CN116623122A - Alloy steel and heat treatment method thereof - Google Patents
Alloy steel and heat treatment method thereof Download PDFInfo
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- CN116623122A CN116623122A CN202310596704.9A CN202310596704A CN116623122A CN 116623122 A CN116623122 A CN 116623122A CN 202310596704 A CN202310596704 A CN 202310596704A CN 116623122 A CN116623122 A CN 116623122A
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- 229910000851 Alloy steel Inorganic materials 0.000 title claims abstract description 86
- 238000010438 heat treatment Methods 0.000 title claims abstract description 65
- 238000000034 method Methods 0.000 title claims abstract description 49
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 105
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 96
- 238000005121 nitriding Methods 0.000 claims abstract description 68
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 51
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 48
- 230000003647 oxidation Effects 0.000 claims abstract description 17
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 17
- 239000007789 gas Substances 0.000 claims abstract description 13
- 238000001816 cooling Methods 0.000 claims abstract description 9
- 238000011282 treatment Methods 0.000 claims abstract description 9
- 239000011261 inert gas Substances 0.000 claims abstract description 5
- 239000012298 atmosphere Substances 0.000 claims abstract description 4
- 229910000831 Steel Inorganic materials 0.000 claims description 48
- 239000010959 steel Substances 0.000 claims description 48
- 238000000354 decomposition reaction Methods 0.000 claims description 5
- 230000001590 oxidative effect Effects 0.000 claims description 2
- 229910045601 alloy Inorganic materials 0.000 abstract description 3
- 239000000956 alloy Substances 0.000 abstract description 3
- 239000000126 substance Substances 0.000 abstract 1
- 125000004433 nitrogen atom Chemical group N* 0.000 description 29
- 230000008569 process Effects 0.000 description 14
- 239000012459 cleaning agent Substances 0.000 description 12
- 238000009792 diffusion process Methods 0.000 description 10
- 239000000463 material Substances 0.000 description 10
- 238000004140 cleaning Methods 0.000 description 9
- 238000012360 testing method Methods 0.000 description 9
- 230000000694 effects Effects 0.000 description 8
- 239000010410 layer Substances 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 4
- 230000035515 penetration Effects 0.000 description 4
- 229910000838 Al alloy Inorganic materials 0.000 description 3
- 230000001680 brushing effect Effects 0.000 description 3
- 238000005336 cracking Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 230000008595 infiltration Effects 0.000 description 3
- 238000001764 infiltration Methods 0.000 description 3
- 150000004767 nitrides Chemical class 0.000 description 3
- 239000012299 nitrogen atmosphere Substances 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 239000011241 protective layer Substances 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 238000005496 tempering Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 229910000797 Ultra-high-strength steel Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000005381 potential energy Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
Classifications
-
- 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
-
- 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
- C23C8/02—Pretreatment of the material to be coated
-
- 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
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
Abstract
The application relates to alloy steel and a heat treatment method thereof. The heat treatment method of the alloy steel comprises the following steps: pre-oxidation stage: preoxidation of alloy steelCarrying out chemical treatment; nitriding in the first stage: under the condition of mixed gas of ammonia and cracked ammonia, the alloy steel is subjected to primary heat treatment, and the nitrogen potential value K of the primary heat treatment N 4-6, and ammonia flow rate of 3-5 m 3 /h; nitriding in the second stage: under the condition of mixed gas of ammonia and cracked ammonia, the alloy steel is subjected to secondary heat treatment, and the nitrogen potential value K of the secondary heat treatment N 1-3, and ammonia flow rate of 2-3 m 3 /h; and (3) a cooling stage: and in the inert gas atmosphere, the temperature of the alloy steel is reduced to below 100 ℃ to obtain the nitriding alloy steel. The application also provides alloy steel which is prepared by the heat treatment method. The application effectively improves the surface hardness of the alloy steel.
Description
Technical Field
The application relates to the technical field of surface heat treatment, in particular to alloy steel and a heat treatment method thereof.
Background
Nitriding treatment is carried out on the surface of steel, nitrogen atoms are permeated into conventional materials, so that the hardness, mechanical property, wear resistance, corrosion resistance and other characteristics of the surface of the materials are improved, and the method is a heat treatment process method commonly used for steel materials and is widely applied to the industrial field.
