Cemented carbide is made by powder metallurgy with one or several refractory carbides (tungsten carbide, titanium carbide, etc.) powder as the main component, adding metal powder (cobalt, nickel, etc.) as a bonding agent, Alloy. It is mainly used to manufacture high-speed cutting tools and cutting tools for hard and tough materials, as well as cold work molds, measuring tools and high wear-resistant parts that are not subject to impact and vibration.
The characteristics of cemented carbide
(1) High hardness, wear resistance and red hardness
The hardness of cemented carbide can reach 86~93HRA at room temperature, which is equivalent to 69~81HRC. It can maintain high hardness at 900~1000℃ and has excellent wear resistance. Compared with high-speed tool steel, the cutting speed can be 4 to 7 times higher, the life span is 5 to 80 times longer, and hard materials with a hardness of up to 50HRC can be cut.
(2) High strength and elastic modulus
The compressive strength of cemented carbide is as high as 6000MPa, and the modulus of elasticity is (4~7)×105MPa, which is higher than that of high-speed steel. But its flexural strength is low, generally 1000~3000MPa.
(3) Good corrosion resistance and oxidation resistance
Generally, it has good resistance to atmospheric, acid, alkali and other corrosion, and is not easy to oxidize.
(4) The linear expansion coefficient is small
When working, the shape and size are stable.
(5) Shaped products are no longer processed or reground
Due to the high hardness and brittleness of cemented carbide, it is no longer necessary to cut or regrind after powder metallurgy forming and sintering. When special reprocessing is required, only electric machining such as electric spark, wire cutting, electrolytic grinding or special grinding wheel grinding can be used. cut. Products of a certain specification usually made of cemented carbide are brazed, bonded or mechanically clamped on the cutter body or mold body for use.
Commonly used cemented carbide：
Commonly used cemented carbides are divided into three categories according to their composition and performance characteristics: tungsten-cobalt, tungsten-titanium-cobalt, and tungsten-titanium-tantalum (niobium). The most widely used in production are tungsten-cobalt and tungsten-titanium-cobalt cemented carbide.
(1) Tungsten-cobalt cemented carbide
The main components are tungsten carbide (WC) and cobalt. The grade is represented by the code YG, followed by the percentage of cobalt content. For example, YG6 represents a tungsten-cobalt cemented carbide with a cobalt content of 6%, and a tungsten carbide content of 94%.
(2) Tungsten-titanium-cobalt cemented carbide
The main components are tungsten carbide (WC), titanium carbide (TiC) and cobalt. The grade is represented by the code YT, followed by the percentage value of the titanium carbide content. For example, YT15 represents a tungsten-titanium-cobalt cemented carbide with 15% titanium carbide content.
(3) Tungsten titanium tantalum (niobium) hard alloy
This type of cemented carbide is also called general-purpose cemented carbide or universal cemented carbide. The main components are tungsten carbide (WC), titanium carbide (TiC), tantalum carbide (TaC) or niobium carbide (NbC) and cobalt. The grade is indicated by the code YW followed by an ordinal number
Application of cemented carbide
(1) Tool material
Cemented carbide has the largest number of tool materials, which can be used to make turning tools, milling cutters, planers, drills, etc. Among them, tungsten-cobalt cemented carbide is suitable for the processing of ferrous and non-ferrous metals with short chips and the processing of non-metallic materials, such as cast iron, cast brass, bakelite, etc.; tungsten-titanium-cobalt cemented carbide is suitable for steel and other ferrous metals. Chip processing. Among similar alloys, those with more cobalt content are suitable for rough machining, and those with less cobalt content are suitable for finishing. The machining life of general-purpose cemented carbide for difficult-to-machine materials such as stainless steel is much longer than that of other cemented carbides.
(2) Mold material
Cemented carbide is mainly used as cold-working molds such as cold drawing dies, cold punching dies, cold extrusion dies, and cold forging dies.
The common feature of hard alloy cold heading dies under impact or strong impact wear-resistant working conditions is that the hard alloy requires good impact toughness, fracture toughness, fatigue strength, bending strength and good wear resistance. Usually select medium and high cobalt and medium and coarse grain alloy grades, such as YG15C.
Generally speaking, the relationship between the wear resistance and toughness of cemented carbide is contradictory: the increase in wear resistance will lead to a decrease in toughness, and the increase in toughness will inevitably lead to a decrease in wear resistance. Therefore, when selecting alloy grades, it is necessary to meet the specific use requirements according to the processing object and processing working conditions.
If the selected grade is prone to early cracking and damage during use, a grade with higher toughness should be selected; if the selected grade is prone to early wear and damage during use, it should be selected with a higher hardness and better wear resistance. . The following brands: YG15C, YG18C, YG20C, YL60, YG22C, YG25C From left to right, the hardness decreases, the wear resistance decreases, and the toughness increases; on the contrary, the opposite is true.
(3) Measuring tools and wear-resistant parts
Cemented carbide is used for wear-resistant parts such as wear-resistant surface inlays and parts of measuring tools, precision bearings of grinding machines, guide plates and guide rods of centerless grinding machines, and lathe centers.