锻造钢制双金属连杆裂解及其性能研究

发布时间：2018-08-30 17:51

【摘要】：裂解连杆加工技术作为最先进的连杆制造技术,它的质量对发动机的性能有着无比重要的影响。但是裂解连杆要求材料同时具备脆断性和良好的综合力学性能,这严重限制了裂解连杆技术的发展。针对这一问题,通过双金属复合铸造技术制备裂解连杆,这种方法可以使高碳钢、铝合金以及钛合金用于裂解连杆的生产制造,突破裂解材料的局限性,但在对铸坯锻造的过程中很容易出现界面锻裂、开裂,锻后裂解区不能实现脆性裂解等问题。为了解决双金属铸坯在锻造过程中存在的问题,本文对25钢和T10A复合连杆铸坯进行锻造强化研究。研究结果表明,通过双金属锻造处理可使铸件试样组织致密,界面不开裂,双金属的力学性能得到提高,能够实现脆性裂解。本文的主要工作和结论如下:(1)首先通过熔模铸造制备钢制双金属铸件,然后在不同工艺参数下对铸件进行锻造处理以及热处理,接着通过分析界面区域显微组织,界面元素成分以及界面强度和硬度的变化来研究锻件是否满足裂解连杆的性能要求,最后对双金属锻件进行裂解与重装试验。(2)研究了双金属复合铸造以及锻造时界面的结合性能,并且选出了最优的铸造和锻造工艺参数。结果表明,控制主体材料浇注温度,裂解材料厚度在一定范围内,双金属复合铸件表面无铸造缺陷,界面能够实现熔合结合,形成一定厚度的扩散层;锻造过程中,试样有向椭圆形变形的趋势,裂解区具有一定的张力,在一定的锻造比范围内,双金属界面不开裂,界面始终保持冶金结合,能够满足双金属锻造的要求。(3)通过研究不同锻造工艺参数下界面的宏观质量、微观组织变化、锻件界面强度和界面区域显微硬度的变化。得出锻造温度和锻造比对钢制双金属界面是否开裂具有较大的影响;冷却方式对界面区域材料的微观组织,强度和以及元素成分扩散具有显著影响;锻后的调质处理降低了界面区的显微硬度和强度,提高了连杆主体的韧性和综合性能,也保证了裂解材料依然可以脆性裂解。(4)研究了在不同裂解槽参数下的双金属锻件的裂解与重装试验。结果表明当裂解槽深度为0.5mm,裂解槽张角为60°,裂解区断裂的断口截面收缩率为1.47%,断口表面平整,无掉渣、台阶等缺陷,具有明显的脆性断裂特征;重装后的试样比原始长度增加0.23mm,小于裂解连杆要求的0.5mm的误差要求,表明锻造后的试样满足裂解连杆的装配要求。裂解试验与重装试验的结果也验证了锻造工艺的合理性。
[Abstract]:As the most advanced manufacturing technology of connecting rod, the quality of pyrolysis rod has a great influence on the performance of engine. However, the pyrolysis rod requires both brittle fracture and good mechanical properties of the material, which seriously limits the development of pyrolytic linkage technology. In order to solve this problem, the pyrolytic connecting rod is prepared by bimetallic composite casting technology. This method can make high-carbon steel, aluminum alloy and titanium alloy used in the manufacture of pyrolytic connecting rod and break through the limitation of pyrolysis material. However, during the forging process of the billet, it is easy to crack at the interface and crack, and the brittle cracking can not be realized in the cracking zone after forging. In order to solve the problems existing in the forging process of bimetallic billet, the forging strengthening of 25 steel and T10A composite connecting rod billet is studied in this paper. The results show that by bimetallic forging treatment, the microstructure of the castings can be densified, the interface will not crack, the mechanical properties of bimetallic can be improved, and brittle cracking can be realized. The main work and conclusions are as follows: (1) Bimetallic steel castings are prepared by investment casting, then forging and heat treatment are carried out under different technological parameters, and then the microstructure of the interface region is analyzed. The change of interface element composition, interface strength and hardness to study whether the forging meets the performance requirements of pyrolysis link, Finally, the cracking and reloading tests of bimetallic forgings were carried out. (2) the bonding properties of bimetallic composite casting and the interface during forging were studied, and the optimum casting and forging process parameters were selected. The results show that there are no casting defects on the surface of bimetallic composite castings by controlling the pouring temperature of the main materials and the thickness of the pyrolysis materials, and the interface can be fused to form a certain thickness of diffusion layer. The specimen has the tendency of elliptical deformation, the cracking zone has a certain tension, in a certain range of forging ratio, the bimetallic interface does not crack, and the interface always maintains metallurgical bonding. It can meet the requirements of bimetallic forging. (3) by studying the change of macroscopic quality, microstructure, interface strength and microhardness of forgings under different forging process parameters. It is concluded that forging temperature and forging ratio have a great influence on the cracking of bimetallic interface in steel, and the cooling mode has a significant effect on the microstructure, strength and diffusion of elements in the interfacial zone. The tempering treatment after forging reduces the microhardness and strength of the interface zone and improves the toughness and comprehensive properties of the main body of the connecting rod. It also ensures that the pyrolysis material can still be brittle cracking. (4) the cracking and reloading tests of bimetallic forgings with different cracking tank parameters are studied. The results show that when the depth of cracking tank is 0.5 mm, the angle of crack is 60 掳, the shrinkage rate of fracture cross section is 1.47, the surface of fracture surface is flat, there is no slag drop, step and other defects, so it has obvious brittle fracture characteristics. The reassembled specimen is 0.23mm longer than the original length, which is less than the 0.5mm error required by the pyrolysis rod, which indicates that the forged specimen meets the assembly requirements of the pyrolytic link. The results of cracking test and reloading test also verified the rationality of forging process.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG316

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