Investigation on the microstructure and mechanical properties of tempered optical mould stainless steel

• Main Authors: Chih-Yuan Shang, 商智苑
• Other Authors: 吳威德
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/82176026434097664654

碩士 === 國立中興大學 === 材料科學與工程學系所 === 104 === This research disscussed of stainless steel in microstructure and mechanical properties after vacuum heat treatment in quenching and 1~3 times tempering . SUS 420J2, SUS 440C, M390 were treated in vacuum furnace for hardening and tempering. M390 be the experimental group, SUS 420J2 and SUS 440C material to be the control groups. Optical microscope, Scanning electron microscope (FE-SEM) and Cu-target X-ray diffraction were used to investigate the steel microstructures, characteristics and identified the carbide type and martrix phase. Wear resistance was estimated with dry sand wheel wear test. Charpy test was performed to vertify the toughness (impact energy) of steel. Retained austenite content values were measured by X-ray with Cr-target device and using SEI/BEI image for carbide type analysis. For SUS 420J2, the primary carbide is M23C6 (Cr-rich) and the smaller carbide M23C6 (Fe-rich) is the main precipitation from martrix ; SUS 440C, the primary M7C3 (Cr-rich) carbide with long strip segregation and the small size carbide precipitated with M23C6 (Fe-rich) type in martrix. The primary M7C3 (Fe-Cr-V) carbide of M390 is the main precipitation in martrix and secondary carbide VC precipitated after tempering. In BEI analysis, we found a part of VC carbide is sourced from M7C3 after tempering. Hardness test analysis shows the high hardness of M390 steel have the excellent wear resistance, because secondary carbide of VC with high hardness and higher C composition. Retained autensite (RA) of stainless steel was measured by Cr- target X-ray in texture TD direction of bulk. Aftering quecnhing and tempering, RA contennt values can influence toughness dut to cracking resistance mechanism.