Known for their unique hardness, tool steels are used in the manufacture of cutting tools such as knives and drills, as well as in hot extrusion, stamping and plastic molds.
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Although the selection of tool steel seems to be very simple, this process requires trade-offs, which must be comprehensively considered from the characteristics of tool steel, process performance, production cost and specific applications.
Scientifically correct and reasonable selection of tool steel is the basis for ensuring the best performance, service life, safety and economy of the product. Selecting the best tool steel grade will depend on a variety of factors as follows.
Hardness directly reflects the material&#;s resistance to deformation. The hardness of tool steel is usually expressed by Rockwell hardness HRC.The application hardness of most tool steel is 60 to 62 HRC, and some will be as high as 66 HRC or above. The final application hardness depends on the steel grade.
Tool steels that undergo plastic deformation in service show insufficient hardness.For example, permanent bending of the blade in use, swelling of the end face of the punch and collapse of the surface of the die all indicate insufficient hardness.Since the deformation resistance of steel is directly related to hardness (independent of steel type). Therefore, the correct way to solve the deformation is to increase the hardness, or reduce the working load. At this time, changing the steel grade will not work unless the new steel grade can achieve higher hardness.
When the difference in hardness value is not large, the change in hardness generally has little effect on the wear life of tool steel. Different tool steels usually have the same hardness in use, but their wear life often varies greatly.
The toughness of tool steel is a kind of resistance that characterizes its resistance to fracture under the action of impact force or other stress.
Most tool steels are notch sensitive. Therefore, any small gap in the material will cause it to break under lower impact force.Therefore, in addition to the inherent characteristics of the material, notches, grooves, geometric changes and other small changes on the workpiece will reduce the impact resistance of the corresponding part.
In production, the loss caused by wear failure is usually less than the loss caused by ductile failure (fracture), because fracture failure is often unpredictable, usually interrupts production, and even brings catastrophic losses.Wear failure is generally gradual and it can often be corrected. Toughness failure is due to insufficient toughness of the material itself, or other reasons, such as heat treatment, lubrication method, or other working conditions.The toughness value can characterize the steel&#;s resistance to fracture but not its service life.
Wear resistance refers to the ability of a material to resist mechanical wear. The objects in contact with the material are workpieces, other tools and objects adhered to their surfaces (scale, metal shavings, etc.). Wear resistance is determined by the hardness of the steel and its chemical composition.
We usually intuitively believe that the wear resistance of high hardness tool steel is better than that of low hardness. However, at the same hardness, different steel grades have different wear resistance. For example, O1, A2, D2 and M2, even though their hardness is 60HRC, their wear resistance is not all equally excellent.
Facts have shown that under some working conditions, the wear resistance of low-hardness high-alloy tool steel is better than that of high-hardness low-alloy tool steel. Therefore, for wear resistance, the influence of other factors other than hardness must be considered, such as carbides, heat treatment processes, etc.
The above three factors,hardness and toughness can be regarded as the function of &#;enough is enough&#;. That is to say, as long as the performance of tool steel in this area is to prevent its failure in this area, it is enough, and it is not necessary to further improve these properties. However, wear resistance can be considered as a &#;never enough&#; function, that is, improving the wear resistance of the tool will increase its life. In order to increase tool life, the wear resistance of tool steel should be improved endlessly. Therefore, as long as other properties are not damaged, it is always beneficial for tool steel to improve wear resistance.
Tooling is a key component of any manufacturing project, both because they are a significant investment and a considerable influence on the overall quality of the manufacturing results. Tooling durability and longevity will depend on the application and the tool steel used to create the tooling. Below we take a dive into two different types of steel commonly used for tooling &#; tool steel and powder metal.
Choosing the right steel for your tooling will depend on several factors, including the conditions it will endure. Some questions must be answered to determine which will work for your application. Does it need a sharp edge? What type of heat treatment is required? Does it need to be abrasion resistant? Does it need to withstand impact? Will it be used at high speeds? Will it be used at high or low temperatures?
Tool steel refers to carbon and alloy steel used to make a wide variety of tooling. The alloying elements give them the necessary properties required for various applications. In general, tool steels offer a fairly high material hardness, toughness that makes it resistant to breaking or chipping, wear resistance, abrasion and erosion resistance, and good thermal properties. It comes in different grades that have their own properties that are impacted by the percentage of each alloy.
A-grade is air-hardened tool steel that respond well to heat treatment. They have great wear resistance and toughness. D-grade is a cold working steel with higher carbon content than W-grade but offers wear resistance and toughness. O-grade is an oil-hardened, cold-working tool steel. This versatile general-purpose steel has great abrasion resistance and high toughness properties. S-grade is shock-resisting, low-carbon tool steel with high toughness. It is resistant to shock at low and high temperatures. W-grade is water hardening and contains low-cost high-carbon steel with high hardness and fragility. It isn&#;t suitable for high-temperature use.
