Electroslag ingot capable of replacing forged ingot and smelting method

Abstract

The present application relates to a kind of smelting method of electric slag ingot that can be replaced with forging, comprising the following steps: preparation of chuck: continuous casting billet annealing, after annealing is completed, into chuck, chuck is turned into small head end and big head end of different diameter at two ends with lathe, and process a groove at the top of small head end at preset position, process more than 2 annular grooves at the top of big head end at preset position;Electric slag ingot and the assembly of chuck: during the smelting process of electric slag ingot, when smelting power-off, the chuck of step 1 is hoisted to the top of crystallizer, when chuck big head end is at a certain distance from the mouth of crystallizer, chuck is centered with electric slag ingot, then chuck big head end is inserted into slag liquid, electric slag ingot with chuck is cooled in crystallizer mode, after mold cooling is completed, slow cooling is carried out.The present application can withstand 720 cycle pipe mill rolling into bar rolling stress (maximum can reach 2056.1KN), avoid the fracture of chuck and electric slag ingot connection during rolling process, and the present application has good feasibility of popularization and application.

Description

Technical Field

[0001] This invention relates to the field of electroslag remelting technology, and more particularly to an electroslag ingot and smelting method that can replace forging with rolling. Background Technology

[0002] "Rolling instead of forging" can greatly improve production efficiency and reduce production costs. It allows for better control of the temperature, dimensional accuracy, surface quality, internal structure and mechanical properties of rolled parts, ensuring the advanced nature, flexibility and economic applicability of production technology.

[0003] "Rolling instead of forging" is particularly suitable for the rolling production of special alloys. Traditional special alloy production processes suffer from problems such as high hot working costs, low yield, and poor surface quality. The "rolling instead of forging" process effectively solves technical challenges such as high alloy deformation resistance, poor hot deformation plasticity, and narrow hot working temperature range.

[0004] In China, electroslag ingots with a diameter of ∮500-∮700mm that can be directly rolled into bars using rolling mills are typically produced by machining a circular hole of a certain depth (150-250mm) at one end of the ingot, inserting a chuck of a specific shape into the hole, and then connecting the two together using welding. Electroslag ingots produced in this way are prone to breakage of the chuck and the ingot during the rolling process, due to the rolling stress, which can reach up to 2056.1KN, resulting in a high number of scraps. Summary of the Invention

[0005] In response to the aforementioned technical problems, an electroslag ingot that can be produced by rolling instead of forging and a smelting method are provided.

[0006] The technical means employed in this invention are as follows:

[0007] A method for smelting electroslag ingots that can be produced by rolling instead of forging includes the following steps:

[0008] Step 1, preparation of the chuck: Anneal the continuous casting billet. After annealing, process it into a chuck. Use a lathe to turn the chuck into a small end and a large end with different diameters at both ends. Process a groove at a preset position from the top of the small end and process more than two annular grooves at a preset position from the top of the large end.

[0009] Step 2, Assembly of the electroslag ingot and the clamp: During the smelting process of the electroslag ingot, when the smelting power is cut off, the clamp processed in Step 1 is hoisted above the crystallizer. When the large end of the clamp is a certain distance from the crystallizer opening, the clamp is aligned with the electroslag ingot. Then the large end of the clamp is inserted into the slag liquid. The electroslag ingot with the clamp is molded and cooled in the crystallizer. After the mold cooling is completed, it is slowly cooled.

[0010] Further, in step 1, the annealing process includes the following steps: heating from room temperature to 520℃-570℃, then heating for another 4-5 hours at a rate of ≤50℃ / h, heating to 770℃-780℃, holding at that temperature for 5 hours, cooling at a rate of ≤30℃ / h, and removing from the furnace when the temperature drops below 200℃.

[0011] Further, in step 1, after annealing, a chuck with a length of 800-900mm is machined. The chuck is then machined on a lathe to have a small end length of 300-301mm and a diameter of ∮230-231mm. A groove with a depth of 30-31mm, a width of 115-116mm, and a length of 200-201mm is machined at a distance of 110-111mm from the top of the small end. The large end has a length of 400-600mm and a diameter of ∮280-282mm. Two or more annular grooves with a width of 20-22mm and a depth of 20-22mm are machined within a range of 90-100mm from the end face of the large end.

[0012] Furthermore, in step 2, the electroslag ingot is smelted according to the normal production process. During the smelting process of the electroslag ingot, 5-10 minutes before the power outage for feeding, the clamp is hoisted with a steel wire rope from a crane for standby.

[0013] Furthermore, in step 2, if the smelting power is interrupted, the extension arm must be unscrewed immediately, and the clamp head must be quickly hoisted above the crystallizer. This invention requires that the operation time for hoisting and aligning the clamp head be ≤5 minutes. When the clamp head is hoisted above the crystallizer, and the large end of the clamp head is 20-50mm away from the crystallizer opening, the clamp head is aligned with the electroslag ingot.

