CN116555680A - Steel for high-strength speed reducer gear of new energy automobile and manufacturing method thereof - Google Patents
Steel for high-strength speed reducer gear of new energy automobile and manufacturing method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 112
- 239000010959 steel Substances 0.000 title claims abstract description 112
- 239000003638 chemical reducing agent Substances 0.000 title claims abstract description 28
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 15
- 238000000034 method Methods 0.000 claims abstract description 37
- 238000009749 continuous casting Methods 0.000 claims abstract description 35
- 238000005096 rolling process Methods 0.000 claims abstract description 32
- 238000010438 heat treatment Methods 0.000 claims abstract description 23
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 13
- 230000007547 defect Effects 0.000 claims abstract description 13
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 9
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 7
- 238000009849 vacuum degassing Methods 0.000 claims abstract description 6
- 239000012535 impurity Substances 0.000 claims abstract description 4
- 238000010791 quenching Methods 0.000 claims abstract description 4
- 230000000171 quenching effect Effects 0.000 claims abstract description 4
- 238000005496 tempering Methods 0.000 claims abstract description 4
- 230000008569 process Effects 0.000 claims description 24
- 238000005266 casting Methods 0.000 claims description 16
- 238000001816 cooling Methods 0.000 claims description 12
- 239000000463 material Substances 0.000 claims description 10
- 239000002245 particle Substances 0.000 claims description 8
- 229910000859 α-Fe Inorganic materials 0.000 claims description 8
- 229910001562 pearlite Inorganic materials 0.000 claims description 5
- 239000013078 crystal Substances 0.000 claims description 4
- 238000001556 precipitation Methods 0.000 claims description 4
- 230000009466 transformation Effects 0.000 claims description 3
- 238000000137 annealing Methods 0.000 claims description 2
- 238000004321 preservation Methods 0.000 claims description 2
- 238000005242 forging Methods 0.000 claims 2
- 238000007670 refining Methods 0.000 abstract description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 8
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 6
- 239000010955 niobium Substances 0.000 description 6
- 229910052782 aluminium Inorganic materials 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 238000010273 cold forging Methods 0.000 description 4
- 229910052750 molybdenum Inorganic materials 0.000 description 4
- 239000011733 molybdenum Substances 0.000 description 4
- 238000003723 Smelting Methods 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 229910052759 nickel Inorganic materials 0.000 description 3
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 3
- 229910000510 noble metal Inorganic materials 0.000 description 3
- 239000003921 oil Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 229910003298 Ni-Ni Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000005422 blasting Methods 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- GNVXPFBEZCSHQZ-UHFFFAOYSA-N iron(2+);sulfide Chemical compound [S-2].[Fe+2] GNVXPFBEZCSHQZ-UHFFFAOYSA-N 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
- 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
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
-
- 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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- 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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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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 Steel (AREA)
Abstract
The invention relates to steel for a high-strength speed reducer gear of a new energy automobile and a manufacturing method thereof. The steel for gears comprises, by mass, 0.13-0.18% of C, less than or equal to 0.15% of Si, 1.10-1.35% of Mn, 1.20-1.45% of Cr, less than or equal to 0.012% of P, less than or equal to 0.003% of S, 0.15-0.35% of Ni, 0.05-0.20% of Mo, 0.015-0.050% of Al, 0.015-0.050% of Nb, and N:0.0085-0.0225%, B0.0015-0.0035%, and the balance of Fe and unavoidable impurities. The steel for the high-strength speed reducer gear of the new energy automobile is manufactured through the process steps of primary refining, vacuum degassing, continuous casting, hot conveying, rolling, isothermal heat treatment and the like, the banded structure of the steel is less than or equal to 1.5 level, the hardness of the steel is less than or equal to 160HBW, the austenite grain size of the steel is more than or equal to 8 level, no crack defect exists on the surface of the steel, and the tensile strength of the steel after oil quenching at 870 ℃ and tempering at 200 ℃ is more than or equal to 1180MPa.
