Forging method for improving annealing structure of H13 type round steel
By performing high-temperature diffusion on H13 mold steel, upsetting by hydraulic press and temperature-controlled forging by diameter forging machine, and adopting specific heat treatment methods, the problem of unqualified annealing structure of H13 mold steel is solved, and the pass rate of annealing structure has been significantly improved.
Patent Information
- Application Number
- CN202411932465.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-26
- Publication Date
- 2025-03-28
AI Technical Summary
The annealed structure of H13 mold steel often fails, resulting in increased production costs and extended production cycles. It is urgent to find a production method to improve the annealed structure of H13 round steel to improve the passing rate of annealed structure.
The steel ingot is treated with high-temperature diffusion heating specifications, and then upset on the hydraulic press and draw the length or directly draw the length, and temperature controlled forging is performed in the diameter forging machine. After forging, the heat treatment adopts "high temperature normalized + isothermal spherical annealing" or "isothermal spherical annealing" is selected when the specifications of Φ80 to Φ350.
This method significantly improves the annealed structure of H13 round steel, and the pass rate of annealed structure reaches more than 99%, meeting the detection requirements of NADCA#207 standard.
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Figure CN119710177A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of forging in the process control of steel material equipment manufacturing, and specifically relates to a forging method for improving the annealing structure of H13 round steel, which can significantly improve the annealing structure of H13 round steel and meet the annealing structure qualification rate of more than 99%. According to the NADCA#207 standard, AS1-AS9 grades are qualified. Background Art
[0002] H13 die steel is a high-performance hot-working die steel, widely used in the manufacture of various molds. During use, in order to ensure that the mold is not easy to crack and increase its service life, the annealing structure becomes a very critical indicator. The ideal annealing structure has no network and chain carbides, and the carbides are spherical particles dispersed on the ferrite matrix. The better the annealing structure rating, the more uniform the carbide distribution, the less likely the mold will cause stress concentration and cracking during use, and the longer the service life.
[0003] In actual production, the annealing structure of H13 die steel often fails to meet the standards, and in severe cases, the annealing structure is even 100% unqualified. The unqualified structure must be reheat treated, which not only increases the gas cost, but also prolongs the production cycle. Therefore, it is urgent to find a production method to improve the annealing structure of H13 round steel, so as to increase the qualified rate of annealing structure. Summary of the invention
[0004] The object of the present invention is to overcome the shortcomings of the prior art and provide a forging method for improving the annealing structure of H13 round steel. The method performs high-temperature diffusion on the steel ingot, performs forging by a temperature control method, and adopts "high-temperature normalizing + isothermal spheroidizing annealing" or "isothermal spheroidizing annealing" for the post-forging heat treatment when the specification is Φ80-Φ350, which can significantly improve the annealing structure of H13 round steel.
[0005] The present invention is achieved through the following technical solutions: A forging method for improving the annealing structure of H13 round steel, wherein the steel ingot is diffused at high temperature → roughened on a hydraulic press and then drawn or directly drawn → temperature-controlled forging on a radial forging machine → heat treatment after forging. The specific forging steps are as follows: Step 1), heating: the steel ingot is kept at 450±10℃ for 3-7h, then heated to 850±10℃ at ≤60℃ / h for 3-7h, then heated to 1250-1280±10℃ at ≤120℃ / h for high temperature diffusion, the high temperature diffusion time is calculated as 2.5h-3h / 100mm according to the cross section of the steel ingot, then cooled to 1230±10℃ and taken out of the furnace; Step 2), after the steel ingot is taken out of the furnace, it is upset on the hydraulic press and then stretched or directly stretched. If the stretching-forging ratio is less than 7, it is necessary to increase the upsetting, and the upsetting pressure is 50% to 60%; the upsetting adopts the upper and lower flat anvils, stretches to four sides and inverts eight sides, and the size needs to meet the feeding of the radial forging machine, cuts off the riser, and then does not return to the furnace, and directly goes to the radial forging machine for forging; Step 3), forging and forming in a radial forging machine under temperature control; Step 4) Post-forging heat treatment adopts "high temperature normalizing + isothermal spheroidizing annealing" or "isothermal spheroidizing annealing" when the specification is Φ80~Φ350.
