Development And Application Of Steelmaking Technology For H08A Electrode Steel At Dagang

The price of constructional steel in the domestic market hits a recorded low,obvious oversupply and serious overcapacity at present.With the decline of growth rate of investment in domestic infrastructure and real estate,the domestic constructional steel market are competing fiercely for business.How to increase the added value of products and to achieve the optimization and upgrading of the company's product structure become a focused and must be addressed problem of steelmaking enterprises.Based on the existing equipmengt and raw material conditions of Dagang,the technical of vanadium liquid iron dephosphorization and liquid steel deoxidation are studied,the improvement production technics and several industrial experiments were conducted.The optimal technological outline for the steel making of H08A steel in Da Gang have been obtained:the use of KR hot metal pretreatment desulphurization to control the sulfur content of molten iron within 0.010%;the use of double slag method combined with pyrodyne reheating process in converter to control the phosphorus endpoint within 0.015%.The tapping temperature is about 1660~oC.Steelcore-aluminumwasselectedasthefinaldeoxidizerand aluminum-magnesium-calcium alloy balls as the complete deoxidizer during tapping.The LF furnace was fed with Ca-Fe wire 100-200m each heat for modification of the molten steel.Oxygen was controlled within 40ppm in the refined molten steel.Full protection was implemented during pouring at continuous casting and even the sub-tundish temperaturewas controlled at 1550~1560?.In the course of the experiment,we carried out an in-depth analysis of the difficulties in dephosphorization of vanadium-titanium hot metal and molten steel deoxidation.The main results are:(1)The treatment of double slag method combined with pyrodyne reheating process in converter can make the phosphorus within 0.015%in the product,which can completely satisfied the standards and requirements of H08A.(2)Since the content of carbon in tapping is extremely low(C?0.05%),the content of oxygen in the molten steel is high.Through the converter furnace and LF refining for deoxidation,the oxygen can be controlled within 40PPm,making sure the subcutaneous porosity of continuous casting billet was effectively controlled to meet the quality and requirements of steel rolling.The quality of H08A steel produced by this process is superior to the national standard and can meet the needs of users.