中性子およびⅩ線回折によるオーステナイトステンレス鋼機械部晶の熱残留応力測定

摘要

Thermal residual stresses in a solution-treated mechanical part made of SUS 304 stainless steel were studied. By using a serial polishing method, the stress distribution near the surface was examined by X-ray sinV method while triaxial stress condition in the inner region was measured by neutron diffraction for a forged specimen. High hydrostatic tensile stress was estimated in the inner region from the X-ray results and then directly mea­sured by the neutron method. It was found that the thermal residual stress was hardly relaxed by stress relief annealing. In case of a part made by casting, it was extremely difficult to measure residual stress either by X-ray nor neutron because of a coarse textured grain structure. The use of a common pallet and digitizer was proposed to perform the X-ray and neutron stress measurement systematically.%オーステナイト鋼は溶体化処理後に析出等を避けるため急速冷却する必要がある（1）。熱伝導率が低いので大型部品では温度分布が生じて熱残留応力が発生しやすい。熱処理後に機械加工を行う段階で残留応力に起因した破壊が起こることもある。回転機械部品の引張残留応力は疲労破壊や応力腐食割れの要因となるので正確な測定と応力除去が望まれている。そのため，水冷後に低温長時間の応力除去焼鈍が施されることが多い（1）が．その効果は明らかでない。