What method is used to distinguish the authenticity of stainless steel?

People often think that "stainless steel" means "stainless steel". If it rusts, it must be a fake and shoddy product. This understanding is of course too simple. First of all, the "stainless" of stainless steel is not absolutely rustless, but relatively rustless under certain conditions. If the user uses it improperly, it will naturally rust if it is used in an environment or condition beyond its corrosion resistance. Second, the stainless steel material used in the product is corroded and rusted, or it may be because the manufacturer's material selection is unreasonable, that is, the manufacturer chooses an inappropriate stainless steel brand as the raw material for its product use, or the manufacturer's production and processing technology is not up to standard. In addition, that is, the manufacturer did choose fake stainless steel that did not meet the authoritative standards of relevant countries or industries as raw materials. In any case, these are what manufacturers should face and solve when purchasing and processing. In view of the fact that there are still cases of producing and selling inferior stainless steel in the current market, as well as market cheating behaviors such as shoddy and forging quality certificates, how can we take the initiative in purchasing stainless steel materials and quickly see through these cheating behaviors to avoid the harm of fake and inferior stainless steel? For these stainless steels, which may be equally bright, it is difficult to distinguish their true and false advantages and disadvantages from their appearance, even as experts. Is there any simple and easy way? Some people say: this is very simple, use a magnet to suck! What you can't absorb is good, it's "stainless steel", and what you can absorb is poor, it's "stainless iron"! At present, this statement and practice seems to be very popular, and even scientific and technological publications and TV programs have implemented this law. It is unscientific and extremely wrong for industry experts to deny this statement and practice. At present, among the five types of stainless steels that have been developed and applied in the world, only austenitic stainless steels (numerous 3 series brands and 2 series brands) often have no magnetism (or have weak magnetism after processing), while ferritic stainless steels (numerous 4 series brands), duplex stainless steels, martensitic stainless steels and precipitation hardening stainless steels all have magnetism. No matter whether it is magnetic or not, each stainless steel has its own characteristics and scope of application. 3 series austenitic stainless steel is the most widely used, and the proportion of stainless steel with magnetic modern ferrite is increasing, which can partially replace 3 series austenitic stainless steel in civil and industrial fields such as kitchen utensils, household appliances, decoration, automobile exhaust system and petrochemical industry. For 2-series austenitic stainless steel whose magnet can't be sucked, replacing nickel with manganese and nitrogen reduces the cost and improves the strength compared with the corresponding 3-series steel. However, due to the decrease of its corrosion resistance, its application fields are narrow, often those fields that require high strength, non-magnetism and low corrosion resistance, such as springs and electronic equipment. As for the so-called "2 series stainless steel" prevailing in China market, its corrosion resistance and use value are even lower. These products are not produced according to the existing national standards, but according to their very lax enterprise standards, the contents of nickel and chromium in steel are reduced, and the contents of manganese are increased. Some of them even have nickel below 1%, chromium below 1% and manganese above 14%, and their pitting equivalent is extremely low, which is far from the corresponding national standards. In terms of corrosion resistance, these products can not even be called stainless steel, nor can they be called 2 series stainless steel at all. In the current stainless steel market in China, it can be said that there is almost no real 2-series stainless steel. The so-called "2-series stainless steel" in the market is the biggest problem steel and fake steel at present, but it is exactly non-magnetic austenitic steel like 3-series austenitic stainless steel! It can be said that in the current China market, the use of magnet attraction to identify the quality of stainless steel tends to connive at fake and inferior stainless steel, and crowd out high-quality magnetic ferritic steel, and at the same time crowd out nonmagnetic 3-series austenitic stainless steel due to cost factors, and may even make this fake and inferior steel pass off as nonmagnetic 3-series austenitic stainless steel and be used in industry. It is obviously impossible to identify the authenticity of stainless steel by magnetic attraction. Is there any other practical and simple method? The answer is yes. Here, a simple method is introduced, that is, identification with stainless steel measuring solution, which is to determine or distinguish some situations of the measured steel by observing the color change characteristics produced by the measuring solution in the process of dissolving the measured steel. The "color change" is often related to specific elements such as nickel (Ni), molybdenum (Mo) and manganese (Mn) in the tested steel. At present, there are many stainless steel measuring liquid products on the market in China, some of which are imported from Japan and many of which are made in China. Especially in the areas where the stainless steel industry and stainless steel scrap recycling industry are relatively developed in China, such as Dai Nan, Wuxi, Foshan, Guangdong, Ningbo, Zhejiang, etc., some manufacturers specializing in the development of stainless steel measuring liquid have appeared, while some enterprises engaged in chemical technology and chemical reagents have also developed stainless steel measuring liquid for the needs of the stainless steel industry. At present, although there are many brands of stainless steel measuring liquid in China, the products seem to be the same, which can be