Generally, tungsten carbide is a kind of super-hard composite material consists of refractory metal carbide (e.g., WC, TiC), and the binder by transition metals or alloys (such as Fe, Co, Ni). It has high hardness, high strength, high melting point, excellent thermal hardness and wear resistance and corrosion resistance and other advantages. In the early 1920s, germen first adapted PM (Powder Metallurgy) to fabricate WC tungsten carbide, which put forward tungsten carbide widely used in aerospace, machinery processing, metallurgy, oil drilling, mining tools, electronic communications, construction, military and other fields.

Originally, tungsten carbide mainly used in drawing die and some wear parts manufacturing. And due to the technologies, process and performance improvements, it gradually plays an important role in metal cutting industries. With the further study, the researchers found that the smaller size of WC in granularity, the shorter mean free path of the binder Co, which has a dramatical increase in the hardness and strength of the alloys. Especially when the WC grain size reduces to about 100 nm, there will be a obvious breakthrough in the mechanical properties.

Today, in some emerging industries as well as some areas of difficult to machine materials fields, such as air super-alloy materials processing, electronics industry, using a wide range of printed circuit board (PCB) drilling, composite sheet metal processing, glass-fiber reinforced structural thermoplastic material, dot matrix printer head, the precision cutting of glass, etc., all need to be completed by nano tungsten carbide cutting tools with higher hardness and better strength. However, in the process of tungsten carbide densification, the growth of grains is an inevitable phenomenon. So in order to obtain nano tungsten carbide, we should synthesize finer powder in advance.

Wolfram has the highest melting point of all metals and is therefore also suitable for very high-temperature applications. It is also characterized by a uniquely low coefficient of thermal expansion and a very high level of dimensional stability. Tungsten rod is a kind of metal rod made of metal tungsten, at high temperatures, as a high melting point and low coefficient of thermal expansion material, so it is now widely used for support line, lead-in wire, printer pin, various electrodes and quartz furnace, filament, high-speed tools, automotive products and other industrial fields. Better wear resistance, higher toughness, better deformation and fracture resistance, results in a long life and good size accuracy. Except formed by metal tungsten powder, wolfram rod can also made through the process of the manufacturing of tungsten bar.

Tungsten bar can be divided into wolfram round bars and square bars, during the processing of swaging for tungsten rod, the obtained finished products would have some differences. When both of them are processing to 8mm in diameter, from the view of the sectional of metallurgical structure, the four corners of tungsten square bar are easy to form recrystallized structure under the conditions of processing temperature. If the follow-up process shall not be treated properly, it will result in the interior tissue of the wolfram rod is uneven, which is the main reason for defects and breaking of the following finished wolfram products. On contrary, after tungsten round bar is being stretched to 8mm in diameter, it still remains uniform tissue density. Nonuniform structure tends to cause internal defects of silk material, if uneven degree is very serious that it cannot be processed any more.

Observe hole distribution of this kind of metal rod after annealing, which can be used the scanning electron microscope, you will see the hole of the recrystallized structure correspond to four edges  are less, almost no orifice tube, but there are more holes in intermediate position of the wolfram rod. However, there are not exist recrystallized structure of the tungsten round bars, so its tissue distribution remains homogeneous state in follow-up processing. Internal tissue density distribution of tungsten bar has a great impact on the preparation of the following processes of tungsten rod and tungsten products. Therefore, the users should choose the right tungsten bars according to their own requirements.

Uneven tungsten billet sizes would cause the nonuniform resistance and large different temperature of each part of wolfram bar during a sintering process. Therefore, due to the different degree of sintering, the degree of combustion of the large size part is too low, but the small part is over-firing, which will cause the fuse. It is best to use the automatic charging machine and tracking piamater retractor and reasonable pressing parameter. So that it can ensure that diameter fluctuations of each part of the round billet can be stabilized within ±0.4mm after sintering.

At the beginning of it, we can see the difference between the square billet and round billet. On the universal testing machine, respectively compare to the compression strength and bending strength of green molding, pre-sintered compact, and isopressed compact. Pressed at the same pressure, the density of isostatic green compact is 1.15 times that of the green molded billet, and compression strength is 6.5 times, its bending strength is 2.7 times that of green die blanks. After pre-sintering, the density of square billet and round billet are approximately the same, compressive strength of round billet is 1.4 times that of square billet, and the flexural strength is 2.1 times. We can finger it out from here that round billet is not easy to be damaged during transport.

When swaging for both materials, it will be found that the surface of the tungsten square bar will often appear subtle cracks, if the swaging temperature rises, then the crack phenomenon would become more serious. Under the same conditions, the round tungsten bar doesn’t have this problem. This is because when the square tungsten is swaging, its edges, faces, and the center pat cannot receive strength evenly, and the degree of deformation also have a greater difference. The tungsten bar is the refined form of tungsten ore, which acts like silver grade tools. But armor and tools made of it will be classed as tungsten equipment. With the processing of tungsten elongated, and the part which did not receive would easy crack with the rest part. Uniform density, round face of cross-section and not forming agent of tungsten round bar eliminate defects of worked structure in a certain extent.