A2 is an air-hardened chromium alloy steel. This multi-purpose steel offers good toughness, intermediate wear resistance, and excellent dimensional stability in heat treatment. Tooling applications include dies, punches, shear and slitter blades, knurling tools, and more.
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A8 is an air-hardening tool steel that offers a combination of very good toughness, intermediate wear resistance, and excellent dimensional stability in heat treatment. A8 is often chosen for punches and dies that operate in the 55-60 Rockwell C hardness range.
Caldie is a chromium-molybdenum vanadium alloyed tool steel, which provides a combination of high toughness, good wear resistance, and dimensional stability on heat treatment. It is used in tooling that requires good chipping and cracking resistance and good wear resistance.
D2 is an air-hardening, high carbon, high chromium tool steel offering exceptionally high wear resistance properties. It provides an effective combination of wear resistance, toughness, and tool performance for a number of tooling applications, including rolls, punches, and dies for blanking, forming, trimming, and thread rolling.
D7 is an air-hardening, high carbon, high chromium tool steel with added carbon and vanadium for exceptional abrasion-resisting qualities. It was developed especially for applications involving extreme abrasive wear.
H13 is a 5% chromium, ultra-high strength air-hardened steel with higher content of molybdenum and vanadium. This combination provides a combination of excellent toughness and high wear resistance. It is often used in hot work tooling with applications such as inserts, cores, and cavities for dies, ejector pins, and nozzles.
M2 is a tungsten-molybdenum high-speed steel that offers good red hardness, toughness, and wear resistance. Tooling applications include drills taps, end mills, reamers, lathe and planer tools, broaches and boring tools, and more.
O1 is a general-purpose oil-hardened steel that offers good abrasion resistance and abundant toughness for a wide variety of tool and dies applications.
S7 is an oil or air-hardened, shock-resistant steel that offers very high impact toughness and high strength, along with medium wear resistance. Its applications include various dies, chisels, punches, rivet sets, and shear blades.
W1 is a water-hardened tool steel with a high carbon content that allows for a keen cutting edge. It offers moderate wear resistance. It is often used in various dies, drills, punches, taps, reamers, wood knives, embossing taps, and more.
Powder metals (PM) or PM high-speed steels are alternatives to conventional steels. Metal powders are the base materials for these steels. Through powered metallurgy, the powders are pressed into the desired shape and sintered (heated) to bond the material to produce the desired qualities, such as high-temperature strength, high-wear resistance, and toughness. Crucible particle metallurgy (CPM) is a powdered metallurgy process developed by Crucible Industries. Common PM steels used in tooling include:
CPM 1V tool steel is a high alloy, medium-carbon tool steel that exhibits high impact toughness, extreme heat resistance, and moderate wear resistance. It should be considered for blanking dies, cold and hot forging punches, gear rolling dies, shear blades, and sizing dies.
CPM 3V is an air-hardened tool steel that exhibits high impact strength and good wear resistance, providing maximum resistance to breakage and chipping. Blanking and sizing dies, shear blades, cold and hot forging punches, powder compaction tooling, and other tooling are made from it.
CPM 9V is an air-hardened tool steel that exhibits very high wear resistance, impact toughness, and heat resistance. Its durability is lower than other hot work tool steels. It is used in applications where resistance to thermal fatigue cracking is important, such as plastic injection feeder screws, non-return valves, shear blades, and forging dies. It has improved toughness compared to 10V.
CPM 10V is an air-hardened tool steel that exhibits high wear resistance and high impact toughness. Offer better wear resistance than high-carbon, high-chromium die steels.
CPM 15V is a cold work tool steel that provides unmatched wear resistance and provides longer tool life than 10V. It is also an alternative to sintered carbide in applications where solid carbide fractures or for intricate tool designs that are not possible with carbide.
CPM Rec M4, or PM M4, is a high-speed tool steel that provides a combination of high wear resistance with high impact toughness and bend strength. It is commonly used in form tooling, punches, broach inserts, taps, and header tooling.
Vanadis 4 Extra is a versatile tool steel manufactured by Uddeholm that offers a combination of ductility, wear resistance, and toughness. It is especially suitable for applications where adhesive wear and chipping are the primary failure mechanisms.
At Pivot, we work with a variety of steel and other materials to deliver tooling you can count on. With shorter lead times and competitive pricing, we can provide the high-quality, high-precision tooling you need to get the job done. Contact us to discuss your tooling requirements.
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