CN111041176A - Heat treatment process of hot work die steel - Google Patents
Heat treatment process of hot work die steel Download PDFInfo
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- CN111041176A CN111041176A CN201911396233.7A CN201911396233A CN111041176A CN 111041176 A CN111041176 A CN 111041176A CN 201911396233 A CN201911396233 A CN 201911396233A CN 111041176 A CN111041176 A CN 111041176A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/32—Soft annealing, e.g. spheroidising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/04—Hardening by cooling below 0 degrees Celsius
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Abstract
The invention belongs to the technical field of alloy steel manufacturing processes, and particularly relates to a heat treatment process of hot work die steel, which specifically comprises the following steps: s10, high-temperature homogenization treatment; s20, forging; s30, grain refinement treatment; s40, performing superfine treatment; s50, spheroidizing annealing heat treatment; and S60, hardening and tempering. According to the heat treatment process of the hot work die steel, the high-temperature diffusion homogenization inside the electroslag ingot is realized by utilizing the solidification latent heat inside the electroslag ingot, and the refined crystal grain pre-heat treatment is realized by utilizing the self waste heat of the forge piece, so that an external heat source is not needed or only a small amount of external supplementary heat is needed, and the purpose of saving energy is realized; meanwhile, annealing treatment on the electroslag ingot in a red hot state and cooling treatment on the forged piece after forging are not needed, so that the production time can be greatly reduced, and the production efficiency is improved.
Description
Technical Field
The invention belongs to the technical field of alloy steel manufacturing processes, and particularly relates to a heat treatment process of hot work die steel.
Background
The hot-working die steel has higher requirements on the service performance and the service life because of the severe working environment, therefore, in the process of manufacturing the hot work die steel, the hot work die needs to be subjected to heat treatment for a plurality of times, so as to improve the service performance and the service life of the hot-work die, at present, the metallurgical manufacturing process of the hot-work die steel usually adopts the process of remelting and cooling electroslag smelted by an electric furnace, forging into a material and then spheroidizing and annealing, however, in the actual production process of the current heat treatment process, the forge piece needs to be heated and cooled for many times, so that the manufacture of the forge piece needs to consume larger electric energy, the manufacture cost of the hot work die steel is greatly increased, in addition, the manufactured hot-work die steel also has the defects of poor isotropic performance and low impact toughness, further, the problems of short service period and early failure of the tool and the die made of the hot work die steel exist.
Disclosure of Invention
The invention aims to provide a heat treatment process of hot work die steel, and aims to solve the technical problems that the heat treatment process of the hot work die steel in the prior art is high in energy consumption, and the manufactured hot work die steel is poor in isotropic performance and low in impact toughness.
In order to achieve the purpose, the invention adopts the technical scheme that: a heat treatment process of hot work die steel specifically comprises the following steps:
s10, high-temperature homogenization treatment: directly conveying an electroslag ingot which is subjected to electroslag remelting and is in a red hot state into a forging heating furnace, preserving heat within first preset time, heating to first preset temperature, and preserving heat within second preset time, wherein the first preset temperature is less than or equal to 120 ℃ below a solidus line;
s20, forging: adjusting the heat preservation temperature of the electroslag ingot to a second preset temperature, preserving heat for 2-4 hours, discharging, and directly forging the discharged electroslag ingot, wherein the second preset temperature is less than or equal to 200 ℃ below a solidus line;
s30, grain refining treatment: sending the forged forging piece to a heat treatment workshop for alternately and rapidly cooling by water, air and water until the temperature of the forging piece is cooled to 400-500 ℃, and then putting the forging piece into a 650 ℃ heating furnace for heat preservation;
s40, ultra-fining treatment: heating the forged piece to 850 ℃, preserving heat for a third preset time, heating the forged piece to 1030-1060 ℃, preserving heat for a fourth preset time, discharging, performing water quenching and oil cooling until the temperature of the forged piece is cooled to below 350 ℃, and then sending the forged piece into an annealing furnace;
s50, spheroidizing annealing heat treatment: heating the forge piece to a temperature of 10-30 ℃ above an AC1 line, preserving heat within a fifth preset time, cooling the forge piece to a temperature of 0-30 ℃ above an Ar1 line, preserving heat within a sixth preset time, cooling the forge piece to a temperature below 350 ℃, discharging the forge piece out of the furnace, and air cooling to room temperature;
s60, hardening and tempering: and heating the forging to 1020-1060 ℃, preserving heat within seventh preset time, cooling by adopting oil quenching, and then tempering.
