毕业论文

当前位置: 毕业论文 > 材料科学 >

3D deform反挤压实验设计+文献综述

时间:2017-10-11 15:57来源:毕业论文
制品表面和边角不易产生裂纹。制品尺寸精度高。沿制品截面上和长度上的变形比正挤压时更均匀,因而制品沿截面和长度上的组织与性能比较均匀,反挤压的成品率高。所以我们需要
摘要金属挤压时制品流出方向与挤压轴运动方向相反的挤压,称为反向挤压或简称反挤压。反挤压法只要用于铝及铝合金、铜以及铜合金管材与型材的热挤压成形,以及各种铝合金、铜合金、钛合金钢铁材料零部件的冷挤压成形。反挤压时金属坯料与挤压筒壁之间无相对滑动,挤压能耗较低,因而在同样能力的设备上,反挤压法可以实现更大变形程度的挤压变形,或挤压变形抗力更高的合金。与正挤压不同,反挤压时金属流动主要集中在模孔附近的领域,因而沿制品长度方向金属的变形是均匀的。但是,迄今为止反挤压技术仍不完善,主要体现在挤压操作较为复杂,间隙时间比正挤压长,挤压制品质量的稳定性还需进一步提高等方面。所以本课题的研究是跟随着国际的脚步。挤压加工具有提高金属的变形能力、制品综合质量高、产品范围广、生产灵活、工艺流程简单、设备投资少等优点,在金属成形加工中广泛使用。挤压加工分正挤和反挤压两种基本形式,各有特点,生产中应根据产品规格品种加以选择。本实验采用反挤压方法对管材进行挤压成形。本实验用两种不同速度通过反挤方式对坯料进行挤压实验,讨论不同速度条件下的挤压力变化和金属流动特点,掌握模具形状及挤压变形程度对挤压力和金属流动的影响,从而有助于挤压工艺制度的合理制定。从金属流动的运动学特点来看,无论正挤压或反挤压,制品的外层都是由经受很大变形的金属微粒构成。但是,变形程度、外层厚和一般变形不均匀性就制品截面和长度而言反挤压时都比正挤压时小。与正挤压相比,反挤压具有下列优点。在相同的挤压条件下,反挤压法由于挤压筒壁与坯料表皮之间无相对滑动,不产生摩擦损耗,所需的最大挤压力可比正挤压降低30%~40%。可在较低温度下挤压有较大挤压比的小断面制品,提高生产效率。所需最大挤压力与坯料长度无关,因而可采用长坯料挤压长制品。挤压筒和模具的磨损少,使用寿命长。反挤压时尾端金属无倒流现象,因而其挤压残料厚度可比正挤压的减少50%以上。坯料和挤压筒之间不产生摩擦热,而且变形区体积小,变形热小,因而模孔附近制品的温升小,可采用较高的速度进行挤压,制品表面和边角不易产生裂纹。制品尺寸精度高。沿制品截面上和长度上的变形比正挤压时更均匀,因而制品沿截面和长度上的组织与性能比较均匀,反挤压的成品率高。所以我们需要进一步的研究反挤压的实验过程,来优化实验。14180

源自六[维^论'文]网.加7位QQ3249'114 www.lwfree.cn


关键词: 反挤压;模具设计;软件模拟;
General Description
Metal extrusion products flow direction and the extruding shaft moving in the opposite direction of extrusion, was called indirect extrusion or backward extrusion. Indirect extrusion method was used for aluminum and aluminum alloy, copper and copper alloy tube and section bar hot extrusion forming, and a variety of aluminum alloy, copper alloy, titanium alloy steel parts cold extrusion. Indirect extrusion and extrusion of metal blank wall had no relative sliding, Extrusion with low energy consumption, and in the same capacity equipment, reverse extrusion method can achieve greater deformation degree of extrusion deformation, or extrusion deformation resistance of high alloy. And forward extrusion, extrusion, metal flow mainly concentrated in the die hole near the field, thus along the length direction of products metal deformation is uniform. However, so far the reverse extrusion technology is still not perfect, mainly reflected in the extrusion process is relatively complex, clearance time than direct extrusion, extrusion product quality stability should be improved etc.. So the research of this paper is to follow in the footsteps of international. Extrusion can improve the metal deformation capacity, products of high quality, product range, production flexibility, simple process, less equipment investment and other advantages, widely used in metal forming process. Extrusion processing of forward extrusion and extrusion of two kinds of basic forms, each have a characteristic, production should be based on product specifications to choose. This experiment adopts the reverse extrusion method for pipe extrusion. This experiment with two different speed through the backward extrusion for billet extrusion experiment, discuss the different speed under the conditions of the pressure change and metal flow characteristics, the master mold and shape of extrusion deformation on extrusion pressure and metal flow effects, thereby contributing to the extrusion process system and reasonable development. From the metal flow kinematics characteristics, whether it is extruded or extrusion, products are subjected to large deformation of outer layer by the metal particles. However, the degree of deformation, the outer layer thickness and generally uneven deformation of cross section and the length of backward extrusion products than they are extruded small. Compared with direct extrusion, the extrusion has the following advantages. In the same extrusion conditions, backward extrusion method due to the extrusion cylinder wall and the blank between the epidermis of the relative sliding, friction loss, the maximum extrusion pressure is lower than30%~40% extrusion. At a low temperature extrusion having large extrusion ratio of small section of products, improve production efficiency. The maximum extrusion pressure and blank length independent, and thus can be used long billet extrusion long products. Extrusion and die less abrasion, long service life. Anti extrusion end metal non backflow phenomenon, so its extrusion residue thickness can be reduced by more than 50% than the forward extrusion. Blank and the extrusion cylinder is not generated between the friction heat, and the deformation zone is small in volume, deformation is small, so the die hole near products, small temperature rise, can adopt the high speed extrusion, surface and corner is not easy to generate cracks. Product size and high precision. The products section and the length of the deformation is more uniform than extrusion, so products along the cross section and length on the comparison of microstructure and properties of uniform, high rate of finished products of the backward extrusion. So we need to further study the extrusion experiment process, to optimize the experimental. 3D deform反挤压实验设计+文献综述:http://www.lwfree.cn/cailiao/20171011/14643.html
------分隔线----------------------------
推荐内容