Lexicon

stainless steel from A to Z.

A


Alloy

Metallic material containing at least two elements. One of these elements must be a metal.

Alloying addition

Chemical element added to steel to influence its properties in a certain way. In the main: nitrogen, silicon, manganese, phosphorous, sulphur, chrome, nickel, molybdenum, copper, vanadium, tungsten, cobalt, lead, aluminium, titanium, tantalum, niobium, boron.

Austenite

Face centred cubic lattice (fcc) mixed crystal structure formed from deposits above the G-S-E line in an iron carbon diagram, also called Gamma mixed crystal compound (pearlite or martensite). Austenite is normally only resistant above 911°C; by adding alloy additives (Ni, Mn) and hyper quenching, Austenite also becomes resistant at room temperature. Austenite’s structure is non-magnetic, tough and has a strength attained through strain hardening (manganese steel, nickel steel, chrome-nickel steel). It is characterised by its high temperature strength and good anti-corrosive and anti-inflammatory properties.

B


Backwardation

In future contracts for storable goods, e.g. Nickel, the difference between the future price e.g. 3 months, and the cash price is usually positive. A constellation is however feasible where this difference can be negative, i.e. the cash price for the product, such as Nickel, is higher than the futures price. This can happen especially when it is advantageous to hold a certain product in stock. If for example there was a large sudden demand for a product, then the cost of storage and insurance would be outweighed by the value of this sought after product. This is a backwardation.

C


Call Option

A Call option signifies the right to buy an item or value (e.g. a stock) at a predetermined fixed price, “strike price”, either during its validity period (American option) or at maturity (European option); there is however no obligation to buy.

Carbide

Carbide is the reaction of carbon with a more electropositive element (anion with cation). In the structure of steel, a one such carbide is Fe3C, also know as Cementite. Together with Ferrite it forms the structure Pearlite. The resistance of steel in a nealed condition is determined by the ferrous carbide content, since carbide has a high toughness level. High-speed steel und hard metal alloys owe their cutting edge to carbides of hard materials tungsten, titanium, tantalum, niobium etc. Carbide is used in the wear protection of surfaces (e.g. tungsten carbide).

Carbon

Chemical element: C. Naturally found in different variations, crystalline in the form of diamonds, graphite or as amorphous carbon. In iron production it is used as a reducing and carburisation agent. In steel production carbon is the alloy which transforms iron into steel.

Charge

Another name for infeed when placing in a metallurgic container. Charge is the introduction of the material, charge time the period of treatment.

Chromium

Another name for infeed when placing in a metallurgic container. Charge is the introduction of the material, charge time the period of treatment.

Cobalt

Chemical element Co. density 8.9 g/cm³. A light grey ferro-magnetic slightly ductile metal with a good chemical stability. Co belongs to the Austenite family. With Cr or W it forms a wear and heat resistant hard alloy. Used as an alloy in extremely tough construction steel, high-speed steel, permanent magnetic materials and high temperature alloys. Co is also used as a bonding agent in sintered hard (metal) alloys.

Contango

Contango is the difference between the cash and the future price. It can be explained thus: if an object is bought today, yet ownership is deferred for 3 months, the capital is still committed. In addition to this the object may have to be stored, causing storage and insurance costs. The ensuing interest and costs are reflected in the contango. The contango is usually favourable, but under certain circumstances can become negative in which case it is called a backwardation.

Copper

Chemical element Cu, density 8.93 g/cm³ . Amongst all the technical non ferrous metals copper is the best electricity conductor, has a high corrosion resistance and is extremely flexible. It is used either in pure form or with a little alloy additive for parts which are heated (furnace nozzles, casting moulds, electrodes for resistors), in heat conducting apparatus (heating cooling elements), as a coating metal used in plating, as an alloy in bearings and hard soldering. Electric arc furnaces have electrodes of conductive copper. Cu is alloyed to steel in volumes of between 0.2 and 0.5%. It increases its tensile strength, yield point and hardness. Copper content of over 0.2%, in combination with phosphorous and other alloys, improves the weathering resistance. A precipitation hardening is possible with a copper content of 1.3%, since the solubility of copper in iron reduces with falling temperatures. A damaging brittleness is caused with upwards of around 0.5% copper in steel.

F


Ferrite

Metallographical description of the solid solution (iron-carbon diagram) where carbon is dissolved interstitial in its lattice. Its maximum carbon absorption is only 0.02%. Ferrite is only in low eutectoid steels, can be combined to form an alloy (alloyed steel) and has a high magnetic permeability up to 769°C. Pure ferrite materials possess less firmness, but high ductility. By forming alloys with Si or Cr it gains a special property (electrical sheets). Next to massive and grain boundary ferrite, with carbon contents of between 0.2 and 0.4% as a result of quick cooling from high temperatures, it can form square loop ferrite (Widmannstätten’scher Ferrite). This brittle structure appears mainly in cast materials and after welding.

