Experimental methods of four stainless steel rod manufacturers

Nowadays, stainless steel has been used in various fields, so the selection of materials is very important. In order to better identify fake and inferior stainless steel materials, certain countermeasures and methods can be adopted. The following are four organic chemical identification methods for stainless steel rods.

1. 304 Stainless steel rod magnetization test method - The magnetization test method is a common and simple way to distinguish martensitic stainless steel from stainless steel with metallographic structure. Martensitic stainless steel is non-magnetic steel, but after cold drawing under high pressure, it will have Slightly magnetized; while pure manganese steel and high alloy steel are both strongly magnetized steel.

2. Sodium cyanide spot test method - A distinctive feature of stainless steel is its inherent corrosion resistance to concentrated sulfuric acid and dilute nitric acid. This characteristic makes it easy to test from most other plastics or aluminum alloys. the difference. However, high-nitrogen 420 and 440 steels were slightly corroded during sodium cyanide testing. Rare metals were corroded immediately when exposed to concentrated sulfuric acid, while 304f stainless steel rods were corroded by dilute nitric acid, which is obviously corrosive to carbon steel.

3. Sodium thiosulfate spot test method - Sodium thiosulfate spot test is a simple way to quickly distinguish carbon structural steel from all types of stainless steel. The concentration of sodium thiosulfate solution used is 5%-10%. Before conducting the point test, the test area should be completely removed from oil or other residues, and a small area should be polished with an electric grinder or soft grinding cloth, and then the test liquid should be applied to the polished area. The carbon structural steel or iron should be polished in a few seconds. A layer of surface metallic copper will be formed inside, while the surface of the stainless steel will not produce copper deposition or show the color of copper.

4. Hydrochloric acid test - hydrochloric acid soaked stainless steel can distinguish 302 and 304, 316 and 317. The trimmed edge of the 316l stainless steel rod sample must be finely ground, and then the mass concentration value is 20%~30% and the temperature is 60~66℃ Clean and passivate in hydrochloric acid for thirty minutes. The volume concentration of the sulfuric acid solution is 10%. When heated to 71°C, 302 and 304 penetrate into the aqueous solution. The steel is quickly corroded and a lot of bubbles are formed. The sample in some species The inside turns black; while the samples of 316 and 317 steel will not be corroded or corrode relatively slowly (no bubbles are caused), and the test will not fade within 10 to 15 minutes. The test can be made more accurate if samples with known compositions are tested at the same time for similar comparisons.