| With social and economic development, there are higher and higher requirements on steel performance and on its diversification. Traditional straight carbon steel can only meet the structural needs. However, for some special industries and areas, special alloy steel gradually have more applications and higher using rates. And straight carbon steel, due to its lower corrosion resistance and mechanical property, has limited applications in daily life. High carbon content led to the corrosion is less than the ferritic and austenitic stainless steels, martensitic corrosion mechanism and it is necessary to improve its corrosion resistance properties.Because of corrosion,10%steel is lost annually. This article have studied the corrosion resistances of3Crl3,3Cr13Mo and431in Martensitic stainless steel, analyzes and summaries the influence of molybdenum on the corrosion resistance of3Crl3Martensitic stainless steel and3Cr13,3Cr13Mo and corrosion resistances of3Crl3,3Cr13Mo and431.Plasma emission spectrometer was used to determine the main chemical constituents of3Crl3,3Cr13Mo and431these three Martensitic stainless steels. And through metallographic analysis, it was known that the main organization of hot-rolled Martensitic stainless steels was a mixture of ferrite and pearlite, and hot-rolled metallurgical structure had a certain direction. And the main organization of hot-rolled Martensitic stainless steels was still a mixture of ferrite and pearlite after800℃high-temperature annealing, but their distribution was not even, and the direction was not obvious. While another set of samples had martensite organizations after being1100℃high temperature oil-quenched. This paper selected hot-rolled Martensitic stainless steels, Because after continuous casting and the following900℃hot rolling, Martensitic stainless steels’supercooling is relatively low when air cooled to room temperature, which stops the forming of martensite organizations; hot extrusion causes metal plastic deformation. Due to external forces, grains are deformed and dislocated, thus there is great stress between grains.First the hardnesses of the three samples obtained after hot-rolling, annealing and quenching of three Martensitic stainless steels were tested and analyzed. The three Martensitic stainless steels had similar vicker hardness in hot-rolled state and annealed state and the vicker hardness had decreased by10%after annealing. After high-temperature quenching, the organizations of the three stainless steels were transformed into martensite organizations and their hardness greatly increased nearly three times.3Crl3,3Cr13Mo had similar hardness after quenching. Mo had no big influence on mechanical properties of Martensitic stainless steel basically. After quenching,431had low hardness than3Cr13and3Cr13Mo because of its low carbon content.The electro-chemical corrosion resistances in hot-rolled state and annealed state were tested. In hot-rolled state,3Cr13Mo’s polarization voltage was higher than other two stainless steels, with431in the middle and3Cr13having the lowest polarization voltage. And when martensite organizations were formed after quenching, the polarization voltages all reduced, with431reduced the most. Three Martensitic stainless steels’polarization voltages went from3Cr13Mo,3Cr13to431.431had the minimum polarization current, which showed that431had the smallest corrosion resistance rate.At last, through weightlessness corrosion test, hot-rolled, annealed and quenched steels’corrosion resistance properties were tested in strong acid, strong oxidant and strong alkali. Experiment results showed431had the best performance, with3Cr13Mo being in the middle and3Cr13having the worst performance. But in specific corrosion environment and time, the three steels’ corrosion weightlessness performances had huge differences. Three stainless steels in strong oxidants had similar corrosion resistance.431has better corrosion resistance than others on acid corrosion, its corrosion-resistant performance was4-5times of that of the other two stainless steels.In a strong alkali, a protective film was formed because of the reaction of iron and OH-, which leaded to the passivation. Thus Martensitic stainless steels basically maintained the original metallic luster after corrosion.The quenching improve the corrosion resistance performance of martensitic stainless steel. By3Cr13Mo,3Cr13,431comparison,431martensitic stainless steel not only in the thermodynamic performance of corrosion electric potential is low, ie, the corrosion trend is smaller, has more advantages in dynamics, Because of the higher chromium content in the431martensitic stainless steel,431martensitic stainless steel containing a small amount of nickel austenite role play to expand, Increase the decay resistance of martensitic stainless steel. |
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