Effect of calcium treatment on inclusions of high strength machinery steel of Lianyuan Steel Company
The evolution mechanism of inclusions in LG600/LG700XL engineering machinery high strength steel during steelmaking was analyzed,and the effects of refining slag and calcium treatment on inclusion and steel cleanliness were researched.The results showed that the inclusion evolution route through calcium treatment.was Al2O3→MgO-Al2O3→Al2O3-CaO,and the inclusions in liquid steel in tundish were mainly the complex oxides of Al2O3-CaO and Al2O3-TiOx.The mass fraction of oxygen decreased from 16 x 10-6 to 11 × 10-6 when calcium treatment was cancelled.Inclusions of steel product through the two production processes were both mainly complex inclusions of aluminate as core and TiN as outer layer,while the core of inclusion with the process of calcium treatment was Al2O3-CaO-CaS and without calcium treatment was MgO-Al2O3.The sizes of these complex inclusions were all small (＜ 10 μmn),which had limited impact on steel quality.The steel castability after cancelling calcium treatment was the same as before on the whole and there was no nozzle clogging,which indicated that cancelling calcium treatment in refining was feasible for engineering machinery high strength steel in LY Steel.
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