報告書番号

280015

タイトル（和文）

原子炉配管用ステンレス鍛鋼材の耐ＳＣＣ性評価

タイトル（英文）

EVALUATION OF SCC SUSCEPTIBILITY FOR NUCLEARGRADE STAINLESS STEEL PIPES PRODUCED BY FORGING

概要 （図表や脚注は「報告書全文」に掲載しております）

３０４ＬＮおよび３１６ＬＮステンレス鋼製２４インチ鍛造パイプに関してＳＣＣ感受性およびその他の基礎的諸性質を調べた。（１）８ｐｐｍの溶存酸素を含む２８８Ｃの高温純水中におけるＳＣＣ感受性は次のようになる。降伏強度の１．３５および１．８０倍の定重試験を約３，７００時間実施したがＳＣＣは生じなかた。また厳しい条件による繰り返し引張試験でも，約２３０サイクルまでＳＣＣの発生はなかった。さらに最小４．２×１０Ｅ─７／秒のひずみ速度による定速引張法でもＳＣＣ感受性は示さずその破面は延性を示すディンプルパターンであった。（２）ストラウス液による腐食後の曲げ試験で割れの発生はみられず，また粒界腐食による重量減少も極めて小さい。室温および３００Ｃの降伏強度，引張強度，全伸びおよび絞りのいずれの値も原子力用３０４および３１６ステンレス鋼の規格

概要 （英文）

FOR THE LOW CARBON AND NITROGEN SOLUTIONIZEDSTAINLESS STEEL 24B PIPES PRODUCED BY FORGING,THE STRESS CORROSION SUSCEPTIBILITY AND FUNDAMENTAL PROPERTIES WERE INVESTIGATED. (1)AS FOLLOWSWAS THE SCC SUSCEPTIBILITY IN 288 DEGREE(C)HIGH PURITY WATER CONTAINING AIR-SATURATED DISSOLVED OXYGEN(APPROXIMATELY 8 PPM). SEVERELY SENSITIZED MATERIALS SHOWED NO SCC UP TO ABOUT 3700 HRS IN THE CONSTANT LOAD TEST OF 1.35 AND 1.80TIMES YIELD STRESS APPLIED STRESSES.NO SCC WAS ALSOCAUSED IN THE CYCLIC TENSION TEST WHICH WAS CONDUCTED UP TO 230 CYCLESUNDER THE SEVERE TESTING CONDITION.CONSTANT EXTENSION RATE TEST(CERT)AT MINIMUM 4.2E-7/S STRAIN RATE EXHIBITED NO SCC,WHOSE FRACTURE MODE WASONLY THE DUCTILE FEATURE OF DIMPLE PATTERN. (2)FUNDAMENTAL PROPERTIES OF THE MATERIALS WERE MAINLY AS FOLLOWS.THE CRACKING WAS NOT CAUSED BY BENDING TESTS AFTER CORROSION IN THE STRAUSS SOLUTION,AND THE WEIGHT LOSS THE SEVERELY-SENSITIZED MATERIAL ALSO SHOWED EXTREMELY LOW VALUE IN THE SAME INTERGRANULAR CORROSION SOLUTION.ALL THE TENSILE TEST PROPERTIES AT ROOM TEMPERATURE AND 300 DEGREE(C),WHICH INCLUDED 0.2% OFFSET PROOF STRESS,ULTIMATE TENSILE STRENGTH,TOTAL ELONGATION AND REDUCTION OF AREA,SATISFIED THE CRITERIA OF THE NUCLEAR-GRADE 304 AND 316 STAINLESS STEELS. THE MATERIALS SHOWED HIGH TOUGHNESS MEASURED BY V-NOTCHED CHARPYTEST. FROM ABOVE RESULTS,THE 304LN AND 316LN STAINLESS STEEL PIPES PRODUCED BY FORGING WERE EVALUATED TO BE NEW PROMISING ALTERNATE MATERIALS.

報告者

キーワード