Description
Technical Field
The invention belongs to the technical field of special steel smelting, and particularly relates to steel for a high-strength speed reducer gear of a new energy automobile and a manufacturing method thereof.
Background
The rotation speed of the new energy automobile speed reducer gear is very high in the transmission process, the rotation speed of the new energy automobile speed reducer gear with high quality can even reach more than 10000r/min, and the gear continuously bears larger external force in the high-speed running process. The gear of the new energy automobile speed reducer must have higher strength, better organization uniformity and good assembly precision so as to ensure that the new energy automobile speed reducer has longer fatigue life. The corresponding steel must possess excellent band structure, low hardness, no surface crack defect to facilitate cold forging of the steel, fine austenite grains, and high strength.
Patent number CN112981271A discloses a manufacturing method of steel for gears of electric automobile speed reducers, belongs to the technical field of iron-based alloys, and particularly relates to steel for gears. The design of the element components is as follows: the weight percentage is as follows: 0.20 to 0.35 percent, si:0.05 to 0.35 percent, mn:1.20 to 1.60 percent, cr:1.10 to 1.50 percent, mo:0.20 to 0.50 percent, S: less than or equal to 0.035 percent, P: less than or equal to 0.015 percent, cu: less than or equal to 0.20 percent, ni: less than or equal to 0.20 percent, al: 0.010-0.080%, N: 0.0060-0.0260%, al/N1.5-3.9%, and Fe and unavoidable impurities in balance. The smelting process flow comprises the following steps: pretreated molten iron and preferable scrap steel, primary refining in an electric furnace, refining in an LF furnace, vacuum degassing in a VD furnace, casting square billets continuously, shot blasting of the casting square billets continuously, heating in a step heating furnace, descaling by high-pressure water, rolling of the casting square billets, surface flaw detection of hot rolled round steel, internal ultrasonic flaw detection, quality inspection and warehousing. The element components are matched with the smelting process, so that the requirements of high strength and high fatigue life of the steel for the electric automobile speed reducer are met, and meanwhile, obvious advantages are obtained in the aspects of hardenability and grain uniformity.
Disclosure of Invention
The invention aims to solve the technical problem of providing steel for a high-strength speed reducer gear of a new energy automobile and a manufacturing method thereof aiming at the prior art so as to ensure that the steel has fine austenite grains and higher tensile strength.
The invention solves the problems by adopting the following technical scheme: the steel for the gear of the high-strength speed reducer of the new energy automobile comprises, by weight, 0.13-0.18% of C, less than or equal to 0.15% of Si, 1.10-1.35% of Mn, 1.20-1.45% of Cr, less than or equal to 0.012% of P, less than or equal to 0.003% of S, 0.15-0.35% of Ni, 0.05-0.20% of Mo, 0.015-0.050% of Al, 0.015-0.050% of Nb, and N:0.0085-0.0225%, B0.0015-0.0035%, and the balance of Fe and unavoidable impurities.
The steel strip structure is less than or equal to 1.5 level, the hardness of the steel is less than or equal to 160HBW, the austenite grain size of the steel is more than or equal to 8 level, the surface of the steel has no crack defect, and the tensile strength of the steel after 870 ℃ oil quenching and 200 ℃ tempering is more than or equal to 1180MPa.
The main functions and design basis of the steel are as follows:
carbon is the most important element affecting the strength of steel. The higher the carbon content, the higher the tensile strength of the steel; the hardness of the steel material is also increased. In order to ensure that the steel has lower hardness, the invention adopts a low-carbon design, and the carbon content selection range is 0.13-0.18%.
Si the steel grade of the invention is used for cold forging, and in order to prevent cold work hardening phenomenon in the cold forging process, the silicon content in the steel needs to be strictly controlled. The silicon content of the invention is selected in the range of Si less than or equal to 0.15 percent.
Mn is an element formed by carbide, and enters cementite to replace a part of iron atoms, so that the Mn can reduce the critical transition temperature in steel, play a role in refining pearlite and indirectly play a role in improving the strength of the pearlite. The Mn content in the invention is selected to be 1.10-1.35%.
