Hardness is an important performance index of mold materials and finished molds. The quality of heat treatment and service performance of molds are usually judged by hardness, and the wear resistance of molds is determined by heat treatment of molds, especially surface heat treatment, and the main basis for evaluating the wear resistance of molds is hardness. The hardness test of die steel mainly aims at three situations, namely, the hardness test of die steel material, the hardness test of semi-finished die after heat treatment, and the surface hardness test of die surface after heat treatment that requires high wear resistance.
Die steel materials are mainly forged steel plates, steel blocks or steel bars, which are generally supplied in an annealed state. Some plastic die steels are also supplied in pre-hardened state (quenching and tempering treatment), and users can directly process them into dies without subsequent heat treatment. Die steels can be classified into carbon tool steels, alloy tool steels and high-speed tool steels according to steel types. The China standard stipulates the ex-factory hardness requirements for all kinds of die steels, and requires the annealing hardness and sample quenching hardness of steels to be tested. The machined die steel material should be quenched and tempered, and then refined and polished to become the finished die. It is more important to detect the hardness of the die after quenching and tempering, because the hardness of the material at this time is a very important quality index, which largely determines the service life of the finished die.
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