WO2022184087A1 - 一种冷锻齿轮钢及其制造方法 - Google Patents

一种冷锻齿轮钢及其制造方法 Download PDF

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Publication number
WO2022184087A1
WO2022184087A1 PCT/CN2022/078754 CN2022078754W WO2022184087A1 WO 2022184087 A1 WO2022184087 A1 WO 2022184087A1 CN 2022078754 W CN2022078754 W CN 2022078754W WO 2022184087 A1 WO2022184087 A1 WO 2022184087A1
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Prior art keywords
steel
gear steel
forged gear
cold forged
cold
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PCT/CN2022/078754
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English (en)
French (fr)
Inventor
章军
赵四新
高加强
王维
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Baoshan Iron and Steel Co Ltd
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Baoshan Iron and Steel Co Ltd
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Priority to EP22762550.6A priority Critical patent/EP4276212A4/en
Priority to AU2022230618A priority patent/AU2022230618B2/en
Priority to US18/278,386 priority patent/US20240318276A1/en
Priority to KR1020237028801A priority patent/KR102894291B1/ko
Priority to JP2023552540A priority patent/JP7683024B2/ja
Publication of WO2022184087A1 publication Critical patent/WO2022184087A1/zh
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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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/32—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for gear wheels, worm wheels, or the like
    • 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
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
    • C21D7/10—Modifying the physical properties of iron or steel by deformation by cold working of the whole cross-section, e.g. of concrete reinforcing bars
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J1/00—Preparing metal stock or similar ancillary operations prior, during or post forging, e.g. heating or cooling
    • B21J1/003—Selecting material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
    • B21K1/00—Making machine elements
    • B21K1/28—Making machine elements wheels; discs
    • B21K1/30—Making machine elements wheels; discs with gear-teeth
    • 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
    • C21D1/32—Soft annealing, e.g. spheroidising
    • 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
    • C21D1/84—Controlled slow cooling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0273—Final recrystallisation annealing
    • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0075—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rods of limited length
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • 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
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • 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
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • 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
    • C21D2211/004—Dispersions; Precipitations
    • 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

Definitions

  • the invention relates to a steel material and a manufacturing method thereof, in particular to a cold forging gear steel and a manufacturing method thereof.
  • Gears are a critical part of a car's transmission.
  • the demand for automobile transmissions has remained high for a long time.
  • Cold forging of parts usually has the following advantages: (1) The size and shape accuracy of the near-net shape body are high, which can be used for subsequent efficient and high-precision machining. Provide ideal blanks; (2) For near-net-shaped parts, many parts do not need subsequent processing, which greatly reduces the waste of raw materials; (3) High productivity and low energy consumption can effectively reduce manufacturing costs, shorten manufacturing cycles, and improve product quality.
  • hardenability has always been one of the key requirements of gear steel.
  • the size of the hardenability bandwidth greatly affects the heat treatment deformation. The narrower the hardenability bandwidth and the smaller the discrete range, the more conducive to the processing and improvement of gears. its meshing accuracy.
  • China's national standard GB/T5216-2014 "Guaranteed Hardenability Structural Steel” requires a hardenability bandwidth of more than 10HRC; although the automotive industry has stricter hardenability bandwidth requirements than the national standard, it is limited to a bandwidth of ⁇ 7HRC .
  • the present invention expects to provide a cold forged gear steel, which not only has excellent plasticity and cold working properties, but also has a narrow hardenability bandwidth, so that it can be effectively applied to cold forged gears, and its applicability It is very extensive and has good promotion prospects and application value.
  • One of the objectives of the present invention is to provide a cold forged gear steel, which adopts a reasonable chemical composition design, which not only has suitable strength, but also has excellent plasticity and cold forging performance.
  • Steel has a narrow hardenability bandwidth, and its hardenability at each position (ie, J1.5, J3, J5, J7, and J9) has a bandwidth of less than 4HRC, which can effectively meet the needs and has a wide range of applicability. promotion prospects and application value.
  • J1.5 means the hardness at 1.5mm from the end of the gear steel
  • J3 means the hardness at 3mm from the end of the gear steel
  • J5 means the hardness at 5mm from the end of the gear steel
  • J7 means 7mm from the end of the gear steel
  • J9 represents the hardness at 9mm from the end of the gear steel.
  • the present invention proposes a cold forged gear steel, in addition to Fe and inevitable impurities, the cold forged gear steel also contains the following chemical elements in mass percentage:
  • the cold forged gear steel of the present invention is composed of the following chemical elements in mass percent:
  • C In the cold forged gear steel of the present invention, adding an appropriate amount of C element can ensure that the steel has good hardenability and appropriate strength, and is beneficial to improve the wear resistance of the final part processed from the steel.
  • the C element in the steel should not be too high, because the increase in the content of the C element in the steel will increase the hardness of the steel, which will lead to excessively high material strength in the subsequent processing process, increase the loss of the mold during the cold forging process, and cause downstream Processing costs increase.
  • C is the key element that affects the hardenability.
  • the mass percentage of C element is controlled between 0.15-0.17% .
  • Si element is a ferrite forming element, which has a strong solid solution strengthening effect and can effectively improve the strength of the steel.
  • Si element can also reduce the diffusivity of C in ferrite, so adding an appropriate amount of Si element to steel can avoid the formation of coarse carbides and their precipitation at defects during spheroidizing annealing.
  • the content of Si element in the steel should not be too high. When the content of Si element in the steel is too high, the plasticity of the steel will be reduced. Therefore, in the cold forged gear steel of the present invention, the mass percentage content of Si element is controlled between 0.10-0.20%.
  • Mn In the cold forged gear steel of the present invention, the Mn element is easy to form plastic MnS with the S element in the steel, thereby improving the chip breaking effect and the cutting performance in the subsequent gear finishing process.
