For the effect of compaction pressure of tungsten copper electrode hardness, the pressure is suddenly increased in the beginning, the hardness of tungsten copper electrode can be increased 10-20HB. While when the pressure rises to a certain degree, the hardness is almost unchanged, despite the increasing pressure. As the result of the pressing pressure is relatively small, the powder body is pressed into blank, which decrease the porosity rapidly and improve the density of tungsten copper electrode remarkably. But the contact area among the particles is still small so that strength increase is slower.

When the pressing pressure is greater, the particles can only increase contact area and reduce the porosity by elastic plastic deformation so that the density increases smoothly. However, due to the distance of particles reduce, the contact area increase, interaction force of atoms are emerging, which the strength of the rapidly improved. When the pressing force climb to a certain degree, the density and hardness of pressed compact is maximum, it will not change no matter how the pressure changes.

More information about pressing process effect on tungsten copper electrode properties, click here:

http://news.chinatungsten.com/en/tungsten-information/80252-ti-10309 
http://news.chinatungsten.com/en/tungsten-information/80294-ti-10312 
http://news.chinatungsten.com/en/tungsten-information/80295-ti-10313

In last part we know that as tungsten carbide wood working drill bits, countersink bits are used to counterbore holes, while bi-metal hole saws have a tungsten carbide edge as well as a diamond one. In this part we go on to introduce more types of wood working drill bits.

10. Plug Cutter

A plug cutter bores holes in wood, creating wood plugs for use in concealing recessed fasteners.When screw holes are drilled with carbide tipped countersink bits, the drilling creates a deeper hole enabling the screw head to be inserted below the surface. This allows a plug to be inserted into the piece and then sanded down creating a flat and clean surface.

11. Step Bit

A step bit is designed primarily for drilling in thin — up to 1/4 inch — metal, but will work with wood. The stepped design allows you to use a single bit to drill holes with different diameters. Often the diameter of each step is etched into the bit. You can also use this type of bit to deburr holes, clearing away waste material.

(The end This article is divided into several parts and this is part 6, for part 5 please refer to http://news.chinatungsten.com/en/tungsten-information/80346-ti-10356)

In last part we know that as tungsten carbide wood working drill bits, twist bits have spiral flutes for removal of chips, and a hole saw is used for cutting larger holes with pilot bit for positioning. In this part we go on to introduce more types of wood working drill bits.

8.Bi-metal Hole Saw

A bi-metal hole saw cuts through wood and metal. A hole saw with a tungsten carbide edge works on heavier materials such as ceramic tile and masonry. A hole saw with a diamond edge also works on tile and masonry, but cuts faster than carbide models.

9. Countersink Bit

 A countersink bit — also called a screw pilot bit — is a specialty bit for drilling in wood. In a single action, the bit can drill pilot, countersink and counterbore holes, allowing you to countersink a fastener and install a plug over the fastener head.

(To be continued. This article is divided into several parts and this is part 5, for part 4 please refer to http://news.chinatungsten.com/en/tungsten-information/80343-ti-10355; for part 6 please refer to http://news.chinatungsten.com/en/tungsten-information/80349-ti-10357)

In last part we know that as tungsten carbide wood working drill bits, a spade bit has one or two spade shaped points, while a forstner bit is used to create flat-bottomed holes.In this part we go on to introduce more types of wood working drill bits.

6. Twist Bit

A twist bit is the conventional and most common type of drill bit not only for wood working use at home, but also for many other kinds of work, such as metal machining industry. It works for general-purpose drilling in wood, plastic and light metal. Twist bits have spiral flutes to help remove the wood chips easily.

7. Hole Saw

A hole saw drills large holes — such as for installing door hardware or creating a pass-through for wiring. A hole saw creates a plug of waste material; a cut-out in the side of the saw cylinder allows you to pry it out. Typically a hole saw attaches to an arbor or mandrel which includes a shank. The arbor also holds a pilot bit for centering and steadying the cutting blade. Some smaller hole saws have a built-in shank and don't use a pilot bit.

