Heat treatment method of 20CrH carburized gear steel for automobile

Abstract

The invention discloses a heat treatment method of carburized gear steel for an automobile, a heat treatment sample is 20CrH carburized gear steel for the automobile, and the heat treatment method comprises the following steps: (1) primary quenching: putting a rough-machined carburized gear steel blank sample for the automobile into a heating furnace, heating to 890-910 DEG C, preserving heat for 60 minutes, then carrying out primary quenching, and cooling in water; and (2) the blank sample subjected to primary quenching is put into a heating furnace, the temperature is increased to 780-800 DEG C, heat preservation is conducted for 50 min, then secondary quenching is conducted, and cooling is conducted in water. A sample subjected to heat treatment is subjected to mechanical property inspection, and it is found that the steel has the advantages of being good in cleanliness, small in grain size, narrow in hardenability bandwidth and the like.

Description

Technical Field

[0001] This invention belongs to the field of manufacturing carburized gear steel for automobiles, and in particular relates to a heat treatment method for 20CrH carburized gear steel for automobiles. Background Technology

[0002] Automotive transmission systems operate in harsh environments, frequently subjected to high temperatures, high pressures, and corrosive media. Carburized gear steel for automobiles needs excellent wear resistance and corrosion resistance, maintaining surface smoothness and mechanical properties for extended periods to prolong gear lifespan. Using high-performance carburized gear steel can reduce automotive manufacturing and maintenance costs, improving overall vehicle performance and economy. Simultaneously, extending gear lifespan reduces replacement and repair frequency, saving costs for both automakers and users. Therefore, developing appropriate heat treatment methods to ensure the good performance of carburized gear steel for automobiles is crucial. Research on the phase transformation points of 20CrH carburized gear steel for automobiles reveals that the optimal first quenching heat treatment temperature is controlled between 890℃ and 910℃, and the optimal second quenching temperature is between 780℃ and 800℃. Using water with a high cooling rate as the quenching medium yields good cleanliness, fine grains, and a narrow hardenability band. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention aims to provide a heat treatment method for 20CrH carburized gear steel for automobiles, thereby enabling it to possess excellent comprehensive performance and significantly improving the overall lifespan and safety of the carburized gear steel for automobiles.

[0004] The specific technical solution of the present invention is as follows:

[0005] This invention provides a heat treatment method for 20CrH carburized gear steel for automobiles, which includes the following steps:

[0006] (1) Place the rough-machined carburized gear steel blank sample for automobiles into a heating furnace, heat it to 890℃~910℃, hold it for 60 min, then perform the first quenching, and cool it in water; and

[0007] (2) Place the blank sample after the first quenching into the heating furnace, heat it to 780℃~800℃, keep it at that temperature for 50 min, and then perform the second quenching and cool it in water.

[0008] In some embodiments, the heat treatment method includes the following steps:

[0009] (1) Place the rough-machined carburized gear steel blank sample for automobiles into a heating furnace, heat it to 890℃, hold it for 60 minutes, then perform the first quenching, and cool it in water; and

[0010] (2) Place the blank sample after the first quenching into the heating furnace, heat it to 780℃, keep it at that temperature for 50 minutes, and then perform the second quenching and cool it in water.

[0011] In some embodiments, the heat treatment method includes the following steps:

[0012] (1) Place the rough-machined carburized gear steel blank sample for automobiles into a heating furnace, heat it to 900℃, hold it for 60 minutes, then perform the first quenching, and cool it in water; and

[0013] (2) Place the blank sample after the first quenching into the heating furnace, heat it to 790℃, keep it at that temperature for 50 minutes, and then perform the second quenching and cool it in water.

[0014] In some embodiments, the heat treatment method includes the following steps:

[0015] (1) Place the rough-machined carburized gear steel blank sample for automobiles into a heating furnace, heat it to 910℃, hold it for 60 minutes, then perform the first quenching, and cool it in water; and

[0016] (2) Place the blank sample after the first quenching into the heating furnace, heat it to 800℃, keep it at that temperature for 50 minutes, and then perform the second quenching and cool it in water.

[0017] In some embodiments, the chemical composition of the 20CrH carburized gear steel for automobiles, by mass percentage, is: C 0.15-0.25%, Si 0.25-0.30%, Mn 0.75-0.80%, P≤0.020%, S≤0.005%, Cr 0.75-0.90%, with the remainder being Fe and unavoidable impurities.

[0018] In some embodiments, the chemical composition of the 20CrH carburized gear steel for automobiles, by mass percentage, is: C 0.19-0.21%, Si 0.25-0.28%, Mn 0.76-0.79%, P≤0.020%, S≤0.005%, Cr 0.79-0.87%, with the remainder being Fe and unavoidable impurities.

[0019] The beneficial effects of the present invention are: the heat treatment method for carburized gear steel for automobiles of the present invention, by studying the effects of heat treatment heating regime, including quenching temperature, tempering temperature and holding time, on microstructure and properties, has determined a set of heat treatment regimes that can guarantee the stable properties of steel. Detailed Implementation

[0020] The heat treatment method for carburized gear steel for automobiles according to the present invention will be described in further detail below.

