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Cylinder block, cylinder head, gear house and fly wheel castings are the main products. The quality of all the castings is stable, but there are some problems that need to be improved. Leakage, sand inclusion, air hole, damage, slag inclusion, are the mostly defects of cylinder block, and leakage is the important one. The average leakage defect rate is 1.05%, which is the mostly of cylinder block defect rate 1.83%. Leakage can be only found in machining process, so the defect loss is huge.In this paper, the different leakage defect on different positions of cylinder block is studied. With the help of Pro cast software, the causes of cylinder block leakage are found, which are inclusions, shrinkage porosity of tapper hole and joint flash. According to cupola and furnace duplex melting technology, addition of steel crack, temperature of blast heating, blast rate and tapping temperature are researched. The results show that when addition of steel crack is 60-67.5%, and tapping temperature is 1500℃, are the optimal melting technology.According to pouring system, design of filter, size of pouring running channel, layout of inside pouring running channel are studied. Collecting slag and feeding capability of pouring system are improved and iron can be cleaned. According to structure of casting, positions of leakage are researched. The wall is formative by tapper core and water jacket core, which practically is less than 7mm theoretically and it is easily penetrated by inclusions. The measure is to modified tapper core frocks.For all these subjects, measures are made after testing. DOE method is used during testing and Pro cast simulation software is used to simulate pouring and solidifying process of cylinder block, and Minitab software is used to analyze testing results. All the measures is put into effect and are wrote into work guiding books.In the last, the leakage rate of cylinder block is reduced to about 0.8%. The improving effect is very obvious and a lot of waste loss is saved. The analysis and measures can supply reference to leakage defect of gray cast-iron cylinder block.
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