How to distinguish the fake and inferior stainless steel materials
Nowadays, many industrial products are made of stainless steel wire rope. In order to identify the fake and inferior stainless steel materials, certain measures and methods can be taken. However, many customers do not know what methods can be used for identification. Here are the following identification methods.
1. Magnetic test method
Magnetic test method is a common and simple method to distinguish austenitic stainless steel from ferritic stainless steel. Austenitic stainless steel is non-magnetic steel, but it will have slight magnetism after cold working under high pressure; Pure chromium steel and low alloy steel are both strong magnetic steel.
2. Nitric acid point test
A remarkable feature of stainless steel wire rope is its inherent corrosion resistance to concentrated nitric acid and dilute nitric acid, which makes it easy to distinguish it from most other metals or alloys.
However, the high-carbon 420 and 440 steels are slightly corroded during the nitric acid point test. Nonferrous metals are immediately corroded when they encounter concentrated nitric acid, while dilute nitric acid has strong corrosivity to carbon steel.
3. Copper sulfate spot test
Copper sulfate spot test is a simple method to quickly distinguish ordinary carbon steel and all types of stainless steel wire rope. The concentration of copper sulfate solution used is 5% – 10%. Before spot test, the test area should be thoroughly cleaned of oil or other impurities, and a small area should be polished with a grinder or soft abrasive cloth, and then the test solution should be dropped to the polishing point. Ordinary carbon steel or iron will form a layer of surface metal copper within a few seconds, However, the surface of stainless steel for spot test does not produce copper precipitation or show copper color.
4. Sulfuric acid test method
Sulfuric acid immersion stainless steel can distinguish 302 and 304 from 316 and 317. The cut edge of the sample shall 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. The volume concentration of sulfuric acid solution is 10%. When heated to 71 ℃, 302 and 304 are immersed in the solution, the steel is rapidly corroded and a large number of bubbles are produced, and the sample turns black in a few minutes; However, the samples of 316 and 317 steel are not subject to corrosion or slow corrosion (no bubbles), and do not change color within 10-15 minutes. If the sample with known composition is tested at the same time for approximate comparison, the test can be more accurate.