  • Mn is the core element that affects the hardenability of the gear steel.
  • the The mass percentage content of Mn element is controlled between 1.0-1.10%.
  • the addition of Cr element to the steel will inhibit the diffusion-type transformation of the steel, which is not conducive to the diffusion nucleation in the spheroidization process. If the content of Cr element in the steel is too high, coarse carbides will be formed and the cold deformation properties will be deteriorated. In addition, Cr can greatly affect the hardenability of gear steel. In order to reduce the fluctuation range of hardenability of gear steel, in the cold forged gear steel of the present invention, the mass percentage of Cr element is controlled within 0.80- between 0.90%.
  • the Al element can form fine AlN precipitates during the steelmaking process, which can inhibit the growth of austenite grains during the subsequent cooling process, thereby effectively refining Austenite grains, to achieve the purpose of improving the toughness of steel at low temperature.
  • the content of Al element in steel should not be too high. Too high content of Al element in steel will lead to the formation of larger Al oxides, which will form B-type inclusions with larger sizes. Coarse alumina hard inclusions will Deteriorating the fatigue resistance of steel can also cause chipping during machining. Based on this, in order to make Al element exert its beneficial effect, in the cold forged gear steel of the present invention, the mass percentage content of Al element is controlled between 0.02-0.04%.
  • the content of impurity elements satisfies at least one of the following: P ⁇ 0.015%, S ⁇ 0.003%, N ⁇ 0.012%, O ⁇ 0.003%, preferably O ⁇ 0.002%, B ⁇ 0.0002%.
  • P, S, N, O and B are all impurity elements in steel. If technical conditions allow, in order to obtain steel with better performance and better quality, impurity elements in steel should be reduced as much as possible. content.
  • the impurity element P can combine with Fe to form a hard and brittle Fe 3 P phase, which makes the steel produce cold brittleness during the cold working process, resulting in poor plasticity of the steel.
  • intergranular fracture occurs and a large cleavage is formed.
  • the P element in the steel will segregate at the grain boundary, reducing the binding energy of the grain boundary and deteriorating the plasticity of the steel. Therefore, in order to prevent the brittleness of the steel from becoming high, in the present invention, the mass percentage content of the P element is controlled to be P ⁇ 0.015%.
  • the impurity element S is easily combined with Fe to form a FeS phase with a melting point of 989°C, which will cause hot brittleness of the steel during hot working. Therefore, in order to avoid hot brittleness of steel, in the present invention, the mass percentage of S is controlled to be S ⁇ 0.003%.
  • the impurity element N can form AlN or TiN in the steel, it can play the role of refining the austenite grains, but the increase of the N element content in the steel will lead to an increase in its enrichment at the defect and the formation of coarse nitrogen.
  • the precipitation particles of the compound will affect the fatigue life of the steel. Therefore, in the present invention, it is necessary to control the mass percentage of N element to be N ⁇ 0.012%.
  • the impurity element O can form compounds such as Al 2 O 3 and TiO with the Al and Ti elements in the steel. Therefore, in order to ensure the uniformity of the steel structure, in the cold forged gear steel of the present invention, the mass percentage content of O is controlled O ⁇ 0.003%, preferably the mass percentage of O is controlled to O ⁇ 0.002%.
  • the impurity element B has a great influence on the hardenability of the material.
  • the B element will segregate at the austenite grain boundary. When the austenite decomposes, it is difficult for the new phase to nucleate at the austenite grain boundary, resulting in austenite decomposition.
  • the growth of the incubation period reduces the rate of diffusive transformation, which is beneficial to martensitic transformation, thereby improving the hardenability of steel, but the position of B segregation is not fixed, which will cause large fluctuations in the hardenability of the material. Therefore, in the present invention, in order to ensure the hardenability of the gear steel, the mass percentage of B is controlled to be B ⁇ 0.0002%.
  • the cold forged gear steel of the present invention further contains at least one of the following chemical elements: 0 ⁇ Ca ⁇ 0.005%, 0 ⁇ Ti ⁇ 0.008%.
  • the above-mentioned Ca and Ti elements can further improve the performance of the cold forged gear steel of the present invention, and the design principle is as follows:
  • Ca In the cold forged gear steel of the present invention, an appropriate amount of Ca element is added to the steel to form CaS, thereby improving the size and morphology of the inclusions and improving the impact toughness of the steel.
  • the Ca element in the steel should not be too high. Therefore, in the present invention, the mass percentage content of the Ca element can be controlled to be 0 ⁇ Ca ⁇ 0.005%.
  • Ti element can form corresponding compounds with C element and N element in the steel, wherein the formation temperature of TiN is above 1400°C, usually in liquid phase or delta ferrite. In order to achieve the purpose of refining austenite grains. However, it should be noted that if the content of Ti element in the steel is too high, coarse TiN precipitates will be formed, which will reduce the fatigue resistance of the steel. Based on this, in the present invention, the mass percentage content of the Ti element can be controlled to be 0 ⁇ Ti ⁇ 0.008%.
  • the microstructure of the cold forged gear steel of the present invention is ferrite+spheroid carbide.
  • the mechanical properties of the cold forged gear steel according to the present invention satisfy: the yield strength is 180-220 MPa, the tensile strength is 380-430 MPa, the elongation rate is ⁇ 37%, and the area reduction rate is ⁇ 68%; and/or the
  • the hardenability of cold forged gear steel meets: J1.5: 38-42HRC, J3: 35-39HRC, J5: 30-34HRC, J7: 26-30HRC, J9: 21-25HRC, and the above hardenability bandwidths are all ⁇ 4HRC.
