A Study Of The Stress Corrosion Fracture In The Replacement Of Centrifuge With Drum Austenitic Stainless Steel

Austenitic stainless steel has strong corrosion resistance,good weldability,toughness and other excellent features.Owing to its low price,good corrosion resistance,and the wide temperature adaptability,Austenitic stainless steel can be used in fresh water environment,sea water environment and acidic environment.The paper aims to study the accidents occurred in the replacement of centrifuge with drum austenitic stainless steel.This paper analyzes the residual stress on the surface of austenitic stainless steel from the test of mechanical properties,the observation of the structure of the structure,the elimination of the residual stress by heat treatment and the mechanism of controlling the corrosion mechanism of chloride ions on the stainless steel in the recycle.Besides the cause of circumferential cracks and drum cylinder fragments will be discussed from several aspects,thus putting forward the rationalization of the proposal to avoid the appearance of similar accidents.The main research directions and results of this paper are as follows:1.Through the mechanical mechanical properties of the test,and the results of the analysis,it can be concluded that the Cr and Ni contents in the chemical composition of the cylinder material do not reach the standard value,but it is very close.From the analysis of the mechanical properties,the comprehensive mechanical properties of the material are good and are typical of the plastic material.This kind of material still belongs to austenitic stainless steel,and is said to be close to 301 stainless steel,rather than requiring the use of 304 stainless steel.2.Metallographic analysis confirmed that the surface of Ni was significantly reduced from the results of debris test,and the Ni content had a great effect on stress corrosion.The same stress corrosion would first reduce the concentration of Ni,which was in accordance with the characteristics of stress corrosion.By further observation,the secondary cracks and surface corrosion pits can still be seen in the specific part.The corrosion resistance "301" stainless steel provided by some company in some corrosive media,is not enough.It is recommended to use molybdenum austenitic steel(Example0Cr18Ni12Mo2)or more excellent duplex stainless steel such as 00Cr22Ni5Mo3 N under the premise of considering economic cost.3.For the study of residual stress of 304 stainless steel,the residual stress of the stainless steel profile was measured by X-ray diffraction.In the cold forming process,the outer surface of the stainless steel drum has a large residual tensile stress,which is the main reason for the stress corrosion cracking of the drum in the practical application.4.Study on stress-induced heat treatment.First,the residual stress of 304 stainless steel is different from that of stress treatment.The residual stress of stainless steel is changed to compressive stress after heat treatment,and the stress value is reduced.This is very useful for improving the stress corrosion resistance of stainless steel.5.By studying the mechanism of Cl~-control and corrosion of stainless steel in the recycle material,we can analyze that the contents of the centrifuge contain oxygen and sulfate ions.Stress corrosion of the media caused by this material should be avoided to the most extent.