Why does the stainless steel flange also have micro-magnetism?

Under normal circumstances, stainless steel flange products cast from non-magnetic 304 stainless steel scraps are slightly magnetic. What causes it? 1. The chemical composition equivalent composition control is not in place.
In order to reduce the cost, generally stainless steel flange manufacturers control the lower limit of Ni, between 8.0-8.2%. When Cr/Ni reaches a certain value, a certain amount of ferrite appears in the steel structure, and ferrite is magnetic; at this time Using solid solution treatment at 1050~1080°C can completely dissolve ferrite into austenite and there will be no magnetism. 2. Cold work hardening.
When austenitic stainless steel produces deformed martensite during cold working, deformed martensite increases the strength of stainless steel, and deformed martensite is magnetic. The deformed martensite can be disappeared by solution treatment or even annealing, but the strength of the steel will decrease.
Stainless steel flanges have good metal properties and strong corrosion resistance. They are often used in steel structural parts, such as stainless steel flanges. Stainless steel flanges are also stainless acid-resistant steel flanges. Its metal surface is smooth, It is not easy to oxidize with air, so it is often used in high-pressure water pipes and corroded pressure pipes. Stainless steel flanges have excellent performance.
First of all, as a metal material, it will react with air in a humid environment, thereby changing the original metal properties, but stainless steel flanges can passivate with oxidants, forming a tough and dense chromium-rich oxide protective film on the surface Cr203, stainless steel flange effectively prevent further oxidation reaction. Other metal pipes, such as galvanized water pipes and copper pipes, have very little passivation ability, which is the key reason why the corrosion resistance of copper pipes of galvanized pipes is far inferior to that of stainless steel pipes. Then the corrosion resistance performance of the stainless steel flange is good. The stainless steel flange will not be uniformly corroded like carbon steel, and no protective coating is required when using it; It has good corrosion resistance in water with various oxygen content, temperature, PH and hardness; stainless steel water pipe can withstand high flow velocity, even if the flow velocity is greater than 40 m/s, it still maintains an extremely low corrosion rate, not exceeding 0.003 mm/s Years, especially suitable for high-rise water supply. The thermal expansion coefficient of stainless steel flange pipe is similar to that of copper pipe, which is 1.5 times that of ordinary steel pipe. In contrast, stainless steel flange pipe fittings have the characteristics of slow thermal expansion and cold contraction.
In addition, the chemical reactions of stainless steel flanges are generally integral, and a protective film will be formed on its surface, which is impossible for other metals.