为了降低钢的T[O]含量和生成较低熔点的非金属夹杂物以改善合金结构钢的抗疲劳破坏性能,在炉外精炼中采用了高碱度和高Al2O3含量的渣系.研究发现LF和RH精炼结束时钢液T[O]含量均随炉渣碱度增加而降低,在炉渣Al2O3含量低于25%时,T[O]随炉渣Al2O3含量减少而降低,而当炉渣Al2O3超过25%后,T[O]则随炉渣Al2O3含量增加而降低.精炼过程钢液中夹杂物按"Al2O3系夹杂物→MgO-Al2O3系夹杂物→CaO-MgO-Al2O3系夹杂物"顺序发生转变,其中MgO-Al2O3系夹杂物向CaO-MgO-Al2O3系夹杂物的转变是由外向内逐步进行的,转变速度相对较慢,因而致使LF结束时钢中仍存在许多尚未转变的Mgo-Al2O3系夹杂物.钢液T[O]对夹杂物转变有显著影响,降低T[O]含量有利于生成较低熔点的CaO-MgO-Al2O3系夹杂物.
Slag of high basicity and high Al2O3 content was used in secondary refining of alloyed structur-al steels aiming at decreasing total oxygen contents (T[O] ) of steel and forming relatively lower melting point inclusions to improve the anti-fatigue properties of the steels. It was found that T[O] at the end of LF and RH refining both decreased with the increase of slag basicity. When Al2O3 in the slag was less than 25%, T[O] decreased with the decrease of Al2O3 content of slag. While, when Al2O3 in the slag was more than 25% , T[O] decreased with the increase of Al2O3 content of slag. In the refining, compo-sitions of the non-metallic inclusions changed in order of "inclusions of Al2O3→ inclusions of MgO-Al2O3 system→inclusions of CaO-MgO-Al2O3 system", among which, the change of inclusions of MgO-Al2O3 system to was inwardly from outside surface and the reaction speed was relatively slower. Thus, at the end of the ladle furnace refining ( LF), there were still many unchanged MgO-Al2O3 system inclusions. The T[O] content of the steels significantly affects the composition change of the inclusions and decrea-sing T[O] content could help obtain inclusions of CaO-MgO-Al2O3 system with low melting point.
参考文献
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