CN111270051A - Heat treatment composite process and die steel thereof - Google Patents
Heat treatment composite process and die steel thereof Download PDFInfo
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- CN111270051A CN111270051A CN202010276191.XA CN202010276191A CN111270051A CN 111270051 A CN111270051 A CN 111270051A CN 202010276191 A CN202010276191 A CN 202010276191A CN 111270051 A CN111270051 A CN 111270051A
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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
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
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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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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/24—Nitriding
- C23C8/26—Nitriding of ferrous surfaces
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
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Abstract
The invention provides a heat treatment composite process and die steel thereof, which comprises the following steps: s1 tissue pretreatment: the method is characterized in that a tissue pretreatment method is used before the die steel raw material leaves a factory, and the tissue pretreatment method comprises the following steps: the first stage is as follows: heating a die steel raw material to 550 ℃ in a vacuum environment, preserving heat for 30 minutes, heating to 850 ℃ and preserving heat for 60 minutes, continuously heating the die steel raw material to 1150 ℃ and preserving heat for 60 minutes, introducing liquid nitrogen into the die steel raw material in the vacuum environment, and quenching the heated die steel raw material after the liquid nitrogen is gasified; and a second stage: heating the die steel raw material obtained after the treatment of the previous procedure to 720 ℃ in a vacuum environment, preserving the heat for 60 minutes, and then tempering to room temperature; s2 quenching in a conventional manner; s3: and (4) placing the die steel raw material obtained by the treatment of the step S2 in a low-temperature environment of-150 ℃ to-200 ℃ for 15-24 hours for super-deep cooling treatment. The heat treatment process can prolong the service life of the die steel.
Description
Technical Field
The invention relates to the technical field of metal heat treatment, in particular to a heat treatment composite process and die steel thereof.
Background
The hot work die steel requires the material to have high hardenability, high temperature strength, high wear resistance, high toughness, high hot cracking resistance, high melting loss resistance and the like.
The H13 steel is the most widely used and representative hot work die steel/die casting die steel, and because the structure and the components of H13 are greatly different at home and abroad, but the heat treatment process is not modified according to the components of the domestic H13, the defects of the domestic H13 are not improved all the time, and the service life of the die casting die is short. According to the introduction of the relevant information, the average service life of the Japanese aluminum alloy die-casting die is about 11 ten thousand times, and the service life of the aluminum alloy die-casting die manufactured by Sweden 8407 reaches 20 ten thousand times. In contrast, the average service life of the aluminum alloy die-casting mold in China is only 6 ten thousand times, the highest service life of the die-casting mold made of the domestic H13 steel is 6 ten thousand times, and the worst die-casting mold is invalid only for thousands of times. Although the market of die-casting moulds in China is large, and the market demand of H13 steel is also large, the mould steel usually needs to be imported, sometimes even the whole mould is imported due to the quality problem of domestic H13 steel. Refusing to complete statistics, China imports up to 6 million tons of various die steels from Sweden, Japan, Germany and other countries every year.
The improvement of the internal structure and the component distribution of the die steel is a fundamental way for improving the service performance of the die and prolonging the service life of the die. The method is a system engineering which relates to various links of smelting, hot working, pre-heat treatment, final quenching and tempering, surface treatment and the like of die steel.
The main defects of the current hot work die steel for die casting include coarse primary carbides M7C3, M23C6, MC and uneven distribution of carbon and alloy components caused by segregation of alloy carbides. These defects can only be ameliorated by heat treatment after shipment, which is also a necessary treatment prior to mold production. Heat treatment enterprises at the present stage adopt fixed quenching and tempering temperatures, the floating interval is within 20 ℃, and the temperature is carefully regulated. This is because the die-casting mold requires strength and toughness to be balanced, and the temperature adjustment is too large, so that the two contradictory properties of strength and toughness are out of balance, and the early failure of the mold occurs. However, in order to improve the defects left after electroslag remelting and forging of die steel, the quenching temperature at the present stage must be increased to increase the diffusion rate of the alloy in austenite, which leads to increase of austenite grains, increase of strength and reduction of plastic toughness.
In view of the foregoing, there is a need for a thermal process that solves the above problems.