The 42CrMo material is often subjected to surface strengthening by adopting a nitriding heat treatment method, and the conventional common nitriding process is generally carried out at 500-520 ℃ and with the nitrogen potential K N After the nitriding process is adopted for treatment, the surface hardness of the material can only reach about 650HV, and the material is difficult to further improve, so that the application of the 42CrMo material is limited.
Disclosure of Invention
The application aims to provide alloy steel and a heat treatment method thereof, so as to improve the surface hardness of the alloy steel and widen the application of the alloy steel.
In order to achieve the above purpose, the technical scheme adopted by the application is as follows:
a method of heat treating alloy steel, comprising the steps of:
pre-oxidation stage: pre-oxidizing alloy steel;
nitriding in the first stage: under the condition of mixed gas of ammonia and cracked ammonia, the alloy steel is subjected to primary heat treatment, and the nitrogen potential value K of the primary heat treatment N 4 to 6, the ammonia flow is 3 to 5m 3 /h；
Nitriding in the second stage: under the condition of mixed gas of ammonia and cracked ammonia, the alloy steel is subjected to secondary heat treatment, and the nitrogen potential value K of the secondary heat treatment N 1 to 3, the ammonia flow is 2 to 3m 3 /h；
And (3) a cooling stage: and in the inert gas atmosphere, the temperature of the alloy steel is reduced to below 100 ℃ to obtain the nitriding alloy steel.
According to the technical means, the effect of uniform temperature is achieved by setting the pre-oxidation stage, preparation is carried out for the subsequent rise to higher nitriding temperature, pre-oxidation is carried out on alloy steel, good precondition is provided for the penetration of nitrogen atoms into the alloy steel in the nitriding stage, high-concentration nitriding is carried out in the nitriding stage by adopting large-flow ammonia gas and higher nitrogen potential value, so that a large amount of nitrogen atoms are penetrated into the surface of the alloy steel in a short time, the nitrogen content of the surface of the alloy steel is effectively improved, diffusion is carried out by adopting slightly lower-concentration nitrogen potential, meanwhile, proper amount of cracking ammonia is doped, the fact that the penetrated nitrogen atoms want to diffuse into the interior is ensured, further the hardness of the surface of the alloy steel is effectively improved, the problem that the concentration of the nitrogen atoms on the surface of the alloy steel is affected is effectively avoided by oxidation through protection of the protection gas after the nitriding is finished, and the method has the advantages of simple operation, easy time in process and suitability for industrial application.
The 42CrMo steel belongs to alloy structural steel in material classification, has good mechanical property and workability, is quite widely applied, mainly comprises two types of materials of plates and round bars, has comprehensive properties superior to 40cr, and is accepted by industry. The 42CrMo steel belongs to ultra-high strength steel, has high strength and toughness, better hardenability, no obvious tempering brittleness, higher fatigue limit and multiple impact resistance after quenching and tempering treatment, and good low-temperature impact toughness. The 42CrMo steel is suitable for manufacturing large and medium plastic molds which require certain strength and toughness. The 42CrMo steel comprises the following components in percentage by mass: carbon: 0.38 to 0.45 percent of silicon: 0.17 to 0.37 percent of manganese: 0.50 to 0.80 percent of sulfur: allowing residual content less than or equal to 0.035%, phosphorus: allowing residual content less than or equal to 0.035%, chromium: 0.90 to 1.20 percent of nickel: allowing residual content less than or equal to 0.30 percent, copper: allowing residual content less than or equal to 0.30 percent, molybdenum: 0.15 to 0.25 percent and the balance of iron.
The inventor of the present application has found through long-term research and analysis that the surface hardness of the 42CrMo steel workpiece after nitriding disclosed in the prior art is not high, and mainly high-concentration nitrogen atoms are difficult to penetrate into the surface and the subsurface of the 42CrMo steel workpiece. The nitrogen absorption capacity of iron increases with increasing temperature, but after the temperature increases to a certain temperature, the change becomes no longer noticeable. When active nitrogen atoms formed by ammonia decomposition are gathered on the surface of the 42CrMo steel workpiece, the active nitrogen atoms must be permeated into the surface of the 42CrMo steel workpiece in time, otherwise, the active nitrogen atoms are immediately polymerized into nitrogen molecules so as to lose activity, and the nitrogen molecules cannot be used for nitriding. When the application adopts the nitriding at 550-560 ℃, the ammonia decomposition rate is kept at about 40-60%, and the 42CrMo steel workpiece still has higher nitrogen absorbing capacity. Therefore, the selection of appropriate process parameters ensures high concentrations of nitrogen and rapid and efficient infiltration into the 42CrMo steel workpiece surface is a key technique to achieve high hardness.
