采用热力学和动力学方法研究了轴承钢GCr15凝固过程中溶质元素偏析、钛夹杂析出规律及影响钛夹杂长大的因素。研究表明:1)GCr15钢在凝固过程中Ti(C_(x)N_(1-x))先于TiN在凝固前沿的固液两相区析出,降低钢液初始Ti、N含量均能推迟Ti(C_(x...采用热力学和动力学方法研究了轴承钢GCr15凝固过程中溶质元素偏析、钛夹杂析出规律及影响钛夹杂长大的因素。研究表明:1)GCr15钢在凝固过程中Ti(C_(x)N_(1-x))先于TiN在凝固前沿的固液两相区析出,降低钢液初始Ti、N含量均能推迟Ti(C_(x)N_(1-x))在凝固前沿的析出。Ti(C_(x)N_(1-x))夹杂中的x值随w(Ti)_(0)下降而下降,但随w(N)_(0)下降而升高。2)凝固冷却速率对GCr15钢中Ti、N元素的凝固偏析影响不大,但对钛夹杂的长大影响显著。随着钢液初始Ti、N含量下降,钛夹杂凝固析出推迟,尺寸变小。采用70 t EAF→EBT→LF→RH→IC(模铸)工艺生产轴承钢GCr15大钢锭,从30 t GCr15钢锭经热锻/轧成的Ф75 mm圆棒上取样,w(T.O)、w(Ti)和w(N)分别为0.0007%、0.0010%、0.0019%。光学显微镜下检测到的钛夹杂是呈土红色的碳氮化钛夹杂;扫描电镜下观察到钢中钛夹杂形状不规则,钛夹杂最大尺寸17.4μm,平均尺寸为9.2μm,这与大吨位模铸锭冷却速率小有关。对大钢锭模铸而言,严格控制各工序钢水增Ti量和增N量,降低钢液中Ti、N含量,推迟钛夹杂在凝固过程中的析出是控制盾构机主轴承圆柱滚子用轴承钢GCr15产品钛夹杂尺寸的有效措施。展开更多
Formation and evolution of inclusions in low-aluminum Ti-containing 51CrV4 spring steel under BOF(basic oxygen furnace)–LF(ladle furnace)–CC(continuous casting)process were investigated by industrial trials and ther...Formation and evolution of inclusions in low-aluminum Ti-containing 51CrV4 spring steel under BOF(basic oxygen furnace)–LF(ladle furnace)–CC(continuous casting)process were investigated by industrial trials and thermodynamic calculations.During LF refining,deoxidation products including Al_(2)O_(3),Al_(2)O_(3)–Ti_(3)O_(5)–SiO_(2)–MnO and Al_(2)O_(3)–SiO_(2)–MnO are modified as MgO–Al_(2)O_(3),CaO–Al_(2)O_(3)–SiO_(2),CaO–Al_(2)O_(3)–MgO and CaO–Al_(2)O_(3)–SiO_(2)–MgO.When reoxidation during ladle casting is quite serious,inclusions such as Al_(2)O_(3),Al_(2)O_(3)–Ti_(3)O_(5)–SiO_(2)–MnO,and Al_(2)O_(3)–SiO_(2)–MnO may regenerate.A handful of Ti carried by alloy into liquid steel has less influence on inclusions during LF refining;Ti-containing inclusions mainly transiently exist as an intermediate product of deoxidation process and then are gradually modified by[Al],[Ca]or[Mg].Thermodynamic calculation and experimental results reveal that tundish flux is the main source of reoxidation in ladle casting process.Further calculations taking into account of the influence of inclusions before casting indicate that reoxidation within a certain of degree leads to the generation of a large amount of high melting point inclusions including CaO·2MgO·8Al_(2)O_(3),CaO·MgO·7Al_(2)O_(3),MgO·Al_(2)O_(3),CaO·6Al_(2)O_(3)and Al_(2)O_(3)in molten steel,which is basically consistent with experimental results,and more high melting point inclusions will generate as reoxidation becomes severer.On this basis,severer reoxidation will deplete[Si],[Mn],and[Ti]in steel melt,resulting in the formation of liquid inclusions composed of Al_(2)O_(3)–Ti_(3)O_(5)–SiO_(2)–MnO(–CaO).These results are of guiding significance for controlling inclusions in Al-killed Ti-containing spring steel.展开更多
