A.MS>350℃,WC<0.2%B.MS<200℃,WC>1.0%C.MS200℃~300℃,WC0.2~0.5%D.MS300℃~350℃,WC0.5~1.0%
A.40mmB.60mmC.80mmD.90mm
A.1~3级B.3~5级C.4~6级D.5~8级