Ferrite Steels

Steels which on solidification contain a ferrite structure which heat cannot change. This property depends upon ferrite formations. These steels are heat resistant, possess especially strong magnetic fields, do not allow quenching and tend to be coarse.

Ferro-Alloys

Intermediate products produced in coke furnaces, electric arc furnaces or low furnaces, used as additives in iron and steel productions, and contain one or more of the following alloy elements: more than 8% Si = Ferro silicon metal), more than 30% Mn (= Ferro manganese), more than 20 % Cr (= Ferro chrome), more than 40% W (=Ferro tungsten), more than a total of 10% of other alloys e.g. Cu, Al, Ti, V, Mo, Nb, F, are standardised according to European standards and DIN 17560-17599, SEW 1740.

H


Hard (metal) alloys

are composed mainly of (up to 95%) highly enamelled, very hard carbides, either of one carbide type or of a carbide of varying types (W, Ti, Ta, Nb). Furthermore chrome or boron carbide as well as compounds of hard materials with nitrogen may be present. The remainder is binder phase, Fe, Co or Ni. Co is the most used. Whereas carbide increases the abrasion resistance and cutting property, the binder phase creates a certain toughness and bending strength. These alloys are produced through pulverisation. Binding phase and hard materials are mixed to a powder. The powder is then pressed and sintered at temperatures higher than the melting point of the binding phase. The structure then has the appearance of rolled balls of carbide, with a binding phase filling.

Hedging

Hedging is to reduce the risk involved with interest rates and price fluctuations. Losses on the cash market should be compensated by profits on the futures market. A future contract is a binding agreement between two parties to buy or sell, and therefore receive or deliver a definite amount and a certain type of product at a fixed contract date at a fixed price A ‘long’ position obliges the buyer to pay the agreed price at maturity of the contract and to accept delivery. The corresponding ‘short’ position obliges the seller to delivery at maturity of the futures contract and to accept the agreed payment of the goods.

High Speed Steel

An alloyed high grade steel, part of the tool steel group, belonging to the steel group 32 (with Co) and 33 (without Co) (DIN EN 10 027-2). Characterised by the alloys Cr, W, Mo and V, and, if applicable, Co. High Speed Steel is extremely hard and tough, highly corrosion resistant and has a keen cutting ability, therefore suitable for tool making, also being able to adjust to temperature changes. The chemical property and heat control of this steel gives it its consistency and ability to take temperatures of 600°C. Because of their toughness, only carbides and oxide ceramics have better cutting abilities than high speed steel. They are used for metal cutting tools. DIN 17 350, EN 10020.

High temperature Steel

Is a austenite steel with very low C-content, at least 13% Cr, high Ni content easily more than 10% even up to 34%. These steels have good strength durability at temperatures between 550°C and 600°C, even under long-term mechanical stress. Two types of alloys >20% Chrome and >30% Nickel have this property even at temperatures of 900° to 1000°C. DIN 17459 pertains to circular tubes, DIN 17460 to sheets, coils, rods and forgings. Used mainly in building power stations where normal temperature steel (DIN 17175 and 17177) is not enough. Normal temperature and high temperature steel are standardised in DIN 17240 for screws and nuts.

I


Information sources / recommended reading:

Bundesverband Deutscher Stahlhandel e.V (Hrsg.)
Stahllexikon – Eine Materialkunde für den Stahlhandel, die Stahlproduktion und die Stahlverarbeitung
1996, 25. Auflage, Verlag Stahleisen GmbH, Düsseldorf

Rudolf Wolff & Co Ltd (Hrsg.)
Wolff’s Guide to the London Metal Exchange, 5th edition
1995, Metal Bulletin Books Ltd.

Verein Deutscher Eisenhüttenleute (Hrsg.)
Stahlfibel
1989, Verlag Stahleisen GmbH, Düsseldorf (Neuauflage in Vorbereitung)

Iron

Chemical element Fe, density 7.85 g/cm3 (heavy metal). As a metal, softer and more pliable than steel. It conducts electricity and heat better and is more corrosion resistant. Chemically pure Fe is only found naturally as meteor iron, otherwise only in connection with other elements, mainly as an oxide or carbonate. Technically pure Fe is only used for special tasks. According to European standards pig and cast iron are iron alloys with a C content of more than 2 %.

ISO

Short for the International Organisation for Standardisation, an institute which coordinates all standards. The aim of ISO is to promote standardisation worldwide, to aid the exchange of goods and services, and to develop the mutual cooperation of the various technical sectors. ISO works on ISO-Standards, which should not be modified in any way by its member states. In Germany these are called DIN ISO-Standards.

