| Compared with other metals, aluminum and its alloys possess special and excellentphysical and chemical properties, mechanical properties and process characteristics to becomeone of the focuses of reserch and application. Although the tensile strength and modulu ofelastic is slightly inferior to traditional irron and steel materials, they are widely used in railtranspotation products domestic and abroad because of their higher specific strenth, higherspecific modulus and other beyond comparision properties than irron and steel after heattreatment to acheieve lightweight and modernnization.This subject is entrusted by Beijing CED railway electric tech. Co., Ltd. Domestic6082aluminum alloy used in welding joint composed by spindle and lifting lug lowerarm structure of pantograph as research object. By means of scanning electronmicroscope, metallographic analysis instrument and conventional mechanical teststechniques, compared and studied effects of comprehensive performs on6082aluminum welding joint from preheating temperature, shielding gas, welding heat input.Providing theoretical basises for the actual production and subsequent welding processoptimazition. Fond out the renson for the crack on the welding joint composed ofspindle and lifting lug of lower arm structure of pantograph, and giving somecorresponding solutions, ensure the welding quality of products.The results of test show that when preheating temperature at100℃, the strenghthefficiency of welding joint is0.61. Higher preheating temperature will make thestrength of joint suffer losses seriously. Therefor, preheating temperature should beavoieded or lower as far as possible. Mechanical properties of the welding joint shieldedby helium-high is good, the shielding gas of arc welding of pure argon can be replacedby helium-high when welding thicker aluminum alloy. The welding heat input has asignificant effection on the mechanical properties of6082aluminum alloy, it should belimited.In the T-joint welding crack susceptibility test, solidification crack do not generate.Liquefied crack rates of two specimen are1.67%and4.17%. Through analysis thedistribution of crack location and propagation path, determined the crack of welding jointcomposed of spindle and lifting lug is a liquefied crack. Higher preheating temperatureincreases the crystallization temperature range of deposited metal, on the other hand, due toaluminum alloy possesses high thermal expansion rate, liquefied crack generater under thecombined effects of the welding stress. |
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