Stainless steel identification agent is used to detect the nickel content of steel to distinguish which series of stainless steel. There are a variety of specifications to quickly detect 200 series, 300 series, 400 series and other stainless steels. The method of using the stainless steel identification agent is very simple, just drop it directly on the stainless steel plate. The stainless steel identification agent usually takes about 2-3 minutes to have an effect. Different colors correspond to different types of stainless steel materials.

The one that turns red in about 10 seconds is ordinary 201 stainless steel (manganese exceeds the standard); the one that turns red in about 50 seconds is authentic 201 stainless steel (manganese exceeds the standard); the one that turns red in about 1 minute is 202 stainless steel (manganese exceeds the standard); 301 stainless steel is in 2-3 It will turn red within minutes, but the color is very light, you need to look carefully; if there is no change in the color within 3 minutes, and the bottom color becomes slightly darker, this is the authentic SUS304 stainless steel. Generally, the stainless steel identification agent is equipped with a contrast color card, and the identification result can be directly compared to know the model of the stainless steel plate, which is very convenient.

Second, distinguish 304 stainless steel by magnetism

In the stainless steel market, people still have misunderstandings about 304 stainless steel. Some people think that if you use a magnet to attract stainless steel, only stainless iron can be attracted, but stainless steel cannot be attracted. Good stainless steel has no magnet. However, from this point of view, I will make a judgment for everyone below, how to distinguish 304 stainless steel through this magnetic property.

First of all, we know that 304 stainless steel belongs to the austenitic type, but the austenitic type is non-magnetic or weakly magnetic, so everyone will think that a good stainless steel is non-magnetic. However, one thing that people have missed is that 304 stainless steel may appear magnetic when its chemical composition fluctuates or its processing state is different during the smelting process, but this cannot be considered a counterfeit or substandard product; in addition, 304 stainless steel undergoes cold processing, and its structure will also be To Martensite transformation, the greater the degree of cold working deformation, the more martensite transformation, and the greater the magnetic properties of the steel.

On the contrary, the 200 series stainless steel of lower quality is likely to be non-magnetic, so it is a big mistake to judge that it is genuine stainless steel. In particular, the magnetism of 304 stainless steel caused by the above-mentioned reasons is not at the same level as other materials of stainless steel, which means that the magnetism of 304 steel always shows weak magnetism.

This tells us that if the stainless steel is weakly magnetic or not magnetic at all, it should be judged as 304 or 316 material; if it is the same as carbon steel, it shows strong magnetism, because it is judged as not 304 material.

Three, use copper sulfate to identify

Remove the oxide layer on the steel, put a drop of water, wipe it with copper sulfate, if it does not change color after wiping, it is generally stainless steel; if it turns purple, non-magnetic is high manganese steel, and magnetic is generally ordinary steel or low alloy steel.

For steel grades with special properties, we still need to take the following three methods for identification.

Cold-worked chromium-nickel stainless steel, if it has magnetism, can take small pieces and burn them in a fire to cool it naturally or put it in water (annealing). Generally speaking, the magnetism will be significantly weakened or disappear completely after annealing. However, some chromium-nickel stainless steels, such as Cr18Ni11Si4AlTi steel and Cr21Ni5Ti steel, contain more ferrite elements, and a considerable part of their internal structure is ferrite. Therefore, it is magnetic even in the state of hot working.

Four, grinding flower identification

Grinding identification is to grind stainless steel on a grinder and observe 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 are no knots, it is chromium steel or chromium-nickel stainless steel.

5. Identification by chemical qualitative method

Chemical qualitative method is an identification method to identify whether nickel is contained in magnetic stainless steel. The method is to dissolve a small piece of stainless steel in aqua regia, dilute the acid with purified water, add ammonia to neutralize it, and then gently inject the nickel reagent. If there is a red velvet-like substance floating on the liquid surface, it means that the stainless steel contains nickel; if there is no red velvet-like substance, it means that there is no nickel in the stainless steel (but due to the low nickel content in stainless steel, generally only a few percent, nickel The content is not easy to reveal or determine how much, generally it can be grasped after several experiments with standard samples).

Expand the information

304 stainless steel is a common material in stainless steel, with a density of 7.93 g/cm3, which is also called 18/8 stainless steel in the industry. It can withstand high temperature of 800℃, has good processing performance and high toughness. It is widely used in industry and furniture decoration industry and food and medical industry.

The common labeling methods on the market are 0Cr18Ni9 and SUS304. Among them, 0Cr18Ni9 generally means national standard production, 304 generally means ASTM standard production, and SUS 304 means Japanese standard production.

304 is a versatile stainless steel, which is widely used to make equipment and parts that require good overall performance (corrosion resistance and formability). In order to maintain the inherent corrosion resistance of stainless steel, steel must contain more than 18% chromium and more than 8% nickel. 304 stainless steel is a grade of stainless steel produced in accordance with the American ASTM standard.