Cr, cr and Cr can increase the hardenability and strength of steel, but the hardness of steel can be increased. The Cr content in the invention is selected to be 1.20-1.45%.
The invention belongs to cold forging steel, and phosphorus can obviously reduce the tensile strength of the steel, in particular to the steel which is more serious at low temperature. The phosphorus content of the invention is selected in the range of P less than or equal to 0.012 percent.
S sulfur is present in the steel of the invention in the form of iron sulfide (FeS), which forms a low melting point (985 ℃) compound with Fe. The continuous casting withdrawal and rolling process can lead to cracking of the steel surface due to premature melting of FeS compounds. The S content of the invention is selected in the range of S less than or equal to 0.003 percent.
The Ni-Ni element can improve the tensile strength of the steel. However, nickel belongs to the noble metals. The Ni content of the invention is selected to be 0.15-0.35%.
Mo is molybdenum, so that the tensile strength of the steel can be effectively improved. Molybdenum, however, is a noble metal. The Mo content of the invention is selected to be 0.05-0.20%.
Al, N and Nb, wherein the combination of aluminum and oxygen in steel plays a role in deoxidizing, alN formed by the combination of aluminum and nitrogen can play a role in refining the grain size of steel, and NbN formed by the combination of niobium and nitrogen also plays a role in refining the grain size of steel. The invention has the Al content of 0.015-0.050%, the N content of 0.0085-0.0225% and the Nb content of 0.015-0.050%.
B, boron has the main function of increasing the hardenability of steel and improving the tensile strength of the steel, thereby saving other noble metals. The content of B in the invention is selected from 0.0015-0.0035 percent.
The steel for the high-strength speed reducer gear of the new energy automobile and the manufacturing method thereof comprise the following process steps:
molten steel smelted by adopting a primary smelting-refining-vacuum degassing process mode is hoisted to a continuous casting platform for casting, a continuous casting crystallizer is cooled in a forced cooling mode, so that a high-strength chilling layer with the thickness of more than 10mm is formed on the surface of a casting blank, the chilling layer consists of small equiaxed crystal belts with different orientations, and the small equiaxed crystal belts with high strength ensure that surface crack defects are not generated in the subsequent withdrawal and straightening process of a continuous casting blank. In order to prevent the surface of the continuous casting blank from generating excessive stress in the cooling process, the continuous casting blank adopts a hot-feeding process, and the hot-feeding temperature is more than or equal to 600 ℃.
And (3) conveying the continuous casting billet with no crack defect on the surface and low stress into a heating furnace to heat to 1180-1280 ℃. The heated continuous casting blank is required to undergo three-stage rolling deformation of rough rolling, medium rolling and finish rolling, and the temperature of the rolling deformation process of the three stages is required to be carried out at a relatively high plastic temperature, so that the method for determining the high plastic temperature comprises the following steps: the continuous casting blank is heated to different temperatures (the heating temperature interval is 750-1100 ℃), then the continuous casting blank is forged by the same force, and the high plastic temperature can be realized after the continuous casting blank is forged. The lower stress on the surface of the rolled material ensures that the surface of the casting blank cannot crack in the heating process; the rolling deformation at high plastic temperature ensures that the surface of the material does not generate crack defects in the rolling process.
