Steel casting. Steel casting Production of piece shaped castings

Steel casting is an important stage of steelmaking. The technology and organization of casting often determine the quality of the finished metal and the amount of waste during the further processing of steel ingots. Melted high-quality steel can be spoiled by improperly organized casting.

During casting, the molten steel is released into a pouring ladle and then poured into metal forms - molds or sent to continuous casting machines. As a result of solidification, steel ingots are obtained, which are then subjected to pressure treatment (rolling, forging).

After the melting process is completed, the finished steel is released into a pouring ladle and poured using a crane. From the converter, steel is discharged into a ladle by tilting, and from open-hearth and electric furnaces - through an outlet chute. From the ladle, steel is poured into cast iron molds to produce ingots and into earthen or metal molds to produce shaped castings.

Ladles for pouring steel are most often made with locking mechanisms; steel from such ladles is poured through a hole in a special refractory glass (Fig. 3.1) inserted into the bottom. The production of steel is stopped by a stopper, which is a steel rod protected from the action of metal and slag by fireproof tubes with a special plug fixed at the bottom that closes the hole in the glass. Stoppers and glasses are made from fireclay, graphite and magnesite. The stopper is connected by a fork to a lever mechanism that serves to raise and lower it when opening and closing the hole during casting. The bucket casing is made of sheet steel. It is surrounded around its circumference by a steel ring with trunnions, which serve to grab the overhead casting crane with hooks. The ladle is lined with fireclay bricks. The lining of the ladles is done carefully, with a slight thickness of the seams to avoid destruction by the metal. The durability of the lining is 25-50 heats. Before filling with liquid metal, the ladles are dried and heated to 700-800° C.

The molds into which steel is poured are cast mainly from cast iron and rarely from steel. The dimensions of the molds depend on the weight of the ingot being poured, which ranges from 100 kg to 100 tons or more.

The durability of cast iron molds is 60-100 melts.

The shape and design of the molds depend on the purpose of the ingots cast in them and the method of casting steel (Fig. 3.2, a), as well as on what kind of steel they are intended for casting - boiling, semi-quiet or calm.

Steel is called boiling when, when cast, the metal “boils” in the mold during the period of crystallization of the ingot. It is deoxidized only by ferromanganese. During the deoxidation process, the resulting carbon monoxide, along with other gases dissolved in the steel, is released from the metal, which creates the impression of steel boiling in the molds. Boiling steel is easier to weld than calm steel and can be stamped very well. It produces less waste during rolling. The cost of boiling steel is less than the cost of calm steel. Negative property boiling metal, especially when casting heavy ingots, is a large heterogeneity chemical composition along the height and cross-section of the ingot.

Diagram of a stop-type ladle for steel casting

1 - Glass; 2 - lining; 3 - casing; 4 - lever mechanism; 5 - stopper; 6 - steel ring with trunnions; 7-cork;

Rice. 3.1

Calm steel is one that is well deoxidized before casting; When pouring, few gases are released from it, due to which it calmly solidifies in the molds. It is deoxidized with ferromanganese, ferrosilicon and aluminum. There are bubbles in boiling steel ingots. In quiet steel ingots they are absent, and friability and porosity are observed. Medium-carbon and high-carbon steel are produced only of the calm type, since it is impossible to obtain good ingots from boiling steel with a high carbon content. In addition, mild steel ingots are more homogeneous in chemical composition.

Semi-quiet steel can be called intermediate between calm and boiling steel. To deoxidize this steel, a smaller amount of ferrosilicon is given than for calm steel, and a certain amount of aluminum is added to the ladle before casting the metal or to the molds during casting.

Since a small shrinkage cavity is formed in semi-quiet steel ingots and chemical heterogeneity is less developed, the yield of the usable part of the ingot increases. For casting boiling steel, through-molds of square and rectangular cross-section without a bottom are used, widening downward to make it more convenient to remove ingots from them. To eliminate the formation of cracks in the ingots, the inner surface of the molds is made wavy (Fig. 3.2, a, b).

To obtain quiet steel ingots, molds with a solid bottom and a hole in it to install a fireclay cup for siphon casting or a steel liner for casting from above are used (Fig. 3.2, b).

Ingots intended for rolling sections are cast into molds square section, and for rolling sheets - into molds of rectangular (elliptical) cross-section (Fig. 3.2, a, b).

Ingots used for forging on hammers or presses are cast into molds with a multifaceted cross-section, widening towards the top.

Types of molds for pouring ingots

Rice. 3.2

For rolling, ingots weighing 0.2-25 tons are cast. For forgings, ingots weighing up to 300 tons or more are made. Typically, carbon calm and boiling steels are poured into ingots weighing up to 25 tons. Alloy and high-quality steels are poured into ingots weighing 0.5-7 tons, and some types of high-alloy steels are poured into ingots weighing several kilograms.

According to the shape of the longitudinal section, there are two types of molds:

With widening towards the top;

With widening towards the bottom.

Molds that widen towards the top are made with a bottom and are used for casting mild steel. Molds that widen towards the bottom are made without a bottom (through), during casting they are placed on cast iron trays and used for pouring boiling steel.

Steel casting methods

There are two main methods of casting steel:

Pouring into molds;

Continuous casting.

Casting into molds is divided into two types:

Pouring from above;

Siphon pouring.

Pouring from above

When casting from above, steel from the ladle (Fig. 3.3) directly enters the molds. After filling each mold, the ladle is transported to the next mold and after filling its cycle is repeated.

Scheme of casting steel into molds from above.

a - ladle with liquid steel, b - mold

Rice. 3.3

Large weight ingots (up to 200 tons) are cast on top, as well as some types of alloy steel (high-speed, ball bearing, etc.), in which a minimum content of non-metallic inclusions is permissible.

Siphon pouring

In siphon casting, based on the principle of communicating vessels, several molds (from two to several dozen) are simultaneously filled with steel. Liquid steel from the ladle enters the center mold installed on the pallet, and from it through channels in the pallet into the molds below. After filling all the molds installed on the pallet, the ladle is transported to the next pallet.

Scheme of the siphon method of steel casting:

1 - ladle, 2 - center sprue, 3 - siphon bricks, 4 - pallet, 6 - molds, 6 - slag traps, 7 - refractory mass

Rice. 3.4

Using the siphon method, from ladle 1 (Fig. 3.4) through center sprue 2, depending on the weight of the ingots, from two to 60-100 molds are simultaneously poured. In this case, the metal, passing through the center sprue 2, enters through a system of channels formed by special siphon bricks 3 in a cast iron pan 4, to each mold 5. Advantages of the siphon method: a large number of ingots can be cast in one stream, the surface of the ingots is clean due to the reduction in height and the volume of the shrinkage cavity, you can obtain high-quality ingots weighing up to 20-30 g of steel. The disadvantage of siphon casting is the labor-intensive work of assembling molds for casting and the high consumption of metal on the gates.

Both casting methods are widely used in practice. Each of them has its own advantages and disadvantages. There is still no clear answer to the question of which one is the best. Due to the simplicity and lack of metal loss with sprues, casting from above is often preferred. For ordinary steel grades, top casting is more economical than siphon casting. At the same time, high-quality and alloy steels, when it is important to obtain a clean surface of the ingot to reduce losses of expensive metal during stripping, are cast mainly by siphon.

