The main factors affecting the heat treatment hardness of the ZLY224-25 gear reducer are as follows:
Material Factors
Carbon content : Carbon content is the main factor that determines the hardness of steel. The higher the carbon content, the higher the hardness of steel, and the higher the hardness after quenching. The carbon content of steel from different manufacturers and batches may vary, which will affect the hardness after heat treatment.
Alloy elements : Almost all alloy elements can improve the strength and hardness of steel to varying degrees, such as Si, Mn, Ni and other elements have significant strengthening effects; Ti, Mo, Cr, Mn, W, V and other elements can combine with carbon to form carbides. When distributed uniformly, the hardness and wear resistance of steel can be significantly improved.
Tissue grains : The raw material structure is severely uneven and some grains are too coarse, which will directly affect the uniformity of hardness after quenching or the hardenability of the material, resulting in uneven hardness.
Decarburizing layer : If there is a decarburizing layer, oxide scale or rust spot on the surface of raw materials and forgings, the surface hardness will occur after quenching, especially forgings are prone to decarburizing.
Heat treatment process factors
Quenching temperature and insulation time : The low quenching heating temperature or short insulation time will cause uneven heating of parts, uneven austenite composition, insufficient dissolution of carbides, resulting in uneven surface hardness or insufficient hardness.
Quenching cooling medium and cooling methods : Inappropriate selection of quenching cooling medium or excessive temperature of cooling medium, the speed of the parts does not exceed the critical cooling speed during quenching and cooling, and insufficient cooling will lead to insufficient hardness or uneven hardness. In addition, the parts move unstablely in the cooling medium, accumulate, or there are impurities in the cooling medium, etc., which will also affect the hardness.
Temperature and time : If the tempering temperature is higher than normal requirements, it will cause martensite to decompose and reduce hardness; if the tempering temperature is lower than normal requirements, and the quenched martensite is not completely converted into tempered structure, it will cause extremely high hardness. If the tempering time is too short, the residual martensite exists in the structure, which will also make the hardness more high.
In-furnace temperature and carbon potential uniformity : In-furnace temperature unevenness has a great impact on uneven hardness, poor furnace sealing and radiation tube failure will affect the uniformity of the furnace temperature. The uniformity of carbon potential is affected by uneven temperature, atmosphere circulation in the furnace, and furnace installation density. In areas with low carbon potential in the furnace, shallow seepage layer and low hardness may occur.
Processing process factors
Grinding process : During the grinding process of the gear, the grinding pressure, grinding speed, and the use of grinding fluid will affect the hardness of the tooth surface. Improper grinding process may cause changes in the hardness of the tooth surface, and even defects such as grinding burns.
Surface treatment : If the gear teeth surface is subjected to surface treatment such as coating, coating, etc., it can improve hardness and wear resistance. Different surface treatment processes and parameters will have different impacts on hardness.
Other factors
Gear design parameters : such as the number of teeth, modulus, pressure angle, etc., will affect the distribution of tooth surface hardness. During the heat treatment process, different design parameters may lead to differences in hardness distribution due to different factors such as stress distribution.
Load conditions : The gear has different requirements for tooth surface hardness under different load conditions. Under high load conditions, higher tooth surface hardness is usually required to ensure the load-bearing capacity of the gear. Long-term operation under high loads may also change the gear hardness.
Environmental factors : The environment in which the reducer is located, such as temperature, humidity, pollution, etc., may also have a certain impact on the hardness of the tooth surface. For example, in a wet or corrosive gas environment, the surface hardness and performance of the gear may be affected.
