CN109894473B - Method for producing hot work die steel by directly forging continuous casting billet - Google Patents
Method for producing hot work die steel by directly forging continuous casting billet Download PDFInfo
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- CN109894473B CN109894473B CN201910266270.XA CN201910266270A CN109894473B CN 109894473 B CN109894473 B CN 109894473B CN 201910266270 A CN201910266270 A CN 201910266270A CN 109894473 B CN109894473 B CN 109894473B
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Abstract
The invention provides a method for producing hot die steel by adopting continuous casting billet direct forging. The method specifically comprises the following steps: carrying out end face seal welding or surfacing on the sawed continuous casting billet, and then carrying out first homogenization: homogenizing at 1150-1320 ℃ for 3-6 h; rapidly cooling the surface of the primarily homogenized continuous casting billet to below 1050 ℃, carrying out unidirectional high-pressure specific deformation, and homogenizing for 10-20 h at 1150-1320 ℃ for the second time; carrying out three-way forging on the twice homogenized billet; the three-way forging start forging temperature is below 1250 ℃, and the finish forging temperature is 800-950 ℃; and refining grains and annealing to obtain the product. The invention organically combines the special treatment, twice homogenization and twice forging of the continuous casting billet to create a dynamic condition which is beneficial to the diffusion of carbon and alloy elements, and thoroughly eliminates the defects of continuous loose pores and the like in the center of the continuous casting billet, the decomposition of liquated carbide and a banded structure generated by dendrite segregation.
Description
Technical Field
The invention relates to the field of special steel production, in particular to a process method for producing high-quality hot work die steel by directly forging a continuous casting billet.
Background
The hot work die steel widely used at present is mainly prepared by homogenizing and forging cast ingots or electroslag ingots. Due to the defects of loose center continuity (penetrability), shrinkage cavity and the like of the continuous casting billet, the conventional heating → forging → grain refinement → annealing process cannot produce the die steel material with defect-free flaw detection. Compared with an ingot and an electroslag ingot, the advantages of small content of liquated carbide in the continuous casting billet, relatively uniform structure, high yield and low cost are not exerted. The invention takes the continuous casting slab as the raw material, and can produce the hot work die steel with high quality and low cost through the processes of special pretreatment of the sawing section of the continuous casting slab → pre-homogenization → special preforging → secondary homogenization → three-way forging and the like.
The toughness and isotropy of the hot die steel produced by the conventional method cannot meet the changing technical requirements. Especially in the aspects of large-scale die casting, large-section nonferrous metal (aluminum alloy) extrusion and precision forging dies, along with the development of automation and intellectualization of equipment, the working condition of the dies is worsened more and more, and the service life of the dies can not meet the market demand. The advantages of small size and relatively uniform distribution of the liquated carbide of the continuous casting billet are utilized, and the special pretreatment, homogenization and forging processes are adopted to produce the large-section hot-working die steel with high toughness and high isotropy, so that the large hot-working die with high quality and long service life is the requirement for the development of modern automobiles, electronic home appliances and rail transit transportation industries.
The hot work die steel usually contains alloy elements such as Cr, Mo and V which improve the red hardness of the steel, and liquated carbides and a banded structure which appears due to dendrite segregation are generated in the solidification process, and the phenomenon is particularly serious in the centers of large-section ingots and electroslag ingots. The liquated carbide and dendritic crystal segregation greatly reduce the toughness and the isotropy of the steel, and researches show that: increasing the number of liquated carbides above 3 μm from 1 to 2 per square millimeter reduces the ductility of the steel by nearly a factor of two. Therefore, the die material adopting the structure can not meet the requirements of severe operating environments such as die-casting, extrusion, precision forging and the like, the service life of the die is very short, and even the integral cracking phenomenon of the die occurs.
The method for sequentially researching and developing the high-tropism and high-toughness die steel at home and abroad in recent 20 years adopts a homogenization and powerful forging method, and the typical production process comprises the following steps: electric arc furnace (intermediate frequency furnace) → ladle refining → vacuum degassing → ingot casting → electroslag remelting → homogenization → forging → grain refinement → full annealing. In the process, for electroslag ingot large-section hot-working die steel (the section with the thickness of more than 200 mm and the diameter of more than 1000 mm), homogenization treatment needs to be carried out at 1150-1320 ℃ for a long time (20 hours), and nevertheless, a considerable amount of liquated carbides and a banded structure generated by dendritic segregation can be found in the central part of the steel structure. The method adopts the continuous casting billet to directly forge the hot die steel forging material, fully utilizes the advantages of small size and relatively uniform distribution of the quick crystallization liquated carbide of the continuous casting billet, eliminates the center continuity defect of the continuous casting billet through special continuous casting billet pretreatment, 2 times of homogenization and special forging process, and produces the hot die steel with high toughness and high isotropy.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
The first purpose of the invention is to provide a low-cost production process method of high-quality hot die steel by using a continuous casting billet as a raw material, wherein the production method thoroughly eliminates continuous looseness and shrinkage at the center of the continuous casting billet, as well as liquated carbides in a steel billet and a banded structure generated by dendrite segregation by virtue of saw cutting continuous casting billet pretreatment, homogenization and special forging alternative treatment, and obtains the hot die steel with high toughness, high ductility and high isotropy.
