【作者】 赵雷；

【导师】 苏彦庆；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2009， 硕士

【摘要】 铸造Al-Si合金由于其成分含有大量的硅而具有优良的铸造性能,如流动性好,收缩小,热裂倾向小等优点。主要用来生产形状复杂、薄璧、耐蚀、气密性要求高、承受中、高静载荷或冲击载荷,或要求在较高温度下工作的大、中、小型铸件,因此广泛地应用于航天、汽车、机械等行业。铸造Al-Si合金铸件占铝铸件的85%～90%,是铝基铸造合金中最重要的一个系列。但是对于该合金系铸件的整个生产过程中,由于铸造涂料、机加切削液等的影响,极易在铸件的表面形成了难以用普通的清洗方法除去的暗斑,不但严重影响了铸件的外观,对铸件的耐蚀性也极为不利。本文主要选用铸造Al-Si系合金ZL102合金进行消除表面色差的研究,改善铸件的外观。针对铸件表面质量最终要求的不同,制定了可以满足不同要求的三条工艺路线:第一,试样制备→除油脱脂→喷砂处理;第二,试样制备→除油脱脂→除灰出光→防锈处理;第三,试样制备→除油脱脂→除灰出光→阳极氧化。由于在对铸件进行表面处理的过程之前,首先都要经过除油去污处理,在除油之后在铸件的表面就会形成一层黑色吸附膜,其成分为未溶解的硅,消除这层疏松的硅就成为Al-Si合金表面处理的一个关键步骤。在第一条工艺流程中,经过适当的喷砂处理之后,表面的黑灰可以除去,得到洁净的亚光表面,但是这种表面的抗污染能力和耐蚀性较差,只限于表面质量要求不高的铸件和对耐蚀性要求不高的铸件,或者作为其它表面处理的预处理;使用第二条工艺流程时,使用的除灰溶液为浓硝酸和氢氟酸的混合溶液,得到的表面为灰白色的表面,再经过防锈处理后在表面形成一层氧化膜,颜色仍为灰白色,这种处理工艺不但表面外观质量较好,得到的氧化膜还具有一定得耐蚀性,可以避免在潮湿环境中贮存时生锈;第三条工艺流程主要是对除灰之后的表面的进一步处理,ZL102铸件表面阳极氧化之后无论从微观形貌还是宏观表面都不同于其它铝合金阳极氧化后的表面,原因是硅元素引起的。阳极氧化最后的表面为灰黑色的多孔层,经封闭处理之后具有很好的耐磨性和耐蚀性。更多还原

【Abstract】 Al-Si casting alloy has good cast performance, that is, good liquidity, less contraction, small hot cracking tendency, for containing a large number of Si. It was widely used in aerospace, automotive, machinery, etc., to produce complex shapes, thin-wall, corrosion resistance, high air tightness, and which can bear middle-and high-static load or impact load, or those requested to work at a higher temperature castings. Cast Al-Si alloy is one of the most important aluminum alloys, whose castings account for 85% ~ 90% of the aluminum alloy castings. However, during the entire production process, dark stain is formatted on the surface of the cast, which is resulting from the mold coating and cutting fluid. It is hard to remove the dark stain from the surface of cast in general method, namely the chromatic aberration emerges on the surface.In this paper, the ZL102 alloy is selected to study eliminating chromatic aberration from the surface of cast. To eliminate color aberration of cast, three processes are designed. They are as follows: the first is making samples→degreasing→abrasion blasting; the second is making samples→degreasing→desmutting→rust prevention; the third is making samples→degreasing→desmutting→anodizing.As surface treatment for cast, the degreasing should be completed firstly, as a result a layer of film will be adsorbed on the surface and its ingredients is silicon which is not dissolved in degreasing. In the first process the black film will be removed after abrasion blasting, as a result sub-bright surface will be got. But this surface has lower contamination resistance and corrosion resistance. So the first process can only be used to modify the surface quality, or as pre-treatment of other surface treatment. The solution for the desmutting is the mixture of concentrated nitric acid and hydrofluoric acid, and the color of cast surface is gray-and-white after desmutting. There will be also rust prevention treatment in the second process and also get white surface which can make the cast avoiding getting rust in wet storage. The third process is a further treatment after desmutting. Both the micro-morphology and macro-morphology of ZL102 alloy’s anodic film is different from that of pure aluminium. This is caused by silicon. The anodic film of ZL102 alloys is black porous oxide film, which will have good wear resistance and corrosion resistance after sealing.更多还原