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用热模锻压力机生产阀门、紧固件、轴等杆类零件时,广泛采用热挤压。此时,模具的使用条件,无论温度或载荷方面的要求都很严格(例如,挤压CM型柴油机阀门时,单位压力达860兆帕,模腔的表面温度为1220K)。热挤压模报废的主要原因是热疲劳网状裂纹的形成,这导致锻件表面上出现所谓的《色条》。热疲劳网状裂纹出现在加载的最初几个周期中,也就是说,这些模具的寿命,主要取决于在周期性冲击力的条件下,模具钢抵抗热疲劳裂纹增长的程度。
Hot die forging press production of valves, fasteners, shafts and other rod parts, the widespread use of hot extrusion. At this point, the mold conditions of use, regardless of temperature or load requirements are stringent (for example, when compressing CM diesel valve unit pressure of 860 MPa, the cavity surface temperature of 1220K). The main reason for the hot extrusion dies being scrapped is the formation of a thermal fatigue web crack, which causes so-called “color bars” on the surface of the forging. Thermal fatigue Mesh cracks occur during the first few cycles of loading, that is, the life of these dies depends primarily on the extent to which the tool steel resists the growth of thermal fatigue cracks under cyclic impact conditions.