![<?echo $_SERVER['SERVER_NAME'];?>](/template/twentyseventeen/skin/images/header.jpg)
Since the 1970s, the market share of high-speed steel tools has gradually been eroded by cemented carbide tools. However, in recent years, with the improvement of cutting performance of powder metallurgy high speed steel (P/MHSS) tools, the market share of high speed steel tools has rebounded. Compared with ordinary high-speed steel tools, powder metallurgy high-speed steel tools have higher hardness, better toughness and wear resistance. Therefore, in some applications (such as high impact, large cutting processing), powder metallurgy high speed steel Knives have a tendency to gradually replace solid carbide tools that are more brittle and prone to chipping under cutting impact.
The powder metallurgy high-speed steel manufacturing process was successfully developed in Sweden in the late 1960s and entered the market in the early 1970s. The process can add more alloying elements in high-speed steel without damaging the toughness or grindability of the material, so that it can be made with high hardness, high wear resistance, absorbable cutting impact, suitable for high resection rate processing and breaking. Continued cutting tools.
High-speed steel tool materials are mainly composed of two basic components: one is metal carbide (tungsten carbide, molybdenum carbide or vanadium carbide), which gives the tool better wear resistance; the other is distributed around the steel matrix, which makes The tool has good toughness and the ability to absorb shock and prevent chipping. When preparing ordinary high-speed steel, the molten steel is injected into the mold from the ladle, and it is slowly cooled and solidified. At this time, the metal carbide precipitates from the solution and forms a large agglomerate. The higher the alloy content added to the high speed steel, the larger the carbide agglomerates. When a critical point is reached, a very large carbide mass (up to 40 mm in diameter) can be formed. The critical point at which large carbide agglomerates appear varies slightly depending on the size of the ingot and other factors, but generally occurs when the vanadium carbide content reaches about 4%. By subjecting the ingot to subsequent processing such as forging and rolling, a part of the carbide agglomerates can be pulverized, but it is impossible to completely eliminate it. Although increasing the amount of metal carbide particles in the steel can improve the wear resistance of the material, as the alloy content increases, the size of the carbide and the number of agglomerates increase, which is extremely unfavorable for the toughness of the steel. Impact, because large carbide clusters can quickly become the starting point for cracking.
The preparation process of powder metallurgy high-speed steel is different from that of ordinary high-speed steel. The molten steel is not directly injected into the mold, but is blown into a nitrogen stream through a small nozzle for atomization, and the sprayed molten steel is rapidly cooled to Small steel particles (less than 1mm in diameter). Since the carbides in the aqueous steel solution are too late to precipitate and form a cluster during the rapid cooling process, the obtained carbide particles have fine and uniform distribution of carbide particles. The steel powder is sieved, placed in a steel drum, and the air in the middle of the steel powder is vacuumed to form a vacuum state, and then the steel powder in the steel drum is pressed and formed under high temperature and high pressure to obtain a density of 100. % of powder metallurgy high speed steel blanks. This preparation process is called hot isostatic pressing (HIPing) molding. The blank can then be subjected to subsequent processing such as forging, rolling, and the like.
The carbide particles in the powder metallurgy high speed steel prepared by the hot isostatic pressing process are very fine, and these carbide particles are uniformly distributed throughout the high speed steel matrix regardless of the alloy content.
Although the process details of different manufacturers for powder metallurgy high speed steel may be slightly different, the basic process principles (nitrogen atomization granulation and hot isostatic pressing) are the same. It is very important that this preparation process cannot be confused with the hot press sintering process (pressing and sintering the workpiece with steel powder heated to the melting point temperature). Although the two processes have similar names, the process principle is completely different. A typical hot press sintering process is to press a workpiece one by one in a mold, and a binder is usually added to the raw material powder, so that a microporous structure is formed in the sintered material.
With the powder metallurgy high-speed steel preparation process, steel producers can increase the metal carbide content in the steel without adversely affecting the toughness or wearability of the material. Although some people who prefer powder metallurgy high-speed steel like to call it a "hybrid" of high-speed steel and solid carbide, it is actually a high-speed structure with small-sized carbide particles and refined steel matrix particle structure. steel. However, it does combine the good toughness of high speed steel with the high wear resistance of cemented carbide.
Since the carbide particles in the powder metallurgy high-speed steel are fine and evenly distributed, the toughness is greatly improved compared with the ordinary high-speed steel having the same carbide content. With this advantage, powder metallurgy high speed steel tools are ideal for machining applications with high cutting impacts and high metal removal rates (eg flexing, interrupted cutting, etc.). In addition, since the toughness of powder metallurgy high-speed steel is not impaired by the increase in metal carbide content, steel producers can add a large amount of alloying elements to the steel to improve the performance of the tool material. Taking the tap as an example, since the tap cutting edge continuously contacts and separates from the workpiece during tapping processing, the cutting impact is large, so it is necessary to manufacture the tap with high-strength and tough grade of shatter-resistant steel, and at the same time, in order to improve the wear resistance of the tap, it is required. The carbide content in the tool material is high. The commonly used tap material is the ordinary high-speed steel grade M-2, and now it can be replaced by powder metallurgy high-speed steel grade M-4. The content of medium hard carbides in these two grades is about the same (M-4 is 8%, M-2 is 7%), but the high hard carbide content in the powder metallurgy high speed steel grade is much higher than ordinary high speed steel. (M-4 is 6%, M-2 is only 2%), so the wear resistance of M-4 tap is significantly enhanced, processing efficiency and tool life are improved, and the toughness of M-4 tap is also much better than M -2 taps are not easily broken during tapping.
