【作者】 张琳；

【导师】 邢书明；

【作者基本信息】 北京交通大学 ， 材料加工工程， 2007， 硕士

【摘要】 液态压铸件内部缺陷率较高,产品不便热处理,因此如何降低压铸件的缺陷率成为急需解决的问题,并引起广大研究学者的关注。本文以A356铸造铝合金汽车化油器为例,系统研究了半固态流变成型工艺。利用斜坡冷却法制备半固态浆料,并进行了流变压铸工艺参数对铸件质量的影响分析。力学性能测试表明,即使在半固态条件下,如果工艺控制不当,依然会产生气孔等缺陷。然而与同等条件下的液态压铸件相比,这些缺陷明显要小得多,因此进一步对压铸工艺参数进行控制,得到了表面质量较好,且内部没有气孔的半固态流变压铸件,解决了液态压铸所不能完全改善的问题。至此,半固态流变压铸工艺的优越性得到体现。研究方法和主要成果如下:使用电阻炉熔炼A356铝合金,并采用斜坡冷却法进行半固态熔体的制备。此方法的机理是利用熔体自身的重力,沿斜坡流动的同时,在槽壁上产生初生晶粒,并随着流动过程达到自身搅拌和晶体游离的作用,形成组织较为均匀圆整的半固态熔体。该方法设备简单,易于实施,且半固态组织较为理想。进行汽车化油器压铸模具的设计分析,并对各个部分功能有了整体的把握。使用汽车化油器压铸模具进行了液态压铸及半固态流变压铸的对比实验。配合压铸工艺参数,研究了影响薄壁型化油器零件的组织性能及内部缺陷的因素。使用万能试验机及摆杆冲击试验机进行了力学性能的测定,并用金相分析仪进行了A356铝合金不同压铸工艺参数下的微观组织的观察。结果表明需要严格控制压铸工艺参数,否则即使在半固态流变压铸条件下,也会因缺陷的产生而导致力学性能的下降。总体来看,半固态流变压铸实验结果仍较好于液态压铸,且随着浇注温度的降低,压铸缺陷的减少,得到的组织越趋于圆整、细小。更多还原

【Abstract】 Traditional die-casting internal defect ratios are always high, and can not easily do the thermal treatment, so how to reduce these defect ratios is an emergent question which needs to be solved has already gathered much concern of scholars.The paper systematically does some research on semi-solid rheological forming technology mainly on carburetor part which is made of A356 aluminum casting alloy. And the study uses the cooling slope method to prepare semi-solid slurry, then does analysis and research on the influence of rheological die-casting technical parameters to the performance of castings. Mechanical property test shows that if craft is not been well controlled, it will produce porosities as well, though under semi-solid conditions. However comparing with the one under the same conditions of traditional die-casting, these detects is much smaller. Therefore, need to do further study on the controlling of die-casting technical parameters, the result shows the good quality of surface and no porosities inner, and solves the problems that traditional die-casting can not solve. By now, the superiorities of semi-solid rheological die-casting are externalized. Research method and main results is as following:Using electrical resistance furnace and cooling slope to melt A356 aluminum alloy and gain the semi-solid slurry. And mechanics of this method is to use the gravity itself to produce the primary grain on the surface when flowing down with the cooling slope, then gains the self-stirring and crystals extricating to form the uniform and near-circular structures of semi-solid slurry. Equipments of this method are simple and easy to put into effect, also the semi-solid structures is proper.Designing and analyzing the carburetor die-casting mould to have a whole idea of every part function, then using the mould to do the comparing experiment of traditional and semi-solid rheological die-casting. To make research on the influencing factors of thin-wall carburetor structures and internal defects which are connecting with die-casting technical parameters. Using the universal test machine and impact test machine to measure the mechanical properties and also using the metallographic analysis machine to do the microstructures observation of A356 aluminum alloy under different technical parameters. The result shows that these parameters should be strictly controlled or the mechanical properties will fall down because of the defects producing, though under semi-solid rheological die-casting. However, the results of semi-solid one更多还原