After the high-concentration nitrogen atoms are permeated into the surface of the 42CrMo steel workpiece, if the permeated nitrogen atoms cannot timely diffuse into the 42CrMo steel workpiece when the concentration of the permeated nitrogen atoms is high, alloy elements contained in the 42CrMo steel workpiece can be quickly focused into nitride and are separated out at a crystal boundary, so that the strengthening effect of the surface of the 42CrMo steel workpiece is reduced. Nitriding at 550-560 ℃ to form three phase areas from the surface to the inside of the 42CrMo steel workpiece, namely epsilon, gamma' and alpha, and the diffusion speed V alpha of nitrogen atoms in the three phase areas>Vε>Vγ ' has the lowest diffusion rate in the γ ' phase, and therefore, it is the most desirable problem to solve the diffusion rate of nitrogen atoms in the γ ' phase. The inventor selects proper nitrogen potential K in the nitriding process of the second stage N To determine a reasonable ammonia decomposition rate, and additionally introducing a suitable ammonia gas andthe flow of the cracked ammonia promotes the optimal diffusion rate of nitrogen atoms in the gamma' phase.
Based on the analysis, the inventor performs related tests, and performs corresponding comparative tests through different nitriding temperatures, nitriding times, flow ratios and ratios of nitrogen potential values, so as to obtain a set of optimal technological scheme parameters, solve the problem of difficult diffusion of high-concentration nitrogen, and obtain the high nitriding hardness of the 42CrMo material.
Preferably, the pre-oxidation treatment is to heat-treat the alloy steel at the temperature of 400-450 ℃ for 0.5-1 h.
Experiments prove that the preoxidation time is between 0.5 and 1h by setting the preoxidation temperature between 400 and 450 ℃, so that the effect of uniform temperature is effectively ensured, and the infiltration of nitrogen atoms into the alloy steel in the nitriding stage is facilitated.
Preferably, the first stage nitriding is carried out, and the flow rate of the ammonia to be cracked is 2-3 m 3 /h。
Experiments prove that in the first nitriding stage, the flow of the ammonia to be cracked is controlled to be 2-3 m 3 And/h, the nitrogen atoms are ensured to quickly and effectively permeate into the alloy steel.
Preferably, the second stage nitriding is carried out with the ammonia decomposition flow rate of 1-2 m 3 /h。
Experiments prove that in the second nitriding stage, the diffusion of permeated nitrogen atoms into the inside is effectively promoted by controlling the flow of the ammonia cracking to be smaller than that in the first nitriding stage.
Preferably, the temperature of the primary heat treatment and the secondary heat treatment is 550 ℃ to 560 ℃.
Experiments prove that in the two nitriding stages, the temperature is controlled between 550 ℃ and 560 ℃ so that active nitrogen atoms have higher potential energy, so that a very high nitrogen potential is formed on the surface of the aluminum alloy steel, high-concentration nitrogen infiltration is realized, and in the second nitriding stage, the nitrogen concentration gradient of the aluminum alloy steel is mainly adjusted through nitrogen diffusion, so that the surface of the aluminum alloy steel can obtain ultrahigh hardness.
Preferably, the primary heat treatment time is 2-4 hours, and the secondary heat treatment time is 15-25 hours.
Because the nitrogen potential value is high and a large amount of nitrogen atoms are accumulated in the primary heat treatment process, the primary heat treatment time is controlled within 2-4 hours so as to avoid the occurrence of more serious network nitrides. Because the nitrogen potential value is relatively low in the secondary heat treatment process, the secondary heat treatment time is prolonged, and the diffusion of nitrogen is effectively ensured.
Preferably, the alloy steel is 42CrMo steel.
Preferably, the inert gas is nitrogen, and the flow rate of the introduced nitrogen is 4-6 m in the cooling stage 3 /h。
Through controlling the nitrogen concentration in the cooling stage, the surface of the alloy steel is effectively prevented from being oxidized, and the hardness of the surface of the alloy steel is further ensured.
