Gear shaft heat treatment
The mill is an important piece of machinery for modern industrial production, and the gear shaft of the mill is an important transmission part of the mill, mainly subjected to alternating load, impact load, shear stress and high contact stress. The shaft is easy to produce cracks, and the teeth are easy to wear. Therefore, the heart of the gear shaft requires a certain degree of strength and toughness, a high fatigue limit and resistance to multiple impacts. The surface should also have a certain degree of hardness and wear resistance. In order to meet these performance requirements, the material should have good mechanical properties, often using 42CrMo steel by normalizing, tempering, induction heating quenching and low-temperature tempering has reached the required performance.Gear shaft heat treatment
Gear shaft heat treatment；42CrMo is a medium carbon alloy steel, the preparatory heat treatment is normalized, the main purpose is to obtain a certain hardness, to facilitate the cutting of billets, for tempering to prepare the organization. The purpose of tempering is to improve the overall mechanical properties of the mill gear shaft. Medium frequency induction heating surface quenching is to make the surface of the parts to get high hardness and wear resistance, while the heart still maintains a certain strength and high plasticity and toughness.
Gear shaft heat treatment；Through the analysis of 42CrMo steel heat treatment process, clear in the implementation of the heat treatment process needs to pay attention to the issues. To be able to correctly determine the heating temperature, time, holding time, cooling mode, the purpose is to achieve the required performance and ensure quality through the correct heat treatment process.
According to the working conditions, failure form and performance requirements of the gear shaft, most of the materials are selected as alloy medium carbon steel. In designing the normalizing – tempering – medium frequency induction heating quenching plus low temperature tempering heat treatment process, this design draws on the “Heat Treatment Engineer’s Handbook”, “Heat Treatment Practical Data Quick Reference Manual”, “Heat Treatment of Steel”, “Steel for Machine Tool Parts”, “Metal Technology”, etc. According to the theoretical basis of the process design, a complete heat treatment process is set, so that the surface of the heat-treated 42CrMo medium carbon alloy structural steel has high hardness, high wear resistance, high fatigue strength, strength at high temperatures, and also high strength and toughness of the heart, so as to meet the quality requirements of the gear shaft.Gear shaft heat treatment
Gear shaft heat treatment
(1) gear material metallurgical factors on the impact of deformation
Tests show that the higher the hardenability of steel. The greater the deformation. When the hardness of the heart is higher than 40HRC, the deformation will increase significantly. Therefore, the hardenability of the steel with certain requirements, the narrower the hardenability band. A1/N content ratio control in the range of 1 to 2.5, can make the hardenability zone narrower, reduce deformation. In addition, the material box segregation and band organization affects the gear spline hole uneven deformation and uneven carburization.
(2) The effect of preparatory heat treatment on gear deformation
Normalization hardness is too high, mixed crystal, a large number of Soxhlet or Weiss organization will make the bore deformation increases, so to use temperature-controlled normalization or isothermal annealing to deal with forgings.Gear shaft heat treatment
(3) The influence of carburizing process on deformation
Uniformity of temperature. The uniformity of the carbon layer, the uniformity of the cooling medium temperature affects the gear deformation, while the higher the carburizing temperature, the thicker the carburizing layer. The oil temperature is low and the gear deformation is large. So to improve the equipment, optimize the process, improve the quality of gear heat treatment.
(4) the impact of quenching on deformation
Quenching cooling behavior is the most important factor affecting the gear deformation, hot oil quenching than cold oil quenching deformation is small, generally controlled at 100 ℃ ± 120 ℃. The cooling capacity of the oil is also critical to the deformation. Stirring mode and intensity are affecting the deformation, on the quenching press quenching disk gear, according to the deformation of various gears. Adjust the parameters of the quenching press to reduce deformation, adjust the pressure of the inner and outer pressure die and expansion block and the size of each section of the oil spray and the upper work table to control the deformation.