  • another object of the present invention is to provide a method for manufacturing the above-mentioned cold forged gear steel, which is simple to produce, and the cold forged gear steel obtained by the manufacturing method not only has excellent plasticity and cold working properties, but also has The narrow hardenability requirement of gear steel has good promotion prospect and application value.
  • the present invention proposes the above-mentioned manufacturing method of cold forged gear steel, which comprises the following steps:
  • the manufacturing method of the cold forged gear steel of the present invention by controlling the process conditions, especially the heat treatment process parameters, the forged or rolled bar is controlled and then the spheroidizing annealing process is used, so that the method of the present invention is adopted.
  • the cold forged gear steel prepared by the manufacturing method can obtain the matrix structure of ferrite and spherical carbide, and there is a large amount of ferrite on the matrix, thereby effectively ensuring that the cold forging gear steel of the present invention has good plasticity, eliminating the need for steel. internal stress to obtain good tissue uniformity.
  • step (1) of the manufacturing method of the present invention in the smelting process, electric furnace or converter smelting can be used; in the casting process, die casting or continuous casting can be used.
  • a forging or rolling process can be used. If the forging process is used, it can be directly forged to the final size of the round steel. If the rolling process is used, the billet can also be directly rolled to the final gauge. In certain embodiments, during the rolling process, the steel billet may be rolled to a specified intermediate billet size first, and then the intermediate billet is heated and rolled to obtain the final finished product size.
  • the heating temperature is controlled to be 1080-1200°C.
  • step (2) the steel can be controlled to be heated at a heating temperature of 1080-1200°C to austenitize it, so that the elements of the steel grade can be uniformly diffused and the segregation of the material can be reduced, thereby reducing the segregation of the material.
  • the round steel has good microstructure uniformity, and its hardenability fluctuation is small.
  • step (3) the temperature of final rolling or final forging is controlled to be 860-980°C.
  • step (4) heating to 750-770°C for more than 4 hours, and then cooling to 700-720°C for 3.5h at a cooling rate of 5-15°C/h Above, then cooled to 660-680°C at a cooling rate of 3-12°C/h for more than 3.5h, then cooled to below 500°C at a cooling rate of 5-20°C/h, and then released from the furnace for cooling.
  • the cold forged gear steel and its manufacturing method of the present invention have the following advantages and beneficial effects:
  • the cold forged gear steel of the present invention can form uniform ferrite + spherical carbides through reasonable chemical composition design, making full use of the effects of various alloy elements on phase transformation and microstructure, and cooperating with a specific heat treatment process basal tissue.
  • the invention also effectively controls the content of impurities such as P, N and O in the steel, ensuring that the obtained cold forged gear steel has suitable strength, excellent plasticity and elongation, and has a narrow hardenability bandwidth.
  • the cold forged gear steel of the present invention not only has suitable strength, but also has excellent plasticity and cold forging properties, and the mechanical properties of the cold forged gear steel satisfy: the yield strength is 180-220Mpa, the tensile strength It is 380-430MPa, the elongation rate is ⁇ 37%, and the section shrinkage rate is ⁇ 68%.
  • the cold forged gear steel also has a narrow hardenability bandwidth, and the hardenability of the cold forged gear steel satisfies: J1.5: 38-42HRC, J3: 35-39HRC, J5: 30-34HRC, J7: 26 -30HRC, J9: 21-25HRC, and the above hardenability bandwidths are all ⁇ 4HRC.
  • FIG. 1 is a photo of the microstructure of the cold forged gear steel of Example 4 under an optical microscope.
  • Example 2 is an image photograph of the cold forged gear steel of Example 4 under a scanning electron microscope (SEM).
  • the cold forging gear steels of Examples 1-9 are all prepared by the following steps:
  • Heating control the heating temperature to be 1080-1200°C.
  • the cold forged gear steels of Examples 1-9 of the present invention are all prepared by the above steps, and their chemical compositions and related process parameters all meet the control requirements of the design specifications of the present invention.
  • a forging or rolling process may be used. If the forging process is used, it can be directly forged to the final size of the round bar. If a rolling process is used, billets can also be directly rolled to final gauge. In certain embodiments, during the rolling process, the steel billet may be rolled to a specified intermediate billet size first, and then the intermediate billet is heated and rolled to obtain the final finished product size.
  • Example 6 adopted the rolling process to roll the steel billet in step (3).
  • the finishing temperature was controlled to be 860-980 °C °C; first roll the billet into an intermediate billet with a size of 215*215mm, and then heat the intermediate billet again. After the intermediate billet is out of the heating furnace, the intermediate billet is rolled again to make it into a specification of ⁇ 25- 45mm final finished round bar.
  • Example 6 in the operation of the above-mentioned step (3) in Example 6, a forging process is adopted.
  • the final forging temperature is controlled to be 860-980° C., and the specification is directly forged into a size of ⁇ 25-45mm. The final finished round bar.
  • Table 1 lists the chemical element compositions in mass percent in the cold forged gear steels of Examples 1-9.
  • Table 2-1 and Table 2-2 list the specific process parameters of the cold forged gear steels of Examples 1-9 in the above process steps.
  • the cold forged gear steels of Examples 1-9 were all tested by the method of GB/T 228.1-2010 "Tensile Test of Metal Materials Part 1: Test Method at Room Temperature” to obtain the yield strength, Tensile strength, elongation and reduction of area.
  • Table 3 lists the mechanical properties test results of the cold forged gear steels of Examples 1-9.
  • Table 4 lists the results of hardenability testing of the cold forged gear steels of Examples 1-9.