Disclosure of Invention
The invention aims to solve the problem that the service life of a die-casting die is short due to the fact that the existing domestic hot-work die steel comprises coarse primary carbides and carbon and alloy components are not uniformly distributed due to segregation of alloy carbides, and provides a heat treatment composite process and die steel thereof aiming at the defects in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
a heat treatment composite process comprises the following steps:
s1 tissue pretreatment: before the die steel raw material leaves a factory, a structure pretreatment method is used for improving the structure of the die steel raw material before quenching, and the structure pretreatment method comprises the following steps:
the first stage is as follows: heating a die steel raw material to 550 ℃ in a vacuum environment, preserving heat for 30 minutes, then heating to 850 ℃ and preserving heat for 60 minutes, continuing to heat the die steel raw material to 1150 ℃ and preserving heat for 60 minutes, introducing liquid nitrogen into the die steel raw material in the vacuum environment, and quenching the heated die steel raw material after the liquid nitrogen is gasified;
and a second stage: heating the die steel raw material obtained after the treatment of the previous procedure to 720 ℃ in a vacuum environment, preserving the heat for 60 minutes, and then tempering to room temperature;
s2 quenching in a conventional manner;
s3: and (4) placing the die steel raw material obtained by the treatment of the step S2 in a low-temperature environment of-150 ℃ to-200 ℃ for 15-24 hours for super-deep cooling treatment.
Further, the ultra-deep cooling process in step S2 includes the steps of: the die steel material obtained in S2 was subjected to extreme cold treatment at a temperature of-190 ℃ for 20 hours.
Further, the conventional quenching in step S2 mainly includes:
the first stage is as follows: heating the die steel raw material obtained after the treatment of the previous procedure to 550 ℃ in a vacuum environment, preserving heat for 30 minutes, heating to 850 ℃ and preserving heat for 60 minutes, continuing to heat to 1030 ℃ and preserving heat for 60 minutes, introducing liquid nitrogen into the die steel raw material in the vacuum environment, and quenching the heated die steel raw material after the liquid nitrogen is gasified;
and a second stage: heating the die steel raw material obtained after the treatment of the previous procedure to 600 ℃ in a vacuum environment, preserving the heat for 60 minutes, and finally cooling to room temperature.
Further, the specific steps of introducing liquid nitrogen into the raw material of the die steel in a vacuum environment comprise:
(1) preparing a workpiece before nitriding: putting the die steel workpiece into acid for a period of time by using an iron hook, polishing the die steel workpiece by using sand paper after taking out the die steel workpiece, washing the die steel workpiece, soaking the die steel workpiece in water for 10 minutes, wiping the discharged water by using cloth, soaking the discharged water in alcohol, and finally taking out the alcohol for drying;
(2) framing: the workpiece is molded into a workpiece frame according to the size, the workpiece is reinforced by metal wires, the workpiece frame is hoisted into a furnace by a hoisting machine, and a pressure handle of an oil drain valve is compressed;
(3) nitriding:
1) setting ammonia gas concentration at 1-1.5Mpa, opening pressure reducing valve at 0.8-0.12 Mpa;
2) setting the temperature according to the process requirements;
3) in the nitriding process, the supply of cooling water is ensured;
(4) cooling: and (4) closing the temperature rising switch after the nitridation is finished, reducing the ammonia flow and the pressure in the furnace, opening the air blower after half an hour, and opening the air inlet and the air outlet.
(5) Discharging: and (3) cooling the temperature in the furnace to below 180 ℃, closing the ammonia gas main valve, loosening the pressing handle, opening the furnace cover, hanging out the die frame by using a crane, and taking down the sample after cooling to below 50 ℃.
The die steel is prepared by the heat treatment composite process.
