Abstract
A semi-dieless drawing technology has the advantages of producing a large deformation in a single pass and achieving high-precision dimensions of the finished products. However, instabilities can easily occur in a technique with a large amount of deformation, resulting in its failure. Herein, the deformation behavior of a wire during semi-dieless drawing is studied by finite element simulations. The instability mechanism of the semi-dieless drawing is proposed and validated by experiments. The experiments are conducted under the following conditions: a heating temperature of 950 °C; a distance between the die and heating coil of 20 mm; a feeding speed of 0.25 mm/s; a drawing speed range of 0.38–0.53 mm/s, and a die diameter range of 1.8–2.4 mm. The results show that by increasing the drawing speed or decreasing die diameter, the diameter fluctuation of the dieless drawn wire increases, and the semi-dieless drawing process easily becomes unstable. The diameter of the entering wire shows a fluctuating increasing trend owing to the variation in the drawing speed, which results in the instability during the semi-dieless drawing. The validity of the finite element model is verified by comparing the numerically predicted value and experimentally measured value of the drawn wire diameter.
Highlights
Ti-6Al-4V titanium alloy has good corrosion resistance, high-temperature mechanical properties, and biocompatibility; it has been widely used in aerospace, petrochemical, biomedicine, and other fields [1]
We examined the influence of the drawing speed vo′ and die diameter Ddie on the deformation behaviour in a semi-dieless drawing for a constant feeding speed vi
The fluctuation can be removed by the subsequent die drawing, as shown drawing speed of the dieless drawing section vc is entering speed as shown in inFigure
Summary
Ti-6Al-4V titanium alloy has good corrosion resistance, high-temperature mechanical properties, and biocompatibility; it has been widely used in aerospace, petrochemical, biomedicine, and other fields [1]. From Equations (2)–(4), it can be seen that the deformation stability in dieless drawing is closely related to the parameters of the material itself (strain rate sensitivity index m, work hardening coefficient γ, or work hardening index n) and process parameters (heating temperature T and strain rate ε). Kawaguchi et al [19] performed dieless drawing followed by die drawing, which eliminated the size fluctuation of the metal wire being drawn This drawing technology failed to completely utilize the residual heat in dieless drawing; the efficiency of energy usage was low. Liu et al [20] proposed a semi-dieless drawing technology, which combined the cooler in dieless drawing with a drawing die and made full use of residual heat in dieless drawing This new drawing technology achieved a large area reduction by performing dieless drawing and warm die drawing simultaneously, which could improve the diameter accuracy and surface quality of the finished products. A Ti-6Al-4V titanium alloy wire was used as the raw material to study the deformation behaviour in semi-dieless drawing by finite element (FE) simulations, following which the instability mechanism of the semi-dieless drawing was proposed
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