Carbide dies are forged with steel knotted carbide that is softened and annealed prior to cutting. And the steel junction carbide is quenched and tempered after cutting before it is put into use. The common heat treatment processes are spheroidizing annealing, quenching and tempering, which are introduced as follows.
1. Isothermal spheroidizing annealing
The sintered forging organization of cemented carbide dies consists of fine pearlite and hard phases WC and TIC with high hardness. For example, sintered 50% WC chromium-molybdenum steel carbide, hardness HRC ≥ 45, annealed and softened to facilitate cutting, while preparing for future heat treatment. The spheroidal degradation process is: heating to 850~890°C, holding for 4 hours, cooling in the furnace to about 730°C, holding for 6 hours, cooling in the furnace to below 500°C, and air cooling out of the furnace. Annealing temperature should not be too high, heating time should not be too long, otherwise for alloy materials containing a large number of carbides, will cause carbide aggregation and coarse organization, more serious may appear a large number of stable carbide phase, or even graphitization, so that the quenching effect and product quality significantly reduced.
2. Quenching process
The purpose of hard alloy die quenching is to transform the matrix into martensite, to obtain higher mechanical properties. Because of poor thermal conductivity, preheating is required. The hard phase carbides in steel junction carbide can prevent the austenite grain growth, while the alloy carbides in the matrix will hinder the diffusion of iron and carbon atoms. Therefore, steel-jointed carbide has less tendency to overheat during quenching than alloyed tool steel, and quenching heating temperatures can be higher and times can be longer. Generally, for WC steel bonded carbide, the quenching for TiC steel bonded carbide, the quenching temperature is 950 ~ 1000℃; for g-type steel bonded carbide with HSS as the bonding phase, the quenching temperature is 1200~1280℃.
Post time: Jun-20-2023
