Thermal Processability Of Oral Materials For Deep-Sea Oil And Gas Wells And Its Corrosion Resistance

With the continuous development and utilization of China’s marine resources,the requirements for steel for marine engineering are becoming more and more stringent.As one of the subsea wellhead devices,the wellhead head has not yet been localized due to the difficulty of production technology.Therefore,in order to quickly master this key technology and accelerate the process of localizing subsea wellhead devices,a micro-alloyed 8630 steel has been designed and characterized independently in this paper.The main research findings and conclusions are as follows:Through hot compression experiments,the thermal deformation behavior and organizational changes of the experimental steel were analyzed,and its thermal deformation activation energy（Q）and thermodynamic intrinsic equations were calculated.The processing diagrams are then drawn based on the Dynamic Materials Model（DMM）to obtain the basic parameters of plastic deformation and finally determine the thermal processing range of the experimental steel:temperature 1125–1200°C and strain rate 0.01-0.1 s^-1.Orthogonal experiments were designed to analyze the effect of each factor on the mechanical properties and microstructure of the experimental steel and to determine the optimum heat treatment process.The influence of each factor on the mechanical properties of the material in descending order is:tempering temperature,tempering time,normalizing temperature,and quenching temperature.After tempering,the metallographic structure of the experimental steel consisted of tempered sothite with a large amount of carbide precipitation.The carbides are mainly of two types as observed by TEM:one is Fe₃C in the form of rods,and the other is（Fe,Mn,Si,Cr）₃C in the form of spheres.The corrosion behavior of the experimental steel in different environments was simulated.The experimental steel exhibits uniform corrosion characteristics in different environments,but corrosion pits and craters are locally present,and carbides of different shapes are present inside the pits.In the salt spray environment,there is intergranular corrosion behavior within the specimen.The test analysis shows that the potential difference between the carbide and the matrix and the depletion of elements at the grain boundaries are the sources of the corrosion behavior of the experimental steels.The corrosion resistance and microbial corrosion behavior of Cu-AISI 8630 and AISI 8630 steels were studied in comparison.The presence of Cu in an environment containing Pseudomonas aeruginosa was found to inhibit the growth of Pseudomonas aeruginosa and to hinder the formation of microbial biofilms.Cu-AISI 8630 steel showed better resistance to microbial corrosion than AISI 8630 steel,with an inhibition efficiency of 39.7%.The presence of Cu in Cu-AISI 8630 steel allowed the Cu ions to act as a bactericide and form protective corrosion products such as Cu₂O and Cu O,resulting in improved microbial resistance of Cu-AISI 8630 steel.