| Titanium alloy has many outstanding advantages such as low density, high specific strength, high corrosion resistance, excellent high temperature performance. It has been widely used in the field of aerospace, marine, medical equipment, livelihood and so on. According to statistics, the consumption rate of chinese titanium products was42.59%in2010, which was about one third of the worldwide consumption, and the consumption rate of Titanium alloy rod was16.60%, which is slightly less than that of sheet and pipe products. Considering its character of high deformation resistance, narrow deforming temperature zone, expensive cost, as well as small-batch and multi-variety, it is not suitable for producing titanium alloy rod by using large-scale production equipments and process for producing iron&steel, which could cause many quality defects such as folded and surface scratch etc. Therefore, using multi-roll mill for producing titanium alloy rod instead of two-roll mill is becoming a tendency.In view of this, Taiyuan university of science and technology proposed to produce titanium alloy rod with three-roll Y-type mill. Compared with two-roll mill, this process has advantages of metals forced uniformly, high deformation efficiency, compact structure and short flow. However, it is difference in deformation features between titanium alloy and common metals, there is no empirical data could be used for reference in rolling technical parameters. In the rolling process, reasonable pass system, rolling temperature, rolling velocity, and filing coefficient etc, which is applicable for rolling Titanium alloy with three-roll mill, are the key factors to achieve smoothly the continuous rolling.In this paper, take TC4alloy as the study subject, the hot deformation behavior has been analyzed for different temperature and strain rate. And the constitutive equation of TC4alloy has also been established. The optimal zone of rolling process is determined on the base of hot processing map. The key factors impacting the pass filling rate have been analysed. The model of filling coefficient has been established for rolling TC4alloy rod with "flat triangle- round" pass system. At last, rolling test is carried by three-roll Y-type mill, and the structure and mechanical property of TC4rod production have also been analyzed. Main contents are as follows.(1) This study conducts compression tests on TC4alloy by Gleeble-1500thermal simulator and the flow stress values are obtained at the temperature(℃) of800、825、850、875、900、925、950、975、1000、1025、1050, and the strain rates (s-1) of10、1、0.1、0.01、0.001. Then, flow stress curves of TC4alloy during high temperature deformation have been plotted, and the flow stress equation has also been established.(2) According to the data of thermal simulating test, the processing maps of TC4alloy at different strain have been plotted, which is based on the theory of Dynamic Material Model. The stability zone of hot processing, the optimal rolling temperature and the optimal strain rate have been determined, which provide theoretical basis for the process parameters of titanium alloy rod with three-roll Y-type mill.(3) Combining orthogonal experiment with ANSYS FEM, the major factors of influencing pass filling coefficient have been analyzed. And mathematical model of pass filling coefficient for rolling TC4alloy rod with "flat triangle-round" pass system has been established. The preliminary relationship between elongation coefficient and filling coefficient has also been determined, and the precision of the model has been proved with three-roll continuous rolling test.(4) Take lots of TC4alloy rod produced by three-roll continuous rolling as the study subject, the microstructure and mechanical property have been analyzed under the appropriate experimental program. The results show that it could meet the using requirements of national standards. Therefore, it is further checked that titanium alloy rod produced by three-roll Y-type mill is feasible. |
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