CN114507769A - Warm forging waste heat isothermal normalizing method for 18CrNiMo7-6 steel - Google Patents
Warm forging waste heat isothermal normalizing method for 18CrNiMo7-6 steel Download PDFInfo
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- CN114507769A CN114507769A CN202210044151.1A CN202210044151A CN114507769A CN 114507769 A CN114507769 A CN 114507769A CN 202210044151 A CN202210044151 A CN 202210044151A CN 114507769 A CN114507769 A CN 114507769A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 61
- 239000010959 steel Substances 0.000 title claims abstract description 61
- 238000000034 method Methods 0.000 title claims abstract description 50
- 238000005242 forging Methods 0.000 title claims abstract description 42
- 239000002918 waste heat Substances 0.000 title claims abstract description 13
- 238000001816 cooling Methods 0.000 claims abstract description 37
- 239000000463 material Substances 0.000 claims description 17
- 229910001562 pearlite Inorganic materials 0.000 claims description 11
- 229910000859 α-Fe Inorganic materials 0.000 claims description 10
- 238000011534 incubation Methods 0.000 claims description 4
- 238000004321 preservation Methods 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 abstract description 16
- 238000005520 cutting process Methods 0.000 abstract description 14
- 238000005255 carburizing Methods 0.000 abstract description 9
- 238000004519 manufacturing process Methods 0.000 abstract description 5
- 230000009286 beneficial effect Effects 0.000 abstract description 4
- 238000005265 energy consumption Methods 0.000 abstract description 4
- 238000003754 machining Methods 0.000 abstract description 2
- 239000002826 coolant Substances 0.000 description 7
- 238000012545 processing Methods 0.000 description 7
- 229910001563 bainite Inorganic materials 0.000 description 3
- 238000005498 polishing Methods 0.000 description 3
- 238000010791 quenching Methods 0.000 description 3
- 230000000171 quenching effect Effects 0.000 description 3
- 238000004088 simulation Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 229910000851 Alloy steel Inorganic materials 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 241000283690 Bos taurus Species 0.000 description 1
- 229910001374 Invar Inorganic materials 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 230000006032 tissue transformation Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
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-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/28—Normalising
-
- 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
-
- 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
- C21D2211/005—Ferrite
-
- 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
- C21D2211/009—Pearlite
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Articles (AREA)
- Forging (AREA)
Abstract
The application relates to a warm forging waste heat isothermal normalizing method of 18CrNiMo7-6 steel, which comprises the following steps: after finish forging of an 18CrNiMo7-6 steel member, controlled cooling the 18CrNiMo7-6 steel member to 650 ℃ at a cooling rate of 0.1 ℃/sec to 20 ℃/sec; keeping the 18CrNiMo7-6 steel component at 650 ℃ for at least 1 hour in an isothermal way; the 18CrNiMo7-6 steel is cooled to room temperature from 650 ℃. The method fully utilizes the warm forging waste heat, saves energy consumption and time; isothermal normalizing is adopted, so that heat treatment deformation is reduced; can obtain ideal tissue and is beneficial to the subsequent machining and manufacturing processes such as cutting, carburizing treatment and the like.
Description
Technical Field
The invention relates to a material normalizing method, in particular to a warm forging waste heat isothermal normalizing method for 18CrNiMo7-6 steel.
Background
The 18CrNiMo7-6 steel is a surface hardening steel and is the leading application material of key parts of gears or gear shafts. The material has the advantages of high strength, high toughness, high hardenability and the like, and is widely applied to manufacturing gear boxes, large-modulus gears, heavy-duty gears and the like. However, a bainite structure is easily obtained in the cooling process of the material, the hardness of the material is increased due to the presence of bainite, and subsequent cutting processing, carburizing and quenching treatment are not facilitated, so that the potential performance of the material is limited. Therefore, the structure of the material before cutting and carburizing needs to be controlled through an additional heat treatment process to be combined with pearlite and ferrite, so that the material has ideal hardness and simultaneously lays a good structure foundation for subsequent cutting, carburizing, quenching and the like.
