# Impact of Die Radius in a Streamlined Die during Wire Drawing
## 1 Introduction  
The need to reduce the weight of cars has led to an increasing market demand for high-strength steel wire, rod, and bar products for automotive applications. Wire drawing is an essential process for manufacturing wire, rod, and bar products because the desired strength, shape, and size of the products are effectively obtained through the wire drawing process [1, 2]. There are four main issues in the wire-drawing industry when considering the manufacturing process. The first is to minimize the drawing energy for the process [3, 4]. The second issue is to reduce the strain inhomogeneity of the wire along the radial direction during the drawing process [5, 6]. The third is to decrease the occurrence of fracture rate, surface defects, and central bursts [7, 8, 9]. The fourth issue is to increase the die life [10, 11]. Although the properties of the drawn wire have complex interactions with several process parameters, three process parameters in particular can affect the abovementioned four issues during wire drawing: reduction of area (RA) per pass, die angle, and friction at the wire-die interface. Therefore, many researchers have investigated the influence of RA per pass [6, 12, 13], die angle [14, 15, 16], and friction at the wire-die interface [17, 18] on the drawing force, strain inhomogeneity, defects, and die life. Although the above three process parameters are highly correlated to each other, the die angle is a key parameter affecting the wire quality and manufacturing process because it primarily controls the contact length between the wire and die [5, 19, 20]. In addition, the die angle is relatively easy to control in the industrial plants. [PERSON] et al. [14] reported the effect of the die angle on the mechanical properties of a copper alloy during wire drawing. They showed that both the yield and tensile strength increased with increasing die angle, whereas the elongation decreased. [PERSON] et al. [19] showed the relationship betweenthe die angle, RA per pass, and friction coefficient using both experimental and numerical approaches. They found that the optimum die angle increased with increasing RA per pass and friction coefficient. [PERSON] et al. [16] investigated the effect of the die angle on the texture of a copper wire during the drawing process. They reported that the ratio of the (111) and (200) texture decreases with an increasing die angle, which means that a higher die angle leads to an increase in the randomly oriented grain structure. [PERSON] and [PERSON] [20] studied the influence of the die angle, RA per pass, and friction coefficient on the strain inhomogeneity of the wire during the process. Their results showed that the die angle and RA per pass strongly affect the stain inhomogeneity of the wire, and the effect of the friction coefficient plays only a minor role in determining the strain distribution of the wire. Most of the studies on the die angle effect during wire drawing have focused on a constant die angle, as shown in Figure 1a. Based on the author's experiences, the drawing process with a constant die angle explained above has some limitations in improving the quality of wire rod products [21]. Therefore, it is necessary to investigate the influence of curved or streamlined dies (Figure 1b-d) on the drawing performance to improve the drawability and wire properties. Figure 1e shows the variations in die angle along the drawing direction for the dies shown in Figure 1a-d. The die angle of the three streamlined dies changed along the drawing direction. There are several studies on the use of streamlined or curved dies during the wire drawing process [21; 22; 23; 24; 25]. [PERSON] and [PERSON] [22] reported that a sigmoid-shaped die provides better fatigue life and ductility of the specimen compared to the conventional die during the strip drawing process. They also showed that the sigmoid-shaped die has a larger interface between the specimen and die than the conventional die.