Optionally, in step S10: in the step S10: the first preset time ranges from 6h to 9 h.
Optionally, in the step S10: the second preset time is less than or equal to 36 h.
Optionally, in the step S20, in the step S20, six-sided forging is performed on the electroslag ingot after tapping.
Optionally, in the step S40, in the step S40, the fourth preset time is set as T1The thickness of the forging is t1(ii) a The first time coefficient is V1(ii) a The following relation is satisfied:
T1＝V1*t1(ii) a Wherein, V1The range of (A) is 0.5min/mm to 0.75 min/mm.
Optionally, in the step S50, the fifth preset time is T2The thickness of the forging is t2(ii) a The second time coefficient is V2(ii) a The following relation is satisfied:
T3＝V2*t2(ii) a Wherein, V2The range of (A) is 1.1min/mm to 1.7 min/mm.
Optionally, in the step S50, the sixth preset time is T3(ii) a The thickness of the forging is t3(ii) a The third time coefficient is V3(ii) a The following relation is satisfied:
T3＝V3*t3(ii) a Wherein, V3The range of (A) is 1.25min/mm to 2 min/mm.
Optionally, in the step S50, the forging is cooled to a temperature of 0-30 ℃ above the Ar1 line, and the cooling rate of the forging is 20-40 ℃/h.
Optionally, in step S60, after the forging is heated to 1020 to 1060 ℃, after the forging is kept warm for a period of time, the forging is cooled by oil quenching, and then 3 times of tempering treatment are performed, where the tempering temperature of 3 times is in a range of 535 to 635 ℃, and the tempering temperature of 3 times is sequentially decreased.
Optionally, in the step S60, the tempering treatment is performed 3 times, the temperature of the 3 times of tempering is within 535 to 635 ℃, and the temperature of the 3 times of tempering is sequentially decreased.
Optionally, in the tempering treatment for 3 times, a cryogenic treatment process is added between the tempering treatment for the second time and the tempering treatment for the third time.
One or more technical schemes in the heat treatment process of the hot working die steel provided by the invention have at least one of the following technical effects: the electroslag ingot which is remelted by electroslag and in a red hot state is directly subjected to heat preservation, the temperature of the electroslag ingot is high at the moment, the solidification latent heat in the electroslag ingot can be directly utilized, the high-temperature diffusion homogenization in the electroslag ingot is realized, meanwhile, the forging piece is cooled and subjected to heat preservation by utilizing the waste heat in the forging piece after the forging is completed, so that the recovery of deformed austenite is inhibited, the complete nucleation of dislocation of a deformed structure of the forging piece after the forging is ensured to the greatest extent, the recrystallization texture is relatively uniform, coarse grains and a network structure formed by the segregation of carbide are inhibited, and a relatively uniform preparation structure is provided for the subsequent tissue refinement, so that the performance of the forging piece can be effectively improved; according to the heat treatment process of the hot work die steel, the high-temperature diffusion homogenization inside the electroslag ingot is realized by utilizing the solidification latent heat inside the electroslag ingot, and the refined crystal grain pre-heat treatment is carried out by utilizing the self waste heat of the forge piece, so that an external heat source is not needed or only a small amount of external supplementary heat is needed, and the purpose of saving energy is achieved; the heat treatment process of the hot work die steel does not need annealing treatment on the electroslag ingot which is in a red hot state after electroslag remelting and complete cooling of the forged piece after forging, can also greatly reduce the production time and improve the production efficiency; the electroslag ingot in a red hot state after electroslag remelting has high temperature, so that the electroslag ingot can reach higher temperature more easily in the subsequent heating process, and at the high temperature, carbide in the electroslag ingot is better dissolved, the internal structure distribution of the electroslag ingot is more uniform, the performance of the electroslag ingot is greatly improved, the isotropic performance and the service life of a subsequently obtained forge piece can be effectively improved, and the problems of short service period and early failure of the existing tool and die made of the hot work die steel are solved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a flowchart of a high-temperature homogenization treatment of a heat treatment process of hot work die steel according to an embodiment of the present invention.
