Hard alloy is a kind of refractory carbide (tungsten carbide, titanium carbide, etc.) powder as the main component, adding as the adhesive metal powder (cobalt, nickel, etc.), through powder metallurgy and made of alloy. It is mainly used in the manufacture of high-speed cutting tools and hard and tough material cutting tools, as well as the manufacture of cold working molds, measuring tools and non-impact, vibration of high wear-resistant parts.
The characteristics of cemented carbide
⑴ High hardness, wear resistance and red hardness
The hardness of hard alloy can reach 86 ~ 93HRA at room temperature, which is equivalent to 69 ~ 81HRC. At 900 ~ 1000℃ can maintain high hardness, and has excellent wear resistance. Compared with high-speed tool steel, the cutting speed can be 4 ~ 7 times higher, the service life is 5 ~ 80 times longer, can be cut up to 50HRC hardness of hard materials.
⑵ High strength and elastic modulus
The compressive strength of hard alloy is up to 6000MPa, and the elastic modulus is (4 ~ 7) ×105MPa, which is higher than that of high speed steel. But its bending strength is low, generally 1000 ~ 3000MPa.
⑶ Good corrosion resistance and oxidation resistance
Generally good resistance to atmospheric, acid, alkali corrosion, not easy oxidation.
The coefficient of linear expansion is small
When working, the shape size is stable.
⑸ Formed products are no longer processed, reground
Due to the high hardness and brittleness of hard alloy, so powder metallurgy forming sintering is no longer cutting or regrinding, special reprocessing, can only use electric discharge, wire cutting, electrolytic grinding and other electrical processing or special grinding wheel. A product of a certain specification, usually made of hard alloy, that is brazed, bonded, or mechanically clamped to a tool body or die for use.
Common hard alloy
Commonly used hard alloys can be divided into three categories according to their composition and properties: tungsten-cobalt, tungsten-titanium-cobalt, tungsten-titanium-tantalum (niobium). Tungsten-cobalt and tungsten-titanium-cobalt hard alloys are the most widely used in production.
⑴ Tungsten and cobalt cemented carbides
The main components are tungsten carbide (WC) and cobalt, the brand is denoted by YG (" hard "and" cobalt "two characters in Chinese pinyin), followed by the percentage of cobalt content. For example, YG6 represents tungsten-cobalt hard alloy with 6% cobalt content, and wWC = 1-wCo = 94% tungsten carbide content.
⑵ tungsten-titanium-cobalt cemented carbide
The main components are tungsten carbide (WC), titanium carbide (TiC) and cobalt. The brand is denoted by YT (" hard "and" titanium "in Chinese pinyin), followed by the percentage of titanium carbide content. Such as YT15 said titanium carbide content wTiC = 15% tungsten titanium cobalt carbide.
(3) tungsten titanium tantalum (niobium) class of hard alloy
This kind of hard alloy, also known as universal hard alloy or universal hard alloy, is mainly composed of tungsten carbide (WC), titanium carbide (TiC), tantalum carbide (TaC) or niobium carbide (NbC) and cobalt. The brand is denoted by YW (" hard "and" Wan "two characters in Chinese pinyin) followed by an ordinal number.
Application of hard alloys
⑴ Tool Material
Carbide is used as the largest number of tool materials, can be made turning tools, milling tools, planer, drill, etc. Tungsten and cobalt carbide is suitable for black metal, non-ferrous metal short chip processing and processing of non-metallic materials, such as cast iron, cast brass, bakelite and so on; Tungsten-titanium-cobalt hard alloys are suitable for long chip processing of ferrous metals such as steel. Among the similar alloys, the ones with more cobalt content are suitable for roughing, while the ones with less cobalt content are suitable for finishing. The working life of general purpose cemented carbide is much longer than that of other cemented carbide for difficult materials such as stainless steel.
⑵ mold material
Hard alloy is mainly used for cold drawing die, cold punching die, cold extrusion die, cold pier die and so on.
⑶ Measuring tools and wear-resistant parts
Hard alloy is used for abrasive surface inlays and parts of measuring tools, precision bearings of grinding machines, guide plates and guide bars of centerless grinding machines, and wear-resistant parts such as lathe centers.
