Language
Country/Area
No result found
Why can high-speed steel withstand high temperatures? Explore the secret of steel hardness!
High speed steel (HSS) is widely used in cutting tool materials and is favored for its excellent high temperature resistance. This steel is unique in that it can withstand higher temperatures than high carbon steel without losing its hardness. This allows high-speed steel to cut faster than high-carbon steel, hence the name "high-speed steel."
High-speed steel exhibits high hardness exceeding 60 Rockwell C and high wear resistance under conventional heat treatment. Compared with common carbon steel and tool steel, its performance is even better.
The history of high-speed steel can be traced back to 1868. The "Mushet steel" developed by the British metallurgist Robert Forester Mushet can be regarded as the precursor of modern high-speed steel . This steel contains 2% carbon, 2.5% manganese and 7% tungsten. Its main advantage is its ability to harden when air cooled, which is done at temperatures where most steels require quenching to harden.
Over the next few decades, the manganese in Muhit steel was replaced by chromium, an important step in the development of high-speed steels. Between 1899 and 1900, Frederick Winslow Taylor and his team conducted a series of experiments at the Bethlehem Steel Company in Pennsylvania, USA, heating existing high-quality tool steel to At temperatures well above industry practice, the process is known as the Taylor-White process.
This process revolutionized the machining industry, allowing tool steel to maintain its hardness at high temperatures and increasing cutting speeds from 30 to 90 feet per minute, causing a sensation at the 1900 Paris Exposition.
There are many types of high-speed steel, mainly obtained by adding various alloy metals to carbon steel to obtain the desired properties, usually containing tungsten and molybdenum, or a combination of both, and often adding other alloys. High-speed steel belongs to the Fe–C–X multi-component alloy system, where X represents elements such as chromium, tungsten, molybdenum, vanadium or cobalt. Generally speaking, the content of X component is more than 7%, and the content of carbon is more than 0.60%. According to the Unified Numbering System (UNS), tungsten types (such as T1, T15) are assigned to the T120xx series, while molybdenum types (such as M2, M48) and intermediate types are classified as T113xx.
The addition of about 10% tungsten and molybdenum can fully increase the hardness and toughness of high-speed steel and maintain these properties at the high temperatures generated by cutting metals.
Among them, molybdenum-based high-speed steel (HSS) combines molybdenum, tungsten and chromium to form several alloys, often referred to as "HSS". For example, M1 lacks some of the red-hot hardness properties of M2, but is more impact-resistant and has better flexibility. M2 is the most widely used industrial high-speed steel, with small and evenly distributed carbides, providing high wear resistance.
M35 is an alloy that adds 5% cobalt to M2 to improve heat resistance and has a hardness of up to 70 Rockwell C, while M42 is a molybdenum series high-speed steel with 8% cobalt and its red hot hardness Superior to other conventional high-speed steels, it is widely used in the metal manufacturing industry.
The application of high-speed steel is still mainly concentrated in the manufacture of various cutting tools, including drill bits, dental cutters, milling cutters, etc. As demand changes, the use of molds and punches has gradually increased. High-speed steel tools are particularly popular in wood turning because the workpiece moves at relatively high speeds in hand tool operations, and HSS is able to keep its cutting edges sharp for long periods of time.
However, despite the superior performance of high-speed steel, how to choose the appropriate type of steel for different applications is still a topic worth exploring?
