Study On Grinding Charicteristics Of Cold Working Die Steel9Mn2V For Thread Gauge

Thread gauge is an indispensable measuring tool in the manufacturing of oilcountry tubular goods (OCTG). Generally, thread gauge is made by cold work diesteel and bearing steel to meet the use requirement, using the grinding method ofprocessing after heat treatment involved quenching, tempering and aging treatment.Due to improper heat treatment, grinding defects involved grinding burns and grindingcracks, and badly worn in using process, are two major problems in thread gaugeproducing and using, it would bring a great risk to the quality control and cost waste ofthe OCTG. Therefore, to improve the heat treatment process is of great practicalsignificance for the thread gauge manufacturing to reduce the manufacturing cost ofOCTG.Through orthogonal experiment and other studying methods, this paper uses heattreatment process test and grinding processing experiment for analysis of the influenceon the thread gauge wear resistance and cold work die steel9Mn2V grindingprocessing performance under different heat treatment processes. The cold work diesteel9Mn2V could get an organization of acicular martensite, residual austenite andgranular carbide after quenching, cold treatment, tempering and aging treatmentprocess, which meets the requirements of service conditions and processing propertiesof the thread gauge. For different heat treatment processes, the quenching temperaturemakes greatest impact on the material microstructure and properties, followed bytempering time and aging. The residual austenite content has a big influence onhardness, dimensional stability and material wear resistance, which can be controlledor eliminated by adding the cold treatment or cryogenic treatment process, but thedeep cryogenic treatment has no significant impact on the hardness.Through the grinding process tests, the results indicated that the heat affectedzone of the quenching workpiece grinding surface was deepest, but significantlyreduced after tempering. With the increase of the time of tempering and the extendedtempering time, supersaturated martensite could be promoted to separate out ε-carbide,which made the square degree improved. This change led to a second phase strengthening and better martensite stability, which could effectively reduce theresidual stress of the material organization and eliminate the grinding cracksincentives, and improved the9Mn2V grinding performance eventually.According to the analysis of heat treatment process and grinding test, this paperimproved the route of the original cold work die steel9Mn2V heat treatment process,and the practical results of the thread gauge indicated that the optimal heat treatmentprocess based on the the existing equipment in Baosteel was actually effective.