Carbide Introduction

The cemented carbide is a main component with a high hardness refractory metal carbide (WC, TiC) micron powder, with cobalt (CO) or nickel (Ni), molybdenum

(MO) is an adhesive, a powder metallurgy product which is sintered in a vacuum or hydrogen.

Ivb, Vb, Vib metal carbide, nitride, boride, etc. The structural, characteristics, and applications of the rigid gold are described below with carbides.

In a metal-type carbide formed of IVA, Va, VIA metal and carbon, due to small radius of carbon atoms, can be filled in the voids of the metal character and retain the metallic lattice form, forming a lifting solvent. Under suitable conditions, such solid solutions can continue to dissolve its composition elements until they are saturated. Thus, their composition can be varied within a certain range (for example, the composition of titanium titanide is changed between TiC0.5 to TiC), and the chemical formula does not meet the compliance rules. When the dissolved carbon content exceeds a certain limit (for example, TiC = 1), the lattice type will change, turn the original metal lattice to another form of metal lattice, at this time A renovated solvent is called a metallic replete.

Metal type carbide, especially IVB, Vb, and Vib metal carbide has a melting point of 3273k, wherein the carbide, tantalum carbide is 4160k and 4150K, respectively, and is a high melting point in the currently known substance. Most carbides have a large hardness, their microscopic hardness is greater than 1800kg? Mm2 (micro-hardness is one of the hardness representations, mostly used in cemented carbide and hard compounds, micro hardness 1800kg? Mm2 equivalent to Mo's Diamond a hardness 9). Many carbides are not easy to decompose at high temperatures, and antioxidant capacity is strong than its components. Titanium carbide is well thermally stabilized in all carbides, is a very important metal carbide. However, in an oxidative atmosphere, all carbides are easily oxidized at high temperatures, which can be said that this is a large weakness of the carbide.

In addition to carbon atoms, nitrogen atoms, boron atoms can also enter the gap of the metal lattice, forming a reinforcing solution. They are similar to the nature of the complex carbide, which can conduct electricity, heat transfer, high melting point, high hardness, and the brittleness is also large.

The substrate of the cemented carbide consists of two parts.

Part is hardened; the other part is bonding metal.

The hardening phase is a carbide of the transition metal in the periodic table, such as tungsten carbide, titanium carbide, carbon tantalum, and its hardness is high, and the melting point is more than 2000 ° C, and some even over 4000 ° C. Further, the nitride, boride, and silicide of the transition metal also have a similar character, or may act as a hardening phase in a carbide. The presence of a hardening phase determines that the alloy has good hardness and wear resistance.

Bond metals are typically ferrous metal, commonly used, cobalt and nickel.

When a hard alloy is produced, the selected raw material powder particle size is between 1 to 2 microns, and the purity is high. The raw material is ingredient according to the specified composition, and the alcohol or other medium is added to the wet ball mill, so that they are fully mixed, pulverized, dried, sieved to add a type of molding agent such as wax or glue, and then dry, over The mixture is prepared. The mixture is then granulated, the mixture is heated to approaching the bonding metal melting point (1300 to 1500 ° C), and the hardening phase forms an eutectic alloy with the bonded metal. After cooling, the hardening phase is distributed in the grid composed of bonded metal, closely together, forming a firm whole. The hardness of the hard alloy depends on the hardening phase content and the grain particle size, that is, the higher the hardening phase content, the finer the grains, the greater the hardness. The toughness of the cemented carbide is determined by bonding metal, the higher the bond metal content, the greater the strength of the bending.

In 1923, Germany's Schletel added 10% to 20% of the cobalt to binder, invented the new alloy degree of tungsten carbide and cobalt, which is the world's artificial production. First carbide. When cutting steel with this alloy, the blade will be worn quickly, and even the cutting cracked. In 1929, Schwarzkov added a quantity of tungsten carbide and tetanned carbide in the original ingredient, and improved the performance of the tool cutting steel. This is another achievement in the history of hard alloy development.

The cemented carbide has a series of excellent performance, heat resistance, strength and toughness, heat resistance, corrosion resistance, etc., especially its high hardness and wear resistance, even at temperatures at 500 ° C. There is still a high hardness at 1000 ° C. Cemented carbide is widely used as tool materials such as car knives, milling cutters, planer, drill, boring, etc., for cutting cast iron, non-ferrous metals, plastic, chemical fiber, graphite, glass, stone and ordinary steel, can also be cut Material resistant steel, stainless steel, high manganese steel, tool steel and other materials. Now the new type of cemented carbide tool cutting speed is equal to hundreds of times of carbon steel.

Cemented carbide can also be used to make rock drill tools, mining tools, drilling tools, measuring instruments, wear-resistant parts, metal abrasives, cylinder liners, precision bearings, nozzles, etc.

In the past two decades, coating hard alloys have also come out. In 1969, Sweden has successfully developed tonite Xu layer tool. The base of the tool is a tungsten cobalt cemented carbide or a tungsten cobalt carbonide, and the thickness of the titanium carbide coating is only a few microns, but compared to the alloy tool of the same number. The service life is extended by three times, and the cutting speed is increased by 25% to 50%. The fourth-generation coating tool has appeared in the 1970s, which can be used to cut the material that is difficult to process.

How is the hard alloy sintered?

The cemented carbide is a metal material made of such or more difficult metal carbides and adhesive metals, with powder metallurgy.