Normalizing is a heat treatment that improves the toughness of steel. The main feature of normalizing is that its cooling rate is faster than annealing and lower than quenching. The normalizing mechanism is that the crystal grains of the steel material are refined in a slightly quick cooling process, so that the treated steel material has satisfactory strength, the toughness of the steel material can be obviously improved, and the cracking tendency of steel material components is reduced.
The inventor of invar and others disclosed an invention application entitled "normalizing heat treatment by using residual heat after forging of forgings" (CN 102605147 a). The method comprises the steps of controlling the forging deformation and the forging termination temperature of the last fire of a forging in the forging process to enable the final forging temperature of the forging to be 20-30 ℃ higher than the final forging temperature of the material, rapidly cooling the forging to 650-700 ℃ in air, sending the forging into a heat treatment furnace to be uniform until the internal temperature and the external temperature of the forging are the same, heating the forging to 60-50 ℃ or higher than Ac3 or Acm of the material, keeping the temperature to be completely austenitized, and taking the forging out of the furnace to be cooled to room temperature at a certain cooling speed. In the method, the forge piece needs to be reheated, the complexity of the process flow is increased, and the energy cost is high. In addition, a bainite structure with high hardness is easily obtained in a cooling mode after normalizing in the method, so that subsequent cutting processing is not facilitated, and cutting precision is influenced.
The scholars of Wangming and the like disclose an invention application named as a post-forging waste heat isothermal normalizing process of 42CrMo steel super-large bearing ring forgings (CN 102912092A). The patent proposes that a super-large bearing ring forge piece made of high-temperature 42CrMo steel after forging processing is directly and alternately cooled to 580 ℃ in water and air, and then the super-large bearing ring forge piece is placed into a heat treatment furnace with the temperature of 580 ℃, and is subjected to heat preservation for 2 hours and then is subjected to air cooling. In this method, although several sets of water and air alternate cooling process steps are shown, the actual cooling rate of the method varies with the size of the component, since no specific dimensions are defined for the component. The actual effect of the method cannot be assessed by the person skilled in the art.
In the article published by Liujinxin et al, which indicates that the normalizing cooling speed influences the self-structure and hardness of the 18CrNiMo7-6 gear steel, 18CrNiMo7-6 steel is subjected to heat preservation at the temperature of 870 ℃ and 900 ℃ for 1h, then is cooled to 640-660 ℃ at the cooling speed of less than or equal to 30 ℃/h, then is cooled to 300 ℃ in a furnace, and is then cooled to room temperature in an air cooling mode, so that a pearlite and ferrite combined structure is obtained, and the hardness of the pearlite and ferrite combined structure is 190-210 HB. The method actually heats the forged piece to the austenitizing temperature again, increases the complexity of the process flow and has high energy expenditure.
In the article of 'residual heat isothermal normalizing process discussion after fracture of carburized steel tooth blank' published by the scholars of bovine civilization and the like, 20CrMo, 20CrNiMo and 20CrMnTi gear steel is forged at high temperature, the gear steel is cooled to 650-750 ℃ by using normalizing liquid, then transferred to an isothermal furnace for isothermal at 650-680 ℃, and pearlite and ferrite transformation is generated to obtain a pearlite and ferrite combined structure, wherein the hardness of the pearlite and ferrite combined structure is 160-175 HB. The method actually utilizes the residual heat of high-temperature forging of 20CrMo, 20CrNiMo and 20CrMnTi gear steel, the forging of the 18CrNiMo7-6 steel belongs to the warm forging, and the rest heat is lower than that of the high-temperature forging, so that the method is difficult to obtain the ideal structure and performance of the 18CrNiMo7-6 steel.
In conclusion, the field needs a simple-flow and energy-saving normalizing method for 18CrNiMo7-6 steel, which can make the normalized 18CrNiMo7-6 steel have ideal structure and performance, and lay a good foundation for subsequent further processing such as cutting and carburizing.
