CN113913733A - Vacuum carburizing heat treatment process for low-carbon high-alloy steel - Google Patents
Vacuum carburizing heat treatment process for low-carbon high-alloy steel Download PDFInfo
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- CN113913733A CN113913733A CN202111178223.3A CN202111178223A CN113913733A CN 113913733 A CN113913733 A CN 113913733A CN 202111178223 A CN202111178223 A CN 202111178223A CN 113913733 A CN113913733 A CN 113913733A
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- 238000005255 carburizing Methods 0.000 title claims abstract description 108
- 238000010438 heat treatment Methods 0.000 title claims abstract description 60
- 238000000034 method Methods 0.000 title claims abstract description 35
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 25
- 229910000851 Alloy steel Inorganic materials 0.000 title claims abstract description 20
- 238000001816 cooling Methods 0.000 claims abstract description 40
- 238000010791 quenching Methods 0.000 claims description 64
- 230000000171 quenching effect Effects 0.000 claims description 64
- 238000004140 cleaning Methods 0.000 claims description 35
- 238000005496 tempering Methods 0.000 claims description 27
- 238000002791 soaking Methods 0.000 claims description 21
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 18
- 238000010583 slow cooling Methods 0.000 claims description 14
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 12
- 229910052757 nitrogen Inorganic materials 0.000 claims description 9
- 239000007789 gas Substances 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 abstract description 9
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 16
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 description 16
- 125000004432 carbon atom Chemical group C* 0.000 description 15
- 238000009792 diffusion process Methods 0.000 description 14
- 229910001566 austenite Inorganic materials 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 8
- 239000010410 layer Substances 0.000 description 8
- 239000004215 Carbon black (E152) Substances 0.000 description 7
- 239000012459 cleaning agent Substances 0.000 description 7
- 238000005238 degreasing Methods 0.000 description 7
- 229930195733 hydrocarbon Natural products 0.000 description 7
- 150000002430 hydrocarbons Chemical class 0.000 description 7
- 238000001514 detection method Methods 0.000 description 6
- 239000002344 surface layer Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 5
- 238000009825 accumulation Methods 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 239000012466 permeate Substances 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 230000008646 thermal stress Effects 0.000 description 3
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000004320 controlled atmosphere Methods 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- 229910001339 C alloy Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
Classifications
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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
- C23C8/20—Carburising
- C23C8/22—Carburising of ferrous surfaces
-
- 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
-
- 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
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
- C21D1/773—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material under reduced pressure or vacuum
-
- 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
- C23C8/80—After-treatment
-
- 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
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F17/00—Multi-step processes for surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by subclass C21D or C22F or class C25
-
- 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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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
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Abstract
The application relates to the field of vacuum heat treatment, and particularly discloses a low-carbon high-alloy steel vacuum carburization heat treatment process, which comprises the following steps: and (3) carburizing: heating the vacuum carburizing furnace with the workpiece to 975-; and repeating the carburizing stage for at least 2 times, and then entering a cooling stage. The vacuum carburization production efficiency is further improved.
Description
Technical Field
The application relates to the field of vacuum heat treatment, in particular to a low-carbon high-alloy steel vacuum carburization heat treatment process.
Background
Carburizing is a common heat treatment process, in which a low-carbon steel or low-carbon alloy steel workpiece is placed in an active carburizing medium, heated to a single-phase austenite region and kept warm for a certain time, and active carbon atoms in the carburizing medium penetrate into the surface layer of the steel workpiece to obtain a workpiece with high carbon on the surface layer and low carbon on the core, so that the surface layer of the workpiece has high hardness and wear resistance, and the core keeps the toughness and plasticity of the low-carbon steel.
