低碳铝脱氧20钢钢水洁净度控制研究

Study on Cleanliness Controlling of Liquid of Low Carbon Al-killed 0.20 C Steel

为了研究120 t BOF-LF-RH-160 mm×160 mm坯CC工艺生产的铝脱氧20钢(/%:0.13-0.23C,0.17~0.37Si,0.35~0.65Mn,≤0.035P,≤0.035S,0.020~0.050Al)中非金属夹杂物的控制技术,对LF精炼过程中脱氧剂加入时机进行调整,并对精炼过程中非金属夹杂物类型与夹杂物数量进行分析。结果表明,转炉出钢后采用铝块脱氧,LF精炼进站非金属夹杂物主要为Al_(2)O_(3),精炼结束前部分夹杂物由Al_(2)O_(3)转变为Al_(2)O_(3)·CaO,RH结束后非金属夹杂物密度3~4个/mm^(2),铸坯氧含量(7.48-8.18)×10^(-6);而转炉出钢后采用硅锰进行脱氧,精炼结束前采用铝线,精炼过程中夹杂物主要为MnO·SiO_(2),CaO含量小于5%,精炼结束非金属夹杂物控制为Al_(2)O_(3),RH真空处理后,非金属夹杂物密度小于1.5个/mm^(2),铸坯氧含量(4.94~5.53)×10^(-6)。因此,针对采用"BOF-LF-RH-CC"工艺流程生产的含铝钢,提出精炼结束前将非金属夹杂物控制为Al_(2)O_(3),同时运用RH真空高效去除夹杂物,以提高钢水的洁净度。

In order to study the control technology of nonmetallic inclusions in aluminum deoxidized 0.20 C steel(/%:0.13~0.23C,0.17~0.37Si,0.35~0.65Mn,≤0.035P,≤0.035S,0.020~0.050Al)produced by the process of "120 t BOF-LF-RH-160 mm×160 mm billet CC",the adding time of deoxidizer in LF refining process is adjusted,and the type and quantity of nonmetallic inclusions in the refining process are analyzed.The results show that the non-metallic inclusions in steel before LF refining are mainly Al_(2)O_(3)with deoxidizing by aluminum block after BOF tapping,and some inclusions change from Al_(2)O_(3)to Al_(2)O_(3)·CaO before LF refining,and the density of non-metallic inclusions is 3〜4/mm^(2)after RH,and billet oxygen content is(7.48-8.18)×10^(-6),But with liquid deoxidizing by silicon-manganese alter BOF tapping,feeding aluminum wire before refining end,the inclusion in refining process is mainly MnO·SiO_(2),and the CaO content is less than 5%,billet oxygen content is(4.94~5.53)×10^(-6),and the non-metallic inclusion is controlled to Al_(2)O_(3)at the end of refining,and after RH vacuum treatment,the density of non-metallic inclusion is less than 1.5/mm^(2).Therefore,for the aluminum-containing steel produced by the "BOF-LF-RH-CC" process,it is proposed to control the nonmetallic inclusions to Al_(2)O_(3)before the end of refining,and at the same time,RH vacuum is used to remove the inclusions efficiently,so as to improve the cleanliness of molten steel.