Study On Temperature Field Simulation And Microstructure And Properties Of Composite Casting Interface Of Gray Cast Iron / Carbon Steel

Castings are the basic components of the equipment manufacturing industry. With the development of industry, the quality and performance of casting is proposed more stringent requirements. A single material or alloy has been difficult to meet the demand of modern production of the material. Double metal composite materials have excellent properties of two kinds of materials, the problem can be solved. The formation conditions and the organization of the Grey cast iron / steel bimetal composite material is studied in this paper. The purpose is to provide the theoretical basis of low cost, simple process model of metal and to control the gray casting solidification behavior.The virtual temperature points were set on the different position of the gray cast iron /carbon steel interface by the casting simulation software and the different casting parameters were changed, the temperature curve of each virtual point was obtained. Effects of different parameters on the gray cast iron / carbon steel fusion layer were analyzed. The critical parameters of Grey cast iron / steel fusion interface were obtained according to the formula which was gotten by the heat exchange law. Grey cast iron / carbon steel composite materials were gotten under different conditions. The mechanism of fusion layer was analyzed with iron carbon phase diagram and the element diffusion mechanism.Grey cast iron / carbon steel volume ratio has a certain influence to the formation of double metal composite material. Pouring temperature was the 1400℃ and the initial temperature of steel bars was 20℃. When the volume ratio was 3:1, the basic demands for the occurrence of metallurgical binding weren’t gotten. When the volume ratio was 8:1 and the volume ratio was 15:1, The basic demands for the occurrence of metallurgical binding were gotten.The heat transfer of sand has a certain influence to the formation of double metal composite material, Pouring temperature was the 1400℃ and the initial temperature of steel bars was 20℃. When the volume ratio was 3:1, the basic demands for the occurrence of metallurgical binding weren’t gotten. When the volume ratio was 8:1, the position of 50 mm away from the steel rod core head got. When the volume ratio was 15:1, the basic demands for the occurrence of metallurgical binding were gotten on 10 mm away from the steel rod core head.The pouring temperature of gray cast iron has a certain influence to the formation of double metal composite material. The initial temperature of steel bars remains 20℃ unchanged and the pouring temperature were changed as 1400 ℃, 1450 ℃ and 1500 ℃. When the volume ratio was 3:1, The basic demands for the occurrence of metallurgical binding weren’t gotten. When the volume ratio was 8:1 and the volume ratio was 15:1, Carbon diffusing time and the highest balance temperature were improved.Formula was gotten by the heat exchange law, when the pouring temperatures were 1400℃、1450 ℃ and 1500 ℃ and the mass ratios were less than 4.0:1、3.4:1、2.9:1,the grey cast iron/carbon steel metallurgy combination couldn’t be gotten. With the increases of grey cast iron/ carbon steel mass ratio, the affect of gray cast pouring temperature iron to the interface balance temperature was bigger and grey cast iron / carbon steel bimetal was more easy to obtain.Microstructure of specimens was studied, the results show: Grey cast iron / steel bimetal interface was diffusion bonding, the carbon element was diffused from Grey cast iron to carbon steel. Through the observation of optical microscope and electron microscope, two different tissue interfaces was formed. The interfaces were respectively transition and aggregation layer. The organization of transition layer is abnormal ledeburite, Diffusion layer organization was consist of pearlite and cementite. With the decreases of grey cast iron / steel rod volume ratio, the transition layer and diffusion layer thickness decreased linearly. The tissue thickness of transition layer was dropped from 260.029 μm to 234.132 μm. The tissue thickness of the diffusion layer was dropped from 736.255 μm to 604.773 μm.The micro hardness test of Grey cast iron / steel interface showed that the hardness of transition layer was the highest, up to 297 HV. With the increase of diffusion distance, the micro hardness of Diffusion layer decreased linearly, dropped from 240 HV to 187 HV. But it was still higher than the micro hardness of steel bar.According to the results of experiments and theoretical analysis, if the time of Steel bar and iron liquid drops to the temperature of solidification is longer than time of the fusion forming required carbon absorption, The fusion can happen.