[0021] The steel part described in the heat treatment method of this invention is 20CrH carburized gear steel for automobiles, and the process is carried out according to the following steps:

[0022] (1) First quenching: The rough-machined carburized gear steel blank sample for automobiles is placed in a heating furnace, heated to 890℃~910℃, held for 60 minutes, and then quenched and cooled in water.

[0023] (2) Second quenching: The steel blank sample after the first quenching is placed in a heating furnace, heated to 780℃~800℃, held for 50 minutes, and then quenched and cooled in water.

[0024] The heat treatment method for carburized gear steel for automobiles of the present invention, by studying the effects of heat treatment heating regime, including quenching temperature and holding time, on microstructure and properties, determines a heat treatment regime that can guarantee the stable properties of the steel; while ensuring the microstructure and properties after heat treatment, the heating temperature range is narrowed, the holding time is reduced, the energy consumption of heat treatment is reduced, and the efficiency of heat treatment is improved.

[0025] The present invention will be described in detail below through specific embodiments. These embodiments are intended to help understand the present invention and are not intended to limit the scope of the present invention.

[0026] Example 1:

[0027] The steel used in the heat treatment method of this invention is 20CrH carburized gear steel for automobiles, and its chemical composition and content are shown in Table 1 below. The process is carried out according to the following steps:

[0028] (1) First quenching: The rough-machined carburized gear steel blank sample for automobiles is placed in a heating furnace, heated to 890℃, held for 60 minutes, and then quenched and cooled in water.

[0029] (2) Second quenching: The steel blank sample after the first quenching is placed in a heating furnace, heated to 780℃, held for 50 minutes, and then quenched and cooled in water.

[0030] Example 2:

[0031] The steel used in the heat treatment method of this invention is 20CrH carburized gear steel for automobiles, and its chemical composition and content are shown in Table 1 below. The process is carried out according to the following steps:

[0032] (1) First quenching: The rough-machined carburized gear steel blank sample for automobiles is placed in a heating furnace, heated to 900℃, held for 60 minutes, and then quenched and cooled in water.

[0033] (2) Second quenching: The steel blank sample after the first quenching is placed in a heating furnace, heated to 790℃, held for 50 minutes, and then quenched and cooled in water.

[0034] Example 3:

[0035] The steel used in the heat treatment method of this invention is 20CrH carburized gear steel for automobiles, and its chemical composition and content are shown in Table 1 below. The process is carried out according to the following steps:

[0036] (1) First quenching: The rough-machined carburized gear steel blank sample for automobiles is placed in a heating furnace, heated to 910℃, held for 60 minutes, and then quenched and cooled in water.

[0037] (2) Second quenching: The steel blank sample after the first quenching is placed in a heating furnace, heated to 800℃, held for 50 minutes, and then quenched and cooled in water.

[0038] After heat treatment, the rough-machined blanks of each embodiment were precision-machined and subjected to various performance tests. The test results are shown in Tables 2 and 3. As can be seen from Tables 2 and 3, all performance indicators are higher than the requirements, and the performance of the heat-treated samples is qualified.

[0039] Table 1: Chemical composition (mass percentage) of various examples of carburized gear steel for automobiles

[0040]

[0041] Table 2: Non-metallic inclusions and austenite grain size in various examples of carburized gear steel for automobiles

[0042]

[0043] Table 3: End Hardness Values ​​of Carburized Gear Steel for Automobiles

[0044]

[0045] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A heat treatment method for 20CrH carburized gear steel for automobiles, characterized in that, The heat treatment method includes the following steps: (1) Place the rough-machined carburized gear steel blank sample for automobiles into a heating furnace, heat it to 890℃~910℃, hold it for 60 min, then perform the first quenching, and cool it in water; and (2) Place the blank sample after the first quenching into the heating furnace, heat it to 780℃~800℃, keep it at that temperature for 50 min, and then perform the second quenching and cool it in water.

2. The heat treatment method as described in claim 1, characterized in that, The heat treatment method includes the following steps: (1) Place the rough-machined carburized gear steel blank sample for automobiles into a heating furnace, heat it to 890℃, hold it for 60 minutes, then perform the first quenching, and cool it in water; and (2) Place the blank sample after the first quenching into the heating furnace, heat it to 780℃, keep it at that temperature for 50 minutes, and then perform the second quenching and cool it in water.

3. The heat treatment method as described in claim 1, characterized in that, The heat treatment method includes the following steps: (1) Place the rough-machined carburized gear steel blank sample for automobiles into a heating furnace, heat it to 900℃, hold it for 60 minutes, then perform the first quenching, and cool it in water; and (2) Place the blank sample after the first quenching into the heating furnace, heat it to 790℃, keep it at that temperature for 50 minutes, and then perform the second quenching and cool it in water.

4. The heat treatment method as described in claim 1, characterized in that, The heat treatment method includes the following steps: (1) Place the rough-machined carburized gear steel blank sample for automobiles into a heating furnace, heat it to 910℃, hold it for 60 minutes, then perform the first quenching, and cool it in water; and (2) Place the blank sample after the first quenching into the heating furnace, heat it to 800℃, keep it at that temperature for 50 minutes, and then perform the second quenching and cool it in water.

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