阅读说明：本技术 一种细化h13中空铸件液析碳化物的方法 (Method for refining H13 hollow casting liquated carbide ) 是由 李少英 郭汉杰 郭靖 习小军 于 2021-08-13 设计创作，主要内容包括：本发明涉及模具钢制备技术领域,提供了一种细化H13中空铸件液析碳化物的方法,包括将原材料进行真空感应熔炼,得到感应熔炼铸锭；感应熔炼铸锭经表面处理后作为母材,在中频感应炉内冶炼,冶炼过程中钢液上部覆盖一层冶炼渣；中频感应炉冶炼结束后,将钢液和渣液倒入带有浇铸模具的立式离心机内,室温下立式离心机在不同转速下旋转产生复合离心场,降低铸锭枝晶间元素偏析程度,增加铸锭中液析碳化物生成固相率,从而达到细化H13中空铸件中液析碳化物尺寸的效果。(The invention relates to the technical field of preparation of mold steel, and provides a method for refining H13 hollow casting liquated carbide, which comprises the steps of carrying out vacuum induction melting on raw materials to obtain an induction melting ingot; the induction smelting cast ingot is used as a base material after surface treatment, smelting is carried out in a medium-frequency induction furnace, and a layer of smelting slag covers the upper part of the molten steel in the smelting process; after the smelting of the medium-frequency induction furnace is finished, molten steel and slag liquid are poured into a vertical centrifuge with a casting die, the vertical centrifuge rotates at different rotating speeds at room temperature to generate a composite centrifugal field, the segregation degree of elements among dendrites of the cast ingot is reduced, the generation solid phase rate of the liquated carbide in the cast ingot is increased, and therefore the effect of refining the size of the liquated carbide in the H13 hollow casting is achieved.)

1. A method of refining H13 hollow castings hydroeducts, the method comprising:

s1, preparing a raw material for smelting and preparing an H13 ingot;

s2, smelting the raw materials in a vacuum induction furnace to obtain an H13 casting blank;

s3, smelting the casting blank in a medium-frequency induction furnace, and controlling the tapping temperature to be 1660-1680 ℃;

and S4, pouring the smelting molten steel and the smelting slag into a centrifuge casting die for composite centrifugal field liquid slag casting to obtain the H13 hollow casting with refined liquated carbide.

2. The method for refining H13 hollow casting liquated carbides according to claim 1, wherein in step S4, the composite centrifugal field liquid slag casting is specifically:

s4.1 preparation stage: the casting die is fixed on a centrifuge, the centrifuge is started before the intermediate frequency induction furnace discharges steel, the rotating speed of the centrifuge is set, and the casting die is cooled;

s4.2, casting stage: the mixture of the slag and the molten steel enters a casting mold, under the action of a composite centrifugal field, the centrifugal speed of the molten steel is greater than that of the slag, and the slag is gathered towards the center of the casting mold to form a temperature field with high intermediate temperature and low edge temperature; the composite centrifugal field is specifically as follows: the starting speed is 1000-^-1The time is 1-2 min; then the rotation speed is 1100-1150 r.min^-1The time is 6-8 min; then the rotation speed is 1200-1300 r.min^-1The time is 3-5 min;

s4.3, finishing stage: after the casting is finished, the centrifugal machine continues to work for a period of time to ensure that the molten steel and the molten slag are completely solidified, and the centrifugal machine is closed; and after the mold is cooled, taking out the hollow casting, and removing the surface slag layer to obtain the H13 hollow casting with refined liquated carbide.

3. The method for refining H13 hollow casting liquated carbide according to claim 2, wherein in step S4.1, the rotating speed of a centrifugal machine is 1000-1300 r-min^-1(ii) a Cooling the mold by helium, specifically: a movable helium gas channel is arranged at the center of the casting die, and the flow rate of the helium gas is 20-100 L.min^-1And cooling the casting mold, wherein the aeration time is 1-2 min.

4. The method for refining H13 hollow casting liquated carbides according to claim 2, wherein in step S4.3, after the casting stage is completed, the centrifuge continues to work for 10-15 min.

5. The method for refining H13 hollow casting liquated carbides according to claim 1, wherein in step S2, the raw material is melted and refined, and casting is performed under argon atmosphere after the refining is finished to obtain H13 ingot; the size length of the vacuum induction melting ingot is 300-350 mm, and the diameter is 90-100 mm.