The second purpose of the invention is to provide high-toughness and high-isotropy hot-work die steel which has the advantages of high toughness, high ductility, high isotropy and the like, and meanwhile, the cost is reduced while high-quality hot-work die steel is obtained due to the high yield and low cost of the continuous casting billet.
In order to achieve the above purpose of the present invention, the following technical scheme is adopted:
a process method for producing hot die steel by directly forging a continuous casting billet comprises the following steps:
and step A, performing end face seal welding (surfacing welding) on the sawed continuous casting billet by adopting the following method, wherein the surfacing welding range is that the core part of the cross section at least covers half of the diameter of the continuous casting billet, and the thickness of the surfacing welding layer is at least 3 mm. Placing the mixture into a heating furnace for primary homogenization: homogenizing and insulating for 3-6 h after the center of the continuous casting billet reaches 1150-1320 ℃;
and step B, taking out the continuous casting billet with the temperature of more than 1150-1320 ℃ from the furnace, and carrying out surface cooling. When the surface temperature of the continuous casting billet is rapidly reduced to 950-1050 ℃, and the central temperature is preferably above 1050 ℃, the unidirectional high-reduction ratio pre-forging in the diameter direction is immediately carried out. Single-pass reduction ratio: more than or equal to 10 percent; the total reduction ratio: more than or equal to 30 percent;
and step C, placing the billet subjected to the radial one-way high-pressure rolling-down ratio pre-forging in a heating furnace for secondary high-temperature homogenization treatment. Homogenizing at constant temperature for 10-20 hr after the center of the continuous casting billet reaches 1150-1320 ℃;
d, after the preset heat preservation time is reached, reducing the furnace temperature to 1100-1250 ℃, preserving the heat for more than 4 hours, and starting three-way forging;
and E, like the situation that three-dimensional forging cannot be finished by one heating, reheating at 1150-1250 ℃ and continuously forging until full deformation in three directions is finished. Controlling the finish forging temperature to be below 950 ℃;
step F: and carrying out grain refinement and annealing treatment on the twice-forged steel billet to obtain a product.
The production method can thoroughly eliminate central continuity porosity, shrinkage cavity, liquated carbide and banded structure generated by dendrite segregation in the continuous casting billet, thereby improving the hot working die performance such as toughness, ductility and isotropy of the steel. The elimination principle is as follows:
aiming at continuous shrinkage cavity and porosity of the continuous casting billet in the core length direction, re-oxidation of the core shrinkage cavity and the surface of the porosity is caused in the heating high-temperature homogenization process after sawing, so that forging and welding of the defects are hindered. And before the furnace is heated, plugging and surfacing welding are carried out on the sawed end face. The thickness of the overlaying layer is 3-6 mm, and air is prevented from entering the continuous casting billet through loosening in the high-temperature homogenization process. Performing primary high-temperature homogenization, cooling to reduce the surface temperature of the continuous casting billet to 980 ℃ after the core of the continuous casting billet reaches a specified temperature and is kept warm for a certain time, and performing unidirectional high-reduction ratio forging in the diameter or cross section direction under the condition that the core temperature is still at a high temperature (above 1050 ℃). The purpose is to utilize the surface with large low-temperature deformation resistance and effectively transmit stress to the central part to cause the core with small high-temperature deformation resistance to generate violent core deformation under the condition of large pressure-reduction ratio, thereby leading the core to be loose and compacted by shrinkage cavity. In the subsequent second long-time homogenization process, the loosening and shrinkage cavities of the mechanical press can spread the alloying elements to fully diffuse each other. On the other hand, in the first homogenization, large-particle chain carbides and coarse dendrite alloying elements are rapidly segregated and diffused into a large region, that is, are unstably diffused, at a high temperature in the first homogenization, by utilizing a large concentration gradient between carbon and the alloying elements and the surrounding area. According to Fick's second law, the diffusion flux rapidly decreases with the extension of diffusion time, at this time, by forging in the direction of specific diameter or cross section under unidirectional high pressure, the liquated carbide which is not uniformly diffused yet and the dendrite segregation region of selective crystallization are mechanically redistributed (carbide is broken) through solid state rheology, a new diffusion concentration field with a larger gradient is established, the diffusion area is increased, and the diffusion distance between carbon and alloy elements is shortened. And the second long-time homogenization is carried out under the driving of a newly established concentration field, so that the carbon and the alloy elements are fully diffused, and the complete homogenization is realized. The loose and shrinkage cavity after compaction realizes the diffusion welding of mechanically pressed surface metal elements in the second long-time homogenization process, and thoroughly eliminates liquated carbide and banded structures generated by dendrite segregation. And finally, forging in three directions, refining grains and annealing to obtain a final product.
