| Fixation of marine engineering platforms and equipments depends on high-level mooring chain. It is used in bad service condition which not only for a long time to withstand enormous storm waves shock, but also to withstand erosion of sea water. Whether high-level mooring chain has good integrated mechanical and chemical properties directly influence security and reliability of marine engineering platforms and equipments. The properties of the material are depended on chemical compositions and microstructures. And heat treatment is an effective measure to alter microstructures and increase comprehensive properties, under the condition of the chemical composition unchanged. So the study of microstructure and corrosion resistant on the different heatment has important theoretical significance and practical engineering applications for high-level mooring chain of 22MnCrNiMo.In this paper, the microstructure and corrosion resistant properties of as high-level mooring chain of 22MnCrNiMo in different heat treatment states, and the effect of heat treatment system on corrosion resistance and mechanical properties of high-level mooring chain of 22MnCrNiMo were studied. The impact on microstructure and corrosion resistance of high-level mooring chain of 22MnCrNiMo were investigated and analyzed systematically by OM, SEM, EDS, XRD, tests of static weight-loss, as well as tests of polarization curves, Salt spray accelerated corrosion tests and mechanical properties respectively.The results show that the microstructure of the rolled steel 22MnCrNiMo includes martensite,bainites, sorbites and a small amount of bulk ferrites.The strength is okaye of the rolled steel,but the plasticity, impact toughness and corrosion resistance is bad. After the double quenching in 910℃,930℃,950℃for 30 min,the organization is lath martensite. The organization is sorbite and troostite after the tempering for 15min,30min,45min in 600℃,620℃,640℃,and Its performance indicators were able to achieve the requirements of DNV classification society .At the same quenching, as the tempering time extended and tempering temperature rise, the strength of the sample decreased, plasticity, impact toughness and corrosion resistance increased. The results of the artificial sea water erosion test and the salt spray accelerated corrosion test is the same as the results of polarization curves after the sample with the heat treatment of double quenching in 930℃for 30min and the tempering in 600℃,620℃,640℃for 30min. Metal corrosion rate measured by weight loss method is less than 0.0102 g.-2h-1.There are all up to 4 of corrosion resistant metallic materials grade,and belong corrosion resistant materials. Even after tempering in 620℃, 640℃, the corrosion rate of the sample are respectively up to 0.0086 g.-2h-1,0.0085 g.-2h-1. There are all up to 3 of corrosion resistant metallic materials grade,and are very corrosion rtesistant. Salt spray accelerated corrosion tests showed that because of to the spread of Cl-1,and the strong ability 0f penetrate,steel surface is dotted with a number of discrete corrosion pit and groove strip. Compared with base metal,the trends that the mechanical properties and corrosion performance of the Welding is consistent.Because of the second heat and Slower cooling rate,weld regional organizations are coarse; the weld region organizations are different with surrounding areas and the organizations are uneven, Therefore both the mechanical properties or corrosion resistance of welds,are bad than base metal. Comparison of mechanical properties and corrosion resistance, we finally selected heat treatment of double quenching in 930℃for 30 min and tempering in 620℃for 30 min.
|
PDF Full Text Request