Investigation On Cold Rolling Process, Microstructure And Properties Of TC4Alloy Thin Thickness Tubes

Titanium alloys were widely used in ocean industry and chemical industry.Traditionally, TC4seamless tubes have been produced by hot working because of the highstrength and bad deformation properties. Thereby, how to produce the thin thickness TC4seamless tubes by cold rolling becomes an important issue. In this paper, the initial tubeswas produced by cross piercing, with a thickness of5.5mm, the rolling process was taken bydifferent deformation and different rolling methods. Microstructure, hardness and strengthwere test and analyzed. Also, deformation mechanism was talked by analyze themacro-texture and the tensile fracture together. Experiments were taken in several parts andcorresponding results were got and show as follow:Firstly, heat-treatment process was investigated before rolling, the microstructure ofinitial tubes was between Widen and basket-weave structure which shows a tough strengthand hardness but bad plasticity. Before the rolling, tubes was warm keeping in vacuumheat-treatment furnace under the temperature of800℃for1-hr, furnace cooling to500℃, aircooling to room temperature. This heat-treatment plays action as residual-stress relieving,and plasticity improving. In the rolling process, choose the800℃as warm keepingtemperature of the rolling-before and pass-between heat-treatment.Secondly, the effect of rolling process parameter on tubes microstructure and propertieswere investigated. The parameter includes pass-between deformation, the number of rollingpasses, rolling process arrangement and rolling methods. Increasing pass-betweendeformation improve the strength and hardness of as rolled tubes, big pass-betweendeformation result in stripped metal flow trick, but result in bad surface and thicknessquality, the appearance quality was the best when pass-between deformation reach40%.Tubes as rolled strength reduced as the rolling pass number increase, this changes when theheat-treatment was taken. Rolling method includes2mill rolling and3mill rolling. The2mill rolling suits diameter reduces rolling and the3mill rolling suit thickness-reduce rolling.Attention should be paid on the parameter of△t/△Dwhen tubes were rolled by2mills.Thirdly, the macro texture was test and analyzed, the texture of initial tubes werehomogeneous.(0002) fiber texture appears after rolling. The <2-1-10>//rolling direction inthe rolling process, and a big deformation approve this trend.Finally, in this paper, deformation mechanism was talked by analyze the macro textureand tensile fracture. The main texture was {0001} basal texture and {10-15},{10-13}, {10-14} pyramid texture. In the rolling process, tubes were rolled by circumferentialpressure, therefore launch the {10-10} slip system, results in plastic deformation in macro, astrong but unorganized {0001} basal texture formed, in this research named it asapproaching {0001}texture.{20-21} pyramid texture formed when the pass-betweendeformations big enough.