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pISSN : 1598-706X / eISSN : 2288-8381


(논문)연구논문

한국주조공학회지 (26권1호 17-26)

Applicability of Air Cooling Heat-treatment for a Duplex Stainless Steel Casting

2상 스테인레스 주강의 공냉 열처리 적용 가능성

Bong-Whan K im, Sik Yang, Je-Sik Shin, Sang-Mok Lee, Byung-Moon Moon

Korea Institute o f Industrial Technology

Abstract

The substitution o f cooling method from water quenching to air cooling after solution heat treatment was aimed for the development o f a convenient and economical heat treatment process o f duplex stainless steels without deterioration o f mechanical and corrosion resistant properties for the industry. In order to achieve this goal, the mechanical properties and corrosion properties o f a ASTM A890-4A duplex stainless steel were systematically investigated as functions o f casting condition and cooling method after solution heat treatment. A 3-stepped sand mold and a permanent Y-block mold were used to check the effects o f solidification structure and cooling rate after solution heat treatment. The microstructural characteristics such as the ferrite/austenite phase ratio and the precipitation behavior o f a phase and carbides were investigated by combined analysis o f OM and SEM-EDX with an aid o f TTT diagram. Hardness and tension test were performed to evaluate the mechanical properties. Impact property at -40°C and corrosion resistance were also examined to check the possibility o f the industrial application o f this basic study. Throughout this investigation, air-cooling method was proved to effectively substitute for water- quenching process after the solution heat treatment, when the duplex stainless steel was sand mold cast with a thickness below 15 mm or permanent mold cast with a thickness below 20 mm.

Keywords

ASTM A890-4A duplex stainless steel, Solidification structure, Solution heat treatment, Cooling method, Phase ratio, a phase, Mechanical properties, Corrosion resistance.