中国国产av片_日本丰满妇人成熟免费中文字幕_青青草原国产av福利网站_午夜中文无码无删减_99久久无码一区人妻A片贼王_老司机在线精品视频网站_亚洲嫩模初次开破苞流血_无码少妇一区二区三区浪潮AV_酒店大战丝袜高跟鞋人妻_亚洲精品久久区二区三区蜜桃臀

Hot work die steel can be divided into: die casting die steel, hot forging die steel and hot extrusion die steel according to the use.

Die life generally depends on the wear resistance of die materials. This also determines the properties of hot work die steel.

1. hardness. Sufficient hardness can ensure that the geometric dimension of the die remains unchanged under the action of high stress. The hardness of hot work die steel is generally required to be kept between hrc40 and 55.

2. thermal hardness. High thermal hardness can ensure the stability of the structure and properties of the hot working die at high temperature. The thermal hardness depends on the chemical composition of the material and the heat treatment process. The thermal hardness of carbon tool steel and low alloy tool steel is generally 180 ~ 250 ℃, and that of chromium molybdenum hot working die steel is generally 550 ~ 600 ℃