Lexicon
M
Martensite
Needle-shaped, very hard brittle substance, formed by a rapid cooling of austenite during quenching, so that carbon has no time to diffuse. When heated (tempered) at high temperatures (up to 720°C and for as long as 10 hours), martensite forms ferrite with spheroid cementite.
Martensitic steels
Because of its martensitic alloy content, this is hard steel formed already by air cooling, such as high speed steel, steels with 3-6% Mn and >=0.5% C, steels with 5-8% Ni and more than 5% C, and such with at least 5% Cr and more than 0.5% C. The martensitic Cr and high speed steels are easily hardened and used as tool steel.
Melting Loss
Carbon oxidisation is a characteristic dimension in steel refining. By blowing oxygen the smelting is decarbonised. The melting loss (in %) shows how much carbon was removed from the smelting. Reactor points for carbon melting loss are to be found directly under the oxygen stream, on the fire resistant lining of the converter, on the interface metal/CO-bubbles and in the metal-emulsion slag. Melting loss curves indicate the time needed for decarbonisation in every refining job.
Metal
Chemical elements which are distinguished by their strong reflective powers and are good heat and electricity conductors. Metals have a crystalline structure with a lattice of metallic attachments, have good durable properties and are readily pliable. They are distinguished according to density as heavy and light metals (bordering 4.5 g/cm³), chemically as precious and non precious metals. Similar properties are classified in the periodical table for the groups alkaline, earth alkaline and rare earth metals. Further distinctions are ferrous and non-ferrous metals.
Molybdenum
Chemical element: Mo, density 10.2 g/cm³ (heavy metal). White greyish metal used as an alloy in steel. It increases toughness and high temperature strength, hinders the brittleness of chrome and manganese heat treatable steel. Forming carbide it increases the corrosion resistance in low alloyed heat resistant steel. In high speed steel and higher alloyed steel Mo can be a replacement for tungsten to a certain extent. Mo has an edge layer carburisation effect in case-hardened steel. In austenite steel it increases the hot temperature strength and corrosive resistance.
MT
metrische Tonne
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