[0014] Furthermore, in step 2, after the clamp head is aligned with the electroslag ingot, the center deviation of the clamp head connection should be ≤10mm, and the clamp head should be connected at a perpendicular 90° angle.

[0015] Furthermore, in step 2, the chuck is inserted into the molten steel to a depth of 90-120mm.

[0016] Furthermore, in step 2, the crane vertically lifts the chuck until the electroslag ingot molten steel solidifies and cools, and the chuck no longer shifts. Then, the crane removes the wire rope and moves it away.

[0017] Furthermore, in step 2, the electroslag ingot is mold-cooled inside the crystallizer for 60-75 minutes.

[0018] This invention also claims protection for electroslag ingots made based on the above-described smelting method.

[0019] Compared with existing technologies, this invention has the following advantages: The ∮450-∮700mm diameter electroslag ingot with an insert clamp is inserted into the uncooled electroslag molten steel during the later stages of the electroslag smelting process, allowing the clamp and the ingot to be firmly connected. The operation is simple, easy to implement, and has low manufacturing costs. It can be rolled into ∮350mm bars or ∮350mm billets (for continuous rolling mills) using a 720-cycle tube rolling mill, and can withstand the rolling stress of 720-cycle tube rolling into bars (up to 2056.1KN), preventing breakage at the connection between the clamp and the electroslag ingot during rolling. In a production run of 100 pieces, no breakage occurred, and the ingot body was free of cracks, sand holes, pits, pores, and other defects, achieving a 100% quality pass rate. Therefore, the feasibility for widespread application of this invention is good.

[0020] The electroslag ingots with a ∮450-∮700mm diameter and a clamping head produced using this invention can be rolled into ∮350mm bars using 720 or other cycle tube rolling mills. This achieves the goal of replacing forging with rolling, shortening production time and saving costs. Using the electroslag ingots of this invention on 720 or other cycle tube rolling mills significantly improves the yield and significantly reduces the scrap rate. Annual benefits are estimated at over 1 million RMB. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the smelting process of the present invention.

[0023] In the diagram: 1. Card head; 2. Slag liquid; 3. Molten steel; 4. Electroslag ingot. Detailed Implementation

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0027] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of components and steps set forth in these embodiments do not limit the scope of the invention. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0028] Example 1

[0029] like Figure 1 As shown, a 3.04t, 2080mm, P91 electroslag ingot with a ∮500mm diameter and a clamping head, produced using this invention, was rolled into a ∮350mm round bar using a 720-cycle tube rolling mill. The quality was satisfactory; the "rolling instead of forging" process resulted in no breakage, and the ingot body was free of cracks, sand holes, pits, porosity, or other defects. The implementation plan is as follows:

[0030] The 20G continuously cast billet is first annealed. The annealing process requires heating from room temperature (20℃) to 520℃ at a rate of 100℃ / h. After 5 hours, it reaches 520℃, and then the temperature is increased for another 5 hours at a rate of 50℃ / h, until it reaches 770℃. After holding at this temperature for 5 hours, the temperature is lowered at a rate of 30℃ / h. The billet is then removed from the furnace when the temperature drops to 200℃.

[0031] After annealing, a chuck with a length of 800mm is machined from a 20G steel continuous casting billet. The chuck is then machined on a lathe to have a small end length of 300mm and a diameter of ∮230mm. A groove with a depth of 30mm, a width of 116mm, and a length of 200mm is machined 110mm from the top of the small end. The large end is 500mm long and has a diameter of ∮280mm. Two annular grooves with a width of 20mm and a depth of 20mm are machined within 80mm of the large end face.

[0032] By creating a groove on the clamp head, the clamp head 1 and the electroslag ingot 4 are more tightly connected after the clamp head is inserted into the electroslag ingot and cooled. The electroslag ingot with the clamp head is less likely to break during the "rolling instead of forging" rolling process.

[0033] The electroslag ingot is produced in 500mm diameter P91 form using a binary slag system of CaF2:Al2O3 = 7:3, with a slag quantity of 100 kg. The smelting current is 12800-13500A, and the smelting voltage is 76-80V. After normal smelting of the electroslag ingot, 5 minutes before the power outage for feeding, the clamping head is hoisted using a gantry crane with a wire rope for standby. Upon power outage, the extension arm must be immediately rotated, and the clamping head quickly hoisted above the crystallizer. When the lower end of the clamping head is 20mm from the crystallizer opening, it is slowly aligned with the electroslag ingot. The clamping and alignment operation takes 2 minutes.

[0034] The depth of the slag liquid is measured to be 350mm. The large end of the chuck is inserted into the slag liquid 2 and the steel liquid 3 to a total depth of 450mm.

