Research On Materials And Production Technology Of Heavy Section Compacted Graphite Iron Ingot Mould

Ingot mould is one of the main metallurgical moulds to produce large-scale forgings in steelworks. It endures thermal stress, phase transformation stress, residual stress and mechanical stress during its use, so it is easy to cause crack and peeling which leads to scrap. Since the compacted graphite cast iron has good thermal conductivity, high tensile strength, excellent anti-oxidation and thermal fatigue properties, the corresponding ingot mould can remarkably improve the resistance of cracking and deformation, reduce the weight and consumption of mould and increase the weight ratio of ingot mould to ingot.Hence, this research will bring about significant social and economic benefits. In this paper, for the goal of producing heavy section compacted graphite iron ingot mould, effects resulted from vermicular agents and combined technology on microstructure and performance have been investigated through simulating castings with the size of 400mm*400mm*450mm. In addition, influences brought by chill and the heat resistance of gray and graphite iron will be also studied. Meanwhile, the simulation of mold filling and solidification is conducted to meliorate the manufacture technique of ingot mould based on the software of HZ-CAE. Finally, the new vermicular agents and technology have been developed.There are four kinds of vermicularing agents including REMg, YSBM-1, YSBM-3 and YSBM-A. The research results showed that YSBM-A has the best anti-declining capability, the percentage of vermicular graphite reached 85% in block center, the tensile and elongation was 315MPa and 3.3% respectively, which meets the requirements of materials for ingot mould. The percentage of vermicular graphite has been increased from 35% to 55% in block center, the number of chunky graphite was reduced, and uniform and small grain matrix was obtained by chiller. Additionally, the heat resistance of compacted graphite iron was superior to gray iron, the average oxidation rate of which was 4.76g/m2h and it was greater than the one of compacted graphite iron 3.14g/m2h within 72 hours. The thermal fatigue life of compacted graphite iron was 42 times while the corresponding value was about 30 times under the quench in water from 700℃to ambient temperature. According to the simulation results of HZ-CAE, the optimal casting technology of mould was as following: top pour and shower gating system for 48t ingot mould was chosen, treatment temperature of compacted graphite was 1420℃and pouring temperature was 1320℃. The attached block of ingot mould had vermicular graphite rate of 85%, tensile strength 350MPa and elongation 7.5%, all of which reached the level of RuT300. 420t ingot mould had two gating systems: the upper gating system was shower gating system while the bottom one was bottom gating system. The pouring temperature was 1300℃~1320℃.