In the process, the temperature and time of each step of the process are important for welding the loose and the shrinkage cavity, eliminating liquated carbide and a banded structure generated by dendrite segregation. For example, in the steps A and C, the thickness of the end face overlaying and the quality of the overlaying are directly related to whether oxygen in air can be completely blocked from entering the interior of the continuous casting billet or not; in the homogenization process, if the temperature is lower than the lower limit, the homogenization effect is poor, and if the temperature is higher than the upper limit, intercrystalline melting can be caused; the surface and the core of the one-way high-reduction ratio forging cannot be welded with the core defects to form a large enough concentration field when the temperature is too high or too low or the time is insufficient; the temperature of the three-way forging is lower than the lower limit, which may cause cracking, and higher than the upper limit, which may easily cause coarse grains.
Therefore, the production method effectively seals and welds the cross section of the continuous casting billet, organically combines the two through the alternate treatment of twice homogenization and twice forging, creates the dynamic conditions which are beneficial to the welding of the loose and the shrinkage cavity and the diffusion of carbon and alloy elements, thoroughly eliminates the continuous loose, the shrinkage cavity, the liquated carbide and the strip-shaped structure generated by dendrite segregation in the continuous casting billet, and obtains the hot work die steel with higher toughness, ductility and isotropy in the homogenization time which is equivalent to the prior art. The production method can be used for manufacturing various types of hot-work die steel, such as H13(4Cr5MoSiV1), H11(4Cr5MoSiV), 1.2714(5CrNiMo), novel Diever (4Cr5Mo2V) and the like.
Preferably, during the end face sealing of the sawed continuous casting billet, at least the whole inner circle surface of 1/2R is achieved, the sealing layer is required to be at least more than 3 mm, for example 3-6 mm, and the sealing layer is free from any crack or micro-crack. And (3) tempering and stress removing treatment are carried out after welding repair, or the temperature is slowly increased to the homogenization temperature along with the furnace, and the temperature increasing speed is not more than 80 ℃ per hour. Homogenization temperature: 1150-1320 ℃; homogenization time: the core reaches the homogenization temperature for 3-6 hours.
Preferably, the unidirectional high-reduction-ratio forging in the diameter or cross section direction is carried out immediately after the surface is cooled to the surface temperature of 950-1050 ℃ and the core temperature is higher than the high temperature (1050 ℃). Single-pass reduction ratio: more than 10 percent; the total reduction ratio: is greater than 30%.
Preferably, the second homogenization is a sufficient diffusion process for a long period of time. Homogenization temperature: 1150-1320 ℃; homogenizing and keeping the temperature for a certain time: after the billet core reaches the homogenization temperature: 10 to 20 hours.
Preferably, the open forging temperature after the second homogenization is 1100 to 1250 ℃. The three-way forging is carried out according to the following sequence: steel ingot upsetting → Z-direction upsetting → X-direction upsetting → Y-direction upsetting → Z-direction elongation (fig. 2).
Preferably, the number of reheating is minimized during the three-way forging to save energy consumption.
Preferably, the center of the billet is ensured to reach a preset temperature during the homogenizing and forging processes, during heating and during repeated heating, so as to ensure that each area can be sufficiently homogenized or plastically deformed.
Preferably, the method for grain refinement is as follows:
and cooling the sand pit until the surface temperature of the steel billet is lower than 600 ℃, then heating to be 30-90 ℃ above the austenitizing temperature, preserving the heat for 30 minutes at the temperature, and then cooling to be below 200 ℃ at the speed of 20 ℃/minute above.
Preferably, in the steps B to E, the upsetting deformation rate in each direction is 10% or more, preferably 30% or more, so that the central deformation amount is satisfied. The forging results of all parts of the billet are more uniform, and 20-60% is more preferable.
Preferably, in the steps B to E, the reduction per pass in the three-way forging is 10% or more, preferably 15% or more, excluding the finishing pass. Similarly, the strict requirement of the reduction ratio of each pass is to ensure that the central deformation reaches the requirement and the forging results of all parts of the billet are uniform.
Preferably, the second homogenization time is at least 3 times, preferably more than 4 times, the first homogenization time, so as to ensure sufficient homogenization time and achieve the purpose of complete homogenization, thereby completely eliminating loose and shrinkage cavities, fully decomposing carbide and fully diffusing.
Preferably, the method for grain refinement further comprises:
cooling the sand pit until the surface temperature of the billet is lower than 650 ℃, then heating the billet to be higher than the austenitizing temperature by 30-90 ℃ (950-. After the grain refining method is adopted, the isometric crystal in the obtained steel billet is more uniform and fine.
Preferably, the annealing treatment method comprises the following steps: spheroidizing and annealing until the hardness of the material is less than or equal to 220HB to obtain spherical or granular carbides uniformly distributed on a ferrite matrix.
Preferably, the finish forging temperature of the three-way forging is above 800 ℃ to reduce the probability of occurrence of cracking phenomenon.