[0035] The overhead crane vertically lifts the chuck until the electroslag ingot molten steel solidifies and cools without shifting. Only then can the overhead crane remove the wire rope and move it away. Simultaneously, the electroslag ingot undergoes die cooling inside the crystallizer. The die cooling time is 70 minutes for a ∮500mm ingot. After die cooling is complete, slow cooling is performed.

[0036] The center deviation between the clamp and the electroslag ingot is 2mm; the insertion depth of the clamp into the steel ingot is 80mm. The clamp is connected perpendicularly at 90°. Ensure that the total length of the clamp on the finished product is 720mm, of which the small end is 300mm and the large end is 420mm.

[0037] Example 2

[0038] One 4.4t, 2550mm, P92 electroslag ingot with a ∮550mm diameter and a clamping head, produced using this invention, was rolled into a ∮350mm round bar using a 720-cycle tube rolling mill, and the quality was qualified.

[0039] The implementation plan is as follows:

[0040] The 20# continuously cast billet is first annealed. The annealing process requires the following steps: first, heat the billet from 25℃ to 550℃ at a rate of 150℃ / h for 3.5 hours, then heat it for another 4.5 hours at a rate of 50℃ / h, until it reaches 775℃. Hold the billet at this temperature for 5 hours, and then cool it down at a rate of 25℃ / h. The billet is then removed from the furnace when the temperature drops to 200℃.

[0041] After annealing, a chuck with a length of 850mm is machined from a 20# steel continuous casting billet. The chuck is then machined on a lathe to have a small end length of 300mm and a diameter of ∮230mm. A groove with a depth of 30mm, a width of 116mm, and a length of 200mm is added 110mm from the top of the small end. The large end is 550mm long and has a diameter of ∮280mm. Two annular grooves with a width of 20mm and a depth of 20mm are machined 60mm from the large end.

[0042] The electroslag ingot is produced using the P92 process with a ∮550mm ingot shape, employing a binary slag system of CaF2:Al2O3 = 7:3, with a slag quantity of 120 kg. The smelting current is 13200-14000A, and the smelting voltage is 78-83V. After normal smelting of the electroslag ingot, 6 minutes before the power outage for feeding, the chuck is hoisted up using a gantry crane with a wire rope for standby. Upon power outage, the extension arm must be immediately rotated, and the chuck quickly hoisted above the crystallizer. When the lower end of the chuck is 25mm from the crystallizer opening, the chuck is slowly aligned with the electroslag ingot. The chuck hoisting and alignment operation takes 3 minutes.

[0043] The depth of the slag liquid was measured to be 375mm. The total depth of the chuck tip inserted into the slag liquid and molten steel liquid was 465mm.

[0044] The overhead crane vertically lifts the chuck until the electroslag ingot molten steel solidifies and cools without shifting. Only then can the overhead crane remove the wire rope and move it away. Simultaneously, the electroslag ingot undergoes die cooling inside the crystallizer. The die cooling time is 75 minutes for a ∮550mm ingot. After die cooling is completed, it is slowly cooled according to the normal process.

[0045] The center deviation between the clamp and the electroslag ingot is 4mm; the insertion depth of the clamp into the steel ingot is 90mm. The clamp is connected perpendicularly at 90°. The total length of the clamp on the finished product is 760mm, of which the small end is 300mm and the large end is 460mm.

[0046] Example 3

[0047] This invention was used to produce one 700mm, 5t, 1900mm diameter P22 electroslag ingot with a clamp at the top. It was then processed into 350mm diameter round bars using a 720-cycle tube rolling mill, and the quality was satisfactory. The implementation plan is as follows:

[0048] The 20g continuously cast billet is first annealed. The annealing process requires the following steps: first, heat the billet from 20℃ to 520℃ at a rate of 50℃ / h for 10 hours, then heat it for another 5 hours at a rate of 50℃ / h, until it reaches 770℃. Hold the billet at this temperature for 5 hours, and then cool it down at a rate of 30℃ / h. The billet is then removed from the furnace when the temperature drops to 200℃.

[0049] After annealing, a chuck with a length of 800mm is machined from a 20g steel continuous casting billet. The chuck is then machined on a lathe to have a small end length of 300mm and a diameter of ∮230mm. A groove with a depth of 30mm, a width of 116mm, and a length of 200mm is machined at a distance of 110mm from the top of the small end. The large end is 500mm long and has a diameter of ∮280mm. Two annular grooves with a width of 20mm and a depth of 20mm are machined at a distance of 60mm from the large end face.

