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5Cr 계 열간공구강의 응고특성에 미치는 희토류금속 첨가의 영향
송치복,서인교,박현균 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.8
Behaviors of solute elements segregation and primary carbides in the solidification structure of rare earth metals(REM) treated 0.35C-0.45Si-0.33Mn-4.9Cr-1.2Mo-0.8V ingots have been investigated. The important results are summarized as follows. 1) REM addition brought about a remarkable reduction of center-segregation, center-blow hole, and enlargement of equiaxed zone and fine solidification structure. 2) REM addition brought about a remarkable reduction of solute elements segregation area in ingots, so that it resulted in refinement of primary carbides. 3) Crystallized carbides in solute elements segregation area of 5Cr and REM treated ingots were MC of dendrite type and M₂C of skeleton type. Dendrite crystal, solute elements segregation area, and M₂C changed into γ-Fe, MC, M_7C₃, M_(23)C_6 and M_6C by 845℃ soaking treatment. REM addition did not influence on the carbide composition at the same heat treatment.
5Cr 계 열간공구강의 충격인성과 절삭성에 미치는 희토류금속 첨가의 영향
박현균,송치복,소진왕 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.8
A small amount of rare earth metals(REM) was added in melts of 5Cr hot working tool steel in order to investigate the changes in cleanliness, shape control of nonmetallic inclusions, and mechanical properties in comparison with those of typical hot working tool steel. The important results obtained are summarized as follows. 1) REM addition in 5Cr hot working tool steel resulted in significant decreases in final oxygen and sulfur, and total nonmetallic inclusions content. 2) RE-complex inclusions in the form of fine globular less than 3㎛ were composed of RE-oxysulfide surrounded by RE-sulfide. 3) Impact toughness, machinability, and chipability were improved by REM addition, owing to the refining of prior austenite grain size and insoluble carbide, and RE-complex inclusions.