Continuous casting of steel

The essence of the continuous casting method is that liquid steel is continuously poured into a water-cooled mold without a bottom - a crystallizer, from the lower part of which an ingot with a liquid core, solidified along the periphery, is pulled out. Next, the ingot moves through a secondary cooling zone, where it completely hardens, after which it is cut into blanks of a certain length. Pouring is carried out until the metal in the steel-pouring ladle is consumed. Before casting begins, a temporary bottom, called a seed, is introduced into the crystallizer.

Units for casting steel using this method are called continuous casting machines (CCMs) or continuous steel casting plants (UNRS). There are several types of continuous casting machines, of which the most common are vertical, curved, and horizontal (Fig. 3.5).

Schemes of industrial continuous casters

I - vertical type; II - vertical type with bending of blanks; III - radial type; IV - curved continuous caster; V - curved type with a straight crystallizer; VI - inclined-curvilinear type; VII - horizontal type; L - metallurgical length, R1 - base radius of the continuous caster, R2, R3 - straightening radii of the cast ingot

Rice. 3.5

Depending on the number of simultaneously cast ingots, machines can be single-strand, double-strand or multi-strand. Continuous casting machines cast square (blooms), rectangular (slabs), round and hollow round billets for the production of pipes.

The main advantages of continuous casting of steel over casting into molds are:

In increasing the yield of usable metal (due to the absence of a shrinkage cavity in workpieces obtained through continuous casting);

There is no need to build and operate crimping mills (blooming and slabs);

In reducing the chemical heterogeneity of the metal;

In reducing the cost of manual labor;

In improving working conditions during casting;

The ability to automate the casting process.

The most common method is to cast steel into molds, which are cast iron, less often steel with or without a bottom, expanded upward or downward for more convenient removal of ingots. Before casting, the molds are cleaned, heated and lubricated from the inside to obtain a clean ingot surface. Pouring is done in two ways: from above or from below. When casting from above, steel is poured into each mold separately (Fig. 52, a) directly from the ladle or using funnels, chutes and intermediate ladles. This method is used in cases where it is necessary to obtain a small number of large ingots. Its advantage is that it allows you to cast steel that is not very hot: this results in a healthier ingot with less shrinkage. The surface quality of the ingot is low due to splashes during pouring, but fewer non-metallic inclusions are formed in the ingot.

Bottom casting (siphon) is used in cases where it is necessary to pour steel into a large number of molds (2-6 pieces). The siphon casting diagram is shown in Fig. 52, b.

The steel produced in steelmaking units contains a significant amount of dissolved oxygen in the form of ferrous oxide. It reduces the impact strength of steel, making it red-brittle and cold-brittle. To free steel from oxygen, it is deoxidized with substances called deoxidizers. Aluminum, calcium, silicon, manganese, titanium, which are introduced in the form of ferroalloys, are used as deoxidizers.

Depending on the degree of deoxidation, calm, semi-quiet and boiling steel are distinguished.

Mild steel is made completely deoxidized. An ingot of such steel is highly dense and does not have gas bubbles. The shrinkage cavity is located on the profitable part (Fig. 53, a).

Boiling steel is obtained by partial reduction of ferric oxide with a small consumption of decompressants. During the solidification of the ingot, a reaction occurs in the steel with the release of carbon monoxide, which causes the formation of a large number of gas bubbles in it (Fig. 53, b).

Semi-quiet steel deoxidizes to a lesser extent than calm steel, which leads to the formation of gas bubbles in the ingot (Fig. 53, c). In terms of properties and structure, semi-quiet steel occupies an intermediate position between boiling and calm steel.

Based on the shape of the longitudinal section, ingots with widening upward or downward are distinguished. Boiling steel is poured into molds that are widened at the bottom, and calm steel is poured into molds that are widened at the top, with insulated extensions (Fig. 54). Widening the molds upward and using insulated extensions reduce the distribution of the shrinkage cavity at the height of the ingot. The yield of suitable rolled products from plain steel ingots widened at the top is greater than from ingots widened downward. The ratio of height to average thickness for calm steel ingots is usually in the range of 2.5-3.0, for boiling steel ingots this ratio sometimes reaches more than 4. To obtain high-quality steel, vacuum casting is used. In this method, the liquid metal is subjected to exposure (vacuum) in a closed chamber, from which air and gas are continuously removed. Thanks to this, the metal is obtained with a minimum content of gases and non-metallic inclusions. Evacuation is usually carried out in a ladle before casting steel into molds.

When steel hardens, a crystallization process occurs. If If a cold ingot is cut across or lengthwise, planed, ground and etched, then you can see its structure or, as they say, macrostructure with the naked eye (as opposed to the microstructure, which can be observed under a microscope with magnification). The macrostructure of ingots is very diverse and depends on the composition of the steel, casting temperature, and solidification rate; the latter, in turn, depends on the speed of filling the mold with liquid metal, the temperature and material of the mold, the thickness of its walls and other factors.
The ingots solidify unevenly in the mold, and their structure is heterogeneous (Fig. 55). Small crystals form near the walls of the molds, since cooling occurs faster here. Further away from the walls, cooling slows down and crystals grow more freely. Growth occurs in the direction of heat removal, and as a result, columnar crystals elongated towards the center are obtained, which occupy most of the ingot. In the center, the metal cools even more slowly, and a new zone of crystals forms. New crystallization centers appear in the liquid metal and grow freely. The crystals are larger and oriented randomly.

I CONFIRM:

[Job title]

_______________________________

[Name of company]

_______________________________

_______________________/[FULL NAME.]/

"_____" _______________ 20___

JOB DESCRIPTION

Steel caster of the 5th category

1. General Provisions

1.1. Real job description defines and regulates the powers, functional and job responsibilities, rights and responsibilities of a steel caster of the 5th category [Name of the organization in the genitive case] (hereinafter referred to as the Company).

1.2. A steel caster of the 5th category is appointed to the position and dismissed from the position in the manner established by the current labor legislation by order of the head of the Company.

1.3. A steel caster of the 5th category belongs to the category of workers and reports directly to [name of the position of the immediate supervisor in the dative case] of the Company.

1.4. A steel caster of the 5th category is responsible for:

timely and high-quality performance of tasks as intended;
compliance with performance and labor discipline;
compliance with labor safety measures, maintaining order, following rules fire safety at the area of work assigned to him (workplace).

1.5. A person with secondary vocational education in this specialty and at least 1 year of work experience is appointed to the position of steel caster of the 5th category.

1.6. In practical activities, a steel caster of the 5th category must be guided by:

local acts and organizational and administrative documents of the Company;
internal labor regulations;
rules of labor protection and safety, ensuring industrial sanitation and fire protection;
instructions, orders, decisions and instructions from the immediate supervisor;
this job description.

1.7. A steel caster of the 5th category must know:

fundamentals of ingot crystallization;
internal defects of ingots;
influence of steel casting speed on metal quality.

1.8. During the period of temporary absence of a steel caster of the 5th category, his duties are assigned to [deputy position title].

