CN201008961Y - A casting device for super-large cast steel support rolls of composite material over 100 tons - Google Patents

Abstract

The utility model relates to a casting device for super-large cast steel support rolls of composite material above 100 tons. It is suitable for the overall casting process of cast steel backup rolls of various types and specifications with a net weight of more than 100 tons of composite materials. The whole mold casting device is adopted, which has a base, a lower roll neck box, a roll body iron mold, an upper roll neck box, a riser box and a pouring system from bottom to top. The box and the riser box are segmented structures. An overflow tank is set on the upper roll neck box, a steel drum is set outside the mold, and an electric heating riser is installed inside the riser box. The utility model mainly adopts molten steel of different materials for pouring, and adopts the combination technology of down-casting flushing and up-casting and runner heat preservation technology, which ensures the product quality of the integral casting of super-large composite cast steel support roller. The utility model can effectively solve the problems of cracks, shrinkage cavities and porosity of large-scale cast steel support rolls, and makes the localization of super-large cast steel support rolls possible.

Description

A casting device for super-large cast steel support rolls of composite material over 100 tons

technical field

The utility model relates to the casting process of an ultra-large composite cast steel support roll of more than 100 tons (the support roll with a net weight of more than 100 tons is a super-large support roll), in particular to a super-large cast steel support roll of a composite material of more than 100 tons. casting device. It is suitable for the overall casting process of cast steel backup rolls of various types and specifications with a net weight of more than 100 tons of composite materials.

Background technique

The cast steel backup roll is a key part in the steel rolling production line, and it is also a vulnerable part. With the continuous increase of steel production, the consumption of backup rolls is also increasing. During the steel plate rolling process, the back-up rolls bear huge bending moments and torques on the rolling mill, and are subject to alternating loads, which are prone to fatigue damage. Internal defects such as inclusions are the internal cause of fatigue damage, so the backup roll must have good internal quality.

Manufacturers of large cast steel backup rolls mainly include WHEMCO Company in the United States, GP Company in Germany, INI STEEL Company in South Korea, and DAVY Company in the United Kingdom. However, only the GP company in Germany can produce cast steel rolls of more than 170 tons, and other companies do not have the ability to produce such large-scale backup rolls. Due to the small number of super-large cast steel backup roll manufacturers, limited production capacity, and continuous expansion of usage, the market is in a serious shortage of supply.

The development difficulties of super-large cast steel backup rolls are mainly due to the large amount of molten steel, difficulty in preparing molten steel, and strict requirements on equipment; the axial dimension of the roll is long, the shrinkage of the solidification process line is large, and tensile stress cracks are likely to occur when shrinkage is hindered, so casting is difficult; molten steel The pouring time is long, secondary oxidation is prone to occur, oxidation inclusions are generated, and the internal quality is difficult to control; the roll is a slender shaft casting, the feeding distance is long, the feeding channel is difficult to keep smooth, and shrinkage cavities and loose defects are prone to occur.

Utility model content

The purpose of this utility model is to provide a casting device for super-large cast steel backup rolls made of composite materials above 100 tons, which can effectively solve the problems of cracks, shrinkage cavities and looseness of large cast steel backup rolls, and make super-large cast steel backup rolls Localization became possible.

The technical scheme of the utility model is:

The utility model mainly refers to the advanced pouring system design, iron mold sand coating process, tangential inner gate rotary filling method, sequential solidification technology, sliding roller during the preparation process of super large cast steel support rolls above 100 tons. Neck technology, electric heating riser technology, computer simulation technology and other technologies, these contents have been included in the Chinese patent application (Patent No. ZL200410021595.5, application date: August 2, 2004, name: cast steel backup roll Casting method; application number 200610048038.1, application date October 18, 2006, name: large cast steel backup roll preparation process). The utility model mainly adopts the pouring process combining down-casting flushing and up-casting, and designs corresponding molds and equipment; adopts molten steel of different materials for pouring, conducts molten steel heat preservation and runner heat preservation technology; adopts multiple group boxes, Multiple electric heating technology and compound riser technology.

