Research On Casting Procedure And Optimization For High Strength Thin Wall Gray Iron Cylinder Block

Optimization of process and structure is one of the convenient way to reduce the weight of car and also the cost of production,so thinning the wall become the key point to cylinder block weight reduction.Aiming at the requirement of thinning the gray-iron cylinder block wall in the engine of the high power and large displacement car/track,the casting procedures and relevant parameters were investigated and then optimized for reducing the gray-iron cylinder block wall thickness using the computer simulation methodology and corresponding experiments to adjust the casting temperatures.Finally,the optimized casting procedure was practically verified using the production-run equipments from FAW Foundry Co.,Ltd.Based on the simulated results form the casting procedures of grayiron cylinder-block,it was found that in the horizontal pouring scheme of cylinder block,there exists a temperature difference at different coordinate positions all through the casting duration,and the largest temperature difference reaches 180?,just locating at the wall of the camshaft wall(the thinnest part).This raised higher possibility to cause micro cracks or related defects.Comparatively,using a vertical core packing casting procedure with an U shape internal pouring gate,the simulated results indicate that the temperature difference was shown decrease,thus greastly reducing the possibility of casting defects such as shrinkage porosity and cavity,cold shut et al.Meanwhile,the solidification process is shown in accordance with the theoretical solidification sequence from thin to thick and from outside to inside,which is more suitable for the gray iron cylinder block with thinner wall thickness for weight reduction.For the vertical core packing casting procedure with an U shape internal pouring gate,there appears some possible defects due to slow solidification in specific positions from the simulated results.In that case,some specific casting-procedure simulations were conducted to obtain the optimized casting scheme and the corresponding processing parameters through analyzing the casting and solidification processes as changing the diameters of pouring gate and designing an additional internal gate near the crankshaft,et al.Hence,the optimized casting procedure and scheme could be determined according to the simulation results as :using the vetical core packing casting scheme with a W-shape internal pouring gate,this pouring gate being directly connected with the bottom flange and upper crankshaft support,the sprue diameter being set as 100 mm,and HT250 be set as the casting materials.Under the optimized procedure and corresponding key parameters,the practical production of verification scheme was carried out and the quality of samples was inspected and analyzed.The appearance of the samples was shown free of defects,the cylinder wall thickness and camshaft outer wall(which was designed the thinnest thickness)were all qualified,and the metallographic structure is reasonable.In order to study the influence of the casting temperatures on gray iron cylinder block,the pouring temperatures at 1430?,1440? and 1470? were selected for verificated experiments.The results show that the appearance of 1440? product is the best without defects,and no white iron and other microdefects were detected.However,higher pouring temperature leads to weakening the casting surface quality,while lowering the temperature would result in some casting defects as lacking meat.