2. Job responsibilities

A steel caster of the 5th category performs the following labor functions:

2.1. Conducting the casting process and regulating the speed of pouring metal from ladles with a capacity of up to 100 tons.

2.2. Centering the jet, cleaning the cup and washing the steel hole in the ladle with oxygen when pouring steel from ladles with a capacity of 100 tons or more, when casting high-quality alloys and grades of steel, when casting converter steel from ladles with a capacity of 100 tons to 300 tons.

2.3. Preparation of trains supplied to the casting bay for casting converter steel from ladles with a capacity of 300 tons or more.

2.4. Installation of stoppers in steel-pouring and tundish ladles.

2.5. Installation of a steel-pouring ladle on a stand near the furnace, replacement of slag bowls.

2.6. Ensuring the timely supply of steel-pouring compositions and deoxidizers, preparation for the production of melts from ladles and the casting platform.

In case of official necessity, a steel caster of the 5th category may be involved in performing duties overtime, in the manner prescribed by law.

3. Rights

A steel caster of the 5th category has the right:

3.1. Get acquainted with the draft decisions of the enterprise management concerning its activities.

3.2. Submit proposals for improvement of work related to the responsibilities provided for by this job description for management's consideration.

3.3. Inform your immediate supervisor about all shortcomings in the production activities of the enterprise (its structural divisions) identified during the performance of your official duties and make proposals for their elimination.

3.4. Request personally or on behalf of the immediate supervisor from heads of departments of the enterprise and specialists information and documents necessary to perform their job duties.

3.5. Involve specialists from all (individual) structural divisions of the Company in solving the tasks assigned to him (if this is provided for by the regulations on structural divisions, if not, with the permission of the head of the Company).

3.6. Require the management of the enterprise to provide assistance in the performance of their official duties and rights.

4. Responsibility and performance evaluation

4.1. A steel caster of the 5th category bears administrative, disciplinary and material (and in some cases provided for by the legislation of the Russian Federation, criminal) responsibility for:

4.1.1. Failure to carry out or improperly carry out official instructions from the immediate supervisor.

4.1.2. Failure to perform or improper performance of one's job functions and assigned tasks.

4.1.3. Illegal use of granted official powers, as well as their use for personal purposes.

4.1.4. Inaccurate information about the status of the work assigned to him.

4.1.5. Failure to take measures to suppress identified violations of safety regulations, fire safety and other rules that pose a threat to the activities of the enterprise and its employees.

4.1.6. Failure to ensure compliance with labor discipline.

4.2. The assessment of the work of a steel caster of the 5th category is carried out:

4.2.1. By the immediate supervisor - regularly, in the course of the employee’s daily performance of his labor functions.

4.2.2. By the certification commission of the enterprise - periodically, but at least once every two years, based on documented results of work for the evaluation period.

4.3. The main criterion for assessing the work of a steel caster of the 5th category is the quality, completeness and timeliness of his performance of the tasks provided for in these instructions.

5. Working conditions

5.1. The work schedule of a 5th category steel caster is determined in accordance with the internal labor regulations established by the Company.

5.2. Due to production needs, a 5th category steel caster is required to go on business trips (including local ones).

I have read the instructions ___________/___________/ “__” _______ 20__

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Introduction
1. Features of steel casting
2. Steel casting ladles
3. Methods for making steel castings
3.1 Production of piece shaped castings
3.2 Casting steel into molds
3.3 Solidification and structure of a steel ingot in a mold
3.4 Processing of liquid metal outside the steelmaking unit
3.5 Continuous casting of steel
4. Experience in improving the quality of steel at OJSC Magnitogorsk Iron and Steel Works
5. Features and disadvantages of continuous steel casting
Conclusion
List of used literature

Introduction

Metallurgical production arose at the dawn of the development of human society. Metals such as iron, copper, silver, gold, mercury, tin and lead found their use even before our era.

Metals are among the most common materials that humans use to meet their living needs. Nowadays, it is difficult to find a branch of production, scientific and technical activity of a person, or simply his everyday life, where metals would not play a dominant role as a structural material.

Metals are divided into several groups: ferrous, non-ferrous and noble. The group of ferrous metals includes iron and its alloys, manganese and chromium. Gold, silver and platinum are considered noble. All other metals are non-ferrous periodic table D. I. Mendeleev.

Iron and its alloys are the basis modern technology and technology Among structural materials, iron and its alloys are in first place and make up more than 90% of all metals used in modern production.

The most important of the alloys of iron is its alloy with carbon, forming the group of steels and cast irons. Steels are alloys of iron and carbon, the content of which does not exceed 2.14%. Steel is the most important structural material for mechanical engineering, transport and many other sectors of the regional and federal economy. Steelmaking is the second link in the overall production cycle of ferrous metallurgy.

The modern high level of metallurgical production is based on deep theoretical research, major discoveries made in different countries world and rich practical experience.

The development of metallurgy follows the path of further improvement of smelting and casting of metal, mechanization and automation of production, the introduction of new progressive methods of work that ensure improvement of the technical and economic indicators of smelting and the quality of finished products.

1. Features of steel casting

The steel casting process includes the preparation of liquid steel for casting, its transportation from the steel-smelting unit to the casting site and the direct pouring of steel into molds in order to obtain castings of specified parameters according to linear dimensions, shape, weight, mechanical properties and required structure.

The main feature that should be taken into account when casting steel is that it has lower fluidity than cast iron, increased shrinkage - linear 2% and volumetric 6%.

The shrinkage of liquid metal depends on the pouring temperature and is an uncertain quantity. Therefore, it is referred to a certain temperature range (at 1 0 C or 100 0 C) and is usually expressed as a percentage. Solidification shrinkage and solid metal shrinkage (volumetric and linear) are also expressed as a percentage.

The volumetric shrinkage of solid metal is assumed to be 3 times greater than linear shrinkage according to known relationships for the thermal expansion coefficients of bodies.

The shrinkage process makes it extremely difficult to obtain accurate and high-precision castings. One of the difficulties is the formation of shrinkage defects inside the solidifying casting in the form of all kinds of discontinuities (cavities, porosity, cracks). The occurrence of these defects is associated with non-simultaneous solidification of the metal in the casting volume. By giving off heat to the environment (mold material), the casting begins to cool and solidify from the outer surface, while its inner part continues to remain liquid. With further cooling and hardening, the core of the casting undergoes greater relative compression than the previously hardened outer surface. As a result, the continuity of the metal is broken and a vacuum void is formed inside the casting, called a “shrinkage cavity”.

Shaped castings are characterized by the formation of an internal, hidden cavity; in contrast, in ingots, metal shrinkage causes the formation of a funnel-shaped depression, which is called an external or open shrinkage cavity.

The size of the crystallization temperature range also affects the formation and nature of shrinkage defects.

Thus, the shrinkage of steel in the liquid state, during the transition period from the liquid state to solidification and directly during solidification, determines the size of the shrinkage cavity.

The size and shape of the casting influence both the size and location of the shell in the casting. Theoretically, the size of the shell turns out to be proportional to the volume of the casting.

The cooling conditions of the casting affect, first of all, the nature of the resulting shrinkage voids. The more intensively the casting is cooled, the less dendritic crystallization develops in it.

