铸造抽芯新工艺制备大长径比细孔的成孔特征

In the field of hole preparation, it is difficult to obtain curved hole and micro-hole with the diameter of 0.1-3 mm and aspect ratio over 100 by machining, non-traditional machining and casting methods. So carbon fiber was chose as main material of hole core to prepare curved hole and micro-hole with large aspect ratio by casting methods, and the single hole with 0.22 mm diameter and aspect ratio 1800 and curved hole have been successfully cast. Characteristics of hole-forming were further researched, main content: (1) carbon fiber core and its surface characteristics influence on quality of micro-hole; (2) the solidification and crystallization method of aluminium alloy influence on characteristics of hole; (3) study on pulling resistance model of hole core and ultimate aspect ratio. (4) preparation of curved hole with U-shape and analysis on pulling resistance of composite core. Innovativeness are as follows: a new preparation which called as casting core-pulling method was proposed to acquire micro-hole with large aspect ratio; qualitative characteristics and forming of micro-hole with large aspect ratio were revealed; the method of pulling-casting is first sued to manufacture U-shape hole. The key problems are following: a large amount of data acquisition on pulling resistance of hole core, surface tension effect on characteristics of hole-forming and analyze on pulling resistance of composite hole core, etc. Scientific significances are that a new process was provided to prepare micro-hole with aspect ratio and curved hole, influence rule of solidification and crystallization and pulling resistance for preparation of hole are grasped, and preparation capacity and level of micro-hole and curved hole are enhanced.

在孔制备领域，直径0.1-3mm、长径比>100的大长径比细孔及弯孔的制备，采用机械、特种加工和铸造法难以实现。为此，本项目提出以碳纤维作为主要孔芯材料、采用铸造抽芯方式制备大长径比细孔和弯孔新工艺，并成功制备直径0.22mm、长径比1800单孔和弯孔。现对成孔特征深入研究，主要内容：(1)碳纤维孔芯及表面特征对孔质量影响的研究；(2)铝合金凝固结晶方式对成孔特征的影响；(3)细长孔制备孔芯抽出阻力模型、极限长径比研究；(4)“U”型弯孔制备及复合孔芯抽芯阻力分析。创新点：提出了铸造抽芯法制备大长径比细孔新工艺；揭示了大长径比细孔成形及质量特征；将铸造抽芯法首次用于“U”型孔制备。本研究需解决大批量孔芯阻力数据获得、熔体表面张力对成孔特征影响、复合孔芯抽芯阻力分析等关键问题。科学意义：为大长径比细孔和弯孔制备提供新工艺，掌握凝固结晶、抽芯阻力对孔制备的影响规律，提高细、弯孔制备能力和水平。

随着先进、高端装备的发展，孔结构作为诸多零部件中的重要组成部分已广泛应用于多种领域中。然而在孔材料制备领域，采用机械、特种加工和铸造法难以实现直径0.1-3mm、长径比>100的大长径比细孔材料的制备，为此开发具有直径细小、大长径比特征的孔制备新工艺具有重要应用前景。本项目采用铸造法，利用碳与铝浸润性差两者反应较为微弱的特性，分别使用碳纤维孔芯和涂覆石墨涂料的金属丝孔芯成功制备了铝基大长径比阵列细孔材料和U型孔材料。并且从碳纤维及其表面特征、合金凝固结晶方式以及抽芯阻力角度，掌握了这一制孔新方法的特征，同时掌握了控制大长径比细孔成孔质量能力，为铸件中大长径比细孔制备奠定基础并提供了指导。在大长径比单孔和阵列空研究成果基础上，进一步探索了铸造抽芯法在U型弯孔制备中的特征。鉴于U型弯孔制备所采用的复合孔芯与单纯碳纤维孔芯显著不同，复合孔芯是以刚性金属体作为骨架、外层缠绕不同层数碳纤维，故进一步从复合孔芯的形变特征及抽芯阻力的影响因素探讨U型弯孔制备的一般特征和基本规律，为其它形状弯孔制备初步奠定基础。同时根据生产实际的需求，探究了实验温度及合金元素的添加对U型孔抗腐蚀性能的影响，为孔材料的实际应用奠定了理论基础。