Tool steel
Encyclopedia
Tool steel refers to a variety of carbon and alloy steels that are particularly well-suited to be made into tool
s. 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 (red-hardness). Tool steel is generally used in a heat-treated state.
With a carbon content between 0.7% and 1.5%, tool steels are manufactured under carefully controlled conditions to produce the required quality. The manganese
content is often kept low to minimize the possibility of cracking during water quenching. However, proper heat treating
of these steels is important for adequate performance, and there are many suppliers who provide tooling blanks intended for oil quenching.
Tool steels are made to a number of grades for different applications. Choice of grade depends on, among other things, whether a keen cutting edge is necessary, as in stamping dies
, or whether the tool has to withstand impact loading
and service conditions encountered with such hand tools as axe
s, pickaxe
s, and quarry
ing implements. In general, the edge temperature under expected use is an important determinant of both composition and required heat treatment. The higher carbon grades are typically used for such applications as stamping dies, metal cutting tools, etc.
Tool steels are also used for special applications like injection molding
because the resistance to abrasion is an important criterion for a mold that will be used to produce hundreds of thousands of parts.
The AISI
-SAE grades of tool steel is the most common scale used to identify various grades of tool steel. Individual alloys within a grade are given a number; for example: A2, O1, etc.
. This type of tool steel is the most commonly used tool steel because of its low cost compared to other tool steels. They work well for small parts and applications where high temperatures are not encountered; above 150 °C (302 °F) it begins to soften to a noticeable degree. Hardenability
is low so W-grade tool steels must be quenched in water. These steels can attain high hardness (above HRC 60) and are rather brittle compared to other tool steels.
The toughness of W-grade tool steels are increased by alloying with manganese, silicon and molybdenum. Up to 0.20% of vanadium is used to retain fine grain sizes during heat treating.
Typical applications for various carbon compositions are:
1.0–1.4% manganese, 0.50% chromium
, 0.50% nickel
, and 0.50% tungsten
. It is a very good cold work steel and also makes very good knives. It can be hardened to about 57-61 HRC.
, which was known as air-hardening steel at the time.
Modern air-hardening steels are characterized by low distortion during heat treatment because of their high-chromium content. They also harden in air because they have less alloyants than oil-hardening grades. Their machinability is good for tool steels and they have a balance of wear resistance and toughness (i.e. between the D- and shock-resistant grades).
or semi-stainless tool steels. However their corrosion resistance was very limited due to the precipitation of major amount of chromium and carbon as carbides.
contains 1.5% carbon and 11.0–13.0% chromium; additionally it is composed of 0.45% manganese, 0.030% max phosphorus
, 0.030% max sulfur
, 1.0% vanadium
, 0.7% molybdenum, and 0.30% silicon. D2 is very wear resistant but not as tough as lower alloyed steels. Mechanical properties of D-2 is very sensitive to heat treatment. It is widely used for shear blades, planer blades and industrial cutting tools, sometimes used for knives.
EN 20 B, is an air hardening tool steel with a primary alloying element of nickel. It possesses good toughness, stable grains, and is highly polishable. It is primarily used for dies in plastic injection molding application that involve high stresses. Other applications include blanking
dies, forging
dies, and industrial blades.
58/60). This type of steel is used in applications such as jackhammer
bits.
T1 (also known as 18-4-1) is a common T-grade alloy. Its composition is 0.7% carbon, 18% tungsten, 4% chromium, and 1% vanadium. M2 is a common M-grade alloy.
and plastic injection molding dies.
Tool
A tool is a device that can be used to produce an item or achieve a task, but that is not consumed in the process. Informally the word is also used to describe a procedure or process with a specific purpose. Tools that are used in particular fields or activities may have different designations such...
s. 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 (red-hardness). Tool steel is generally used in a heat-treated state.
With a carbon content between 0.7% and 1.5%, tool steels are manufactured under carefully controlled conditions to produce the required quality. The 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...
content is often kept low to minimize the possibility of cracking during water quenching. However, proper heat treating
Heat treatment
Heat treating is a group of industrial and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass...
of these steels is important for adequate performance, and there are many suppliers who provide tooling blanks intended for oil quenching.