1. Combination pouring technology of down-casting flushing and up-casting

(1) Betting and flushing technology: Adopting advanced gating system design principles, a smooth filling gating system without air gaps is designed. The pouring system is composed of a tapered sprue, a runner and a tangential inner gate. According to the weight of poured molten steel and the pouring speed, 1-4 pouring systems are arranged to distribute along the circumference, and multiple pouring systems are poured at the same time. The first metal liquid is all poured by pouring, and when the metal liquid is poured above the roller body, the pouring of the first metal liquid is stopped. After the first metal liquid forms a shell with a certain thickness in the cavity, start to pour the second metal liquid, and replace the unsolidified part of the first metal liquid with the second metal liquid.

(2) Up-casting technology: The molten metal is poured directly from the top of the casting cavity (riser end), and the upper roll neck box and the riser are poured by the up-casting method.

(3) Casting effect: First, pouring and flushing can be performed to complete the pouring of composite materials, and obtain rolls with different materials on the surface and the core. Finally, the upper injection and electric heating and heat preservation can reduce the tendency of cracks, shrinkage cavities and loosening.

(4) Pouring method: The pouring process adopts a smooth filling pouring system. During the pouring process, when the molten metal flows in the sprue, it is in a full state. When the molten metal reaches above the roll body and below the overflow groove, stop pouring. After 30 to 180 minutes, the first metal liquid has formed a solidified layer with a certain thickness, and the second metal liquid is poured, which is also carried out in the form of downcasting. With the pouring of the second metal liquid, the unsolidified part of the first metal liquid is gradually pushed out of the overflow tank and flows into the ladle. When the unsolidified part of the first metal liquid overflows completely, the flushing pouring is completed, the pouring is suspended, the overflow tank is closed, and electroslag is added to the metal liquid surface for electric heating and heat preservation. After heating for 30 minutes, start pouring. The upper roll neck and riser part above the overflow groove is poured using the top pouring technology, directly pouring from the top of the cavity. When the ladle is aligned with the cavity, pouring begins. When performing upper injection, in order to reduce the exposure time of molten steel in the air and the impact force of molten steel on the cavity, the ladle should be as low as possible.

2. Set overflow tank and steel drum

(1) Overflow groove: During the mold design process, an overflow device is installed on the upper roll neck box, and the overflow groove is 200-300mm away from the bottom surface of the upper roll neck box. Its shape is like the tapping trough of a melting furnace, the outer layer is a trapezoidal steel plate trough, and the inner layer is built with insulating bricks.

(2) Ladle: The ladle is similar to a ladle, and its volume is set according to the amount of liquid metal removed during the pouring process. Generally, it is 50-200 tons. The outer layer is a steel plate structure, and the inner layer is built with insulating bricks.

(3) Main function: The function of the overflow tank is to make the first metal liquid be smoothly discharged from the overflow tank when the second metal liquid enters the cavity during the pouring process. The function of the ladle is to contain the discharged metal liquid, and after the pouring is completed, the metal liquid is synthesized into a steel ingot.

(4) How to use: During the molding process, the overflow groove is set on the upper roll neck box, and the inner cavity and the cavity are kept unblocked. After the second metal liquid enters the cavity, the liquid metal level gradually rises, and when it exceeds the overflow tank, the molten metal begins to overflow from the overflow tank. After the molten metal flows out from the overflow tank, it enters the ladle, and the ingots are combined after the pouring is completed.

3. Choose different materials for pouring

(1) Liquid metal composition: the core is made of high-quality carbon steel, and the working layer on the surface of the roll is made of alloy steel.

(2) Purpose: The working surface of the roll is made of alloy steel, which can increase the wear resistance of the material, while the center part is made of high-quality carbon steel, which can effectively improve the toughness of the roll.

(3) How to use: Composite casting is carried out by flushing method, the working layer of the roll body is first cast, and then the core metal is poured to complete the casting of the composite roll.

4. Insulation technology of pouring system

(1) Insulation measures are taken on the outside of the gating system, and the outside of the sprue, runner, and inner runner are all insulated with insulation materials and heated by induction coils.

