A multi-layer ingot mold casting method for high-silicon ferroalloy production

Abstract

The application provides a multilayer ingot mold casting method for high-silicon ferroalloy production and relates to the technical field of high-silicon ferroalloy production.The present casting method uses a rapid casting mode to cast a small amount of liquid high-silicon ferroalloy onto an ingot mold to form an alloy solid protective layer, and continues to cast liquid high-silicon ferroalloy on the protective layer to form 1-3 main alloy layers; the thickness of the main alloy layer is controlled to be 1-4 times that of the alloy solid protective layer, and the cooling temperature is controlled to be 25-60 DEG C / min; the solidified alloy is mechanically broken and demolded in a hot state to obtain high-silicon ferroalloy. The method prolongs the service life of the ingot mold, reduces the segregation of Si and other components in the product high-silicon ferroalloy, the segregation of Si components is 0.5-1%, and simultaneously reduces the generation of fine lines and the alloy powder rate, and the average powder rate is 6-7%.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high-silicon alloy production, in particular to the technical field of automatic casting of high-silicon ferroalloy, and specifically relates to a multilayer ingot mold casting method for high-silicon ferroalloy production. BACKGROUND

[0002] An alloy is a solid substance with metallic properties obtained by mixing and melting one metal with another metal or non-metal and then cooling and solidifying. There are many types of alloys, among which high-silicon content alloys are mainly used in the preparation of products such as spring steel, bearing steel, and combined steel, which require high precision, long service life, and low deformation rate. Silicon can significantly improve the performance of the alloy, but it also significantly reduces the process performance of the alloy, increasing the tendency of the alloy to form pores, shrinkage, and cracks, as well as the powder rate and the probability of product composition segregation, posing new challenges for alloy smelting and casting. During the production of high-silicon alloys, the liquid metal from the submerged arc furnace needs to be cast and cooled, and the casting and cooling process has a significant impact on the performance of the alloy product.

[0003] Currently, common casting methods in industry include cast iron ingot mold casting, alloy metal powder mold bed casting, pool casting, and water quenching method. Among them, cast iron ingot mold casting is the most common casting method in industry. In order to prevent the alloy from sticking to the mold, a release agent is usually sprayed on the surface of the moving or fixed ingot mold before casting. However, this method also has some disadvantages, such as: (1) short ingot mold life, high loss, and significant increase in industrial production cost, 50-150 yuan / ton of alloy; (2) use of release agent, which affects the quality of the alloy product; (3) low release efficiency and low degree of automation, affecting the effect of the alloy.

[0004] The method of making casting mold bed with alloy metal powder is simple, but due to the low thermal conductivity of the powder, the cooling is mainly through the radiation and convection cooling of the top, and the cooling speed is difficult to control, which is easy to cause segregation and impurity aggregation. In addition, the metal powder will stick to the metal, affecting the appearance quality of the product, and the powder mold bed is suitable for small-scale electric furnace production operation; the pool casting method is to cast the alloy layer by layer into the casting pool. Pool casting requires small casting thickness and can accelerate the alloy solidification. In industrial production, more than 15 layers are usually cast, and standby casting pools are provided for mutual conversion. However, the disadvantages of this casting method are: (1) the alloy cooling time is longer than other methods, and the product segregation is more serious; (2) the alloy casting thickness is small, and the lower product is repeatedly heated and cooled by the upper alloy, which significantly increases the internal fine lines of the alloy, and the product powder rate is higher than that of ingot mold casting; (3) the product quality is difficult to control, and the product is in one casting pool. Once the local quality does not meet the requirements, the overall quality will be affected. Water granulation (water quenching method) can control the casting of alloy into water, the alloy is dispersed, the high-speed heat transfer rate and small particle size of metal droplets are combined to provide the conditions for rapid solidification of the alloy and high-strength alloy. However, this method has the risk of explosion.

[0005] Chinese invention patent CN104372188B discloses a preparation method of high-silicon nickel-copper alloy casting. The method adopts vacuum induction furnace melting and casting into mother alloy ingot, and then melts the mother alloy ingot in the vacuum induction furnace and refines for 3-7 min at 1450-1550℃, and then cools to 1260-1320℃ for casting, to obtain a near-net-shape alloy casting. The solidification control process is: the initial cooling speed is 90-180℃ / s, the cooling speed is reduced to 0.01-0.1℃ / s when the casting temperature reaches 900-1100℃, and the alloy casting is naturally cooled to room temperature when the temperature is below 400℃, to obtain a high-silicon nickel-copper alloy casting. The casting process solves the problem of brittle fracture and internal cracks in high-silicon nickel-copper alloy casting by using the heat treatment method of segmented cooling, and improves the performance of the alloy.