The application also provides alloy steel which is prepared by adopting the heat treatment method.
Preferably, the depth of the nitriding layer on the surface of the alloy steel is 0.28-0.32 mm, and the hardness of the surface of the alloy steel is more than 800 HV.
The application has the beneficial effects that:
according to the heat treatment method of the alloy steel, through setting the pre-oxidation stage, the effect of uniform temperature is achieved, preparation is carried out for the subsequent rising to a higher nitriding temperature, pre-oxidation is carried out on the alloy steel, good preconditions are provided for the penetration of nitrogen atoms into the alloy steel in the nitriding stage, high-flow ammonia gas and higher nitrogen potential values are adopted, so that high-concentration nitriding is carried out in the nitriding starting stage, a large amount of nitrogen atoms are penetrated into the surface of the alloy steel in a short time, the nitrogen content of the surface of the alloy steel is effectively improved, diffusion is carried out with a slightly lower-concentration nitrogen potential, meanwhile, proper amount of cracking ammonia is doped, the penetration of the nitrogen atoms into the alloy steel is guaranteed, the hardness of the surface of the alloy steel is effectively improved, the nitrogen atoms are cooled to below 100 ℃ through protection of protective gas after the nitriding is finished, the problem that the nitrogen atoms on the surface of the alloy steel are oxidized is effectively avoided, and the heat treatment method has the advantages of simplicity in operation, easiness in time in process and suitability for industrial application;
the test shows that the depth of the nitriding layer on the surface of the alloy steel is 0.28-0.32 mm, the hardness of the surface of the alloy steel is above 800HV, and the surface hardness of the alloy steel is effectively improved, so that the application of the alloy steel is widened, and the method has popularization and application values in the technical field of heat treatment of the surface of the alloy steel.
Drawings
FIG. 1 is a process scheme of a heat treatment method of alloy steel of the present application;
fig. 2 is a hardness detection position diagram.
Detailed Description
Further advantages and effects of the present application will become readily apparent to those skilled in the art from the disclosure herein, by referring to the accompanying drawings and the preferred embodiments. The application may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present application. It should be understood that the preferred embodiments are presented by way of illustration only and not by way of limitation.
It should be noted that the illustrations provided in the following embodiments merely illustrate the basic concept of the present application by way of illustration, and only the components related to the present application are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complicated.
Example 1
A method of heat treating alloy steel, comprising the steps of:
s1, pretreatment: firstly, thoroughly cleaning greasy dirt and impurities on the surface of a 42CrMo steel workpiece by adopting a water-based cleaning agent or a gasoline cleaning agent with strong detergency; when the cleaning agent is used for cleaning, the cleaning agent needs to be dried after the cleaning is finished, so that the residual water on the surface of the 42CrMo steel workpiece and in the pore canal is thoroughly eliminated; secondly, brushing a protective layer on a part which does not require high hardness and high nitrogen concentration on the surface of the 42CrMo steel workpiece for protection;
s2, a pre-oxidation stage: carrying out heat treatment on the 42CrMo steel workpiece subjected to pretreatment at the temperature of 450 ℃ for 45min;
s3, nitriding in the first stage: performing primary heat treatment on the 42CrMo steel workpiece subjected to pre-oxidation under the condition of mixed gas of ammonia and cracked ammonia, wherein the nitrogen potential value K of the primary heat treatment N 5.5 and ammonia flow of 4.5m 3 And/h, the flow rate of the cracked ammonia is 2.5m 3 And/h, wherein the temperature is 555 ℃ and the time is 2.5h;
s4, nitriding in the second stage: performing secondary heat treatment on the 42CrMo steel workpiece subjected to the first-stage nitriding under the condition of mixed gas of ammonia and cracked ammonia, wherein the nitrogen potential value K of the secondary heat treatment N 2.5 and ammonia flow of 2.5m 3 And/h, the flow rate of the cracked ammonia is 1.5m 3 And/h, wherein the temperature is 555 ℃ and the time is 18h;