6. The method for refining H13 hollow cast liquated carbides according to claim 1, wherein in step S3 the vacuum induction melting ingot is castSmelting in a medium-frequency induction furnace by taking the surface treated material as a base material, wherein argon is used for protection in the smelting process; the upper part of the molten steel is covered with a layer of smelting slag, and the components of the smelting slag are as follows: 20-30% of CaO and SiO₂10-20%, MgO 20-30%, and the balance of CaF₂(ii) a The smelting temperature range is 1500-1750 ℃.

7. The method for refining H13 hollow casting liquated carbides according to claim 5, wherein in step S2, the vacuum degree is 5 x 10 when melting in the vacuum induction furnace^-3～8×10^-2Pa, the casting temperature of the vacuum induction melting molten steel is 1500-1550 ℃, and the oxygen content of the vacuum induction melting cast ingot is 50-70 ppm.

8. The method for refining H13 hollow casting liquated carbide according to claim 6, wherein in step S3, the flow of argon gas in the medium frequency induction furnace is 10-50L-min^-1And the oxygen content in the molten steel after the medium-frequency induction furnace is smelted is 20-40 ppm.

9. The method for refining H13 hollow casting liquated carbides according to claim 1, wherein in the step S4, the segregation degree of interdendritic elements in the hollow casting is reduced by 9-15%; the solid phase rate of the generated liquated carbide is increased by 5-10%, and the particle size is reduced by 10-20%.

10. A composite centrifugal field liquid slag casting refined H13 hollow casting, which is characterized by being prepared by the method for refining the H13 hollow casting liquated carbide according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of preparation of die steel, in particular to a method for refining H13 hollow casting liquated carbide.

Background

The H13 steel is widely applied to the manufacturing field of high-wear-resistant parts such as a hot forging die, a hot extrusion die, a non-ferrous metal die-casting die and the like because of high hardenability, high red hardness and high thermal fatigue resistance. Because of the high content of carbon element and alloy element in H13 steel, it is easy to form large size liquated carbide during solidification. The existence of large-size liquated carbide seriously affects the service performance of steel, on one hand, the formation of the liquated carbide consumes alloy elements in a steel matrix, so that the strengthening effect of the alloy elements on the steel is weakened, and the strength of the steel matrix is reduced; on the other hand, large-sized liquated carbides destroy the solidification structure of the steel, thereby lowering the impact properties of the steel. Therefore, it is necessary to control the formation of the liquated carbide and finely disperse the same during the solidification process.

At present, the H13 steel is usually produced at home and abroad by adopting the processes of electric furnace steel making, continuous casting, electroslag remelting, forging, heat treatment and the like. However, even electroslag steel has a structure which hardly meets the standard requirement of H13 steel by adopting the conventional forging heating and post-forging annealing process. In the heat treatment process, a high-temperature diffusion link is added to refine the macrostructure of the H13 forge piece and eliminate the net-shaped carbide, and the technology is reported and applied. The national invention patent (application number: CN104726659A) discloses a heat treatment process for improving the macroscopic crystal and microstructure of an H13 forge piece, and the method adopts a high-temperature diffusion, normalizing and isothermal spheroidizing annealing mode to refine the coarse crystal and eliminate network carbide. The research shows that the forging and heat treatment process is improved to refine or eliminate carbide in H13 steel, and during solidification, rod-shaped and block-shaped liquated carbide with the size larger than 20 mu m is generated in H13 cast ingot. However, studies on refining carbides during solidification of H13 steel have not been reported.

In conclusion, how to refine large-size liquated carbides in the cast ingot in the solidification process is an urgent problem to be solved for producing high-performance H13 die steel.

Disclosure of Invention

The invention aims to overcome at least one of the defects of the prior art, and provides a method for refining the liquated carbide of the H13 hollow casting, which can effectively reduce the segregation of interdendritic elements in the H13 casting and refine the liquated carbide in the H13 casting.