FIG. 2 is a cooling flow chart of a forging in grain refinement treatment of a heat treatment process of hot work die steel according to an embodiment of the present invention.
Fig. 3 is a flowchart of six-side forging of a heat treatment process of a hot work die steel according to an embodiment of the present invention.
Fig. 4 is a flowchart of thermal refining of a heat treatment process of a hot work die steel according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
In the description of the present invention, it is to be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships illustrated in the drawings, and are used merely for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
As shown in fig. 1 to 2, in an embodiment of the present invention, a heat treatment process for hot work die steel is provided, which specifically includes the following steps:
s10, high-temperature homogenization treatment: directly conveying the electroslag ingot which is subjected to electroslag remelting and in a red hot state into a forging heating furnace, preserving heat within first preset time, heating to first preset temperature, and preserving heat within second preset time, wherein the first preset temperature is less than or equal to 120 ℃ below a solidus line; specifically, referring to fig. 1, the temperature of the electroslag ingot which is remelted by the electroslag and in a red hot state is higher than 600 ℃, then the electroslag ingot is directly sent into a forging heating furnace, the heating is carried out within a first preset time, the electroslag ingot is heated to a temperature lower than 120 ℃ below a solidus line according to a proper heating speed, wherein the heating speed is higher than or equal to 50 ℃/h, then the heating is carried out within a second preset time, the carbide segregation can be fully diffused through the heat treatment in the process, the segregation of alloy elements in steel is remarkably improved, the form, the size and the quantity distribution of liquated carbide are reduced and improved, and the purposes of dissolving and homogenizing the carbide are achieved.
S20, forging: adjusting the heat preservation temperature of the electroslag ingot to a second preset temperature, preserving heat for 2-4 h, discharging, and directly forging the discharged electroslag ingot, wherein the second preset temperature is less than or equal to 200 ℃ below a solidus line; specifically, the heat preservation temperature of the electroslag ingot is adjusted to be below the solidus line and kept at 200 ℃ for 2h, 2.5h, 3h, 3.5h or 4 h.
S30, grain refining treatment: sending the forged piece to a heat treatment workshop for alternately and rapidly cooling by water, air and water until the temperature of the forged piece is cooled to 400-500 ℃, and then putting the forged piece into a 650 ℃ heating furnace for heat preservation; specifically, referring to fig. 2, the rapid cooling and heat preservation of the forged piece can inhibit the recovery of the deformed austenite, ensure the sufficient nucleation of the deformed structure dislocation after forging as much as possible, ensure the uniform recrystallization structure, inhibit the coarse grains and the network structure formed by the segregation of carbides, and provide a uniform preparation structure for the subsequent structure refinement.
S40, ultra-fining treatment: heating the forged piece to 850 ℃, preserving heat within a third preset time, heating the forged piece to 1030-1060 ℃, preserving heat within a fourth preset time, discharging, cooling with water quenching oil, cooling the forged piece to below 350 ℃, and then sending the forged piece into an annealing furnace; specifically, after the forging is subjected to superfine treatment, crystal grains and carbides inside the forging can be further refined, so that the structure in the forging is finer and more uniform, and the performance of the forging is effectively improved. More specifically, the forging is heated to 1030 ℃, 1040 ℃, 1050 ℃, or 1060 ℃.