Disclosure of Invention
In view of the above problems in the prior art, the present application provides, on one hand, a warm forging waste heat isothermal normalizing method for 18CrNiMo7-6 steel, which enables the normalized 18CrNiMo7-6 steel to have ideal structure and performance, lays a good foundation for subsequent further processing such as cutting and carburizing, and is simple in process flow and energy-saving.
In order to achieve the aim, the warm forging waste heat isothermal normalizing method for the 18CrNiMo7-6 steel comprises the following steps:
-controlled cooling of the 18CrNiMo7-6 steel member to 650 ℃ at a cooling rate of 0.1 to 20 ℃/sec after finish forging of the 18CrNiMo7-6 steel member;
-isothermal incubation of said 18CrNiMo7-6 steel component at 650 ℃ for at least 1 hour;
-cooling the 18CrNiMo7-6 steel material from 650 ℃ to room temperature.
By accurately controlling the cooling rate, the method fully and effectively utilizes the waste heat of the warm forging of the 18CrNiMo7-6 steel, thereby avoiding an additional heating step, simplifying the process and saving the energy consumption. In addition, according to the method, 650 ℃ is selected as the isothermal temperature, so that ferrite and pearlite have short incubation periods, sufficient tissue transformation can occur in a relatively short time, ferrite and pearlite with moderate hardness and therefore beneficial to subsequent cutting processing are obtained, and small and uniform grain size beneficial to subsequent carburizing processing is also obtained; the temperature can also effectively save the heat preservation time, and reduce the energy consumption and the whole normalizing method time.
In some possible implementations of the normalizing method of the present application, the cooling rate of the core of the 18CrNiMo7-6 steel component is made to be 0.1 ℃/sec to 20 ℃/sec during the controlled cooling.
In some possible implementations of the normalizing method of the present application, the core of the 18CrNiMo7-6 steel component is maintained at 650 ℃ for at least 1 hour during the isothermal incubation.
The method of the invention enables a person skilled in the art to select a suitable cooling medium and a suitable cooling mode according to actual manufacturing conditions for components with different sizes by limiting the cooling rate, so as to achieve similar or even identical normalizing effects.
The application also provides an 18CrNiMo7-6 steel component treated by the normalizing method, which has a ferrite and pearlite microstructure and has a Brinell hardness of 163-176 HB.
In some possible implementations of the 18CrNiMo7-6 steel component treated by the normalizing method, the grain size is grade 10 to 15.
The method has the advantages that the warm forging waste heat is fully utilized, the energy consumption is saved, and the time is saved; isothermal normalizing is adopted to reduce heat treatment deformation; can obtain ideal tissue and is beneficial to the subsequent machining and manufacturing processes such as cutting, carburizing treatment and the like.
The foregoing of the present application will be more readily understood in the following description of various embodiments with reference to the accompanying drawings.
Drawings
The drawings of the present application are provided below for the purpose of illustrating the present application in a more intuitive form, and are exemplary and not intended to limit the scope of the present application.
FIG. 1 is a microstructure view of an 18CrNiMo7-6 gear steel after treatment according to one embodiment of a normalizing process of the present application having a cooling rate of 0.1 deg.C/sec, the view being magnified 500 times.
FIG. 2 is a microstructure view of an 18CrNiMo7-6 gear steel after treatment according to another normalizing process example of the present application, having a cooling rate of 1 deg.C/sec, the view being magnified 500 times.
FIG. 3 is a microstructure view of an 18CrNiMo7-6 gear steel after treatment according to another normalizing process embodiment of the present application having a cooling rate of 20 deg.C/sec at a 500-fold magnification.
Detailed Description
In order that the application may be more readily understood, the application is further described below in connection with specific embodiments. The experimental methods described in the application are conventional methods unless otherwise specified; the materials mentioned are commercially available unless otherwise specified. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. In the case of inconsistency, the meaning described in the present specification or the meaning derived from the content described in the present specification shall control. In addition, the terminology used herein is for the purpose of describing embodiments of the present application only and is not intended to be limiting of the present application.
