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CN-122013046-A - Induction heat treatment high-carbon gear steel

CN122013046ACN 122013046 ACN122013046 ACN 122013046ACN-122013046-A

Abstract

The invention discloses induction heat treatment high-carbon gear steel, and belongs to the technical field of mechanical manufacturing. The gear steel comprises the following chemical components in percentage by mass ：0.705-0.995% C、0.5-2.5% Si、0.1-0.5% Cr、0.010-0.3%Mo、0-0.3% Cu、0-0.2% V、0-0.02% Ti、O < 30 ppm、S < 0.025%、P < 0.025%, and the balance of Fe. The material is subjected to vacuum melting to obtain an ingot, then heated to 1050-1100 ℃ to be fully austenitized and insulated to realize homogenization of alloy components, and then continuously forged to the required size in the cooling process, wherein the final forging temperature is controlled to be 850-900 ℃. The forging is heated and kept at 780-820 ℃ for 1-8 hours, cooled to 600 ℃ at a cooling speed of 20 ℃ per minute and discharged from the furnace, and the structure of the distributed spherical cementite on the ferrite matrix can be obtained, or the pearlite structure is obtained through 850 ℃ heating and normalizing treatment. After induction quenching, the surface hardness of the steel can reach 62-64 HRC, and the depth of a hardening layer is 0.5-5 mm. The surface layer structure is characterized by carbide with average size of 0.3-0.6 μm, martensite with length of 0.5-2 μm and fine grain structure of 7-15 μm.

Inventors

  • LIU YONGNING
  • Xiong Xinyi

Assignees

  • 江苏特斯力新材料科技有限公司

Dates

Publication Date
20260512
Application Date
20260316

Claims (5)

  1. 1. The induction heat treatment high-carbon gear steel and the heat treatment method thereof are characterized in that the gear steel comprises the finished product components of 0.705-0.995% of C, 0.5-2.5% of Si, 0.1-0.5% of Cr and 0.01-0.3% of C by mass percent (wt.%) Mo, 0.01-0.3% Cu, 0-0.2% V, 0-0.02% Ti and the balance Fe.
  2. 2. The induction heat treated high carbon gear steel and heat treatment method thereof according to claim 1, wherein the gear steel is obtained by vacuum melting or conventional industrial special high quality steel process melting to obtain ingot or continuous rolling profile, the oxygen content is less than 30 ppm, and the s and P contents are respectively less than 0.025%.
  3. 3. The induction heat treated high carbon gear steel and heat treatment method thereof according to claim 1 or 2, wherein the heat treatment method comprises the steps of: heating the obtained cast ingot or rolled section to 1050-1100 ℃ for complete austenitizing and preserving heat to homogenize alloy components, then continuously forging the cast ingot or rolled section into a required shape and size in the cooling process, wherein the final forging temperature is 850-900 ℃, heating and preserving heat for 1-8 hours at 780-820 ℃, cooling to 600 ℃ at a cooling speed of 20 ℃ per min, discharging and air cooling to obtain ferrite and spherical cementite tissues, or heating and normalizing at 850 ℃ to obtain pearlitic tissues.
  4. 4. The induction heat treated high carbon gear steel and the heat treatment method thereof according to any one of claims 1 to 3, wherein the depth of the hardened layer can be controlled by adjusting the heating time, current and frequency parameters, the surface hardness after induction quenching can reach 62 to 64 HRC, the depth of the hardened layer is 0.5 to 5mm, and the surface residual compressive stress is 400 to 600 MPa.
  5. 5. The induction heat treated high carbon gear steel as claimed in any one of claims 1 to 4, wherein the hardened structure obtained by the treatment according to the method is characterized by an average grain size of 7 to 15 μm, an average carbide size of 0.3 to 0.6 μm, a martensitic sheet length of 0.5 to 2 μm, a surface hardness after induction hardening of 62 to 65 HRC, and a hardening depth of 0.5 to 5 mm.