In connection with the above, it follows:

1. In order to prevent defects due to shrinkage cavities, it is necessary, if possible, to ensure the direction of solidification of the casting towards the locations of its most massive parts.

2. In order to prevent defects due to sand holes and other defects, it is necessary to place the main surfaces to be processed, as well as developed surfaces of the casting, primarily from below the pouring, and in the absence of such a possibility, vertically or obliquely.

3. In order to reduce defects due to underfilling, thinner walls of the casting should be located in the lower parts of the mold and, if possible, in a vertical or inclined position.

To eliminate the possibility of the formation of shrinkage cavities in assemblies and massive parts of the casting, during the design and manufacture of the mold, the installation of profits is provided, which also serve as collectors of floating non-metallic inclusions or possible other discharges.

The profit weight for steel parts is 30 - 50% of the casting weight.

1. Shrinkage cavities are formed in the casting areas that are the last to cool, these include all the most massive parts, local thickenings, joints individual elements parts, as well as places where heat transfer is difficult.

2. The shrinkage cavity tends to occupy the highest position in the casting.

3. Open profits are installed on the upper parts of the casting, closed ones - on the massive parts of the casting located inside the mold.

4. Placing profits on massive parts of the casting slows down the cooling rate of the latter, contributing to an increase in residual stresses in it.

5. Placement of gains in places where tensile stresses are concentrated in the casting when high temperature, promotes the formation of hot cracks in these places during the solidification of the casting.

6. Putting profits on unprocessed parts of the casting leads to an increase in the cost of processing it.

7. To cool local components and mainly thickened areas of the casting, if the latter are not provided with power from the profit, refrigerators - metal inserts - are installed during the manufacture of the mold.

2. Steel casting ladles

Liquid steel produced in a steelmaking unit (arc furnace, open hearth, converter, induction furnace, etc.) must be transported to the casting site. A special steel-pouring ladle is used for this purpose. Its purpose is to receive molten steel, move the resulting volume of steel from the steel-smelting unit to the casting site, short-term storage and pouring of steel into the feeders of casting molds.

Depending on the method of transportation of buckets and their purpose in the technological process, they are divided into crane and monorail. Crane buckets, in turn, are divided into:

1. Conical, with a capacity from 1 to 70 tons.

2. Locking, with a capacity of 1 to 70 tons.

3. Drum, with a capacity from 1 to 5 tons.

Monorail buckets are classified into;

1. Conical, with a capacity from 100 to 400 kg.

2. Conical with a turning mechanism, capacity from 500 to 800 kg.

3. Teapots, with a capacity from 100 to 250 kg.

4. Drum, capacity from 400 to 800 kg.

The design of a teapot ladle is shown schematically in Fig. 1.

The outer body of the bucket is made of steel. Two axles, located diametrically opposite and slightly above the center of gravity of the bucket, are rigidly fixed to the outer surface of the body. Trunnions are necessary to support the bucket on the seats of a monorail trolley or crane suspension. The method of fixing the bucket is determined by its load capacity and method of transportation.

The internal cavity of the ladle is lined with a heat-resistant lining, which ensures the durability of the ladle, eliminates burnout of the outer casing by liquid metal and plays the role of a thermal insulator that maintains the temperature of the liquid steel in the ladle.

Pouring liquid steel from a ladle is carried out by rotating it on axles at a certain angle. The trajectory of the outflow of metal is parabolic and with a change in the angle of inclination of the ladle, the shape of the parabola and the intensity of the stream of flowing metal change.

In Fig. Figure 2 shows the schematic design of a stopper ladle, the device of which allows liquid metal to be dispensed through a nozzle located in the bottom of the ladle and closed with a stopper. The operation of the stopper is controlled by a special lever mechanism mounted on the outer surface of the housing.

Otherwise, the design and structure of the bucket is similar to the bucket shown in Fig. 1.

The advantages of the ladle in question over the previous one are that, firstly, there is no need to rotate the ladle, and secondly, the flow of flowing metal is straight and directed vertically downwards.

The development of steel casting processes led to the creation and use of drum-type ladles, the schematic design of which is shown in Fig. 3.

The bucket is a cylinder 2 with a horizontal axis of rotation; The ends of the cylinder are rigidly and hermetically sealed with lids, on the outer surface of which axles 1 are strictly coaxially installed. To pour liquid metal into the ladle and release this metal from the ladle, a window 3 is located on the side surface of the cylinder.

The bucket body and axle are made of steel, and its inner surface lined with fire-resistant lining material.

The design of this bucket has a number of advantages over the previous ones:

1. Allows use in mechanized devices for transporting, filling and dispensing liquid steel.

2. Rigid fixation of the bucket during transportation.

3. Better thermal insulation ladle, thereby increasing the time for collecting liquid steel.

4. Possibility of rotating the bucket 180 0 .

Buckets in terms of their design, metal content and method of transporting liquid steel are selected depending on the requirements of the technological process, the method of obtaining finished foundry products and the degree of mechanization of production processes.

3. Methods for making steel castings

Liquid steel can be used:

To produce shaped piece castings of any size and weight, both in single, large-scale and mass production

For pouring into molds for the purpose of further processing, an ingot is obtained by pressure (rolling, forging) and, as the final stage of this process, the production of long products.

For continuous casting on special equipment in order to obtain long products, bypassing the stage of obtaining an ingot, its cooling, additional heating and subsequent pressure treatment.

3.1 Production of piece shaped castings

These castings are blanks for parts of any engineering industry. Approximately 23% of the total assortment produced by the steel industry consists of shaped castings with a yield of usable metal of slightly more than 60%. To produce steel shaped castings from carbon steel, mainly foundry steel grades 15L, 20L, 25L, 30L, 35L, 40L, 45L, 50L and 55L are used. Within the same group of complexity and mass, castings can be produced in different ways.

The main methods for making castings include:

A. Conventional casting method: ? casting into one-time wet and dry sand molds, regardless of the molding method.

B. Special casting methods:

In metal molds (chills),

Shell mold casting,

Lost wax casting,

Centrifugal casting.

The casting manufacturing method is selected taking into account the subsequent machining finished casting, based on comparative technical and economic analysis.

The simplest method, known since ancient times, is to make a mold in the ground (on the parade ground). An open mold in soil is used for single (individual) production. More critical castings and with increased weight characteristics are obtained by molding in various ways: the lower part of the casting is in soil, the upper part is in a flask. In this case, liquid metal is poured through a feeder.

Castings can be obtained by molding a model in two flasks, both equal in height and of different heights. The forming process is carried out manually, and the liquid steel is poured through a feeder and gating system. In the form, if necessary, profits can be located.

In machine molding, molds are made, with rare exceptions, in two flasks (Fig. 4 and Fig. 5). This method is used in serial and mass production. When using the forms presented in Fig. 4. Liquid steel is poured into a raw mold, and when using the molds shown in Fig. 5, liquid steel is poured into a dry mold or a mold with surface drying.

The weight groups of castings for this casting method are not limited.

In addition to the usual methods of producing steel castings by casting into one-time sand molds, special casting methods are quite widespread.