The rolled steel is sent into an isothermal furnace to be subjected to isothermal heat treatment, the isothermal heat treatment is divided into three stages, the first stage is isothermal normalizing treatment, the stage aims to fully precipitate NbC and AlN particles which are not completely precipitated in the rolled material in the shortest time, and the method for determining the optimal normalizing heat preservation temperature is to observe the precipitation rate of the NbC and AlN particles in the rolled material at different temperatures by using a scanning electron microscope in the range of 850-950 DEG CWhen the NbC and AlN particles have the highest precipitation rate, the temperature is the optimal normalizing temperature; the second stage is quick cooling, the temperature drop speed of the steel is more than or equal to 10 ℃/s, and the steel is quickly cooled to Ar 1 Temperature (Ar of the present invention) 1 The temperature is below 705 ℃ and is 20 ℃, and the aim of the stage is to reduce the strip-shaped proeutectoid ferrite which is firstly precipitated before the proeutectoid transformation of the steel; the third stage is isothermal annealing treatment, and the purpose of the stage is Ar 1 The temperature is kept below 20 ℃ for a period of time, so that the austenite structure is completely transformed into a fine and uniformly distributed ferrite and pearlite structure, and the banding of the steel is reduced. And finally, air cooling, wherein the hardness of the steel is reduced to below 160 HBW.
Aiming at the steel for the high-strength speed reducer gear of the new energy automobile, the invention designs low carbon for components, adds a proper amount of nickel and molybdenum elements, and adds a trace amount of aluminum, nitrogen and niobium elements, and the AlN and NbN quality is fully separated out through a subsequent heat treatment process, so that the steel is ensured to have fine austenite grains and higher tensile strength. In the continuous casting process, a casting blank adopts a forced cooling process in a crystallizer, so that a high-strength chilling layer with the thickness of more than 10mm is formed on the surface of the casting blank; the continuous casting blank adopts a hot delivery process so as to reduce the stress on the surface of the casting blank; and (3) performing rough rolling, medium rolling and finish rolling on the continuous casting blank at a high plastic temperature, so as to ensure that the surface of the produced steel has no crack defect. The rolled steel is subjected to three-stage isothermal heat treatment, and the effect is that (1) NbC and AlN particles are fully precipitated at the fastest speed; (2) reducing the strip-shaped proeutectoid ferrite which is firstly precipitated before the eutectoid transformation of the steel; (3) the austenite structure is completely transformed into fine and uniformly distributed ferrite and pearlite structure, thereby reducing the banding of the steel and reducing the hardness of the steel to 160HBW or less. Finally produced steel for the high-strength speed reducer gear of the new energy automobile is characterized in that: the strip-shaped structure of the steel is less than or equal to 1.5 level, the hardness of the steel is less than or equal to 160HBW, the austenite grain size of the steel is more than or equal to 8 level, the surface of the steel has no crack defect, and the tensile strength of the steel after 870 ℃ oil quenching and 200 ℃ tempering is more than or equal to 1180MPa.
Compared with the prior art, the invention has the advantages that:
aiming at the steel for the high-strength speed reducer gear of the new energy automobile, the invention adopts a low-carbon design on components, adds a proper amount of nickel and molybdenum elements, and adds a trace amount of aluminum, nitrogen and niobium elements, and the quality of AlN and NbN is fully separated out through a subsequent heat treatment process, so that the steel is ensured to have fine austenite grains and higher tensile strength. Immediately adopting a forced cooling process after a casting blank with high temperature in the continuous casting process leaves a crystallizer, and promoting the surface of the casting blank to form a high-strength chilling layer with the thickness of more than 10 mm; the continuous casting blank adopts a hot delivery process so as to reduce the stress on the surface of the casting blank; and (3) performing rough rolling, medium rolling and finish rolling on the continuous casting blank at a high plastic temperature, so as to ensure that the surface of the produced steel has no crack defect. The rolled steel is subjected to three-stage isothermal heat treatment, and the effect of each stage is that (1) NbC and AlN particles are fully precipitated at the fastest rate (2) to form a fine and uniformly distributed ferrite structure, thereby reducing the ferrite band structure. (3) The hardness of the steel is reduced to 160HBW or less. The steel for the high-strength speed reducer gear of the new energy automobile is successfully manufactured through reasonable steelmaking, steel rolling and isothermal heat treatment processes, and fills the domestic blank.
Drawings
FIG. 1 is a longitudinal strip (X100 times) of example 1 of the present invention, the strip grade being 0.5.
FIG. 2 is a longitudinal strip (X100 times) of example 2 of the present invention, the strip grade being 0.5.