Further, setting a third preset time as T5Then; in this step, the thickness of the forging is t5(ii) a The fourth time coefficient is V5(ii) a The following relation is satisfied: t is5＝V5*t5Wherein V is5Is 2 min/mm. The meaning of the fourth time coefficient means that V needs to be increased for every 1mm increase of the thickness of the forging4For example: the thickness of the forging piece is 200mm, and the temperature is kept for 400 min; in step S40, according to the thickness t of different forgings5Thereby ensuring the heat preservation time T of the corresponding forge piece5Therefore, different forgings can be guaranteed to have good performance.
S50, spheroidizing annealing heat treatment: heating the forge piece to a temperature of 10-30 ℃ above an AC1 line, preserving heat within a fifth preset time, cooling the forge piece to a temperature of 0-30 ℃ above an Ar1 line, preserving heat within a sixth preset time, cooling the forge piece to a temperature below 350 ℃, discharging the forge piece out of the furnace, and air cooling to room temperature; specifically, the forging is heated to 10 ℃, 15 ℃, 20 ℃, 25 ℃ or 30 ℃ above the AC1 line; and cooling the forging to 0 ℃, 10 ℃, 20 ℃ or 30 ℃ above the Ar1 line.
S60, hardening and tempering: heating the forging to 1020-1060 ℃, preserving heat within seventh preset time, cooling by adopting oil quenching, and then tempering. Specifically, the forging is heated to 1020 ℃, 1030 ℃, 1040 ℃, 10501 ℃ or 1060 ℃.
According to the heat treatment process of the hot working die steel, the electroslag ingot which is remelted by electroslag and is in a red hot state is directly subjected to heat preservation, the temperature of the electroslag ingot is high at the moment, the solidification latent heat in the electroslag ingot can be directly utilized, the high-temperature diffusion homogenization inside the electroslag ingot is realized, meanwhile, the forging is cooled and subjected to heat preservation by utilizing the waste heat inside the forging after the forging is completed, so that the recovery of deformed austenite is inhibited, the sufficient nucleation of dislocation of a deformed structure of the forging is ensured as much as possible, the recrystallization structure is relatively uniform, coarse grains and a network structure formed by carbide segregation are inhibited, and a relatively uniform preparatory structure is provided for the subsequent structure refinement, so that the performance of the forging can be effectively improved; according to the heat treatment process of the hot work die steel, the high-temperature diffusion homogenization inside the electroslag ingot is realized by utilizing the solidification latent heat inside the electroslag ingot, and the refined crystal grain pre-heat treatment is carried out by utilizing the self waste heat of the forge piece, so that an external heat source is not needed or only a small amount of external supplementary heat is needed, and the purpose of saving energy is achieved; the heat treatment process of the hot work die steel does not need annealing treatment on the electroslag ingot which is in a red hot state after electroslag remelting and complete cooling of the forged piece after forging, can also greatly reduce the production time and improve the production efficiency; the electroslag ingot in a red hot state after electroslag remelting has high temperature, so that the electroslag ingot can reach higher temperature more easily in the subsequent heating process, and at the high temperature, carbide in the electroslag ingot is better dissolved, the internal structure distribution of the electroslag ingot is more uniform, the performance of the electroslag ingot is greatly improved, the isotropic performance and the service life of a subsequently obtained forge piece can be effectively improved, and the problems of short service period and early failure of the existing tool and die made of the hot work die steel are solved.
In another embodiment of the present invention, there is provided the step S10 of the heat treatment process of the hot work die steel: the first preset time ranges from 6h to 9 h. Specifically, the first preset time can be 6h, 6.5h, 7h, 7.5h, 8h, 8.5h or 9h, and after the heat preservation within the range, the temperature of the electroslag ingot is uniformly diffused inside, so that preparation is provided for subsequent heating, and cracks caused by uneven temperature distribution are prevented.