[0050] Electroslag ingots are produced using a ∮700mm P22 process, employing a binary slag system of CaF2:Al2O3 = 7:3, with a slag quantity of 160 kg. The smelting current is 15000-16000A, and the smelting voltage is 80-86V. After normal smelting of the electroslag ingots, 5 minutes before the power outage for feeding, the chuck is hoisted up using a gantry crane with a wire rope for standby. Upon power outage, the extension arm must be immediately rotated, and the chuck quickly hoisted above the crystallizer. When the lower end of the chuck is 20-50mm from the crystallizer opening, the chuck is slowly aligned with the electroslag ingot. The chuck hoisting and alignment operation takes 2 minutes.

[0051] The depth of the slag liquid was measured to be 450mm, and the total depth of the chuck inserted into the slag liquid and molten steel liquid was 550mm.

[0052] The overhead crane vertically lifts the chuck until the electroslag ingot molten steel solidifies and cools without shifting. Only then can the overhead crane remove the wire rope and move it away. Simultaneously, the electroslag ingot undergoes die cooling inside the crystallizer. The die cooling time is 75 minutes for a ∮700mm ingot. After die cooling is complete, it is slowly cooled according to the normal process.

[0053] The center deviation between the clamp and the electroslag ingot is 3mm; the insertion depth of the clamp into the steel ingot is 100mm. The clamp is connected perpendicularly at 90°. The total length of the clamp on the finished product is 710mm, of which the small end is 300mm and the large end is 410mm.

[0054] In a statistical analysis of 20 electroslag ingots produced using the "rolling instead of forging" method, 7 ingots experienced breakage of the clamp and the ingot itself, and 3 were scrapped due to cracks, resulting in a failure rate of 50%. In contrast, 100 ingots produced using this invention showed no breakage, no cracks, sand holes, pits, or pores in the ingot body, achieving a 100% quality pass rate.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for smelting electroslag ingots that can be produced by rolling instead of forging, characterized in that, Includes the following steps: Step 1, preparation of the chuck: Anneal the continuous casting billet. After annealing, process it into a chuck. Use a lathe to turn the chuck into a small end and a large end with different diameters at both ends. Process a groove at a preset position from the top of the small end and process more than two annular grooves at a preset position from the top of the large end. Step 2, Assembly of electroslag ingot and clamp: During the smelting process of electroslag ingot, when the smelting power is cut off, the clamp processed in Step 1 is hoisted above the crystallizer. When the large end of the clamp is a certain distance from the crystallizer opening, the clamp is aligned with the electroslag ingot. Then the large end of the clamp is inserted into the slag liquid. The electroslag ingot with the clamp is molded in the crystallizer and then slowly cooled after the mold cooling is completed. In step 1, the annealing process includes the following steps: heating from room temperature to 520℃-570℃, then heating for another 4-5 hours at a rate of ≤50℃ / h, heating to 770℃-780℃, holding at that temperature for 5 hours, cooling at a rate of ≤30℃ / h, and removing from the furnace when the temperature drops below 200℃. In step 1, after annealing, a chuck with a length of 800-900mm is machined. The chuck is then machined on a lathe to make the small end 300-301mm long and ∮230-231mm in diameter. A groove 30-31mm deep, 115-116mm wide, and 200-201mm long is machined 110-111mm from the top of the small end. The large end is 400-600mm long and ∮280-282mm in diameter. Two or more annular grooves 20-22mm wide and 20-22mm deep are machined within 90-100mm from the end face of the large end.

2. The smelting method for electroslag ingots that can be produced by rolling instead of forging according to claim 1, characterized in that, In step 2, during the smelting process of electroslag ingots, 5-10 minutes before the power outage for feeding, the clamp is hoisted with a steel wire rope from a crane and is ready for use.

3. The smelting method for electroslag ingots that can be produced by rolling instead of forging according to claim 1, characterized in that, In step 2, the clamp is hoisted above the crystallizer. When the lower end of the large end of the clamp is 20-50mm away from the crystallizer opening, the clamp is aligned with the electroslag ingot.

4. The smelting method for electroslag ingots that can be produced by rolling instead of forging according to claim 1, characterized in that, In step 2, after the clamp head is aligned with the electroslag ingot, the center deviation of the clamp head connection should be ≤10mm, and the clamp head should be connected at a 90° vertical angle.

5. The smelting method for electroslag ingots that can be produced by rolling instead of forging according to claim 1, characterized in that, In step 2, the clamp is inserted into the molten steel 80-120mm.

6. The smelting method for electroslag ingots that can be produced by rolling instead of forging according to claim 1, characterized in that, In step 2, the crane lifts the chuck vertically until the electroslag ingot steel solidifies and cools, and the chuck no longer shifts. Then, the crane removes the wire rope and moves it away.

7. The smelting method for electroslag ingots that can be produced by rolling instead of forging according to claim 1, characterized in that, In step 2, the electroslag ingot is mold-cooled inside the crystallizer for 60-75 minutes.

8. An electroslag ingot prepared according to any one of claims 1 to 7.

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