Preparation Process Optimized And Quadratic Machining Of TiC_p/Fe In-situ Composites

In-situ TiCp/Fe composites were prepared by reaction cast method with induction heating, crucible smelting and covering agent. The microstructure and phase structure of the composites were investigated by means of optional microscope, XRD and SEM. The preparation process and its parameters of composites were tested systemically. The forming mechanism of TiC particles in Fe-Ti-C melt was discussed preliminarily on the condition of optimized technology. The mechanical properties of TiCp/Fe composites with different microstructure were analyzed. The machinability and welding ability of the composites were also studied .The best process parameters of preparing TiCp/Fe composites were explored by means of orthogonal design test as: C was 2.8%, Si was 1.0%, Ti was 8.0% and reaction temperature was 1650 , heat preservation time was 10 minutes. The properties of the obtained composites were: HRC was 46.8, k was 14.25J cm-2. The cast microstructure was pearlite body with diffusion TiC particles distributed on it.According to thermodynamics and dynamics analysis, the forming-nucleus ratio of TiC was higher in the interface of carbon particles. The forming-nucleus drive power could form numerous little crystal nucleus under natural melting temperature. The formation of TiC particles in the melt could be divided into two phases which was forming-nucleus and growth. The forming mechanism of TiC was: melting Ti first surrounded C, then Ti melting in the alloy and C formed a complicated reaction mesosphere on the carbon surface. C particles decreased continually and the inborn TiC melted in the Ti liquid with the reaction. The growth process of TiC particles went with the pilling up, congregation and shape regularization of them.The microstructure and properties of TiCp/Fe in situ composites could be changed obviously by different heat treatments, however the shape, dimension and quantity of the TiC reinforcement couldn't be changed. Annealing could reduce hardness and raise toughness, which could be prone to mechanical machining.Quenching and low temperature tempering could raise intensity and hardness of materials, not reduce toughness obviously. Quenching on same temperature caused TiCp/Fe in situ composites having the best integral machine properties.On the condition of the test, the cutting force of TiCp/Fe composites was morethan which of 45 steel by 60N, and the cutting temperature was higher than which of 45# steel by 90 , and the roughness of machined surface was almost as much as which of 45# steel. TiC ceramic particles enhanced the cutting force and the cutting temperature of TiCp/Fe composites, but had little effect on the roughness of machined surface. The machining quality of TiCp/Fe in situ composite was similarity to 45# steel.The welding line microstructure of TiCp/Fe in situ composites gained by different welding technologies and welding methods was different. However the microstructure was diffused on the welding line and there were no welding defects, the welding quality was better. The TiC reinforced particles on the welding line still kept the same shape as that of the casting microstructure.