The invention adopts the following technical scheme:

a method for refining H13 hollow casting liquated carbides comprises the following steps:

s1, preparing a raw material for smelting and preparing an H13 ingot;

s2, smelting the raw materials in a vacuum induction furnace to obtain an H13 casting blank;

s3, smelting the casting blank in a medium-frequency induction furnace, and controlling the tapping temperature to be 1660-1680 ℃;

and S4, pouring the smelting molten steel and the smelting slag into a centrifuge casting die for composite centrifugal field liquid slag casting to obtain the H13 hollow casting with refined liquated carbide.

The invention is particularly suitable for H13 hollow castings with the specification of 50-100 kg, the outer diameter of 400-500 mm and the inner diameter of 300-400 mm.

In any one of the foregoing possible implementation manners, there is further provided an implementation manner, and in step S4, the liquid slag casting in the composite centrifugal field specifically includes:

s4.1 preparation stage: the casting die is fixed on a centrifuge, the centrifuge is started before the intermediate frequency induction furnace discharges steel, the rotating speed of the centrifuge is set, and the casting die is cooled;

s4.2, casting stage: the mixture of the slag and the molten steel enters a casting mold, under the action of the composite centrifugal force, the centrifugal speed of the molten steel is greater than that of the slag, and the slag is gathered towards the center of the casting mold to form a temperature field with high intermediate temperature and low edge temperature; the composite centrifugal force is specifically as follows: the starting speed is 1000-^-1The time is 1-2 min; rotation speed of 1100-1150 r.min^-1The time is 6-8 min; the rotation speed is 1200-1300 r.min^-1The time is 3-5 min;

s4.3, finishing stage: after the casting is finished, the centrifugal machine continues to work for a period of time to ensure that the molten steel and the molten slag are completely solidified, and the centrifugal machine is closed; and after the mold is cooled, taking out the hollow casting, and removing the surface slag layer to obtain the H13 hollow casting with refined liquated carbide.

In any of the above possible implementation manners, there is further provided an implementation manner, in step S4.1, the rotation speed of the centrifuge is 1000 to 1300r · min^-1(ii) a Cooling the mold by helium, specifically: a movable helium gas channel is arranged at the center of the casting die, and the flow rate of the helium gas is 20-100 L.min^-1And cooling the casting mold, wherein the aeration time is 1-2 min.

In any of the above possible implementations, there is further provided an implementation manner that after the casting mold is cooled, the helium gas passage is quickly removed, and the pouring gate with the argon atmosphere protection is connected to the intermediate frequency induction furnace and the casting mold.

Any one of the possible implementation manners described above further provides an implementation manner, the intermediate frequency induction furnace is inclined to the side of the runner, and the inclination angle is 10-120 degrees; because the density of the slag is lower than that of the molten steel, a small amount of slag preferentially enters the casting mold under the action of gravity, and a layer of slag crust is rapidly formed under the action of composite centrifugal force to cover the inner wall of the casting mold; and then, the mixture of the slag and the molten steel enters the mold, the centrifugal speed of the molten steel is higher than that of the slag under the action of the composite centrifugal force, the slag is gathered towards the center of the casting mold to form a temperature field with high intermediate temperature and low edge temperature, and the casting is favorably solidified from the outer edge to the center.

In step S4.3, after the casting stage is completed, the centrifuge continues to work for 10-15 min.

In any of the above possible implementation manners, there is further provided an implementation manner, in step S2, melting and refining the raw material, and after the refining is finished, casting in an argon atmosphere to obtain an H13 ingot; the size length of the vacuum induction melting ingot is 300-350 mm, and the diameter is 90-100 mm.

In step S3, the vacuum induction melting ingot is treated to obtain a base material, and is smelted in a medium frequency induction furnace, and argon is used for protection during the smelting process; the upper part of the molten steel is covered with a layer of smelting slag which is formedDividing into: 20-30% of CaO and SiO₂10-20%, MgO 20-30%, and the balance CaF₂(ii) a The smelting temperature range is 1500-1750 ℃.

In any of the foregoing possible implementation manners, there is further provided an implementation manner that, in step S2, the vacuum degree during melting in the vacuum induction furnace is 5 × 10^-3～8×10^-2Pa, the casting temperature of the vacuum induction melting molten steel is 1500-1550 ℃, and the oxygen content of the vacuum induction melting cast ingot is 50-70 ppm.

In any of the above possible implementation manners, there is further provided an implementation manner that in step S3, the flow rate of argon gas in the intermediate frequency induction furnace is 10 to 50L · min^-1And the oxygen content in the molten steel after the medium-frequency induction furnace is smelted is 20-40 ppm.