Tool steels are made to a number of grades for different applications. Choice of grade depends on, among other things, whether a keen cutting edge is necessary, as in stamping dies
Die (manufacturing)
A die is a specialized tool used in manufacturing industries to cut or shape material using a press. Like molds, dies are generally customized to the item they are used to create...
, or whether the tool has to withstand impact loading
Structural load
Structural loads or actions are forces, deformations or accelerations applied to a structure or its components.Loads cause stresses, deformations and displacements in structures. Assessment of their effects is carried out by the methods of structural analysis...
and service conditions encountered with such hand tools as axe
Axe
The axe, or ax, is an implement that has been used for millennia to shape, split and cut wood; to harvest timber; as a weapon; and as a ceremonial or heraldic symbol...
s, pickaxe
Pickaxe
A pickaxe or pick is a hand tool with a hard head attached perpendicular to the handle.Some people make the distinction that a pickaxe has a head with a pointed end and a flat end, and a pick has both ends pointed, or only one end; but most people use the words to mean the same thing.The head is...
s, and quarry
Quarry
A quarry is a type of open-pit mine from which rock or minerals are extracted. Quarries are generally used for extracting building materials, such as dimension stone, construction aggregate, riprap, sand, and gravel. They are often collocated with concrete and asphalt plants due to the requirement...
ing implements. In general, the edge temperature under expected use is an important determinant of both composition and required heat treatment. The higher carbon grades are typically used for such applications as stamping dies, metal cutting tools, etc.
Tool steels are also used for special applications like injection molding
Injection molding
Injection molding is a manufacturing process for producing parts from both thermoplastic and thermosetting plastic materials. Material is fed into a heated barrel, mixed, and forced into a mold cavity where it cools and hardens to the configuration of the cavity...
because the resistance to abrasion is an important criterion for a mold that will be used to produce hundreds of thousands of parts.
The AISI
American Iron and Steel Institute
The American Iron and Steel Institute is an association of North American steel producers. Its predecessor organizations date back to 1855 making it one of the oldest trade associations in the United States. AISI assumed its present form in 1908, with Elbert H...
-SAE grades of tool steel is the most common scale used to identify various grades of tool steel. Individual alloys within a grade are given a number; for example: A2, O1, etc.
Water-hardening grades
W-grade tool steel gets its name from its defining property of having to be water quenched. W-grade steel is essentially high carbon plain-carbon steelPlain-carbon steel
Carbon steel, also called plain-carbon steel, is steel where the main interstitial alloying constituent is carbon. The American Iron and Steel Institute defines carbon steel as: "Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt,...
. This type of tool steel is the most commonly used tool steel because of its low cost compared to other tool steels. They work well for small parts and applications where high temperatures are not encountered; above 150 °C (302 °F) it begins to soften to a noticeable degree. Hardenability
Hardenability
The hardenability of a metal alloy is its capability to be hardened by heat treatment. It should not be confused with hardness, which is a measure of a sample's resistance to indentation or scratching. It is an important property for welding, since it is inversely proportional to weldability,...
is low so W-grade tool steels must be quenched in water. These steels can attain high hardness (above HRC 60) and are rather brittle compared to other tool steels.
The toughness of W-grade tool steels are increased by alloying with manganese, silicon and molybdenum. Up to 0.20% of vanadium is used to retain fine grain sizes during heat treating.
Typical applications for various carbon compositions are:
- 0.60–0.75% carbon: machine parts, chisels, setscrews; properties include medium hardness with good toughness and shock resistance.
- 0.76–0.90% carbon: forging dies, hammers, and sledges.
- 0.91–1.10% carbon: general purpose tooling applications that require a good balance of wear resistance and toughness, such as drills, cutters, and shear blades.
- 1.11–1.30% carbon: small drills, lathe tools, razor blades, and other light-duty applications where extreme hardness is required without great toughness.
