Isothermal quenching heat treatment process method for third-generation bearing steel
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A technology of isothermal quenching and process method, which is applied in the field of bearing steel, can solve the problems of poor comprehensive mechanical properties, poor structure uniformity, and large environmental impact, and achieve the effects of improving plasticity, toughness, uniform structure, and good red hardness
Active Publication Date: 2021-03-16
BEIHANG UNIV +1
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Problems solved by technology
This third-generation bearing steel processed by the austempering process of the prior art has the problems of easy cracking, high brittleness, and poor ductility and toughness during quenching.
and if figure 1 Shown is the photo of the metallographic structure of the CSS-42L bearing steel block treated by the existing austempering process. From left to right, it is the electron micrograph of the structure at different depths from the inside to the outside; from the figure, it can be seen that the structure from the center to the surface The transformation of pearlite → bainite → martensite will occur on the surface, and the uniformity of the structure is not good, resulting in poor comprehensive mechanical properties; in addition, the medium used for salt bath quenching of this third-generation bearing steel is generally mixed Nitrate, which produces toxic gas during the quenching process, has a great impact on the environment and causes a great waste of resources
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Embodiment 1
[0060] Embodiment 1: What this embodiment uses is the first kind of bearing steel block, and it carries out the following processing steps:
[0061] (7a.1) Solution treatment:
[0062] At 10°C / min, heat to the first stage temperature of 550°C, and keep warm for 15 minutes;
[0063] At 10°C / min, heat to the second stage temperature of 850°C and hold for 15 minutes;
[0064] Heat at 5°C / min to a solid solution temperature of 1090°C, and a solid solution time of 45 minutes;
[0065] (7a.2) Austempering: put it into the tube furnace quickly, and cool down rapidly by means of segmental circulation cooling;
[0066] (7a.2.1) High pressure and high flow rate gas quenching: pressure P 1 =1.5MPa; Velocity V 1 =0.5m / s, carry out purging, and the purging time is t 1 = 60s;
[0067] (7a.2.2) Gas quenching at low pressure and low flow rate: pressure P 2 =0.3MPa; Velocity V 2 =0.2m / s,t 2 = 60s;
[0068] (7a.2.3) Cycle step (7a.2.1) and step (7a.2.2) 7 times until cooled to isother...
Embodiment 2
[0071] Embodiment 2: The difference between this embodiment and Embodiment 1 is that the isothermal temperature of step (7a.2.3) is 180°C.
[0072] The metallographic structure photograph of present embodiment is as Figure 4 As shown, the tissue is uniform.
Embodiment 3
[0073] Embodiment 3: The difference between this embodiment and Embodiment 1 is that the isothermal temperature of step (7a.2.3) is 220°C.
[0074] The metallographic structure photograph of present embodiment is as Figure 5 As shown, the tissue is uniform.
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Abstract
The invention relates to an isothermal quenching heat treatment process method for third-generation bearing steel. The isothermal quenching heat treatment process method comprises the following stepsthat A, solution treatment is carried out; B, isothermal quenching is conducted, specifically, when the thickness h of a steel block is smaller than or equal to 20 mm, constant-pressure and constant-flow-speed gas quenching is adopted, specifically, the pressure is 0.2-1.5 MPa, the flow speed is 0.1-0.8m/s, the cooling time is smaller than or equal to 15 min, the cooling speed is 60-100 DEG C/min,and heat preservation is conducted for 1-2 h after the steel block is cooled to the isothermal temperature of 140-280 DEG C; then air cooling is carried out to room temperature; and when the thickness h of the steel block is larger than 20 mm and smaller than or equal to 50 mm, high-pressure high-flow-speed gas quenching and low-pressure low-flow-speed gas quenching are adopted for segmented circulating cooling. By adopting the isothermal quenching heat treatment process, the plasticity and toughness of the third-generation bearing steel can be improved, so that the structure components are uniform and environment-friendly.
Description
technical field [0001] The invention relates to the field of bearing steel, in particular to an austempering heat treatment method for third-generation bearing steel. Background technique [0002] For the third-generation bearing steel with low C and high Cr-Co-Mo, including CSS-42L, etc., compared with the second-generation bearing steel M50 and M50NiL, an appropriate amount of Cr element is added to improve its corrosion resistance. High amount of Co element to refine M 2 Phase X. After carburizing, the alloy not only has excellent red hardness, wear resistance, fatigue resistance and corrosion resistance on the surface, but also maintains high strength and fracture toughness in the core. [0003] In 1954, foreign countries began to study bainite austempering of GCr15 steel. FAG and other world-renowned bearing companies have applied austempering technology to impact-resistant and poorly lubricated bearings such as railways, automobiles, rolling mills, and drilling tools...
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