AISI 1015低碳鋼與AISI 304不鏽鋼異質銲件於氯化鈉/硫酸納混和鹽之熱腐蝕

Hot Corrosion Behavior of Dissimilar Weldments of AISI 1015 Low Carbon Steel and AISI 304 Stainless Steel with NaCl/Na2SO4 Mixed Deposit

本研究使用氬銲以309L為銲料將AISI 1015低碳鋼及AISI 304不銹鋼進行異質銲接，銲接部位沉積2 mg/cm2不同比例NaCl-Na2SO4混合鹽後，置於750℃靜滯空氣爐中探討熱腐蝕之影響。鋼料銲接後在低碳鋼熱影響區（Heat Affected Zone, HAZ）與304 HAZ皆發生晶粒成長，且304之HAZ有發生敏化現象，低碳鋼與銲道之界面則有碳化物產生。熱腐蝕實驗結果顯示，304不銹鋼與309L銲道均呈現典型內侵蝕，低碳鋼則為均勻腐蝕之型態，各區侵蝕深度皆隨持溫時間增加而增加；銲道因309L具高鉻含量使其金屬損失量最小。304不銹鋼之HAZ因敏化而具有大的金屬損失及總侵蝕深度；在有足量熔融鹽下，因加凡尼效應而導致在低碳鋼／309L界面之低碳鋼側發生嚴重侵蝕。

The purpose of this work was to study the hot-corrosion behavior of dissimilar weldments of AISI 304 stainless steel and AISI 1015 low carbon steel assembled with consumable-309L stainless steel wires at 750 ℃ in static air with 2 mg/cm2 mixture of various ratios of NaCl-Na2SO4 deposits. It was found that the HAZ of weldments revealed the coarse grain structure and the around 304 HAZ. Moreover, the carbon migrated from the substrate of low carbon steel of the higher chromium weld metal side and formed chromium carbide adjacent to the interface between the low carbon steel HAZ and weld metal. The results of hot corrosion showed that both 304 and 309L appeared the subscale attack while low carbon steel revealed the uniform corrosion. The depth of attack increased with increasing exposure duration of time. The 309L weld metal had the smallest metal loss because of its high chromium content. Due to sensitized reaction the 304 HAZ had the highest metal loss and the total depth of attack. The galvanic effect to the low carbon steel resulted in a serious corrosion with sufficient molten salts at low carbon steel HAZ/WM interface.