Stainless steel material determination and difference method
At present, the easiest material judgment method on the market is to identify the potion through stainless steel, but a more scientific and reliable method should be to use a spectrum to conduct chemical analysis of the stainless steel composition through a spectral analysis instrument, which can accurately identify the stainless steel material.
The following are some of the more practical identification methods for several common steel grades:
Physical identification of 304 stainless steel: The physical identification of stainless steel plate is to use simple tools to identify the physical and chemical properties of the commodity (including the whole material, residual material, waste, etc.) in the case of unknown steel type (number). A specific method to determine whether it is stainless steel and what kind of stainless steel it belongs to. It should be pointed out that: sensory identification cannot distinguish the specific steel (type) number, but can only basically distinguish three categories of chromium stainless steel, chromium-nickel stainless steel and chromium-manganese nitrogen stainless steel. The identification methods are as follows:
1. The difference in color: After pickling The color of the stainless steel is silver-white and smooth: the color of chrome-nickel stainless steel is silver-white and jade-colored; the color of chrome-nickel stainless steel is slightly grayish and weak; the color of chrome-manganese-nitrogen stainless steel is similar to that of chrome-nickel stainless steel and slightly lighter. The surface color of unpickled stainless steel: chrome-nickel steel is brownish white; chrome steel is brown-black; chrome-manganese nitrogen is black (these three colors refer to the color with heavier oxidation). Cold-rolled unannealed chrome-nickel stainless steel with silver-white reflective surface. In addition to the original steel, stainless steel is generally white after pickling. 2. Identify with copper sulfate: The method is to remove the oxide layer on the steel, put a drop of water, and wipe it with copper sulfate. If it does not change color after wiping, it is generally stainless steel; if it turns purple: non-magnetic high manganese steel, Magnetic ones are generally ordinary steel or low alloy steel. 3. Identification with magnets: Magnets can basically distinguish two types of stainless steel. Because chromium stainless steel can be attracted by magnets in any state; chromium-nickel stainless steel is generally non-magnetic in the annealed state, and some will be magnetic after cold working. However, high manganese steel with higher manganese content is non-magnetic; the magnetic situation of chromium-nickel-nitrogen stainless steel is more complicated: some are non-magnetic, some are magnetic, and some are non-magnetic in vertical and magnetic in transverse. Therefore, although magnets can basically distinguish chromium stainless steel and chromium-nickel stainless steel, they cannot correctly distinguish some steel types with special properties, let alone specific steel grades. The important difference between common 304 stainless steel and 201 stainless steel: At present, the stainless steels sold in the Chinese market are mainly 304 stainless steel and 201 stainless steel. The difference between the two lies in the chemical element nickel content, which results in a huge difference in performance and price. . At the current nickel price level, the price of 201 stainless steel with very low nickel content is only about half of that of 304 stainless steel, and it is far inferior to 304 stainless steel in terms of corrosion resistance and toughness. It is only suitable for kitchen utensils, food processing and other fields. Used in construction, medical equipment and other fields, there will be great hidden dangers. 201 products with a nickel content of about 1% cannot withstand general atmospheric corrosion. On the surface, 201 stainless steel and 304 stainless steel are difficult to distinguish even by experts. At present, some stainless steel water tank enterprises take advantage of the fact that many users cannot identify the authenticity, and sell all or part of the 201 shoddy as 304 series in the water tank, defrauding high profits, and bringing incalculable losses and hidden dangers to users. So that the regular brand water tank business market is blocked. On the surface, 201 stainless steel and 304 stainless steel are difficult to distinguish even by experts. Many users who buy stainless steel doors and windows cannot identify the authenticity of stainless steel materials, which will bring you immeasurable losses and hidden dangers. Here we teach you how to identify the material of stainless steel. For the steel with special properties, we need to take the following three methods to identify it. 1) Grinding identification: Grinding identification is to grind stainless steel on a grinder and watch the sparks. If the spark is streamlined and has more dense knots, it is high manganese steel or manganese nitrogen steel with higher manganese content; if there is no knot, it is chrome steel or chrome-nickel stainless steel. 2) Identification by annealing method: For cold-worked chrome-nickel stainless steel, if there is magnetism, you can take a small piece to burn red in the fire and let it cool naturally or put it in water (annealing). Generally speaking, after annealing, the magnetism will be significantly weakened or completely disappear. However, some chromium-nickel stainless steels, such as Cr18Ni11Si4AlTi steel and Cr21Ni5Ti steel, contain a lot of ferrite elements, and a considerable part of their internal structure is ferrite. Therefore, it is magnetic even in the hot-worked state. 3) Identification by chemical qualitative method: The chemical qualitative method is an identification method to identify whether the magnetic stainless steel contains nickel. After neutralization, the nickel reagent is gently injected. If there is a red velvet substance floating on the liquid surface, it means that the stainless steel contains nickel; if there is no red velvet substance, it means that there is no nickel in the stainless steel. (However, due to the low nickel content in stainless steel, generally only a few percent, the nickel content is not easy to reveal or determine how much, and generally it can only be mastered after several experiments with standard samples.) Stainless steel not only needs to be comprehensively tested by several methods, but the test results can only determine a certain type of stainless steel, but cannot determine which alloy elements and specific contents are contained in the steel. Therefore, the method of sensory identification is currently extremely imperfect, and some may be wrong, and there are many physical phenomena, which are only known but unknown, and need to be further explored. The best way to correctly distinguish stainless steel grades is to go deep into the relevant processing units for investigation and research, ask their material managers and workers for advice, understand the steel grades of the materials, carefully check the steel number marks on the steel, and consult the original This is the fundamental method to correctly distinguish the grade and quality of stainless steel. For alloy elements and their contents with large differences, they are required to be stacked separately to facilitate rational utilization and avoid unnecessary losses and waste. Stainless steel has a lot of materials, but the commonly used materials are 304/304j/ 304L/316/316L/321/310S 410/420/420J1/420J2/430/ 201/202 As for how to identify the quality of stainless steel, if you personally identify stainless steel It is impossible to identify which material it is, and it must be determined by chemical analysis. Some such as 400 series and 300 series can be identified by magnetic identification, 400 series is generally magnetic, 300 is generally not magnetic.
