オーステナイト系ステンレス鋼溶接金属のSSRT特性に及ぼす－45℃，106 MPa水素ガスの影響

<p>In order to study the hydrogen embrittlement behavior of austenitic stainless steel weld metals, slow strain rate tensile (SSRT) tests were performed in 106 MPa gaseous hydrogen at −45 °C. Tensile specimens, in which whole of the gauge section consists of weld metals, were machined out from a TIG welded round bar. The base metal was SUS316 (hi-Ni), and the filler metals were 317L, 316 and 316L. The nickel equivalent values of SUS316 (hi-Ni) base metal, and 317L, 316 and 316L weld metals were 29.7, 30.0, 28.9 and 28.3 mass %, respectively. Two types of weld metals were tested; one was as-welded metal, and the other was post-welded solution-treated weld metal. The relative reduction of area, RRA, was 0.55 for 317L as-welded metal, and approximately 0.9 for SUS316 (hi-Ni) base metal and 317L, 316 and 316L post-welded solution-treated weld metals. The result indicated that the resistance against hydrogen embrittlement was improved by the post-welded solution-treatment. The fracture surface of SUS316 (hi-Ni) base metal and 317L post-welded solution-treated weld metal was entirely covered with dimples, whereas the fracture surface of 316 and 316L post-welded solution-treated weld metals was covered with dimples and quasi-cleavages. Accordingly, it was concluded that 317L post-welded solution-treated weld metal with the highest nickel equivalent had an excellent resistance against hydrogen embrittlement, which was recommended for use in high-pressure hydrogen components.</p>