[0006] In recent years, with the gradual scale of high-silicon alloy production, electric furnaces are developing towards large-scale, and the single casting capacity is greatly increased. In addition, the requirements for alloy quality are becoming more and more strict, and the demand for efficient and lean production in the production process is becoming more and more intense. Therefore, the casting method with higher efficiency, lower risk of ingot mold fracture, lower safety risk, longer service life of ingot mold, higher alloy product quality, lower powder rate and fewer cracks is attracting more and more attention. SUMMARY

[0007] The present application aims at the problems existing in the prior art, and provides a multi-layer ingot mold casting method for high-silicon ferroalloy production, which adopts a rapid casting mode to cast a small amount of liquid high-silicon ferroalloy on the ingot mold to form an alloy solid protective layer, and continues to cast the liquid high-silicon ferroalloy on the protective layer to form a main alloy layer; the cooling temperature is controlled to be 25-60 ℃ / min; and the solidified alloy is mechanically broken and demolded in a hot state. The method prolongs the service life of the ingot mold, reduces the segregation of components such as silicon in the product, and reduces the generation of fine lines and the alloy powder rate.

[0008] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0009] In one aspect, the present application provides a multi-layer ingot mold casting method for high-silicon ferroalloy production, comprising the following steps:

[0010] (1) casting liquid high-silicon ferroalloy on the ingot mold to form an alloy solid protective layer, and controlling the thickness of the alloy solid protective layer to be 5-30 mm;

[0011] (2) cooling the alloy solid protective layer to below 500-900 ℃ to solidify, and casting liquid high-silicon ferroalloy on the alloy solid protective layer to form a main alloy layer, and the thickness of each main alloy layer is 1-4 times the thickness of the alloy solid protective layer;

[0012] (3) controlling the cooling speed of the main alloy layer to be 25-60 ℃ / min to obtain a solidified alloy;

[0013] (4) mechanically breaking and demolding the solidified alloy in a hot state, controlling the hot breaking temperature to be 800-1100 ℃, cooling, and obtaining high-silicon ferroalloy.

[0014] Preferably, in steps (1) and (2), the temperature of the liquid high-silicon ferroalloy is 1450-1600 ℃.

[0015] Preferably, in step (1), the casting is performed in a rapid casting mode.

[0016] Preferably, in step (1), the thickness control is performed according to the principle of casting, cooling and solidification.

[0017] Preferably, in step (1), the thickness of the alloy solid protective layer is controlled to be 10-20 mm.

[0018] Preferably, in step (1), the temperature of the alloy solid protective layer is controlled to be 600-800 ℃.

[0019] Preferably, in step (1), the material of the alloy solid protective layer is consistent with that of the main alloy layer.

[0020] Preferably, in step (2), the alloy solid protective layer is cooled to 800℃.

[0021] Preferably, in step (2), the thickness of each main alloy layer is 2-3 times the thickness of the alloy solid protective layer.

[0022] More preferably, the thickness of each main alloy layer is 30-60mm.

[0023] Preferably, in step (2), the number of main alloy layers is 1-3.

[0024] Preferably, in step (3), the cooling rate of the main alloy layer is 35-45℃ / min.

[0025] Preferably, in step (3), the temperature of the solidified alloy is 800-1000℃.

[0026] Preferably, in step (3), the cooling rate can be controlled by forced cooling such as air cooling and / or water cooling.

[0027] Preferably, in step (4), the temperature of the hot-state breaking is 800-1000℃.

[0028] More preferably, the temperature of the hot-state breaking is 800-900℃.

[0029] Preferably, in step (4), the cooling is natural cooling.

[0030] In another aspect, the present application provides a high-silicon ferroalloy prepared by the above method.

[0031] Preferably, the segregation of Si component of the high-silicon ferroalloy is 0.5-1%, and the average powder rate is 6-7%.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] 1. The method of the present application protects the ingot mold by controlling the thickness and cooling temperature of the alloy protective layer, reducing the direct erosion and heat erosion of the liquid alloy on the ingot mold; and the alloy is mechanically broken and demolded in a hot state, which reduces the mechanical impact on the ingot mold, prolongs the service life of the ingot mold, reduces the cost, and reduces the need for secondary breaking of the alloy.

[0034] 2. The method of the present application slows down the thermal shock impact of the ingot mold by multi-layer casting of the main alloy layer, significantly reduces the risk of ingot mold fracture, improves production safety, and significantly prolongs the first mold of the ingot mold by 1.5-3 times.

[0035] 3. The method of the present application reduces product composition segregation and improves the quality of alloy products by controlling the thickness and number of layers of the main alloy layer.