The high-quality hot work die steel produced by directly forging the continuous casting billet is prepared by the process method.
As described above, the hot work die steel has advantages of high toughness, high ductility, high isotropy, and the like.
Compared with the prior art, the invention has the beneficial effects that:
(1) the hot die steel continuous casting billet has the characteristics of low production cost and high yield. Because the continuous casting billet has high crystallization speed, the formed liquated carbide has small particles and relatively uniform distribution, and the core of the continuous casting billet is easy to generate continuous loose and continuous through shrinkage cavities due to the same reason. If the surface sealing welding treatment is carried out on the special sawing continuous casting billet, the surface is cooled, the unidirectional high reduction ratio forging, the secondary homogenization and other technological processes are improved. On one hand, the loose and shrinkage cavity is eliminated, on the other hand, the metal elements are fully diffused, the tissue segregation is thoroughly eliminated, and the hot work die steel with high toughness and isotropy can be manufactured on the basis of lower production cost.
(2) After the cold continuous casting billet with continuously loosened and shrunk core is cut and cut by sawing, the loosened and shrunk surface can become a conveying pipeline of air (oxygen) during forging and heating. Surfacing and plugging are carried out on the sawed end face before the continuous casting billet enters a furnace and is heated, surfacing materials can be ordinary low-carbon welding rods or stainless steel welding rods, and a plugging surfacing layer is 2-6 mm, so that the continuous casting billet is loose in the center part and is not oxidized with the inner surface of a shrinkage cavity in the first homogenization process.
(3) The heating furnace takes out the continuous casting billet at high temperature and places the continuous casting billet on the forging pillow, and the surface of the continuous casting billet is quenched. When the surface temperature reaches 900-1050 ℃, unidirectional high-reduction-ratio forging is immediately carried out in the cross section direction. Single-pass reduction ratio: more than 10 percent; the total reduction ratio: is greater than 30%. Aims to compact the continuity of the central part of the continuous casting billet, such as loosening and shrinkage.
(4) The billet subjected to the one-way high reduction in the cross section direction is placed in a heating furnace again for the second homogenization. The temperature of the second homogenization is 1150-1320 ℃; the homogenization time is constant temperature for 10-20 hours after the core reaches the temperature.
(5) Through the alternate treatment of twice homogenization and twice forging, the two are organically combined, the dynamic condition which is beneficial to the diffusion of carbon and metal elements is created, the fusion of a welding part is facilitated, the liquated carbide in a billet and a banded structure generated by dendrite segregation are thoroughly eliminated, and the hot-work die steel with higher toughness, ductility and isotropy is obtained in the homogenization time equivalent to that of the prior art.
(6) The forging sequence, the deformation rate and the reduction rate of each pass of homogenization, one-way large reduction ratio and three-way forging are optimized, so that the structure quality of each part of the prepared hot work die steel is higher, and the quality of each area is uniform.
(7) The time difference of the two homogenization is optimized so as to completely eliminate the phenomena of carbide and segregation.
(8) Aiming at the homogeneous forging method, the corresponding grain refinement and annealing conditions are optimized.
Drawings
FIG. 1 is a flow chart of one-way high reduction ratio initial forging in an embodiment of the present invention;
FIG. 2 is a three-way forging flow chart according to an embodiment of the present invention.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. 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.
Example 1
A process method for producing high-quality hot work die steel by directly forging a continuous casting billet comprises the following steps:
the first step is as follows: the annealed continuous casting billet is 500 mm in diameter (the steel type is H13(4Cr5MoSiV1)), and the length of the annealed continuous casting billet is 1200 mm (the length/diameter is less than 2-3) by sawing.
The second step is that: and (3) surfacing plugging of two sawed end faces of the continuous casting billet, wherein the thickness of the surfacing layer is at least 3 mm within a surfacing range of the center of the cross section, namely within a radius range of phi 250 mm of the cross section. And (3) performing stress relief treatment on the continuously cast blank subjected to sealing welding at the temperature of 450-600 ℃ for 2 hours after the temperature of the core reaches the temperature. The welding wire is made of low-carbon steel or austenitic stainless steel, and the surfacing mode can be arc welding, argon arc welding, laser cladding of pure iron powder and the like.
The third step: and (3) placing the continuous casting billet subjected to sealing welding and stress removal treatment in a heating furnace, heating to 1200 ℃, and preserving heat for 4 hours after the center reaches a set temperature to finish primary homogenization.
The fourth step: and (3) rapidly transferring the continuous casting billet after the first homogenization to operating pliers of a forging press, quenching the surface of the billet by using a high-pressure water spraying method, and measuring the surface temperature. When the surface temperature reached 950 ℃, the unidirectional high reduction ratio forging in the cross-sectional direction was started, see fig. 1. Single-pass reduction ratio: more than 10 percent; the total reduction ratio: is greater than 30%.
