| With the diversified development trend of marine development and the demand for material,the status of seawater corrosion resistant steel is becoming increasingly important,the traditional seawater corrosion resistant steel has been far from meeting the demand.In recent years,high strength low alloy steel with good strength,ductility,formability,low cost and other comprehensive advantages has been widely used.How to improve the corrosion resistance of low alloy high strength steel has become a hot topic in today's society.In this paper,the effects of different deoxidation methods on the corrosion resistance of low carbon high strength steel were studied by adding Al element into the low carbon high strength steel and using Zr-Ti combined deoxidation.The Al element content in Al deoxidized low alloy high strength steel was 0.024%.The Ti element content was 0.006% and the Zr element content was 0.018%.By using optical microscope and scanning electron microscope observations of different deoxidation methods,microstructure,inclusion and its size,distribution and type were analyzed.Results showed that two samples of inclusion size was not more than 8 ?m,and the size of the sample Zr-Ti deoxidized was mainly 0-5 ?m,and the size of the sample Zr-Ti deoxidized was relatively large,generally distributed in 4-7 ?m.According to the Russian GOST 9.911-89 standard,indoor simulated seawater accelerated corrosion test was carried out,the environment of which was under the tidal zone,to explore the influence of different deoxidation processes of high strength low alloy steel local corrosion resistance in seawater.Compared with Al deoxidized steel,the average corrosion rate of Zr-Ti killed was 17.27% lower than that of Al killed.Compared with the Zr-Ti combined deoxidation sample and the Al deoxidation sample,the former was more excellent in seawater corrosion resistance.In this paper,0.04%La element or the 0.08%Nb element was added in low-alloy and high strength steel.Using optical microscopy and scanning electron microscopy,the effects of different deoxidation methods on microstructure and size of inclusions,and the distribution of kinds were analyzed.The results showed that the rare earthelements and Nb elements could refine grains.The average diameter of rare earth-Al deoxidized steel was lower than the size of base steel 0.99%,and the average diameter of rare earth-Zr-Ti was lower than the size of base steel 14.71%.The results showed that the inclusion size,distribution and types of Zr-Ti combined deoxidization and low alloy with rare earth elements in high strength steel has been effectively controlled,and MnS and Al2O3 mixed inclusions were spheroidized and dispersed,which improved its local corrosion resistance.The corrosion rate of high strength low alloy steel with rare earth elements Al killed and Zr-Ti killed was lower than the base steel sample 14.26% and 29.07% respectively.The corrosion rate of high strength low alloy steel with Nb elements addition as lower than the base steel sample 11.91%.By using Zr-Ti combined deoxidation.The content of Mn of low alloy high strength steel was depleted,which reduced the thermodynamic stability of austenite,and thus promoted the nucleation of intragranular ferrite,which was beneficial to improve the corrosion resistance properties.The solid solution strengthening of Nb increased the nucleation rate of ferrite and refined grain structure.The second phase particles was formed by the precipitation of Nb and C,N atoms in austenite and ferrite grains or along the grain boundaries and sub-grain boundaries.These particles provided nucleation sites,which promoted the formation of intragranular ferrite.The addition of Nb element in low alloy high strength steel could not only enhanced the thermodynamic stability of the material,reduced the corrosion current,but also improved the corrosion resistance of the steel.Moreover,the grain size was reduced,the corrosion current density was reduced and the corrosion resistance of steel was improved. |
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