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Knowledge of microstructure in heat treatment of bearing steel
- Aug 01, 2016 -

Knowledge of microstructure in heat treatment of bearing steel:

Martensitic: under normal circumstances, GCr15 quenching temperature to 840 degrees Celsius, there is generally no more than 850 ℃. Quenching temperature of 820 ° c about GCr15SiMn, generally not more than 835. too high or too low temperature causing martensite heat or less hot.

Qualified standard Martensitic 1-5 (micro-parts 1-3). Tightens for small 1-4 for wall thickness (6-7mm) products can be 1-3. Martensite weight associated with heating temperature and time.

Bainite: Bainite isothermal hardening material for general use GCr15 GCr18Mo,GCr15 steel and machined parts within the effective thickness is controlled in the 30mm, GCr18Mo extends 65mm

Heating temperature: whether GCr15 or GCr18Mo, 865 more temperature ¡æ ~890 ¡æ

Isothermal temperature: whether GCr15 or GCr18Mo, the Ms point of 225 ℃, isothermal temperature 235-245 degrees centigrade.

Holding time: generally not less than 4 hours according to the JB/T1255 standard 1-3 qualified, Bainite was associated with temperature and heating time, isothermal temperature and time

Troostite: troostite are heating or quenching of non-Martensitic or bainitic, and don't want it to exist. Standard in the provides effective wall thick not is greater than 12mm, heart Department not is greater than 1-2 level; is greater than 12mm Shi, surface 3mm circumcenter Department not control, surface 3mm within allows few troostite troostite of produced main is cooling bad or heating insufficient produced, main is cooling bad of reasons: oil quenching General heart Department not appeared troostite effective wall thick for 8mm around, salt quenching General heart Department not appeared troostite effective wall thick for 15mm around, strengthening media flow, and improve quenching temperature, and Increase part or parts and equipment gaps, salt water can reduce the occurrence of troostite, can sometimes be found Qu's body on the surface, and not, are generally caused by too much moisture in the media