In another embodiment of the present invention, there is provided the step S10 of the heat treatment process of the hot work die steel: the second preset time is less than or equal to 36 h. Specifically, the second preset time can be 10h, 15h, 20h, 25h, 30h, 35h or 36h, and the heat preservation time within the range can ensure that the temperature distribution in the electroslag ingot is uniform, so that the carbide segregation in the electroslag ingot is fully diffused, the segregation of alloy elements in steel is obviously improved, the form, size and quantity distribution of liquated carbide are reduced and improved, and the purpose of dissolving and homogenizing the carbide is achieved; if the heat preservation time is too long, the energy consumption is large.
In another embodiment of the present invention, there is provided a heat treatment process of the hot work die steel, in which the discharged electroslag ingot is directly forged into six sides in step S20. Specifically, six-face forging adopts wide anvil, large pressing, upsetting and drawing-out in three directions and multi-fire-number strong forging technology, the final forging temperature is more than or equal to 820 ℃, and the isotropic performance of a finished product is promoted to be more than or equal to 0.85.
More specifically, referring to fig. 3, the three directions of the electroslag ingot are a direction, a direction and a direction, and the multidirectional forging process includes upsetting the electroslag ingot along the direction a, then horizontally drawing the electroslag ingot along the direction B, upsetting the electroslag ingot along the direction a, horizontally drawing the electroslag ingot along the direction C, and upsetting the electroslag ingot along the direction C to obtain a finished product of the forged piece.
In another embodiment of the present invention, there is provided the heat treatment process for the hot work die steel, wherein in step S40, the fourth predetermined time is T1Thickness of forging is t1(ii) a The first time coefficient is V1(ii) a The following relation is satisfied: t is1＝V1*t1Wherein V is1The range of (A) is 0.5min/mm to 0.75 min/mm. In particular, V1Can be 0.5min/mm, 0.55min/mm, 0.6min/mm, 0.65min/mm, 0.7min/mm or 0.75 min/mm; wherein, the first time coefficient means that V needs to be increased every 1mm of the thickness of the forging1For example: the thickness of the forging piece is 200mm, and the heat preservation time is 100-150 min; in step S40, according to the thickness t of different forgings1Thereby ensuring the corresponding forgingThermal insulation T1Therefore, the internal structures of different forgings can be well thinned; wherein, V1The specific numerical value can be set according to actual production needs, and the internal structure of the forge piece is ensured to be well refined.
In another embodiment of the present invention, there is provided the heat treatment process for the hot work die steel, wherein in step S50, the fifth predetermined time is T2Thickness of forging is t2(ii) a The second time coefficient is V2(ii) a The following relation is satisfied: t is2＝V2*t2Wherein V is2The range of (A) is 1.1min/mm to 1.7 min/mm. In particular, V2Can be 1.1min/mm, 1.2min/mm, 1.3min/mm, 1.4min/mm, 1.5min/mm, 1.6min/mm or 1.7min/mm, wherein the meaning of the second time coefficient means that V needs to be increased for every 1mm increase in the thickness of the forging2For example: the thickness of the forging piece is 200mm, and the heat preservation time is 220-340 min; in step S50, according to the thickness t of different forgings3Thereby ensuring the heat preservation time T of the corresponding forge piece2Therefore, the internal structures of different forgings can be well thinned; wherein, V2The specific numerical value can be set according to actual production needs, and the internal structure of the forge piece is ensured to be well refined.