Casting in metal molds (moulds), These molds are reusable, made of steel or cast iron. Forms with horizontal, vertical and combined parting planes are used. A cavity configuration of the casting and gating system is made along the parting plane. Sand rods are used to obtain internal cavities in the casting.

Liquid steel is poured into the mold through a feeder; after solidification, the castings are knocked out.

Chill casting is used to produce steel castings, and the range of castings is very diverse.

Shell casting is used primarily to reduce the large amount of mechanical processing of the casting and to produce castings of 4...6 accuracy grades, and also when the method of producing castings using lost wax models is not economically justified.

Pouring liquid steel is most often carried out using a siphon method.

Shell casting is used in serial and mass production.

Lost wax casting is used to reduce or even eliminate large amounts of machining, primarily when cast steel is difficult to cut.

Used in serial and mass production.

Centrifugal casting is mainly used to ensure high density casting material and elimination of center rods.

Steel castings are produced by centrifugal casting using special machines with a horizontal, vertical or inclined axis of rotation of the casting.

Steel is poured into a rotating mold using a special open tray directly from the ladle. Rods are not needed to obtain the internal cavity of the casting.

Analyzing the methods for producing castings, we can say that pouring liquid steel into molds in single or small-scale production is carried out without the use of automation equipment directly from the ladle to the mold feeder.

In conditions of serial and mass production, the method of pouring liquid steel into one-time, mostly raw sand molds is used, manufactured in two equally high flasks by machine molding with an additional pressing pressure of 20 - 30 MPa. This method of obtaining molds is a prerequisite for creating a mechanized or automated section for filling molds with liquid steel, since such molds in flasks allow them to be transported.

Accelerating the rate of production of molds in a flow (12 sec. or less) in conditions of mass and large-scale production makes it necessary to automatically fill liquid steel. Industry (both domestic and foreign) produces installations for automatic casting of liquid steel - these are installations using a magnetic pump, a dosing pouring ladle with induction heating, an intermediate stop drum ladle with dosing of a mass of metal, etc. For mechanized or automated casting of liquid steel, electrified ones are used trolleys of type TML - 100 and TML - 200, produced by domestic industry. These carts are equipped with an operator’s cabin and at the same time have the ability to remotely control the movement and manipulation of the bucket (raising, lowering, turning, etc.). The trolley moves along a monorail track.

When using the method of pouring liquid steel directly from a ladle into a mold, it is necessary to observe the time for selecting liquid carbon steel from the ladle, which is recommended for the given materials:

Bucket capacity, t 4 6 - 8 16

Selection time, min 12 17 23

3.2 Casting steel into molds

Pouring liquid steel into molds is used to produce steel blanks of significant dimensions and weight, for their further processing by pressure (after cooling and subsequent additional heating) in order to obtain long products or large forgings. Pouring liquid steel into molds is carried out from a ladle. Casting molds (molds) are accepted depending on the intended finished product: for long and shaped rolled products.

Molds are cast iron molds for producing ingots of various sections. Based on their design, molds are divided into solid-bottom and through-bottom, and based on the method of metal pouring - into top-filled and bottom-filled (siphon casting). Vertical cast iron molds are used for casting steel. Molds for ingots intended for forgings can hold up to 100 tons of steel or more; molds for steel going into rolling are designed for ingots weighing from 100 kg to 20 tons (ingots for slabs). In order to reduce shrinkage cavities in ingots, I. are manufactured with an insulated extension.

The method of casting steel into a mold and the state of the metal during the casting and solidification process significantly affect the properties of steel. Basically, there are two types of casting: boiling and calm steel.

There are two methods of casting steel into molds: from above directly into the mold and by siphon

Rice. 6 Scheme of molds: a-from the top pouring; b-with siphon filling

When casting from above (Fig. 6), steel is poured from ladle 2 into each mold 1 sequentially.

With this method of steel casting, the surface of the ingots, due to splashes of liquid metal on the walls of the mold, may be contaminated with oxide films.

When siphon filling (Fig. 6, b) steel is simultaneously filled from 2 to 6 molds installed on a pallet through the center sprue 3 and channels in the pallet. In this case, the steel enters the molds from below, which ensures smooth filling without splashing, the surface of the ingot is clean, and the casting time is reduced. The steel in extension 4 is kept in a liquid state, thereby reducing sinkage and ingot waste during cutting.

Top casting is usually used for carbon steels, and siphon casting is usually used for alloy steels.

3.3 Solidification and structure of a steel ingot in a mold

The process of solidification of a steel ingot and the formation of a crystalline structure in it was discussed above. It should be added that the structure of the ingot is determined not only by the cooling conditions, but also by the degree of deoxidation. On this basis, steels are divided into boiling, calm and semi-calm. Schemes of the structure of ingots are presented in Fig. 7.

Fig.7. Schematic representation of steel ingots:

a - boiling, b - calm, c - semi-calm

Boiling steel? steel that has not been completely deoxidized in the furnace. Its deoxidation continues in the mold due to the interaction of iron oxide FeO with carbon. The resulting carbon monoxide CO is released from the steel and it does not contain non-metallic impurities, while possessing high ductility.

Boiling steel is deoxidized so that it emits gas both during the filling of the mold and after the filling process is completed. As a result of the reaction of carbon with oxygen at the solidification front, carbon monoxide is formed. In this case, a clean surface layer (dense crust) and a core enriched with impurities (liquation zone) are formed. Intensive gas release until complete solidification prevents a concentrated decrease in volume in the middle of the upper (head) part of the ingot. The decrease in volume (shrinkage cavity) is caused by the unequal specific volume of steel in liquid and solid states of aggregation. In boiling steel, the shell is distributed in the form of gas bubbles (pores) throughout the entire volume of the ingot. During the subsequent hot pressure treatment, the gas bubbles are sealed, as they are almost uncontaminated. This has a positive effect on the yield. Another advantage is the clean surface area, which meets high demands on surface quality. The disadvantage is the enrichment of impurity elements (liquation): carbon, phosphorus, sulfur, nitrogen and oxygen in the axial zone, especially in the upper part of the ingot. This leads to uneven properties of the material along the height of the ingot and across its cross section. Another disadvantage is the increased tendency to brittle fracture, since nitrogen cannot be bound.

Calm steel is obtained by complete deoxidation of the metal in the furnace and ladle (Fig. 7, b). Such steel hardens without the release of gases, a dense structure is formed in the ingot, and the shrinkage cavity is concentrated in the upper part of the ingot, which increases the yield of usable metal. Calm steel eliminates the above disadvantages inherent in boiling steel. When casting calm steel, a significant reduction in the content of oxygen and elements with an affinity for oxygen, which are listed above, is ensured. Since the elements aluminum, titanium, vanadium and zirconium simultaneously have a high affinity for nitrogen, this simultaneously reduces the tendency to brittle fracture of steel. The quality of steel can be adversely affected by oxides formed during the binding of oxygen, which, if it is not possible to remove them from the melt, turn into non-metallic inclusions and, in sufficient concentration, can limit the use of the material due to the formation of discontinuities in it. Since, as a result of erosion of the refractory material, additional (exogenous) non-metallic inclusions enter the steel, special attention should be paid to reducing their content by separation. When blowing liquid steel with argon, a reduction in the content of non-metallic inclusions in it is achieved. The remaining non-metallic inclusions are released during the solidification process, especially in the subsurface zone, which can adversely affect the quality of the surface. However, along the entire length of the ingot and especially in its upper part (where the shrinkage cavity ends), enrichment with non-metallic inclusions is possible. Another disadvantage of quiet steels is a concentrated decrease in volume in the upper part of the ingot, which reduces the yield. When using molds equipped with heat-insulating extensions in the upper part, this reduction in yield can be compensated to a certain extent.

