S17CK於高溫腐蝕後抗拉強度預估方法之研究

The Study of Estimating in Tensile Strength for S17CK after High Temperature Corrosion

選用低碳鋼S17CK於750℃及850℃進行氧化、氯化鈉熱腐蝕試驗，藉由金相檢驗法、化學清洗法所計算而得之截面積減損百分率並與腐蝕後拉伸之結果相比較，找出主要影響之因素。結果顯示熱軋低碳鋼受高溫腐蝕後，抗拉強度衰減之主導機制隨反應之進行時間而有變化。於高溫腐蝕之初始階段，退火是主要的作用因素；此後，則由脫碳所主導。於已脫碳之後期反應，因腐蝕而引起的截面積減損量變，則為抗拉強度衰減之最主要作用因素。經由實驗結果之分析，本研究提出一套金屬材料於高溫腐蝕後抗拉強度衰減之預估程序及其計算模式。

The factors which dominate the decay of tensile strength of the low carbon steel S17CK underwent high temperature oxidation and NaCl-induced hot corrosion at 7500 and 850℃ can be determined by comparison of the optical microscopy and chemical cleaning analysis of the cross section area loss ratio and with the corresponding tensile strength results. The analysis showed that the dominating factors on the decay of tensile strength depended on the reaction stages which occurred in the hot corrosion of hot rolled steel at high temperature. The initial reduction of tensile strength was due to the high temperature annealing effect. Subsequently, the decarburization effect became dominate. The cross section area was decreased due to corrosion attack in decarburized region, resulting in the tensile strength reduction. Moreover, based on the experimental results, an evaluation procedure and mathematical model of estimating tensile strength for metallic materials was also developed in this study.