Austenitic Stainless Steel - Patent 8133431

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Austenitic Stainless Steel - Patent 8133431 Powered By Docstoc
					
				
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Description: The present invention relates to an austenitic stainless steel, particularly to an austenitic stainless steel which contains C-fixing elements. More particularly, the present invention relates to an austenitic stainless steel, which containsC-fixing elements and can be applied in manufacturing heating furnace pipes and the like which are used in power plant boilers, petroleum refining and petrochemical plants. Still more particularly, the present invention relates to an austeniticstainless steel, which contains C-fixing elements and shows excellent liquation cracking resistance and embrittling cracking resistance in a weld zone and also has high corrosion resistance, in particular high polythionic acid stress corrosion crackingresistance.BACKGROUND ART Due to the recent growing demand for energy, new power plant boilers, petroleum refining and petrochemical plants have been built. An austenitic stainless steel to be used in these manufacturing heating furnace pipes and the like, for use inthose facilities is required to have not only excellent corrosion resistance but also excellent high temperature strength. In such a technological background, for example, the Non-Patent Document 1 proposes a highly corrosion resistant austenitic stainless steel, having a reduced content of C together with N which is set at a level within a specified range, andcontaining Nb as a C-fixing element at a level within a specified range, thereby having excellent stress corrosion cracking resistance and high temperature strength, and showing no sensitizing even after a long period of aging without post heat treatmentafter welding. Concerning the cracking in the Heat Affected Zone (hereinafter referred to as "HAZ") of the austenitic stainless steel which contains C-fixing elements after welding, the Non-Patent Document 2 declares that the carbide dissolution in weldingthermal cycles and reheating to the M.sub.23C.sub.6 precipitation temperature in the subsequent cycles lead to the form