(2) Main function: During the pouring process, it is necessary to pause for a long time, the diameter of the runner is relatively small, and it is easy to solidify, so that subsequent pouring cannot be carried out. The use of thermal insulation materials and induction heating can keep the pouring system in a liquid state, so that the entire pouring process can be carried out smoothly.

(3) How to use: During the molding process, the outer sides of all runner refractory bricks are wrapped with thermal insulation cotton, and the outer sides are wound with induction coils. When pouring the first molten metal, the runner is heated by the induction coil until the second pouring begins.

5. Multiple group box and multiple electric heating technology

(1) Multiple boxes: During the mold design process, the upper roll neck box and the riser box are designed as multi-section boxes, and the joints are positioned between each section. Before the first betting, when the mold is assembled, it is only assembled to a certain section of the upper roll neck. When the first pouring is finished and the second pouring is ready, the rest of the upper roll neck boxes can be assembled. According to the specific situation, one section, two sections or three sections can be assembled. As the pouring proceeds, the upper roll neck box and riser box are continuously increased.

(2) Multiple times of electric heating: Electric heating starts after the second casting is completed, and electric heating is carried out between each pouring to keep the metal surface in a liquid state.

(3) Main function: When the molten metal shrinks in solid state, the solid metal will receive resistance from the mold, and when the resistance is greater than the high temperature strength of the metal, tensile stress cracks will occur. Using multiple pouring process, the molten metal can be solidified sequentially, so that the roll body and the lower roll neck are solidified first, and after the solid shrinkage is basically completed, the upper roll neck and riser are poured to minimize the shrinkage resistance. In this way, the tensile stress is reduced and tensile stress cracks are avoided.

(4) How to use: During the pouring process, after the second pouring is completed, electric heating and heat preservation is started; before the second pouring, the upper roll neck box is raised, pouring is performed, and then electric heating is performed. Alternate with raising the upper roll neck box and riser box. Until the riser is filled, the final electric heating and heat preservation is carried out.

6. Composite riser technology

(1) Composite riser structure: The composite riser is composed of upper and lower parts, the upper part is a sand mold, and the lower part is made of insulating bricks. The height of the sand mold is 200-1500mm, and the height of the insulation brick masonry layer is 1000-2500mm.

(2) Main function: The upper part of the composite riser has strong high temperature resistance and corrosion resistance. The lower part uses insulation bricks, which can increase the feeding distance of the riser and reduce the looseness of the axis.

(3) How to use: In the molding process, first surround the insulation bricks into a cylindrical shape, tie them up with steel belts, put them into the riser box, hit the back sand behind the insulation bricks until they are solid. After the molding of the lower part is completed, sand molds are used for the upper part, chromite sand is used for the face sand, and ordinary quartz sand is used for the back sand.

3. Multiple electric heating process

(1) Electric heating riser structure: The electric heating riser used in the utility model is an electroslag heating riser. The electroslag heating riser is composed of heating electrodes and electroslag, the electrodes are graphite electrodes, and the electroslag is a mixture of Al ₂ O ₃ , CaO and CaF. By weight, Al ₂ O ₃ accounts for 30-70%, CaO accounts for 10-15%, and CaF ₂ accounts for 20-50%. The three kinds of electroslag raw materials are placed in separate bags before use, and are added to the molten pool according to the weight percentage. After filling the mold, add electroslag to the riser, the electroslag covers the entire liquid surface, and the thickness of the electroslag is 50-150mm; then the graphite electrode is supplied with power through the power supply device, and the riser is heated and kept warm; single-electrode or multi-electrode, DC Or AC electroslag heating and heat preservation.

(2) Use of electric heating riser: During the pouring process of bottom injection castings, the temperature above the molten metal is low and the temperature below is high, which is not conducive to feeding. Electric heating is carried out in the middle stage, mainly to keep the metal liquid level in a liquid state, so that the casting does not have cold shut defects. Finally, the function of electric heating is to heat the molten metal above to form a positive temperature gradient, which is beneficial for the riser to complete feeding.

(3) How to use: The electric heating voltage is 50-100V, the current is 500-1500A, and the transformer power is 25-150KW. The intermediate heating time is determined according to the pouring requirements. When the next pouring is required, the electric heating is temporarily stopped. The final electric heating time is determined according to the size of the riser, and the specific time is shown in Table 1.

