1.Usually refers to various molds for drawing metal wires, as well as drawing dies for drawing optical fibers. The center of all drawing dies has a certain shape of hole, round, square, octagonal or other special shapes. When the metal is pulled through the die hole, the size becomes smaller and even the shape changes. Steel molds are sufficient when drawing soft metals (such as gold and silver). The steel molds can have multiple holes with different diameters.
The drawn steel wire (steel wire) generally uses a cemented carbide mold (Tungsten carbide nib). The typical structure of this mold is a cylindrical (or slightly tapered) cemented carbide core tightly embedded in a round steel sleeve. In the (case), the inner hole of the core includes a bell radius, an entrance angel, an approach angle, a bearing, and a back relief. For drawing non-ferrous metal wires, such as copper and aluminum, wire drawing dies similar to wire dies are also used. The shape of the inner hole is slightly different. The fine wire can be used for polycrystalline dies (man-made diamonds), and also for natural diamond.
Some of the soldiers in the ancient Chinese terracotta warriors and horses of Qin Shihuang could see metal wires on the stone armor, so it is estimated that someone had mastered the drawing technique at that time. In the Ming Dynasty book of Tiangong Kaiwu, we can see the needle making process, among which the drawing die is used.
First, the definition of drawing die
Usually refers to various molds for drawing metal wires, as well as drawing dies for drawing optical fibers. The center of all drawing dies has a certain shape of hole, round, square, octagonal or other special shapes. When the metal is pulled through the die hole, the size becomes smaller and even the shape changes.
Second, the type of drawing die 1. Steel molds—Steel molds are sufficient when drawing soft metals (such as gold and silver). There can be multiple holes with different apertures on the steel mold.
2. Cemented carbide mold—Tungsten carbide nib is generally used for drawing steel wire (steel wire). The typical structure of this mold is a cylindrical (or slightly tapered) cemented carbide core. The ground is embedded in a round steel case (Bell radius), entrance angel (Entrance angel), deformation angle (approach angle), sizing belt (bearing) and Exit angle (back relief).
3. Wire molds—For drawing non-ferrous metal wires, such as copper and aluminum, wire drawing dies similar to wire dies are also used. The shape of the inner hole is somewhat different.
4. Polycrystalline mold-Polycrystalline mold (man-made diamonds) can be used for drawing thin wires, as well as wire-drawing molds using natural diamonds.
Third, the use of drawing die
The wire drawing die is a very important consumable die for drawing wires by various metal wire manufacturers (such as wire and cable factories, steel wire factories, welding wire factories, etc.). The scope of application of wire drawing die is very wide. It is mainly used for drawing linear and difficult-to-machine objects such as bars, wires, wires, pipes, etc. It is suitable for drawing processing of metal and alloy materials such as steel, copper, tungsten, molybdenum, etc.
Since the cost of the wire drawing die accounts for more than 1/2 of the wire drawing cost, how to reduce the cost of the wire drawing die and increase its service life is an urgent issue for metal wire production units.
In order to improve the production competitiveness of foreign metal products industry, more and more attention is paid to the improvement of the quality of the drawing die and the manufacturing process. Starting from the improvement of the life of the drawing die, the material, structure, manufacturing process, manufacturing equipment and testing instruments of the drawing die have been studied. Systematic research has developed composite drawing dies, new drawing die materials, new surface coating technologies, and new hole design methods for drawing dies, which have promoted the development of wire drawing production in the world.
China is a major wire producer and its output ranks among the highest in the world. China’s wire drawing die manufacturing industry has developed rapidly since the 1980s. With the continuous improvement of wire drawing die manufacturing level and continuous improvement of production technology, China’s wire drawing die manufacturing technology has further developed, especially in the materials of wire drawing die, Great progress has been made in such areas as structure. But in general, there is still a big gap with foreign countries. Although the types of wire drawing dies produced abroad are similar to those of domestic ones, the materials and processes used are more advanced. The processing accuracy, durability and wear resistance of wire drawing dies are better than those of our products. Therefore, strengthening the management of mold making, improving the quality level of wire drawing dies, and promoting the progress of mold making technology are important issues currently facing the mold making industry.
2. Drawing die material
After decades of development, many new wire drawing die materials have appeared. According to the type of material, the wire drawing die can be divided into alloy steel die, hard alloy die, natural diamond die, polycrystalline diamond die, CVD diamond die and ceramic die. In recent years, the development of new materials has greatly enriched the application range of wire drawing dies and increased the service life of wire drawing dies.
(1) Alloy steel mold is an early material for wire drawing die manufacturing. The materials used to make alloy steel molds are mainly carbon tool steel and alloy tool steel. However, due to the poor hardness and abrasion resistance of the alloy steel mold, and the short life, it cannot meet the needs of modern production, so the alloy steel mold was quickly eliminated, and almost no alloy steel mold can be seen in the current production process.
(2) The cemented carbide mold is made of cemented carbide. Cemented carbide is a tungsten-cobalt-based alloy whose main components are tungsten carbide and cobalt. Tungsten carbide is the “skeleton” of the alloy, which mainly plays a hard and wear-resistant role; cobalt is the bonding metal and the source of alloy toughness. Therefore, compared with alloy steel molds, cemented carbide molds have the following characteristics: high wear resistance, good polishing, small adhesion, low friction coefficient, low energy consumption, high corrosion resistance, these characteristics make the carbide wire drawing Die has a wide range of processing adaptability, and has become the most widely used wire drawing die mold.
(3) Natural diamond is an allotrope of carbon, and the mold made with it has the characteristics of high hardness and good wear resistance. However, natural diamond is relatively brittle and difficult to process. It is generally used to make wire drawing dies with a diameter of 1.2 mm or less. In addition, natural diamond is expensive and scarce in supply, so natural diamond molds are not the economical and practical drawing tools that people eventually seek.
(4) Polycrystalline diamond is made by carefully selecting high-quality artificial diamond single crystals with a small amount of binders such as silicon and titanium, and polymerizing under high temperature and pressure conditions. Polycrystalline diamond has high hardness and good abrasion resistance. Compared with other materials, it has its own unique advantages: due to the anisotropy of natural diamond, during the drawing process, when the entire hole is surrounded by Under working conditions, natural diamond will wear preferentially at a certain position of the hole;
Polycrystalline diamond is polycrystalline and has the characteristics of isotropy, thereby avoiding uneven wear of mold holes and out-of-round mold holes. Compared with cemented carbide, the tensile strength of polycrystalline diamond is only 70% of common cemented carbide, but 250% harder than cemented carbide. In this way, polycrystalline diamond mold has more advantages than cemented carbide mold. . The wire drawing die made of polycrystalline diamond has good wear resistance, uniform bore wear, strong impact resistance, high wire drawing efficiency, and the price is much cheaper than natural diamond. Therefore, polycrystalline diamond dies are currently widely used in the wire drawing industry.
(5) CVD (chemical vapor deposition) coating wire drawing die is a newly developed new technology. The main method is to coat the diamond film on the carbide wire drawing die. Diamond film is a pure diamond polycrystal. It has the advantages of single crystal diamond’s smoothness and temperature resistance, as well as the abrasion resistance and low price of polycrystalline diamond. It has achieved good results in preparing wire drawing tools instead of rare natural diamond. Effect, its widespread use will bring new vitality to the wire drawing industry.
(6) High-performance ceramic materials have the characteristics of high hardness, good abrasion resistance, strong chemical stability, high-temperature mechanical properties, and difficulty in bonding with metals. They can be widely used in the processing of difficult-to-process materials.
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