Compared with the prior art, the invention has the following beneficial effects:
(1) the structure pretreatment is added, so that on the premise of ensuring the strength, hardness and plasticity of the die-casting die steels H13 and 1.2344, the toughness is improved, the method is very favorable for reducing the risks of cracking failure and thermal fatigue crack failure, the thermal stability of the die steel can be improved by the mode of the structure pretreatment and the conventional quenching, and the method has a positive effect on improving the melting loss resistance and the thermal fatigue resistance of the die;
(2) the high-temperature tissue pretreatment can promote the dissolution of alloy carbide, improve the segregation of alloy elements and carbon and improve the thermal stability of the die steel. This also leads to an increase in the lath martensite content and improved mechanical properties. In addition, the more uniform structure of the lath martensite relative to the acicular martensite makes the structure preparation for uniform precipitation of carbides in the subsequent tempering process;
(3) the structure pretreatment and the conventional quenching mode are adopted, the length rule of the austenite heated by the unbalanced structure appears in the heating process of the second refined grain quenching, the grains are refined, the grain boundary effect appears, and the quenched martensite still retains the orientation of the first quenched martensite. The majority of lath martensite is obtained and arranged in the orientation of coarse martensite within the coarse prior austenite grains of the first quench, but the laths of martensite are significantly refined. The structure can improve the resistance of thermal fatigue crack propagation, prolong the service life of die steel, and eliminate the problems of uneven structure components and segregation of some short plates of the die-casting die steel at the present stage and larger impurities and alloy carbides existing in grain boundaries;
(4) the comprehensive mechanical property of the material is improved by the ultra-deep cooling treatment in three aspects: the toughness of the material is improved, the impact toughness is high, and the tempering resistance stability and the fatigue resistance of the matrix are improved; meanwhile, the wear resistance is improved; the dimensional stability is improved. Thereby achieving the purposes of strengthening the matrix, improving the heat treatment quality, reducing the tempering times and prolonging the service life of the die. The internal thermal stress and mechanical stress of the material are greatly reduced after cryogenic treatment, and the micropore or stress concentration part generates plastic rheology in the cooling process, and the pressure stress can be generated on the surface of the micropore or stress concentration part in the heating process, so that the damage of the defect to the local performance of the workpiece can be greatly reduced, and the possibility of deformation and cracking of the metal workpiece is effectively reduced.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Drawings
FIG. 1 is a time-temperature graph of tissue pretreatment and conventional quenching according to the present invention.
Detailed Description
In order to make the technical means, the creation characteristics, the achievement purposes and the functions of the invention clearer and easier to understand, the invention is further explained by combining the drawings and the detailed implementation mode:
examples 1 to 5 used die-casting die steel H13 (hereinafter referred to as H13) as the test subject, and the conditions were the same except for the processing technique, and examples 6 to 10 used hot-working die steel 1.2344 (hereinafter referred to as 1.2344) as the test subject, and the conditions were the same except for the processing technique. Wherein die-casting die steel H13 and hot-work die steel 1.2344 were manufactured into dies using the processes in tables to test the life and the retained austenite percentage of each die steel as detailed in tables 1 and 2.
TABLE 1 EXAMPLES 1-5, model number die casting die Steel H13
Table 2 examples 6-10, type hot work die steel 1.2344
In tables 1 and 2, the heat treatment composite process mainly includes the following steps as shown in fig. 1, and specifically, the processing process in the tables is shown as follows:
s1 tissue pretreatment: prior to shipment of H13, a tissue pretreatment process is used to improve the pre-quenched tissue of H13 raw material, said tissue pretreatment process comprising the steps of:
the first stage is as follows: heating a die steel raw material to 550 ℃ in a vacuum environment, preserving heat for 30 minutes, then heating to 850 ℃ and preserving heat for 60 minutes, continuing to heat the die steel raw material to 1150 ℃ and preserving heat for 60 minutes, introducing liquid nitrogen into the die steel raw material in the vacuum environment, and quenching the heated die steel raw material after the liquid nitrogen is gasified;
and a second stage: heating the die steel raw material obtained after the treatment of the previous procedure to 720 ℃ in a vacuum environment, preserving the heat for 60 minutes, and then tempering to room temperature; the effect of the structure pretreatment is that the problems of the short plates H13 in the prior stage, such as the phenomena of uneven structure components and segregation, and the existence of larger impurities and alloy carbides in grain boundaries, can be eliminated;
s2 conventional quenching, the first stage: heating the die steel raw material obtained after the treatment of the previous step S1 from room temperature to 550 ℃ in a vacuum environment, preserving heat for 30 minutes, heating to 850 ℃ and preserving heat for 60 minutes, continuing to heat to 1030 ℃ and preserving heat for 60 minutes, introducing liquid nitrogen into the die steel raw material in the vacuum environment, gasifying the liquid nitrogen, and quenching the heated die steel raw material;
and a second stage: heating the die steel raw material obtained after the treatment of the previous procedure to 600 ℃ in a vacuum environment, preserving the heat for 60 minutes, and finally cooling to room temperature, wherein the conventional quenching is a conventional quenching process in the prior art, and the details are not repeated herein;
s3: and (4) placing the die steel raw material obtained by the treatment of the step S2 in a low-temperature environment of-150 ℃ for 15 hours for ultra-deep cooling treatment. The H13 is quenched twice, so that the toughness is improved on the premise of ensuring the strength, hardness and plasticity of the die-casting die steel H13, and the quenching die steel is very beneficial to reducing the risks of cracking failure and thermal fatigue crack failure;
s3: and (4) placing the die steel raw material obtained by the treatment of the step S2 in a low-temperature environment of-150 ℃ to-200 ℃ for 15-24 hours for super-deep cooling treatment. The ultra-deep cooling treatment converts the residual austenite with lower hardness into a harder, more stable martensite with higher wear resistance and heat resistance, the grain boundary edge and the inside of the grain boundary of the martensite are partially decomposed and refined to separate out a large amount of ultra-fine carbides, the supersaturation degree of the supersaturated martensite is reduced in the deep cooling process, the separated ultra-fine carbides keep a coherent relationship with a matrix, the lattice distortion of the martensite can be reduced, the micro stress is reduced, and the fine dispersed carbides can block the dislocation motion when the material is plastically deformed, so that the matrix structure is strengthened; meanwhile, because ultrafine carbides are precipitated and uniformly distributed on a martensite matrix, the grain boundary catalysis effect is weakened, and the refinement of the matrix structure not only weakens the segregation degree of impurity elements in the grain boundary, but also plays a role in strengthening the grain boundary.
