Study On Cutting Tool Matching And Cutting Performance Of Alloy Cast Iron For Diesel Engine Cylinder Head

Since diesel engine is known with good dynamic, high thermal efficiency and energy saving, it has been widely used in agricultural machinery, engineering machinery, ship machinery, automobile industry, power industry and other fields. The cylinder head, as one of the key components of the engine box which is featured with the multi porous system with the properties of complicated structure and high machining precision. In order to meet the increasing performance requirements for diesel engine, alloy cast iron materials added with alloy elements of Cu, Cr are used for WP10 diesel engine cylinder cover, which can improve the mechanical properties of the cylinder head. However, adding alloy elements to cast iron would cause decreasing of mechanical properties, serious tool wear, and then affect the processing efficiency and processing cost. Therefore, it is necessary to research the cutting performance of the material and select appropriate tool material. Moreover, that is an effective method for prolonging tool life, reducing processing cost, and improving processing efficiency.In this paper, the matching problem of alloy cast iron material used in cylinder head and hard alloy coating tool and the cutting property of alloy cast iron were studied, the main research contents are shown as following:(1) The chemical matching relationship between cemented carbide materials and alloy cast iron was studied. Prediction of oxidation products of tool material and workpiece material was conducted by chemical thermodynamic calculation. Through the XRD analysis of the products of high temperature oxidation test, the oxidation products of cutting tool material and workpiece material were compared with the prediction. The oxidation resistance of various grades of cemented carbide tools was researched by oxidation weight addition of materials:Fine grain YG3X, YG6X, YG6A and YG8 with high content of Co were found to have better antioxidant properties. The antioxidant property of YT tool is better than that of YG tool. The diffusion degree of different grades of carbide tool material and alloy cast iron was studied by element diffusion test, and the effect of temperature on the diffusion of elements was studied. The diffusion of YG3X, YG6X and YG6A with fine grains is weak, and the temperature has a great influence on the diffusion of elements. It was found that he higher the temperature, the more intense the diffusion.(1) The matches of chemical, mechanical and physical properties between cemented carbide materials and alloy cast iron were studied, and then, coating material fitting for alloy cast iron machining was analyzed and selected. For chemical properties, cutting tools with fine grains is suitable for the process of alloy cast iron because of excellent antioxidant and antiproliferation ability.For physical and mechanical properties, YT tool is not suitable for the process of alloy cast iron because of poor toughness. YG8 tool has good flexural strength and impact toughness, which is suitable for rough machining of cast iron alloy. YG3 and YG3X tools with the performance of high hardness, red hardness, and elastic modulus, little expansion coefficient, good thermal conductivity, good resistance to thermal shock property are well suited to the finish machining of cast iron alloy. YG6A and YG6X tools can be wildly applied in roughing, semi finishing and intensive processing of alloy cast iron because of good comprehensive properties. For alloy cast iron milling, TiC and Ti(C, N) coatings are always used as the bottom of multi-layer coating, tin coating, Al2O3 coating suitable for multi-layer coating layer or the middle surface.(2) Through the orthogonal experiment, the influence law of cutting parameters on cutting force and surface roughness in the milling process of alloy cast iron using the uncoated cemented carbide cutting tools and coating cemented carbide cutting tools were studied. Also the empirical prediction model of cutting force was established. And the tool wear conditions of two kinds of cutting tools under the same parameters were compared. The cutting forces all increase along with the increase of cutting speed, feed rate and the axial and radial cutting depth. The increase of cutting speed leads the increase of surface roughness of the two kinds of cutter while the increase of cutting depth and cutting force has a different degree of increasing. When the cutting speed with two kinds of cutting tool increases, the workpiece surface roughness reduced. However when the axial cutting depth, feed and the radial cutting depth with two kinds of cutting tool increase, surface roughness increases. With the same cutting condition, the coated tools have higher knives’ service life than those not coated.(3) The wear, fracture morphology and mechanism of coated carbide tools in milling of alloy cast iron were analyzed. Coating breakage, wear on the rake face, flank face, fatigue crack of tool, chipping edge of the cutting tool matrix material are the main types of tool wear morphologies. Coating breakage, adhesive wear and fatigue crack of tool are the main reason for the failure of the tool.