The traditional controlled atmosphere carburization is influenced by the performance of equipment, the highest use temperature is 950 ℃, the carburization speed is low, the production efficiency is low, and the workpiece is easy to oxidize, the carburization quality is unstable and the like. In order to improve the quality of carburized workpieces and improve the carburization efficiency, a vacuum carburization technology is produced. The vacuum carburizing equipment can increase the carburizing temperature to 1080 ℃, and can achieve the purpose of accelerating the carburizing speed by increasing the carburizing temperature on the premise of not influencing the use performance of parts. In addition, the quality of vacuum carburization is excellent, the surface of a workpiece is not easy to oxidize or decarbonize, and the depth of a carburized layer is uniform. Therefore, vacuum carburization gradually replaces traditional controlled atmosphere carburization and is increasingly widely applied.
In the actual production process, compared with the controllable atmosphere carburization, the vacuum carburization technology is used for processing the same material, and the time required for achieving the same effective hardened layer depth can be saved by about one third. However, the above vacuum carburization technology still needs to be improved to further improve the production efficiency.
Disclosure of Invention
In order to further improve the production efficiency of vacuum carburization, the application provides a low-carbon high-alloy steel vacuum carburization heat treatment process.
The application provides a low-carbon high-alloy steel vacuum carburizing heat treatment process which adopts the following technical scheme:
a low-carbon high-alloy steel vacuum carburizing heat treatment process is characterized by comprising the following steps:
and (3) carburizing: heating the vacuum carburizing furnace with the workpiece to 975-class 985 ℃, continuously introducing acetylene into the vacuum carburizing furnace, keeping for 17-20min, stopping introducing acetylene, vacuumizing the vacuum carburizing furnace, and keeping for 200-class 210 min;
and repeating the carburizing stage for at least 2 times, and then entering a cooling stage.
By adopting the technical scheme, acetylene is introduced into the vacuum carburizing furnace in stages and is diffused in stages, and compared with primary carburizing-diffusion, the accumulation of carbon atoms on the surface of a workpiece is reduced through the circulation of the carburizing-diffusion step, so that the carbon atoms can permeate into the workpiece in time, the diffusion efficiency of the carbon atoms on the surface layer of the workpiece is improved, and the heat treatment deformation of the workpiece is reduced; in the process, the temperature of the vacuum carburizing furnace is kept at 975-985 ℃, the carburizing speed is increased by increasing the carburizing temperature, and the diffusion speed of carbon atoms in the workpiece is guaranteed; a person skilled in the art can know the range of the repeated times of the carburizing stage according to the actual processing requirement, and the process only needs 25.3-26.8 hours to obtain an effective hardened layer of 3.95-4.25mm, so that the production efficiency of vacuum carburizing is greatly improved.
Preferably, before the carburizing stage, the method further comprises the following steps:
a pre-cleaning stage: and soaking and cleaning the workpiece.
By adopting the technical scheme, residual oil stains on the workpiece easily pollute a hearth of the vacuum carburizing furnace and influence the heat treatment quality, so that the workpiece is cleaned before carburization, on one hand, the workpiece is protected to a certain extent by the vacuum carburizing furnace, and on the other hand, the carburization quality of the workpiece is improved.
Preferably, before the carburizing stage, the method further comprises the following steps:
a temperature equalization stage: heating the vacuum carburizing furnace with the workpiece to 845-855 ℃, and keeping for 90-110 min;
a temperature equalizing stage: heating the vacuum carburizing furnace to 975 and 985 ℃ and keeping the temperature for 90-110 min.
By adopting the technical scheme, the vacuum carburizing furnace is heated up in stages before carburizing treatment, so that the service life of the vacuum carburizing furnace is protected, the internal and external temperature difference of a workpiece is reduced, the thermal stress generated in the heating process is reduced, and the carburizing quality is improved.
Preferably, the cooling phase comprises the steps of:
and (3) slow cooling stage: and (3) placing the workpiece into a slow cooling chamber of a vacuum carburizing furnace for slow cooling, keeping for 90-110min, and taking out the workpiece from the vacuum carburizing furnace.