L


LME (London Metal Exchange)

The LME is one of the leading international future and option markets for raw materials. Contracts for the NE-Metals, copper, aluminium, lead, zinc, nickel, tin and most recently the precious metal silver are traded. The origins of the LME go back to 1571 and Queen Elizabeth I. Metal and raw material dealers used to meet on a regular basis. Finally in 1877 the London Metal Exchange Company was founded. For in-depth information a visit to the LME website (www.lme.co.uk) is recommended.

LME Membership

Over time a multilevel structure of membership has formed on the LME, accommodating the various needs of metal and financial traders.
Category 1 – Ring dealing members: the highest level, they may deal during the ring in the ring and also outside the ring 24 hours in the open marketplace. At the moment there are 15 companies in this category, most of which have strong ties to the raw material sector.
Category 2 – Associate Broker Clearing members: These have all the privileges of Ring Dealing members except they are not allowed to deal in the ring.
Category 3 – Associate Trade Clearing Members: These are not allowed to conclude contracts with customers, nor deal in the Ring, but they may clear their own exchange business.
Categories 4 – 7: these have no major influence on the trading activities of the LME.

LME Official Price

Based on the LME settlement price the various prices for the different future contracts. The standard contract with the highest market liquidity runs for 3 months. The longest contract is for 27 months. The official Future Price is based on the settlement price with the addition or subtraction of the Contango or Backwardation.

LME Settlement Price

The last price, not covered by a bid on the offer in the cash market (for immediate delivery), at the end of the second ring in the morning session, i.e. the price of the seller at the close. This price, which is officially announced on the LME floor is valid for 24 hours and is the accepted reference price for the prompt delivery of the metals.

LME trading day

The LME is a 24 hour market. Certain members (see LME membership) are authorized to complete contracts with customers day and night and are not restricted to floor trading. Floor trading begins at 11.40 and each metal is traded for five minutes. At 12.20, when all metals have been traded once, there is a 10 minute break, until 12.30 when all metals are traded once more for five minutes. This second phase is considered the more important since then the Settlement and the Official Prices are determined. After announcement of the Official Prices the kerb trading begins. During the kerb all eight contract metals are traded simultaneously. At 15.10 the afternoon session begins, identical to the morning session with the exception of the Official Prices.

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

N


Nickel

Chemical element Ni. Density 8.9% g/cm³ (heavy metal). Nickel belongs to the austenite family. Steel is made corrosion resistant by adding at least 8% nickel. Nickel improves the durability and coating and increases the toughness, especially at low temperatures. Nickel is close-grained, lowers the overheating sensitivity and increases the electrical resistance.

Nickel Future contract (LME)

Contract size: 6 mt, currency: US-dollar, minimum price change: 1 US-dollar per mt, delivery date for physical nickel: daily for the 3 month future contract, every Wednesday for the following 3 months and every third Wednesday for the next 15 months (totally 27 months). Quality: primary nickel with 99.8 % nickel content with a chemical analysis according to the ASTM Specifications. Form: cathodes, pellets or briquettes.

Nickel Options (LME)

On the underlying nickel future contacts, nickel options (calls/puts) have maturities of up to 27 months; declaration date (the last day on which the option can be exercised) is the first Wednesday of the month in which the option matures, delivery date is the third Wednesday in the month of maturity.

Nickel-base alloy

This is a collective name for alloys of Nickel and other metals, Cu, Cr, Fe, Mo, with a good heat and corrosion resistance. They are referred to by many trade names. W. Nr. 2.4360 is NiCu 30 Fe, an alloy with approx. two thirds nickel and one third copper. It is both extremely tough and corrosion resistant (sulphuric acid, hydrochloric acid, hydrofluoric acid, saline solutions) and is therefore used in pickling plants, chemical apparatus and sea water equipment. There are also cast iron alloys containing nickel of more than 50%, with about 20% Cr and a significant amount of Co with additives of Mo, Ti, Al and Fe. They are used for high technical and temperature demands. Sheets for various usage can be plated with a nickel-base alloy (explosive plated, roll plated). A range of nickel-base alloys can be found in the steel-iron list. Their product number begins with 2.

Non ferrous metals

This is the collective term for all metals except iron. They are distinguished according to density (above or below 4.5 g/cm³) as heavy or light metals, as low or high smelting, as precious and non-precious non-ferrous metals.

Non-alloyed stainless steel

This term has been newly defined with the introduction of DIN EN 10020. Previously it was used for all stainless steels where, apart from carbon, no other alloy was added. Now the term non-alloyed stainless is used for steels which have a higher purity than quality steels, especially with regard to non metallic inclusions. This steel is used mainly for quenching and tempering or surface hardening. There are many regulations in place to control harden-ability, firmness and toughness, so that the highest standards are maintained.

