The Effect Of Unequal Length Bearing On The Behavior Of Flow And Temperature In The Extrusion Process

With the rapid development of high-speed trains, aerospace, ship weapons and manufacturing industry, metal extrusion products is larger and more integrate、high precision and complicated, thus bring big challenge to mold-designing at the same time.The unequal length bearing of extrusion die is the key of keeping the balance of each part of extrusion section metal flow rate, obtaining products with high surface quality and dimensional accuracy. The unequal length bearing of extrusion die which could produce large solid aluminum alloy profile usually has complicated structure and big change in size, thus rings difficult to design. It’s h rd to design reasonable unequal length bearing by traditional design method which derived from the engineering analogy.By using the Finite Element Method, acquire the influence law of unequal length bearing on the rheological behavior and temperature behavior of metal, forecast the forming quality of products, improve the efficiency of the design and reduce the production cost.For this, based on a small rectangular section profile, by using the method of numerical simulation combined with extrusion experiment, studied the effect of unequal length bearing on the flow velocity and extrusion temperature, obtained the rule of block about the unequal length bearing works on the flow velocity, built the quantitative relationship between the length of unequal length bearing and flow rate.The results showed the length of the bearing adds 1mm, the maximum flow rate of the profile decreases by 0.9mm/s. When the length of the bearing increases to 5~6mm, the SDV of the section is 0.2, velocity of the section distribution uniformity, the shape of the profile is better. The configur tion of e ring’s re on two fl nks of the extrusion center ranges from 1.00 to 1.05. When L increased to 6mm, the offset of the bending achieved the minimum deviation: 0.19 mm, 0.57 mm, the profile is almost close to section contour with flat shape, improved the left side sword curved phenomenon effectively. Changing the length of the bearing has little effect on the distribution of the temperature, the temperature rose 2oC after optimization, while the distribution of the stress changes 50 MPa.On this basis, the die and bearing were set to independent geometric entities and geometry modeled by split type, the contact surface between inner wall of the container, surface of the die and deformation metal were set to shear friction model, the contact surface between deformation metal and the bearing was set to coulomb friction model. For the knife bending defects made in the extrusion process of large size aluminum alloy profile, by using the numerical simulation method, analyzed the effect of the unequal length e rings’ structure nd size on the flow eh vior nd the forming qu lity of the metal, designed the structure and size for different parts of the bearing, improved the uniformity of the flow on the cross-section of the profile effectively, improved the stress concentration phenomenon on the surface of the profile, acquired the distribution of the temperature field on the cross-section of the extrusion profiles.The results showed that When the length of the bearing where the slowest flow rate distributed is decreased from 5mm to 2mm, the flow rate increases from 2.1mm/s to 2.3mm/s, and the length of the bearing where the fastest flow rate distributed is increased from 19 mm to 25 mm, the flow rate reduces from 3.9mm/s to 2.2mm/s, the distribution of the flow rate is uniform, the extrusion profile is flat,the difference value between the maximum and minimum flow rate is 0.72mm/s on the cross-section of the profile after optimization; The longest part of the bearing earns the highest temperature on the surface, and the shortest part of the bearing earns the lowest temperature on the surface; The stress concentration phenomenon disappeared.