By adopting the technical scheme, after the carburization stage is completed, the workpiece is placed into the slow cooling chamber to be slowly cooled, so that on one hand, cracks caused by thermal stress and tissue stress in the recooling process are avoided, on the other hand, residual austenite in the workpiece can be decomposed to a certain degree, and the quality of the workpiece is improved.
Preferably, after the carburizing stage and before the cooling stage, the method further comprises the following steps:
cooling and soaking: and cooling the vacuum carburizing furnace with the workpiece to 875-885 ℃, and keeping the temperature for 90-110 min.
By adopting the technical scheme, the cooling and soaking are carried out before the cooling stage after the carburizing stage, on one hand, conditions are provided for further diffusion of carbon atoms in the workpiece, the carburizing quality and the carburizing efficiency are further improved, on the other hand, austenite crystal grains in the workpiece are favorably refined, and the structure of the workpiece is improved.
Preferably, after the cooling stage, the method further comprises the following steps:
and (3) high-temperature tempering: heating the workpiece to 645 ℃ and 655 ℃, keeping the temperature for 200min and 220min, and then cooling the workpiece to below 60 ℃.
By adopting the technical scheme, high-temperature tempering is carried out after carburization and cooling, on one hand, the residual internal stress of the workpiece after carburization and cooling is favorably eliminated, on the other hand, a large amount of residual austenite exists in the workpiece after carburization and cooling, the residual austenite is decomposed through high-temperature tempering, the Ms point of the austenite is improved, the crystal grains on the surface of the workpiece are convenient to refine, and therefore the quality of the workpiece is improved.
Preferably, in the high temperature tempering stage, the workpiece is heated in a vacuum environment.
By adopting the technical scheme, the workpiece is subjected to vacuum tempering, so that the possibility of oxidation or decarburization of the workpiece is reduced, and the toughness of the workpiece is improved.
Preferably, the high-temperature tempering stage is performed in a vacuum gas quenching furnace, and in the high-temperature tempering stage, the cooling mode is to introduce nitrogen into the vacuum gas quenching furnace so as to cool the workpiece along with the furnace.
By adopting the technical scheme, the nitrogen is introduced into the vacuum gas quenching furnace, so that the cooling speed of the workpiece is accelerated, the growth of austenite grains in the workpiece is inhibited, the grains are favorably refined, the quality of the workpiece is improved, the excessive tapping temperature of the part can be avoided by furnace cooling, and the possibility of oxidation on the surface of the workpiece is reduced.
Preferably, after the high temperature tempering stage, the method further comprises the following steps:
and (3) quenching: heating the workpiece to 815-825 deg.C, maintaining for 240min at 220-110 deg.C, and cooling in 90-110 deg.C quenching oil for 20-40 min;
and (3) low-temperature tempering: the workpiece is heated to 150 ℃ and 170 ℃ and kept for 280min and 300 min.
By adopting the technical scheme, after the carburizing-cooling-high temperature tempering process is completed, the workpiece obtains a final structure through quenching and low temperature tempering, so that the surface of the workpiece obtains a martensite structure, and the hardness of the surface of the workpiece is improved.
Preferably, after the quenching stage and before the low-temperature tempering stage, the method further comprises the following steps:
and (3) post-cleaning: and soaking and cleaning the quenched workpiece.
By adopting the technical scheme, after quenching is finished, quenching oil on the surface of the workpiece is removed by cleaning, so that subsequent low-temperature tempering treatment is facilitated, the surface quality of the workpiece is improved, the possibility of smoke generation and pollution caused by residual oil stains during tempering is reduced, and the tempering equipment is protected.