According to any possible implementation manner, an implementation manner is further provided, the iron oxide scales on the surface of the vacuum induction melting ingot, the head and the tail of the ingot and the like of the base material smelted by the medium-frequency induction furnace are removed by a machining manner, and the surface of the base material smelted by the medium-frequency induction furnace is smooth and free of defects.

In any of the above possible implementation manners, there is further provided an implementation manner in which the centrifugal machine is a vertical centrifugal machine, and the flow rate of argon in a pouring channel of the vertical centrifugal machine is 10 to 20 l.min^-1。

Any of the possible implementations described above further provides an implementation that the chemical composition range of the hollow casting of H13 conforms to the composition range specification for the casting of H13 in the standard "NADCA # 207-2003".

By using the method, the segregation degree of interdendritic elements in the hollow casting can be reduced by 9-15%; the solid phase rate of the generated liquated carbide is increased by 5-10%, and the particle size is reduced by 10-20%.

On the other hand, the invention also provides a composite centrifugal field liquid slag casting refined H13 hollow casting which is prepared by using the method for refining the H13 hollow casting liquated carbide.

Several explanations regarding the improvements of the present invention:

1. the working principle is as follows: the generation of liquated carbides is mainly caused by the segregation of interdendritic elements. The composite centrifugal field has different centrifugal speeds, certain tangential acceleration can be generated by conversion among the different centrifugal speeds, and the crushing degree of dendritic crystals can be further enhanced under the action of the tangential acceleration, so that the element segregation degree among the dendritic crystals can be further weakened under the action of the composite centrifugal field, and refining of the liquated carbide is facilitated.

2. Composite centrifugal field centrifugal speed setting

The starting rotating speed is 1000-^-1The time is 1-2 min; the reason for selecting this parameter is that the shell formed on the outer side of the casting is thin at the initial stage of solidification, and excessively high rotation speed tends to cause cracking of the shell, and the stable shell formation time is about 1 min.

Rotation speed of 1100-1150 r.min^-1The time is 6-8 min; after the shell of the billet is stabilized, the rotating speed of the die is increased to generate a certain shearing acting force in the molten steel, the forced convection action at the front of solidification is further enhanced under the action of the shearing force, the segregation of elements among dendrites is weakened, the liquated carbide is refined, the molten steel in the die reaches the rotating speed of the die after about 5min, and the shearing force disappears.

The rotation speed is 1200-1300 r.min^-1The time is 3-5 min; when the shearing force disappears, the rotating speed needs to be further increased to ensure the refining effect of the liquated carbide, and the solidification process of the casting is finished after about 3 min.

3. Composite centrifugal force casting slag system component setting

(1) Because the smelting work before casting is finished in the medium-frequency induction furnace, in order to prevent the MgO furnace lining from corroding and polluting molten steel, the MgO content in the slag system is controlled between 20 percent and 30 percent, and the MgO saturation solubility of the slag system is ensured to be reached, thereby avoiding the corrosion of an MgO crucible;

(2) in the slag-steel interface reaction, the deoxidizing element of H13 steel is mainly silicon element, and the alkalinity of slag system (% CaO/% SiO)₂) Larger than 1.0, the forward progress of the silicon deoxidation reaction can be ensured;

(3) the content of calcium fluoride in the slag system is more than 20 percent, the slag can be ensured to have better fluidity, and under the action of centrifugal force, a slag crust can be formed in a shorter time, so that the adhesion between a mould and a casting is prevented, and the smooth surface of the casting is ensured.

It should be noted that the design of the unique slag system of the present invention is of great significance for achieving the purpose of the present invention and obtaining high quality products. The common slag system design in the prior art does not consider the influence of the fluidity of the slag system on the centrifugal force to form slag crust, and does not consider key factors of ensuring the forward progress of the silicon deoxidation reaction and the like.

