Investigation of stress Corrosion Cracking of the Cast and Forging Steel in Water
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摘要: 用同一爐鋼的鑄件和鍛件對比研究了在水介質中的應力腐蝕性能,結果表明,鑄鋼和鍛鋼應力腐蝕裂紋擴展的激活能相同,均為Q=5540cal/mol。且和氫滲透測出的表觀擴散激活能Q=6010cal/mol相—致。無論是陽極極化還是陰極極化均使鑄鋼和鍛鋼的da/dt升高,但陰極極化更為明顯,氫滲透測量表明,無論是陽極極化還是陰極極化,隨電流增大,飽和氫滲透通量明顯增加;極化對da/dt和氫滲透通量影響是相似的。
實驗表明,試驗溫度對KIscc影響極小,但鑄鋼的KIscc明顯比鍛鋼要高。氫滲透測試表明,鍛鋼的飽和氫滲透通量約比鑄鋼要大一倍,這就可解釋KIscc的差異,這也和斷口觀察相一致,盡管斷口形貌明顯依賴開裂時的KI值,但在KIscc附近鍛鋼全是沿晶斷口,而鑄鋼則以準解理為主。Abstract: stress corrosion behavior of the cast and forging steel with the same heat has been investigated.Results showed that the activation energy of crack growth of the cast steel was identical with that of the forging steel and was in agreement with the apparent diffusion activation energy of hydrogen in the steel.Both cathodic and anodic polarization increased the da/dt of the cast and forging steel but the influence of the cathodic polarization was much s-tronger. Correspondingly, the steady-stat hydrogen permeation flux increased steeply with increasing the polarization current, whether cathodic or anodic polarization.
The KISCC of the cast steel was larger than that of the forging steel. It may be due to the fact that the steady-stat hydrogen permeation flux of the forging steel was twice as larger as that of the cast steel.The fracture modes of both cast and forging steel were clearly dependent upon K1 at the crack tip and a transition from dimple to quasi-cleavage or intergranular was observed on the fracture surfaces with decreasing K1. -
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