Mushet steel
Encyclopedia
Mushet steel, also known as Robert Mushet's Special Steel (RMS), self-hardening steel and air-hardening steel, is considered the first tool steel
and air-hardening steel. It was invented in 1868 by Robert Forester Mushet
. Prior to Mushet steel, steel had to be quenched to harden it. It later led to the discovery of high speed steel
.
was the main alloying constituent, which ranged between 4 and 12%, while manganese
(2–4%) and carbon
(1.5–2.5%) were the secondary alloying constituents. A typical sample contained 9% tungsten, 2.5% manganese, and 1.85% carbon.
Mushet steel was harder than standard water quenched steel. It was found that Mushet steel could be best hardened by submitting it to an air blast after forging
.
Mushet steel is non-magnetic.
due to its ability to retain its hardness at high temperatures. In 1894, Frederick Winslow Taylor
conducted machining comparison tests between Mushet steel and high carbon tool steel. He found that it could cut 41 to 47% faster on hard tire steel forgings and approximately 90% faster on mild steels. He also found that if a stream of water was used as a cutting fluid
the cutting speed
could be increased 30%. After Taylor's tests results were published Mushet and other self-hardening steels became popular in machine tools. Prior to Taylor's tests Mushet steel was often just used to increase the time between regrinds, take larger cuts, or machine harder materials.
In 1899 and 1900, Taylor and Maunsel White were experimenting with hardening processes for Mushet steel and other self-hardening steels. They discovered if the steel is heated to near its melting point it creates a more durable metal. The metal will retain its hardness up to a red heat
. This type of hardened self-hardening steel was the first high speed steel.
Tool steel
Tool steel refers to a variety of carbon and alloy steels that are particularly well-suited to be made into tools. Their suitability comes from their distinctive hardness, resistance to abrasion, their ability to hold a cutting edge, and/or their resistance to deformation at elevated temperatures...
and air-hardening steel. It was invented in 1868 by Robert Forester Mushet
Robert Forester Mushet
Robert Forester Mushet was a British metallurgist and businessman, born April 8, 1811, in Coleford, in the Forest of Dean, Gloucestershire, England. He was the youngest son of Scottish parents, Agnes Wilson and David Mushet; an ironmaster, formerly of the Clyde, Alfreton and Whitecliff...
. Prior to Mushet steel, steel had to be quenched to harden it. It later led to the discovery of high speed steel
High speed steel
High speed steelMost copyeditors today would tend to choose to style the unit adjective high-speed with a hyphen, rendering the full term as high-speed steel, and this styling is not uncommon . However, it is true that in the metalworking industries the styling high speed steel is long-established...
.
Properties
The chemical composition of Mushet steel varied; tungstenTungsten
Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...
was the main alloying constituent, which ranged between 4 and 12%, while manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
(2–4%) and carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
(1.5–2.5%) were the secondary alloying constituents. A typical sample contained 9% tungsten, 2.5% manganese, and 1.85% carbon.
Mushet steel was harder than standard water quenched steel. It was found that Mushet steel could be best hardened by submitting it to an air blast after forging
Forging
Forging is a manufacturing process involving the shaping of metal using localized compressive forces. Forging is often classified according to the temperature at which it is performed: '"cold," "warm," or "hot" forging. Forged parts can range in weight from less than a kilogram to 580 metric tons...
.
Mushet steel is non-magnetic.
Use
It was primarily used as a machine toolMachine tool
A machine tool is a machine, typically powered other than by human muscle , used to make manufactured parts in various ways that include cutting or certain other kinds of deformation...
due to its ability to retain its hardness at high temperatures. In 1894, Frederick Winslow Taylor
Frederick Winslow Taylor
Frederick Winslow Taylor was an American mechanical engineer who sought to improve industrial efficiency. He is regarded as the father of scientific management and was one of the first management consultants...
conducted machining comparison tests between Mushet steel and high carbon tool steel. He found that it could cut 41 to 47% faster on hard tire steel forgings and approximately 90% faster on mild steels. He also found that if a stream of water was used as a cutting fluid
Cutting fluid
Cutting fluid is a type of coolant and lubricant designed specifically for metalworking and machining processes. There are various kinds of cutting fluids, which include oils, oil-water emulsions, pastes, gels, aerosols , and air or other gases. They may be made from petroleum distillates, animal...
the cutting speed
Cutting speed
The phrase speeds and feeds refers to two separate velocities in machine tool practice, cutting speed and feed rate. They are often considered as a pair because of their combined effect on the cutting process...
could be increased 30%. After Taylor's tests results were published Mushet and other self-hardening steels became popular in machine tools. Prior to Taylor's tests Mushet steel was often just used to increase the time between regrinds, take larger cuts, or machine harder materials.
In 1899 and 1900, Taylor and Maunsel White were experimenting with hardening processes for Mushet steel and other self-hardening steels. They discovered if the steel is heated to near its melting point it creates a more durable metal. The metal will retain its hardness up to a red heat
Red heat
The practice of using colours to determine the temperature of a piece of ferrous metal comes from blacksmithing. Long before thermometers were widely available it was necessary to know what state the metal was in for heat treating it and the only way to do this was to heat it up to a colour which...
. This type of hardened self-hardening steel was the first high speed steel.