냉간금형용 STD11강의 내마모 특성에 미치는 크라이오처리의 영향

Abstract

Effects of austenitizing, cryogenic treatment and tempering conditions on the microstructure and mechanical properties have been studied in a commercial STD 11 steel. The results obtained are as follows;

(1) The volume fraction of eutectoid carbides decreased while the size of those becames fine in matrix with extending austenitizing time because of re-solutionizing of eutectoid carbides.

(2) Hardness values showed a tendency to decrease with extending austenitizing time; HRC = 60.9 in a specimen austenitized at 1030℃ for 20 min but HRC = 59.3 and HRC = 58.7 at 1030℃ for 40 and 60min, respectivily.

(3) Finer carbides in size of 10nm or less could be observed by cryogenic treatment at -196℃ after austenitizing, and those carbides were spheroidized and well dispersed with extending cryogenic treatment time. Tetragonality of α󰡑martensite also decreased by cryogenic treatment.

(4) The α󰡑maretensite was transformed into tempered martensite in which ε carbides were precipitated, but primary carbides had no change even by higher tempering temperature.

(5) Wear resistance of STD 11 steel was significantly improved due to modified microstructue i.e., fine and uniform η carbides introduce by cryogenic treatment.