Also known as HSS, high speed steel is one of the most outstanding steel products available. Why is this so? In this article, we will be defining what HSS is, its common grades and properties. Essentially, HSS refers to the steel alloy that is named after its high capacity to handle other materials much faster than other high-carbon steels. This is due to the outstanding hardness, great abrasion resistance and resistance over softening at high temperatures. All thanks to how it is processed and heat treated to achieve its amazing properties.
The heat treatment applied is a vital part of what makes high speed steel very capable. It contributes to its great martensitic structure which further led to its high hardness. This is done through the austenization process used to bring the steel to its melting temperature and quench it in a salt bath or by air cooling it. Then several tempering cycles are performed to convert the remaining austenite to martensite. The most distinguishing elements of HSS are the following:
High alloy content, which is chiefly made of tungsten or molybdenum, with some traces of cobalt, chromium, and vanadium
High carbon content, containing around 1.5% of carbon at the maximum while 0.65% at the minimum level
With at least 64 rockwell hardness at room temperature
Involvement of heat treatment process that generates very high quantity of complex metallic carbides that are suspended in steel substrate, resulting in great wear resistance and hardness
When it comes to grades, HSS has more than 40 classifications categorized by the American Iron and Steel Institute (AISI). Each grade of high speed steel is designated with its unique number to distinguish it from other grades. While they are composed of different content of tungsten, molybdenum, and carbide, they all contain some amounts of these elements to achieve certain properties. Ultimately, what makes HSS grade to have strong influence on its properties and various grades is the chief alloying elements that make it up. The specific content is designed according to desired properties.
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