Mechanické vlastnosti nehrdzavejúcej ocele

Mechanické vlastnosti

Austenitická nehrdzavejúca oceľ má najnižšiu medzu klzu zo všetkých ocelí. Preto z hľadiska mechanických vlastností nie sú austenitické nehrdzavejúce ocele tým najlepším materiálom pre driek ventilu, pretože na zabezpečenie určitej pevnosti by sa mal priemer drieku ventilu zväčšiť. Medza klzu sa nedá zvýšiť tepelným spracovaním, ale dá sa získať tvárnením za studena.

magnetický výkon

Due to the wide application of austenitic stainless steel, many of us have false impression that all stainless steel has no magnetic. For austenitic stainless steel, this can be understood as non-magnetic, because it is true that the forged steels have no magnetic after quenched, but SS304 will be somewhat magnetic after cold forming. For casting stainless steel, if the material is 100 percent Austenitic stainless steel, then it is no magnetic. 

Nerezová oceľ s nízkym obsahom uhlíka

The corrosion resistance of austenitic stainless steel comes from the oxidation chrome protective layer formed on metal surface. If the material is heated to a high temperature of 450 degree to 900 degree , the structure of the material will change, and carbide will form along the edge of the crystal. In this way, the protective layer of magnesium oxide cannot be formed on the edge of the crystal, which decreases the corrosion resistance. This corrosion is called "intergranular corrosion".

As a result, 304L stainless steel and 316L stainless steel were developed to combat this corrosion. Both 304L stainless steel and 316L stainless steel have lower carbon content, so there will be no carbonization problem, and the "Intergranular corrosion" will not occur.

Je potrebné poznamenať, že citlivosť medzi vyššou medzikryštálovou koróziou neznamená, že materiály s nízkym obsahom uhlíka ľahšie korodujú. V prostredí s vysokým obsahom chloridov je táto citlivosť vyššia.

Please note that this phenomenon is due to high temperature (450 degree -9000c), and usually soldering is the direct reason to reach such high temperature. For soft seat butterfly valve, since we do not proceed welding on the valve plate, it doesn't make much sense to use low carbon stainless steel, while most specs will require also 304L stainless steel or 316L stainless steel.

Prečo hrdzavie aj nehrdzavejúca oceľ?

Why does stainless steel also rust? When brown rust spots appear on the surface of stainless steel pipes, people were amazed: "Stainless steel is not rusted, the rusted one is not stainless steel, it may be some problems with the steel", while it is just false conception of stainless steel, because stainless steel is also rusted under specific circumstances.