Cold-working grades
These tool steels are used on larger parts or parts that require minimal distortion during hardening. The use of oil quenching and air hardening helps reducing distortion as opposed to higher stress caused by quicker water quenching. More alloying elements are used in these steels, as compared to water-hardening grades. These alloys increase the steels' hardenability, and thus require a less severe quenching process. These steels are also less likely to crack and are often used to make knife blades.Oil-hardening grades
contains 0.90% carbonCarbon
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...
1.0–1.4% manganese, 0.50% chromium
Chromium
Chromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
, 0.50% nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
, and 0.50% tungsten
Tungsten
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...
. It is a very good cold work steel and also makes very good knives. It can be hardened to about 57-61 HRC.
Air-hardening grades
The first air hardening grade tool steel was mushet steelMushet steel
Mushet steel, also known as Robert Mushet's Special Steel , 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...
, which was known as air-hardening steel at the time.
Modern air-hardening steels are characterized by low distortion during heat treatment because of their high-chromium content. They also harden in air because they have less alloyants than oil-hardening grades. Their machinability is good for tool steels and they have a balance of wear resistance and toughness (i.e. between the D- and shock-resistant grades).
| Grade | Composition | Notes |
|---|---|---|
| 1.0% C 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... , 1.0% Mn 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... , 5.0% Cr Chromium Chromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable... , 0.3% Ni Nickel Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile... , 1.0% Mo Molybdenum Molybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores... , 0.15–0.50% V Vanadium Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature... |
A common general purpose tool steel; it is the most commonly used variety of air-hardening steel. It is commonly used for blanking and forming punches, trimming dies, thread rolling dies, and injection molding dies. | |
| 1.25% C, 0.5% Mn, 5.0% Cr, 0.3% Ni, 0.9–1.4% Mo, 0.8–1.4% V | ||
| 1.0% C, 2.0% Mn, 1.0% Cr, 0.3% Ni, 0.9–1.4% Mo | ||
| 0.7% C, 1.8–2.5% Mn, 0.9–1.2% Cr, 0.3% Ni, 0.9–1.4% Mo | This grade of tool steel air-hardens at a relatively low temperature (approximately the same temperature as oil-hardening grades) and is dimensionally stable. Therefore it is commonly used for dies, forming tools, and gauges that do not require extreme wear resistance but do need high stability. | |
| 2.00–2.85% C, 0.8% Mn, 5.00–5.75% Cr, 0.3% Ni, 0.9–1.4% Mo, 3.9–5.15% V, 0.5–1.5 W Tungsten 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... |
||
| 0.5–0.6% C, 0.5% Mn, 4.75–5.50% Cr, 0.3% Ni, 1.15–1.65% Mo, 1.0–1.5 W | ||
| 0.5% C, 0.5% Mn, 0.95–1.15% Si Silicon Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table... , 4.75–5.00% Cr, 1.25–1.75% Ni, 1.3–1.8% Mo, 0.8–1.4% V |
||
| 1.25–1.50% C, 1.6–2.1% Mn, 1.0–1.5% Si, 1.55–2.05% Ni, 1.25–1.75% Mo | This grade contains a uniform distribution of graphite Graphite The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal... particles to increase machinability and provide self-lubricating properties. It is commonly used for gauges, arbors, shears, and punches. |
D-grades
D-grade tool steels contain between 10% and 18% chromium. These steels retain their hardness up to a temperature of 425 °C (797 °F). Common applications for these grade of tool steel is forging dies, die-casting die blocks, and drawing dies. Due to high chromium content, certain D-grade tool steel grades are often considered stainlessStainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....
or semi-stainless tool steels. However their corrosion resistance was very limited due to the precipitation of major amount of chromium and carbon as carbides.
contains 1.5% carbon and 11.0–13.0% chromium; additionally it is composed of 0.45% manganese, 0.030% max phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
, 0.030% max sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
, 1.0% vanadium
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...
