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Die Matching Guidelines - Four Steps of Drawing Die Matching and Calculation Method of Key Data

Summary: Wire drawing die matching is the work of determining drawing pass, die hole size and shape according to blank size and wire size during wire drawing. It is also called drawing procedure or drawing route formulation. It can be divided into single-pass drawing die and multi-pass drawing die. The main steps of drawing die include the following four steps: 1. Selecting blanks; 2. Determining the number of intermediate annealing; 3. Determining the number of drawing passes and the elongation coefficient of distribution passes; 4. Calibration of die matching. This paper introduces the steps and calculation methods of wire matching for circular and special section metal drawing.

Mould matching principle and calculation example of sliding wire drawing machine

Summary: Wire drawing die matching refers to the method of selecting each drawing die in our drawing process. There are two main points in reasonable die matching: one is machinery; the sliding wire drawing machine has its fixed pulling wheel speed ratio. The correlation number of 7.2mm copper rod to 1.6mm copper wire is calculated by calculating the die matching example of the real wire drawing machine.

Uses of various drawing dies. Detailed classification

See how you classify it? The purpose of drawing dies is to reduce the material to be drawn.

According to size: micro-hole drawing die (inner hole size below 0.2), conventional drawing die.

According to the material of wire drawing die: diamond drawing die (natural diamond and artificial diamond, also known as polycrystalline drawing die), generally used for drawing small size wire and cable; carbide drawing die (YG3, YG6, YG8, YG10 and many other brands), mainly drawing large specifications of steel, copper, aluminum, and other products.

According to the materials and products drawn, they can be divided into ordinary drawing die, aluminium clad steel drawing die, prestressing steel wire drawing die, wire rope drawing die, steel cord drawing die, welding wire drawing die, welding rod drawing die, wire drawing die and so on. After using tungsten carbide steel wire drawing die for a period of time, its internal parts will gradually wear out and be damaged, resulting in the reduction of working performance and accuracy of the carbide wire drawing die. Due to carelessness of operators and improper maintenance and use, the tungsten steel wire drawing die will be damaged or the product quality will decline, and even cause shutdown. How to eliminate and avoid these failures? The number of cemented carbide die fitters is required to master the relevant die repair technology, so that failure can occur at any time, can be handled and repaired at any time, so that it can resume normal use as far as possible, and has given full play to the maximum potential of the die.

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Starting in 1893, German scientists used tungsten trioxide and carbon heated together in an electric furnace to a high temperature to make tungsten carbide, and tried to use their high melting point,High hardness and other characteristics to make drawing die, etc., in order to replace the diamond material.ButWC spraying powderhas not been used in industry because of its high brittleness, easy cracking and low toughness.

In the 1920s, German scientist Karl Schroter found that pure tungsten carbide could not adapt to the drastic stress changes formed in the drawing process. Only by adding low-melting metal into WC could the roughcast have certain toughness without reducing its hardness.

Schroter first proposed in 1923 the patented method of powder metallurgy, in which tungsten carbide is mixed with a small amount of ferrous metals (iron, nickel, cobalt), then pressed into shape and sintered in hydrogen at temperatures above 1300 to produce a hard alloy.

So far, the development oftungsten carbide sprayingpowdergenerally spans three stages. The first phase consists of powders and wires with metals and alloys as the main components, including aluminum, zinc, copper, nickel, diamond and iron metals and their alloys. These materials are made into powders, produced by primary grinding methods such as crushing and mixing, and manufactured by drawing wire or alloy wires of a certain diameter. These materials are mainly used in flame powder spraying, line spraying and arc spraying processes. Coating function is relatively simple, general corrosion resistance, wear resistance, small application surface; The second phase began in the mid-1950s. It has been found that it is necessary to improve the spraying process of tungsten carbide to obtain a more wear-resistant coating in order to solve the problem of mass wear in industrial equipment. After several years of efforts, the introduction of self-fusion alloy, the development of flame spray welding process. This is known as "hard surface technology". Self-fusion alloy is made by adding B, Si and Cr into the metal of Ni, Co and Fe groups, which can form eutectic alloying elements and antioxidant elements with low melting point. After tungsten carbide is sprayed, it is heated and remelted to obtain a hard coating. This technique was inspired in part by the welding surface treatment process.