Detailed Description
The technical scheme of the present invention will be described in more detail in connection with the preferred embodiments of the present invention. However, these examples are merely illustrative of preferred embodiments of the present invention and are not intended to limit the scope of the present invention in any way.
Example 1 and example 2:
the two embodiments relate to a steel manufacturing method for the high-strength speed reducer gear of the new energy automobile, which comprises the following steps: primary refining in a 100t electric furnace, refining in a 100t refining furnace, vacuum degassing in a VD furnace, continuous casting billet (300 mmX340 mm), hot feeding of continuous casting billet, heating of continuous casting billet, rough rolling, middle rolling, finish rolling and isothermal heat treatment in an isothermal furnace. Two batches of steel for the high-strength speed reducer gear of the new energy automobile are manufactured.
Molten steel smelted by adopting an electric furnace-refining-vacuum degassing process is hoisted to a continuous casting platform for casting, a casting blank is forced to cool after exiting a crystallizer, and the thickness of a surface chilling layer is 15mm (example 1) and 17mm (example 2); the hot-cast strand temperature was 633 ℃ (example 1), 626 ℃ (example 2).
And (5) heating the continuous casting blank to 1180-1280 ℃ in a heating furnace. The heated continuous casting slab was subjected to three-stage rolling including rough rolling, intermediate rolling and finish rolling to obtain a product having a diameter of 52mm (example 1) and a diameter of 95mm (example 2), the rough rolling temperature was 1050 ℃, the intermediate rolling temperature was 1000 ℃, and the finish rolling temperature was 975 ℃.
The rolled steel is sent into an isothermal furnace for isothermal heat treatment, isothermal normalizing treatment is carried out in the first stage, the isothermal temperature is 925 ℃, and the isothermal time is 52min (example 1) and 95min (example 2); the steel material in the second stage is cooled by strong wind, the temperature drop speed is 12 ℃/s (example 1) and 11 ℃/s (example 2), the steel material is rapidly cooled to 685 ℃, the temperature is kept for 208min (example 1) and 380min (example 2), and finally the steel material is discharged from the furnace for air cooling.
The chemical compositions of the steels prepared in examples 1 and 2 are shown in Table 1;
TABLE 1 (wt%)
The steel products prepared in examples 1 and 2 were free of any crack defects on the surface, and the band structure grade, hardness and austenite grain size grade of the steel products are shown in Table 2;
TABLE 2
| Specification of specification | Band tissue (level) | Hardness of steel material | Austenite grain size (grade) | |
| Example 1 | Φ52mm | 0.5 | 147HBW | 8.5 |
| Example 2 | Φ95mm | 0.5 | 158HBW | 9.0 |
The steels prepared in examples 1 and 2 were oil quenched at 870 ℃ and tempered at 200 ℃, and the tensile strengths of the steels are shown in Table 3;
TABLE 3 Table 3
| Specification of specification | Tensile strength of | |
| Example 1 | Φ52mm | 1198MPa |
| Example 2 | Φ95mm | 1287MPa |
While the preferred embodiments of the present invention have been described in detail, it is to be clearly understood that the same may be varied in many ways by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. The steel for the high-strength speed reducer gear of the new energy automobile is characterized by comprising, by weight, 0.13-0.18% of C, less than or equal to 0.15% of Si, 1.10-1.35% of Mn, 1.20-1.45% of Cr, less than or equal to 0.012% of P, less than or equal to 0.003% of S, 0.15-0.35% of Ni, 0.05-0.20% of Mo, 0.015-0.050% of Al, 0.015-0.050% of Nb and N:0.0085-0.0225%, B0.0015-0.0035%, and the balance of Fe and unavoidable impurities.
2. The steel for the high-strength speed reducer gear of the new energy automobile, which is disclosed in claim 1, is characterized in that the banded structure of the steel for the gear is less than or equal to 1.5 level, the hardness of the steel is less than or equal to 160HBW, the austenite grain size of the steel is more than or equal to 8 level, the surface of the steel has no crack defect, and the tensile strength of the steel after 870 ℃ oil quenching and 200 ℃ tempering is more than or equal to 1180MPa.