In summary, the present application includes at least one of the following beneficial technical effects:
1. the acetylene is introduced into the vacuum carburizing furnace in a staged manner and is diffused in a staged manner, and compared with the primary carburizing-diffusion process, the accumulation of carbon atoms on the surface of the workpiece is reduced through the circulation of the carburizing-diffusion step, so that the carbon atoms can permeate into the workpiece in time, the diffusion efficiency of the carbon atoms on the surface layer of the workpiece is improved, and the heat treatment deformation of the workpiece is reduced; in the process, the temperature of the vacuum carburizing furnace is kept at 975-985 ℃, the carburizing speed is increased by increasing the carburizing temperature, and the diffusion speed of carbon atoms in the workpiece is guaranteed; the technical personnel in the field can know the range of the repeated times of the carburizing stage according to the actual processing requirement, and the process only needs 25.3-26.8 hours to obtain an effective hardened layer of 3.95-4.25mm, thereby greatly improving the production efficiency of vacuum carburizing;
2. the vacuum carburizing furnace is heated in stages before carburizing treatment, so that the service life of the vacuum carburizing furnace is protected, the internal and external temperature difference of a workpiece is reduced, the thermal stress generated in the heating process is reduced, and the carburizing quality is improved;
3. the cooling and soaking are carried out after the carburizing stage and before the cooling stage, on one hand, conditions are provided for further diffusion of carbon atoms in the workpiece, the carburizing quality and the carburizing efficiency are further improved, on the other hand, austenite crystal grains in the workpiece are favorably refined, and the structure of the workpiece is improved.
Detailed Description
Sources of raw materials and equipment
Unless otherwise specified, the designations and sources of the raw materials and equipment in the following examples and comparative examples are shown in table 1 below.
TABLE 1 raw materials and Equipment designations and sources
| Feedstock/plant | Number plate | Source |
| Degreasing hydrocarbon cleaning agent | Industrial grade | Suzhou Haigang chemical Co Ltd |
| Vacuum soaking cleaning machine | HWBV | Jiangsu Fengdong Thermal Technology Co., Ltd. |
| Vacuum carburizing furnace (full name: vacuum carburizing oil quenching furnace) | VCB-76/70/120 | JIANGSU IHI FENGDONG VACUUM TECHNOLOGY Co.,Ltd. |
| Vacuum gas quenching furnace | VKNQ-600 | JIANGSU IHI FENGDONG VACUUM TECHNOLOGY Co.,Ltd. |
| Box type multipurpose stove | UBE-400 | Jiangsu Fengdong Thermal Technology Co., Ltd. |
Workpiece material: 20Cr2Ni4
Workpiece size: phi 60mm x 120mm
Examples
Example 1
A low-carbon high-alloy steel vacuum carburizing heat treatment process comprises the following steps:
s1, pre-cleaning stage: putting the workpiece into a vacuum soaking cleaning machine, cleaning by a degreasing hydrocarbon cleaning agent at 110 ℃, and taking out the workpiece after cleaning oil stains on the surface of the workpiece;
s2, temperature equalization stage: putting the workpiece into a heating chamber of a vacuum carburizing oil quenching furnace, heating to 845 ℃, and keeping for 90 min;
s3, temperature equalization stage: heating the vacuum carburizing oil quenching furnace to 985 ℃, and keeping for 100 min;
s4, carburizing: keeping the temperature of the vacuum carburizing oil quenching furnace at 985 ℃, continuously introducing acetylene into the vacuum carburizing oil quenching furnace, wherein the acetylene flow is 14L/min, stopping introducing acetylene after 18min, vacuumizing the vacuum carburizing oil quenching furnace, and keeping the temperature for 200 min; repeating the step S4 for 7 times, and entering S5;
s5, cooling and soaking: cooling the vacuum carburizing oil quenching furnace to 880 ℃, and keeping the temperature for 110 min;
s6, slow cooling stage: slowly cooling the workpiece in a slow cooling chamber of a vacuum carburizing oil quenching furnace, keeping for 100min, and taking out the workpiece from the vacuum carburizing oil quenching furnace;
s7, high-temperature tempering: putting the workpiece into a vacuum quenching furnace, vacuumizing the vacuum quenching furnace, heating to 650 ℃ through 2Bar nitrogen convection, keeping for 220min, and introducing 2Bar nitrogen into the vacuum quenching furnace to cool the workpiece to 60 ℃ along with the furnace;
s8, quenching: putting a workpiece into a heating chamber of a vacuum carburizing oil quenching furnace, heating to 820 ℃, keeping for 220min, then putting the workpiece into quenching oil at 100 ℃, cooling for 30min, and taking the workpiece out of the vacuum carburizing oil quenching furnace;
s9, post-cleaning stage: putting the workpiece into a vacuum soaking cleaning machine, cleaning by a degreasing hydrocarbon cleaning agent at 120 ℃, and taking out the workpiece after cleaning oil stains on the surface of the workpiece;
s10, low-temperature tempering: and (3) putting the workpiece into a box type multipurpose furnace, heating to 170 ℃, keeping for 290min, and taking the workpiece out of the box type multipurpose furnace.