In another embodiment of the present invention, there is provided the heat treatment process for the hot work die steel, wherein in step S50, the sixth predetermined time is T3Then; thickness of forging is t3(ii) a The third time coefficient is V3(ii) a The following relation is satisfied: t is3＝V3*t3Wherein V is3The range of (A) is 1.25min/mm to 2 min/mm. In particular, V3Can be 1.25min/mm, 1.3min/mm, 1.4min/mm, 1.5min/mm, 1.6min/mm, 1.7min/mm, 1.8min/mm, 1.9min/mm or 2min/mm, wherein the meaning of the third time coefficient means that V needs to be increased for every 1mm of the thickness of the forging3For example: the thickness of the forging piece is 200mm, and the heat preservation time is 250-400 min; in step S50, according to the thickness t of different forgings3Thereby ensuringGuarantee the holding time T of corresponding forging3Therefore, the internal residual stress of different forgings can be completely eliminated, and the tissue defect is avoided; wherein, V3The specific numerical value can be set according to actual production needs, and the internal structure of the forge piece is ensured to be well refined.
In another embodiment of the invention, in the step S50, the forging is cooled to 0-30 ℃ above the Ar1 line, and the cooling speed of the forging is 20-40 ℃/h. After the forging is processed in the process, the carbide and the grain size in the forging are further refined, the structure is converted into the balanced structure of pearlite and the carbide, and the hardness and the impact toughness of the forging are effectively improved.
In another embodiment of the present invention, referring to fig. 4, there is provided the heat treatment process of the hot work die steel in which the tempering treatment is performed 3 times, the temperature of the 3 tempering treatments is within 535 to 635 ℃, and the temperature of the 3 tempering treatments is sequentially decreased in step S60. Specifically, after the forging is subjected to oil quenching and cooling for a seventh preset time and 3 times of tempering treatment, the structure of the forging is converted into a balanced structure of fine pearlite and carbide, crystal grains and carbide are further refined, the structure inside the forging is converted into small grains which are uniformly distributed, fine granular globular carbide is dispersed and precipitated, and the method plays a positive role in prolonging the service life of a tool and a die made of the hot work die steel.
Further, setting the seventh preset time as T4Then; thickness of forging is t4(ii) a The third time coefficient is V4(ii) a The following relation is satisfied: t is4＝V4*t4Wherein V is4The range of (A) is 0.6min/mm to 0.85 min/mm. In particular, V3Can be 0.6min/mm, 0.65min/mm, 0.7min/mm, 0.75min/mm, 0.8min/mm or 0.85min/mm, wherein the meaning of the third time coefficient means that V needs to be increased for every 1mm increase of the thickness of the forging4For example: the thickness of the forging piece is 200mm, and the heat preservation time is 120-170 min; in step S60, according to the thickness t of different forgings4Thereby ensuring the heat preservation time T of the corresponding forge piece4Therefore, different forgings can be guaranteed to have good performance.
In another embodiment of the present invention, referring to fig. 4, there is provided a method of increasing a cryogenic treatment process between the second tempering treatment and the third tempering treatment in 3 tempering treatments of the heat treatment process of the hot work die steel. Specifically, oil cooling for more than or equal to 15 hours for the first time, oil cooling for more than or equal to 15 hours for the second time and air cooling for more than or equal to 15 hours for the third time are carried out by 3 times of tempering treatment; a primary deep cooling treatment process is added between the second oil cooling and the third air cooling, so that the decomposition and transformation of residual austenite in the forge piece can be promoted, and carbide is promoted to be spheroidized, fine and dispersed and separated out.
After the process is adopted, the metallographic structure of the hot work die steel is uniform and fine, and the carbide is in a spherical shape and is finely dispersed and separated out. Under the condition of the same hardness, the unnotched impact energy of the sample of the tool and die body is more than or equal to 350J, and the notched impact energy is more than or equal to 20J; the equal directional performance is more than or equal to 0.85, and the equal directional performance, the toughness, the impact performance, the service life and other important indexes of the tool and the die are obviously improved.
