What is the difference between tool steel and HSS?

Tool steel is a kind of carbon alloy which is perfectly suited for manufacturing several types of tool. Machine dies and hand tools are two of its top application areas. Robustness, hardness, resistance against wears and abrasions, characteristic of retaining shape even at excessively high temperatures are few of its properties. Tool steel can be further categorized into water hardening, air hardening, oil hardening, D type, hot working, high speed steel, shock resistant type. High speed steel is a subcategory of tool steel. It is alloy steel containing tungsten, molybdenum, vanadium, chromium and in rare cases, cobalt. Each of these metals render certain properties to the otherwise standard tool steel. For instance, vanadium is used for extreme strength while cobalt helps in increasing hot hardness and gives outstanding wear resistance. High speed steel is commonly used for cutting tools.

1.      Composition of HSS and tool steel – High speed steel suppliers define it as superior to the old high carbon steels which was widely in use during 1940s which provided standard resistance against high temperatures without losing its hardness. Tungsten in HSS helps in resistance against wearing and increases tempering. Vanadium gives wear resistance in finishing tools. Molybdenum is primarily used for increasing toughness. Cobalt is helpful for increasing hardening temperatures and improves resistance against wears. Tool steel is the parent of HSS in this regard. Besides all the characteristics of HSS, several other types of tool steel as mentioned earlier has distinct properties. The application of the grades differ depending on the purpose of business.

2.      Subcategories of HSS and tool steel – Tool steel can be broadly classified into three types – cold working steel, hot working steel and high speed steel. Cold working steel can be further categorized into four types – oil hardening, air hardening, medium alloy cold work steel and high carbon high chromium cold working steel. Hot working steel is primarily of three different types – molybdenum , tungsten and intermediate HSS. Other types of tool steel are – water hardening, shock resistant, low alloy special category and low carbon. High speed steel on the other hand can be subdivided into four main categories – tungsten, molybdenum, molybdenum and cobalt, molybdenum and vanadium. Commonly used molybdenum high speed steel are – M1, M2, M7, M50 and T1. Cobalt high speed steel are M35 and M42. For M type HSS, the Rockwell C hardness measures between 63 and 65. For cobalt HSS, it can reach up to 70. There are a total of 7 T-types and 17 M-types HSS.

3.      Application – The prime use of high speed steel, as mentioned by high speed steel suppliers is in production of many types of cutting tools. Taps, drills, tool bits, milling cutters, saw blades, planers, jointer blades, router bits etc. Use of HSS in punches and dies has increased over the due course of time. The excellent property of retaining it’s shape and resistance against wears even after being in close and frequent contact with other materials and steel has given high speed steel it’s superior position in the market. Tool steel is heavily used in multiple industries. Reamers, saw blades, cutters etc that are used for machining wood, metals and plastic are few of the most commonly used areas of tool steel.

Other grades of tool steel have various other functions in many industries. High speed steel suppliers noted that this particular tool steel is praised for cutting tools without any hassle and with a certain level of smoothness.