SSC hydrogen sulfide stress corrosion
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In the presence of water and H2S, the corrosion and tensile stress related to a metal cracking.
SSC is related to the metal embrittlement caused by the hydrogen induced corrosion on the metal surface. In the presence of sulfide, it will promote the absorption of hydrogen. Atomic hydrogen diffusion into the metal, reduce metal toughness, increase the crack sensitivity. High strength metal materials and hard weld area are easy to occur SSC.
Basic requirements for anti H2S corrosion of steel: editing
The composition design is reasonable: material resistance to H2S stress fracture properties are mainly related to the grain boundary strength of materials, often adding elements Cr, Mo, Nb, refined Ti and Cu alloy original austenite grain size. Ultrafine grained primary austenite after quenching, the formation of ultra-fine grain ferrite and fine carbide microstructure distribution, is the most effective way to develop high strength steel resistant to sulfide stress corrosion.
The use of harmful elements (including hydrogen, oxygen, nitrogen, etc.) with a very low content of pure steel;
The tempering good hardenability and uniform and fine, the hardness fluctuates as small as possible;
The tempering stability, high tempering temperature (>600 C);
The good toughness; residual tensile stress.
Sulfide stress corrosion is a special type of stress corrosion, but the difference with the stress corrosion usually said, corrosion stress usually said, it is the role of the anodic dissolution, and SSC is the main cathodic hydrogen charging. At present, the SSC mechanism has not yet been fully revealed, but most scholars tend to this cracking is caused by hydrogen, and sulfur ions or hydrogen sulfide on the diffusion of hydrogen into the material has a certain role in promoting. In the oil and natural gas (especially natural gas) pipeline, high pressure and high strength pipeline sulfide stress corrosion cracking will lead to serious accidents, so the need for anti SSC performance evaluation of pipeline steel, ensure the safety of pipeline