[0006] In step 1), high temperature diffusion can effectively improve the segregation and liquid precipitation inside the original steel ingot, make the composition uniform, dissolve the coarse liquid precipitation carbides, and finally improve the annealing structure of the finished forging. After high temperature diffusion, the temperature is lowered to 1230±10℃ and the temperature is lowered to prevent the coarse grain of the forging.
[0007] In step 2), it should be noted that at least 20% of the deformation should be reserved for the last fire of the hydraulic press to prevent coarse grains; the purpose of "cutting off the riser" is to greatly shorten the length of the discarded material at the riser end of the finished forging, so that the good material position can be closer to the outside and closer to the fan, and the heat dissipation can be faster, thereby increasing the cooling intensity of the good material position, reducing the precipitation of network or chain carbides, and improving the annealing structure; after the last fire of the hydraulic press is completed, it is not allowed to return to the furnace, and step 3) is carried out directly, the purpose is to cooperate with step 3) to reduce the temperature during forging.
[0008] In step 3), the forging is performed in a radial forging machine under temperature control. The specific requirements are: before each forging, the material is dried to a temperature of 750-800℃ at the highest point on the surface; during each forging, only one-side pulling is allowed, and the empty pass is returned; the pulling speed is controlled to be ≤3m / min, the pressing amount is between 40-70mm, and the final forging temperature is guaranteed to be between 750-850℃.
[0009] The purpose of temperature-controlled forging is: 1. Lowering the temperature during forging can refine the grains of forgings. Finer grains and more grain boundaries will prevent carbides from forming a network or chain, making the annealing structure better and improving the annealing structure qualification rate. 2. In the temperature range of temperature-controlled forging, some carbides have been precipitated. After forging, the precipitated carbides can be broken and distributed more evenly, which can also make the annealing structure better and improve the annealing structure qualification rate.
[0010] In step 4), the post-forging heat treatment adopts "high temperature normalizing + isothermal spheroidizing annealing", which can make the network, chain carbide or larger carbide particles re-dissolve and make them evenly distributed in spherical shape, which has a good effect of improving the annealing structure. The normalizing temperature is 1000-1050℃, and the isothermal spheroidizing temperatures are 850-880℃ and 740-760℃ respectively. Different from the traditional "high temperature normalizing + isothermal spheroidizing annealing" heat treatment method, the cooling method after forging and normalizing in this heat treatment method is: ≥Φ400mm specifications adopt "first water cooling, then air cooling to 250-300℃ before entering the furnace", and Φ80-Φ400 specifications adopt "first mist cooling to 300-350℃, then air cooling to 200-250℃ before entering the furnace". By continuing to air cool the forgings to lower the furnace temperature, sufficient cooling intensity can be ensured to reduce the precipitation of network or chain carbides, and a certain grain refinement effect can be achieved, which can ultimately improve the annealing structure.
[0011] In step 4), the post-forging heat treatment or "isothermal spheroidizing annealing" is selected for the specifications of Φ80~Φ350, and the isothermal spheroidizing temperatures are 850~880℃ and 740~760℃ respectively. Canceling normalizing can reduce production costs and cycles. At the same time, under this forging method, the annealing organization qualification rate can be guaranteed to be above 99%.
[0012] The present invention has the following beneficial effects: The present invention uses a special heating specification to diffuse the steel ingot at high temperature, adopts a special forging method of "upsetting on a hydraulic press and then drawing or directly drawing → temperature-controlled forging on a diameter forging machine" for forging, and adopts "high-temperature normalizing + isothermal spheroidizing annealing" for post-forging heat treatment, or "isothermal spheroidizing annealing" when the specification is Φ80-Φ350. This forging method can significantly improve the annealing structure of H13 round steel. According to the NADCA#207 standard test, AS1-AS9 grades are qualified, which can meet the annealing structure qualification rate of more than 99%. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 This is the heating specification diagram of H13 round steel before forging of the present invention.
[0014] Figure 2~Figure 8 It is a schematic diagram of the forging deformation of H13 round steel of the present invention.