Further, the specific steps of introducing liquid nitrogen into the raw material of the die steel in a vacuum environment comprise:
(1) preparing a workpiece before nitriding: putting the die steel workpiece into acid for a period of time by using an iron hook, polishing the die steel workpiece by using sand paper after taking out the die steel workpiece, washing the die steel workpiece, soaking the die steel workpiece in water for 10 minutes, wiping the discharged water by using cloth, soaking the discharged water in alcohol, and finally taking out the alcohol for drying;
(2) framing: the workpiece is molded into a workpiece frame according to the size, the workpiece is reinforced by metal wires, the workpiece frame is hoisted into a furnace by a hoisting machine, and a pressure handle of an oil drain valve is compressed;
(3) nitriding:
1) setting ammonia gas concentration at 1-1.5Mpa, opening pressure reducing valve at 0.8-0.12 Mpa;
2) setting the temperature according to the process requirements;
3) in the nitriding process, the supply of cooling water is ensured;
(4) cooling: and (4) closing the temperature rising switch after the nitridation is finished, reducing the ammonia flow and the pressure in the furnace, opening the air blower after half an hour, and opening the air inlet and the air outlet.
(5) Discharging: and (3) cooling the temperature in the furnace to below 180 ℃, closing the ammonia gas main valve, loosening the pressing handle, opening the furnace cover, hanging out the die frame by using a crane, and taking down the sample after cooling to below 50 ℃. And the workpiece can be rapidly cooled in a short time by introducing liquid nitrogen.
The following analyses of the differences between the examples of the invention:
in table 1, examples 1 to 5 are H13 type die steels, examples 1 and 6 were subjected to only conventional quenching treatment, the die made of H13 used about 1500 times for breakage, the die made of 1.2344 used about 1600 times for breakage, and the retained austenite AR (unit%) of the two groups of examples 1 and 6 were 12 and 11, respectively, and the two groups were used as a control group.
The example 2 and the example 7 adopt the process of the structure pretreatment and the conventional quenching, the service lives of two groups are 2000 and 2900 pieces respectively, and compared with the example 1 and the example 6, the service life of the die steel after the structure pretreatment is greatly improved under the condition of the same other conditions.
Examples 3 and 8 were subjected to conventional quenching and ultra-deep cooling treatment in a low temperature environment of-150 ℃ for 15 hours, and the two groups of lives were 2500 and 2600 pieces respectively, compared with examples 1 and 6, the ultra-deep cooling treated H13 and 1.2344 die steels had residual austenite AR (unit%) of 12 and 11 respectively in the die steel structures of examples 4 and 9 under the same conditions, and the lives were greatly improved after comparison.
Examples 4 and 9 adopt a metal treatment mode of structure pretreatment, conventional quenching and ultra-deep cooling treatment in a low-temperature environment of-150 ℃ for 15 hours, wherein the service lives of two groups are 3000 and 3100 pieces respectively, compared with examples 1 and 6, H13 and 1.2344 die steels subjected to ultra-deep cooling treatment in a low-temperature environment of-150 ℃ for 15 hours respectively have residual austenite AR (unit%) of 1.7 and 1.8 in the die steel structures of examples 4 and 9 under the same other conditions, and the service lives of the die steels after comparison are greatly improved.
