Study of the Effects of the Welding Parameters of GTAW Process on the Mechanical and Microstructural Properties of Auste
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Study of the Effects of the Welding Parameters of GTAW Process on the Mechanical and Microstructural Properties of Austenitic Stainless Steel 304L M. A. Banda*, J. L. Acevedo, J. J. Ruiz, F. Cepeda Corporación Mexicana de Investigación en Materiales S.A. de C.V., Ciencia y Tecnología #790. Fracc. Saltillo 400, C.P. 25290, Saltillo, Coahuila, México, (844) 4113200 Ext. 1215, Fax (844) 4113210. Email: [email protected]
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ABSTRACT The low thickness stainless steel is widely used in the food and automotive industry and also to manufacture heat exchangers in the transport of fluids, due the stainless characteristics, in these applications the quality control of the pipe is very high, that is why it is important to achieve a strict control of the welding parameters during the manufacturing process. In order to quantify the effect of the travel speed and the hydrogen content in the shielded gas of the welding quality different test were performed with low thickness tubing’s welded by GTAW process without filler material. The weld specimens were characterized by optic microscopy and scanning electron microscopy, energy dispersive x-ray spectrometry, and mechanical test like micro hardness and reverse. It was found that when the travel speed increase, a lack of penetration on the welding is observed when the hydrogen content is low, due a lower heat input.
Key words: microstructure, steel, welding, scanning electron microscopy (SEM).
INTRODUCTION The austenitic 304L stainless steels have a good weldability [1, 2] its main applications are the pipe diameters manufacturing used in the food and automotive industry. In the mixtures of shielding gases the hydrogen is used on welding applications of stainless steels due to the increment of the stability of the arc which increase the heat input that affects the penetration of the material [3-5]. Several researchers in the welding field have studied the effect of hydrogen as protective gas in stainless steels on thicknesses of 4-13 mm [6-8] but there are no research works on thin materials (0.71 mm) as the case of this study. The aim of this study is to evaluate the effects of the use of hydrogen as a shielding gas and the welding travel speed in thin materials in the microstructure, penetration of the weld and in the mechanical properties of the weld. EXPERIMENTAL The samples analyzed during this experiment correspond to an austenitic stainless steel pipe 304L, which had dimensions of 0.71 mm width and 12.06 mm in diameter. The welding joint configuration was a butt weld and the welding process used was GTAW without filler material. The chemical composition for the base metal was obtained by Optical Emission Spectrometry (OES) and its results are shown in Table 1.
Mater. Res. Soc. Symp. Proc. Vol. 1275 © Materials Research Society
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Table. I. Chemical composition obtained by OES Si Mn P S Cr Mo Ni Fe 0.38 1.64 0.024 0.015 17.9 0.01 7.92 Balance
The table 2 presents the parameters used in the tests, the amperage and voltage were constant; the percentage of hydrogen w
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