[0015] in Figure 2 It is a schematic diagram of the structure of the steel ingot before upsetting on the upper flat plate and lower platform; Figure 3 It is a schematic diagram of the structure of the steel ingot after being upset on the upper flat plate and the lower platform; Figure 4 It is a schematic diagram of the structure of the roughened blank being stretched on the upper and lower flat anvils; Figure 5 It is a schematic diagram of the structure in which the blank is stretched to a square shape on the upper and lower flat anvils; Figure 6It is a schematic diagram of the structure in which the billet is stretched to four sides and then tilted to eight sides, in preparation for forging on the upper diameter forging machine; Figure 7 This is a schematic diagram of the forging process of a radial forging machine, where numbers 6, 7, 8, and 9 are the four hammers of the radial forging machine, and temperature-controlled forging is performed in each pass; Figure 8 This is a schematic diagram of the finished forgings forged by a radial forging machine.
[0016] Fig. 9 This is a picture of the annealing structure detection of H13 round steel of the present invention, and the illustrated structure result is AS3 grade. DETAILED DESCRIPTION
[0017] like Figure 2~Figure 8 As shown, in the forging deformation schematic diagram of the present invention, the section line portion of the blank 3 represents the riser end, and the following diagrams are the same.
[0018] The implementation of the technical solution of the present invention mainly utilizes special heating specifications to diffuse the steel ingot at high temperature, and then forges it through a temperature-controlled forging method after the high-temperature diffusion. After forging, post-forging heat treatment, surface and dimensional inspection, ultrasonic flaw detection, sawing and cutting, and physical and chemical testing are performed.
[0019] The specific production process of a forging method for improving the annealing structure of H13 round steel is as follows: The steel ingot diffuses at high temperature → is stretched after upsetting on a hydraulic press or is stretched directly → is forged by a temperature-controlled forging machine → is heat treated after forging → is inspected for surface and dimensions → is ultrasonically tested → is sawn → is physically and chemically tested → is delivered.
[0020] Forging Example 1: Take the electroslag ingot forging of Φ360 H13 round steel as an example. Figure 2 ), the electroslag ingot weighs 6 tons, has a diameter of Φ750mm and a height of approximately 1730mm.
[0021] The specific steps of forging are as follows: Step 1), the electroslag ingot is kept at 450±10℃ for 4h, then heated to 850±10℃ at ≤60℃ / h for 4h, and then heated to 1250±10℃ at ≤120℃ / h for high temperature diffusion for 20h. High temperature diffusion can effectively improve the segregation and liquid precipitation inside the original steel ingot, make the composition uniform, dissolve the coarse liquid precipitation carbides, and finally improve the annealing structure of the finished forging. After high temperature diffusion, the ingot is cooled to 1230±10℃ and taken out of the furnace. Cooling is beneficial to prevent coarse grains in the forgings; Step 2) The calculated drawing-forging ratio of 4.3 is less than 7, so it is necessary to increase the upsetting. After the electroslag ingot (also called billet, No. 3) is taken out of the furnace, the upper plate (No. 1) and the lower platform (No. 2) are used on the hydraulic press to upset from 1730mm to a height of 800mm, and the upsetting reduction is 50% to 60%. Figure 2 and Figure 3After upsetting, the blank (No. 3) is stretched on the upper and lower flat anvils (No. 4 and 5), as shown in FIG. Figure 4 As shown, the blank (No. 3) is continuously stretched to a square shape of 530, as shown in FIG. Figure 5 Then, the square blank (No. 3) is turned to 550 on the upper and lower flat anvils (No. 4 and 5). Figure 6 As shown, the riser is chopped off at last, and the forging machine is directly put into the forging process to be finished product without returning to the furnace. The purpose of "chopping off the riser" is to shorten the discarded material at the riser end after the forging is finished, improve the cooling intensity of the good material position, reduce the precipitation of network carbides, and improve the annealing structure; "not returning to the furnace" is coordinated with step 3) to reduce the temperature during forging; Step 3), forge on a diameter forging machine at controlled temperature to a finished product size of Φ370; the schematic diagram of the forging process is as follows Figure 7 As shown, the serial numbers 6, 7, 8, and 9 are the four hammers of the radial forging machine, and the schematic diagram of the finished forging is shown in Figure 8 As shown. The radial forging machine is used for temperature-controlled forging. The specific requirements are: before each forging pass, the material is dried to a temperature of the highest point on the surface between 750 and 800°C. During each forging pass, only one-side pulling is allowed, and the empty pass is returned. The pulling speed is controlled to be ≤3m / min, and the reduction amount is between 40 and 70mm to ensure that the final forging temperature is between 750 and 850°C. The purpose of temperature-controlled forging is: 1. Lowering the temperature during forging can refine the grains of the forgings. Finer grains and more grain boundaries will hinder the carbides from forming a network or chain, making the annealing structure better graded and improving the annealing structure qualification rate. 2. In the temperature range of temperature-controlled forging, some carbides have already precipitated. After forging, the precipitated carbides can be broken up and distributed more evenly, which can also make the annealing structure better graded and improve the annealing structure qualification rate; Step 4), the post-forging heat treatment adopts "high temperature normalizing + isothermal spheroidizing annealing", which can make the network, chain carbide or larger carbide particles re-dissolve and make them evenly distributed in spherical shape, which has a good effect on improving the annealing structure; the normalizing temperature is 1000-1050℃, and the isothermal spheroidizing temperature is 850-880℃ and 740-760℃ respectively. The cooling method after forging and normalizing is: "first mist cooling to 300-350℃, then air cooling to 200-250℃ before entering the furnace"; by continuing air cooling to lower the temperature of the forging entering the furnace, sufficient cooling intensity can be guaranteed to reduce the precipitation of network or chain carbides, and a certain grain refinement effect can be achieved, and ultimately the annealing structure can be improved; After that, surface and dimension inspection, ultrasonic flaw detection, sawing and cutting, and physical and chemical testing are carried out.