The fifth step: and (3) putting the unidirectionally forged flat steel billet in the heating furnace again, and performing second homogenization, wherein the homogenization temperature is as follows: 1200 ℃; homogenization time: the core was kept at the temperature for 10 hours to achieve complete homogenization.
And a sixth step: and (3) slowly cooling the fully homogenized billet to 1150 ℃, keeping the temperature constant for 4 hours, and then starting three-direction forging, wherein the flow is shown in figure 2, and the final forging temperature is 800 ℃ at the minimum and 950 ℃ at the maximum to obtain the size required by a customer.
The fifth step: the steel obtained by the homogenizing forging process is put into a heating furnace to be heated to 30 ℃ above the austenitizing temperature after a sand pit is cooled to the temperature of the surface of a billet to be lower than 500 ℃, the heat preservation is carried out for 20 minutes after the core reaches the specified temperature, and the temperature is forcibly cooled to below 250 ℃ at the cooling speed of more than or equal to 20 ℃/minute. Then immediately carrying out spheroidizing annealing until the hardness of the material is less than or equal to 220 HB.
Example 2
The first step is as follows: the annealed continuous casting billet is 650 mm in diameter (the type of the steel is H13(4Cr5MoSiV1)), and the length of the cut billet is 1600 mm (the length/diameter is less than 2-3).
The second step is that: and (3) surfacing plugging of two sawed end faces of the continuous casting billet, wherein the thickness of the surfacing layer is at least 1 mm within the surfacing range of the center of the cross section, namely the radius range of the cross section phi 325 mm. And (3) performing stress relief treatment on the continuously cast blank subjected to sealing welding at the temperature of 550-750 ℃ for 2 hours after the temperature of the core reaches the temperature. The welding wire is made of low-carbon steel or austenitic stainless steel, and the surfacing mode can be arc welding, argon arc welding, laser cladding of pure iron powder and the like.
The third step: and (3) placing the continuous casting billet subjected to sealing welding and stress removal treatment in a heating furnace, heating to 1200 ℃, and preserving heat for 6 hours after the center reaches a set temperature to finish primary homogenization.
The fourth step: and (3) rapidly transferring the continuous casting billet after the first homogenization to operating pliers of a forging press, quenching the surface of the billet by using a high-pressure water spraying method, and measuring the surface temperature. When the surface temperature reached 950 ℃, the unidirectional high reduction ratio forging in the cross-sectional direction was started, see fig. 1. Single-pass reduction ratio: more than 10 percent; the total reduction ratio: is greater than 30%.
The fifth step: and (3) putting the unidirectionally forged flat steel billet in the heating furnace again, and performing second homogenization, wherein the homogenization temperature is as follows: 1200 ℃; homogenization time: the core was kept at a constant temperature for 20 hours after reaching the temperature, and complete homogenization was achieved.
And a sixth step: and (3) slowly cooling the fully homogenized billet to 1200 ℃, keeping the temperature constant for 4 hours, and then starting three-direction forging, wherein the flow is shown in figure 2, and the final forging temperature is 800 ℃ at the lowest and 950 ℃ at the highest, so that the size required by a customer is obtained.
The fifth step: the steel obtained by the homogenizing forging process is put into a heating furnace to be heated to 30 ℃ above the austenitizing temperature after a sand pit is cooled to the temperature of the surface of a billet to be lower than 600 ℃, the heat preservation is carried out for 20 minutes after the core reaches the specified temperature, and the temperature is forcibly cooled to be below 200 ℃ at the cooling speed of more than or equal to 20 ℃/minute. Then immediately carrying out spheroidizing annealing until the hardness of the material is less than or equal to 220 HB.
Example 3
A process method for producing high-quality hot work die steel by directly forging a continuous casting billet comprises the following steps:
the first step is as follows: the annealed continuous casting billet is phi 390 mm (the steel type is H13(4Cr5MoSiV1)), and the length of the cut billet is 1000 mm (the length/diameter is less than 2-3).
The second step is that: and (3) surfacing plugging of two sawed end faces of the continuous casting billet, wherein the thickness of the surfacing layer is at least 3 mm within the surfacing range of the center of the cross section, namely within the radius range of phi 185 mm of the cross section. And (3) performing stress relief treatment on the sealed and welded continuous casting blank at 550-750 ℃ for 2 hours after the core reaches the temperature. The welding wire is made of low-carbon steel or austenitic stainless steel, and the surfacing mode can be arc welding, argon arc welding, laser cladding of pure iron powder and the like.
The third step: and (3) placing the continuous casting billet subjected to sealing welding and stress removal treatment in a heating furnace, heating to 1200 ℃, and preserving heat for 3 hours after the center reaches a set temperature to finish primary homogenization.
The fourth step: and (3) rapidly transferring the continuous casting billet after the first homogenization to operating pliers of a forging press, quenching the surface of the billet by using a high-pressure water spraying method, and measuring the surface temperature. When the surface temperature reached 950 ℃, the unidirectional high reduction ratio forging in the cross-sectional direction was started, see fig. 1. Single-pass reduction ratio: more than 10 percent; the total reduction ratio: is greater than 30%.