Semi-quiet steel is obtained by deoxidation with ferromanganese and an insufficient amount of ferrosilicon or aluminum and by targeted regulation of the oxygen content. The result is semi-quiet or mechanically plugged steel. These measures make it possible to achieve a better surface quality than that of calm steel, and a more uniform distribution of liquidating elements than in boiling steel, and the ingot itself does not have a concentrated shrinkage cavity; in the lower part it usually has the structure of calm steel, and in the upper part - of boiling steel (Fig. 7, c). In terms of quality, such steel is applicable only for some specific purposes, and in terms of cost it is intermediate between boiling and calm.

3.4 Processing of liquid metal outside the steelmaking unit

During out-of-furnace processing, metal smelted in a conventional steel-smelting unit (open hearth furnace, converter or electric furnace) is exposed to external influences in a steel-pouring ladle. The main purpose of the out-of-furnace processing of liquid steel in a ladle is to reduce the content of gases, non-metallic inclusions and sulfur dissolved in the metal.

Currently, there is no method of processing liquid steel in a ladle that would simultaneously significantly reduce the content of non-metallic inclusions, sulfur and gases in the metal. Therefore, depending on the task at hand, one or another method of out-of-furnace metal processing is used.

Processing metals in a ladle with synthetic slag leads to a decrease in the amount of sulfur, non-metallic inclusions and oxygen in the steel. The essence of the method is that the metal is released from the furnace into a ladle partially filled with liquid slag (4 - 5% of the metal mass), which is previously smelted in a special unit. Liquid slag and metal are intensively mixed. Sulfur, oxygen and non-metallic inclusions pass from the metal into the slag. When processing metal with synthetic slag, its composition and physicochemical properties play an important role. The slag must have a low melting point and viscosity, as well as high basicity and low oxidation. These requirements are met by lime-alumina slags containing 50 - 55% CaO, 38 - 42% Al 2 O 3, 1.5 - 4% SiO 2, 0.15 - 0.5% FeO. Slags of this composition have a high refining ability.

Improving the quality of steel processed with synthetic slag compensates for the costs associated with smelting such slag.

Blowing metal in a ladle with powdered materials is one of the modern methods improving the quality of steel and the productivity of steelmaking units.

Electroslag remelting (ESR) consists of the following:

The remelted steel is supplied to the installation in the form of a consumable (remelted) electrode 1 (Fig. 8). Molten slag 2 (a mixture of 60...65% CaF2, 25...30% Al2O3, CaO and other additives) has high electrical resistance and when passing electric current it generates heat sufficient to melt the electrode. Drops of metal pass through a layer of slag, collect in a bath and solidify in a water-cooled mold, forming an ingot. In this case, crystallization of the metal occurs sequentially and is directed from bottom to top, which contributes to the removal of non-metallic inclusions and gas bubbles and thereby the formation of a dense and homogeneous structure of the ingot. At the end of the remelting, the pan is lowered and the solidified ingot is removed from the mold.

Modern ESR installations make it possible to produce ingots of various sections weighing 40 tons.

Fig.8. ESR installation diagram: 1-electrode, 2-flattened slag, 3-bath, 4-mold, 5-obtained ingot, 6-pallet

Liquid metal in a flow of inert gas (argon) through a tuyere is introduced into crushed desulfurizers and deoxidizers. As a result of such processing, it is possible to obtain a metal with a sulfur and oxygen content of less than 0.005% each.

Treatment of liquid steel with argon in a ladle is the most in a simple way improving metal quality. Argon is blown into liquid steel through porous and fireproof plugs, which are installed in the bottom of the ladle. Argon does not dissolve in liquid steel, therefore, when blowing metal with argon, a large number of bubbles are formed in the volume of liquid steel, which intensively mix the metal and bring non-metallic inclusions to its surface. In addition, hydrogen and nitrogen dissolved in steel pass into argon bubbles and leave the liquid metal with it, i.e. degassing of the steel occurs.

The simplest method is to vacuum the steel in a ladle. In this case, a ladle with liquid metal is placed in a sealed chamber, from which the air is pumped out. When the pressure in the chamber decreases, the metal boils due to the rapid release of gases from the metals. After degassing the metal, the chamber is depressurized, and the evacuated ladle is sent for casting.

Bucket evacuation is ineffective when processing completely deoxidized steel and large masses of metal. In this case, due to the weak development of the reaction 2C + O 2 = 2CO, the metal boils sluggishly. To improve the degassing of steel, vacuum processing of metals in a ladle is combined with purging it with argon and electromagnetic stirring. Typically, degassing of the metal in the ladle is carried out for 10 - 15 minutes. Longer processing leads to a significant decrease in metal temperature.

Partial and circulation evacuation of steel is used for degassing large masses of metal.

In batch evacuation, a lined vacuum chamber of small volume is placed above a ladle with liquid metal. The chamber pipe, lined inside and out, is immersed in liquid metal. Under the influence atmospheric pressure a portion of metal (10 - 15% of the total mass) rises into the chamber and is degassed. When the ladle moves down or the chamber moves up, the metal flows out, and when it moves back, it rises into the chamber again; to completely degas the steel, it is necessary to carry out 30 to 60 cycles of vacuum treatment.

In the circulation method of evacuation of steel, a vacuum chamber with two pipes is used. Liquid metal from the ladle rises into the chamber through one pipe, degasses and flows back into the ladle through the second pipe. There is a continuous circulation of metal through the vacuum chamber. The rise of liquid steel into the chamber occurs due to the action of argon, which is supplied to the inlet pipe.

Jet evacuation of metal is used mainly when casting large ingots. This method is more advanced, since it eliminates secondary oxidation when pouring evacuated metal from a ladle into molds.

When casting ingots in a vacuum, a stream of metal poured from a ladle into a mold installed in a vacuum chamber is broken by the released gases into many small drops of metal. The surface of the metal increases sharply, which leads to deep degassing of the steel. In addition, the steel is also degassed into the molds.

Recently, to obtain steel with a very low carbon content, processing the metal in a vacuum is combined with blowing it with oxygen or a mixture of argon and oxygen.

Steel refined with synthetic slag has a low content of oxygen, sulfur and non-metallic inclusions, which provides it with high ductility and toughness.

3.5 Continuous casting of steel

Continuous casting of steel is the process of obtaining ingots from liquid steel - billets (for further rolling, forging or pressing), formed continuously as liquid metal enters from one side of the mold - crystallizer and the partially solidified billet is removed from the opposite side. It should be noted that only soft steel is subjected to the continuous casting process, since, due to the high drawing speed, it is not possible to obtain a satisfactory surface quality.