The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A heat treatment process of hot work die steel is characterized by comprising the following steps:
s10, high-temperature homogenization treatment: directly conveying an electroslag ingot which is subjected to electroslag remelting and is in a red hot state into a forging heating furnace, preserving heat within first preset time, heating to first preset temperature, and preserving heat within second preset time, wherein the first preset temperature is less than or equal to 120 ℃ below a solidus line;
s20, forging: adjusting the heat preservation temperature of the electroslag ingot to a second preset temperature, preserving heat for 2-4 hours, discharging, and directly forging the discharged electroslag ingot, wherein the second preset temperature is less than or equal to 200 ℃ below a solidus line;
s30, grain refining treatment: sending the forged forging piece to a heat treatment workshop for alternately and rapidly cooling by water, air and water until the temperature of the forging piece is cooled to 400-500 ℃, and then putting the forging piece into a 650 ℃ heating furnace for heat preservation;
s40, ultra-fining treatment: heating the forged piece to 850 ℃, preserving heat for a third preset time, heating the forged piece to 1030-1060 ℃, preserving heat for a fourth preset time, discharging, performing water quenching and oil cooling until the temperature of the forged piece is cooled to below 350 ℃, and then sending the forged piece into an annealing furnace;
s50, spheroidizing annealing heat treatment: heating the forge piece to a temperature of 10-30 ℃ above an AC1 line, preserving heat within a fifth preset time, cooling the forge piece to a temperature of 0-30 ℃ above an Ar1 line, preserving heat within a sixth preset time, cooling the forge piece to a temperature below 350 ℃, discharging the forge piece out of the furnace, and air cooling to room temperature;
s60, hardening and tempering: and heating the forging to 1020-1060 ℃, preserving heat within seventh preset time, cooling by adopting oil quenching, and then tempering.
2. The heat treatment process for hot work die steel according to claim 1, wherein in the step S10: the first preset time ranges from 6h to 9 h.
3. The heat treatment process for hot work die steel according to claim 1, wherein in the step S10: the second preset time is less than or equal to 36 h.
4. The heat treatment process for hot work die steel according to claim 1, wherein in step S20, six-sided forging is performed on the electroslag ingot after tapping.
5. The heat treatment process for hot work die steel according to any one of claims 1 to 4, wherein the heat treatment process is carried out in a hot work die steelIn the step S40, the fourth preset time is T1The thickness of the forging is t1(ii) a The first time coefficient is V1(ii) a The following relation is satisfied:
T1＝V1*t1(ii) a Wherein, V1The range of (A) is 0.5min/mm to 0.75 min/mm.
6. The heat treatment process for hot work die steel according to any one of claims 1 to 4, wherein in the step S50, the fifth predetermined time is T2The thickness of the forging is t2(ii) a The second time coefficient is V2(ii) a The following relation is satisfied:
T3＝V2*t2(ii) a Wherein, V2The range of (A) is 1.1min/mm to 1.7 min/mm.
7. The heat treatment process for hot work die steel according to any one of claims 1 to 4, wherein in the step S50, the sixth predetermined time is T3(ii) a The thickness of the forging is t3(ii) a The third time coefficient is V3(ii) a The following relation is satisfied:
T3＝V3*t3(ii) a Wherein, V3The range of (A) is 1.25min/mm to 2 min/mm.
8. The heat treatment process for the hot work die steel according to any one of claims 1 to 4, wherein in the step S50, the forging is cooled to a temperature within a range of 0 ℃ to 30 ℃ above the Ar1 line, and the cooling rate of the forging is 20 ℃/h to 40 ℃/h.
9. The heat treatment process for hot-work die steel according to any one of claims 1 to 4, wherein in the step S60, the tempering treatment is performed 3 times, the temperature of the 3 times of tempering is within 535 to 635 ℃, and the temperature of the 3 times of tempering is decreased in sequence.
10. The heat treatment process of hot work die steel according to claim 9, wherein a cryogenic treatment process is added between the second tempering and the third tempering in 3 times of the tempering treatment.
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