4. Setting of centrifugal speed: from the perspective of refining the liquated carbide, the higher the rotating speed of the centrifugal machine, the greater the centrifugal force action, the weaker the degree of segregation of interdendritic elements, and the size of the liquated carbide is easy to be refined. However, in the actual production process, the higher the rotation speed of the centrifuge, the greater the convection heat transfer action between the mold and the air, which means that the solidification time of the molten steel is shortened and the action time of the centrifugal force is reduced, in which case, it is disadvantageous to the refinement of the liquated carbide. According to a large number of experiments, the centrifugal speed is determined to be 1000-1300 r.min^-1。

5. Composite centrifugal force casting temperature: sufficient composite centrifugal action time needs to be ensured, the solidification time of the molten steel is prolonged as far as possible, and a great number of experiments confirm that the best effect is achieved when the casting temperature of the molten steel is controlled between 1660-1680 ℃.

6. Selection of argon shield pouring channel

The argon shield runner is chosen during casting to prevent oxygen in the air from entering the molten steel. During casting, the increase in oxygen content of the molten steel increases the size of oxide inclusions and thus increases the size of the eutectoid carbides centered on the oxide inclusions.

7. Helium cooling system option

The cooling time of the outer edge of the centrifugal casting is shorter than the interior of the centrifugal casting, and the centrifugal force has less agitation of the solidification front. In order to reduce the size of the liquefied carbide at the position, the supercooling degree at the time of solidification at the position needs to be increased as much as possible. The helium cooling mold can just meet the requirement.

The invention has the beneficial effects that:

(1) the invention provides a smelting and casting process for refining the size of a liquated carbide in an H13 hollow casting; in addition, the centrifugal force action time is short at the position of the outer surface of the casting, when the molten steel is poured into the helium cooled mould, a chilling layer is easy to form, a liquated carbide is refined, the segregation of interdendritic elements in the H13 hollow casting is reduced, and the refinement of the liquated carbide in the H13 hollow casting is realized.

(2) The method of the invention carries out smelting in a medium frequency induction furnace with argon protection, carries out temperature control before tapping (in addition, can ensure sufficient centrifugal force acting time), can effectively reduce the oxygen content in H13 cast ingots, and controls the oxygen content below 40ppm so as to reduce the size of oxide inclusions, thereby refining the liquated carbide taking the oxide inclusions as cores.

(3) In the process of casting the liquid slag in the composite centrifugal field, the method of the invention cools the die by helium gas, can ensure that the liquid steel and the slag liquid can quickly form a chilling layer with uniform and fine tissues after entering the die, and is beneficial to refining the liquated carbide on the outer surface of the casting.

Drawings

FIG. 1 shows the morphology of the liquated carbides in the H13 hollow casting obtained in example 1.

FIG. 2 shows the morphology of the liquated carbides in the H13 hollow casting obtained in example 2.

FIG. 3 shows the morphology of the liquated carbides in the H13 hollow casting obtained in comparative example 1.

FIG. 4 is a graph showing a comparison of the widths of interdendritic element-rich regions in H13 hollow castings obtained in examples 1 and 2 and comparative example 1.

FIG. 5 is a graph showing the segregation ratio of interdendritic elements in H13 hollow castings obtained in examples 1 and 2 and comparative example 1.

FIG. 6 is a graph showing the size distribution of the liquated carbides in the H13 hollow castings obtained in examples 1 and 2 and comparative example 1.

Fig. 7 shows photographs of the liquated carbides at the outer edge of the helium-free cooled mold casting.

FIG. 8 is a photograph showing the absence of precipitated carbides at the outer edge of a mold casting cooled with helium.

Detailed Description

Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that technical features or combinations of technical features described in the following embodiments should not be considered as being isolated, and they may be combined with each other to achieve better technical effects. In the drawings of the embodiments described below, the same reference numerals appearing in the respective drawings denote the same features or components, and may be applied to different embodiments.

The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The embodiment of the invention provides a method for refining H13 hollow casting liquated carbide, which comprises the following steps:

s1, preparing raw materials for smelting and preparing H13 cast ingots: the invention has no special requirement on the raw materials, and the raw materials for preparing the H13 ingot and the component proportion of each raw material are adopted, so that the chemical component range of the prepared H13 ingot is ensured to meet the component range of the H13 ingot in the standard of NADCA # 207-2003;

s2, smelting the raw materials in a vacuum induction furnace to obtain an H13 casting blank: in the vacuum induction smelting process, the raw materials are melted and refined, the temperature is preferably controlled for 5-10 min before molten steel casting, and then casting is carried out in an argon atmosphere to obtain H13 cast ingots; the size length of the vacuum induction melting ingot is preferably 300-350 mm, and the diameter is preferably 90-100 mm;

preferably, the vacuum degree of the vacuum induction melting process is 5 x 10^-3～8×10^-2Pa。

Preferably, the casting temperature of the vacuum induction melting molten steel is 1500-1550 ℃.

