Keywords: carbon spring steel wire; tempering
Introduction
In order to reduce the hardness of carbon spring steel wire and make the mechanical properties reach their ideal state, tempering is a necessary process. Oil tempering is a far-reaching development in the history of tempering technology. The purpose of this paper is to discuss the oil tempering of valve carbon spring steel wire (YB/T5102-1993) in detail.
History of Oil Tempering
Oil tempering history can be traced back to two thousand years in China. In ancient China, most of the oil tempering techniques were used to quenching and temper a variety of sacrificial objects. Because of the good thermal properties of animal and vegetable oil, oil tempering has been widely used to temper small objects in Japanese and European swords. With the continuous development of science and technology and the improvement of steel performances, oil tempering plays an increasingly important role in the tempering of steel springs, including carbon spring steel wire YB/T5102-1993.
Oil Tempering Process
At present, the process of oil tempering for valve carbon spring steel wire (YB/T5102-1993) mainly includes overall quenching and low temperature tempering. The overall quenching process is carried out in three steps: preheating, quenching and start tempering. It can be seen from the quenching diagram of YB/T5102-1993 that the preheating temperature is 800-900℃ and the quenching temperature is 950-1000℃. The steel spring here passes through its transformation range, achieves comprehensive quenching effect and obtains certain wear resistance.
After this overall heat treatment, the steel spring enters the tempering process. Its purpose is to reduce the brittleness of the material, improve the fatigue strength and wear resistance while maintaining the hardness. The tempering temperature of oil tempering should be selected as low as possible, generally ranging from 300 to 450 °C. The tempering time should not be too long, generally it is no more than four hours or little more. After tempering, the breaking strength of the steel spring can compete with that of hot-rolled spring steel wire YB/T5102-1993, and the bending riglity is better than that of hot-rolled spring steel wire.
Advantages and Disadvantages of Oil Tempering
Oil tempering has the advantages of small volume and convenient heat treatment without setting up a cooling pond. In addition, the tempering of oil tempering is more uniform, the deformation is less, and the hazard caused by high temperature and high pressure is avoided. In terms of disadvantages, oil tempering has a large energy consumption, a high oil consumption rate, a large amount of foam in the oil and a small cooling rate of the oil surface.
Conclusion
In summary, oil tempering is a good choice for tempering valve carbon spring steel wire (YB/T5102-1993). Oil tempering has many advantages, such as small volume, convenient heat treatment and uniform tempering. In addition, it also has certain disadvantages, such as high energy consumption, large oil consumption rate, etc. In order to make the tempering effect of the valve carbon spring steel wire (YB/T5102-1993) better, the process design should be reasonable and the parameters should be regulated properly.
