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<p>In austenitic stainless steels, low-temperature sensitization (LTS) in the heat-affected zone (HAZ) of welds can cause intergranular corrosion and stress corrosion cracking (SCC). However, in recent years, the occurrence of SCC owing to material hardening has been confirmed even in areas where sensitization is not observed, and attention has been focused on the hardening behavior in HAZ. However, the precipitation hardening behavior in HAZ of welds during low-temperature thermal aging has not been sufficiently investigated. Therefore, in this study, the precipitation hardening behavior in HAZ of welds in austenitic stainless steel was investigated by conducting hardness measurements within the grains after low-temperature thermal aging at 350 °C to 500 °C. Based on the results, a novel phenomenon in HAZ of welds was proposed as “low-temperature precipitation hardening (LTPH),” and the mechanism of hardness behavior owing to LTPH was also investigated. The proposed LTPH phenomenon may occur in HAZ of austenite stainless steel welds in nuclear power plants operating at ~ 300 °C for long period, which may be an important cause for the occurrence of SCC and should be given high attention in future.</p>

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A Phenomenon of Low-Temperature Precipitation Hardening in Heat-Affected Zone of Austenitic Stainless Steel Welds

  • 期刊论文

  • 发表日期：

    2025年7月14日

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  • Lina Yu,
  • Kazutoshi Nishimoto,
  • Hiroyuki Hirata,
  • Kazuyoshi Saida

摘要

In austenitic stainless steels, low-temperature sensitization (LTS) in the heat-affected zone (HAZ) of welds can cause intergranular corrosion and stress corrosion cracking (SCC). However, in recent years, the occurrence of SCC owing to material hardening has been confirmed even in areas where sensitization is not observed, and attention has been focused on the hardening behavior in HAZ. However, the precipitation hardening behavior in HAZ of welds during low-temperature thermal aging has not been sufficiently investigated. Therefore, in this study, the precipitation hardening behavior in HAZ of welds in austenitic stainless steel was investigated by conducting hardness measurements within the grains after low-temperature thermal aging at 350 °C to 500 °C. Based on the results, a novel phenomenon in HAZ of welds was proposed as “low-temperature precipitation hardening (LTPH),” and the mechanism of hardness behavior owing to LTPH was also investigated. The proposed LTPH phenomenon may occur in HAZ of austenite stainless steel welds in nuclear power plants operating at ~ 300 °C for long period, which may be an important cause for the occurrence of SCC and should be given high attention in future.