The fifth step: and (3) putting the unidirectionally forged flat steel billet in the heating furnace again, and performing second homogenization, wherein the homogenization temperature is as follows: 1200 ℃; homogenization time: the core was kept at the temperature for 12 hours to achieve complete homogenization.
And a sixth step: and (3) slowly cooling the fully homogenized billet to 1150 ℃, keeping the temperature constant for 4 hours, and then starting three-direction forging, wherein the flow is shown in figure 2, and the final forging temperature is 800 ℃ at the minimum and 950 ℃ at the maximum to obtain the size required by a customer.
The fifth step: the steel obtained by the homogenizing forging process is put into a heating furnace to be heated to 30 ℃ above the austenitizing temperature after a sand pit is cooled to the temperature of the surface of a billet to be lower than 600 ℃, the heat preservation is carried out for 20 minutes after the core reaches the specified temperature, and the temperature is forcibly cooled to be below 200 ℃ at the cooling speed of more than or equal to 20 ℃/minute. Then immediately carrying out spheroidizing annealing until the hardness of the material is less than or equal to 220 HB.
Example 4
A process method for producing high-quality hot work die steel by directly forging a continuous casting billet comprises the following steps:
the first step is as follows: the annealed continuous casting billet is 385X425 mm (the steel type is H13(4Cr5MoSiV1)), and the length is cut by sawing and cutting, wherein the length/diameter is less than 2-3 mm.
The second step is that: and (3) surfacing plugging of two sawed end faces of the continuous casting billet, wherein the thickness of the surfacing layer is at least 3 mm within the surfacing range of the center of the cross section of the continuous casting billet by at least 50% of the area of the center of the cross section, namely within the range of 200X220 mm of the center of the cross section. And (3) performing stress relief treatment on the continuously cast blank subjected to sealing welding at the temperature of 550-750 ℃ for 2 hours after the temperature of the core reaches the temperature. The welding wire is made of low-carbon steel or austenitic stainless steel, and the surfacing mode can be arc welding, argon arc welding, laser cladding of pure iron powder and the like.
The third step: and (3) placing the continuous casting billet subjected to sealing welding and stress removal treatment in a heating furnace, heating to 1200 ℃, and preserving heat for 5 hours after the center reaches a set temperature to finish primary homogenization.
The fourth step: and (3) rapidly transferring the continuous casting billet after the first homogenization to operating pliers of a forging press, quenching the surface of the billet by using a high-pressure water spraying method, and measuring the surface temperature. When the surface temperature reached 950 ℃, the unidirectional high reduction ratio forging in the direction of the cross section (preferably in the direction of 425 mm) was started, see fig. 1. Single-pass reduction ratio: more than 10 percent; the total reduction ratio: is greater than 30%.
The fifth step: and (3) putting the unidirectionally forged flat steel billet in the heating furnace again, and performing second homogenization, wherein the homogenization temperature is as follows: 1200 ℃; homogenization time: the core was kept at the temperature for 15 hours to achieve complete homogenization.
And a sixth step: and (3) slowly cooling the fully homogenized billet to 1150 ℃, keeping the temperature constant for 4 hours, and then starting three-direction forging, wherein the flow is shown in figure 2, and the final forging temperature is 800 ℃ at the minimum and 950 ℃ at the maximum to obtain the size required by a customer.
The fifth step: the steel obtained by the homogenizing forging process is put into a heating furnace to be heated to 30 ℃ above the austenitizing temperature after a sand pit is cooled to the temperature of the surface of a billet to be lower than 600 ℃, the heat preservation is carried out for 20 minutes after the core reaches the specified temperature, and the temperature is forcibly cooled to be below 200 ℃ at the cooling speed of more than or equal to 20 ℃/minute. Then immediately carrying out spheroidizing annealing until the hardness of the material is less than or equal to 220 HB.
Example 5
A process method for producing high-quality hot work die steel by directly forging a continuous casting billet comprises the following steps:
the first step is as follows: the annealed continuous casting billet is 500 mm in diameter (the steel type is H418(4Cr5Mo2V)), and the length of the annealed continuous casting billet is 1200 mm (the length/diameter is less than 2-3) by sawing.
The second step is that: and (3) surfacing plugging of two sawed end faces of the continuous casting billet, wherein the thickness of the surfacing layer is at least 3 mm within a surfacing range of the center of the cross section, namely within a radius range of phi 250 mm of the cross section. And (3) performing stress relief treatment on the continuously cast blank subjected to sealing welding at the temperature of 550-750 ℃ for 2 hours after the temperature of the core reaches the temperature. The welding wire is made of low-carbon steel or austenitic stainless steel, and the surfacing mode can be arc welding, argon arc welding, laser cladding of pure iron powder and the like.
The third step: and (3) placing the continuous casting billet subjected to sealing welding and stress removal treatment in a heating furnace, heating to 1200 ℃, and preserving heat for 6 hours after the center reaches a set temperature to finish primary homogenization.