Preferably, the oxygen content of the induction melting ingot obtained by vacuum induction melting is 50-70 ppm.

Optionally, the vacuum degree of the vacuum induction melting process can be 5 × 10^-3Pa、1×10^-2Pa、8×10^-2Pa and 5X 10^-3～8×10^-2Any value between Pa; the temperature control before the casting of the vacuum induction melting molten steel can be any value between 5min, 8min, 10min and 5-10 min; the casting temperature of the vacuum induction melting molten steel can be any value between 1500 ℃, 1525 ℃, 1550 ℃ and 1500-1550 ℃; the oxygen content of the induction melting ingot obtained by vacuum induction melting can be any value of 50ppm, 60ppm, 70ppm and 50-70 ppm; the size length of the vacuum induction melting ingot can be any value among 300mm, 325mm, 350mm and 300-350 mm, and the diameter can be any value among 90mm, 95mm, 100mm and 90-100 mm.

S3, smelting the casting blank in a medium-frequency induction furnace: and (3) performing surface treatment on the vacuum induction melting cast ingot to serve as a base metal, and smelting in a medium-frequency induction furnace. Argon is used for protection in the smelting process; the upper part of the molten steel is covered with a layer of smelting slag, and the components of the smelting slag are preferably as follows: 20-30% of CaO and SiO₂10-20%, MgO 20-30%, and the balance CaF₂(ii) a The preferable smelting temperature range is 1500-1750 ℃. After the smelting of the medium-frequency induction furnace is finished, the tapping temperature is preferably controlled between 1660 and 1680 ℃;

preferably, the oxide scales on the surface of the vacuum induction melting ingot, the head and the tail of the ingot and the like of the base material obtained by medium-frequency induction melting are removed by a machining mode, so that the surface of the base material obtained by medium-frequency induction melting is smooth and free of defects.

Preferably, the flow of argon in the intermediate frequency induction furnace is 10-50 L.min^-1。

Preferably, the oxygen content in the molten steel after the molten steel is smelted by the medium-frequency induction furnace is 20-40 ppm.

Optionally, the medium frequency inductionThe flow of argon in the furnace is 10 L.min^-1、30L·min^-1、50L·min^-1And 10 to 50 L.min^-1Any value in between; the smelting slag comprises the following components: CaO can be 20%, 25%, 30% or 20-30%, SiO₂Can be any value of 10%, 15%, 20% and 10-20%, MgO can be any value of 20%, 25%, 30% and 20-30%, the balance being CaF₂(ii) a The medium-frequency induction melting temperature can be any value between 1500 ℃, 1625 ℃, 1750 ℃ and 1500-1750 ℃; the tapping temperature of the medium-frequency induction smelting molten steel can be any value between 1660 ℃, 1665 ℃, 1680 ℃ and 1660-1680 ℃; the oxygen content in the molten steel after the smelting in the medium frequency induction furnace can be any value among 20ppm, 30ppm, 40ppm and 20-40 ppm.

S4, pouring the molten steel smelted by the medium-frequency induction furnace and the smelting slag into a vertical centrifuge casting die for centrifugal force electroslag casting, wherein the composite centrifugal force electroslag casting process comprises the following three stages:

s4.1 preparation stage: starting a vertical centrifuge before tapping of the medium-frequency induction furnace, wherein the rotating speed of the vertical centrifuge is preferably set to be 1000-1300 r.min^-1The casting mould is fixed on a vertical centrifuge; a movable helium gas channel is arranged in the center of the casting die, and the preferable flow rate of the helium gas is 20-100 L.min^-1Cooling the mold, wherein the aeration time is preferably 1-2 min; after the mold is cooled, quickly removing the helium gas channel, and connecting the pouring gate with the argon atmosphere protection to the intermediate frequency induction furnace and the mold;