Example 2
A low-carbon high-alloy steel vacuum carburizing heat treatment process comprises the following steps:
s1, pre-cleaning stage: putting the workpiece into a vacuum soaking cleaning machine, cleaning by a degreasing hydrocarbon cleaning agent at 120 ℃, and taking out the workpiece after cleaning oil stains on the surface of the workpiece;
s2, temperature equalization stage: putting the workpiece into a heating chamber of a vacuum carburizing oil quenching furnace, heating to 855 ℃, and keeping for 110 min;
s3, temperature equalization stage: heating a vacuum carburizing oil quenching furnace to 980 ℃, and keeping the temperature for 90 min;
s4, carburizing: keeping the temperature of the vacuum carburizing oil quenching furnace at 980 ℃, continuously introducing acetylene into the vacuum carburizing oil quenching furnace, wherein the flow rate of the acetylene is 13L/min, stopping introducing the acetylene after 17min, vacuumizing the vacuum carburizing oil quenching furnace, and keeping the vacuum carburizing oil quenching furnace for 210 min; repeating the step S4 for 7 times, and entering S5;
s5, cooling and soaking: cooling the vacuum carburizing oil quenching furnace to 885 ℃, and keeping the temperature for 100 min;
s6, slow cooling stage: slowly cooling the workpiece in a slow cooling chamber of a vacuum carburizing oil quenching furnace, keeping for 110min, and taking out the workpiece from the vacuum carburizing oil quenching furnace;
s7, high-temperature tempering: putting a workpiece into a vacuum quenching furnace, vacuumizing the vacuum quenching furnace, heating to 645 ℃ through 2Bar nitrogen convection, keeping for 210min, and introducing 2Bar nitrogen into the vacuum quenching furnace to cool the workpiece to 60 ℃ along with the furnace;
s8, quenching: putting a workpiece into a heating chamber of a vacuum carburizing oil quenching furnace, heating to 825 ℃, keeping for 230min, then putting the workpiece into quenching oil at 110 ℃, cooling for 20min, and taking the workpiece out of the vacuum carburizing oil quenching furnace;
s9, post-cleaning stage: putting the workpiece into a vacuum soaking cleaning machine, cleaning by a degreasing hydrocarbon cleaning agent at 110 ℃, and taking out the workpiece after cleaning oil stains on the surface of the workpiece;
s10, low-temperature tempering: and (3) putting the workpiece into a box type multipurpose furnace, heating to 150 ℃, keeping for 280min, and taking the workpiece out of the box type multipurpose furnace.