The fourth step: and (3) rapidly transferring the continuous casting billet after the first homogenization to operating pliers of a forging press, quenching the surface of the billet by using a high-pressure water spraying method, and measuring the surface temperature. When the surface temperature reached 950 ℃, the unidirectional high reduction ratio forging in the cross-sectional direction was started, see fig. 1. Single-pass reduction ratio: more than 10 percent; the total reduction ratio: is greater than 30%.
The fifth step: and (3) putting the unidirectionally forged flat steel billet in the heating furnace again, and performing second homogenization, wherein the homogenization temperature is as follows: 1200 ℃; homogenization time: the core was kept at a constant temperature for 20 hours after reaching the temperature, and complete homogenization was achieved.
And a sixth step: and (3) slowly cooling the fully homogenized billet to 1150 ℃, keeping the temperature constant for 4 hours, and then starting three-direction forging, wherein the flow is shown in figure 2, and the final forging temperature is 800 ℃ at the minimum and 950 ℃ at the maximum to obtain the size required by a customer.
The fifth step: the steel obtained by the homogenizing forging process is put into a heating furnace to be heated to 30 ℃ above the austenitizing temperature after a sand pit is cooled to the temperature of the surface of a billet to be lower than 600 ℃, the heat preservation is carried out for 20 minutes after the core reaches the specified temperature, and the temperature is forcibly cooled to be below 200 ℃ at the cooling speed of more than or equal to 20 ℃/minute. Then immediately carrying out spheroidizing annealing until the hardness of the material is less than or equal to 220 HB.
Example 6
A process method for producing high-quality hot work die steel by directly forging a continuous casting billet comprises the following steps:
the first step is as follows: the annealed continuous casting billet is 500 mm in diameter (the type of the steel is H11(4Cr5MoSiV)), and the length of the annealed continuous casting billet is 1200 mm (the length/diameter is less than 2-3) by sawing.
The second step is that: and (3) surfacing plugging of two sawed end faces of the continuous casting billet, wherein the thickness of the surfacing layer is at least 3 mm within a surfacing range of the center of the cross section, namely within a radius range of phi 250 mm of the cross section. And (3) performing stress relief treatment on the continuously cast blank subjected to sealing welding at the temperature of 550-750 ℃ for 2 hours after the temperature of the core reaches the temperature. The welding wire is made of low-carbon steel or austenitic stainless steel, and the surfacing mode can be arc welding, argon arc welding, laser cladding of pure iron powder and the like.
The third step: and (3) placing the continuous casting billet subjected to sealing and stress removal treatment in a heating furnace, heating to 1150 ℃, keeping the temperature for 4 hours after the center reaches a set temperature, and finishing primary homogenization.
The fourth step: and (3) rapidly transferring the continuous casting billet after the first homogenization to operating pliers of a forging press, quenching the surface of the billet by using a high-pressure water spraying method, and measuring the surface temperature. When the surface temperature reached 950 ℃, the unidirectional high reduction ratio forging in the cross-sectional direction was started, see fig. 1. Single-pass reduction ratio: more than 10 percent; the total reduction ratio: is greater than 30%.
The fifth step: and (3) putting the unidirectionally forged flat steel billet in the heating furnace again, and performing second homogenization, wherein the homogenization temperature is as follows: 1150 ℃; homogenization time: the core was kept at the temperature for 12 hours to achieve complete homogenization.
And a sixth step: and (3) slowly cooling the fully homogenized billet to 1150 ℃, keeping the temperature constant for 4 hours, and then starting three-direction forging, wherein the flow is shown in figure 2, and the final forging temperature is 800 ℃ at the minimum and 950 ℃ at the maximum to obtain the size required by a customer.
The fifth step: the steel obtained by the homogenizing forging process is put into a heating furnace to be heated to 30 ℃ above the austenitizing temperature after a sand pit is cooled to the temperature of the surface of a billet to be lower than 600 ℃, the heat preservation is carried out for 20 minutes after the core reaches the specified temperature, and the temperature is forcibly cooled to be below 200 ℃ at the cooling speed of more than or equal to 20 ℃/minute. Then immediately carrying out spheroidizing annealing until the hardness of the material is less than or equal to 220 HB.
Example 7
A process method for producing high-quality hot work die steel by directly forging a continuous casting billet comprises the following steps:
the first step is as follows: the annealed continuous casting billet is 500 mm in phi (the type of the steel is 1.2714(5CrNiMoV), and the length of the annealed continuous casting billet is 1200 mm (the length/diameter is less than 2-3).
The second step is that: and (3) surfacing plugging of two sawed end faces of the continuous casting billet, wherein the thickness of the surfacing layer is at least 3 mm within a surfacing range of the center of the cross section, namely within a radius range of phi 250 mm of the cross section. And (3) performing stress relief treatment on the continuously cast blank subjected to sealing welding at the temperature of 550-750 ℃ for 2 hours after the temperature of the core reaches the temperature. The welding wire is made of low-carbon steel or austenitic stainless steel, and the surfacing mode can be arc welding, argon arc welding, laser cladding of pure iron powder and the like.
