High Temperature Mechanical Properties Of Slag For ESR Withdrawing

Electroslag remelting withdrawing technology（ESRW） has a series of advantages compared with the traditional electroslag remelting, but it is limited to be further promoted because the slag and steel leakage problems can’t be controlled in ESRW ingot production. The slag and steel leakage problems are attributed to the slag shell fracture by the moving mold, which covers on the surface of the steel ingot. Therefore, the key of the slag shell broken is related to high temperature mechanical performance of ESRW slag series. There is no relative movement between ingot and mold in traditional electroslag remelting（ESR）. The ESR slag does not apply to ESRW because the high temperature mechanical properties of slag have no chance to be choosen as slag series of evaluation index. Therefore, it is necessary to study the high temperature mechanical properties of slag to choose a suitable slag system for the ESRW.In this paper, the high temperature slag shell flexural strength experiment was designed for testing the high temperature mechanical properties of three typical ESRW slag series（1^﹟,2^﹟,3^﹟）, the thermal expansion was tested for change volume of three kinds slag series. Comprehensive analysis of the influence of high temperature mechanical properties, such as the slag shell structure, composition of slag system, and the formation of the slag shell volume changes on the ESRW slag series was conducted. The experimental results show that the three kinds of slag shell strength are concerned with mineral constituents and distribution of shell. High melting point, hardness mineral phase dispersion distribution was beneficial to improve the slag shell strength. 1^﹟ slag series slag shell mineral structure of fluorite + long strip corundum + calcium hexa-aluminate. Fluorite which have lower melting point accounting for most of organizations are not conducive to slag series of high temperature strength. Long strips of corundum in all directions make organization throughout distribution irregular and lead to stress concentration, which is adverse to the intensity of slag shell; 2^﹟ slag series slag shell for fluorite + spinelle +(Ca₁₂Al₁₄O₃₃). High hardness small of spinel diffuse distribution in the entire organization, it is not easy to cause stress concentration and increase the high temperature strength and slag for ESRW. 3^﹟ in contrast with 1^﹟ slag series increased the content of CaO and decreased the content of Al₂O₃, so the intensity trend along with the change of temperature has a certain decline. With the content of SiO₂ increasing in 2^﹟slag, the other mineral are inhibited from aggregation and growing up, which is advantageous to the mineral phase distribution uniformity and the high temperature strength which is in favor of slag series.1^﹟slag series slag shell heat expansion rate is greater than 2^﹟and 3^﹟slag series,2^﹟slag volume change rate with the temperature is close to 3^﹟ slag. The higher thermal expansion rate for slag,the larger slag shell volume shrinkage in the process of slag solidification.The air gap between the crystallizer would increase and upward stretch. The slag skin is prone to fracture in ESRW production.