tungsten carbide steel tool material Basics

Carbide is the most widely used class of high-speed machining (HSM) tool materials, such materials are produced by powder metallurgy process, made of hard carbide (usually tungsten carbide WC) particles and the soft texture of the metal bond components. Currently, there crack chaser  are hundreds of different components of WC-based cemented carbide, the majority of them are used cobalt (Co) as a binder, nickel (Ni) and chromium (Cr) element is also commonly used binding agent, also can add other Some alloying elements. Why are there so many carbide grade? Tool manufacturers how to choose a particular cutting tool material correct? To answer these questions, let us look to make it an ideal tool material Carbide various characteristics.
Hardness and toughness
WC-Co cemented carbide in both hardness and toughness has a unique advantage. Tungsten carbide (WC) itself has a high hardness (more than corundum or aluminum oxide), and at elevated temperature hardness are rarely reduced. However, it lacks sufficient toughness, which is essential for the performance of the cutting tool. To take advantage of the high hardness of tungsten carbide and improve the toughness, people use the tungsten metal bonded together, so that the material is both far more than the hardness of high-speed steel, while able to withstand the cutting process, in most cutting force. In grinding cup wheels  addition, it can withstand high-speed machining heat generated by the cutting.
Today, almost all of the WC-Co cutting tool inserts are used and the coating, therefore, the base material may seem less important role. But in fact, it is WC-Co materials with high elastic modulus (a measure of the stiffness of, WC-Co at room temperature modulus of elasticity is about three times as high speed steel) for the coating of a substrate without distortion. WC-Co substrate can provide the necessary toughness. These properties are WC-Co materials, basic characteristics, but can also be produced when the carbide powder, by adjusting the material composition and material properties tailored microstructure. Therefore, the tool performance and suitability of a particular processing depends largely on the initial milling process.
Milling process
Tungsten carbide powder is through the tungsten (W) powder obtained by carburizing treatment. Tungsten carbide powder characteristics (in particular its size) depends on the particle size of raw material powders of tungsten and carburization temperature and time. Chemical control is also critical, the carbon content must be kept constant (close to the weight ratio of 6.13% of the theoretical value). In order to control the subsequent step by the particle size, can be added before the carburizing treatment a small amount of vanadium and / or chromium. Downstream of different process conditions and the type of final machining applications require the router bits  use of specific particle size of tungsten carbide, carbon content, vanadium content and chromium content in combination, a combination of these changes, can produce a variety of tungsten carbide powder. For example, tungsten carbide powder manufacturer ATI Alldyne company produced a total of 23 kinds of standard grades of tungsten carbide powder, and customized according to user requirements up to standard grades of tungsten carbide powder, tungsten carbide powder varieties more than 5 times.
When the metal bonded tungsten carbide powder and mixed together to produce a milled powder carbide grades, you can use a variety of combinations. The most common cobalt content of 3% to 25% (by weight), and the tool need to enhance corrosion resistance in the case of nickel and chromium needs to be added. In addition, you can also add other alloy components, and further improvement of the metal binding agent. For example, in the WC-Co cemented carbide adding ruthenium can be made without the premise of reducing the hardness significantly increase its toughness. Increase the binding agent content can also increase the toughness of the alloy, but will reduce its hardness.
Reducing the particle size of tungsten carbide hardness of the material can be improved, but in the sintering process, the tungsten carbide particle size must remain unchanged. Sintering, the tungsten carbide particles re-precipitated by dissolving process combines and growth. In the actual sintering process, in order to form a fully dense material, a metal binding agent to a liquid state (known as liquid phase sintering). By adding other transition metal carbides, including vanadium carbide (VC), chromium carbide (Cr3C2), titanium carbide (TiC), tantalum carbide (TaC) and niobium carbide (NbC), tungsten carbide particles can control the growth rate. These metals usually in the tungsten carbide powder and a metal binding agent is mixed with the milled added, although chromium carbide and vanadium carbide and tungsten carbide powder may also be formed when carburizing.
Recycled scrap carbide materials can be produced grades of tungsten carbide powder. Waste recycling and reuse of carbide in cemented carbide industry has a long history, is the entire economic chain of the industry is an important part, it helps to reduce material costs, conserve natural resources and avoid waste material and non- harm and disposal. Generally used cemented carbide by APT (ammonium paratungstate) process, or through a zinc recovery process for reuse after pulverization. The "regeneration" generally have a better carbide powder, predictable compactness, because of its surface area ratio is made directly through the carburization process of tungsten carbide powder is smaller.
Metal bonded tungsten carbide powder and mixing the milled processing conditions is crucial parameters. The two most common technique is ball milling and ultrafine grinding. Both processes can be uniformly mixed so that the milled powder, and to reduce the particle size. After the workpiece is pressed with sufficient strength to maintain the shape of the workpiece, and to an operator or robot can pick up the work operation, the milling usually also need to add an organic binding agent. The chemical composition of this combination is pressed into the workpiece can affect the density and strength. In order to facilitate operations, it is best to add high-strength bonding agent, but this will lead to suppression of lower density, which may result in lumps, causing a defect in the final product.
After the completion of milling, spray dried powder typically be generated from an organic binding agent that binds free flowing agglomerates. By adjusting the composition of the organic binder, these clumps can be customized mobility and charge density. By filtering out the coarse or fine particles, agglomerates can be further customized particle size distribution, to ensure that when the mold cavity is loaded with good fluidity.
Workpiece manufacturing
Carbide workpiece using a variety of craft molding methods. According to the workpiece size, shape, complexity level and production volume, most of the cutting blades are pressed by the top and bottom compression molded rigid mold. At each time of pressing, in order to maintain the consistency of the workpiece weight and size, to ensure the powder in the cavity (mass and volume) are identical. Powder flow mainly through the agglomerate size distribution and the characteristics of the organic binding agent to control. Loading the mold cavity by applying a powder 10-80ksi (one thousand pounds / square foot) of the molding pressure, the molded piece can be formed (or "blanks").