文摘采用热力学和动力学方法研究了轴承钢GCr15凝固过程中溶质元素偏析、钛夹杂析出规律及影响钛夹杂长大的因素。研究表明:1)GCr15钢在凝固过程中Ti(C_(x)N_(1-x))先于TiN在凝固前沿的固液两相区析出,降低钢液初始Ti、N含量均能推迟Ti(C_(x)N_(1-x))在凝固前沿的析出。Ti(C_(x)N_(1-x))夹杂中的x值随w(Ti)_(0)下降而下降,但随w(N)_(0)下降而升高。2)凝固冷却速率对GCr15钢中Ti、N元素的凝固偏析影响不大,但对钛夹杂的长大影响显著。随着钢液初始Ti、N含量下降,钛夹杂凝固析出推迟,尺寸变小。采用70 t EAF→EBT→LF→RH→IC(模铸)工艺生产轴承钢GCr15大钢锭,从30 t GCr15钢锭经热锻/轧成的Ф75 mm圆棒上取样,w(T.O)、w(Ti)和w(N)分别为0.0007%、0.0010%、0.0019%。光学显微镜下检测到的钛夹杂是呈土红色的碳氮化钛夹杂;扫描电镜下观察到钢中钛夹杂形状不规则,钛夹杂最大尺寸17.4μm,平均尺寸为9.2μm,这与大吨位模铸锭冷却速率小有关。对大钢锭模铸而言,严格控制各工序钢水增Ti量和增N量,降低钢液中Ti、N含量,推迟钛夹杂在凝固过程中的析出是控制盾构机主轴承圆柱滚子用轴承钢GCr15产品钛夹杂尺寸的有效措施。
基金support from the project of Xinjiang Bayi Iron and Steel Co.,Ltd.(No.2022-0460).
文摘Formation and evolution of inclusions in low-aluminum Ti-containing 51CrV4 spring steel under BOF(basic oxygen furnace)–LF(ladle furnace)–CC(continuous casting)process were investigated by industrial trials and thermodynamic calculations.During LF refining,deoxidation products including Al_(2)O_(3),Al_(2)O_(3)–Ti_(3)O_(5)–SiO_(2)–MnO and Al_(2)O_(3)–SiO_(2)–MnO are modified as MgO–Al_(2)O_(3),CaO–Al_(2)O_(3)–SiO_(2),CaO–Al_(2)O_(3)–MgO and CaO–Al_(2)O_(3)–SiO_(2)–MgO.When reoxidation during ladle casting is quite serious,inclusions such as Al_(2)O_(3),Al_(2)O_(3)–Ti_(3)O_(5)–SiO_(2)–MnO,and Al_(2)O_(3)–SiO_(2)–MnO may regenerate.A handful of Ti carried by alloy into liquid steel has less influence on inclusions during LF refining;Ti-containing inclusions mainly transiently exist as an intermediate product of deoxidation process and then are gradually modified by[Al],[Ca]or[Mg].Thermodynamic calculation and experimental results reveal that tundish flux is the main source of reoxidation in ladle casting process.Further calculations taking into account of the influence of inclusions before casting indicate that reoxidation within a certain of degree leads to the generation of a large amount of high melting point inclusions including CaO·2MgO·8Al_(2)O_(3),CaO·MgO·7Al_(2)O_(3),MgO·Al_(2)O_(3),CaO·6Al_(2)O_(3)and Al_(2)O_(3)in molten steel,which is basically consistent with experimental results,and more high melting point inclusions will generate as reoxidation becomes severer.On this basis,severer reoxidation will deplete[Si],[Mn],and[Ti]in steel melt,resulting in the formation of liquid inclusions composed of Al_(2)O_(3)–Ti_(3)O_(5)–SiO_(2)–MnO(–CaO).These results are of guiding significance for controlling inclusions in Al-killed Ti-containing spring steel.
