Study On The Law Of Flow Distribution Of Large Flat - To - Thickness (Shaped) Flat - Row Metal And Optimization Of Mold Structure

As the extending and development of aluminum and aluminum alloy continuous extrusion,the copper continuous extrusion mainly applied in producing copper conductive bar for various industrial power transmission, owning extensive application prospect.As the domestic copper flat line continuous extrusion technology matures, high-strengthing and alloying of produced materials, the complicate and flattening of produced shapes was the development direction of this technology.The key techmology of big flakiness ratio flat by continuous extrusion:1) using a large extending ratio combined cavity structure to realized the large deformation;2) the characteristics of metal flow distribution: the intermediate metal flow fast while the side flow slowly;3)extrusion friction between the wheel and block as extrusion driving force, so the maximum size of products is related to the extrusion wheel torque. The uneven metal flow which is closely related to the flow law of metal and the mold structure in a series quality defects of copper flat products with features of small section and width ratio,such as width restriction, easy edge crack, surface roughness, easy to color, the transverse thickness deviation, bad shape(wave pattern), total root tissue distribution. Therefore, the flow row and thermal field distribution of the big flakiness ratio flat in cavity and mold urgent need to be mastered as well as the influence mechanism of mold structure on extrusion wheel torque and die load,further realizing optimum structure size parameters to provide theoretical basis for production practice. The main research work and achievements are as follows:(1) The big flakiness ratio flat of copper was simulated by finite element numerical simulation. It was concluded that the speed distribution of the metal in the body cavity expansion field and the ways to improve the metal liquid which was increasing the matal contact area with the cavity.(2) The wide in the middle and narrow on both sides structure of large extending ratio combined cavity was beneficial to hinder the flow of middle metal, making the metal flow velocity more uniform. The influence of middle width H, edge width h and middle length of expansion cavity on SDV was analyzed by means of orthogonal experimental design. To be a conclusion, the optimal cavity structure is: l=62 mm, H=40 mm, h=24 mm. The impact of various factors on SDV value rank is H>1>h gained by nanlysis of variance.(3) The two main factors for die structure are calibrating strap and the angle of mould. The length of calibrating strap under obvious width-thickness ratio have effect on the uniformity ofmetal flow velocity. When calibrating strap is at a length of 7~9mm, the mean square deviation of metal flow velocity is less than 1, which indicated that the uniformity of metal flow velocity is good when the calibrating strap length is 7 ~ 9mm.Compared to circular- arc- shaped,trapezoid calibrating strap with differed length is more conducive to the uniformity of metal flow velocity.Extally setting a angle of 3o~15o to hinder metal flow at the die entrance could improve the die life. The simulation results showed that with increasing of the angle, the mean square deviation of metal flow velocity increased first and then decreased, and cavity and die loads reduces gradually.(4) The process of trapezoidal continuous extrusion was simulated by Finite element( FE).The flow rate of metal is faster at narrow parts and the flow rate of metal is slower. The velocity difference across them is 80mm/s, which it vulnerably causes quality problems,such as, the forming at narrow parts is relatively difficult. The die structure could be optimized by adjusting the length of die hole bearing land and increasing the angle of relieving bearing and chocking.