The effect of quenching on the solidification structure and transformation behavior of stainless steel welds |
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Authors: | S Kou Y Le |
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Affiliation: | (1) Department of Metallurgical Engineering and Materials Science, Carnegie-Mellon University, 15213 Pittsburgh, PA |
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Abstract: | Weld solidification structure of three different types of stainless steel,i.e., 310 austenitic, 309 and 304 semiaustenitic, and 430 ferritic, was investigated. Welds of each material were made without
any quenching, with water quenching, and with liquid-tin quenching during welding. The weld micro-structure obtained was explained
with the help of the pseudobinary phase diagrams for Fe-Cr-Ni and Fe-Cr-C systems. It was found that, due to the postsolidification
5 → γ phase transformation in 309 and 304 stainless steels and the rapid homogenization of microsegregation in 430 stainless
steel, their weld solidification structure could not be observed unless quenched from the solidification range with liquid
tin. Moreover, the formation of acicular austenite, and hence, martensite, at the grain boundaries of 430 stainless steel
welds was eliminated completely when quenched with liquid tin. The weld solidification structure of 310 stainless steel, on
the other hand, was essentially unaffected by quenching. Based upon the observations made, the weld microstructure of these
stainless steels was summarized. The effect of cooling rate on the formation of primary austenite in 309 stainless steel welds
was discussed. Finally, a simple method for determining the relationship between the secondary dendrite arm spacing and the
solidification time, based on welding speeds and weld pool configurations, was suggested. |
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