slewing bearing factory

What processes are included in the heat treatment of slewing bearings?

The function of the heat treatment of the slewing bearing is to improve the mechanical properties of the material, eliminate the residual stress and improve the machining performance of the metal. Different heat treatments are adopted at different stages in the processing of the slewing bearing. Commonly used are annealing, normalizing, aging, modulation, Quenching, nitriding, etc., let’s briefly introduce each heat treatment process.

1. Annealing
The process of heating the forging of the slewing bearing to a certain temperature and keeping it for a long time and then slowly cooling it, the main purpose is to release the residual stress during forging, increase the toughness of the forging, reduce the hardness of the forging to facilitate subsequent processing, and improve the internal structure of the forging. Refine grains and enhance the mechanical properties of forgings.

 

2. Normalizing
The slewing bearing forgings are heated to a temperature of 30~50°C exceeding the AC3 temperature, and they are cooled after a period of heat preservation. After they are released, they need to be cooled quickly. Generally, water spray, spray or air cooling are used.

Because they do not need to be cooled with the furnace, and accelerated cooling is adopted. Measures, the heat treatment efficiency is higher, the grains of the forgings after normalizing are more refined and the distribution is more uniform, which can improve the comprehensive mechanical properties of the forgings, improve the cutting performance of the forgings, and make the forgings easier to process.

3. Aging
The process of placing the machined slewing bearing ferrule at a higher temperature or room temperature for a period of time to release the internal stress and fully deform the ferrule. The aging at a certain higher temperature is called artificial aging, and the aging in the natural state is called natural aging. Artificial aging generally heats the ferrule to about 150 ℃ and keeps it for about 12 hours, which can eliminate the internal stress of the ferrule and make the ferrule more stable. effect.

Generally, aging treatment is carried out after rough machining and heat treatment of the slewing bearing ring. For precision slewing bearings, almost every process is processed, an aging treatment will be carried out. On the one hand, it can ensure high machining accuracy and prevent machining deformation. In terms of fully eliminating the internal stress of the slewing bearing to ensure that the slewing bearing will not be deformed after delivery, affecting the accuracy.

4. Modulation
The rough processed slewing bearing forgings are first quenched and then subjected to a heat treatment process of high temperature tempering. The quenching temperature and tempering temperature are determined according to the size of the ferrule and the specific hardness and mechanical properties. Generally, the ferrule is heated to 850 °C for a period of time, and then quenched. The quenching medium is generally oil or water medium.

After quenching High temperature tempering, the ferrule is heated to 630 ℃ for a period of time and then air-cooled. The slewing ring has excellent comprehensive mechanical properties after modulation, and the strength and toughness are well matched, with high strength, excellent toughness, plasticity, cutting performance, etc.

5. Quenching
Quickly heat the surface of the channel or tooth of the slewing bearing to the quenching temperature, and then immediately use the quenching liquid to cool the heating part. After cooling, the surface of the channel and tooth is hard, the core is soft, and the surface is wear-resistant and anti-fatigue.

High toughness, good impact resistance. Quenching not only makes the channels and teeth of the slewing bearing firm and wear-resistant, but also increases the load of the channels and teeth, and improves the comprehensive performance of the slewing bearing.

6. Nitriding

Nitriding is a method of infiltrating nitrogen atoms into the metal surface to obtain a layer of nitrogen-containing compounds. Nitriding layer can improve the hardness, wear resistance, fatigue strength and corrosion resistance of the part surface. Because the nitriding temperature is low, the deformation is small, and the nitriding layer is thin (generally no more than 0.6~0.7mm), the nitriding process should be arranged as far back as possible. In order to reduce the deformation during nitriding, it is generally necessary to High temperature tempering for stress relief.