Example 3
A low-carbon high-alloy steel vacuum carburizing heat treatment process comprises the following steps:
s1, pre-cleaning stage: putting the workpiece into a vacuum soaking cleaning machine, cleaning by a degreasing hydrocarbon cleaning agent at the cleaning temperature of 130 ℃, and taking out the workpiece after cleaning oil stains on the surface of the workpiece;
s2, temperature equalization stage: putting the workpiece into a heating chamber of a vacuum carburizing oil quenching furnace, heating to 850 ℃, and keeping for 100 min;
s3, temperature equalization stage: heating a vacuum carburizing oil quenching furnace to 975 ℃, and keeping the temperature for 110 min;
s4, carburizing: keeping the temperature of the vacuum carburizing oil quenching furnace at 975 ℃, continuously introducing acetylene into the vacuum carburizing oil quenching furnace, wherein the acetylene flow is 15L/min, stopping introducing acetylene after 20min, vacuumizing the vacuum carburizing oil quenching furnace, and keeping for 205 min; repeating the step S4 for 7 times, and entering S5;
s5, cooling and soaking: cooling the vacuum carburizing oil quenching furnace to 875 ℃ and keeping the temperature for 90 min;
s6, slow cooling stage: slowly cooling the workpiece in a slow cooling chamber of a vacuum carburizing oil quenching furnace, keeping for 90min, and taking out the workpiece from the vacuum carburizing oil quenching furnace;
s7, high-temperature tempering: putting the workpiece into a vacuum quenching furnace, vacuumizing the vacuum quenching furnace, heating to 655 ℃ by 2Bar nitrogen convection, keeping for 200min, and introducing 2Bar nitrogen into the vacuum quenching furnace to cool the workpiece to 60 ℃ along with the furnace;
s8, quenching: putting a workpiece into a heating chamber of a vacuum carburizing oil quenching furnace, heating to 815 ℃, keeping for 240min, then putting the workpiece into quenching oil at 90 ℃, cooling for 40min, and taking the workpiece out of the vacuum carburizing oil quenching furnace;
s9, post-cleaning stage: putting the workpiece into a vacuum soaking cleaning machine, cleaning by a degreasing hydrocarbon cleaning agent at 110 ℃, and taking out the workpiece after cleaning oil stains on the surface of the workpiece;
s10, low-temperature tempering: and (3) putting the workpiece into a box type multipurpose furnace, heating to 150 ℃, keeping for 280min, and taking the workpiece out of the box type multipurpose furnace.
Example 4
Example 4 differs from example 3 in that there is no cool down soaking stage in example 4.
Comparative example
Comparative example 1
The difference between comparative example 1 and example 3 is that the carburization stage is different from the carburization stage in which the method is: and (3) keeping the temperature of the vacuum carburizing oil quenching furnace at 975 ℃, continuously introducing acetylene into the vacuum carburizing oil quenching furnace, wherein the acetylene flow is 15L/min, stopping introducing acetylene after 140min, vacuumizing the vacuum carburizing oil quenching furnace, keeping 1435min, and then entering S5.
Performance test
Detection method/test method
The workpieces of the examples and comparative examples were tested for their properties, and the following tests were performed, respectively:
1. and (3) surface hardness detection: the measurement is carried out by using HR-150DTL Rockwell hardness tester of Shanghai Bill test equipment Co., Ltd according to GB/T230.1-2018.
2. And (3) detecting the core hardness: the measurement is carried out by using HR-150DTL Rockwell hardness tester of Shanghai Bill test equipment Co., Ltd according to GB/T230.1-2018.
3. And (3) detecting the depth of the effective hardened layer: the test is carried out according to GB/T9450-2005 by adopting MH-6 micro Vickers hardness tester of Shanghai Hengyi precision instruments Co.
4. And (3) metallographic structure detection: the detection was carried out according to JB/T6141.3-1992 using an Axio Observer 3m metallographic microscope from Zeiss, Germany.
5. And (3) detecting the surface carbon concentration: the detection is carried out by a CCD-6000 spectrometer of Steel Yan Nak detection technology GmbH.
The results of the tests of examples 1 to 4 and comparative example 1 are shown in Table 2.
TABLE 2 Performance test results
It can be seen from the combination of examples 1 to 4 and table 2 that, by the cycle of the carburization-diffusion step, an effective hardened layer of 3.95 to 4.25mm can be obtained only for 25.3 to 26.8 hours, and the production efficiency of vacuum carburization is significantly improved. Since the step of temperature reduction and soaking is not adopted in example 4, slow cooling is directly carried out after the end of the carburizing-diffusing cycle, and carbon atoms are not further diffused, so that the effective depth of a hard layer and the surface carbon concentration of example 4 are slightly lower than those of examples 1-3, and simultaneously, martensite and retained austenite grains on the surface of the workpiece of example 4 are coarser than those of examples 1-3, which indicates that the step of temperature reduction and soaking is omitted, so that the retained austenite on the surface of the workpiece is not effectively decomposed, and the grains are not further refined.
