It's Hot Work for Die Steels

摘要

Hot Work Tool Steels are the most commonly used materials for High Pressure Diecasting (HPDC) dies, but alternatives such as Maraging Steels and special high temperature resistant materials are becoming more frequently used where service conditions are more demanding. These special materials include Nickel base alloys, Tungsten, Molybdenum, Nickel Aluminides, and ceramic type materials. Increasing use of Surface Engineering is also being made to improve the performance of conventional die steels using techniques such as Nitriding, Carbo-nitriding, and Physical and Chemical Vapour Deposition (PVD and CVD) to produce controlled depth surface regions containing hard constituents such as carbides and nitrides to increase wear resistance (1). The material requirements for HPDC dies can be summarized as follows: Resistance to wear and attack by liquid metals, entrained oxides and dross. High thermal and mechanical fatigue cracking resistance in order to resist fine cracking, chipping damage and gross fracture (See Figure 1) High strength Structural and dimensional stability during service Resistance to softening in service Ability to be machined or ground during die making Ability to be electro-discharge machined (EDM) to complex shapes. Ability to be surface treated in order to reduce friction and increase wear resistance.