Microstructural and Mechanical Properties of 308 and 409 Stainless Steel Welded by GTAW Process
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Microstructural and Mechanical Properties of 308 and 409 Stainless Steel Welded by GTAW Process R. Saldaña-Garcésa, A. F. Miranda-Pérezb, G. Y. Pérez-Medinac, Y. N. BarrónVargasd, F. A. Reyes-Valdése Corporación Mexicana de Investigación en Materiales. Saltillo, Coahuila. México. a [email protected], [email protected], c [email protected], [email protected], [email protected]
ABSTRACT Today, stainless steel is widely used in automotive industry due to its high impact resistance, corrosion resistance and light weight. This paper present the research carried out to study the differences between microstructure and mechanical properties of 409 and 308 stainless steel sheets, each joints by gas tungsten arc welding (GTAW). For each of weldments, detailed analysis was conducted on the chemical composition, microstructure characteristics and mechanical properties of base metal (BM), heat affected zone (HAZ) and fusion zone (FZ). Scanning electron microscopy (SEM) and optical microscopy were used to analyze microstructural changes and mechanical properties, including microhardness and tensile test. This study can be a practical guide in the selection of other materials in order to determine the important to use in structural automotive industry. Keywords: stainless steel, GTAW, microstructure, mechanical properties, welding. INTRODUCTION The employment of stainless steels is widely used metal after carbon steel, austenitic stainless steels are commonly seen at chemical and process industries in vessel internals, tanks and distillery equipment, etc., while, ferritic stainless steels are more employed on chemical plants, pulp and paper industry and refinery [1-3]. This is due to their high temperature resistance, superior mechanical and corrosion properties [3-6]. Lately, these classes of steels have been introduced into automotive sector, due to their high impact and light weight. Welding becomes as primary importance when it comes to the focus of the material performance, when is applied their microstructure of fully austenite, ferrite, ferrite/austenite and ferrite/martensite mixture depends in the balance of promoting elements of each phase [4,7,8]. In certain austenitic stainless steels welds with a completely austenitic matrix are commonly prone to hot cracking [9,10], and sometimes in the weld filler material delta δ-ferrite promoting elements are added in order to minimize this tendency [11]. This study was carried out, in order to have a deeper knowledge on the microstructure changes on welded stainless steels with Gas tungsten arc welding. GTAW process in ferritic and austenitic stainless steels had not reached its full potential so far; since there is limited weldability data published literature. This paper deals with the characterization of austenitic 308 and ferritic 409 welded stainless steels with GTAW. Mechanical testing and microstructural examinations were carried out in order to evaluate the welds. Furthermore, their properties-microstructure relationship were analyzed
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