s4.2, casting stage: the intermediate frequency induction furnace is inclined to the side of the casting channel, and the inclination angle is 10-120 degrees. Because the density of the slag is lower than that of the molten steel, a small amount of slag preferentially enters the casting mold under the action of gravity, and a layer of slag crust is rapidly formed under the action of composite centrifugal force to cover the inner wall of the casting mold; then, the mixture of the slag and the molten steel enters a mold, under the action of the composite centrifugal force, the centrifugal speed of the molten steel is higher than that of the slag, the slag is gathered towards the center of a casting mold to form a temperature field with high intermediate temperature and low edge temperature, and a casting is favorably solidified from the outer edge to the center;

s4.3, finishing stage: after the casting process is finished, the centrifugal machine continues to work for 10-15 min to ensure that the molten steel and the molten slag are completely solidified, and then the centrifugal machine is closed; and after the casting mold is cooled, taking out the hollow casting, knocking out the surface slag layer, and preparing the H13 hollow casting with refined liquated carbide.

Preferably, the flow of argon in the pouring channel of the vertical centrifugal machine is 10-20 L.min^-1。

Preferably, the rotating speed of the composite centrifugal field is 1000-1300 r.min^-1。

Preferably, the chemical composition range of the prepared H13 hollow casting meets the composition range specification for H13 casting in the NADCA #207-2003 standard.

Optionally, the composite centrifugal field rotating speed of the vertical centrifuge can be 1000 r-min^-1、1150r·min^-1、1300r·min^-1And 1000 to 1300 r.min^-1Any value in between; the flow rate of the helium gas in the air passage of the vertical centrifugal machine can be 20L-min^-1、60L·min^-1、100L·min^-1And 20 to 100 L.min^-1The aeration time can be any value between 1min, 1.5min, 2min and 1-2 min; the flow of argon in the pouring channel of the vertical centrifuge can be 10 L.min^-1、15L·min^-1、20L·min^-1And 10 to 20 L.min^-1Any value in between.

By the centrifugal liquid slag casting process, the segregation degree of interdendritic elements in the H13 hollow casting is reduced by 9-15%; the solid phase rate of the generated liquated carbide is increased by 5-10%, and the particle size is reduced by 10-20%.

Example 1

The embodiment provides a method for casting and refining liquated carbides in H13 hollow castings by liquid slag in a composite centrifugal field, wherein a vacuum induction cast ingot with the length of 300mm and the diameter of 100mm is obtained by adopting hollow induction smelting, and the oxygen content of the cast ingot is 58 ppm; smelting a vacuum induction cast ingot in a medium-frequency induction furnace, wherein the smelting slag system comprises the following components: CaO 25%, SiO₂14 percent of MgO26 percent and the balance of CaF₂Oxygen of medium frequency induction molten steelThe content was 36 ppm; molten steel and smelting slag in the medium-frequency induction furnace are poured into a vertical centrifuge die, and the rotating speed of the centrifuge is as follows: 1000 r.min^-1Keeping for 1.0min +1100 r.min^-1Keeping for 5.5min +1200 r.min^-1Keeping the temperature for 8.5min, and obtaining a liquid slag casting H13 hollow casting under the action of the composite centrifugal field; FIG. 1 shows the morphology of typical liquated carbides in a composite centrifugal field liquid slag cast H13 hollow casting.

Example 2

The embodiment provides a method for casting and refining liquated carbides in H13 hollow castings by liquid slag in a composite centrifugal field, wherein vacuum induction melting is adopted to obtain vacuum induction cast ingots with the length of 350mm and the diameter of 90mm, and the oxygen content of the cast ingots is 65 ppm; smelting a vacuum induction cast ingot in a medium-frequency induction furnace, wherein the smelting slag system comprises the following components: CaO 28%, SiO₂12%, MgO 25%, the rest is CaF₂The oxygen content of the medium-frequency induction molten steel is 38 ppm; molten steel and smelting slag in the medium-frequency induction furnace are poured into a vertical centrifuge die, and the rotating speed of the centrifuge is as follows: 1000 r.min^-1Keeping for 1.0min +1150 r.min^-1Keeping for 6.5min +1300 r.min^-1Keeping the temperature for 8.0min, and obtaining a liquid slag casting H13 hollow casting under the action of the composite centrifugal field; FIG. 2 shows the morphology of typical liquated carbides in a composite centrifugal field liquid slag cast H13 hollow casting.