Table 1 Comparison of Riser Diameter and Electric Heating Time Process Parameters

Riser diameter 500～700mm 700～1000mm 1000～1500mm ＞1500mm Heating time (h) 3～4 4～5 10～15 30～36

Note: Riser diameter refers to the average diameter at the height of the riser.

The utility model has the following beneficial effects:

1. The casting device and method of the super-large cast steel backup roll of composite material above 100 tons of the utility model is an organic combination of multiple technologies, including advanced gating system design principles, iron mold sand-coating technology, and tangential ingate rotation Mold filling method, sequential solidification technology, sliding roll neck technology, combined technology of lower injection flushing method and upper injection, multiple box technology, multiple pouring technology, multiple electric heating technology and composite riser technology. The utility model is suitable for the casting process of various models and specifications of cast steel support rolls of composite material above 100 tons, and can make super-large cast steel support rolls manufactured by casting method.

2. The utility model has developed a casting method for super-large composite material cast steel backup rolls above 100 tons, and casts composite material cast steel backup rolls by using the pouring technology combined with down-casting flushing and up-casting. The working layer and the core of the roll body are made of different materials. Through the design of overflow tanks, steel drums, etc., measures such as runner insulation technology and liquid level protection have been used to carry out multiple pours, reducing the height of the riser and reducing the metal The static pressure of the liquid reduces the resistance of the casting mold to the casting and avoids the generation of tensile stress cracks. The use of multiple group boxes, multiple electric heating and composite riser technology effectively solves the cracks and shrinkage of cast steel backup rolls. Holes, porosity and other problems have made it possible to localize super-large cast steel backup rolls.

3. The utility model uses molten steel of two kinds of materials for pouring, so that the material of the working layer of the roll is different from that of the core, which increases the wear resistance of the roll, ensures the toughness of the roll, and improves the service life of the roll.

4. The utility model adopts the composite riser technology, which increases the feeding distance of the riser, enhances the feeding capacity of the riser, reduces the shrinkage cavity and loose tendency of the casting, reduces the volume of the riser, and improves the forming efficiency of the casting. possibility.

Description of drawings

Fig. 1 is a schematic diagram of a casting device for composite cast steel back-up rolls of more than 100 tons of the utility model;

Among them: 1-the first molten metal; 2-steel drum; 3-the second molten metal; 4-overflow tank; 5-the upper roll neck box of the first section; 6-the upper roll neck box of the second section; 7-the first riser box; 8-the second riser box; 9-electroslag; 10-graphite electrode; 11-tundish; 12-sprue; 13-sand mold; 14-roller body iron mold; 15-lower roll neck box; 16-base; 17-runner; 18 plug rod.

Detailed ways

Describe the utility model in detail below in conjunction with accompanying drawing and embodiment.

As shown in Figure 1, the schematic diagram of the casting device of the composite super-large cast steel support roll above 100 tons of the utility model. The sand mold is adopted, the riser is a composite riser, the lower surface of the riser is made of insulation bricks, the back sand is used for the back, and the upper part of the riser is made of sand mold. Set base 16, lower roll neck box 15, roll body iron mold 14, first section upper roll neck box 5, second section upper roll neck box 6, first section riser box 7, second section riser box from bottom to top. Mouth box 8 etc. When assembling the mold before pouring for the first time, it is only assembled to the upper roll neck box 5 of the first joint. The first molten metal 1 enters the cavity through the tundish 11 with plunger system, the sprue 12 and the runner 17. After the first molten metal fills the iron mold 14 of the roller body, close the stopper rod 18 of the tundish 11 , stop the betting of the first section of molten metal 1. While pouring the first type of molten metal 1, the sprue 12 and runner 17 are heated by induction until the second type of molten metal 3 enters the cavity of the casting, then the induction heating of the sprue is stopped. After 30 to 180 minutes, the second molten metal 3 enters the casting cavity through the tundish 11, the sprue 12 and the runner 17 placed in the sand mold 13, and the unsolidified first molten metal in the cavity 1 upward, when the liquid level reaches the overflow tank 4, the first metal liquid 1 flows into the steel ladle 2 through the overflow tank 4, until all the unsolidified first metal liquid 1 overflows, stop the second The betting of the molten metal 3 closes the overflow tank 4. Add electroslag 9 to the upper roll neck box of the first section, adjust the position of the graphite electrode 10, and start electric heating in the upper roll neck box 5 of the first section. After heating for 30 to 180 minutes, remove the graphite electrode 10, align the ladle with the upper roll neck box 5 of the first section, start pouring, and then conduct electric heating again after filling. This process is carried out sequentially until the second riser box is filled, and the final electric heating and heat preservation is carried out. The number of sections of the upper neck box and riser box depends on the weight and length of the roll.