  • Example 1 Numbering J1.5/HRC J3/HRC J5/HRC J7/HRC J9/HRC Example 1 39.8 37.1 31.7 28.1 22.6
  • Example 2 40.6 37.6 32.2 28.3 23.1
  • Example 3 41.3 38.4 32.5 29 24.1
  • Example 4 39.4 36.8 31.2 28.3 23.6
  • Example 5 40 37.3 30.7 27.5 22.5
  • Example 6 41.6 38.2 31.5 29.5 24.6
  • Example 7 39.6 37 31.2 28.6 23.4
  • Example 8 40.7 37.5 30.4 27.4 22.3
  • Example 9 41.6 38.6 32.1 29.4 24.7
  • J1.5 represents the hardness at a distance of 1.5mm from the end
  • J3 means the hardness at a distance of 3mm from the end
  • J5 means the hardness at a distance of 5mm from the end
  • J7 means The hardness at 7mm from the end
  • J9 represents the hardness at 9mm from the end.
  • the cold forged gear steels of Examples 1-9 have very excellent mechanical properties, and the yield strengths of the cold forged gear steels of Examples 1-9 are all between 182-218MPa, The tensile strength is between 382-426MPa, the elongation rate is ⁇ 37%, and the area shrinkage rate is ⁇ 68%.
  • the mechanical properties of the cold-forged gear steel of each embodiment are very excellent, the steel has good plasticity and area reduction rate at low temperature, and has excellent cold working properties.
  • FIG. 1 is a photo of the microstructure of the cold forged gear steel of Example 4 under an optical microscope.
  • Example 2 is an image photograph of the cold forged gear steel of Example 4 under a scanning electron microscope (SEM).
  • microstructure of the cold forged gear steel of Example 4 of the present invention is ferrite + spherical carbide.
  • the present invention has developed a cold forged gear steel with a narrow hardenability bandwidth through reasonable chemical composition design and combined with an optimized process, which not only has good strength, but also has excellent plasticity. and elongation, it can be effectively applied to cold forging gears, has a wide range of applicability, and has good promotion prospects and application value.
  • the cold forging gear steel of the present invention is reasonable in chemical composition and process design, and has a loose process window, which can realize batch commercial production on bars, and has good promotion prospects and application value.

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Abstract