The third step: and (3) placing the continuous casting billet subjected to sealing welding and stress removal treatment in a heating furnace, heating to 1200 ℃, and preserving heat for 4 hours after the center reaches a set temperature to finish primary homogenization.
The fourth step: and (3) rapidly transferring the continuous casting billet after the first homogenization to operating pliers of a forging press, quenching the surface of the billet by using a high-pressure water spraying method, and measuring the surface temperature. When the surface temperature reached 950 ℃, the unidirectional high reduction ratio forging in the cross-sectional direction was started, see fig. 1. Single-pass reduction ratio: more than 10 percent; the total reduction ratio: is greater than 30%.
The fifth step: and (3) putting the unidirectionally forged flat steel billet in the heating furnace again, and performing second homogenization, wherein the homogenization temperature is as follows: 1150 ℃; homogenization time: the core was kept at the temperature for 12 hours to achieve complete homogenization.
And a sixth step: and (3) slowly cooling the fully homogenized billet to 1100 ℃, keeping the temperature constant for 4 hours, and then starting three-direction forging, wherein the flow is shown in figure 2, and the final forging temperature is 800 ℃ at the lowest and 950 ℃ at the highest to obtain the size required by a customer.
The fifth step: the steel obtained by the homogenizing forging process is put into a heating furnace to be heated to 30 ℃ above the austenitizing temperature after a sand pit is cooled to the temperature of the surface of a billet to be lower than 600 ℃, the heat preservation is carried out for 20 minutes after the core reaches the specified temperature, and the temperature is forcibly cooled to be below 200 ℃ at the cooling speed of more than or equal to 20 ℃/minute. Then immediately carrying out spheroidizing annealing until the hardness of the material is less than or equal to 220 HB.
While particular embodiments of the present invention have been illustrated and described, it would be obvious that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
Claims (3)
1. A method for producing hot die steel by adopting continuous casting billet direct forging is characterized by comprising the following steps:
step A, carrying out end surface surfacing plugging on the sawed continuous casting billet, wherein the surfacing range of the center of the cross section at least reaches half of the diameter of the continuous casting billet, the thickness of a surfacing layer is 3-6 mm, and placing the surfacing layer into a heating furnace for primary homogenization: homogenizing and insulating for 3-6 h after the center of the continuous casting billet reaches 1150-1320 ℃;
step B, carrying out surface cooling on the continuous casting billet at the temperature of more than 1150 ℃ taken out from the furnace; when the surface temperature of the continuous casting billet is rapidly reduced to 950-1050 ℃, and the central temperature is above 1050 ℃, performing one-way large reduction ratio pre-forging in the diameter direction immediately, wherein the single-pass reduction ratio is as follows: more than or equal to 10 percent; the total reduction ratio: more than or equal to 30 percent;
step C, placing the pre-forged steel billet in a heating furnace for secondary high-temperature homogenization treatment; homogenizing at constant temperature for 10-20 h after the center of the continuous casting billet reaches 1150-1320 ℃;
d, after the preset heat preservation time is reached, reducing the furnace temperature to 1100-1250 ℃, preserving the heat for more than 4 hours, and starting three-way forging; the three-way forging is carried out according to the following sequence: steel ingot upsetting → Z-direction upsetting → X-direction upsetting → Y-direction upsetting → Z-direction elongating;
step E, like the three-way forging cannot be completed by one heating, reheating at 1100-1250 ℃, and then continuing forging until the three-way full deformation is completed; controlling the final forging temperature to be more than 800 ℃ and less than 950 ℃;
step F: and carrying out grain refinement and annealing treatment on the three-way forged steel billet to obtain a product.
2. The method for producing hot die steel through direct forging using a continuous casting slab as claimed in claim 1, wherein the second homogenization time is 3 to 5 times as long as the first homogenization time.
3. A hot work die steel produced by the method for producing a hot work die steel by direct forging using a continuous casting slab according to any one of claims 1 to 2.
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| CN110656227A (en) * | 2019-10-10 | 2020-01-07 | 内蒙古北方重工业集团有限公司 | Hot working method for improving impact toughness of high-strength steel |
| CN110863140B (en) * | 2019-11-06 | 2020-12-29 | 北京科技大学 | Low-alloy ultrahigh-strength structural steel and preparation method thereof |
| CN112845609B (en) * | 2020-12-03 | 2022-06-14 | 联峰钢铁（张家港）有限公司 | Controlled rolling method for improving micro-pores on bearing steel core part |
| CN113000758B (en) * | 2021-03-15 | 2023-01-17 | 大冶特殊钢有限公司 | Square steel forging method |
| CN114210893B (en) * | 2021-12-09 | 2023-07-14 | 山西太钢不锈钢股份有限公司 | Manufacturing method of large-diameter stainless steel round tube blank |
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