Thanks to their high hardness, high metallurgical bonding and excellent oxidation resistance, these coatings have taken a big step forward in terms of wear resistance and oxidation resistance. The appearance of self-fusion alloy greatly promoted the development of tungsten carbide spraying technology. Another technological breakthrough at this stage is the emergence of plasma spraying equipment. Plasma flame up to 10,000 degrees, almost all materials can be sprayed. As a result, people began to think and develop a series of ceramic materials and metal ceramic materials. In fact, only after the mid-1970s, after the 8th international thermal spraying conference held in Miami in 1976, with the rapid development of the aviation industry, these materials really found a way to be applied, and high-performance, are gradually emerging. Technical wear-resistant, high temperature resistant, anti-gas corrosion and heat insulation surface engineering coating materials, so that thermal spraying technology from the simple maintenance workshop began to enter the aerospace and aircraft and other high-tech industries, and solve the headache of many metallurgical engineers. Not only did aircraft designers worry about the technology dropping planes from the sky, but since then, aircraft engines with more than 100 parts have been included in the specifications and must be sprayed with tungsten carbide to meet the designer's requirements. In the third stage, a series of composite powders and self-adhesive primary spraying powders appeared in the mid-1970s. It was not until the 1980s that sandwich lines were introduced to the market as arc sprayed materials.

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Using the parallel light projection method and the high precision linear CCD as the measuring sensor, combined with the mechanical scanning method, the hole diameter of the drawing die nibs was quickly detected. The circuit design of anti - spot interference in CCD aperture detection is proposed.

High-speed wire drawing production line is an important production equipment in the metal products industry. The quality of each process in wire-drawing production depends on whether the aperture of the wire-drawing die in the process is qualified. The axial section of the die hole is shown in figure 1, which is composed of four parts: inlet area, working area, sizing area and outlet area. Die diameter is the diameter of the specified diameter zone. Because the die hole is a cone Angle change hole, it is difficult to directly measure its minimum diameter, currently in the metal products industry is usually put silicone injection die hole to silicon gel solidification and then pull out, through the measurement of silicon punch die to obtain the die diameter. This kind of measurement method has low efficiency and is not suitable for the requirement of mass production. The range of the instrument:Φ 2 ~ 10 mm, accuracy < 0.01 mm.

The instrument adopts the method of parallel light projection and USES the high-precision linear CCD as the measuring sensor to extract the dimension information of thedrawing die nibshole. As shown in FIG. 2, the light source 1 forms parallel light through the condenser 2, the light column 3 and the collimating lens 4. Under the irradiation of parallel light, the wire-drawing die hole is imformed on the photosensitive surface of CCD through the imaging objective 6 and the light column 7. Optical system using remote fangyuan's heart light path, lighting and material can be reduced when installing drawing die sizing with position deviation, the measuring error caused by the light source to choose 6 v, 25 w halogen tungsten lamp step-down use, in order to improve the life and collimating mirror, choose standard photographic lens imaging lens, CCD and the use of Toshiba TCD106C, 5000 photosensitive pixels, center distance of adjacent pixels of 7 microns, the total size of 35 mm.

Measuring aperture with linear CCD is different from measuring diameter of outer circle. If the axis of measured rod and optical axis of measuring system are perpendicular to each other, the outer diameter can be measured by projection method. When measuring the inner diameter, the axis of the measured hole must be parallel to the optical axis. After the hole passes through the optical path imaging, the linear array CCD cannot directly measure the aperture. What the CCD cuts is the string of the hole. As long as the sampling frequency of CCD and the motion speed of the mechanical scanning mechanism are reasonably set, the scanning error can be controlled within the range that does not affect the accuracy.

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In order to improve the surface hardness and wear resistance of parts, a layer of tungsten carbide wear-resistant coating was applied on 45# steel by vacuum melting method. Hardness distribution and wear resistance change data ofwear-resistant coating for WC spraying powder at different depths were obtained through microhardness tester and wear test. The results show that the hardness of the diffusion layer of the coating is the lowest, and the hardness of the coating is higher than that of the matrix and the diffusion layer. In the condition of dry friction, the outer layer of the coating has the best wear resistance, the middle layers have the same wear resistance, and the coating near the diffusion layer has the worst performance.