本发明公开了一种冷锻齿轮钢，除Fe和不可避免的杂质以外，所述冷锻齿轮钢还含有以质量百分比计的如下化学元素：C：0.15-0.17％、Si：0.10-0.20％、Mn：1.0-1.10％、Cr：0.80-0.90％、Al：0.02-0.04％。相应地，本发明还公开了一种上述冷锻齿轮钢的制造方法，其包括以下步骤：(1)冶炼和浇铸；(2)加热；(3)锻造或轧制；(4)球化退火：加热至750-770℃并进行保温，然后以5-15℃/h的冷却速度冷却至700-720℃并进行保温，接着以3-12℃/h的冷却速度冷却至660-680℃并进行保温，随后以5-20℃/h的冷却速度冷却至500℃以下，然后出炉冷却。

Description

一种冷锻齿轮钢及其制造方法 技术领域
本发明涉及一种钢材及其制造方法，尤其涉及一种冷锻齿轮钢及其制造方法。
背景技术
齿轮是汽车变速箱中的一个关键部分。近年来，随着汽车产业的飞速发展，面对更加广阔的汽车市场，汽车变速器的需求量长久居高不下。
由于齿轮的形状较为特殊，对尺寸精度要求较高，很多企业采用热锻加工后精加工的工艺方式进行齿轮生产，但采用这种方法生产齿轮不仅材料的利用率较低，而且在热锻过程中需要的能源消耗较高，如此会大大增加加工成本，造成环境污染。
因此，部分零部件加工企业采用冷锻技术来生产齿轮，零件冷锻加工通常具备以下多方面的优势：(1)近净成形体的尺寸及形位精度高，可以为后续高效、高精加工提供理想的毛坯；(2)对于近净成形零件，很多部分无需后续加工，大大降低了原材料的浪费；(3)生产率高、能源消耗低，可以有效降低制造成本，缩短制造周期，提高产品的竞争力，精密成形产品的性能和质量相对于传统切削加工的产品，有很大提高；(4)零件冷锻技术较传统成形工艺，生产条件得到了改善，对环境的污染大大减少；(5)零件冷锻技术在冷精密成形方面，由于热处理工序的减少和无飞边工艺的进步，能源耗费和污染程度大大降低。由此可见，冷锻这一技术更符合未来清洁制造和绿色环保的趋势，能够为可持续发展创造有利条件。
然而，冷锻技术对材料的塑性要求很高，而齿轮的形状较为复杂，冷锻加工要求材料具备极佳的塑性，因此在采用冷锻技术制造齿轮时经常出现因钢材塑性不足导致挤压过程中发生开裂或者微裂纹萌生的问题，这一问题会导致加工后的零件报废率升高，使后续检测成本上升。
此外，淬透性一直是齿轮钢的关键要求指标之一，淬透性带宽的大小很大 程度上影响热处理变形，淬透性带宽越窄，离散范围越小，越有利于齿轮的加工及提高其啮合精度。目前，中国国家标准GB/T5216-2014《保证淬透性结构钢》对淬透性的要求带宽为10HRC以上；尽管汽车行业对淬透性带宽的要求比国标严格，但也仅限于带宽≤7HRC。随着汽车行业对汽车齿轮精密加工及装配尺寸公差要求的不断提高，缩小齿轮钢的淬透性带宽成为近年来国内外齿轮钢研究的热点，特别是一些精度要求高的冷锻齿轮钢对淬透性的要求更加苛刻。
基于此，本发明期望提供一种冷锻齿轮钢，该冷锻齿轮钢不仅具有优良的塑性和冷加工特性，还具备窄的淬透性带宽，使得其可以有效应用于冷锻加工齿轮，适用性十分广泛，具有良好的推广前景和应用价值。
发明内容
本发明的目的之一在于提供一种冷锻齿轮钢，该冷锻齿轮钢采用了合理的化学成分设计，其不仅具有适宜的强度，还具有优良的塑性和冷锻性能，同时该冷锻齿轮钢具有窄的淬透性带宽，其在各位置处的淬透性(即J1.5、J3、J5、J7和J9)的带宽达到4HRC以内，可以有效满足需求，适用性十分广泛，具有良好的推广前景和应用价值。
需要说明，J1.5表示距齿轮钢端部1.5mm处的硬度，J3表示距齿轮钢端部3mm处的硬度，J5表示距齿轮钢端部5mm处的硬度，J7表示距齿轮钢端部7mm处的硬度，J9表示距齿轮钢端部9mm处的硬度。
为了实现上述目的，本发明提出了一种冷锻齿轮钢，除Fe和不可避免的杂质以外，所述冷锻齿轮钢还含有以质量百分比计的如下化学元素：
C：0.15-0.17％、Si：0.10-0.20％、Mn：1.0-1.10％、Cr：0.80-0.90％、Al：0.02-0.04％。
在一个优选实施方式中，本发明所述的冷锻齿轮钢由以质量百分比计的如下化学元素组成：
C：0.15-0.17％、Si：0.10-0.20％、Mn：1.0-1.10％、Cr：0.80-0.90％、Al：0.02-0.04％；余量为Fe和不可避免的杂质。
在本发明所述的冷锻齿轮钢中，各化学元素的设计原理具体如下所述：
C：在本发明所述的冷锻齿轮钢中，添加适量的C元素，可以保证钢材具 有良好的淬透性和适当的强度，有利于提高钢材加工成最终零件的耐磨性。但需要注意，钢中C元素不宜过高，因为钢中C元素含量提高，会提高钢材的硬度，进而会导致在后续加工过程中材料强度过高，增加冷锻过程中模具的损耗，引起下游加工成本升高。而当钢中C元素含量太低时，则无法保证钢获得较高的抗拉强度，导致齿轮心部的组织强度偏低，齿轮的抗变形能力降低，使齿轮的疲劳寿命降低。因此，C是淬透性影响的关键元素，为了实现齿轮钢的窄淬透性，在本发明所述的冷锻齿轮钢中，将C元素的质量百分含量控制在0.15-0.17％之间。
Si：在本发明所述的冷锻齿轮钢中，Si元素是铁素体形成元素，其具有较强的固溶强化效果，能够有效提高钢材的强度。此外，Si元素还可以降低C在铁素体的中扩散能力，因此钢中添加适量的Si元素可以在球化退火过程中避免粗大碳化物的形成及其在缺陷处的析出。但需要注意，钢中Si元素含量不宜过高，当钢中Si元素含量过高时，会降低钢材的塑性。因此，在本发明所述的冷锻齿轮钢中，将Si元素的质量百分含量控制在0.10-0.20％之间。
Mn：在本发明所述的冷锻齿轮钢中，Mn元素易与钢中的S元素形成塑性的MnS，进而在后续的齿轮精加工过程中提高断屑效果，改善切削性能。但需要注意，钢中Mn元素含量过高同时也会导致钢材的强度上升，硬度上升，在后续冷锻的过程中会加剧模具的损耗。因此，为了改善钢材的易切削性能，同时避免钢的强度偏高，Mn是影响齿轮钢淬透性的核心元素，为降低淬透性波动，在本发明所述的冷锻齿轮钢中，将Mn元素的质量百分含量控制在1.0-1.10％之间。
