Nowadays, many industrial products are made of stainless steel. In order to identify fake and inferior stainless steel, certain measures and methods can be taken. But many don't know what method to use to identify. Huiyingsteel here lists four chemical identification methods for stainless steel bars to help you better identify the quality of stainless steel bars.
1. Magnetic test method to identify stainless steel bars
The magnetic test method is the most primitive and common method to distinguish austenitic stainless steel rods from ferritic stainless steel rods. Austenitic stainless steel is non-magnetic steel, but it will have mild magnetic properties after cold working under high pressure. ; pure chromium steel and low alloy steel are strong magnetic steel.
2. Nitric acid point test method to identify stainless steel bars
A distinctive feature of stainless steel is its inherent corrosion resistance to concentrated and dilute nitric acid, a property that allows it to be easily distinguished from most other metals or alloys. However, stainless steel bars made of high-carbon 420 and 440 sheets of steel are slightly corroded during the nitric acid spot test, and non-ferrous metals are immediately corroded when they encounter concentrated nitric acid while diluting nitric acid is strongly corrosive to carbon steel.
3. Stainless steel bars can be identified by the copper sulfate point test method
The copper sulfate point test is the easiest way to quickly distinguish between ordinary carbon steel and all types of stainless steel. The concentration of copper sulfate solution used is 5%-10%. Before the point test of stainless steel bars, the test area should be thoroughly Removed oil or other impurities, and use a grinder or soft abrasive cloth to polish a small area, and then drop the test solution on the polished stainless steel bar, ordinary carbon steel or iron will form a layer of surface metal copper in a few seconds, while the spot test stainless steel surface does not produce copper precipitation or show the color of copper.
4. Stainless steel bars can be identified according to the sulfuric acid test method
A sulfuric acid immersion stainless steel bar can distinguish 302 and 304 from 316 and 317. The cut 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°C for half an hour. The volume concentration of the sulfuric acid solution is 10% and heated to 71°C. When 302 and 304 stainless steel rods are immersed in the solution, the steel is rapidly corroded and produces a large number of bubbles, and the sample turns black within a few minutes; while the stainless steel rods made of 316 and 317 steel are not corroded or corroded very slowly ( No air bubbles are produced), and the test does not change color within 10 to 15 minutes. Stainless steel bar tests can be made more accurate if approximate comparisons are made by simultaneously testing samples of known composition.
I hope the above methods can help you better identify the material and quality of stainless steel bars. For more information about stainless steel bars, please refer to our news column.