It can be seen from the combination of example 3 and comparative example 1 and the combination of table 2 that the effective hardened layer depth of the workpiece in comparative example 1 is far lower than that of example 3, and the surface carbon concentration is also reduced, which shows that compared with the case of one-time carburization-diffusion, the process has the advantages that the production efficiency of vacuum carburization is greatly improved through 7 cycles of carburization-diffusion, the accumulation of carbon atoms on the surface of the workpiece is reduced, the carbon atoms can timely permeate into the workpiece, and the diffusion efficiency of the carbon atoms on the surface layer of the workpiece is improved.
The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.
Claims (10)
1. A low-carbon high-alloy steel vacuum carburizing heat treatment process is characterized by comprising the following steps:
and (3) carburizing: heating the vacuum carburizing furnace with the workpiece to 975-;
and repeating the carburizing stage for at least 2 times, and then entering a cooling stage.
2. The low carbon high alloy steel vacuum carburization heat treatment process of claim 1, further comprising, prior to said carburization stage, the steps of:
a pre-cleaning stage: and soaking and cleaning the workpiece.
3. The low carbon high alloy steel vacuum carburization heat treatment process of claim 1, further comprising, prior to said carburization stage, the steps of:
a temperature equalization stage: heating the vacuum carburizing furnace with the workpiece to 845-855 ℃ and keeping for 90-110 min;
a temperature equalizing stage: heating the vacuum carburizing furnace to 975 ℃ and 985 ℃ and keeping the temperature for 90-110 min.
4. The low carbon high alloy steel vacuum carburization heat treatment process of claim 1, where said cooling phase comprises the steps of:
and (3) slow cooling stage: and (3) placing the workpiece into a slow cooling chamber of a vacuum carburizing furnace for slow cooling, keeping for 90-110min, and taking out the workpiece from the vacuum carburizing furnace.
5. The low carbon high alloy steel vacuum carburization heat treatment process of claim 1, further comprising, after said carburization phase and before said cooling phase, the steps of:
cooling and soaking: and cooling the vacuum carburizing furnace with the workpiece to 875 ℃ and 885 ℃, and keeping the temperature for 90-110 min.
6. The low carbon high alloy steel vacuum carburization heat treatment process of claim 1, further comprising, after said cooling phase, the steps of:
and (3) high-temperature tempering: heating the workpiece to 645 ℃ and 655 ℃, keeping the temperature for 200 ℃ and 220min, and then cooling the workpiece to below 60 ℃.
7. The vacuum carburizing heat treatment process for low-carbon high-alloy steel according to claim 6, characterized in that: in the high-temperature tempering stage, the workpiece is heated in a vacuum environment.
8. The vacuum carburizing heat treatment process for low-carbon high-alloy steel according to claim 7, characterized in that: and in the high-temperature tempering stage, the cooling mode is that nitrogen is introduced into the vacuum gas quenching furnace, so that the workpiece is cooled along with the furnace.
9. The low carbon high alloy steel vacuum carburization heat treatment process of claim 6, further comprising, after said high temperature tempering stage, the steps of:
and (3) quenching: heating the workpiece to 815-825 ℃ and keeping for 220-240min, and then cooling the workpiece in quenching oil at 90-110 ℃ for 20-40 min;
and (3) low-temperature tempering: the workpiece is heated to 150 ℃ and 170 ℃ and kept for 280min and 300 min.
10. The low carbon high alloy steel vacuum carburization heat treatment process of claim 9, further comprising, after said quenching stage and before said low temperature tempering stage, the steps of:
and (3) post-cleaning: and soaking and cleaning the quenched workpiece.
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