Example 1

The first metal material used in this embodiment is Cr1, the second metal is No. 45 steel, and the weight of poured metal liquid is 150 tons. Its casting process is as follows:

1) The pouring system adopts tangential inner gate rotary pouring, and the tundish and pouring system are designed according to the principle of smooth filling, and the runner insulation technology is adopted. 2) Composite riser, the height of the riser is 2800mm, of which the height of the sand mold is 1500mm, and the height of the refractory brick is 1300mm. 3) Using 4 times of boxing, 6 times of pouring, and 5 times of electric heating. The final electric heating after the molten metal fills the pouring system for 12 hours. 4) When assembling the mold for the first time, it is assembled to the first section box of the upper roll neck, and the first molten metal is poured through the designed smooth filling and pouring system, using double runners and filling at a pouring speed of 9 tons per minute. Type, after the molten metal fills the iron mold of the roller body, stop pouring. After the first molten metal starts pouring, the runner is heated by induction until the second molten metal is poured and the heating stops. After 60 minutes, pour the second metal liquid, and when the unsolidified first metal liquid overflows completely, close the overflow tank, and stop the betting of the second metal liquid. Add electroslag to the upper roll neck box of the first section, and start electric heating and heat preservation. After heating for 30 minutes, remove the graphite electrode, align the ladle with the upper roll neck box of the first section, and start pouring from the top of the upper roll neck box of the first section. heating. After 60 minutes of electric heating, remove the graphite electrode, assemble the second section of the upper roll neck box, and perform the second upper injection. After filling the second section of the upper roll neck box, conduct electric heating again. After 70 minutes of electric heating, remove Open the graphite electrode, assemble the first riser box, and inject from the top of the first riser box. After the metal liquid fills the first riser box, add electroslag and start electric heating. After heating for 90 minutes, Assemble the second riser box for the last pouring from the top. After pouring, add electroslag to the second riser box for final electric heating and heat preservation for 12 hours. In this embodiment, the heat preservation electroslag is a mixture of Al ₂ O ₃ , CaO and CaF ₂ , by weight, Al ₂ O ₃ accounts for 40%, CaO accounts for 10%, CaF ₂ accounts for 50%, and the electroslag thickness is 120mm. The current is 800A, the voltage is 125V, and the heating power is 100kw.

The first pouring was successfully completed, and the molten steel rose steadily. After electric heating, the electric heating equipment works normally. The produced composite cast steel back-up roll is subjected to ultrasonic testing after machining, which meets the roll flaw detection standard.

Example 2

The first metal material used in this embodiment is Cr2, the second metal is No. 45 steel, and the weight of poured metal liquid is 155 tons. Its casting process is as follows:

1) The pouring system adopts tangential inner gate rotary pouring, and the tundish and pouring system are designed according to the principle of smooth filling, and the runner insulation technology is adopted. 2) Composite riser, the height of the riser is 2800mm, of which the height of the sand mold is 1500mm, and the height of the refractory brick is 1300mm. 3) Using 4 times of boxing, 6 times of pouring, and 5 times of electric heating. The final electric heating after the molten metal fills the pouring system for 13 hours. 4) When assembling the mold for the first time, it is assembled to the first section box of the upper roll neck, and the first molten metal is poured through the designed smooth filling and pouring system, using double runners and filling at a pouring speed of 10 tons/min. Type, after the molten metal fills the iron mold of the roller body, stop pouring. After the first molten metal starts pouring, the runner is heated by induction until the second molten metal is poured, and the heating is stopped. After 70 minutes, pour the second metal liquid, after the unsolidified first metal liquid overflows completely, close the overflow tank, stop the betting of the second metal liquid. Add electroslag to the upper roll neck box of the first section, and start electric heating and heat preservation. After heating for 40 minutes, remove the graphite electrode, align the ladle with the upper roll neck box of the first section, and start pouring from the top of the upper roll neck box of the first section. heating. After 70 minutes of electric heating, remove the graphite electrode, assemble the second section of the upper roll neck box, and perform the second upper injection. After filling the second section of the upper roll neck box, perform electric heating again. Open the graphite electrode, assemble the first riser box, and inject from the top of the first riser box. After the metal liquid fills the first riser box, add electroslag and start electric heating. After heating for 90 minutes, Assemble the second riser box for the last pouring from the top. After pouring, add electroslag to the second riser box for final electric heating and heat preservation. The heating time is 13 hours. In this embodiment, the thermal insulation electroslag is a mixture of Al ₂ O ₃ , CaO and CaF ₂ , in terms of weight ratio, Al ₂ O ₃ accounts for 70%, CaO accounts for 10%, CaF ₂ accounts for 20%, and the electroslag thickness is 150mm. The current is 1000A, the voltage is 150V, and the electric heating power is 150kw.

The second pouring was successfully completed, and the molten steel rose steadily. After electric heating, the electric heating equipment works normally. The produced composite cast steel back-up roll is subjected to ultrasonic testing after machining, which meets the roll flaw detection standard.

The utility model work process and result:

The utility model is used to cast super-large composite cast steel support rolls above 100 tons. During the pouring process, two metal liquids of different materials are used to obtain different performances for the working layer of the roll body, the body of the roll body, and the upper and lower roll necks. , to meet the needs of the roll. The combination of down-casting flushing method and up-casting method, multiple pouring technology and sprue insulation technology are used to make the molten metal fill smoothly and effectively avoid air entrainment and inclusion defects. Multiple electric heating techniques are used to ensure that there are no cold shut defects in the casting. The composite riser is used to increase the feeding capacity of the riser, so that the large cast steel backup roll has no shrinkage cavity and loose defects. The flaw detection results are in full compliance with national standards.

Claims (6)

1. A casting device for a super-large cast steel backup roll made of composite material above 100 tons, which adopts a mold integral casting device, and has a base, a lower roll neck box, an iron mold for the roll body, an upper roll neck box, and a risker in sequence from bottom to top. The gating box and gating system are characterized in that: the gating system is a combined structure of lower and upper gating, the upper roll neck box and the riser box are of segmented structure, an overflow groove is set on the upper roll neck box, and an overflow groove is set outside the mold. It is filled with steel barrels, and there is an electric heating riser in the riser box. 2. According to claim 1, the casting device for super-large cast steel backup rolls made of composite materials above 100 tons is characterized in that: when the combination structure of lower injection flushing and upper injection is adopted, the lower injection gating system consists of a tundish, a direct It consists of sprue, runner and tangential ingate, and 1 to 4 gating systems are placed around the circumference. 3. According to claim 2, the casting device for super-large cast steel backup rolls made of composite materials above 100 tons is characterized in that: the outer sides of all runner refractory bricks are wrapped with thermal insulation cotton, and the outer sides are wound with induction coils. 4. According to claim 1, the casting device for super-large cast steel backup rolls made of composite materials above 100 tons is characterized in that: the multi-section upper roll neck box and the riser box are used, and the upper roll neck box and the riser box are respectively It consists of 2 to 4 sections, each section is positioned by a seam, and each section is 300 to 1200mm high. 5. According to claim 1, the casting device for super-large cast steel backup rolls made of composite materials above 100 tons is characterized in that: a composite riser is used, the riser is made of composite materials, and the upper part of the riser is a sand mold with a height of 200-1500mm, the lower part of the riser is built with insulating bricks, and the height is 1000-2500mm. 6. The casting device for super-large cast steel backup rolls made of composite material above 100 tons according to claim 1, characterized in that: the electric heating riser includes electroslag and graphite electrodes for heating the electroslag.

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