First, the magnetic test is the most simple method to distinguish between annealed austenitic stainless steel and ferriticstainless steel pipe. Non magnetic steel is austenitic stainless steel, but the high pressure after cold working with mild magnetic; and pure chromium steels and low alloy steels is strong magnetic steel.
Two. One of the remarkable characteristics of the stainless steel pipes is that the corrosion resistance of concentrated nitric acid and dilute nitric acid is inherent. This property makes it easy to distinguish from most other metals or alloys. However, the high carbon type 420 and 440 steel in the nitric acid point test is slightly affected by corrosion, non-ferrous metals encountered when concentrated nitric acid will be corroded. And dilute nitric acid has strong corrosive to carbon steel.
Third, sulfuric acid copper sulfate test copper test is fast to distinguish between ordinary carbon steel and all kinds of stainless steel pipe is the most simple method. The concentration of copper sulfate solution was 5~10%. Before the test, the test area should be thoroughly cleaned of oil or various impurities, and polishing cloth polishing a small region, then dropping to clean up after the regional drop note copper sulfate solution. Ordinary carbon steel or iron within a few seconds it will form a layer on the surface of copper, and the surface of the stainless steel does not produce copper precipitation or copper color.
Four, sulfuric acid test sulfuric acid immersion stainless steel pipes test can be 302 and 316 and 317 and 304 to distinguish. The cutting edge of the sample should be finely ground, then the volume concentration of 20~30%, temperature of 60~66 c c c (1.42) in the proportion of clean and passivation for half an hour. The volume concentration of sulfuric acid test solution was 10%, heated to 71 degrees when.302 and 304 stainless steel immersed in the hot solution, rapid corrosion and a large number of bubbles, sample within a few minutes of black; and 316 and 317 steel specimens is not subject to corrosion or reaction is very slow (bubble) sample in 10 to 15 minutes do not change color. It can make the test more accurate if the test specimen with known composition is used to make an approximate comparison.
Source: Zhejiang Yaang Pipe Industry Co., Limited (www.yaang.com)