Rolling mill bearing is the bearing used on the roll neck and drum of metallurgical, mining and other rolling mill stands. The following is a detailed explanation of 11 heat treatment processes for rolling mill bearing processing, hoping to help you.

1. Reduce heating temperature

Generally, the quenching heating temperature of hypoeutectoid carbon steel is 30 ~ 50 ℃ above AC3, and the quenching heating temperature of eutectoid and hypereutectoid carbon steel is 30 ~ 50 ℃ above AC1. However, recent studies have confirmed that the temperature of hypoeutectoid steel is slightly lower than that of AC3 α＋γ Heat quenching in two-phase zone (i.e. sub temperature quenching) can improve the strength and toughness of steel, reduce the brittle transition temperature and eliminate tempering brittleness. The heating temperature of quenching can be reduced by 40 ℃.

Low temperature rapid short-time heating quenching of high carbon steel can reduce the carbon content of austenite and obtain lath martensite with good strength toughness fit. It can not only improve its toughness, but also shorten the heating time.

For some transmission gears, carbonitriding is used instead of carburizing, the wear resistance is increased by 40% ~ 60%, the fatigue strength is increased by 50% ~ 80%, and the carburizing time is the same, but the carburizing temperature (850 ℃) is 70 ℃ lower than the carburizing temperature (920 ℃), and the heat treatment deformation can be reduced.

2. Shorten heating time

The production practice shows that the traditional heating time determined according to the effective thickness of the workpiece is conservative, so the formula of heating and holding time should be adjusted τ＝α· Heating coefficient in K · D α Make corrections. According to the traditional treatment process parameters, when heated to 800 ~ 900 ℃ in an air furnace, α The recommended value is 1.0 ~ 1.8min/mm, which is obviously conservative. If you can α If the value decreases, the heating time can be greatly shortened. The heating time shall be determined through experiments according to the steel type, workpiece size, furnace loading, etc. once the optimized process parameters are determined, they shall be carefully implemented in order to obtain significant economic benefits.

3. Cancel tempering or reduce tempering times

Cancel the tempering of carburized steel. For example, the fatigue limit of double-sided carburized piston pin for 20Cr steel loader can be increased by 16% compared with that of tempering; The tempering of low-carbon martensitic steel is cancelled, the bulldozer pin sleeve is simplified to 20 steel quenched (low-carbon martensite), the hardness is stable at about 45hrc, the product strength and wear resistance are significantly improved, and the quality is stable; The tempering times of high-speed steel shall be reduced. For example, the saw blade of W18Cr4V Steel shall be tempered once (560 ℃) × 1H) instead of the traditional 560 ℃ × After tempering for three times in 1H, the service life is increased by 40%.

4. Replace high temperature tempering with low and medium temperature tempering

Medium carbon or medium carbon alloy structural steel can obtain higher multi impact resistance by using medium and low temperature tempering instead of high temperature tempering. W6Mo5Cr4V2 steel Φ 8mm drill bit, 350 ℃ after quenching × 1h＋560℃ × 1H secondary tempering, 560 ℃ × The cutting life of the drill bit tempered three times in 1H is increased by 40.

5. Reasonably reduce the depth of infiltration layer

Chemical heat treatment has long cycle and high power consumption. If the infiltration depth can be reduced to shorten the time, it is an important means of energy saving. The necessary hardened layer depth is obtained by stress measurement, which shows that the current hardened layer is too deep, and only 70% of the traditional hardened layer depth is enough. The results show that carbonitriding can reduce the layer depth by 30% ~ 40% compared with carburizing. At the same time, if the infiltration depth is controlled at the lower limit of its technical requirements in actual production, it can also save energy by 20%, shorten the time and reduce the deformation.

6. High temperature and vacuum chemical heat treatment

High temperature chemical heat treatment is to increase the chemical heat treatment temperature when the equipment service temperature is allowed and the austenite grain of the infiltrated steel is not growing, so as to greatly accelerate the speed of carburization. Increasing t

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