Low-cost high-purity medium carbon bearing steel for automobile hub and manufacturing method thereof

Abstract

The invention discloses a manufacturing method of low-cost and high-purity medium-carbon bearing steel used for automobile hubs; the manufacturing method comprises the following steps: (a) the mass percentage of the components of the bearing steel is as follows: C: 0.55 percent to 0.58 percent, Si: 0.15 percent to 0.35 percent, Mn: 0.80 percent to 0.85 percent, P: less than or equal to 0.030 percent, S: less than or equal to 0.015 percent, Cr: 0.10 percent to 0.20 percent, Ni: less than or equal to 0.25 percent, Cu: less than or equal to 0.20 percent, Mo: less than or equal to 0.08 percent, Al: 0.008 percent to 0.015 percent, Ti: less than or equal to 30ppm, O: less than or equal to 15ppm, and the rest are Fe and inevitable impurities; (b) smelting, electric furnace initial melting+ ladle furnace refined melting+ vacuum degassing; (c) continuous casting into steel billet; (d) rolling. Compared with the prior art, the technological process has obviously shorter process and lower production cost; the impact resistance, torsion resistance, wear resistance and fatigue endurance of the produced automobile hub bearing are good.

Description

technical field [0001] The invention relates to steel for automobiles and a production method thereof, in particular to a medium-carbon bearing steel for automobile wheel hubs. Background technique [0002] Automobile hub bearing is one of the important parts of automobile chassis system, and its quality is directly related to the safety, stability and reliability of the automobile. The traditional car wheel hub bearing structure is two sets of bearings, which requires auto assembly workers to choose and match the clearance and fill the grease, which often causes problems such as inaccurate clearance adjustment and easy contamination of the grease. The first generation hub bearing unit designed two sets of bearings into a set of bearings, adjusted the clearance, installed grease, and reduced processing and assembly costs. Both traditional automobile hub bearings and first-generation hub bearing units are produced with high-carbon chromium bearing steel. The second-generati...

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Problems solved by technology

[0007] As automobile manufacturers have higher and higher requirements for wheel hub materials, the S55C steel composition provided in Table 1 has the following problems: 1. The lower limit composition of C and Mn is too low. When the C and Mn compositions of the steel are at the lower limit, the high The hardness after frequency quenching cannot meet the parts requirements of HV700~800, resulting in low hardness on the raceway surface after high frequency quenching, which affects its wear resistance

2. The upper limit of S content is too high, resulting in high sulfide content and affecting its fatigue life

3. The content of O and Al in the form of oxides is not controlled, resulting in a high content of inclusions in the steel, which reduces the fatigue life

[0011] 2. The Ti content is not controlled. If the Ti content is too high, large particles of TiN or TiCN will be produced. This diamond-shaped hard inclusion is very harmful to the fatigue life of the hub bearing

Firstly, in order to satisfy the central porosity level C≤2, the shrinkage cavity level of the continuous casting slab must be reduced, and the continuous casting bloom has a large compression ratio, and the central porosity is not easy to exceed the standard; secondly, it is necessary to solve the aluminum-killed steel continuous casting steel pouring (nozzle can not be blocked) ) and cannot add calcium (the aluminum-containing inclusions will be denatured after adding calcium, and it is not easy to block the nozzle, but the calcium-containing inclusions are very harmful to the fatigue life of the bearing), and the pouring nozzle of the continuous casting bloom is large, resulting in blockage less likely

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