E sad, stainless steel u nasim jezicima je preveden kao nerdjajuci celik, sto je opsti pojam za leguru koja pored ostalih komponenti sadrzi hrom, i to bukvalno hromsku ili neku drugu presvlaku koja sprijecava koroziranje materijala. Zamislite da je legura takvog sastava i da ima malo hroma u svojoj sredini, malo na krajevima, malo ovdje i malo ondje. Naravno da bi materijal zardjao. Sa presvlakom to nije slucaj. Presvlaka pokriva citavu vanjsku povrsinu i time stvara nerdjajuci sloj. Kolegica Vesna je bila na dobrom putu pokusavajuci objasniti da je to nerdjajuci celik, sto u svojoj osnovi taj materijal to i jeste ali nije bila dovoljno precizna u odgovoru. Ja nisam navodio reference jer sam iz razno raznih razloga sto hiljada posto siguran u svoj prijedlog i ja bih ga licno i upotrijebio ne brinuci se nijedne sekunde o tome da je to mozda greska.
Posto Vesna u svom prijedlogu kopira samo dio Webstera prohrom i inox, ja ga donosim u cijelosti, pa sami razaberite da li se radi u mucenju secera i vode ili pravljenju legura.
Ograde i Kapije od Prohroma
In metallurgy, stainless steel is defined as a ferrous alloy with a minimum of 10.5% chromium content. Such steels have higher resistance to oxidation (rust) and corrosion in several environments. It was invented in 1912, at the research laboratory of Brown-Firth, Sheffield, England by Harry Brearley. He had been investigating ways to reduce corrosion in gun-barrels, when it was noticed that a discarded sample was not rusting.
High oxidation resistance in air at ambient temperature is normally achieved with additions of more than 12%(weight) chromium. The chromium forms a layer of chromium (III) oxide (Cr2O3) when exposed to oxygen. The layer is too thin to be visible, meaning the metal stays shiny. It is, however, impervious to water and air, protecting the metal beneath. Also, when the surface is scratched this layer quickly reforms. When stainless steel parts such as nuts and bolts are forced together, the oxide layer can be scraped off causing the parts to weld together. This effect is known as galling.
There are different types of stainless steels: when nickel, for instance is added the austenite structure of iron is stabilized and these steels become non-magnetic. For higher hardness and strength, carbon is added. When subjected to adequate heat treatment these steels are used as razor blades, cutlery, tools etc.
In recent decades, significant quantities of manganese have come to be used in many stainless steel recipes. Manganese imparts similar qualities to the steel as does nickel, but at a lower cost.
Stainless steels are also classified by their crystalline structure:
Austenitic stainless steels comprise over 70% of total stainless steel production. They contain a maximum of 0.15% carbon, a minimum of 16% chromium and sufficient nickel and/or manganese to retain an austenitic structure at all temperatures from the cryogenic region to the melting point of the alloy. A typical composition is 18% chromium and 8% nickel, commonly known as 18/8 stainless.
Ferritic stainless steels are highly corrosion resistant, but far less durable than austenitic grades and cannot be hardened by heat treatment. They contain between 10.5% and 27% chromium and very little nickel, if any. Most recipes include Molybdenum; some, aluminum or titanium. Common ferritic grades include 18Cr-2Mo, 26Cr-1Mo, 29Cr-4Mo, and 29Cr-4Mo-2Ni.
Martensitic stainless steels are not as corrosion resistant as the other two classes, but are extremely strong and tough as well as highly machineable, and can be hardened by heat treatment. They contain 11.5 to 18% chromium and significant amounts of carbon. Some grades include additional alloying elements in small quantities.
The AISI defines the following grades:
200 Series – austeniitic iron-chromium-nickel-manganese alloys
300 Series – austeniitic iron-chromium-nickel alloys
Type 301 – highly ductile, for formed products
Type 303 – equivalent to ISO  A1.
Type 304 – the most common; austenitic (contains nickel); equivalent to ISO A2.
Type 316 – for food and medical uses; contains nickel and molybdenum; also called 18-8; equivalent to ISO A4.
400 Series – ferritic and martensitic alloys
Type 408 – heat-resistant; poor corrosion resistance; 11% chromium, 8% nickel.
Type 409 – cheapest type; used for automobile exhausts; ferritic (iron/chromium only).
Type 410 – martensitic (high-strength iron/chromium); equivalent to ISO C1.
Type 420 – \”Cutlery Grade\” martensitic; similar to the Brearley\’s original \”rustless steel\”.
Type 430 – decorative, e.g. for automotive trim; ferritic.
Na kraju krajeva, sam izraz prohromski upucuje da materijal sadrzi odredjen postotak hroma. Znaci nije hromski nego prohromski, nesto sto naginje hromu ali nije cisti hrom iz razloga sto takav materijal ne bi imao potrebnu tvrdocu i elasticnost, tj potreban kvalitet za svrsishodnost u krajnjoj upotrebi.
U vasem konkretnom slucaju, odgovarajuca vrsta nerdjajuce legure jeste
300 Series – austeniitic iron-chromium-nickel alloys
Type 316 – for food and medical uses; contains nickel and molybdenum; also called 18-8; equivalent to ISO A4
Austenite is a solid solution of carbon and iron that exists in steel above the critical temperature of 1333°F (about 723°C). It is named after Sir W.C. Roberts-Austen. Its face-centred cubic (FCC) structure allows it to hold a high proportion of carbon. As it cools, it breaks down into other materials such as pearlite (a mixture of ferrite and cementite), martensite and bainite. The rate of cooling determines the relative proportions of these materials and therefore the mechanical properties (e.g. hardness, tensile strength) of the steel.
The addition of certain other metals, such as manganese, nickel and chromium, can cause the austenitic structure to survive at room temperature, resulting in austenitic steel.
Nisam nasao adekvatan prijevod za austenitic, jer je sam pojam nazvan po osobi, pa bi mozda u nasim jezicima to zvucalo nesto kao austenski (ostenski), ili mozda austenov (ostenov).
Uglavnom, jedna od podgrupa je hromirana legura celika, znaci chrome-pated steel ili chromium plated steel. Sto se tice vaseg pitanja, ne treba ici toliko u krajnost, osim ako to daljnji tekst ne zahtijeva.
Kako god, sad sam dao reference, samo da pojasnim zasto pokusavam ne biti puno slozen i komplikovan.