Sabtu, 06 Desember 2014

Guide To Stainless Steel Fabricator

By Claudine Hodges


Stainless-steel has a big role in countless areas: daily life, mechanical, food, chemical, transportation, medicine, surgery, etc. This is a family of steels, iron alloys, and carbon, in which chromium is essentially added, which, beyond 10.5% solution (based on carbon content) in die, causes the formation of protective layer of chromium oxide which gives these steels their corrosion resistance (stainless steel fabricator).

Other elements may be added, in particular nickel, which improves the mechanical properties in general and particularly ductility, and other elements such as molybdenum or titanium, which enhance the stability of alloy at temperatures other than room as well as elements with high melting points such as vanadium and tungsten in general accompanied by an increase in chromium content, for resistance to high temperatures ignited (refractory steels).

Stainles-steels are steels with added chromium. In accordance with the European standard EN 10088-13, a stainles-steel is classified if it contains at least 10.5 wt% chromium and less than 1.2% carbon. The carbon content is limited to a maximum of 1.2% by mass to avoid carbures4 training (including chromium carbides which is a very stable chemical compound hungry chrome) that are harmful to material.

In 1890s, the German Hans Goldschmidt developed and patented a process called thermite which allowed to obtain carbon-free iron. Between 1904 and 1911, various researchers, including the French Leon Guillet, devised various alloys that could today be considered stainles. In 1911, German Philip Monnartz highlighted the influence of chromium alloys rate and resistance to corrosion.

Manganese is a nickel substitute. Some series of austenitic alloys have been developed to deal with supply of nickel6 uncertainties. Molybdenum and copper improve the resistance in most corrosive environments, particularly those that are acidic, but also in phosphate solutions, sulfur, etc. Molybdenum increases the stability of passivation films.

There are actually numerous grades of stainles-steels and the choice is difficult because they do not all have the same behavior in a given environment. Are often referred to by the weight percentages of nickel and chromium. Thus, a 18/10 stainles-steel, such as those used in cutlery for cutlery and for cooking in general, contains 18% by weight of chromium and 10% by weight of nickel.

This designation is actually very insufficient because it does not prejudge the metallurgical structure. Stainles-steels can corrode if not using the right shade compared to room environment (chemical composition of environment, temperature), or if the passive layer is not formed before the in room service:

The metal is exposed (grinding, machining, deformation of workpiece cracking the passive layer, friction, erosion, cavitation), but the oil or grease prevents air arriving to oxidize; then the surface is "active". Non-stainles-steel particles pollute the surface (pollution iron): these particles rust, forming halos, but can also initiate corrosion of stainless-steel in some cases.




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