s5, a cooling stage: in nitrogen atmosphere, the temperature of the 42CrMo steel workpiece subjected to the second-stage nitriding is reduced to be lower than 100 ℃ to obtain the nitrided 42CrMo steel workpiece, wherein the flow rate of nitrogen is 5m 3 /h。
Example 2
A method of heat treating alloy steel, comprising the steps of:
s1, pretreatment: firstly, thoroughly cleaning greasy dirt and impurities on the surface of a 42CrMo steel workpiece by adopting a water-based cleaning agent or a gasoline cleaning agent with strong detergency; when the cleaning agent is used for cleaning, the cleaning agent needs to be dried after the cleaning is finished, so that the residual water on the surface of the 42CrMo steel workpiece and in the pore canal is thoroughly eliminated; secondly, brushing a protective layer on a part which does not require high hardness and high nitrogen concentration on the surface of the 42CrMo steel workpiece for protection;
s2, a pre-oxidation stage: carrying out heat treatment on the 42CrMo steel workpiece subjected to pretreatment at the temperature of 450 ℃ for 45min;
s3, nitriding in the first stage: performing primary heat treatment on the 42CrMo steel workpiece subjected to pre-oxidation under the condition of mixed gas of ammonia and cracked ammonia, wherein one of the heat treatments is thatNitrogen potential value K of secondary heat treatment N 5.0 and ammonia flow rate of 4.0m 3 And/h, the flow rate of the cracked ammonia is 2.5m 3 And/h, wherein the temperature is 550 ℃ and the time is 3h;
s4, nitriding in the second stage: performing secondary heat treatment on the 42CrMo steel workpiece subjected to the first-stage nitriding under the condition of mixed gas of ammonia and cracked ammonia, wherein the nitrogen potential value K of the secondary heat treatment N 2.5 and ammonia flow of 2.5m 3 And/h, the flow rate of the cracked ammonia is 1.5m 3 And/h, wherein the temperature is 550 ℃ and the time is 20h;
s5, a cooling stage: in nitrogen atmosphere, the temperature of the 42CrMo steel workpiece subjected to the second-stage nitriding is reduced to be lower than 100 ℃ to obtain the nitrided 42CrMo steel workpiece, wherein the flow rate of nitrogen is 5m 3 /h。
Comparative example 1
A method of heat treating alloy steel, comprising the steps of:
s1, pretreatment: firstly, thoroughly cleaning greasy dirt and impurities on the surface of a 42CrMo steel workpiece by adopting a water-based cleaning agent or a gasoline cleaning agent with strong detergency; when the cleaning agent is used for cleaning, the cleaning agent needs to be dried after the cleaning is finished, so that the residual water on the surface of the 42CrMo steel workpiece and in the pore canal is thoroughly eliminated; secondly, brushing a protective layer on a part which does not require high hardness and high nitrogen concentration on the surface of the 42CrMo steel workpiece for protection;
s2, a pre-oxidation stage: carrying out heat treatment on the 42CrMo steel workpiece subjected to pretreatment at the temperature of 450 ℃ for 45min;
s3, nitriding: performing primary heat treatment on the 42CrMo steel workpiece subjected to pre-oxidation under the condition of mixed gas of ammonia and cracked ammonia, wherein the nitrogen potential value K of the primary heat treatment N 2.5 and ammonia flow of 2.0m 3 And/h, the flow rate of the cracked ammonia is 1.0m 3 And/h, wherein the temperature is 555 ℃ and the time is 23h;
s4, a cooling stage: in nitrogen atmosphere, the temperature of the 42CrMo steel workpiece subjected to the second-stage nitriding is reduced to be lower than 100 ℃ to obtain the nitrided 42CrMo steel workpiece, wherein the flow rate of nitrogen is 5m 3 /h。
Detection analysis
Surface hardness test
After nitriding treatment was performed according to the processes and parameters of example 1, example 2 and comparative example 1, the surface hardness test was performed on the nitrided 42CrMo steel workpieces prepared in example 1, example 2 and comparative example 1 using an LM247AT microhardness tester, the experimental load was 100g, the hardness test position was shown in fig. 2, and the test results were shown in table 1.
Table 1 hardness test results
As can be seen from the analysis in Table 1, the surface hardness of the nitrided 42CrMo steel workpiece treated by the method of the present application is above 800HV, and the steel workpiece exhibits ultra-high strength.