(To be continued. This article is divided into several parts and this is part 4, for part 3 please refer to http://news.chinatungsten.com/en/tungsten-information/80341-ti-10354; for part 5 please refer to http://news.chinatungsten.com/en/tungsten-information/80346-ti-10356)

In last part we know that as tungsten carbide wood working drill bits, auger bits and self-feed bits all have screw points to position the bits, but auger bits have large flutes to help remove chips, while self-feed bits don’t. In this part we go on to introduce more types of wood working drill bits.

4. Spade Bit

A spade bit bores large-diameter holes — up to 1-1/2 inches in diameter — in wood. It has a flattened blade with a sharp point that helps position and steady the bit. Some spade bits have points at the two edges that help create a neater hole and exit point.

5. Forstner Bit

A forstner bit bores smooth, clean holes in wood. You can use it to create flat-bottomed holes — such as for receiving dowels. If you need to bore through the work piece, it creates a neat exit hole. A point allows you to position the bit precisely on the work piece. Pull the bit out regularly to clear away chips and dust as you work. A hand-held drill typically won't give you the force or control you need to use a forstner bit, so a drill press is a better option.

(To be continued. This article is divided into several parts and this is part 3, for part 2 please refer to http://news.chinatungsten.com/en/tungsten-information/80239-ti-10316; for part 4 please refer to http://news.chinatungsten.com/en/tungsten-information/80343-ti-10355)

The volume shrinkage of tungsten skeleton infiltrated with increasing compacts after pressing force increases, after its infiltration volume shrinkage greater than shrinkage skimmed skeleton after sintering blanks. As the result of the main ingredient of compact is tungsten and a slight amount of copper-induced, when skimmed blank sinter at high temperature, volume shrinkage mainly by volume diffusion effects and some tungsten particles induced copper compacts pressing pressure, which is conducive mutual contact between the tungsten particles and the diffusion and sintering density improving

However, if the pressing pressure exceeds a certain limit, the tungsten particle volume shrinkage decreases. It occurs liquid phase sintering during copper-tungsten skeleton infiltration. By the action of capillary force, tungsten particles rearranges, and improves the density, the volume shrinkage caused much greater than the volume shrinkage by volume diffusion.

More information about pressing process effect on tungsten copper electrode properties, click here:

http://news.chinatungsten.com/en/tungsten-information/80252-ti-10309 
http://news.chinatungsten.com/en/tungsten-information/80294-ti-10312

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With the increasing pressure, the density of powder with same weight is increasing. This is due to the accumulation of powder loaded in loose, irregular surface friction generated between each other, the particles to each other to form a bridge arch effect. When pressure exerted, arch effect the destruction of the body powder, powder particles will fill the pores with each other, rearrangement occurs, increase the contact area, and displacement occurs inside powder body.

Therefore, in the process of powder formation, the increasing molding pressure makes the blank density increase. For the same particle size of infiltration sample, as the pressure increased, under the same conditions, which skimmed density, skeletal density have also been increased accordingly.

For the impact of tungsten copper alloy electrode volume change, the experimental data shows that the volume shrinkage skimmed blank with high-temperature sintering compacts after pressing pressure increases. When the pressing pressure is 410 MPa, the maximum volume contraction, and thereafter compacting pressure continues to increase, the volume shrinkage rate began to decline.

More information about pressing process effect on tungsten copper electrode properties, click here:

http://news.chinatungsten.com/en/tungsten-information/80252-ti-10309

Tungsten Copper Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-copper.com/
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email:sales@chinatungsten.com
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In last part we know that to obtain a prolonged tool’s life, tungsten carbide cutting tools are coated with layers of wear resistant materials via chemical vapor deposition in a vacuum furnace. We go on to explain PVC technology.

PVD-Physical Vapor Deposition

The inserts are mounted on racks so they are separated from each other. Each rack rotates and the whole assembly of racks revolves within the furnace, so every surface of the tungsten carbide cutting tools is exposed to the deposition process. The furnace is evacuated. Strong negative charge is applied to the tungsten carbide cutting tools. A piece of titanium, or titanium and aluminum is installed on the wall or floor of the furnace. The metal is vaporized by either an electric arc or an electron beam, liberating the positively charged metal ions. These ions are attracted to the negatively charged inserts. Nitrogen and methane are added as appropriate, to achieve the different types of coatings.