Wear is one of the three main failure forms of materials, it is very huge economic losses, adhesion wear is one of the most common forms of wear, its development is very fast, easy to make parts or machine accident, causing huge losses. Wear failure of all kinds of parts caused by adhesive wear accounts for about 15%, and one of the main factors affecting the solid material adhesive wear is the hardness of the material, for the friction pair material hardness, the higher the hardness of the material, the better the wear resistance, therefore, the study of the hardness and wear resistance of parts material has important practical significance. In addition, the use of surface engineering technology, can make the material surface is not get it and hope to have a special performance (such as requirement surface wearability, heart good toughness), and the surface layer is very thin, material very little, high performance price ratio, saving material and saving energy, reducing environmental pollution, is an important measure to realize the sustainable development of the material. It is in this context that this paper attempts to make some research on the hardness and wear resistance of WC wear-resistant coating prepared by vacuum melting and burning method by means of test.

Sample preparation

Nickel-based tungsten carbide alloy powder fn15-wc35 and Ni45B were mixed in a ratio of 3:1 (mass ratio). Then saturated turpentine was added. The mixed WC spraying powder was prepared into paste for later use. Powder composition is shown in table 1. Clean the 45 steel surface to be coated with kerosene and dry it in an electric oven to check for defects in the abrasion resistant coating. If there is insufficient coating or coating loss, be sure to reapply, to ensure that the coating is relatively flat, there can be no defects. Coating is good and then into the oven for drying, baking temperature of 110degrees, drying time should be greater than 8 h, make not easy peeling off coating.

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The rapid development of high technology requires new materials with superior properties, and puts forward higher requirements for the hardness, strength and wear resistance of materials. Tungsten carbide base ultra fine cemented carbides have showed excellent mechanical properties, when WC spraying powder grain size decreases to 0.5 mu m, alloy shows excellent comprehensive performance, especially of ultrafine alloy treated by HIP, due to eliminate the residual pore in the alloy, the alloy properties (tensile strength) was further improved. There are many methods to prepare ultrafine tungsten carbide powder, but they can be divided into chemical method and mechanical method. Chemical methods mainly include spray heat transfer, organic salt thermal decomposition, one-step reduction carbonization, etc. The mechanical methods include high energy ball grinding, vibration ball grinding and mechanical alloying. Israeli g. r. graen-muginstein et al. obtained nanometer tungsten carbide powder with powder size of 0.6 m after 300h ball grinding, and dry grinding powder size was more uniform (5 ~ 10nm), while wet grinding powder size was wider (1 ~ 50nm). In this study, the submicron tungsten carbide powder was prepared by vibrating ball milling method.

Ultra-fine grain cemented carbide has high hardness and high strength, and is widely used in the manufacture of microdrill bits, dot matrix printer needles and precision tools for the drilling of integrated circuit boards. Ultrafine WC sprayingpowderis an important raw material for the preparation of ultrafine cemented carbide. At present, the reports of preparing nanometer, ultrafine tungsten carbide powder, or the way of the composite powder is more, there are mainly tungsten oxide reduction carbonization method (that is, the traditional process), directly carbonized tungsten oxide method, plasma chemistry carbonation method, halide tungsten carbide method, since the reducing amine salt, high frequency plasma method, gas solid instead should method, freeze drying, etc. These methods, the traditional process is simple and easy, reasonable, stable and reliable, large production capacity and advanced products of good quality, low cost and efficiency higher advantages, and is closely related with tungsten carbide production in our country,whichis a kind of conform to China's national conditions, more province industrial production method, literature, points out that the traditional process made BET size is less than 0.2 microns ultrafine tungsten carbide powder as the U.S. DOW company is the quality of the production of the tungsten carbide powder. However, other methods still have disadvantages such as complicated process, high production cost, low efficiency and many impurities, which are suitable for industrial scale production.

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