Zinc Clad Steel Wire Composite Continuous Extrusion Coating Process Research

As a kind of bimetal composite, zinc cladding steel wire has many advantages such as high strength, favorable electrical conductivity and corrosion resistance. It has been widely used for petroleum pipeline and the city pipe-nets, especially in the application of corrosive conditions. At present, the method of preparing zinc cladding steel wire is electrochemistry method, which has many shortcomings. In this paper, the forming -continuous extrusion cladding method was proposed. A combination of bonding good thick layer of zinc clad steel wire was prepared successfully based on the theoretical analysis and experimental research. The results could provide a theoretical and technical guidance for large-scale industrial production.The key problems, such as line tension, plastic deformation velocity field and die cone angle of continuous extrusion cladding process were analyzed by the upper bound theorem and virtual principle. The theoretic analysis results indicated that additional stress - of the steel wire needn't impose and the forward-line tension entirely was provided by the extrusion process the friction in the process of continuous extrusion coating. In the exports of coating module, the axial flow velocity of the deformation zinc material should accord with the movement velocity of the steel wire in order to ensure zinc layer and the core being close combined, which could achieve effect of metallurgical combination. The half angle of the conical profile had significantly impacts on the radial force in cladding process. The calculation results indicated that friction factor and half angle satisfied with a certain condition could achieve superposition of the ultimate mold center and center-line because the steel wire become eccentric in the presence of centripetal force.Continuous extrusion cladding experimental results showed that the product quality and productivity depended on the effects of zinc deformation temperature, squeeze round of speed, steel core preheating temperature, steel core movement speed and steel core tension. Control of above parameters could make the production process successfully and guarantee product pass ratio. Several flaw from the extrusion process had core line shoved off, lax weld and eccentric. The reasons of off-line showed were excessiveσ_s/σ_c, excessive length of the deformation and too much extrusion ratio. Too wide segregation bridge resulted in lax weld. The eccentric appeared with unreasonable design of the mould. By adjusting the process parameters and improving mould design, the defects were avoided and the zinc cladding steel wire with good bonding properties was obtained. At last, the corrosion resistance and electrical conductivity properties of the product were discussed.