304 stainless steel pipes contain more than 18% chromium and more than 8% nickel, which are also two important elements that determine the value of 304 stainless steel pipes. The metal has good toughness, plasticity, and corrosion resistance, and is also widely used. However, the quality of stainless steel on the market is uneven, there are inferior products and counterfeits, which makes many buyers not know where to start. The following is the detection method for 304 stainless steel pipes:
1. Friction spark identification method: Use 304 material and 202 material respectively, put them on a high-speed rotating grinding wheel to see the sparks generated. Due to the high temperature of friction, the number of sparks generated when various element particles are oxidized, the shape of the bifurcation, etc. are different to identify the chemical composition and approximate content of the material.
2. Copper sulfate identification method: Remove the oxide layer on the 304 stainless steel pipe, put a drop of water on it, and rub it with copper sulfate. If it does not change color after rubbing, it is generally stainless steel; if it turns purple-red, non-magnetic is high manganese steel, and magnetic is generally ordinary steel or low alloy steel.
3. Chemical qualitative method: It is a method to identify whether magnetic stainless steel pipes contain nickel. The method is to dissolve a small piece of stainless steel in aqua regia, dilute the acid with clean water, add ammonia water to neutralize it, and then gently inject the nickel reagent. If there is a red velvety substance floating on the liquid surface, it means that the stainless steel contains nickel; if there is no red velvety substance, it proves that there is no nickel in the stainless steel (but because the nickel content in stainless steel is low, generally only a few percent, the nickel content is not easy to show or determine, generally it is necessary to use standard samples for multiple experiments before it can be mastered).
The above methods are all sensory identification of 304 stainless steel pipes. Not only do they need to be tested comprehensively with several methods, but the test results can only determine a certain type of stainless steel pipe, and cannot determine which alloy elements and specific contents are contained in the steel.
Therefore, the sensory identification method is currently extremely imperfect, some may be wrong, and there are many physical phenomena that are only known but not known, which need further discussion.
The most authoritative is the spectral detection method, and instrument identification is the safest and most accurate method. First, use a grinder to remove a layer of the surface, but the surface must be flat, and then use a spectrometer to read the metal elements in the material in detail, and then compare the material. This method is the most reliable.
We can choose some formal channels in the process of purchasing stainless steel pipes. If we purchase 304 stainless steel pipes in large quantities, we should try to choose those with several years of experience. In addition, for large-scale purchases, we can ask 304 stainless steel manufacturers to provide material test reports. We only need to compare the content of each metal component.
Post time: Apr-28-2025