Tungsten copper alloy is an alloy of tungsten and copper. The copper content of common alloys is 10% to 50%. The alloy is made by powder metallurgy, has good electrical and thermal conductivity, good high temperature strength and certain plasticity. At very high temperatures, such as above 3000 ° C, copper in the alloy is liquefied and evaporated, which absorbs a large amount of heat and reduces the surface temperature of the material. So this kind of material is also called metal sweating material.
Tungsten copper alloy combines the advantages of metal tungsten and copper. Among them, tungsten has a high melting point (tungsten melting point is 3410 ℃, copper melting point is 1080 ℃) and high density (tungsten density is 19.34g / cm3, copper density is 8.89g / cm3). Copper has superior electrical conductivity and thermal conductivity. Tungsten copper alloy (composition generally ranges from WCu7 to WCu50) has a uniform microstructure, high temperature resistance, high strength, arc ablation resistance, and high density; moderate electrical and thermal conductivity properties, and is widely used in military high temperature resistant materials. , High-voltage switch electrical alloys, electro-machining electrodes, microelectronic materials, as parts and components are widely used in aerospace, aviation, electronics, power, metallurgy, machinery, sports equipment and other industries.
Defects in the machining technology of
tungsten copper alloy materials
Tungsten-copper alloys not only have the high strength, high hardness, and low expansion coefficient of tungsten, but also the high plasticity and good electrical and thermal conductivity of copper, which cause problems such as difficult parts cnc machining, high scrap rate, and large tool waste. As shown in Figure 1, during the machining of parts, the tap breakage rate is high, the wear is fast, and the inspection of finished products often results in unqualified parts with large ratios. The reasons for the failure are mainly the tapered outer cylindrical surface, the small diameter internal thread of the part (below M3 and M3), and the unqualified plug gauge, which not only causes the entire batch of parts to be repaired, but also the parts are prone to waste. Therefore, there is a great need to redesign and improve the machining method, cutting parameters and machining dimensions of the material.
Process analysis and improvement of tungsten copper alloy materials
1. The original process route was direct molding of the clamped bar material, the process route was unreasonable, and the process parameter was not selected properly, resulting in repeated tapers on the outer cylindrical surface of the part. Tungsten copper alloy material is an irregular round bar, which is prone to turbulence during turning, which causes taper during the machining of the outer cylindrical surface. The properties of tungsten copper alloy materials are special, such as the tools used, cutting methods and cutting If the parameters are incorrect, the taper will also be produced during the machining of the outer cylindrical surface. When cutting the tungsten copper alloy material, a relatively high temperature will be generated on the tool tip and the part. If it is not cooled in time, it will also cause a taper during the machining of the outer cylindrical surface. .
2. To avoid repeated taper when copper machining the outer cylindrical surface, it is necessary to adjust the cutting parameters and process methods of the part. The adjusted process route and parameters are as follows: ① Increase the roughing process of rough stock and ensure that the tolerance level of the bar is within H7; ② When machining parts, first select a tool and divide it into semi-finishing and finishing. During semi-finishing programming, the tool should be moved in an oblique manner to effectively avoid rapid wear of the blade tip due to repeated hammering on the same part of the blade during cutting. Due to the small diameter of the machined part, it is necessary to ensure the pointed end of the front end of the 1.5 cylinder. Improper selection of cutting parameters will cause the head of the part to break and cause the part to be scrapped.
3. According to the requirements of part material, dimensional accuracy and surface roughness, the calculation value of the surface roughness calculation formula Ra = 50f 2 / rε (f is the feed amount, rε is the radius of the tool nose arc) is based on the combination of the tool The recommended cutting parameter values and tungsten copper alloy material characteristics in the manual determine the cutting parameters of the tool (see Table 2) to avoid the occurrence of taper.
4. According to the characteristics of tungsten-copper alloy materials, the coolant uses water-solvent extreme-pressure cutting fluid. The specific heat of the cooling liquid is large, which can quickly remove the heat from the parts and chips. When the external cooling is performed, the cutting liquid should be aligned with the cutting edge, so that the machining area can be quickly and sufficiently cooled, and the effect of cutting heat on the cutting edge of the blade can be reduced. To avoid taper and extend tool life.