Continuous casting of steel has the following advantages over conventional casting: metal consumption per 1 ton of suitable rolled stock is reduced by 10 ... 15% due to reduced cutting of the head and bottom parts of the billet, capital costs for the manufacture of a fleet of cast iron molds are reduced, which are completely eliminated in this process, there are no sections for preparing molds and extracting ingots from them, there is a complete absence of expensive blooming and slabging, in which large ingots are pressed into a billet for subsequent rolling; conditions are created for complete mechanization and automation of the casting process; Due to the acceleration of solidification, the degree of homogeneity of the metal increases and its quality improves.

Continuous casting of steel is carried out in special installations - UNRS (Fig. 9).

Liquid steel from ladle 6 through an intermediate device 5 is continuously poured from above into a water-cooled mold without a bottom - a crystallizer? 4, and from its lower part a hardening ingot is pulled out at a certain speed (which ranges from 1...2.5 m/min) using rollers 3. The mold 4 has an internal cavity, the profile of which corresponds to the cross section of the casting. The working part of the crystallizer in contact with the metal is made of copper, hard aluminum alloys, steel or graphite. The crystallizer body is intensively cooled by water circulating through the channels available in it.

Steel castings are poured into long molds (1000 ... 1500 mm). To obtain castings with internal cavities, a rod of the appropriate cross-section is installed in the mold.

At the beginning of the process, a temporary bottom is introduced into the crystallizer - the so-called seed, connected to an individual drive and having a profile corresponding to the cross-sectional profile of the resulting casting. The metal solidifies at the walls of the crystallizer and at the seed, which clears the way for the shell of the workpiece to be removed from the crystallizer and which begins to be removed from the crystallizer at a constant, predetermined speed. From above, liquid metal is continuously fed into the crystallizer in such a quantity that its level remains constant throughout the entire casting process. To reduce the pulling force, the crystallizer is given a reciprocating movement along its longitudinal axis, and lubricant is supplied to its walls. The surface of the liquid metal is protected from oxidation by a layer of synthetic slag or a protective atmosphere created by an inert gas. At the exit from the crystallizer, the workpiece with a liquid core enters the secondary cooling zone, where sprayed water is supplied to its outer surface from nozzles. It finally solidifies and enters the cutting zone, where it is cut by a gas cutter 2 into ingots of the required length. The resulting ingots are lowered onto a roller conveyor using tilter 1 and fed to rolling mills.

The described continuous casting method is called Junghans casting.

At UNRS, square billets with dimensions from 50x50 to 300x300 mm, flat slabs with a thickness of 50 to 300 mm and a width of 300 to 2000 mm, round billets (solid and with an internal cavity) with a diameter of 100 to 550 mm, from which pipes are produced, are cast. long and sheet products, forgings. Large degree chemical homogeneity along the length and cross-section of continuously cast billets ensures stable mechanical properties and increases the reliability of metal products. Due to its advantages, continuous casting of steel has been adopted as the main casting method in all newly constructed steelmaking shops and will be widely used in the reconstruction of existing plants. The highest productivity of UNRS is ensured when they operate in combination with oxygen converters. In this case, equality of cycles for steel production from the converter and its casting at the UNRS is achieved, thanks to which liquid metal can be supplied to the installation continuously for a long time. In workshops with modern arc furnaces, in which the melting duration is maintained quite accurately, casting can also be organized using the so-called “melt-to-melt” method (one installation continuously receives metal from several furnaces).

Due to continuous feeding and directional solidification, there are no shrinkage cavities in the ingots produced at UNRS. Therefore, the yield of suitable billets can reach 96...98% of the mass of the cast steel, the surface of the resulting ingots is of good quality, and the metal of the ingot is dense and homogeneous

To reduce capital investments and to create the most appropriate combination of continuous casting with rolling, a radial installation for continuous casting of steel was created. This installation is 2 - 3 times lower than vertical ones (the height of which can exceed 40 m) and is correspondingly cheaper. These installations are divided into two types: radial carbon steel without deformation of the workpiece until complete solidification and with deformation of the workpiece until the end of solidification.

General form radial CNC without deformation of the workpiece until complete solidification is shown in Figure 10.

Rice. 10 General view of a radial continuous casting plant:

1- main pouring ladle; 2 - tundish; 3- crystallizer; 4 - mechanism of reciprocating movement of the crystallizer; 5 - secondary cooling; 6 - pulling mechanism.

Steel casting is carried out from a teapot-type ladle, which has a partition to retain slag while the metal is drained. Before casting, the ladle with metal is installed on the cradle of the turning mechanism with a drive. From the bucket, the metal is poured through the toe into an intermediate container mounted on a bracket attached to the frame of the bucket turning cradle. A zircon dispenser is installed in the intermediate container above the crystallizer. The intermediate container has a fixed chute for draining metal in case of overfilling of the ladle and a rotating chute for draining the first contaminated and cooled portions of metal. Another rotary chute is fixed under the intermediate container, which serves to interrupt the flow of metal entering the mold. Before casting, the lining of the main ladle and intermediate tank is heated to 900-1150°C.

Conveyor casting is continuous casting between conveyors moving in one direction (Figure 11). Liquid metal 1 is poured between two rows of plates (moulds) connected into conveyors 2 . The grooves in the molds form a channel covered by a seed. As the conveyors move, the metal crystallized on the walls of the molds is produced in the form of a square, round or other profile.

Rice. 11 Scheme of conveyor casting

Also, in metallurgical shops with modern arc furnaces, in which the duration of smelting is maintained quite accurately, the “smelting for smelting” method is used. One installation continuously receives metal from several furnaces.

The horizontal casting method is shown in Figure 12.

Rice. 12 Horizontal casting method

Liquid metal is fed from a ladle or from a holding furnace 1 into a crystallizer 2, under the influence of the water-cooled walls of which cooling begins. The hardened part of the casting 3 is pulled out by pulling rollers 4 and periodically cut with saws or cutters 5 into pieces of the required length.

This method of continuous casting of steel has advantages over other methods: there is no secondary oxidation when pouring metal from the metal receptacle into the mold; this advantage allows the casting of high-alloy steels with higher quality; absence of deformation of the ingot, which makes it possible to cast crack-sensitive steels that cannot withstand bending, characteristic, for example, of radial machines. You can also note the flexibility of the design, which makes it possible to change the technological length of the machine, the number and location of secondary cooling devices at low cost, which is especially important, it is the ability to quickly switch to casting of a different section.

A progressive method of producing steel blanks by continuous casting requires constant improvement and implementation scientific achievements into production, which leads to an increase in product output while simultaneously improving quality.

4. Experience in improving the quality of steel at OJSC Magnitogorsk Iron and Steel Works

As an example, we consider a project for the reconstruction of the metallurgical production of OJSC Magnitogorsk Iron and Steel Works without stopping the existing production.

To ensure the necessary requirements for metal quality, a steel finishing unit (STA) and a ladle-furnace unit (AKP) were installed. Metal smelting is carried out in two double-bath steelmaking units (DSAs), the capacity of which is reduced from 285 to 175 tons to maintain optimal casting time. For the production of long products, the following technological scheme is used: DSA > AKP or ADS > CCM.

