مشخصات مکانیکی
فولاد زنگ نزن آستنیتی کمترین نقطه تسلیم را در بین تمام فولادها دارد. بنابراین با توجه به خواص مکانیکی، فولادهای زنگ نزن آستنیتی بهترین ماده برای میل سوپاپ نیستند، زیرا برای اطمینان از استحکام معین، باید قطر میل سوپاپ را افزایش داد. نقطه تسلیم را نمی توان با عملیات حرارتی افزایش داد، اما می توان آن را با شکل دهی سرد به دست آورد.
عملکرد مغناطیسی
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.
فولاد ضد زنگ نوع کم کربن
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.
باید توجه داشت که حساسیت بین خوردگی بین دانهای بالاتر به این معنی نیست که مواد کم کربن راحتتر خورده میشوند. در محیط با کلرید بالا، این حساسیت بیشتر است.
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.
چرا فولاد ضد زنگ نیز زنگ می زند؟
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.
