IMPROVING THE CONTINUOUS CAST BLANK STRUCTURE BY USING MICRO-COOLANTS
Paper intended to clarify some problems regarding the accomplishment of an improved crystalline of the continuously cast blanks using the micro-coolant addition during the continuous casting of the steel. The industrial experiments were made within a metallurgical plant having a continuous casting machine for blooms with a 240x270mm section. Micro-coolants as grains were added in the mould of the continuous casting machine, on a single thread. The conclusions got from analyzing the casting structure of the experimental blanks (with addition of micro-coolants in the mould) in comparison with the common casting structure (witness blank) are presented.
RESPECTS REGARDING THE USAGE MICRO-COOLERS TO CASTING STEEL
Basic problem, which must solve to casting steel, consists in the smooth ingots procurance insurance from chemical point of view, structural and of mechanical ownerships. For the defects mitigation to solidification classic, it is the needed adjustment to an efficient methods exhaust of warmth from the steel under solidification through the administration of micro-cooler under form of grains to casting. Micro-coolers you utilize with the view of process directing of solidification must achieve conditions series: to have a heaved purity respecting the content of oxide inclusions; the wet micro-coolers uttermost 0, 25%; to not have surface oxidant; to have a certain granulometric composition. The work clears the aspects related interaction micro-coolers you deal to casting steel over solidification to this. As parameters, which influence the process of solidification they were taken in the dimensions, study micro-coolers, the specific enlargement of micro-cooler, steel temperature in the enlargement moment while as the influenced parameter steel volume in which they acted microcoolers. Through analysis of regression by the agency of program Excel and Matlab they obtained dependence between meal micro-cooler you utilize to casting ingots from temperature and steel of casting, correlations which they allow the optimal areas establishment variation for temperature of casting, the quantity of micro-cooler dealt respective affected volume percent of cooling to the administration micro-coolers.
Solidification of high speed steels
Abstract High speed steels are ferrous based alloys of the Fe–C–X multicomponent system where X represents a group of alloying elements comprising mainly Cr, W or Mo, V, and Co. These steels are mainly used for cutting tools, since they are characterised by their capacity to retain a high level of hardness while cutting metals at high speed. The as cast microstructure of high speed steels consists of dendrites surrounded by a more or less continuous interdendritic network of eutectic carbides. These are observed even under rapid cooling, at rates as high as 106 K s-1. The main features of the as cast microstructure are the distribution and morphology of eutectic carbides, owing to their decisive influence on mechanical properties, and on the service performance of the high speed steels, even after hot working. Hence, the most important improvements on the as cast microstructure that have been obtained through progress in alloy design concern the type, morphology, and volume fraction of the eutectic carbides, while improvements obtained by progress in solidification processing are, on the other hand, mostly related to a significant reduction in the microstructure scale. The development of the microstructure in high speed steels through solidification is reviewed, emphasising the effects of the alloy chemical composition and of the cooling rate. The formation of the eutectic carbides and the techniques used to control their morphology and distribution, both under normal and rapid cooling, are discussed. Microstructures obtained through surface remelting and surface alloying using laser and electron beams are described, and the application of highly alloyed high speed steels to the manufacture of cast hot rolling mill rolls is reviewed.