焊接熱循環(huán)對Q315NS鋼在H2SO4溶液中腐蝕行為的影響焊接熱循環(huán)對Q315NS鋼在H2SO4溶液中腐蝕行為的影響EFFECT OF WELDING THERMAL CYCLE ON CORROSION BEHAVIOR OF Q315NS STEEL IN H2SO4 SOLUTION 采用焊接熱模擬技術和電化學測試系統(tǒng)，研究了Q315NS鋼焊接熱影響區(qū)組織轉(zhuǎn)變規(guī)律及焊接熱循環(huán)對其腐蝕行為的影響，實驗結(jié)果表明：Q315NS鋼母材、細晶區(qū)和混晶區(qū)微觀組織均由鐵素體和珠光體組成，粗晶區(qū)主要由粗大的粒狀貝氏體組成。在質(zhì)量分數(shù)為50%的H2SO4溶液中，母材和熱影響區(qū)的等效電路中均包含一個電荷轉(zhuǎn)移電阻和一個由雙電層產(chǎn)生的常相位角元件，并都發(fā)生了鈍化行為。母材和混晶區(qū)的電荷轉(zhuǎn)移電阻最大，腐蝕電流密度最小，耐腐蝕性能最好；粗晶區(qū)電荷轉(zhuǎn)移電阻最小，腐蝕電流密度最大，耐腐蝕性能最差。腐蝕72h后，在母材、細晶區(qū)和混晶區(qū)表面形成了由腐蝕溶液和基體直接反應生成的孔洞狀腐蝕產(chǎn)物膜，而在粗晶區(qū)表面形成了由析出的硫酸鹽晶粒吸附在基體表面并長大形成的短棒狀腐蝕產(chǎn)物膜，腐蝕產(chǎn)物均主要為Fe2(SO4)3。 Q315NS steel has been used as structural material in economizers, air preheaters, chimneys and other fields due to its low cost and good corrosion resistance. However, there is little research elucidating the effect of welding thermal cycle on corrosion behavior of Q315NS steel in H2SO4 solution. Therefore, the microstructure evolution and corrosion behaviour in the 50% (mass fraction) H2SO4 solution of welding heat affected zones of Q315NS was investigated by comparison with base metal using welding thermal simulation technique, SEM and electrochemical measurements. The results show that the microstructure of ferrite and pearlite is observed in base metal, fine-grained region and incomplete recrystallization region, while coarse-grained region consists of granular bainite. All the equivalent circuits of Q315NS with or without welding thermal cycle contain a resistor of corrosion product film and a capacitor of electric double layer, and all specimens have passivation behavior. The base metal and the incomplete recrystallization region have the lowest corrosion current density and the largest charge-transfer resistance, which means the best corrosion resistance, while the coarse-grained region has the highest corrosion current density and the least charge-transfer resistance. A rod-like structure corrosion product film was formed by deposition on the surface of the coarse-grained region while a porous structure product film was formed by the reaction of H+ and Fe directly on the surface of other specimens. 全文下載：http://pan.baidu.com/s/1c2CoqU
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