Cr：在本发明所述的冷锻齿轮钢中，Cr元素添加到钢中，会抑制钢的扩散型相变，不利于球化过程中的扩散形核。若钢中Cr元素含量过高，则会形成粗大的碳化物，恶化冷变形性能。此外，Cr能够较大程度地影响齿轮钢淬透性，为降低齿轮钢的淬透性波动范围，在本发明所述的冷锻齿轮钢中，将Cr元素的质量百分含量控制在0.80-0.90％之间。
Al：在本发明所述的冷锻齿轮钢中，Al元素在炼钢过程时可以形成细小的AlN析出物，其可以在随后的冷却过程中抑制奥氏体晶粒长大，从而有效细化奥氏体晶粒，达到提高钢在低温下的韧性的目的。但需要注意，钢中Al元素含量不宜过高，钢中Al元素含量过高会导致较大的Al的氧化物形成，会形成 尺寸较大的B类夹杂物，粗大的氧化铝硬质夹杂会恶化钢的抗疲劳性能，也会引起机械加工过程中的崩刀现象。基于此，为了使Al元素发挥其有益效果，在本发明所述的冷锻齿轮钢中，将Al元素的质量百分含量控制在0.02-0.04％之间。
优选地，在本发明所述的冷锻齿轮钢中，在不可避免的杂质中，杂质元素的含量满足如下中的至少一种：P≤0.015％、S≤0.003％、N≤0.012％、O≤0.003％，优选O≤0.002％、B≤0.0002％。
在上述技术方案中，P、S、N、O和B均为钢中的杂质元素，在技术条件允许情况下，为了获得性能更好且质量更优的钢材，应尽可能降低钢中杂质元素的含量。
杂质元素P能够和Fe结合形成硬脆的Fe 3P相，使得钢在冷加工过程中产生冷脆性，导致钢的塑性变差，受到冲击载荷的作用时发生沿晶断裂，形成较大的解理面，钢中的P元素会在晶界偏聚，降低晶界的结合能，恶化钢的塑性。因此，为了避免钢的脆性变高，在本发明中，控制P元素的质量百分含量为P≤0.015％。
杂质元素S容易与Fe结合形成熔点989℃的FeS相，其会使钢在热加工过程中产生热脆性。因此，为了避免钢的热脆性，在本发明中，控制S的质量百分含量为S≤0.003％。
杂质元素N虽然可以在钢中形成AlN或TiN，能够起到细化奥氏体晶粒的作用，但钢中N元素含量增加会导致其在缺陷处富集量增加，同时会形成粗大的氮化物析出颗粒，影响钢疲劳寿命。因此，在本发明中，需要控制N元素的质量百分含量为N≤0.012％。
杂质元素O可以与钢中的Al和Ti元素形成Al 2O 3、TiO等化合物，因此，为了保证钢组织均匀性，在本发明所述的冷锻齿轮钢中，控制O的质量百分含量为O≤0.003％，优选控制O的质量百分含量为O≤0.002％。
杂质元素B对材料淬透性的影响极大，B元素会在奥氏体晶界偏聚，奥氏体分解时新相在奥氏体晶界位置难以形核，从而造成奥氏体分解的孕育期增长，从而降低了扩散性相变的速率，有利于马氏体转变，进而提高钢材的淬透性，但是B偏聚的位置不固定，会造成材料的淬透性波动较大。因此，在本发明中，为了保证齿轮钢的淬透性，将B的质量百分含量控制为B≤0.0002％。
优选地，本发明所述的冷锻齿轮钢还含有如下化学元素中的至少一种：0＜Ca≤0.005％、0＜Ti≤0.008％。
在上述技术方案中，上述的Ca、Ti元素可以进一步提高本发明所述的冷锻齿轮钢的性能，其设计原理如下所述：
Ca：在本发明所述的冷锻齿轮钢中，钢中加入适量的Ca元素，可以形成CaS，从而改善夹杂物的尺寸和形貌，提高钢的冲击韧性。但是需要说明，钢中Ca元素不宜过高。因此，在本发明中，可以控制Ca元素的质量百分含量为0＜Ca≤0.005％。
Ti：在本发明所述的冷锻齿轮钢中，Ti元素可以与钢中的C元素和N元素形成对应的化合物，其中TiN的形成温度为1400℃以上，通常在液相或δ铁素体中析出，从而实现细化奥氏体晶粒的目的。但需要注意，若钢中Ti元素含量过高，会形成粗大的TiN析出物，其会导致钢的抗疲劳性能降低。基于此，在本发明中，可以控制Ti元素的质量百分含量为0＜Ti≤0.008％。
需要说明，上述元素的加入会增加材料的成本，综合考虑到性能与成本控制，在本发明所述的技术方案中，可以优选地添加上述元素中的至少一种。
优选地，本发明所述的冷锻齿轮钢的微观组织为铁素体+球状碳化物。
优选地，本发明所述的冷锻齿轮钢的力学性能满足：屈服强度为180-220Mpa，抗拉强度为380-430MPa，延伸率≥37％，断面收缩率≥68％；和/或所述冷锻齿轮钢的淬透性满足：J1.5：38-42HRC，J3：35-39HRC，J5：30-34HRC，J7：26-30HRC，J9：21-25HRC，并且以上淬透性带宽均≤4HRC。
相应地，本发明的另一目的在于提供一种上述冷锻齿轮钢的制造方法，该制造方法生产简单，采用该制造方法制得的冷锻齿轮钢不仅具有优异的塑性和冷加工特性，同时具备齿轮钢的窄淬透性要求，其具有良好的推广前景和应用价值。
为了实现上述目的，本发明提出了上述的冷锻齿轮钢的制造方法，所述方法包括以下步骤：
(1)冶炼和浇铸；
(2)加热；
(3)锻造或轧制；
(4)球化退火：加热至750-770℃并进行保温，然后以5-15℃/h的冷却 速度冷却至700-720℃并进行保温，接着以3-12℃/h的冷却速度冷却至660-680℃并进行保温，随后以5-20℃/h的冷却速度冷却至500℃以下，然后出炉冷却。
在本发明所述的冷锻齿轮钢的制造方法中，通过对工艺条件尤其是热处理工艺参数的控制，控制锻造或轧制好的棒材然后采用球化退火工艺，使得采用本发明所述的制造方法所制得的冷锻齿轮钢可以获得铁素体+球状碳化物的基体组织，基体上有大量的铁素体，从而有效保证了本发明冷锻齿轮钢具有良好的塑性，消除钢材的内应力，获得良好的组织均匀性。
需要注意，在本发明所述制造方法的步骤(1)中，冶炼过程中，可以采用电炉或转炉冶炼；在浇铸过程中，可以采用模铸或连铸。
