Now many industrial products will be made of stainless steel. In order to identify fake and inferior stainless steel, certain measures and methods can be taken. But many do not know what method can be used to identify, the following four chemical identification methods on stainless steel rod.
1, magnetic test method – magnetic test method is the most original and most common distinction between austenitic stainless steel and ferritic stainless steel is the simplest method, austenitic stainless steel is not magnetic steel, but after large pressure cold processing will have mild magnetic; And pure chromium steel and low alloy steel are strong magnetic steel.
2, nitric acid spot test – a significant feature of stainless steel is the inherent corrosion resistance of concentrated and dilute nitric acid, which enables it to be easily distinguished from most other metals or alloys. However, high carbon 420 and 440 steels are slightly corroded in nitric acid point test, and non-ferrous metals are corroded immediately in concentrated nitric acid, while dilute nitric acid has a strong corrosive effect on carbon steel.
3, copper sulfate test – copper sulfate points test is quick to distinguish between ordinary carbon steel and the easiest way of all types of stainless steel, the use of the concentration of a solution of copper sulfate is 5% – 10%, before the point tests, test area should be thoroughly remove oil and other impurities, cloth or soft grinding polishing and grinding machine small area, and then try the droplets to burnish, ordinary carbon steel or iron on A layer of surface metal copper is formed in a few seconds, while the surface of the stainless steel is not precipitated or colored.
4, sulfuric acid test method – sulfuric acid immersion stainless steel can distinguish 302 and 304 from 316 and 317. The cutting edge of the sample should be finely ground, and then cleaned and passivated in sulfuric acid with a volume concentration of 20%~30% and a temperature of 60~66℃ for half an hour. When the volume concentration of sulfuric acid solution is 10% and heated to 71℃,302 and 304 are immersed in the solution, the steel is rapidly corroded and produces a large number of bubbles, and the sample becomes black in a few minutes. While 316 and 317 steel samples are not corroded or corroded very slowly (no bubbles), the test within 10~15 minutes do not change color. The test can be more accurate if the sample with known composition is used for approximate comparison.