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Introduction and application of crucible powder high speed steel in the United States

application and promotion of powder high speed steel

I. production and advantages of powder high speed steel

there are two methods for manufacturing high speed steel, one is traditional ingot casting, the other is powder metallurgy. Traditional smelting and manufacturing are usually divided into secondary refining (eaf+lf+vd) or electroslag remelting (ESR). In the above methods, the slow cooling of molten metal causes uneven segregation of alloy and coarseness of alloy carbides, which affects the properties of high-speed steel. Although the subsequent heat treatment can change and refine the casting structure of the ingot and reduce the adverse effects, it can not eliminate the original casting structure, which has a negative impact on the physical and mechanical properties. In order to improve the quality of traditional high-speed steel, it is especially hoped that the carbide particle size of large-diameter high-speed steel can be fine and evenly distributed, so as to prevent the occurrence of segregation and make the horizontal and vertical mechanical properties uniform. In 1965, the United States began to develop the alloy powder process to meet this need, and Mr. Liu from the furnace company (crucible) produced a steel grade with uniform structure and no directionality. Up to now, powder metallurgy process has become the main method of manufacturing high-performance tool steel. The main principle of this process is that the high-temperature molten steel with mixed alloy components is atomized with high-pressure nitrogen when it flows out of the geotextile testing machine with the main specifications of 10kN, 20KN and 50kN, so that it can be rapidly solidified into uniform powder particles, and then screened and filled into the evacuated and sealed cylindrical steel cylinder for thermal pressure equalization (hip), so that the particles in the steel cylinder become completely dense materials, and then directly through traditional forging Rolled into products of different shapes, such as round bars, plates, sheets and wires, for industrial use

the main advantages of powder high speed steel in practical application are:

1. good grindability

2. small heat treatment deformation and good hardness uniformity

3. high toughness

4. good wear resistance

5. long service life and stability

due to the high technical requirements for the production of powder high speed steel, there are not many manufacturers of powder high speed steel in the world, mainly concentrated in the United States, Europe and Japan, The representative ones are crucible in the United States, Assab, soderfors, Erasteel, Bohler, DSS, ca r penter in Europe, and Hitachi, Daido, Nachi, Kobe in Japan. At present, there is no factory or company in China that actually commercializes the production of powder high speed steel, and all materials are imported from abroad. Therefore, in the impression of most Chinese users, powdered high-speed steel is only a vague concept. Only knowing that it represents a kind of high-speed steel with excellent performance and very expensive price, check whether the electromechanical operation of air circulation is a normal high-speed steel. Other understanding and application are not clear. As there are many varieties and grades of powder high speed steel, the author only describes the four types of steel commonly used by the American furnace crucible to provide customers with reference and selection

crucible, also known as "crucible steel", is the largest tool steel manufacturer and supplier in North America. The company pioneered the famous CPM process powder metallurgy tool steel. Its products are well known in the United States and Europe, and it is internationally recognized as the top tool and die manufacturing material

II. Classification and property comparison of high-speed steel tool steels

when selecting appropriate high-speed steel as cutting tools and dies, there are three important properties that must be carefully considered, namely, wear resistance, toughness and high-temperature hardness. Based on traditional m2, from the perspective of alloy elements, the three main development directions are:

(1) increasing vanadium (V) content to increase wear resistance

(2) increasing cobalt (CO) content, In order to improve the red hardness

(3) increase the content of vanadium and cobalt at the same time, and give consideration to the wear resistance and red hardness, the descriptions of the four powder high-speed steels compared with the traditional high-speed steels are shown in the table below

① CPM m4

cpm M4 is a powder high-speed steel which is widely used at present. Its performance and chemical composition are similar to asp23. It is a steel with good toughness and excellent wear resistance among high-speed steels at present. Generally speaking, the wear resistance of high-speed steel will increase with the increase of total alloy composition and maximum hardness, while the toughness will decrease with the increase of alloy content. Therefore, it will be improved on the basis of traditional high-speed steel m2. The wear resistance of CPM M4 depends on the hardness and carbide formation after heat treatment. CPM M4 increases carbon and vanadium in M2 to improve the wear resistance; At the same time, considering the toughness of the front Timken testing machine: the main shaft of the testing machine drives the test ring to rotate on the static test block, and uses the powder metallurgy process to improve the toughness, so that the toughness of CPM M4 is higher than that of the traditional M2 high-speed steel. According to statistics, its toughness is about times that of the traditional high-speed steel, and its wear resistance is also times. It has a wide range of applications. It is applicable to all kinds of stamping dies, embedding dies, powder forming dies and broaches, milling cutters, screw taps and shears in cutting tools. It can be applied to any parts that need wear resistance or strength and toughness. Based on the above two properties, CPM M4 is the most common high-speed high-quality steel with the best performance in the market. The hardness varies with different industries. It depends on the production needs. Generally, the hardness between HRC is the most appropriate

② CPM t15

cpm T15 is a tungsten based high-speed steel, which has very high hardness and wear resistance, and also contains cobalt, so it has good red hardness. It is suitable for hard to machine materials with heavy cutting, high cutting efficiency, large feed and high hardness, especially for replacing tungsten carbide parts; The wear resistance is about times that of traditional high-speed steel, and the toughness is about the same as that of M2. It is widely used in hobbing cutters, broaches, milling cutters, taps, stamping dies that need wear resistance, precision blanking, etc. In particular, it is the preferred material for the flat broach of superalloy turbine disk in the aviation industry, as well as the tap and die milling cutter for machining difficult cutting materials and quenched and tempered materials. Due to its high tungsten content and high wear resistance, it is suitable for precision stamping dies, especially when the workpiece is easy to wear or its service life is not long enough, it can be replaced with CPM T15. It is recommended to use it on stamping parts. The thickness of the workpiece should not exceed 2.5mm, and the general hardness is about HRC

③ CPM 10v

cpm 10V is not familiar in China, but it is widely used in European and American countries, especially in the United States. The most distinctive property is that its high wear resistance is being actively promoted. According to the experimental data of abrasion test, comparing CPM 10V with several other high-speed steels, it is worth mentioning that CPM 10V contains nearly 10% vanadium, so it produces VC carbide with the most wear resistance. Although the hardness is only about HRC60, it still has better wear resistance than CPM T15 (hrc67). It does not need to be processed to a higher hardness to achieve the purpose of enhancing wear resistance. This is mainly related to the form and quantity of carbides

generally speaking, the wear resistance of CPM 10V is times that of traditional high-speed steel. It is the best choice to replace tungsten carbide and other materials requiring high wear resistance; In particular, it is used for cutting blades, crusher blades, cutting and shearing edges, powder forming molds and other parts requiring wear resistance. It is generally recommended to use HRC hardness. Cpm10v mainly relies on the formation of carbides to increase the wear resistance. However, sometimes when it is used, it needs higher hardness to resist abnormal coarse-grained wear or better compressive strength, we will suggest to use CPM T15 instead

④ CPM 3v

cpm 3V is a new tool steel produced by the powder metallurgy process of LSP. It has high wear resistance and solves the problems of "angle collapse" and "fracture" of tools and dies. The toughness of CPM 3V is significantly higher than that of D2 and CPM M4, and is close to that of S7 impact steel. If the surface is coated, better wear resistance, hardness and thermal stability will be obtained. Use within the range of HRC hardness. CPM 3V is generally used to make stamping forming tools, punching dies and punches, industrial blades and shears, fine blanking and cold stamping tools. (end)

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