High-speed steel ( HSS or HS ) is part of a steel tool, usually used as a cutting tool.
It is often used in saw blades and electric drill. This is superior to older high carbon steel tools that were used extensively through the 1940s because they can withstand higher temperatures without losing their (violent) nature. This property allows HSS to cut faster than high carbon steel, hence the name high-speed steel . At room temperature, in generally recommended heat treatments, HSS values ​​generally exhibit high hardness (above Rockwell 60 hardness) and abrasion resistance (generally associated with tungsten and vanadium content often used in HSS) compared to common carbon and sculpture steels.
Video High-speed steel
History
Although the development of modern high-speed steel began in the second half of the 19th century, there is documented evidence of previously produced steel with similar content. These include hardened steel in China in the 13th century BC, wootz steel produced in India around 350 BC and the production of Damascus and Japanese plated steel blades in 540 AD and 900 AD. The high-speed properties of the steels are mostly accidental (since no machining technology involves quantification of speed and feed at the time) and will be the result of local iron ore containing traces of natural tungsten or other advantageous alloying components.
In 1868, the British metallurgist Robert Forester Mushet developed Mushet's steel, which is considered a forerunner of modern high-speed steel. It consists of 2% carbon (C), 2.5% manganese (Mn), and 7% tungsten (W). The main advantage of this steel is that it hardens when air is cooled from the temperature at which most of the steel must be extinguished for hardening. Over the next 30 years, the most significant change is the replacement of manganese (Mn) with chromium (Cr).
In 1899 and 1900, Frederick Winslow Taylor and Maunsel White, working with a team of assistants at Bethlehem Steel Company in Bethlehem, Pennsylvania, conducted a series of experiments with heat treatment against existing high-quality steel tools, such as the steel Mushet, heating it to a temperature much higher than is usually considered desirable in the industry. Their experiments are characterized by scientific empiricism in many different combinations that are created and tested, regardless of conventional wisdom or alchemical prescriptions, and with detailed records stored from each batch. The end result is a heat treatment process that converts the existing alloy into a new type of steel that can retain its hardness at higher temperatures, allowing much higher speed and cutting rates when machining.
The Taylor-White process patented and created a revolution in the machinery industry. Heavier machine tools with higher stiffness are required to use new steel for full benefit, encouraging redesign and replacement of installed installations. The patent was contested and eventually canceled.
The first alloys that are formally classified as high-speed steels are known as AISI T1, which was introduced in 1910. Patented by Crucible Steel Co. at the beginning of the 20th century.
Although high-speed molybdenum-rich steel such as AISI M1 has been in use since the 1930s, the material shortages and high costs caused by World War II encouraged the development of cheaper alloys replacing molybdenum for tungsten. Advances in high-speed molybdenum-based steels during this period put them on par with and in certain cases better than tungsten-based high-speed steels. It starts with the use of M2 steel instead of steel T1.
Maps High-speed steel
Type
High-speed steels are alloys that derive their properties from tungsten or molybdenum, often with a combination of both. They include the Fe-C-X multi-component alloy system in which X represents chromium, tungsten, molybdenum, vanadium, or cobalt. Generally, X components present more than 7%, along with more than 0.60% carbon. Percentage of alloying elements is not alone provides the nature of hardness retaining; they also require the right high-temperature heat treatment to be the correct HSS; see History above.
In the integrated numbering system (UNS), tungsten type classes (eg T1, T15) are numbered in the T120xx series, while molybdenum (eg M2, M48) and intermediate type are T113xx. The ASTM standard recognizes 7 types of tungsten and 17 types of molybdenum.
The addition of approximately 10% of tungsten and molybdenum in total maximizes efficiently hardness and toughness of high speed steels and maintains these properties at high temperatures generated when cutting metal.
Tungsten Steels
- T1
- Original HSS, generally has been replaced by M2.
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Adding molybdenum, tungsten and chrome steel create several alloys commonly called "HSS", measuring 63-65 Rockwell hardness.
- M1
- M1 does not have some of the red hardness properties of M2, but is less susceptible to shock and will be more flexible.
- M2
- M2 is the most used "standard" and industrial HSS. It has small and even carbides that provide high wear resistance, although the decaying sensitivity is slightly high. After heat treatment, the hardness is equal to T1, but its bending strength can reach 4700 MPa, and its toughness and thermo-plasticity is higher than T1 by 50%. Usually used to produce various tools, such as drill bits, taps and reamers.
- M7
- M7 is used to make heavier construction exercises where flexibility and extend the life of the drill are just as important.
- M50
- M50 does not have any other grade red hardness of the HSS tungsten, but is excellent for exercises where damage is a problem as it stretches the drill. Generally preferred for hardware stores and contractor usage. It is also used in high temperature ball bearings.
The addition of cobalt increases heat resistance, and can provide Rockwell hardness of up to 67 Min..
- M35
- M35 is similar to M2, but with 5% cobalt added. M35 is also known as Cobalt Steel, HSSE or HSS-E. It will cut faster and last longer than M2.
- M42
- M42 is a molybdenum series high molecular steel alloy with an additional 8% or 10% cobalt. It is widely used in the metal manufacturing industry because of its superior red hardness compared to more conventional high-speed steels, allowing shorter cycle times in the production environment due to higher cutting speeds or from increased time between tool changes. M42 is also less prone to chipping when it is used for cut offs and costs less when compared to the same tools made of carbide. Tools made of high-speed cobalt-bearing steel can often be identified by HSS-Co.
Coating
High-speed steel life can be extended by coating the tools. One such coating is TiN (titanium nitride). Most coatings generally increase hardness and/or tool lubrication. Coatings allow the tip of the tool spear to pass through the material cleanly without having the bile material (rod) into it. This coating also helps lower the temperature associated with the cutting process and increase tool life.
Modify surfaces
Lasers and electron beams can be used as a strong source of heat on the surface for heat treatment, glazing, and composition modification. It is possible to achieve different liquid pool shapes and temperatures. The cooling rate ranges from 10 3 to 10 6 K s -1 . Profitably, there is little or no cracking or porosity formation.
While the possibility of heat treatment on the surface should be easily visible, other applications ask for clarification. At a cooling rate exceeding 10 6 K s -1 the eutectic microconstituents disappear and there is extreme separation of the substitution alloy element. It has the beneficial effect of a glass section without running that is associated with wear damage.
The alloy compositions of the part or tool may also be altered to form a high speed steel on the surface of a slim alloy or to form a coated alloy or enriched carbide on the surface of a high speed steel section. Some methods can be used such as foil, boronising pack, plasma spray powder, cored powder strip, inert gas blow feeder, etc. Although this method has been reported to be favorable and stable, it has not seen extensive commercial use.
Apps
The main use of high-speed steels is continuously made in the manufacture of various cutting tools: drills, taps, milling cutters, tool bits, cutters, saw saws, attack knives and connections, router bits, etc., although the use for blows and dies increases.
High-speed steels also find the market in good hand tools where their relatively good toughness at high hardness, coupled with high abrasion resistance, makes them suitable for low-speed applications that require sharp sharpness, such as files, chisels, plane knives, and damaskus kitchen knives and pocket knives.
High-speed steel tools are the most popular for use in woodturning, because the movement speed of the work passes through the edge is relatively high for handheld devices, and HSS holds the tip much longer than the high-carbon steel tools.
See also
- Container Industry
- List of steel producers
References
External links
Source of the article : Wikipedia
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