P


Phosphorous

Chemical element, P, density 1.8 g/cm³ (non metal). Embrittles steel material and is therefore combined with a limy slag when refining raw iron containing phosphorous. Machining steel contains a certain amount of P. In low alloyed steel P affects atmospheric corrosion. Phosphorous enhancement on grain boundaries is the reason for temper embrittlement. Phosphor alloyed high strength deep drawn steel is a modern lightweight solution in the car industry.

Put option

A put option is the right to sell a certain item or value (e.g. a stock) at a predetermined fixed price, “strike price”, during (American Option) or at the end of (European Option) the contract period.

R


Rust Free Stainless Steel

In 1958 the Informationsstelle Edelstahl Rostfrei (ISER) – the Stainless Steel Information Office – was founded as a joint organisation by stainless steel producers, processors, traders, refiners, alloy manufacturers and other interested parties. The aim was to provide company neutral information about this complex material and its varied usages. From the beginning it soon became clear that there was a need to have one single concise collective name from amongst the various terms, norms and marketing names of producers; this became ‘Stainless Rust Free’ shortened to ‘Rust Free’, which then became a registered trade mark used by many stainless steel processors as part of their advertising strategy. The term is however erroneously sometimes used for non rust steels (DIN EN 10088).

S


Scrap

Material with a high metal content, which is used not only as a cooling agent, but also as a secondary raw material in steel production. Scrap can also be alloyed or non-alloyed. Scrap is accrued in a steel works and outside scrap is bought in. There are ten different types of scrap: old scrap, new scrap, heavy old scrap, shredder scrap, waste combustion scrap, waste scrap, steel turnings, bales made of new light sheet scrap and new scrap. The scrap list is neither internationally recognised nor standardised.

Spectral analysis

The process of qualifying chemical elements in steels (qualitative spectral analysis) and of determining their quantity (quantitive spectral analysis). In an active state, each element sends out a collection of rays according to its components. Using a prism the frequency of the various rays can be separated and projected next to one another on a screen, where they can be determined according to position (deflection) and intensity. The position characterises the element, the intensity its mass weight. With a spectroscope the evaluation is determined by the viewer, with a spectrometer by photocells and electronic evaluation. The process releases a discharge.

Stainless Steel

Is a collective term for those steels which have been smelted in a special procedure (secondary metallurgy), have a high purity and react consistently to heat treatment. There are two types according to their chemical properties (DIN EN 10 020); non-alloyed (steel group 10-18) and alloyed (steel group 20-89). It is differentiated according to its use, as structural, engineering, container, tool, high-speed or ball-bearing steel. Steel is also characterised by its properties: chemically resistant, non corrosive, heat resistant, high temperature alloy, suitable for welding purposes, and with special physical or magnetic properties or yield levels.

T


Tantalum

Chemical element, Ta, density 16.6 g/cm³, melting point: 2,995 +/- 25°C. Greyish white, ductile metal with a high chemical stability at room temperature. Is used in its pure form, or as an alloyed additive, for heavy duty parts. Used with Niobium (Nb) as a stabiliser in chemically resistant steels and as tantalum carbide for use in carbides.

Titanium

Chemical element, Ti, density 4.5 g/cm³ (light metal). Ti, with its alloys, is to be found in apparatus and aeroplane assembly thanks to its firmness, low density and high corrosion resistance. Ti is a much used alloy (stabilises steel and stainless construction steel). In austenitic non rust steel it binds the carbon so preventing its separation. Titanium carbides are found in hard wearing stellite types. Titanium oxide (rutile) is used as a welding additive.

Tool steel

Stainless steel of high durability, high corrosion resistance and high toughness suitable for tool making. It must also be able to adjust to wide ranges of temperature change. Tool steel is characterised as cold forming steel (i.e. non-alloyed or low alloyed for surface work at temperatures of less than 200°C), hot-work steel and high speed steel. DIN 17350.

Tungsten

Chemical element W, density 19.3 g/cm. Grey, robust metal, resistant to chemical attacks at room temperature. W is extremely hard with high temperature strength. It is a valuable alloy for steel as it increases corrosion resistance. With cementite it forms carbide, type M3C and M6C. W is especially good for tool steel, providing a good cutting edge, and for permanent magnets. Because of its hardness it is fated to be a hard metal alloy.

Tungsten carbide

Is one of the most important components of hard metal alloys.

V


Vanadium

Chemical element V, density: 6.07 g/cm³. Ductile silvery white metal. In steel V. has the following impact: increases tensile strength, yield and high temperature strength, decreases brittleness. V. produces fine grain material and makes steel impervious to overheating.

Y


Yield

Ratio (in %) of utilisable material to deployed material, e.g. the yield of a smelting oven in total or of an added alloyed element or a rolling mill (of applied weight).

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