[0022] By adopting the above forging methods and strictly controlling the forging parameters of each process, the physical and chemical testing annealing structure is qualified and no coarse grains appear.
[0023] Table 1. Annealed structure Ingot No. Forging specifications Tail Center Center Testing standards Sample 1 Φ360mm AS3 AS3 NADCA#207 Sample 2 Φ360mm AS3 AS3 NADCA#207 Forging Example 2: Take the electroslag ingot forging of Φ300 H13 round steel as an example. Figure 2 ), the electroslag ingot weighs 6 tons, has a diameter of Φ750mm and a height of approximately 1730mm.
[0024] The specific steps of forging are as follows: Step 1), the electroslag ingot is kept at 450±10℃ for 4h, then heated to 850±10℃ at ≤60℃ / h for 4h, and then heated to 1250±10℃ at ≤120℃ / h for high temperature diffusion for 20h. High temperature diffusion can effectively improve the segregation and liquid precipitation inside the original steel ingot, make the composition uniform, dissolve the coarse liquid precipitation carbides, and finally improve the annealing structure of the finished forging. After high temperature diffusion, the ingot is cooled to 1230±10℃ and taken out of the furnace. Cooling is beneficial to prevent coarse grains in the forgings; Step 2) Calculate the drawing ratio of 6.2, which is less than 7, so it is necessary to increase the upsetting. After the furnace, the electroslag ingot (also called billet, No. 3) is upset from 1730mm to 800mm on the hydraulic press using the upper plate (No. 1) and the lower platform (No. 2). The upsetting pressure is 50% to 60%. Figure 2 and Figure 3 After upsetting, the blank (No. 3) is stretched on the upper and lower flat anvils (No. 4 and 5), as shown in FIG. Figure 4 As shown, the blank (No. 3) is continuously stretched to a square shape of 530, as shown in FIG. Figure 5 Then, the square blank (No. 3) is turned to 550 on the upper and lower flat anvils (No. 4 and 5). Figure 6 As shown, the riser is chopped off at last, and the forging machine is directly put into the forging process to be finished product without returning to the furnace. The purpose of "chopping off the riser" is to shorten the discarded material at the riser end after the forging is finished, improve the cooling intensity of the good material position, reduce the precipitation of network carbides, and improve the annealing structure; "not returning to the furnace" is coordinated with step 3) to reduce the temperature during forging; Step 3), forge on a radial forging machine at controlled temperature to a finished product size of hot Φ310. The schematic diagram of the forging process is as follows Figure 7 As shown, the serial numbers 6, 7, 8, and 9 are the four hammers of the radial forging machine, and the schematic diagram of the finished forging is shown in Figure 8As shown. The radial forging machine is used for temperature-controlled forging. The specific requirements are: before each forging pass, the material is dried to a temperature of the highest point on the surface between 750 and 800°C. During each forging pass, only one-side pulling is allowed, and the empty pass is returned. The pulling speed is controlled to be ≤3m / min, and the reduction amount is between 40 and 70mm to ensure that the final forging temperature is between 750 and 850°C. The purpose of temperature-controlled forging is: 1. Lowering the temperature during forging can refine the grains of the forgings. Finer grains and more grain boundaries will hinder the carbides from forming a network or chain, making the annealing structure better graded and improving the annealing structure qualification rate. 2. In the temperature range of temperature-controlled forging, some carbides have already precipitated. After forging, the precipitated carbides can be broken up and distributed more evenly, which can also make the annealing structure better graded and improve the annealing structure qualification rate; Step 4), the post-forging heat treatment adopts "isothermal spheroidizing annealing", and the isothermal spheroidizing temperatures are 850-880°C and 740-760°C respectively; After that, surface and dimension inspection, ultrasonic flaw detection, sawing and cutting, and physical and chemical testing are carried out.
