- The dual liquid lost foam casting process is proposed to produce bimetallic liner. Placing the wear-resistant cast iron at the bottom of the mold and adopting the pouring process of pouring molten iron first and then molten steel is conducive to ensuring the casting quality of the wear-resistant surface.
- Establish the mechanical model of mold collapse in bimetallic composite casting process. The key condition to avoid box collapse at the top and side of the mold during pouring or after pouring is that the whole mold provides enough P resistance (resistance per unit area when the coating layer and molding sand move). In order to ensure that no box collapse occurs in the process of bimetal liquid lost foam composite casting, in addition to increasing the vacuum pumping process measures, the thick wall (2mm-3mm) high-strength coating layer is mainly used.
- Carry out the thermal structure meshing analysis of the solidification process of bimetallic liner based on ANSYS. The results show that high temperature liquid carbon steel is poured into the solid phase high chromium cast iron, which provides the necessary temperature conditions for the formation of metallurgical bonding near the interface; During solidification, the stress concentration at the interface shall be focused, and appropriate heat treatment process shall be adopted to eliminate the residual stress and prevent the material from cracking at the joint surface; In order to ensure the dimensional accuracy of the lining plate to be installed in the ball mill smoothly, the design radius of the circular arc surface of the carbon steel layer of the lining plate shall be reduced. When the lining plate solidifies and shrinks, the radius shall be automatically increased to compensate for deformation to adapt to the installation circular arc surface in the ball mill.
- Complete the design and parameter optimization of bimetallic liquid lost foam composite casting process: the optimal combination temperature of wear-resistant cast iron and carbon steel (1210 ° C on the surface of high chromium cast iron and 1550 ° C on carbon steel) was determined through temperature operation test, the pouring temperature of molten iron was 1480 ° C, and the pouring temperature of molten steel was 1550 ° C. according to the heat transfer theoretical model of the casting process, the pouring interval between the two metals was calculated to be 75s, It is determined that the composite interface is located at 15.2mm of the lower limit of carbon steel layer thickness; The software of lost foam bimetal casting process system was developed by using c\n\e platform and access data.
- The high chromium cast iron was modified with a compound modifier composed of rare earth, calcium, silicon and a small amount of low melting point metals, and the grains were obviously refined; The morphology and distribution of carbides have been significantly improved, from fibrous chrysanthemum clusters to isolated and dispersed small blocks, and the degree of isolation has been improved and significantly refined.
- The wetting of liquid carbon steel on the surface of high chromium cast iron provides conditions for the nucleation of its composite interface. The poured liquid carbon steel reproduces the random wavy surface of high chromium cast iron, making the composite interface present a dog tooth staggered shape; The microstructure of the interface transition region is dense, without obvious shrinkage and porosity defects, and is in a good metallurgical bonding state.
- The mass transfer model in the transition region is established and the diffusion equation is solved. The theoretical calculation is consistent with the SEM results: in the composite interface transition zone, chromium, iron and carbon atoms transfer from high chromium cast iron to carbon steel for a short distance, and the diffusion law is tiller attenuation curve.
- The most important process parameter affecting the composite quality of high chromium cast iron and carbon steel bimetallic liner is the composite pouring time interval. The interval of composite pouring is too short (60s), and the two metals are miscible due to solid-phase re dissolution; If the interval of compound pouring is too long (90s), the surface of carbon steel cannot be completely melted by pouring high chromium cast iron to form mechanical compound; The pouring time interval is appropriate (75s), and the metallurgical bonding between the two metal materials is of high quality, sufficient strength and thickness.
- Compared with a single high chromium cast iron material, the mechanical properties of the bimetal composite samples have been greatly improved, with Rockwell hardness of 61hrc, impact toughness of 16.5j/cm2 and bending strength of 1600mpa. ZHY casting has successfully applied the lost foam dual liquid bimetal composite lining to production.
- After the ball mill has been operated at full load for nine months, the carbon steel high chromium cast iron bimetallic liner still retains a smooth arc transition contour, and the thickness direction is thinned evenly, still maintaining the original silver luster of high chromium; However, due to the cyclic alternating effect of impact, corrosion and wear, the surface profile of the original alloy steel lining plate becomes rough and intermittent impact peaks, and the thickness direction is thinned to only 10mm. The entire lining plate surface is completely oxidized and presents red rust color, which has been scrapped and must be replaced with a new lining plate. The comparison of the weight loss results of the liner after service shows that the relative wear resistance coefficient of the high chromium cast iron / carbon steel bimetal liner is three times that of the original alloy steel liner under the full load service condition in the wet ball mill.