PVD coatings are typically about 2-4 microns thick. Different manufacturers use different numbers of layers. When the inserts are removed from the furnace they may be ground again, or directly packaged and shipped.

Tool manufacturers are meeting the pressures for ever increasing feeds and speeds, and the need for longer tool life and lower costs, by continually improving the designs of tungsten carbide cutting tools and developing better and better coating technologies.

 (The end -This article is divided into several parts and this is part 9, for part 8 please refer to http://news.chinatungsten.com/en/tungsten-information/80278-ti-10331)

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In last part we know that tungsten carbide cutting tools are obtained through a final machining process on carbide blanks, including grinding, cutting, drilling, milling and sawing, etc. But machining may not be the final step for some type of cutting tools, since thereafter they are usually coated with special layers of wear resistant materials for longer life and better cutting efficiency. We explain firstly CVD.

Coating

To prolong tool life under challenging cutting conditions, many types and combinations of coatings have been developed for tungsten carbide cutting tools. TiC layers were the first to be applied by CVD. Others followed like TiN, TiCN, Al₂O₃, AlON as well as combinations and permutations. They can be applied mainly in two ways: by chemical vapor deposition (CVD) or physical vapor deposition (PVD). Both types are applied in furnaces. Coated hardmetal is the dominant tool material for indexable inserts.

CVD-Chemical Vapor Deposition

For CVD, the coating is usually 5- 20 microns thick. Milling and drilling inserts usually receive 5–8 microns, as these operations require better surface finish, and they encounter more impact, so they require greater edge toughness. To apply a CVD coating, the parts are placed on trays and sealed in a furnace. The furnace is drawn down to a vacuum.

For each layer, the appropriate gases are introduced into the furnace, such as hydrogen, titanium tetrachloride, methane, nitrogen, aluminum chloride. A chemical reaction occurs, depositing the layer of coating on the inserts.

 (To be continued-This article is divided into several parts and this is part 8, for part 7 please refer to http://news.chinatungsten.com/en/tungsten-information/80277-ti-10330; for part 9 please refer to http://news.chinatungsten.com/en/tungsten-information/80279-ti-10332)

Tungsten Carbide Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-carbide.com.cn
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In last part we know that the blank of a tungsten carbide insert comes into form with enough density and mechanical properties by sintering process. When we finally get a sintered tungsten carbide blank, we will go on to the machining process.

Machining

Before any tungsten carbide blank can be used as a tool, it has to be machined into a specific shape with a certain cutting function. Machining is any of various processes in which a piece of raw material is cut into a desired final shape and size by a controlled material-removal process. The three principal machining processes are classified as turning, drilling and milling. Other operations falling into miscellaneous categories include shaping, planning, boring, broaching and sawing.

For example, after the tungsten carbide inserts are removed from the furnace and cooled, they are dense and hard. After a quality control check, the inserts are usually ground or honed to achieve the correct dimensions and cutting edge. Honing to a radius of 0.001″ is typical, though some parts receive a cutting-edge radius of half a thousandth or as large as 0.002″, and some are left “dead sharp” as sintered.

But most of tungsten carbide cutting tools are much complex than a carbide insert, so they shall be machined in many different ways by different machining equipments with various machining tools. The modern equipment is the CNC machining center in high efficiency and precision, which can produce a final tungsten carbide drill in a complete sequence from grinding, cutting, boring , drilling, end milling to deburring, etc. The finished drill can be put into use directly, or go to the last process:coating.

 (To be continued-This article is divided into several parts and this is part 7, for part 6 please refer to http://news.chinatungsten.com/en/tungsten-information/80276-ti-10329; for part 8 please refer to http://news.chinatungsten.com/en/tungsten-information/80278-ti-10331)

Tungsten Carbide Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-carbide.com.cn
Tel.: 86 592 5129696; Fax: 86 592 5129797
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