Common identification methods of stainless steel flanges
Stainless steel flanges can be said to play a role in many aspects of our lives, you know, stainless steel flanges are the most common disk in pipeline engineering. Stainless steel flanges are used in pairs, with matching flanges on the valve. In pipeline engineering, flanges are mainly used for pipeline connection. Here we introduce several chemical identification methods!
1, magnetic measurement method: magnetic measurement method is the original and commonly used simple method to distinguish austenitic stainless steel and ferritic stainless steel. Austenitic stainless steel is a non-magnetic steel, but it produces a slight magnetism after cold working under high pressure. Pure chromium steel and low alloy steel are strong magnetic steel.
2, copper sulfate spot test method: copper sulfate spot test is the easiest way to quickly distinguish ordinary carbon steel and all types of stainless steel. The concentration of copper sulfate solution used is 5%-10%. Before the drop test, the oil or other impurities in the test area should be thoroughly removed, and a small area should be polished with a grinder or soft abrasive cloth, and then the test liquid should be dropped to the polishing place. Ordinary carbon steel or iron will form a layer of copper on the surface in a few seconds, while stainless steel will not produce copper precipitation or show the color of copper.
3, nitric acid spot test method: A remarkable feature of stainless steel flange is that it has inherent corrosion resistance to concentrated nitric acid and dilute nitric acid. This property makes it easily distinguishable from most other metals or alloys, but high-carbon 420 and 440 steels suffer slight corrosion in nitric acid spot tests. Non-ferrous metals are immediately corroded when they encounter concentrated nitric acid, while dilute nitric acid is strongly corrosive to carbon steel.
4, sulfuric acid test method: stainless steel sulfuric acid soaking can distinguish 302, 304 and 316, 317. The cutting edge of the sample should be finely ground, and then washed and passivated in sulfuric acid with a volume concentration of 20%-30% and a temperature of 60-66°C for half an hour. The volume concentration of sulfuric acid solution is 10%, heated to 71 ° C, 302 and 304 are immersed in the solution, the steel is rapidly corroded, and a large number of bubbles are produced. The samples turned black in a few minutes, while the 316 and 317 steel samples were not corroded or corroded very slowly (no bubbles). The test will not change color for 10-15 minutes. The test can be more accurate if samples with known components are tested at the same time for approximate comparison.