Effect of composition and degree of deformation on the carbice heterogeneity of high-speed steels

Abstract

1. In their tendency to develop carbide heterogeneity as a function of the composition the high-speed steels investigated are arranged in the following order: R18K5F2, R10K5F5, R18F2, R14F4, R9F5, R18, R12, R9K10, R6M3, R9K5. 2. Carbon and tungsten have a substantial effect on the tendency of high-speed steels to develop carbide heterogeneity. The effect of carbon is stronger than that of tungsten, which can be seen from the positions of steels R18 and R9F5 in the sequence given above. 3. The effect of vanadium is weaker than that of tungsten, which can be seen by comparing the order of steels R18F2 and R14F4. Despite its higher carbon concentration, steel R14F4 has less tendency to develop carbide heterogeneity than steel R18F2. 4. Cobalt, forming an intermetallic phase with tungsten [8], increases the structural heterogeneity of high-speed steel according to the GOST 5952-63 scale, since it is impossible to differentiate the intermetallic and carbide phases in the microanalysis. 5. Molybdenum induces less tendency to develop carbide heterogeneity as compared with tungsten. This fact makes tungsten — molybdenum steel promising for manufacturing large tools. 6. Carbide heterogeneity standards should be established by separating high-speed steels into four groups, depending on their tendency to develop structural heterogeneities (see Table 3). 7. The degree of carbide heterogeneity in rods more than 40 mm in diameter (or square) can be reduced only by increasing the forging reduction ratio, i.e., by using ingots weighing 500–1000 kg, when the technological ductility of the steel makes this possible.