1、 Analysis of raw materials of slewing ring
Slewing ring is mainly composed of inner ring and outer ring. The materials of conventional inner and outer rings are 50Mn and 42CrMo. 50Mn is carbon structural steel and 42CrMo is alloy structural steel. 50Mn has high strength, elasticity and hardness. 42CrMo steel is an ultra-high strength steel with high strength and toughness and good hardenability. If there are performance requirements, both steels need heat treatment. However, 50Mn has the tendency of overheating sensitivity and temper brittleness, so it is more necessary to pay attention to the control of temperature during heat treatment.
After years of experience summary and improvement, Xuzhou helin slewing ring has continuously improved its process. For raw materials of different materials, different currents and quenchant concentrations are used, and the process is also slightly adjusted for different batches of the same materials. Its own quenching quality acceptance standard is higher than the industry standard, extending the service life of the slewing ring.
2、 Application scope of slewing ring raw materials
There are normalizing and quenching and tempering treatment methods for the inner and outer ring blank of slewing ring: normalizing is a heat treatment method that heats the steel above the critical temperature to convert all the steel into uniform austenite, and then cools naturally in the air. It can eliminate the network cementite of hypereutectoid steel. For hypoeutectoid steel, normalizing can refine the lattice and improve the comprehensive mechanical properties. It is economical to use normalizing instead of annealing process for parts with low requirements; Quenching and tempering treatment is a heat treatment method of high temperature tempering after quenching. High temperature tempering refers to tempering between 500-650 ℃. Quenching and tempering can greatly adjust the properties and materials of steel, with good strength, plasticity and toughness, and good comprehensive mechanical properties.
After quenching and tempering treatment, 50Mn and 42CrMo can be applied to most working conditions of slewing bearings. Generally, 50Mn is used for domestic conventional parts, and 42CrMo is used for foreign or domestic working conditions with high requirements. 42CrMo has better mechanical properties and toughness than 50Mn. In some special occasions, such as corrosive environment or medical food, stainless steel raw materials will be used to produce slewing ring.
3、 Raw material advantages of Xuzhou Helin slewing ring
The cost of normalized blank is low, the matrix hardness is within 200hb, and the subsequent processing cost is also relatively low. However, the bearing and gear circumferential force after processing into rotary bearing are less than those of quenched and tempered products. Xuzhou Helin slewing bearing, after careful consideration, does not use normalized raw materials to produce slewing ring in order to eliminate production errors, For the requirements of some special working conditions, high hardness billets are used, and the quenching and tempering hardness is 270-320hb, which meets the requirements of customers and the market.