[0036] 4. The method of the present application controls the cooling speed of the main alloy layer by forced cooling, suppresses the volume expansion reaction of the alloy, reduces the generation of fine lines and the alloy powder rate, and significantly improves economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 Figure 1 is a comparison chart of the grain size and internal fine lines of high-silicon alloy produced at different cooling speeds in Example 2 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0038] The following non-limiting examples can enable those of ordinary skill in the art to more fully understand the present application, but in no way limit the present application. The following content is merely an exemplary illustration of the scope of the present application, and those skilled in the art can make various changes and modifications to the application disclosed herein, which should also be within the scope of the present application.

[0039] The present application will be further described below in the form of specific examples. The various chemical reagents used in the examples of the present application are obtained through conventional commercial channels unless otherwise specified.

[0040] In the examples of the present application, the liquid high-silicon iron alloy raw material used mainly includes 65-98% silicon element and 2-35% iron element.

[0041] Example 1

[0042] The liquid high-silicon iron alloy is cast into an ingot mold to form an alloy solid protective layer with a layer thickness of about 20 mm; 2 layers of main alloy are continuously cast on the protective layer, the first layer of main alloy has a thickness of 40 mm, and the second layer of main alloy has a thickness of 60 mm; the cooling speed of the main alloy layer is controlled at about 35°C / min, and mechanical crushing and demolding are performed at a hot state of about 900°C. A high-silicon iron alloy is obtained, the alloy Si composition segregation is about 0.8%, the average powder rate is 6%, and the cast iron ingot mold life is about 12 months.

[0043] Example 2

[0044] The liquid high-silicon iron alloy is cast into an ingot mold to form an alloy solid protective layer with a layer thickness of about 10 mm; 1 layer of main alloy is continuously cast on the protective layer, and the main alloy layer has a thickness of 50 mm; the cooling speed of the main alloy layer is controlled at about 30°C / min, and mechanical crushing and demolding are performed at a hot state of about 800°C. A high-silicon iron alloy is obtained, the alloy Si composition segregation is about 0.5%, the average powder rate is 6.5%, and the cast iron ingot mold life is about 8 months.

[0045] Example 3

[0046] The liquid high-silicon ferroalloy is cast into the ingot mold to form an alloy solid protective layer with a thickness of about 20 mm; 3 layers of main alloy are continuously cast on the protective layer, the thickness of the first layer of main alloy is 40 mm, and the thickness of the second and third layers of main alloy is 60 mm respectively; the cooling speed of the main alloy layer is controlled at about 25 ℃ / min, and mechanical crushing and demolding are performed at a hot state of 1000 ℃. The high-silicon ferroalloy is obtained after natural cooling. The alloy Si component segregation is about 1%, the average powder rate is about 7%, and the service life of the cast iron ingot mold is about 14 months.

[0047] Example 4

[0048] The liquid high-silicon ferroalloy is cast into the ingot mold to form an alloy solid protective layer with a thickness of about 30 mm; 2 layers of main alloy are continuously cast on the protective layer, the thickness of the first layer of main alloy is 30 mm, and the thickness of the second layer of main alloy is 30 mm; the cooling speed of the main alloy layer is controlled at about 45 ℃ / min, and mechanical crushing and demolding are performed at a hot state of about 800 ℃. The high-silicon ferroalloy is obtained after natural cooling. The alloy Si component segregation is about 0.5%, the average powder rate is 6%, and the service life of the cast iron ingot mold is about 10 months.

[0049] Example 5

[0050] The liquid high-silicon ferroalloy is cast into the ingot mold to form an alloy solid protective layer with a thickness of about 25 mm; 3 layers of main alloy are continuously cast on the protective layer, the thickness of the first layer of main alloy is 25 mm, the thickness of the second layer of main alloy is 50 mm, and the thickness of the third layer of main alloy is 25 mm; the cooling speed of the main alloy layer is controlled at about 40 ℃ / min, and mechanical crushing and demolding are performed at a hot state of about 900 ℃. The high-silicon ferroalloy is obtained after natural cooling. The alloy Si component segregation is about 0.6%, the average powder rate is 6.5%, and the service life of the cast iron ingot mold is about 12 months.

[0051] Comparative Example 1

[0052] Comparative Example 1 adopts a casting method of pool casting, the number of single-pool casting layers is 20, and the single-layer casting thickness is 80 mm-110 mm; the alloy layer cooling speed is not controlled, and the alloy layer is naturally cooled through radiation and convection at the top; the crushing temperature is ≤300 ℃. The average alloy Si component segregation is about 3%, and the average powder rate is 12.5%.