In summary, the heat treatment method of the alloy steel of the application firstly carries out pre-oxidation treatment on the alloy steel to enable the surface of the alloy steel to be slightly oxidized, then adopts large-flow ammonia flux through nitriding in the first stage, and simultaneously adopts 4-6 high nitrogen potential K N The value is that the alloy steel surface focuses on high concentration active nitrogen atoms, so that the alloy steel surface obtains a high concentration nitriding layer in a short time, and then the nitrogen atoms on the alloy steel surface diffuse to the inside through second-stage nitriding, so as to obtain the required layer depth, meanwhile, the nitride distribution of the nitriding layer is regulated, and after the nitriding is finished, the alloy steel is cooled to below 100 ℃ by adopting protective atmosphere, so that the nitriding layer is effectively prevented from being oxidized. The heat treatment process of the alloy steel adopts a nitriding treatment method with high nitrogen potential value, breaks through the nitrogen potential value K in the nitriding process of the traditional process N The method has the advantages that the inherent concept that the nitrogen potential value range must be limited at the corresponding temperature is selected, the nitriding temperature is adopted to replace the traditional 500-520 ℃ nitriding temperature parameter, the activity of nitrogen atoms in nitriding is improved, the penetration of high-concentration nitrogen atoms on the surface of alloy steel into the alloy steel before being combined into nitrogen molecules is ensured, the nitriding effect is accelerated, and the method has popularization and application values in the technical field of alloy steel surface heat treatment.
Tests prove that the depth of the nitriding layer on the surface of the alloy steel is 0.28-0.32 mm, the hardness of the surface of the alloy steel is above 800HV, and the surface hardness of the alloy steel is effectively improved, so that the application of the alloy steel in the fields requiring high hardness and high wear resistance, such as plastic part dies, heavy-duty gears, high-pressure plunger friction pairs, high-load transmission shaft parts and the like, is widened.
The above embodiments are merely preferred embodiments for fully explaining the present application, and the scope of the present application is not limited thereto. Equivalent substitutions and modifications will occur to those skilled in the art based on the present application, and are intended to be within the scope of the present application.
Claims (10)
1. A method for heat treatment of alloy steel, comprising the steps of:
pre-oxidation stage: pre-oxidizing alloy steel;
nitriding in the first stage: under the condition of mixed gas of ammonia and cracked ammonia, the alloy steel is subjected to primary heat treatment, and the nitrogen potential value K of the primary heat treatment N 4-6, and ammonia flow rate of 3-5 m 3 /h；
Nitriding in the second stage: under the condition of mixed gas of ammonia and cracked ammonia, the alloy steel is subjected to secondary heat treatment, and the nitrogen potential value K of the secondary heat treatment N 1-3, and ammonia flow rate of 2-3 m 3 /h；
And (3) a cooling stage: and in the inert gas atmosphere, the temperature of the alloy steel is reduced to below 100 ℃ to obtain the nitriding alloy steel.
2. The heat treatment method of alloy steel according to claim 1, wherein the pre-oxidation treatment is to heat treat the alloy steel at a temperature of 400-450 ℃ for 0.5-1 h.
3. The heat treatment method of alloy steel according to claim 1, wherein the first-stage nitriding is performed at a flow rate of 2-3 m of cracked ammonia 3 /h。
4. The heat treatment method of alloy steel according to claim 1, wherein the second-stage nitriding and ammonia decomposition flow rate is 1 to 2m 3 /h。
5. The heat treatment method of alloy steel according to claim 1, wherein the primary heat treatment and the secondary heat treatment are carried out at a temperature of 550 ℃ to 560 ℃.
6. The heat treatment method of alloy steel according to claim 1, wherein the primary heat treatment is performed for 2 to 4 hours and the secondary heat treatment is performed for 15 to 25 hours.
7. The method of heat treatment of alloy steel according to claim 1, wherein the alloy steel is 42CrMo steel.
8. The heat treatment method of alloy steel according to claim 1, wherein the inert gas is nitrogen and the flow rate of the introduced nitrogen is 4-6 m in the cooling stage 3 /h。
9. Alloy steel, characterized in that it is produced by the heat treatment method according to any one of claims 1 to 8.
10. The alloy steel according to claim 9, wherein the depth of the nitriding layer on the surface of the alloy steel is 0.28-0.32 mm, and the hardness of the surface of the alloy steel is 800HV or more.
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