3. A method for manufacturing the steel for the high-strength speed reducer gear of the new energy automobile according to claim 1, which is characterized by comprising the following main steps:
1) Molten steel smelted by adopting a primary smelting-refining-vacuum degassing process mode is hoisted to a continuous casting platform for casting;
2) The continuous casting billet with no crack defect on the surface and low stress is sent into a heating furnace to be heated to 1180-1280 ℃, and the heated continuous casting billet is required to undergo three-stage rolling deformation of rough rolling, intermediate rolling and finish rolling;
3) The rolled steel is sent into an isothermal furnace for isothermal heat treatment, the isothermal heat treatment is divided into three stages, the first stage is isothermal normalizing treatment, and the purpose of the stage is to fully separate out all NbC and AlN particles which are not completely separated out in the rolled steel in the shortest time; the second stage is quick cooling, and the purpose of the second stage is to reduce strip-shaped proeutectoid ferrite precipitated before proeutectoid transformation of the steel; the third stage is isothermal annealing treatment, and the purpose of the stage is Ar 1 Keeping the temperature below 20 ℃ for a period of time to ensure that the austenite structure is completely converted into a fine ferrite and pearlite structure which are uniformly distributed, thereby reducing the banding of the steel, and finally air-cooling to reduce the hardness of the steel to below 160 HBW.
4. The method for manufacturing the steel for the high-strength speed reducer gear of the new energy automobile, which is disclosed in claim 3, is characterized in that a continuous casting crystallizer is cooled in a forced cooling mode, so that a high-strength chilling layer with the thickness of more than 10mm is formed on the surface of a casting blank, the chilling layer consists of small equiaxed crystal belts with different orientations, and the small equiaxed crystal belts with higher strength ensure that surface crack defects are not generated in the subsequent withdrawal and straightening process of the continuous casting blank.
5. The method for manufacturing the steel for the high-strength speed reducer gear of the new energy automobile according to claim 4, wherein the hot-feeding process is adopted for the continuous casting billet in order to prevent excessive stress on the surface of the continuous casting billet in the cooling process, and the hot-feeding temperature is more than or equal to 600 ℃.
6. A method for manufacturing steel for high-strength reduction gears for new energy vehicles according to claim 3, characterized in that the three-stage rolling deformation process temperatures are all carried out at relatively high plastic temperatures, and the method for determining the high plastic temperatures comprises the following steps: and heating the continuous casting blank to different temperatures, forging the continuous casting blank with the same force, and realizing high deformation, namely high plastic temperature, after forging the continuous casting blank.
7. The method for manufacturing steel for high-strength speed reducer gears for new energy vehicles according to claim 6, wherein the temperature for heating the continuous casting is 750-1100 ℃.
8. The method for manufacturing the steel for the high-strength speed reducer gear of the new energy automobile according to claim 3, wherein the method for determining the optimal normalizing heat preservation temperature during isothermal normalizing treatment is to observe the precipitation rates of NbC and AlN particles in a high-temperature rolled material at different temperatures in a range of 850-950 ℃ by using a scanning electron microscope, and the temperature is the optimal normalizing temperature when the NbC and AlN particles have the highest precipitation rates.
9. The method for manufacturing steel for high-strength speed reducer gear of new energy automobile according to claim 3, wherein the temperature drop rate of steel in the rapid cooling stage is not less than 10 ℃/s, and the steel is rapidly cooled to Ar 1 20 ℃ below the temperature Ar 1 The temperature was 705 ℃.
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| CN202310375533.7A CN116555680A (en) | 2023-04-11 | 2023-04-11 | Steel for high-strength speed reducer gear of new energy automobile and manufacturing method thereof |
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| CN202310375533.7A CN116555680A (en) | 2023-04-11 | 2023-04-11 | Steel for high-strength speed reducer gear of new energy automobile and manufacturing method thereof |
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