Steel casting on long continuous casters is carried out using an open jet. High oxygen saturation of the metal smelted in DSA and additional gas saturation of the metal due to secondary oxidation during casting affect the quality of long products and lead to the appearance of surface defects due to a violation of the continuity of the metal caused by the formation of subcrustal gas bubbles. To improve the quality of the metal, a set of works was carried out aimed at reducing the oxidation of the metal both in the DSA and in after-furnace processing units.

Rice. 13. Dependence of metal oxidation in the furnace on the carbon content at the outlet: 1 - without the use of aluminum flux; 2 -- using aluminum flux (3.8 - 4.9 kg/t).

The use of a calculated amount of silicon carbide containing ~ 80% Si and 4% C and carbon-containing material UM-5 containing 70% C and 14% SiC for preliminary deoxidation of the metal in a furnace allows reducing the oxidation of the metal by 75-100 ppm.

The issues of reducing the oxidation of the metal in the furnace were also studied by changing the carbon content in the metal at the outlet and when feeding different amounts of aluminum flux containing 4 - 7% metallic aluminum into the furnace before release.

Rice. 14. Dependence of metal oxidation on the amount of added aluminum flux at a constant carbon content at the outlet.

The indicators of metal oxidation upon arrival at the automatic transmission and fumes of deoxidizers used at the outlet during the smelting of StZsp steel. Change in the oxidation of steel in the ladle upon arrival of the melt at automatic transmission on the carbon content in the metal before releasing the melt from the furnace is shown in Fig. 13, and the change in metal oxidation depending on the amount of aluminum flux added to the furnace is shown in Fig. 14.

By increasing the carbon content in the metal before release and during preliminary deoxidation in the furnace, a decrease in the oxidation of the metal is achieved, and, as a result, the absorption of ferroalloys used for deoxidation increases. According to the developed technology, the carbon content at the outlet must be at least 0.03%, and the metal must first be deoxidized in a furnace with aluminum flux (up to 7.0 kg/t) or an appropriate amount of carbon-containing material UM-5 or silicon carbide.

Reducing metal oxidation in automatic transmission. To study the possibility of deeper deoxidation of the metal and reducing the contamination of the ingot by an internal gas bubble, experimental melts using flux-cored wire containing silicocalcium were carried out on the AKP. Analysis of experimental melts with silicocalcium allowed us to conclude that the use of this material leads to a decrease in the oxidation of the metal due to its deeper deoxidation, resulting in a decrease in the score of the internal gas bubble with an increase in the total consumption of silicocalcium (Fig. 15).

Rice. 15. Dependence of the internal gas bubble on the consumption of silicocalcium

Rice. 16. Dependence of the reduction in FeO content in slags on automatic transmission on the consumption of silicon carbide

Rice. 17. Dependence of the degree of reduction in metal oxidation on silicon carbide consumption

To reduce the oxygen content in the metal and slag due to diffusion deoxidation of the metal, experimental melts of StZsp steel were carried out using silicon carbide to deoxidize the slag. When the silicon carbide consumption increases to 1 kg/t, a proportional decrease in the FeO content in the slag (Fig. 16) and metal oxidation (Fig. 17) occurs.

A decrease in metal oxidation in the furnace led not only to a decrease in oxidation upon arrival at the out-of-furnace processing units, but also to a decrease in the loss of silicon and manganese by an average of 8%. By reducing the oxygen content in steel, an improvement in the quality of the metal was noted: a decrease in edge point contamination by 12%, gas bubbles - internal by 70%, surface by 21%.

5. Features and disadvantages of continuous steel casting

With continuous casting in a mold of limited length, castings or cast blanks of unlimited length are obtained. In the cavity of the crystallizer, in its various parts, cooling of the melt, solidification and cooling of the casting simultaneously occurs, and all its parts successively pass through the same zones of the crystallizer and, therefore, are formed under the same conditions.

A high temperature gradient across the cross section of the casting located inside the mold and constant replenishment of the melt in the mold cavity create the prerequisites for directed solidification and continuous feeding of the casting, so the castings are dense

The type of casting under consideration is characterized by:

High yield of usable metal due to reduced trim and the absence of a gating system

By excluding from the technological process such an energy-intensive operation as ingot compression;

Accuracy and surface cleanliness of castings;

A high degree of chemical homogeneity along the length and cross-section of continuously cast billets;

Provides stable mechanical properties of cast workpieces, which in turn leads to increased reliability of metal products;

Reduced energy costs;

Low specific consumption for the manufacture of molds;

Complete exclusion from the technological process of manufacturing castings of the operations of knocking castings out of molds, trimming and cleaning castings;

Reducing the cycle of production operations from steel smelting to obtaining finished rolled products;

Improving working conditions;

Improving the environmental situation by reducing environmental pollution due to the exclusion of molding, manufacturing of rods and the use of rod mixtures from the technological process.

The method of continuous casting of steel produces billets of constant cross-section in the form of a square with dimensions from 50 x 50 to 300 x 300 mm, slabs with a thickness of 50 to 300 mm and a width of 300 to 2000 mm, polyhedrons, angles, round cross-section blanks (solid and with internal cavity) with a diameter of 100 to 550 mm, from which round bars and pipes, strips, long and sheet products and forgings are then produced.

The disadvantages of the continuous steel casting method are:

Impossibility of manufacturing castings of complex configuration;

Limited range of castings and blanks;

Small volumes of casting steel of various grades increase their cost;

Impossibility of casting steel of some grades, for example, boiling steel;

Unexpected equipment breakdowns that cause equipment to stop have a significant impact on overall productivity.

Conclusion

The steel casting process is quite complex, since it involves a number of interrelated processes; obtaining high-quality metal to obtain high-quality final products; reduction of metal losses due to imperfections in the technological process; reduction of energy costs for metal production and reduction of capital investments when reconstructing or expanding steel production.

At the same time, it should be taken into account that the process of pouring liquid steel is very labor-intensive and requires significant physical labor expenditures of service personnel, in particular pourers.

The above provisions pose challenges for engineers and scientists to solve every day in terms of improving the technological process of casting liquid steel and preparing it for casting; maximum possible automation of these processes, improvement of equipment.

The use of the technological process of continuous casting of steel and equipment on which this technological process carried out, allow for significant progress on the path of technological progress.

List of used literature

1. Nebogatov Yu.E. and Tamarovsky V.I. Special types of casting. M.: “Mechanical Engineering”, 1975.

2. Bigeev A.M. Steel metallurgy. M.: Metallurgy, 1987.

3. Mikhailov A.M. Foundry. M.: “Mechanical Engineering”, 1987. .

4. Boychenko M.S., Rutes V.S., Fulmakht V.V., Continuous casting of steel, M., 1961.

5. Nikolaev O. A., Sarychev A. V., Ivin Yu. A. et al. Technology of steel smelting in a two-bath unit and methods of its preparation for casting on long-form continuous casters. ISSN 0038 - 920Х "Steel". No. 3. 2006

6. Schwartzmeier V., Continuous casting, trans. from German, M., 1962;

7. Hermann E., Continuous casting, trans. from German, M., 1961; The theory of continuous casting. Technological foundations, M., 1971.

Steel casting. Steel casting Production of piece shaped castings

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