In examples 5 and 10, the metal treatment mode of structure pretreatment, conventional quenching and ultra-deep cooling treatment in a low-temperature environment of-200 ℃ for 20 hours is adopted, the service lives of two groups are 3500 pieces and 3600 pieces respectively, compared with examples 1 and 6, H13 and 1.2344 die steels subjected to ultra-deep cooling treatment in a low-temperature environment of-200 ℃ for 20 hours respectively have residual austenite AR (unit%) of 1.5 and 1.6 in the die steel structures of examples 4 and 9 under the same other conditions, and the service lives of the die steels after comparison are greatly improved. This is because the cryogenic treatment makes the structure of H13 and 1.2344 die steel change in three ways:
1) some or all of the retained austenite is transformed into martensite;
2) the structure of the residual part of the retained austenite is relatively stable, and the structure is internally thinned, so that the retained austenite is strengthened and contributes to toughness;
3) the toughness of the material is improved, and the impact toughness is high.
The invention also provides the die steel processed by the heat treatment composite process.
Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.
Claims (5)
1. A heat treatment composite process is characterized by comprising the following steps:
s1 tissue pretreatment: before the die steel raw material leaves a factory, a structure pretreatment method is used for improving the structure of the die steel raw material before quenching, and the structure pretreatment method comprises the following steps:
the first stage is as follows: heating a die steel raw material to 550 ℃ in a vacuum environment, preserving heat for 30 minutes, then heating to 850 ℃ and preserving heat for 60 minutes, continuing to heat the die steel raw material to 1150 ℃ and preserving heat for 60 minutes, introducing liquid nitrogen into the die steel raw material in the vacuum environment, and quenching the heated die steel raw material after the liquid nitrogen is gasified;
and a second stage: heating the die steel raw material obtained after the treatment of the previous procedure to 720 ℃ in a vacuum environment, preserving the heat for 60 minutes, and then tempering to room temperature;
s2 quenching in a conventional manner;
s3: and (4) placing the die steel raw material obtained by the treatment of the step S2 in a low-temperature environment of-150 ℃ to-200 ℃ for 15-24 hours for super-deep cooling treatment.
2. The thermal processing composite process according to claim 1, wherein the ultra-deep cooling treatment in step S3 comprises the following steps: the die steel material obtained in S2 was subjected to extreme cold treatment at a temperature of-190 ℃ for 20 hours.
3. The heat treatment composite process according to claim 1, wherein the conventional quenching in the step S2 mainly comprises:
the first stage is as follows: heating the die steel raw material obtained after the treatment of the previous procedure to 550 ℃ in a vacuum environment, preserving heat for 30 minutes, heating to 850 ℃ and preserving heat for 60 minutes, continuing to heat to 1030 ℃ and preserving heat for 60 minutes, and quenching the heated die steel raw material;
and a second stage: heating the die steel raw material obtained after the treatment of the previous procedure to 600 ℃ in a vacuum environment, preserving the heat for 60 minutes, and finally cooling to room temperature.
4. The heat treatment composite process according to any one of claims 1 to 3, wherein the mold steel raw material is subjected to a nitriding treatment process after step S3, which comprises the specific steps of:
(1) preparing a workpiece before nitriding: putting the die steel workpiece into acid for a period of time by using an iron hook, polishing the die steel workpiece by using sand paper after taking out the die steel workpiece, washing the die steel workpiece, soaking the die steel workpiece in water for 10 minutes, wiping the discharged water by using cloth, soaking the discharged water in alcohol, and finally taking out the alcohol for drying;
(2) framing: the workpiece is molded into a workpiece frame according to the size, the workpiece is reinforced by metal wires, the workpiece frame is hoisted into a furnace by a hoisting machine, and a pressure handle of an oil drain valve is compressed;
(3) nitriding:
1) setting the ammonia concentration at 1-1.5Mpa, opening a pressure reducing valve, and setting the pressure at 0.8-0.12 Mpa;
2) setting the temperature according to the process requirements;
3) in the nitriding process, the supply of cooling water is ensured;
(4) cooling: after the nitridation is finished, closing a temperature rising switch, reducing the ammonia flow and the pressure in the furnace, opening an air blower after half an hour, and opening an air inlet and an air outlet;
(5) discharging: and (3) cooling the temperature in the furnace to below 180 ℃, closing the ammonia gas main valve, loosening the pressing handle, opening the furnace cover, hanging out the die frame by using a crane, and taking down the sample after cooling to below 50 ℃.
5. A die steel, characterized in that the die steel is prepared by the heat treatment composite process of any one of claims 1 to 3.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112458257A (en) * | 2020-11-26 | 2021-03-09 | 广东和胜工业铝材股份有限公司 | Heat treatment process of aluminum profile extrusion die steel |
| CN114150114A (en) * | 2021-11-10 | 2022-03-08 | 广东世创金属科技股份有限公司 | Improved heat treatment method for welded pipe die steel |
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