相应地，在步骤(3)中，可以采用锻造或轧制工艺。若采用锻造工艺可以直接锻造至圆钢最终尺寸。若采用轧制工艺，同样也可以采用钢坯直接轧制到最终规格。在某些实施方式下，在轧制过程中，也可以先将钢坯轧制到指定的中间坯尺寸，而后将中间坯再进行加热和轧制从而得到最终的成品尺寸。
优选地，在本发明所述的制造方法中，在步骤(2)中，控制加热温度为1080-1200℃。
在上述技术方案中，在步骤(2)中，可以控制钢在1080-1200℃的加热温度下加热来使其奥氏体化，钢种的各元素发生均匀化扩散，降低材料的偏析，从而在随后的锻造或轧制和冷却过程中，圆钢的组织均匀性良好，其淬透性波动较小。
优选地，在本发明所述的制造方法中，在步骤(3)中，控制终轧或终锻温度为860-980℃。
优选地，在本发明所述的制造方法中，在步骤(4)中，加热至750-770℃保温4h以上，然后以5-15℃/h的冷却速度冷却至700-720℃保温3.5h以上，接着以3-12℃/h的冷却速度冷却至660-680℃保温3.5h以上，随后以5-20℃/h的冷却速度冷却至500℃以下，然后出炉冷却。
本发明所述的冷锻齿轮钢及其制造方法相较于现有技术具有如下所述的优点以及有益效果：
本发明所述的冷锻齿轮钢，通过合理的化学成分设计，充分利用各种合金元素对相变和微观组织的影响，再配合特定的热处理工艺，可以形成均匀的铁 素体+球状碳化物基体组织。此外，本发明还有效控制了钢中P、N和O等杂质的含量，保证了得到的冷锻齿轮钢具有适合的强度以及优良的塑性和延伸率，同时具备窄的淬透性带宽等。
在本发明中，本发明所述的冷锻齿轮钢不仅具有适宜的强度，还具有优良的塑性和冷锻性能，该冷锻齿轮钢的力学性能满足：屈服强度为180-220Mpa，抗拉强度为380-430MPa，延伸率≥37％，断面收缩率≥68％。同时，该冷锻齿轮钢还具备窄的淬透性带宽，该冷锻齿轮钢的淬透性满足：J1.5：38-42HRC，J3：35-39HRC，J5：30-34HRC，J7：26-30HRC，J9：21-25HRC，并且以上淬透性带宽均≤4HRC。
此外，需要说明，本发明所述冷锻齿轮钢的化学成分和工艺设计合理，其工艺窗口宽松，可以在棒材生产线上实现批量商业化生产，其具有十分广泛的适用性，具有良好的推广前景和应用价值。
附图说明
图1为实施例4的冷锻齿轮钢在光学显微镜下的微观组织照片。
图2为实施例4的冷锻齿轮钢在扫描电子显微镜(SEM)下的图像照片。
具体实施方式
下面将结合说明书附图以及具体的实施例对本发明所述的冷锻齿轮钢及其制造方法做进一步的解释和说明，然而该解释和说明并不对本发明的技术方案构成不当限定。
实施例1-9
实施例1-9的冷锻齿轮钢均采用以下步骤制得：
(1)按照表1所示的化学成分进行冶炼和浇铸：冶炼采用电炉或转炉进行，浇铸过程采用模铸或连铸。
(2)加热：控制加热温度为1080-1200℃。
(3)锻造或轧制：控制终轧或终锻温度为860-980℃。
(4)球化退火：加热至750-770℃并进行保温，然后以5-15℃/h的冷却速度冷却至700-720℃并进行保温，接着以3-12℃/h的冷却速度冷却至660-680℃并进行保温，随后以5-20℃/h的冷却速度冷却至500℃以下，然后 出炉冷却。
本发明所述的实施例1-9的冷锻齿轮钢均采用以上步骤制得，且其化学成分及相关工艺参数均满足本发明的设计规范的控制要求。
需要说明，在上述步骤(3)的锻造或轧制过程中，可以采用锻造或轧制工艺。若采用锻造工艺，则可以直接锻造至圆钢最终尺寸。若采用轧制工艺，则同样也可以采用钢坯直接轧制到最终规格。在某些实施方式下，在轧制过程中，也可以先将钢坯轧制到指定的中间坯尺寸，而后将中间坯再进行加热和轧制从而得到最终的成品尺寸。
在实施例1-9中，除实施例6以外的所有实施例在步骤(3)中均采用轧制工艺对钢坯进行轧制，在轧制工艺的过程中，控制终轧温度为860-980℃；先将钢坯轧制成尺寸规格为215*215mm的中间坯，然后将中间坯再次加热，中间坯出加热炉后，对中间坯再次进行轧制，以将其轧制成规格为φ25-45mm的最终成品圆钢。
相应地，在本发明中，实施例6在上述步骤(3)的操作中，采用的是锻造工艺，实施例6通过控制终锻温度为860-980℃，直接锻造成规格为φ25-45mm的最终成品圆钢。
表1列出了实施例1-9的冷锻齿轮钢中以质量百分比计的化学元素组成。
表1(余量为Fe和除P、S、N、O以及B以外的其他不可避免杂质)
Figure PCTCN2022078754-appb-000001
表2-1和表2-2列出了实施例1-9的冷锻齿轮钢在上述工艺步骤中的具体工艺参数。
表2-1
Figure PCTCN2022078754-appb-000002
表2-2
Figure PCTCN2022078754-appb-000003
将得到的实施例1-9的冷锻齿轮钢取样并进行各项相关性能测试，将所得的性能测试结果分别列于表3中。
其中，实施例1-9的冷锻齿轮钢均采用GB/T 228.1-2010《金属材料拉伸试验第1部分：室温试验方法》的方式进行测试，以检测得到各实施例钢的屈服强度、抗拉强度、延伸率与断面收缩率。
表3列出了实施例1-9的冷锻齿轮钢的力学性能测试结果。
表3
Figure PCTCN2022078754-appb-000004
相应地，力学性能测试完成后，对实施例1-9的冷锻齿轮钢取样并进行淬透性测试，所得的性能测试结果列于表4中。
其中，实施例1-9的冷锻齿轮钢均采用GB/T225-2006《钢淬透性的末端淬火试验方法》进行测试，以检测得到的各实施例中钢的淬透性。
表4列出了实施例1-9的冷锻齿轮钢的淬透性测试的结果。
表4
编号 J1.5/HRC J3/HRC J5/HRC J7/HRC J9/HRC