To accurately describe the technical contents in the present application and to accurately understand the present invention, the words and terms used in the present specification are explained or defined as follows before describing the embodiments.
The words "one embodiment" or "an embodiment" as used in this specification means that a particular feature, step, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, steps or characteristics may be combined in any suitable manner in one or more embodiments, as would be apparent to one of ordinary skill in the art from this disclosure.
The term "18 CrNiMo7-6 steel" as used in the specification and claims refers to an alloy steel with alloying elements of 0.15 wt% to 0.21 wt% C, 0.50 wt% to 0.90 wt% Mn, 1.50 wt% to 1.80 wt% Cr, 0.25 wt% to 0.35 wt% Mo, and 1.40 wt% to 1.70 wt% Ni. The alloy steel is suitable for manufacturing gears or gear shafts, and is also called 18CrNiMo7-6 gear steel in the invention.
The term "normalizing" as used in the specification and claims refers to a heat treatment in which the steel is heated to a temperature 30 to 50 ℃ above the Ac3 temperature and then held for a period of time for tapping and air cooling.
< example 1>
Adopting a Gleeble-3800 thermal simulation testing machine, the sample size of 18CrNiMo7-6 steel:
the method comprises the following steps:
putting the sample into a sample cabin, and vacuumizing;
heating to 830 ℃ at a speed of 10 ℃/s, preserving heat for 10min, and then compressing and deforming the sample by 40% to simulate warm forging and finish forging of 18CrNiMo7-6 steel;
air is used as a cooling medium, the air is coordinated with resistance heating, and the sample is cooled to 650 ℃ in the sample cabin at the cooling rate of 0.1 ℃/s;
keeping the temperature of the sample isothermal at 650 ℃ for 1 hour;
cooling the sample from 650 ℃ to room temperature in the sample chamber by using air as a cooling medium;
and (3) longitudinally cutting the obtained sample along the axial direction, polishing and corroding the longitudinal section, and observing the structure and detecting the performance, wherein the results are respectively shown in a figure 1 and a table 1.
< example 2>
Adopting a Gleeble-3800 thermal simulation testing machine, the sample size of 18CrNiMo7-6 steel:
the method comprises the following steps:
putting the sample into a sample cabin, and vacuumizing;
heating to 830 ℃ at a speed of 10 ℃/s, preserving heat for 10min, and then compressing and deforming the sample by 40% to simulate warm forging and finish forging of 18CrNiMo7-6 steel;
air is used as a cooling medium and is coordinated with resistance heating, and the sample is cooled to 650 ℃ at the cooling rate of 1 ℃/s in a sample cabin;
keeping the temperature of the sample isothermal at 650 ℃ for 1 hour;
cooling the sample from 650 ℃ to room temperature in the sample bin by using air as a cooling medium;
and (3) longitudinally cutting the obtained sample along the axial direction, polishing and corroding the longitudinal section, and observing the structure and detecting the performance, wherein the results are respectively shown in a figure 2 and a table 1.
< example 3>
Adopting a Gleeble-3800 thermal simulation testing machine, the sample size of 18CrNiMo7-6 steel:
the method comprises the following steps:
putting the sample into a sample cabin, and vacuumizing;
heating to 830 ℃ at a speed of 10 ℃/s, preserving heat for 10min, and then compressing and deforming the sample by 40% to simulate warm forging and finish forging of 18CrNiMo7-6 steel;
air is used as a cooling medium, the air is coordinated with resistance heating, and the sample is cooled to 650 ℃ at the cooling rate of 20 ℃/s in a sample cabin;
keeping the temperature of the sample isothermal at 650 ℃ for 1 hour;
cooling the sample from 650 ℃ to room temperature in the sample bin by using air as a cooling medium;
and (3) longitudinally cutting the obtained sample along the axial direction, polishing and corroding the longitudinal section, and observing the structure and detecting the performance, wherein the results are respectively shown in a figure 3 and a table 1.
