| 6M cylinder head is one of the company’s leading products,which is mainly used for high-power heavy-duty diesel engine,it is characterized by complex cavity structure,wall thickness disparity and strict material requirement,therefore,the thin wall with high strength should be one of the requirements for cast.In order to improve the company’s competitiveness on the heavy machinery market,the company transfered 6M cylinder head material from the HT250 to RuT350,However,due to the immature vermicular iron treatment process,there are many quality problems such as injection vermicularizing,leakage,and hardness not up to standard(180HBS),which seriously affects the output of casting and the development of heavy duty engine products market.According to the need of the diesel engine products development promotion,in this paper,through the study of gating system design,cupola melting process,the control of sulfur content,vermicularizing addition and adding temperature,the time out of mold and exhaust system,and the micro-alloying elements added,We studied the vermicularizing treatment process methods and quality control methods of 6M cylinder head systematically,the main results are as follows:(1)The results show that vermicularizing treatment will be effective with the method of "dam-style" + "lander".The total amount of rare earth magnesium and rare earth silicon vermicularizing added during Vermicularizing processing should be controlled at 0.55%or less.(2)It is effective to control S content by choosing the coke of which S content is less than 0.25%,ingredienting with high ratio of iron to coke and melting with high temperature and low S content.There is a strong linear relationship between S content and the casting scrap rate,the higher S content,the higher casting scrap rate.we should control the S content by increasing the ratio of iron to coke as well as external desulfurzation.(3)As to the same metal material,due to the cooling environment is different,compared with the 5 hours out of the mold,the 2.5 hours can improve casting hardness 20～30 units.For 6M cylinder head,the content of Sn controlled in the range of 0.055～0.070%will not affect the casting water leakage,and can guarantee the casting hardness in the range of 180-210HBS.(4)In the process of injection vermicularizing treatment,the most reasonable injection vermicularizing treatment temperature is set to a temperature of 1485℃～1500℃ for the first 5 package;after the fifth package process the temperature is set to a temperature of 1475 ℃～1490 ℃.During the gating system designing,the intercepting location is SPR,it can reduce the turbulent flow of hot metal into the gate effectively,and guarantee flowing molten iron smoothly.The sequence of the amount of core gas evolution is that the precoated sand is the largest,the furan resin sand is the second,and the cold core sand is the minimum,in the production,we should choose the minimum ones as far as possible.At the same time,we should guarantee the sand core group is dry and the moisture should be 0.15%or less.During designing of exhaust system,we should follow the principle that gas cavity and core exhaust gas channels should be separated and strengthen the core set of exhaust on the back.(5)By vermicularizing a small triangle block,triangle block Ⅰ,triangle block Ⅱ to control the process before furnace,can give effective guidance to the injection vermicularizing process,and improve the vermicularizing process consistency. |
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