Why more than 95% of dies in steel wire production is tungsten carbide dies?
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Why more than 95% of dies in steel wire production is tungsten carbide dies?
More than 95% of the dies for special steel wire production are tungsten carbide dies, followed by polycrystalline diamond dies. Natural diamond dies are usually used for stainless steel and high resistance electrothermal alloy wires (φ ≤ 0.30mm).
Next, let’s talk about the properties and uses of tungsten cobalt alloys
W-Co alloy has high hardness and good wear resistance. After grinding, it can obtain very low roughness, but it has low toughness, high brittleness, and tensile strength far lower than compressive strength. The properties of different grades of alloys are quite different, so it is very important to master the influence of various performance indexes on the service performance and select the proper grades.
(1) Density: density is an important mark to identify alloy grades. The density of tungsten cobalt alloy is between 15.3 and 12.9. With the decrease of carbide content, the density of different batches of the same brand should not exceed 0.08kg/m3.
(2) Hardness: according to the national standard, the hardness of knot alloy is expressed by HRA, and the hardness of tungsten cobalt alloy for wire drawing dies is generally between 85 ~ 93HRA /. The results show that the hardness decreases with the increase of cobalt content; the finer the tungsten carbide grains, the higher the hardness; the hardness of the tic alloy increases, and the hardness of the tungsten titanium cobalt alloy is higher than that of the tungsten cobalt alloy at the same cobalt content. In the process of drawing, even if the temperature rises to 500 ℃, the hardness of the alloy remains basically unchanged. When the temperature is higher than 500 ℃, the hardness of the alloy is basically unchanged. When the temperature is higher than 500 ℃, the hardness decreases slightly.
(3) Bending strength: bending strength is an important index to measure the toughness of tungsten cobalt alloy. At room temperature, the bending strength of W-Co alloy ranges from 1080 MPa to 2645 MPa. The bending strength increases with the increase of cobalt content and decreases with the increase of tungsten carbide content. Tungsten carbide has coarse grain and high bending resistance.
(4) Wear resistance: wear resistance refers to the ability of alloy to resist friction. There are many influencing factors. Generally speaking, tungsten carbide has high content, high hardness, fine grains and good wear resistance.
(5) Impact toughness: tungsten cobalt alloy is brittle, almost no plasticity, impact toughness and tensile strength are very small. Relatively speaking, the impact toughness increases with the increase of cobalt content.
(6) linear expansion coefficient: the linear expansion coefficient of tungsten cobalt alloy is much lower than that of carbon steel. In the range of 20 ~ 900 ℃, the linear expansion coefficient of tungsten cobalt alloy is (5 ~ 7.5) × 10-6 / ℃, and that of carbon steel is (11 ~ 13) × 10-6 / ℃. With the increase of cobalt content, the linear expansion coefficient increases, and the grain size has little relationship with the linear expansion coefficient.
(7) Thermal conductivity: high thermal conductivity is an important advantage of tungsten cobalt alloy, and its thermal conductivity is 2 times higher than that of high speed steel.
(8) Structure: including porosity, graphite inclusion content, and total length of dirt. W-Co alloy is formed by pressing and sintering powder materials. Pores, inclusions, and dirt are inevitable. However, the content of W-Co alloy will reduce the hardness, toughness, especially the impact properties.
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