TABLE 1
As can be seen from FIGS. 1 to 3 and Table 1, the gear steels treated by the above normalizing method examples all have a ferrite-pearlite combined structure, have moderate Brinell hardness of 163 to 176HB, and are easy for subsequent cutting. In addition, the grain size of the structure is more than 10 grades, and the level of the banded structure is 1-1.5 grades, so that the method is particularly favorable for subsequent carburizing treatment.
Claims (5)
1. A warm forging waste heat isothermal normalizing method for 18CrNiMo7-6 steel comprises the following steps:
-controlled cooling of the 18CrNiMo7-6 steel member to 650 ℃ at a cooling rate of 0.1 to 20 ℃/sec after finish forging of the 18CrNiMo7-6 steel member;
-isothermal incubation of said 18CrNiMo7-6 steel component at 650 ℃ for at least 1 hour;
-cooling the 18CrNiMo7-6 steel material from 650 ℃ to room temperature.
2. The warm forging waste heat isothermal normalizing method according to claim 1, wherein a cooling rate of a core of the 18CrNiMo7-6 steel member is made to be 0.1 ℃/sec to 20 ℃/sec during the controlled cooling.
3. The warm forging waste heat isothermal normalizing method according to claim 1, wherein the core of the 18CrNiMo7-6 steel member is maintained at 650 ℃ for at least 1 hour during the isothermal heat preservation period.
4. A steel member of 18CrNiMo7-6 treated by the normalizing method according to any one of claims 1 to 3, having a ferrite and pearlite microstructure and having a Brinell hardness of 163 to 176 HB.
5. A steel member as claimed in claim 4 of 18CrNiMo7-6 where the grain size is grade 10 to 15.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210044151.1A CN114507769A (en) | 2022-01-14 | 2022-01-14 | Warm forging waste heat isothermal normalizing method for 18CrNiMo7-6 steel |
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| CN202210044151.1A CN114507769A (en) | 2022-01-14 | 2022-01-14 | Warm forging waste heat isothermal normalizing method for 18CrNiMo7-6 steel |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115094309A (en) * | 2022-06-06 | 2022-09-23 | 东风商用车有限公司 | Cr-Ni-Mo carburizing steel containing Nb, heat treatment method and part |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102912092A (en) * | 2012-11-14 | 2013-02-06 | 洛阳Lyc轴承有限公司 | After-forging waste heat isothermal normalizing technology for 42CrMo steel extra large size bearing ring forge piece |
| CN105886717A (en) * | 2016-04-30 | 2016-08-24 | 王中忞 | Normalizing method for forging waste heat of steel |
| WO2018006843A1 (en) * | 2016-07-06 | 2018-01-11 | 马钢(集团)控股有限公司 | Low cost lean production bainitic steel wheel for rail transit, and manufacturing method therefor |
-
2022
- 2022-01-14 CN CN202210044151.1A patent/CN114507769A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102912092A (en) * | 2012-11-14 | 2013-02-06 | 洛阳Lyc轴承有限公司 | After-forging waste heat isothermal normalizing technology for 42CrMo steel extra large size bearing ring forge piece |
| CN105886717A (en) * | 2016-04-30 | 2016-08-24 | 王中忞 | Normalizing method for forging waste heat of steel |
| WO2018006843A1 (en) * | 2016-07-06 | 2018-01-11 | 马钢(集团)控股有限公司 | Low cost lean production bainitic steel wheel for rail transit, and manufacturing method therefor |
Non-Patent Citations (1)
| Title |
|---|
| 王会诊: "18CrNiMo7-6 齿轮钢温锻后余热等温正火工艺", 金属热处理, vol. 45, no. 11, pages 78 - 82 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115094309A (en) * | 2022-06-06 | 2022-09-23 | 东风商用车有限公司 | Cr-Ni-Mo carburizing steel containing Nb, heat treatment method and part |
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