austenitic materials and austenitic stainless steel

You can share such steel grade in three main groups:

•      normal austenitic steels, non-stabilized, with increased carbon  content, heat resistant;
•      stabilized austenitic steels;
•      austenitic steels with low carbon content.

You have no transition points A1 and A3, ie they have a pure austenitic Struktur. Man distinguishes two groups:

1. Fe-C-Cr-Ni

2. Fe-C-Cr-Ni-Mo

After AISI as "Series 300" means.
AISI 301-302 - 302B - 304-305 - 308-384

They differ from Ni content. If the Ni content is larger, the work hardening is reduced during processing. Such steels have normal room temperature properties, but very good at very low temperatures (especially impact strength); In addition, they have high fatigue strength, low sensitivity for incisions.
AISI 309 - 309S - 310-314

With high nickel content. Heat-resistant steels. Very good properties as regards corrosion resistance and mechanical properties at high temperatures.
AISI 316-317

With Mo, which has good resistance to Grübchenbildungskorrosion and "stress corrosion" result. Better mechanical properties at high temperatures.
AISI 321 - 347-348

So-called stabilized steels. They originate from the 304 and 316 with titanium and niobium. The most important property is that such steels avoid the formation of chromium oxides, and consequently a better corrosion resistance is ensured. Feature element is the titanium content (about 0.3-0.4%).
AISI 304L - 316L

Variants of 304 and 316, wherein in these steels, the carbon content is lower (<= 0.03%), so that the carbide precipitation becomes so large at temperatures of 450-850 ° C that the formation is made possible of welded structures, without any precipitation of carbides within the welded spots. Similar properties at room temperature, low properties at higher temperatures.
AISI 316SL (Basel Norm)

High molybdenum content (> = 2.5%).
Very good general corrosion resistance properties.
resolution capability

It heats the steel at a high enough temperature so that the native of processing methods strukturalische change can be eliminated; With this method, the material remains in a certain temperature, which (especially the chromium carbides) to connect all carbides with the solution, as well as the cooling procedure must be slow enough to carbide precipitation (happening between 450 and 850 ° C) to avoid. As a result, the steel is in the maximum Erweichungslage. Three factors play an important role, namely the temperature (about 1000-1100º C), speed of treatment (depending on the thickness of the material) and the speed of cooling. At such a temperature, a recarburising on the surface is very likely for austenitic steels, which means that the risk of carbide precipitation is quite large (one must also consider whether the atmosphere is not carburized in the oven). The cooling must be done quickly. By recrystallization annealing at high temperatures to obtain a larger grain dimension; thus the corrosion can be even harder.
Sensitization to intergranular corrosion

One method that is used only in the laboratory to determine the sensitivity of IK-corrosion. In steels from the groups "normal austenitic steel" is carried out at a temperature between 450 and 850 ° C a Chromkarbidausscheidung, with corresponding thereto reduction of the chromium content, and therefore a higher probability of IK-corrosion. In order to avoid such a problem, one uses stabilized elements, such. As titanium and niobium, the easier combine with carbon than with chromium. Thus, the depletion of free chromium in the alloy is avoided, and therefore it prevents the sensitization of the steel (in this case, is to raise awareness among 1250-1300º C).
relaxation

Thus, the internal stresses resulting from the production process are eliminated. For spring steels (extremely hard material), the breaking load is made larger by an expansion to increase the elastic properties, with heat treatment at 450 ° C (temperature of Sensibilisierungshärtbargkeit). Since the material thickness is a few tenths of a millimeter is the time of heat treatment is very short (a few seconds). The relaxation is complicated for welded materials. Need to beiseitigen voltages for such materials to anneal the material, then there during cooling of the welded spots the risk of "stress corrosion".