At the present, tungsten skeleton shaping includes compression molding, extrusion molding and injection molding, etc. For compression molding, the suppress pressure, velocity and holding time will directly affects the products. And the suppress is related to tungsten copper contents, tungsten content, Cu-induced content and the proportions of tungsten powder granularity, aspect ratio or shaping agent and mold discharging agent. On the premise of density of suppress blank, prolong the suppress time properly will reduce the elasticity of the stamper after divorcing.

There are few literatures about extrusion molding, some researchers use paraffin as plasticizer and study the choice of material, the amount and the process of wax-doped, pre-pressing, the temperature of extrusion molding, dewaxing and presintering, which plays an important role in extrusion molding of tungsten skeleton. And they thought when tungsten content of tungsten skeleton is 70% - 90%, the infiltration and other properties will be stable.

More infomation about tungsten copper electrode infiltration, click here:

http://news.chinatungsten.com/en/tungsten-information/79730-ti-10171 
http://news.chinatungsten.com/en/tungsten-information/79780-ti-10172 
http://news.chinatungsten.com/en/tungsten-information/79781-ti-10175 
http://news.chinatungsten.com/en/tungsten-information/79849-ti-10176

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Besides, mixed with light of Cu-induced powder will improve the corrosion ratio and the efficiency. Chinese scholars use 0.8-3.0μm tungsten powder for mixing, the result shows that despite small average granularity of tungsten powder, the density of sintering blank is still lower and the micro-structure is maldistributed.

Viewed from tungsten skeleton, it is a key of high density tungsten copper electrode manufacturing by infiltration. Due to tungsten (W) has high melting point, high hardness and low contraction, it is difficult to be machining and densifying, which becomes the major part of scholars study. The study of tungsten skeleton can be divided into two types, one is the shaping properties of tungsten skeleton, and the other is the sintering properties of tungsten skeleton.

More infomation about tungsten copper electrode infiltration, click here:

http://news.chinatungsten.com/en/tungsten-information/79730-ti-10171 
http://news.chinatungsten.com/en/tungsten-information/79780-ti-10172 
http://news.chinatungsten.com/en/tungsten-information/79781-ti-10175

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In part 15 we know that for tungsten carbide reamer, aluminum and brass have relatively better machinability than cast iron, plastics and stainless steel, and during reaming process proper lubrication helps cool tool, increase cutting speeds, remove chips and thus increases effect. And here we list the specific application ways of different cutting fluid for various work materials on which we use a tungsten carbide reamer to machine.

 (To be continued. This article is divided into several parts and this is part 16, for part 15 please refer to http://news.chinatungsten.com/en/tungsten-information/79784-ti-10204)

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In part 14 we know that versus high-speed steel reamers, tungsten carbide reamers are more expensive, but are can be applied to ream hardened materials with a longer life because of its much greater hardness. And here we explain shortly the work piece materials and lubrication during reaming process.

 (To be continued. This article is divided into several parts and this is part 15, for part 14 please refer to http://news.chinatungsten.com/en/tungsten-information/79734-ti-10199; for part 16 please refer to http://news.chinatungsten.com/en/tungsten-information/79785-ti-10205)

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Other experiment uses three different granularity of tungsten powder (8.7μm, 23.2μm and 65.2μm) for W-15Cu tungsten copper electrode. They thought different process parameters and tungsten powder granularity accounts for obturator or the changing of W-W adjacency rate, which has an effect on the density and resistivity. Nowadays, tungsten copper contacts made of 4-8μm (tungsten powder) granularity is widely used worldwide, which has good molding, contraction, low coefficient of thermal expansion and it is easily to be controlled in size or the porosity of tungsten blank.

In order to achieve that corrosion ratio and the efficiency of machining in electrical discharge machining (EDM) with tungsten copper electrode by diverse granularity of tungsten powder, researchers use 1.0-3.0μm five kinds of tungsten powder as tungsten copper electrode. It demonstrates that 2.0 μm average granularity of tungsten copper has better properties in 80WC-20Co tungsten carbide machining.

