抛丸处理对ADC12挤压铸造件表面状态影响

发布时间：2018-03-06 09:03

本文选题：ADC12挤压铸造件　切入点：抛丸处理　出处：《哈尔滨理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：抛丸处理技术被普遍应用于铸造件生产的后续表面处理,最初抛丸处理主要应用于钢铁等重金属的表面清理,所以抛丸处理也被成为抛丸清理,随着轻量化进程的发展,大量铝合金零件的生产需要抛丸处理。对铝合金件的抛丸处理不仅限于清理其表面,更主要是对零件进行表面性能的强化,比如:改变表面形貌、粗糙度的改变、提高表面硬度、增加表面残余压应力、提高疲劳强度。但抛丸处理工艺对铝合金铸件表面状态影响还没有进行过系统性的研究。本文以ADC12铝合金挤压铸造件为试验对象,研究了18种不同抛丸处理工艺对ADC12铝合金挤压铸造件的表面形貌、表面硬度、粗糙度、强化层厚度和表面残余应力的影响。研究结果表明:经抛丸处理后ADC12铝合金挤压铸造件表面硬度由100HV提高到112.7-163HV范围,粗糙度由Ra1.600提高到Ra2.480-6.515范围。影响规律为:试样粗糙度随抛丸时间增加而略有提高,随抛丸速度的提高而提高,0.45mm和0.25mm两种直径钢丸对试件粗糙度影响差别不大。粗糙度最小值和最大值均在抛丸时间400s工艺中出现。试样硬度随抛丸时间的增加而提高,随抛丸速度的提高而提高,钢丸直径大的工艺试样表面硬度高。影响试件硬度的工艺由主要到次要的排序为:抛丸速度、抛丸时间、钢丸直径。抛丸后ADC12铝合金挤压铸造件表面的硬度与粗糙度成正比关系。抛丸后试样表面硬度在主要由表面的强化层厚度、断层、颗粒组织决定。凹坑的深度和形貌起伏也间接体现出抛丸强化层厚度,凹陷越大试样表面硬度越高。凹坑深度增大、强化层厚增加和表面缺陷程度的增大使表面更容易形成大的最高点和最低点之差Ra,从而使表面粗糙度增大。硬度梯度数据可以显示抛丸强化层厚度,强化层厚度最小值为0.22mm,最大值为1.12mm,试验面硬度越高的试样其强化层厚度越大,抛丸工艺对硬化层厚度影响跟随对硬度影响规律。抛丸处理能有效提高表面残余压应力,经抛丸试样残余应力由未经抛丸的4.30MPa提高到7.64MPa。试件表面残余应力随抛丸速度、钢丸直径、抛丸时间的提高而增大,抛丸速度为主要因素。抛丸处理能够改善工件表层拉伸性能,但不会改变内部组织和缺陷情况。
[Abstract]:Shot blasting treatment technology is widely used in the subsequent surface treatment of casting parts production. At first, shot blasting treatment is mainly used to clean the surface of heavy metals, such as iron and steel, so shot blasting treatment is also called shot blasting cleaning, with the development of lightweight process, The production of a large number of aluminum alloy parts needs shot blasting treatment. The shot blasting treatment of aluminum alloy parts is not only limited to cleaning its surface, but also mainly strengthening the surface properties of the parts, such as changing the surface morphology, changing the roughness, The effect of shot blasting on the surface state of aluminum alloy castings has not been systematically studied. In this paper, ADC12 aluminum alloy squeeze casting parts are taken as experimental objects. The surface morphology, surface hardness and roughness of ADC12 aluminum alloy were studied by 18 different shot blasting processes. The effect of strengthening layer thickness and surface residual stress. The results show that the surface hardness of ADC12 aluminum alloy squeeze casting parts increases from 100HV to 112.7-163HV after shot blasting. The roughness is increased from Ra1.600 to Ra2.480-6.515. The law of influence is that the roughness of the sample increases slightly with the time of shot blasting. With the increase of shot blasting speed, the effect of 0.45mm and 0.25mm diameter steel pellets on the roughness of the specimen is not different. The minimum and maximum roughness of the sample appear in the 400s process of shot blasting time, and the hardness of the sample increases with the increase of shot blasting time. With the increase of shot blasting speed, the surface hardness of the process sample with large diameter of steel shot is higher. The order of the process influencing the hardness of the specimen is: shot blasting speed, shot blasting time, Diameter of steel pellets. After shot blasting, the hardness of ADC12 aluminum alloy squeeze casting parts is proportional to the roughness. After shot blasting, the hardness of the specimen surface is mainly determined by the thickness of the strengthening layer and the fault of the surface. The depth and shape fluctuation of the pit also indirectly reflect the thickness of the shot blasting strengthened layer, the larger the sag is, the higher the surface hardness of the specimen is, and the deeper the pit depth is, the higher the surface hardness is. The increase in the thickness of the strengthened layer and the increase in the degree of surface defects make it easier for the surface to form a large difference between the highest and lowest points, thereby increasing the surface roughness. The hardness gradient data can show the thickness of the shot peening strengthened layer. The thickness of hardening layer is 0.22 mm and the maximum is 1.12 mm. The thicker the specimen with higher hardness of test surface, the greater the thickness of hardening layer is, and the effect of shot blasting on the thickness of hardened layer follows the rule of hardness. Shot blasting treatment can effectively increase the residual compressive stress of the surface. The residual stress of the sample was increased from 4.30MPa to 7.64MPa. The surface residual stress of the specimen increased with the increase of the shot blasting velocity, the diameter of the steel shot, the shot blasting time, and the shot blasting velocity was the main factor. The tensile properties of the surface layer of the workpiece were improved by shot blasting treatment. But it will not change the internal organization and defects.
【学位授予单位】：哈尔滨理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG246

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