The disadvantage of powder metallurgy high-speed steel is that it is more expensive, about 2 to 5 times that of ordinary high-speed steel (different grades are different). Therefore, tool manufacturers must balance the increase in tool performance with the additional tool manufacturing costs. For small and complex tools, the use of powder metallurgy high-speed steel is very cost-effective because the material cost is only a small part of the total cost of the tool. For large-size simple tools, the choice of powder metallurgy high-speed steel requires careful consideration. However, significant improvements in the grindability of powder metallurgy high speed steels often result in partial (or total) compensation for increased material costs.
The main factor affecting the grindability of steel is the content of vanadium carbide in steel. Since the hardness of vanadium carbide is higher than the hardness of alumina abrasive grains in the grinding wheel, when grinding ordinary high-speed steel with high vanadium content, abrasive grains It is easy to passivate, resulting in more grinding heat, faster grinding wheel wear and longer grinding time. The powder metallurgy high-speed steel has fine carbides and uniform distribution. Compared with ordinary high-speed steel, the loss of the grinding wheel is small, which can greatly shorten the grinding man-hour and save the grinding processing cost. Small and complex tools usually require a large number of precision grinding processes, ie their grinding/material-costratio ratio is high, so the increased material costs are easily recovered in the grinding process (even There is a surplus). While larger size tools require less grinding and a lower grinding/material cost ratio, improvements in material grindability typically only partially compensate for material cost increases. Although the economics of using powder metallurgy high speed steel varies depending on the manufacturing process of different tool manufacturers, in general, the improvement of the grindability of the tool material can reduce the grinding time by about 30%.
Today, powder metallurgy high speed steel tools have become a strong contender for solid carbide tools. Although the solid carbide tool has a high hardness and is brittle, it is often used for turning, and is not suitable for machining and roughing with large cutting impact. Because powder metallurgy high-speed steel contains a lot of hard carbide, its wear resistance can reach the level equivalent to the whole cemented carbide, and its toughness is better than the whole hard alloy, and it is more suitable for the tool and wear resistance. And tough cutting (such as tapping, end milling, etc.).
The latest advances in powder metallurgy high speed steel preparation technology have further enhanced its competitiveness. The application of electro-slag heating (ESH) refining process has great significance for powder metallurgy high-speed steel. The process removes almost all of the impurities in the steel, further improving the toughness of the material and significantly improving the chip's resistance to chipping. In addition, due to the reduction of impurities in the steel, the manufacturer can further increase the alloy content of the steel. For example, the vanadium carbide content of a certain powder metallurgy high-speed steel grade can reach 14%, while the maximum content of ordinary high-speed steel grade vanadium carbide is only about 4%. Although a large amount of alloy is added to the steel, it does not affect its toughness and grindability.
It should be noted that many powder metallurgy high-speed steel producers do not adopt process measures to improve material purity in order to reduce costs. The steel they produce may contain many impurities that cause micro-cracking of the tool. However, it is difficult to discern the quality of the product based on the product information provided by the manufacturer. The user must ask the manufacturer to explain the process measures for removing impurities, or further require it to provide detailed technology on the size of impurities in the steel. data.
The powder metallurgy process changes the material properties of traditional high-speed steel, especially with the newly developed purification technology, which enables powder metallurgy high-speed steel to achieve extremely high alloy content while maintaining its toughness. Therefore, the cutting performance of powder metallurgy high speed steel tools surpasses traditional high speed steel tools in almost all cutting fields, and is superior to solid carbide tools in high cutting rate and high impact cutting. Although its price is higher than that of ordinary high-speed steel, it can be compensated for by improving the performance of the tool, prolonging the life, and improving the wearability.
Concerned about surprises
Tag: high speed steel tool material powder metallurgy high wear resistance microporous structure
Previous: Tool material heat treatment process needs to be personalized Next: Ball chip high speed wire knife and one knife forming machine clip thread
Rhein Lighting has developed a line of the high voltage 2835 Led Strip Light which is perfect for home, office and outdoor decoration. The light strip has multiple colors such as white, red, blue, yellow, green and RGB etc. The strip light has clear PVC tubing, which is flexible, transparent and durable and it can be shaped, formed or bent in any angle to perfectly fit the space being decorated.
The led rope light has come with different options of lengths in a reel, which has 50ft, 100ft and 150ft. The 120v Led Strip Light can be cut in every 1.64ft/0.5m along the cutting marks, without damaging the rest strips.
The Led strip light is ETL certified, which is Eco-Friendly, No splash and UV, without mercury and no damage to human and environment.
Rhein Lighting is specialized in the design and manufacture of led panel downlight, led slim down light, backlit Led Panel Light, led rope light, led strip light, led plant light and Led Grow Light etc.
Led Strip Lights Home Depot,Phopollo Led Strip Lights,Led Strip Lights For Bedroom,Monster Illuminessence Led Strip
Rhein Lighting Technology Co.,Ltd. , https://www.rheinlighting.com