basically divided into two categories: those without batteries and those with batteries. The ones that don't need batteries are often not subdivided, mainly by observing and measuring the color changes of the droplets on the stainless steel surface, and then distinguishing them by chromatography. For example, there is a model 34 in the market, which is marked with four standard colors corresponding to four stainless steel brands-21, 22, 31 and 34, of which 21 corresponds to deep red, 22 to red, 31 to light red and 34 to colorless or light yellow. These colors refer to the colors that appear when the corresponding steel grades are tested with this measuring solution. There are many kinds of measuring solutions for batteries in the market, such as "Mo2, low Ni, Ni2, Ni4, Ni6, Ni8, Ni14, Ni2, Ni4, Ni6", and some products use "n" instead of "Ni". When these products are used alone or in combination, the approximate content (percentage) of corresponding elements such as nickel (Ni), molybdenum (Mo) and manganese (Mn) in steel can be determined, and then the quality of steel can be distinguished according to the relevant authoritative national standards. For example, when using the "Ni8" measuring solution, first drop a proper amount of "Ni8" medicine solution on a clean steel surface, then connect the positive electrode of a special battery (usually 9V, which can be distributed by the manufacturer) with a steel plate, and connect the negative electrode with "Ni8" medicine beads on the steel surface (be careful not to touch the steel surface). After a few seconds, stop the power supply to observe the color change of the medicine beads on the steel surface. If the color turns red, Another example is the "low Ni" solution, which is a powerful weapon for the determination of low Ni and high Mn stainless steel. If the beads are purplish red after electrified oxidation, it indicates that the manganese content in steel is above 6% and the nickel content is generally below 5.5%. If electrified oxidation is colorless or light yellow, it is generally other materials such as 31, 34 and 43. Another example is "Mo2" measuring solution. If the red complex generated by electrified oxidation does not fade, it indicates that the molybdenum content in steel is about 2% or above ... The usage of each product will be introduced in detail in its instruction manual. Using stainless steel measuring liquid, we can easily see through some cheating behaviors in the market and the true face of fake and inferior stainless steel to a certain extent. For example, if we want to buy 34 brand stainless steel, we can test the "34" products provided by the manufacturers. If it is a true 34, we should test it with the above-mentioned "Type 34" measuring solution or "Ni8" measuring solution, and the corresponding test results should appear; otherwise, it is not a true 34; If the beads are found to be purplish red by further testing with "low Ni" measuring solution, it indicates that the product is a kind of steel with high manganese content, and it is also likely to be a fake stainless steel with low corrosion resistance prevailing in the market at present, that is, the so-called "2 series stainless steel". When using the measuring liquid to measure the approximate content of specific elements in stainless steel for relevant testing and identification, we are required to refer to and understand the provisions on chemical composition in the relevant national standards for stainless steel. At present, the use of stainless steel determination liquid to identify stainless steel only answers the question of "what is not" to a certain extent, but can not really answer the question of "what is exactly". For example, if the so-called "34" product is tested with "34" measuring solution or "Ni8" measuring solution, if the test result is the same as that of the real 34 product, we can never conclude that it is 34, but can only say that it is "possible". Because whether it is electrified or not, the test result is only a necessary but not a sufficient condition for us to judge that the tested steel is a certain steel type (such as 34). If we really want to find out the exact brand of Chugang, we must comprehensively determine its chemical composition through professional chemical analysis or spectral analysis, and then identify it against relevant authoritative standards. Of course, these methods are more professional and accurate than using stainless steel determination solution, but they are also much more difficult or costly. In addition, the quality of stainless steel is not only determined by its chemical composition, but also related to its structure, properties, purity and other factors. For the determination of these factors, the stainless steel measuring liquid is obviously powerless, only with the help of relevant professional tests. At present, the products of stainless steel measuring liquid on the market are not scientific enough in identification and other aspects. As mentioned above, when "N" is used instead of "Ni", some 2 series stainless steels are divided into "2, 21, 22" and so on. In the actual use process, it is also found that some test results are difficult to distinguish with naked eyes, which is easy to lead to errors. For example, except for obvious color differences between 21 and 22 and 31 and 34, the color changes between 21 and 22 and between 31 and 34 are not obvious. These unscientific and insufficient places need further improvement by the relevant manufacturers. In any case, when purchasing stainless steel products, we should not only pay attention to the factory inspection certificate or quality certificate of the products, but also pay attention to the reputation of the merchants, instead of being greedy for cheap. Besides, we can still take some initiatives to see through the market deception and the true face of fake and inferior stainless steel products. At present, the small bottles of stainless steel measuring liquid on the market are small in size, light in weight, convenient to carry, low in cost (the price of each bottle ranges from ten yuan to twenty or thirty yuan, and the cost of each test is only a few cents), and the test operation is very simple, so it can be regarded as a powerful tool and "weapon". We might as well try it.