Quenching and tempering treatment of the hottest 3

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Quenching and tempering treatment of 35CrMo steel large supporting axle

the supporting axle is one of the important parts of the supporting part of the dry process rotary cement kiln. Its material is 35Cr mo. due to the lack of quenching oil, our factory cannot carry out oil quenching on it. In order to meet the needs of production, we adopted the cooling process of "water → air → water" and the method of controlling the "final cooling temperature", which solved the quenching and tempering of large-scale alloy steel supporting axle with excellent chemical corrosion resistance, and its mechanical properties are better than those after oil quenching and tempering

1. The structure, material and performance requirements of the supporting axle

the structure of the supporting axle is shown in Figure 1

2. Quenching and tempering treatment process

(1) the requirements of rough machining are to ensure the processing after quenching and tempering. During rough machining, 8 ~ 9mm allowance is left for each processing part, and the surface roughness is RA6 three μ M above, so as to facilitate flaw detection; 250 mm shaft head is reserved at the other end as the allowance for mechanical properties

(2) the quenching and tempering process curve is shown in Figure 2

(3) the only difference between the process analysis and the traditional 35Cr Mo shaft quenching and tempering process is the use of water quenching and cooling. As we all know, quenching and cooling will produce both structural stress and thermal stress. Using oil quenching, because its cooling speed is much smaller than that of water quenching, and the thermal stress is much smaller, the supporting axle is not easy to crack during oil quenching; Because of water quenching, the thermal stress produced by the anti digital display impact testing machine is very large, which is very easy to cause the cracking of the supporting axle. Therefore, it is necessary to adopt water quenching, reduce thermal stress and prevent the cracking of the supporting axle, which is the key to the formulation of the process, which is specifically reflected in the determination of cooling parameters. In order to reduce thermal stress, our practice is to adopt "water → air → water" gap cooling; The temperature of the workpiece during final cooling is 500 ~ 550 ℃, so that the workpiece can use its own waste heat for self tempering to reduce stress

3. Process effect

we commissioned an oil quenched supporting axle, and took physical samples with the supporting axle adopting the "water → air → water" cooling process, and made mechanical properties. Its quantity is continuous. Ford used the rice by-product rice husk fiber reinforced plastic energy test in 2014 f ⑴ 50 automobile. It can be seen that the supporting axle with water quenching and tempering meets the performance requirements of the drawing and is better than that with oil quenching and tempering

4. Conclusion

(1) the method of "water → air → water" cooling process can effectively reduce quenching stress

(2) controlling the final cooling temperature is the key to prevent the cracking of the supporting axle

(3) the mechanical properties of quenching are better than oil quenching. (end)

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