A low-carbon,low-cost,and high-efficient method was reported for remarkably improving corrosion resistance of C–Mn structural steel by weak deoxidation.The results showed that,with the total oxygen content(wOT)increa...A low-carbon,low-cost,and high-efficient method was reported for remarkably improving corrosion resistance of C–Mn structural steel by weak deoxidation.The results showed that,with the total oxygen content(wOT)increasing in the tested steel from 41×10^(−6)to 195×10^(−6),both the degree of element segregation and the level of banded microstructure weakened,presenting the lower potential difference between pearlite(P)and ferrite(F),and then smaller galvanic corrosion driving force,and thus effectively improving general corrosion properties.In addition,with wOT growing up,the number and size of inclusions increased,and the shape also changed from long chain or small particle to large particle ball with typical mosaic structure,which could effectively inhibit the preferential dissolution of local component due to multiple complex interfaces,and correspondingly suppress the pitting susceptibility.However,the impact toughness at low temperature of the tested steel reduced with wOT increasing,and then,taking the mechanical properties and corrosion resistance all into account,160×10^(−6) was the optimal oxygen content within the present scope.展开更多
Alloying structural steel used for mechanical structures has a high requirement for cleanliness because its failures are greatly affected by non-metallic inclusions and total oxygen content in steel.It has been report...Alloying structural steel used for mechanical structures has a high requirement for cleanliness because its failures are greatly affected by non-metallic inclusions and total oxygen content in steel.It has been reported by some steelmaking plants to have some problems in controlling total oxygen content and inclusions during alloying structural steel production.For this purpose,cleanliness control in 0.2C-0.3Si-0.6Mn-1Cr-0.2Mo steel was investigated.Firstly,low melting temperature zone（≤1873 K） of CaO-Al2O3-MgO system and formation condition of low melting temperature inclusions were investigated through thermodynamic equilibrium calculation.On this basis,industrial tests were carried out.Through sampling at different stages,transformation of oxide inclusions and change of total oxygen content in steel were studied.The results show that：in order to form CaO-Al2O3-MgO system inclusions with low melting temperature,mass percent of Al2O3,MgO and CaO in inclusions should be controlled from 37.6% to 70.8%,0 to 17.4% and 25.5% to 60.6%;For the condition of 1873 K and 0.05%（mass percent） dissolved aluminum in steel,the activities of dissolved oxygen,magnesium and calcium should be controlled as 0.298×10-4-2×10-4,0.1×10-5-40×10-5 and 0.8×10-8-180×10-8 respectively.With secondary refining proceeding,average total oxygen content and inclusion amount decrease,the type of most inclusions changes from Al2O3 after tapping to Al2O3-MgO after top slag is formed during ladle furnace refining and finally to CaO-Al2O3-MgO after RH treatment.In the final products,average total oxygen content was 12.7×10-6 and most inclusions were in spherical shape with size less than 5 μm.展开更多
基金supported by the National Natural Science Foundation of China(No.U21A20113)the Natural Science Foundation of Hubei Province of China(No.2021CFA023).
文摘A low-carbon,low-cost,and high-efficient method was reported for remarkably improving corrosion resistance of C–Mn structural steel by weak deoxidation.The results showed that,with the total oxygen content(wOT)increasing in the tested steel from 41×10^(−6)to 195×10^(−6),both the degree of element segregation and the level of banded microstructure weakened,presenting the lower potential difference between pearlite(P)and ferrite(F),and then smaller galvanic corrosion driving force,and thus effectively improving general corrosion properties.In addition,with wOT growing up,the number and size of inclusions increased,and the shape also changed from long chain or small particle to large particle ball with typical mosaic structure,which could effectively inhibit the preferential dissolution of local component due to multiple complex interfaces,and correspondingly suppress the pitting susceptibility.However,the impact toughness at low temperature of the tested steel reduced with wOT increasing,and then,taking the mechanical properties and corrosion resistance all into account,160×10^(−6) was the optimal oxygen content within the present scope.
基金Item Sponsored by National Basic Research Program of China(2010CB630806)
文摘Alloying structural steel used for mechanical structures has a high requirement for cleanliness because its failures are greatly affected by non-metallic inclusions and total oxygen content in steel.It has been reported by some steelmaking plants to have some problems in controlling total oxygen content and inclusions during alloying structural steel production.For this purpose,cleanliness control in 0.2C-0.3Si-0.6Mn-1Cr-0.2Mo steel was investigated.Firstly,low melting temperature zone（≤1873 K） of CaO-Al2O3-MgO system and formation condition of low melting temperature inclusions were investigated through thermodynamic equilibrium calculation.On this basis,industrial tests were carried out.Through sampling at different stages,transformation of oxide inclusions and change of total oxygen content in steel were studied.The results show that：in order to form CaO-Al2O3-MgO system inclusions with low melting temperature,mass percent of Al2O3,MgO and CaO in inclusions should be controlled from 37.6% to 70.8%,0 to 17.4% and 25.5% to 60.6%;For the condition of 1873 K and 0.05%（mass percent） dissolved aluminum in steel,the activities of dissolved oxygen,magnesium and calcium should be controlled as 0.298×10-4-2×10-4,0.1×10-5-40×10-5 and 0.8×10-8-180×10-8 respectively.With secondary refining proceeding,average total oxygen content and inclusion amount decrease,the type of most inclusions changes from Al2O3 after tapping to Al2O3-MgO after top slag is formed during ladle furnace refining and finally to CaO-Al2O3-MgO after RH treatment.In the final products,average total oxygen content was 12.7×10-6 and most inclusions were in spherical shape with size less than 5 μm.