[0053] Comparative Example 2

[0054] Comparative Example 2 adopts single-layer casting of a fixed combined ingot mold, and the casting thickness is 60 mm-80 mm; the alloy layer cooling speed is not controlled, and the alloy layer is naturally cooled through convection at the upper part of the ingot mold and heat conduction at the lower part; the crushing and demolding temperature is 600-800 ℃. The average alloy Si component segregation is about 1%, and the average powder rate is 7.5%. The average service life of the ingot mold is 6 months.

[0055] Comparative Example 3

[0056] Comparative Example 3 uses a casting machine to move a single ingot mold to cast a single layer, with a casting thickness of 80 mm, a breaking and demolding temperature of about 900°C, an average alloy Si component segregation of about 1%, an average powder rate of about 7.5%, and a cast iron ingot mold service life of 1-3 months.

[0057] Comparative Example 4

[0058] Unlike Example 1, the second layer of main alloy has a thickness of 160 mm.

[0059] The remaining steps and parameters are the same as in Example 1. A high-silicon ferroalloy is obtained, with an alloy Si component segregation of about 1%, an average powder rate of 9%, and a cast iron ingot mold service life of about 3 months.

[0060] Casting the main alloy layer causes secondary melting of the alloy protective layer and the first layer of main alloy, which cannot protect the ingot mold, and uneven melting can cause a decrease in product quality.

[0061] Comparative Example 5

[0062] Unlike Example 1, the main alloy has 5 layers: the first layer of main alloy has a thickness of 40 mm, the second layer of main alloy has a thickness of 60 mm, the third layer of main alloy has a thickness of 60 mm, the fourth layer of main alloy has a thickness of 40 mm, and the fifth layer of main alloy has a thickness of 40 mm.

[0063] The remaining steps and parameters are the same as in Example 1.

[0064] A high-silicon ferroalloy is obtained, with an alloy Si component segregation of about 1.5%, an average powder rate of 9%, and a cast iron ingot mold service life of about 14 months.

[0065] Comparative Example 6

[0066] Unlike Example 1, the cooling speed of the main alloy layer is not controlled by forced cooling. In this comparative example, the cooling of the main alloy layer is natural slow cooling.

[0067] The remaining steps and parameters are the same as in Example 1.

[0068] A high-silicon ferroalloy is obtained, with an alloy Si component segregation of about 1.5%, an average powder rate of 11%, and a cast iron ingot mold service life of about 12 months. Finally, it should be noted that the above content is only used to illustrate the technical solutions of the present application, and is not a limitation on the protection scope of the present application. Simple modifications or equivalent replacements of the technical solutions of the present application made by ordinary technical personnel in the art do not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A multi-layer ingot casting method for the production of high-silicon ferroalloys, characterized in that, Includes the following steps: (1) The liquid high silicon iron alloy is cast onto the ingot mold to form an alloy solid protective layer, and the thickness of the alloy solid protective layer is controlled at 5-30mm; (2) The alloy solid protective layer is cooled to below 500-900℃ and solidified. Liquid high silicon iron alloy is cast onto the alloy solid protective layer to form the main alloy layer. The thickness of each main alloy layer is 1-4 times the thickness of the alloy solid protective layer. (3) Control the cooling rate of the main alloy layer to 25-60℃ / min to obtain a solidified alloy; (4) The solidified alloy is cooled to a hot state and mechanically crushed and demolded. The temperature of mechanical crushing and demolding in the hot state is controlled at 800-1100℃. After cooling, a high silicon iron alloy is obtained.

2. The method according to claim 1, characterized in that, In steps (1) and (2), the temperature of the liquid high-silicon iron alloy is 1450-1600℃.

3. The method according to claim 1, characterized in that, In step (1), the thickness of the alloy solid protective layer is controlled at 10-20 mm.

4. The method according to claim 1, characterized in that, In step (1), the temperature of the alloy solid protective layer is controlled at 600-800℃; the material of the alloy solid protective layer is the same as that of the main alloy layer; the casting is carried out by rapid casting to achieve immediate casting, cooling and solidification.

5. The method according to claim 1, characterized in that, In step (2), the thickness of each main alloy layer is 2-3 times the thickness of the alloy solid protective layer.

6. The method according to claim 5, characterized in that, The thickness of each main alloy layer is 30-60 mm.

7. The method according to claim 1, characterized in that, In step (2), the number of main alloy layers is 1-3.

8. The method according to claim 1, characterized in that, In step (3), the cooling rate of the main alloy layer is 35-45℃ / min.

9. The method according to claim 1, characterized in that, In step (4), the temperature of mechanical crushing and demolding under hot conditions is controlled at 800-1000℃.

10. The high-silicon iron alloy prepared by the method according to any one of claims 1-9; wherein the Si segregation of the high-silicon iron alloy is 0.5-1%, and the average powder yield is 6-7%.

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