More infomation about tungsten copper electrode infiltration, click here:

http://news.chinatungsten.com/en/tungsten-information/79730-ti-10171 
http://news.chinatungsten.com/en/tungsten-information/79780-ti-10172

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Powder granularity: It stresses that tungsten powder granularity has an effect on tungsten copper electrode and other properties. Generally, the higher sintering temperature, the larger average granularity and the better strength of tungsten skeleton. However, if the granularity of tungsten powder exceeds a certain degree, the contact area among tungsten powder will be reduced and the tungsten powder can not be necking, which decreases the strength and hardness of tungsten skeleton and material.

Some scientists do some researches about tungsten powder granularity and volume fraction effects on density of tungsten copper electrode, they thought it depends on original grain size of tungsten powder and this effect will decrease by the increasing temperature of sintering temperature.

More infomation about tungsten copper electrode infiltration, click here:

http://news.chinatungsten.com/en/tungsten-information/79730-ti-10171

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In part 13 we know that the two major materials for reamers are high-speed steel and tungsten carbide, and tungsten carbide reamers are less affected by heat in machining process, but with so brittle and blunt cutting edges that they are not for light machinery. And here we list the different applications of the reamers made of the two categories of materials.

 (To be continued. This article is divided into several parts and this is part 14, for part 13 please refer to http://news.chinatungsten.com/en/tungsten-information/79733-ti-10198)

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In part 12 we know that the life of a tungsten carbide reamer can be up to 30,000 holes keeping size quality consistent if used properly and reamers are usually used with a drill press, lathes, machining centers or the similar. And here we explain two categories of materials used to build reamers.

Two materials for reamers

Like other cutting tools, there are two categories of materials used to build reamers: heat treated and hard. Heat treated materials are composed by different steels, most notably plain carbon (unalloyed, considered obsolete today) and high-speed steels. The most common hard material is tungsten carbide (solid or tipped), but reamers with edges of cubic boron nitride (CBN) or diamond also exist.

The main difference between both categories is that hard materials are usually unaffected by the heat produced by the machining process and may actually benefit from it. The down side is that they are usually very brittle, requiring slightly blunt cutting edges to avoid fracture. This increases the forces involved in machining and for this reason hard materials are usually not recommended for light machinery. Heat treated materials, on the other side, are usually much tougher and have no problem holding a sharp edge without chipping under less favorable conditions (like under vibration). This makes them adequate for hand tools and light machines.

 (To be continued. This article is divided into several parts and this is part 13, for part 12 please refer to http://news.chinatungsten.com/en/tungsten-information/79704-ti-10192; for part 14 please refer to http://news.chinatungsten.com/en/tungsten-information/79734-ti-10199)

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Infiltration is kind of process that uses the metal or alloy which has lower melting point than the product to fill in the pores of products in molten state. For tungsten copper electrode, copper solution has lower melting point and it fill in the porous tungsten skeleton, which has excellent density and strength so that tungsten copper material has better properties, such as thermal conductivity, electric conductivity and high hardness.

The process is: Tungsten powder (W) + shaping agent (or adds Cu-induced powder) → tungsten skeleton (suppressing + degreasing + sintering) → copper infiltration (Cu) → after treatment. And the most research focus on:

1. Powder granularity

2. Tungsten skeleton

3. Infiltration process

4. After treatment.

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In order to reach the theoretical density, researchers add some trace activated elements to improve liquid sintering. Compared with high-temperature sintering, liquid activated sintering decreases the sintering temperature, reduces the sintering time and improves the properties of tungsten copper electrode.

The research proved that Co and Fe is beneficial for improving the density of tungsten copper electrode, Ni and Pd neither. As a result of Co and Fe comes onto being W₆Co₇ or other metal compounds, it can promote rearrangement and spreading effect in the process of tungsten copper electrode activated sintering. However, Ni and Pd easily becomes unlimited solid solution with Cu, which is useless to sintering. The more specific data shows that when the content of Co is 0.35% and the temperature is 1300℃, tungsten copper products have better properties. The relative density of W-10Cu-0.35Co reaches 98-99% and the hardness is 300HV.

More infomation about tungsten copper electrodeliquid activated sintering, click here:

http://news.chinatungsten.com/en/tungsten-information/79706-ti-10164

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