【作者】 喻光远；

【导师】 蔡启舟；

【作者基本信息】 华中科技大学 ， 材料工程， 2011， 硕士

【摘要】 三乙胺法冷芯盒制芯工艺具有高效、节能、铸件表面质量好、尺寸精度高、砂芯溃散性好等优点,广泛应用于汽车、内燃机、拖拉机、工程机械、机车车辆、制泵等行业。但是,国内的一些企业在生产过程中存在如树脂加入量偏高、砂芯强度偏低、存放性差等问题,致使铸件废品率偏高。因此,对这些问题进一步的探讨和研究,可为三乙胺冷芯盒制芯工艺优化、提高砂芯性能和降低生产成本提供技术支持,具有重要的现实意义。本文结合东风汽车有限公司商用车铸造一厂(以下简称:铸造一厂)三乙胺法冷芯盒制芯车间的生产实际,分析了该厂目前树脂用量偏高和制芯效率低的原因,研究工艺条件对三乙胺法冷芯盒砂芯性能的影响,并提出了三乙胺法冷芯盒制芯工艺的改进措施,取得了如下研究成果。通过对铸造一厂三乙胺法冷芯盒制芯工艺的原材料质量和生产流程的分析发现,原砂水分偏高和压缩空气含水量较高是造成树脂用量偏高的主要原因。研究了树脂加入量对砂芯性能的影响。结果表明,随着树脂加入量的增加,砂芯的初始强度和24h终强度增加,砂芯发气量也相应增大。在树脂加入量为1.8%时,当组分Ⅰ与组分Ⅱ之比在50:50时,砂芯24h终强度达到最大值,在55:45时砂芯的初始强度达到最大值。组分Ⅰ与组分Ⅱ之比在50:50~55:45之间的比例,砂芯的抗拉强度的稳定性较好。研究水基涂料、环境湿度和温度对砂芯强度和砂芯断裂的影响。结果表明,水基涂料使砂芯24h终强度显著下降,下降幅度随树脂加入量的增加而减少;砂芯存放1~6h后浸涂的强度低于即时浸涂的强度和24h浸涂的强度。在常温高湿环境下,随着砂芯存放时间的延长,砂芯强度出现显著的下降;在40℃、RH100%的环境下,砂芯的强度在5h达到最大值,随后砂芯的强度随放置时间的延长迅速下降。在常温低湿环境下,树脂粘结桥断口为以内聚断裂为主的复合断裂,而常温高湿环境里存放的砂芯,水分使树脂粘结桥出现裂纹、砂芯呈附着断裂。基于上述研究结果,针对铸造一厂的降低树脂用量和提高制芯效率的目标,从原砂水分、混砂工艺、空气干燥器、浸涂料与烘烤、工艺与工装参数、砂芯仓储等几个方面提出了相应的改进措施。更多还原

【Abstract】 Tri-ethylamine Cold Box Core-making Process, with the features of more efficiency, energy saving, good casting surface quality, accurate dimension, good core collapsibility, has been widely used in automobiles, internal combustion engines, tractor, engineering machinery, rolling stock, brake pump. However, the high usage amount of resin, low performance and bad storage of sand core lead to the high scrap rate in production process of some Foundry Enterprise. Therefore, further studies on these problems can provide technical support for optimization of Tri-ethylamine Cold Box Core-making Process, enhancing sand core performance and reducing production cost, which have important realistic significance.In this paper, combining the production practice of No.1 Foundry Plant, Dongfeng motor Co., Ltd (hereinafter called: No.1 Foundry Plant), reasons for the high usage amount of resin and low efficiency of core-making were analyzed. Furthermore, effects of process conditions for sand core performance of Tri-ethylamine Cold Box based on actual production were studied. Finally, several improvement measures of ISOCURE of No.1 Foundry Plant were proposed, and the results achieved are as follows.Through analyzing quality of raw materials and production process of Tri-ethylamine Cold Box Core-making of No.1 Foundry Plant, high water content of the raw sand and the compressed air is identified as the main reason for high usage amount of resin.The effect of the amount of added resin on sand core performance was studied. The results showed that the initial strength and the 24h final strength of sand core increased with the increase of amount of addition of resin, the gas evolution indicate the same variation tendency. When the amount of added resin is 1.8%, he 24h final strength reach the maximum at the ratio of two components is 50:50, and the initial strength reaches its maximum at the ratio of 55:45. It is also can be seen that the tensile strength of sand core has good stability when the ratio is between 50:50 and 55:45.And then, research of water-based paint, environmental humidity and temperature on strength and fracture of sand core were also explored. The results showed that the water-based paint made the 24h final strength decrease significantly, but the decline rate decreased with the increase amount of added resin; the strength of core painted during storage time 1-6h was lower than that of immediate painted core and painted after storage 24h. In the environment of room temperature and high humidity, the core strength decreased significantly due to high humidity with the extension of storage time. In the environment of 40℃and RH100%, the sand core reaches its maximum strength within 5h, and then the strength declined rapidly with the extension of storage time. The resin binding bridge showed cohesive-fracture-dominated compound fracture in the environment of room temperature and low humidity, While, the resin binding bridge showed the adhesive fracture because of moisture-induced cracks in high humidity environment.Based on these, several improvements for the raw water content, sand mulling, compressed air dryer, dip coating and heating, process and tooling parameters and sand core storage have been proposed to reduce the usage amount of resin and increase efficiency of core-making.更多还原