Selection of High-Speed Tool Steels

High-speed tool steels are designed primarily for cutting tool applications. The term “high-speed” was used when these steels were first invented. The term refers to the fact that the steels could be used as cutting tools at high turning speeds on a lathe. In some cases, the turning speeds were so fast that the tools would heat to dull red color, which is about °F (593°C). The ability to maintain the hardness required for cutting while at this temperature is a property known as red hardness or hot hardness, and it is the primary defining characteristic of high-speed steels.

Youngson supply professional and honest service.

High-speed steels exhibit high strength and hardness, but typically exhibit lower toughness than the cold work tool steels. Some, most notably M2 and powder metal M4, are used in cold work applications because of the strength and wear resistance which can be achieved.

To qualify as a high-speed steel, the chemical composition must meet certain minimum requirements, which are defined in the ASTM A600 Specification for High-Speed Tool Steels. The lowest alloy grades, M50 and M52 high-speed steels, are properly known as intermediate high-speed steels because of their lower alloy contents. The cobalt-bearing grades, such as M35 and M42, are known as super high-speed steels because they exhibit enhanced hot hardness.

The nominal chemical compositions of the common high-speed and intermediate high-speed tool steels are presented in weight percent below. Relative comparisons of the properties of the steels are presented in the chart on the reverse side. More specific information about the steels may be obtained from the individual data sheets. Grades with the DuraTech™ prefix are manufactured by powder metallurgy and provide very unique combinations of strength, toughness, and wear resistance. Several of the grades are also available in a resulfurized version. The sulfur addition improves the machinability of the steel in the annealed condition and the grindability in the hardened condition.

A lot goes into the planning and prototyping process when developing a new application for a specific end use. In this alloy selection guide, our goal is to help you find the right balance across all the common factors and land on the alloy that fits your manufacturing process, application needs, and buying requirements. Once you know your goal, you must determine what alloy is going to be the best for YOUR product and be able to justify it. Many aspects need to be considered in alloy selection and they are not always weighted evenly. Purchasing usually has certain things to consider, while Engineering may be evaluating things differently, and the same goes for Production. Departmental, or the interests and requirements of different disciplines within your organization may have their own factors to consider that may not always line up but is important to consider all main factors of alloy selection when choosing the metal for your product.

Manufacturers understand that every metal alloy has unique properties to weigh against each other when deciding on an alloy for your product. The main factors that are often considered are:

1. Physical Properties
2. Mechanical Properties
3. Cost
4. Service
5. Fabrication
6. Surface Properties

How each of these ranks will, of course, vary from project to project and application to application. The point is though, that all of these should be factored into your selection and if you are not sure how to go about ranking them, we should dive a little deeper into the ins and outs of each. Ulbrich's Metallurgy department can always help with this too.

Want more information on High-Performance Alloy Tool Steel? Feel free to contact us.

Physical Properties

This is a crucial factor in determining the appropriate alloy for your application because there are so many different things to look at. If you are looking for something that may be exposed to water, we would want to consider an alloy with excellent corrosion resistance. Other applications may bring things like thermal, electrical and magnetic properties into play. If the end use of a product is within the aerospace field, it may be worth looking at how the alloy operates under high and low temperatures, so a Nickel alloy may be the best option. If it is a consumer product, aesthetic appeal could be more important, so it will be worth looking at the different finish options.

Mechanical Properties

Another factor that always needs to be looked at, mechanical properties of an alloy can vary greatly depending on both its content and how it was processed. Strength (tensile and yield), ductility, hardness and toughness are all often looked at within the umbrella of mechanical properties. Some applications are better off with harder material while some, maybe they require a lot of forming, need softer material. This can all be controlled during the rolling and annealing processes. Working closely with a stainless steel and special metals precision reroller with engineering and metallurgy teams on staff are a helpful resource for getting your desired alloy's mechanical properties right for your needs.

Cost

This can often be a key prohibitive factor in the alloy selection process. It is important however, within cost, to explain why things are priced the way they are. Different alloys have different elemental content, are processed in various ways and must be processed differently. By this I mean, a certain alloy might be cheaper as a raw material, but if its’ lifespan is 1/3 the lifespan of an alternative option, is it really worth it? Will money or time be saved in the long run by going with more expensive but also more suitable/qualified option. These are a few questions to consider when weighing cost as a long-term factor.

Service

This factor in alloy selection plays into some of what was mentioned in the Cost Section. Meaning, what will the maintenance be like on your application because of the alloy you selected? In most scenarios there are some type of outside factors such as temperature or other environmental concerns that may affect how long a product will last before it must be serviced. Choosing the best possible alloy for your product should extend the time between servicing or just extend the lifespan. We can look in depth at this and determine if it makes more sense to select an alloy that will be serviced a lot and is easier to process up front or a specialty metal that will need little to no service.

Fabrication

Manufacturing and producing this part is where we need to look at the appropriate fabrication selection. Maybe your part needs to be deep drawn and we should take a look at an alloy with higher Nickel content, such as 305 Stainless Steel. In other scenarios a part may need to be stretch formed or welded and we could recommend an appropriate alloy for that, such as 316L stainless steel in strip or wire. 316L has resistance to intergranular corrosion following the welding process. Ulbrich is happy to review any considerations such as these.

Surface Finish & Surface Properties

A lot of different characteristics can fall under this category and all are important to making alloy selection that makes sense for your process and part. Different end uses for a part will make a manufacturer value different types of surface properties such as the appearance, abrasion, and a coating or the finish. Ulbrich offers many different finish capabilities and will work with you to reach appropriate surface roughness and appearance for your application.

Are you interested in learning more about Hiperco 50A alloy supplier? Contact us today to secure an expert consultation!