[0025] By adopting the above forging methods and strictly controlling the forging parameters of each process, the physical and chemical testing annealing structure is qualified and no coarse grains appear.
[0026] Table 2: Annealed structure Ingot No. Forging specifications Tail Center Center Testing standards Sample 3 Φ300mm AS3 AS3 NADCA#207 Sample 4 Φ300mm AS4 AS4 NADCA#207
Claims
1. A forging method for improving the annealing structure of H13 round steel, characterized in that: The steel ingot diffuses at high temperature → it is stretched after upsetting on a hydraulic press or stretched directly → it is forged by a radial forging machine with controlled temperature → it is heat treated after forging. The specific forging steps are as follows: Step 1), heating: the steel ingot is kept at 450±10℃ for 3-7h, then heated to 850±10℃ at ≤60℃ / h for 3-7h, then heated to 1250-1280±10℃ at ≤120℃ / h for high temperature diffusion, the high temperature diffusion time is calculated as 2.5h-3h / 100mm according to the cross section of the steel ingot, then cooled to 1230±10℃ and taken out of the furnace; Step 2), after the steel ingot is taken out of the furnace, it is upset on the hydraulic press and then stretched or directly stretched. If the stretching-forging ratio is less than 7, it is necessary to increase the upsetting, and the upsetting pressure is 50% to 60%; the upsetting adopts the upper and lower flat anvils, stretches to four sides and inverts eight sides, and the size needs to meet the feeding of the radial forging machine, cuts off the riser, and then does not return to the furnace, and directly goes to the radial forging machine for forging; Step 3), forging and forming in a radial forging machine under temperature control; Step 4) Post-forging heat treatment adopts "high temperature normalizing + isothermal spheroidizing annealing" or "isothermal spheroidizing annealing" when the specification is Φ80~Φ350.
2. A forging method for improving the annealing structure of H13 round steel according to claim 1, characterized in that: In step 2), it should be noted that at least 20% of the deformation should be reserved for the last fire of the hydraulic press to prevent coarse grains; the riser should be chopped off after the hydraulic press is completed to increase the cooling intensity of the good material position of the finished forging; after the hydraulic press is completed, it is not allowed to return to the furnace and go directly to step 3) in order to cooperate with step 3) to reduce the temperature during forging.
3. A forging method for improving the annealing structure of H13 round steel according to claim 1, characterized in that: In step 3), during the temperature-controlled forging process on the radial forging machine, the specific requirements are as follows: before each forging pass, the material is dried to a temperature of the highest point on the surface between 750 and 800°C; during each forging pass, only one-side pulling is allowed, and empty passes are returned; the pulling speed is controlled to be ≤3m / min, the reduction amount is between 40 and 70mm, and the final forging temperature is guaranteed to be between 750 and 850°C.
4. A forging method for improving the annealing structure of H13 round steel according to claim 1, characterized in that: In step 4), "high temperature normalizing + isothermal spheroidizing annealing", the normalizing temperature is 1000-1050℃, and the isothermal spheroidizing temperatures are 850-880℃ and 740-760℃ respectively; the cooling method after forging and normalizing in this heat treatment method is: ≥Φ400mm specifications adopt "first water cooling, then air cooling to 250-300℃ before entering the furnace", and Φ80-Φ400 specifications adopt "first mist cooling to 300-350℃, then air cooling to 200-250℃ before entering the furnace".
5. A forging method for improving the annealing structure of H13 round steel according to claim 1, characterized in that: In step 4), "isothermal spheroidizing annealing" is selected for Φ80~Φ350 specifications, and the isothermal spheroidizing temperatures are 850~880℃ and 740~760℃ respectively.