發(fā)布時間：2018-08-30 17:51

【摘要】：裂解連桿加工技術作為最先進的連桿制造技術,它的質量對發(fā)動機的性能有著無比重要的影響。但是裂解連桿要求材料同時具備脆斷性和良好的綜合力學性能,這嚴重限制了裂解連桿技術的發(fā)展。針對這一問題,通過雙金屬復合鑄造技術制備裂解連桿,這種方法可以使高碳鋼、鋁合金以及鈦合金用于裂解連桿的生產制造,突破裂解材料的局限性,但在對鑄坯鍛造的過程中很容易出現界面鍛裂、開裂,鍛后裂解區(qū)不能實現脆性裂解等問題。為了解決雙金屬鑄坯在鍛造過程中存在的問題,本文對25鋼和T10A復合連桿鑄坯進行鍛造強化研究。研究結果表明,通過雙金屬鍛造處理可使鑄件試樣組織致密,界面不開裂,雙金屬的力學性能得到提高,能夠實現脆性裂解。本文的主要工作和結論如下:(1)首先通過熔模鑄造制備鋼制雙金屬鑄件,然后在不同工藝參數下對鑄件進行鍛造處理以及熱處理,接著通過分析界面區(qū)域顯微組織,界面元素成分以及界面強度和硬度的變化來研究鍛件是否滿足裂解連桿的性能要求,最后對雙金屬鍛件進行裂解與重裝試驗。(2)研究了雙金屬復合鑄造以及鍛造時界面的結合性能,并且選出了最優(yōu)的鑄造和鍛造工藝參數。結果表明,控制主體材料澆注溫度,裂解材料厚度在一定范圍內,雙金屬復合鑄件表面無鑄造缺陷,界面能夠實現熔合結合,形成一定厚度的擴散層;鍛造過程中,試樣有向橢圓形變形的趨勢,裂解區(qū)具有一定的張力,在一定的鍛造比范圍內,雙金屬界面不開裂,界面始終保持冶金結合,能夠滿足雙金屬鍛造的要求。(3)通過研究不同鍛造工藝參數下界面的宏觀質量、微觀組織變化、鍛件界面強度和界面區(qū)域顯微硬度的變化。得出鍛造溫度和鍛造比對鋼制雙金屬界面是否開裂具有較大的影響;冷卻方式對界面區(qū)域材料的微觀組織,強度和以及元素成分擴散具有顯著影響;鍛后的調質處理降低了界面區(qū)的顯微硬度和強度,提高了連桿主體的韌性和綜合性能,也保證了裂解材料依然可以脆性裂解。(4)研究了在不同裂解槽參數下的雙金屬鍛件的裂解與重裝試驗。結果表明當裂解槽深度為0.5mm,裂解槽張角為60°,裂解區(qū)斷裂的斷口截面收縮率為1.47%,斷口表面平整,無掉渣、臺階等缺陷,具有明顯的脆性斷裂特征;重裝后的試樣比原始長度增加0.23mm,小于裂解連桿要求的0.5mm的誤差要求,表明鍛造后的試樣滿足裂解連桿的裝配要求。裂解試驗與重裝試驗的結果也驗證了鍛造工藝的合理性。
[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 擄, 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.
【學位授予單位】：江蘇大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG316

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本文編號：2213823