Golovachov A. Development of Metallurgical Fundamentals of Resource-saving Technologies of Composite Ingots making from High Speed Steel.

Dissertation is devoted to theoretical basics of metallurgical methods on making the composite ingots of high speed steel and experimental estimation of effectiveness of both "Liquid Sandwich" (LS) and Electro Slag Surfacing by Liquid Metal (ESS LM) technologies for production of metal cutting tools. Stability of carbides and the equilibrium compositions of phases in steel W6Mo5 (M2) and in steel with reduced content of alloying elements, which formed in central volume of LS ingot, have been thermodynamically evaluated. On basis of recent theories of lowering of liquidus temperature at enriching of the alloy by the second component it was shown the theoretical possibility to increase it by use of addition of much hot but less alloyed alloy. There were methodic and software created that allows us to forecast the composition, liquidus temperature and mechanical properties of steel. Due to two-step mathematic model the numeral experiment was done for optimization of parameters of LS composite ingot casting. Technology of pouring of LS composite ingot W6Мo5+42Cr4 (5140) was tested in industry. Number of tests of structure and properties of produced metal showed complete correspondence to GOST 19265 requirements. Industrial tests of tools from composite steel shown full correspondence to norms of cutting accepted for steel W6Мo5. It is shown that there is a small grain created with ESS LM due to the fact that there are two cooling surfaces that allows us to exclude deformation when producing of large dimension tools. The developed technologies of manufacture of composite high-speed steel ingots allow to save alloying elements and the competitiveness of produced tools.