Comparative example 1

Unlike examples 1 and 2, the centrifuge rotation speed in comparative example 1 was constant at 1000 r.min^-1。

Obtaining a vacuum induction cast ingot with the length of 350mm and the diameter of 90mm by adopting hollow induction melting, wherein the oxygen content of the cast ingot is 63 ppm; smelting a vacuum induction cast ingot in a medium-frequency induction furnace, wherein the smelting slag system comprises the following components: CaO 27%, SiO₂12%, MgO 26%, the rest is CaF₂The oxygen content of the medium-frequency induction molten steel is 36 ppm; pouring molten steel and smelting slag in the medium-frequency induction furnace into a vertical centrifuge die, wherein the rotating speed of the centrifuge is constant and is 1000 r.min^-1Obtaining a liquid slag casting H13 hollow casting under the action of the centrifugal force field; FIG. 3 is a graph of the morphology of typical liquated carbides in a centrifugal field liquid slag cast H13 hollow casting.

As shown in fig. 1, 2 and 3, when the morphology of the carbides in the H13 hollow castings obtained in examples 1 and 2 and comparative example 1 was compared, it was found that the carbides in the H13 hollow castings were significantly refined by the composite centrifugal field.

FIG. 4 is a graph showing the width of the interdendritic element-rich region in H13 hollow castings obtained in examples 1 and 2 and comparative example 1. As can be seen from fig. 4, as the rotational speed of the centrifugal field increases, the width of the interdendritic enrichment region decreases. The increase of the rotating speed of the centrifugal force field enhances the stirring effect of centrifugal force on molten steel, increases the destructive power on dendritic crystals, and is beneficial to the full flow of a liquid phase with high solute element concentration in the solidification process, thereby reducing the width of a solute element enrichment area in the liquid phase.

FIG. 5 shows segregation ratios of interdendritic elements in H13 hollow castings obtained in examples 1 and 2 and comparative example 1. As can be seen from fig. 5, increasing the rotational speed of the centrifugal field is beneficial to reducing the segregation degree of interdendritic elements. The increase of the rotating speed of the centrifugal force field is beneficial to enhancing the forced convection of the melt, breaking the dendritic crystal structure, accelerating the movement speed of the enriched elements at the solidification front and promoting the homogenization of the soluble elements in the melt.

FIG. 6 is a graph showing the size distribution of the liquated carbides in the H13 hollow castings obtained in example 1, example 2 and comparative example 1. As can be seen from FIG. 6, the size of the liquated carbide particles is concentrated and distributed between 1 to 10 μm. For the centrifugal force field liquid slag casting H13 hollow casting with constant rotating speed, the number of liquated carbides is the largest, and the overall size of the liquated carbides is larger than that of the composite centrifugal field liquid slag casting H13 hollow casting. The liquid slag casting of the composite centrifugal field can effectively reduce the width of an interdendritic element enrichment region and the interdendritic element segregation ratio, thereby being beneficial to refining the liquated carbide in the H13 hollow casting.

Fig. 7 is a photograph showing no liquated carbides at the outer edge of a helium cooled mold casting and fig. 8 is a photograph showing no liquated carbides at the outer edge of a helium cooled mold casting. As can be seen from a comparison of FIGS. 7 and 8, the helium gas cooling of the mold and the runner according to the present invention further improves the distribution of the liquated carbides that refine the edges of the casting, thereby improving the overall quality of the casting.

The method comprises the steps of carrying out vacuum induction melting on raw materials to obtain an induction melting ingot; the induction smelting cast ingot is used as a base material after surface treatment, smelting is carried out in a medium-frequency induction furnace, and a layer of smelting slag covers the upper part of the molten steel in the smelting process; after the smelting of the medium-frequency induction furnace is finished, molten steel and slag liquid are poured into a vertical centrifuge with a mold, the vertical centrifuge rotates at different rotating speeds at room temperature to generate a composite centrifugal field, the segregation degree of elements among dendrites of the cast ingot is reduced, and the generation solid phase rate of the liquated carbide in the cast ingot is increased, so that the effect of refining the size of the liquated carbide in the H13 hollow casting is achieved.

While several embodiments of the present invention have been presented herein, it will be appreciated by those skilled in the art that changes may be made to the embodiments herein without departing from the spirit of the invention. The above examples are merely illustrative and should not be taken as limiting the scope of the invention.