Research on Large Inclusion Behavior of Carbon Structural Steel before Steel Slag Modified
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摘要: 通过夹杂物示踪等试验对北方某钢厂两种低成本碳素结构钢Q235D的大型夹杂物含量、种类、粒径、来源等进行了系统研究。结果表明:120 t转炉—CC工艺,稳态铸坯中T[O]平均含量为76×10-6、[N]平均含量为28×10-6、10 kg铸坯中大型夹杂物含量为31.3 mg;混浇坯T[O]平均含量为82×10-6、[N]平均含量为30×10-6、10 kg铸坯中大型夹杂物含量为38.8 mg。只含钢包渣示踪剂的夹杂物约占5%,只含中间包渣示踪剂的夹杂物约占22%,同时含钢包渣、中间包渣两种示踪剂的约占27%。120 t转炉—钢包渣改质处理—CC工艺,出钢温度较原工艺高15℃,5 kg/t改质剂、5 kg/t石灰随脱氧剂同时加入钢包,并大搅至出钢结束,盖上钢包盖后静吹12 min,然后静置20 min送至连铸。典型钢包终渣成分:43% Ca O,36% Al2O3,10% Si O2,6% Mg O,5%(MnO+FeO)。改质处理后钢中T[O]及大型夹杂含量均大幅降低,钢包顶渣改质剂的加入明显增强了钢渣对大型夹杂物的吸附能力,能做到一个浇次30炉不堵水口,改质处理作用显著。Abstract: The content,type,size and origin of large inclusions in two kinds of low cost carbon structural steel Q235 D in a steel factory in north China were studied systematically by inclusion tracing.The results shows: 120 tons BOF—CC process,the average content of T[O]in steady casting billets is 76×10-6,and the average content of [N]is 28×10-6,the content of large inclusions in the steady billets is 31.3 mg/10 kg; The average content of T[O]in mixed casting billet is 82×10-6,and the average content of [N]is 30×10-6,the content of large inclusions in the mixed casting billet is 38.8 mg/10 kg.Inclusions containing only slag tracer in ladle were about 5 %,containing only about 22 % of inclusions in tundish slag,and 27% of two tracers including ladle slag and tundish slag.120 tons BOF—ladle slag modification—CC process,The tapping temperature of this process is 15 ℃ higher than that of the original process,5 kg/t ladle slag modifier and 5 kg/t lime adding ladle with deoxidizer,and stir until the end of tapping,then blowing quietly 12 min and static 20 min after cover the ladle lip,and delivery to the continuous casting.Typical final slag composition of ladle: 43% CaO,36% Al2O3,9% SiO2,6% Mg O,5%( Mn O+Fe O).After the modification,the content of T[O]and large inclusions in the steel decreased greatly.The addition of ladle top slag modifier increases the adsorption capacity of steel slag to large inclusions significantly.It can achieve that have no nozzle clogging in 30 times pouring cycle,and the effect of modification treatment is obvious.
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Key words:
- carbon structural steel /
- ladle slag modification /
- large inclusions
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