Refining slag for ultra-pure steel and preparation method thereof

Abstract

The invention relates a refining slag and a preparing method for a super pure steel, characterized in that the raw material lime comprises: CaO>=93%, SiO2<=2%, TiO2<=100ppm; the aluminum base materials are calcined alumina and / or industrial alumina and / or fused alumina containing Al2O3>=99.5%, TiO2<= 50ppm; the obtained refining slag comprises the following: 45-59 wt% of CaO, 40-50 wt% of Al2O3, 1-5 wt% of SiO2, wherein TiO2<=50ppm, N <=200ppm, (B+Pb)<=100ppm, (S+P)<=200ppm. Thus in the refining slag the undesired impurity and harmful elements content are low, which meets the requirement of super pure steel. And petroleum coke air-retaining agent and barium carbonate slag modifier are also added, which effectively reduces the melting point of the high pure refining slag, quickens the melting speed, has quick slag melting and long gas evolution as well as good foaming effect, and improves the sulfur and phosphor specific capacity of the refining slag. The refining slag is a new refining slag for smelting the super pure steel, the bearing steel and autocar steel after test run have qualified rate more than 98%, wherein the bearing steel has the detection qualified rate more than 90% according to national SKF standard.

Description

technical field [0001] The invention relates to a refining slag for ultra-pure steel and a preparation method thereof. Background technique [0002] Ultra-pure steel has extremely strict requirements on purity, and the content of unwanted impurities must be strictly controlled. For example, SKF bearing steel requires that N, Ti, As, Sn, and Pb should be controlled to be less than 0.003%, 0.0015%, 0.04%, 0.03%, and 0.0002%, respectively. %, [H]<1.0ppm; X60~100 series oil pipeline steel requirements: [S]<0.001%, T[O]+[S]+[P]+[N]+[H]≤90ppm. In addition to the purification of smelting raw materials, ultra-pure steel smelting also adopts various refining methods to further reduce harmful elements and inclusions. The refining process goal is mainly achieved through refining slag, so the impurities in refining slag must be strictly controlled. If the refining slag itself has impurities And the high content of harmful elements will not only fail to achieve the purpose of refi...

AI Technical Summary

Problems solved by technology

[0012] Various CaO-Al mentioned above 2 o 3 -SiO 2 It is refining slag, only for CaO and Al 2 o 3 , SiO 2 , MgO, etc. are limited, and there are basically no special restrictions on other impurities, so the unwanted harmful element impurities (such as Ti, Na, H, N, Pb, B, Pb) is not particularly limited, for example, aluminum slag contains K, Na compounds, usually SiO in alumina 2 Content above 6%, TiO 2 The content is more than 3%, S and P are also high, fluorite not only erodes the lining, but also has harmful F-, witherite contains high impurities of sulfur, silicon, and iron oxide, and the binder contains hydrogen, sodium, crystal water, etc. Harmful ingredients, resulting in low purity of the obtained refining slag itself, TiO 2 , CaF 2 、Na 2 CO 3 , H, N and other harmful components are high, and become the source of inclusions and harmful elements in ultra-pure steel, such as TiO in refining slag 2 >100ppm, it will cause the refined bearing steel [Ti] to exceed the standard

Therefore, the above refining slags are not suitable for ultra-pure steel refining

Moreover, the preparation of the above-mentioned refining slag cannot reduce or remove the harmful components in the raw materials, and even lead to the increase of harmful components, such as the use of binders for pelletizing