Description

Induction heat treatment high-carbon gear steel Technical Field The invention belongs to the technical field of mechanical manufacturing, and particularly relates to low-hardenability high-carbon gear steel suitable for induction heat treatment and a heat treatment method thereof. Background Gears are key mechanical parts for transmitting torque and changing rotating speed, and are widely applied to transmission systems of automobile speed changers, wind driven generators, mechanical equipment reducers and the like. The gear transmits load by sliding contact of the surface, and the surface thereof is subjected to extremely high contact stress, so that the surface is required to have high hardness and high wear resistance. However, the gear root is subjected to a large bending stress, and the core is required to have sufficient toughness. In order to meet the structural performance requirements of the hard core and the toughness of the surface, a carburizing heat treatment process is commonly adopted in the industry. The process ensures that the carbon content of the surface layer reaches a high carbon range of 0.8-1.0%, the core part keeps original low carbon components, after integral quenching, the surface obtains high hardness of HRC60 or more, and the core part obtains low carbon martensite or bainite structure with good toughness, thereby meeting the service performance requirement of the gear. Thus, carburizing heat treatment has become an indispensable key process in gear manufacturing. However, the conventional carburizing heat treatment process consumes a great amount of energy. The parts are typically kept at 900-950 ℃ for 8-10 hours, and for large parts, the treatment time is even as long as tens of hours. The carburizing heat treatment becomes one of the processes with the highest energy consumption in the mechanical industry, and the urgent need for reform the process is always present at home and abroad. Foreign studies have been attempted to increase the carburizing temperature to 1000 ℃ to shorten the carburizing time, thereby achieving the purpose of energy saving. However, the process puts more stringent requirements on carburizing steel, namely the material must have excellent grain growth resistance when heated for a long time at 1000 ℃, otherwise the mechanical properties will be deteriorated. In addition, raw materials such as kerosene, methanol and the like are required to be decomposed in the carburizing process, a large amount of CO is generated, and environmental pollution is caused. The induction heat treatment technology provides a feasible way for replacing the traditional carburizing heat treatment. The induction heat treatment heats the workpiece by using the skin effect of electromagnetic induction, and has the remarkable advantages of high heating speed and high heat efficiency. The heating process starts from the surface and gradually conducts inwards. By precisely controlling parameters such as heating time, current frequency and the like, a thin shell tissue with a hard surface and a tough core similar to carburizing and quenching can be obtained. At present, the induction quenching process is mainly applied to medium carbon steel, for example patent 201410082954.1 'a medium carbon gear heat treatment process', discloses an induction quenching process of 45# steel, which comprises the steps of quenching and tempering, induction quenching and tempering, and the hardness after treatment is 550-600 HV. The hardness of the steel after induction quenching can reach 45-50 HRC, which is obviously lower than the hardness which can be reached by carburizing and quenching. According to the description of the handbook of mechanical engineering materials (5 th edition, 2007), the maximum carbon content of the two low-hardenability induction heat-treated steels 60Ti and 70Ti is 0.7%, and the hardness after induction hardening is still not comparable to the carburized layer hardness. The newly-granted patent 'a low-hardenability high-carbon gear steel and a heat treatment process' (ZL 2017 1 1219013.8) discloses an ultra-high-carbon steel with carbon content in the range of 1.0-1.5%, the hardness and the wear resistance of the ultra-high-carbon gear steel after quenching are obviously improved, and the service life of gears is prolonged. However, too high a carbon content deteriorates the machinability of the material. In order to achieve good balance between service life and processing performance of the gear, the invention provides the induction heat treatment high-carbon gear steel with carbon content controlled in the range of 0.705-0.995%, so as to fill the blank of the existing low-hardenability gear steel in the range. Disclosure of Invention The invention aims to provide induction heat treatment high-carbon gear steel capable of replacing the traditional carburizing heat treatment process and a heat treatment method thereof. The material can obtain high hardness on the surface