, 0.7% molybdenum, and 0.30% silicon. D2 is very wear resistant but not as tough as lower alloyed steels. Mechanical properties of D-2 is very sensitive to heat treatment. It is widely used for shear blades, planer blades and industrial cutting tools, sometimes used for knives.
1.2767
ISO 1.2767, also known as DIN X 45 NiCrMo 4, AISI 6F7, and BSBS
BS, B.S., Bs or bs may refer to:-Academics:*Bachelor of Science degree, also abbreviated BSc*Bachelor of Surgery*Behavioural sciences-Standards:*Venezuelan bolívar's currency sign*Bolivian boliviano's currency sign...
EN 20 B, is an air hardening tool steel with a primary alloying element of nickel. It possesses good toughness, stable grains, and is highly polishable. It is primarily used for dies in plastic injection molding application that involve high stresses. Other applications include blanking
Blanking (metalworking)
Blanking and piercing are shearing processes in which a punch and die are used to modify webs. The tooling and processes are the same between the two, only the terminology is different: in blanking the punched out piece is used and called a blank; in piercing the punched out piece is...
dies, 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...
dies, and industrial blades.
Shock resisting grades
S-grade tool steel are designed to resist shock at both low and high temperatures. A low carbon content is required for the necessary toughness (approximately 0.5% carbon). Carbide-forming alloys provide the necessary abrasion resistance, hardenability, and hot-working characteristics. This family of steels displays very high impact toughness and relatively low abrasion resistance, it can attain relatively high hardness (HRCRockwell scale
The Rockwell scale is a hardness scale based on the indentation hardness of a material. The Rockwell test determines the hardness by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload. There are different scales, denoted by a single...
58/60). This type of steel is used in applications such as jackhammer
Jackhammer
A jackhammer is a pneumatic tool that combines a hammer directly with a chisel that was invented by Charles Brady King. Hand-held jackhammers are typically powered by compressed air, but some use electric motors. Larger jackhammers, such as rig mounted hammers used on construction machinery, are...
bits.
High speed grades
T-grade and M-grade tool steels are used for cutting tools where strength and hardness must be retained at temperatures up to or exceeding 760 °C (1,400 °F). M-grade tool steels were developed to reduce the amount of tungsten and chromium required.T1 (also known as 18-4-1) is a common T-grade alloy. Its composition is 0.7% carbon, 18% tungsten, 4% chromium, and 1% vanadium. M2 is a common M-grade alloy.
Hot-working grades
H-grade tool steels were developed for strength and hardness during prolonged exposure to elevated temperatures. All of these tool steels use a substantial amount of carbide forming alloys. H1 to H19 are based on a chromium content of 5%; H20 to H39 are based on a tungsten content of 9-18% and a chromium content of 3–4%; H40 to H59 are molybdenum based.Special purpose grades
is short for plastic mold steels. They are designed to meet the requirements of zinc die castingDie casting
Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process...
and plastic injection molding dies.
- L-grade tool steel is short for low alloy special purpose tool steel. L6 is extremely tough.
- F-grade tool steel is water hardened and substantially more wear resistant than W-grade tool steel.
Comparison
| Defining property | AISI-SAE grade | Significant characteristics |
|---|---|---|
| Water-hardening | W | |
| Cold-working | O | Oil-hardening |
| A | Air-hardening; medium alloy | |
| D | High carbon; high chromium | |
| Shock resisting | S | |
| High speed | T | Tungsten base |
| M | Molybdenum base | |
| Hot-working | H | H1–H19: chromium base H20–H39: tungsten base H40–H59: molybdenum base |
| Plastic mold | P | |
| Special purpose | L | Low alloy |
| F | Carbon tungsten |
See also
- Silver steelSilver steelSilver steel is common tool steel that is supplied as a centerless ground round bar .Amongst other applications, it has been widely used to make such things as punches, engravers, screwdrivers. Sheffield silver steel is used in France as a blade steel for straight razors...
is a common tool steel in the UK that is roughly equivalent to drill rod in the U.S.