实施例1 39.8 37.1 31.7 28.1 22.6
实施例2 40.6 37.6 32.2 28.3 23.1
实施例3 41.3 38.4 32.5 29 24.1
实施例4 39.4 36.8 31.2 28.3 23.6
实施例5 40 37.3 30.7 27.5 22.5
实施例6 41.6 38.2 31.5 29.5 24.6
实施例7 39.6 37 31.2 28.6 23.4
实施例8 40.7 37.5 30.4 27.4 22.3
实施例9 41.6 38.6 32.1 29.4 24.7
注：上表中，关于钢的淬透性的表达，J1.5表示距离端部1.5mm处的硬度，J3表示距离端部3mm处的硬度，J5表示距离端部5mm处的硬度，J7表示距离端部7mm处的硬度，J9表示距离端部9mm处的硬度。
由表3可看出，在本发明中，实施例1-9的冷锻齿轮钢具有十分优异的力学性能，实施例1-9的冷锻齿轮钢的屈服强度均在182-218MPa之间、抗拉强度在382-426MPa之间、延伸率≥37％、断面收缩率≥68％。各实施例的冷锻齿 轮钢的各项力学性能十分优异，此钢在低温下具有良好塑性和断面收缩率，具有优良的冷加工特性。
相应地，由表4可知，实施例1-9的冷锻齿轮钢的淬透性满足J1.5：39.4-41.6HRC，J3：36.8-38.6HRC，J5：30.4-32.5HRC，J7：27.4-29.5HRC，J9：22.3-24.7HRC，各位置处的淬透性带宽均≤4HRC。
图1为实施例4的冷锻齿轮钢在光学显微镜下的微观组织照片。
图2为实施例4的冷锻齿轮钢在扫描电子显微镜(SEM)下的图像照片。
结合图1和图2可以看出，本发明中实施例4的冷锻齿轮钢的微观组织为铁素体+球状碳化物。
综上所述可以看出，本发明通过合理的化学成分设计并结合优化工艺，开发出了具有窄的淬透性带宽的冷锻齿轮钢，其不仅具有较好的强度，还具有优良的塑性和延伸率，其可以有效应用于冷锻加工齿轮，适用性十分广泛，具有良好的推广前景和应用价值。
此外，本发明所述冷锻齿轮钢的化学成分和工艺设计合理，其工艺窗口宽松，可以在棒材生产线上实现批量商业化生产。
需要说明，本发明所述的冷锻齿轮钢化学成分和工艺设计合理，工艺窗口宽松，可以在棒材上实现批量商业化生产，具有良好的推广前景和应用价值。
此外，本案中各技术特征的组合方式并不限本案权利要求中所记载的组合方式或是具体实施例中所记载的组合方式，本案记载的所有技术特征可以以任何方式进行自由组合或结合，除非相互之间产生矛盾。
还需要注意，以上列举的仅为本发明的具体实施例，显然本发明不限于以上实施例，随之有着许多的类似变化。本领域的技术人员如果从本发明公开的内容直接导出或联想到的所有变形，均应属于本发明的保护范围。

Claims (10)

  1. 一种冷锻齿轮钢，其特征在于，除Fe和不可避免的杂质以外，所述冷锻齿轮钢还含有以质量百分比计的如下化学元素：
    C：0.15-0.17％、Si：0.10-0.20％、Mn：1.0-1.10％、Cr：0.80-0.90％、Al：0.02-0.04％。
  2. 如权利要求1所述的冷锻齿轮钢，其特征在于，所述冷锻齿轮钢由以质量百分比计的如下化学元素组成：
    C：0.15-0.17％、Si：0.10-0.20％、Mn：1.0-1.10％、Cr：0.80-0.90％、Al：0.02-0.04％；余量为Fe和不可避免的杂质。
  3. 如权利要求1或2所述的冷锻齿轮钢，其特征在于，在不可避免的杂质中，杂质元素的含量满足如下中的至少一种：P≤0.015％，S≤0.003％，N≤0.012％，O≤0.003％、优选O≤0.002％，B≤0.0002％。
  4. 如权利要求1所述的冷锻齿轮钢，其特征在于，所述冷锻齿轮钢还含有如下化学元素中的至少一种：0＜Ca≤0.005％、0＜Ti≤0.008％。
  5. 如权利要求1或2所述的冷锻齿轮钢，其特征在于，所述冷锻齿轮钢的微观组织为铁素体+球状碳化物。
  6. 如权利要求1或2所述的冷锻齿轮钢，其特征在于，所述冷锻齿轮钢的力学性能满足：屈服强度为180-220Mpa，抗拉强度为380-430MPa，延伸率≥37％，断面收缩率≥68％；和/或所述冷锻齿轮钢的淬透性满足：J1.5：38-42 HRC，J3：35-39 HRC，J5：30-34 HRC，J7：26-30 HRC，J9：21-25 HRC，并且以上淬透性带宽均≤4 HRC。
  7. 如权利要求1-6中任一项所述的冷锻齿轮钢的制造方法，其特征在于，所述方法包括以下步骤：
    (1)冶炼和浇铸；
    (2)加热；
    (3)锻造或轧制；
    (4)球化退火：加热至750-770℃并进行保温，然后以5-15℃/h的冷却速度冷却至700-720℃并进行保温，接着以3-12℃/h的冷却速度冷却至660-680℃并进行保温，随后以5-20℃/h的冷却速度冷却至 500℃以下，然后出炉冷却。
  8. 如权利要求7所述的制造方法，其特征在于，在步骤(2)中，控制加热温度为1080-1200℃。
  9. 如权利要求7所述的制造方法，其特征在于，在步骤(3)中，控制终轧或终锻温度为860-980℃。
  10. 如权利要求7所述的制造方法，其特征在于，在步骤(4)中，加热至750-770℃保温4h以上，然后以5-15℃/h的冷却速度冷却至700-720℃保温3.5h以上，接着以3-12℃/h的冷却速度冷却至660-680℃保温3.5h以上，随后以5-20℃/h的冷却速度冷却至500℃以下，然后出炉冷却。
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