Study On The Control Of Molten Steel Cleanliness For Large Forgings

Large forging is an important basic subassembly which is necessary for many national major technical equipments and projects.Because of the relation to the national economy and the people's livelihood,so the quality of large forgings is always concerned by society. Its production capacity and technology level are the important signs of a country's major technical equipment production ability. Provide a quality molten steel is the prerequisite to assure the large forging quality.So,it is an important for the study on the control of molten steel cleanliness for the large forgings.In this paper, according to geometric similarity 130t and 160t ladle models are designed by 1:5 and 1:5.5 and study by physical simulation method. Using conductivity meter, wave height meter and other lab equipments, from the mixed time, the level fluctuation, the inclusion floated time, the entrapped slag and the bar earea diameter to study the ladle. Optimizting the 130t and 160t ladles'bottom blowing argon which is met to the steel-slag interfacial reaction kinetics and inclusion removed for LF furnace, VD furnaceand VOD furance .The study obtains 130t and 160t LF refining process's bottom blowing argon ,which include heating stage, desulfurization and deoxidation under heating, desulfurization and deoxidation without heating, alloying process and soft blowing stage. The 130t, 160t VOD the bottom blowing argon during the oxygen blowing decarburization stage, deep vacuum decarburization stage and reduction stage has got.And the the bottom blowing argon under degassing,deep desulfurization and inclusion removal for the VD furance also has been designed. The results has been use to the production of ultrapure rotor steel for CHFI and the molten steel's cleanliness is met the quality requirement.According to mass balance principle ,combining with metallurgical thermodynamics and dynamics theory, a VOD decarburization control mathemtical model is set up. Through practical application in production,indicating that the decarburization control mathematics model can realize availability forcast and control for the oxygen blowing amount, oxygen blowing time, carbon end content,and the carbon hit rate over 95%, preventing molten steel peroxide. With the aforementioned study on argon system, under an adequate desulfurization slag interface kinetics condition,the production of ultra-low carbon stainless steel has achieved by EAF-VOD-VCD.