Study On Element Migration During Electroslag Remelting Of H13 Die Steel

H13 steel is C-Cr-Mo-Si-V martensitic die steel with good thermal fatigue performance,high toughness and thermal crack resistance.It is widely used in many important fields,such as electric,power and machinery manufacturing.In order to obtain high cleanliness,uniformity and density of H13 die steel,the electroslag remelting process(ESR)is generally used.However,there exists many problems such as the continuity and quantification of adding deoxidizer and the imperfect protective atmosphere parameters in the process of ESR,which leads to uneven distribution of content of[Al]and[Si]along the ingot axis.And even these problems affect the metallurgical properties of H13 die steel to a certain extent.Therefore,controlling the distribution of[Al]and[Si]elements during the ESR process is of great significance for improving the properties of H13 die steel.In this thesis,a five-element slag system CaF₂-Ca O-Al₂O₃-Fe O-Si O₂is selected,and the thermodynamic model of the burning and loss of elements in the CaF₂-Ca O-Al₂O₃-Fe O-Si O₂five-element slag system is established by using the coexistence theory of molecules and ions.Based on the thermodynamic model,the change law of the various components of the molten slag on the[Al]and[Si]elements of H13 die steel is studied.The change law between the amount of deoxidizer oxidized by air and the oxidation time is explored.A deoxidation model for the proportion of deoxidizer per ton of steel in the H13 die steel during slag-gold reaction process is established.The change rule of deoxidizer Al tonnage ratio of steel was studied.The research results show that the functional relationship between equilibrium w[Al]and equilibrium w[Si]obtained by thermodynamic calculation is:w[Si](28)20.7057w[Al]^4/3.When w[Si]in the electrode is 0.97%and w[Al]is 0.014%,the Gibbs free energy of reaction between[Si]and(Al₂O₃)is-11 KJ/mol,and Si participates in the reduction reaction of Al₂O₃.The reaction can proceed spontaneously.The relationship between the oxidation amount of Al and the oxidation time is,when aluminum ball with diameter of 8 mm,under 1873 K.When the percentage of deoxidizer Al increased from 0 to 0.1%per ton of steel,the mass fractions of w[Al]and w[Si]increased by 0.051%and 0.88%,respectively.According to the composition requirements of H13 die steel,it is concluded that the deoxidizer Al accounts for 0.08%to 0.1%per ton steel under certain conditions of slag system.