How to tell if it is stainless steel and how to identify whether it is stainless steel?

Iron and steel are distinguished by the amount of carbon they contain. Iron-carbon alloys with a carbon content of less than 2% are called steel, and those with a carbon content of more than 2% are called iron. Steel is widely used because of its toughness, elasticity and rigidity.

All we come into contact with in our lives is steel, but people call it differently. For stainless steel, regardless of whether the magnet can be attracted or not, as long as it meets the quality standards, it is stainless steel. Therefore, from the point of view of metallurgy, there is no such thing as stainless iron at all.

The main element of stainless steel that resists corrosion is chromium. Steel with a chromium content above will not rust. The alloying elements added during smelting are different, and there is a difference between magnets that can be attracted and those that cannot be absorbed.

Stainless steel is generally divided according to the organizational structure, which can be divided into several categories such as austenite, ferrite, and martensitic. If different proportions of chromium and nickel are added to the molten steel, the smelted austenitic steel is stainless steel that cannot be attracted by magnets; If chromium and a small amount of nickel (or no nickel) are added to the molten steel, the steel is ferritic stainless steel that can be attracted by magnets; The main alloying elements of martensitic stainless steels are chromium, iron, and carbon. There are more than 100 kinds of stainless steel due to different alloy content.

In addition to austenitic, stainless steels are magnetic.

Nickel is very small in the world and is relatively expensive. Therefore, stainless steel with high nickel content is also higher in the market, and the magnet is not yet able to attract it. In fact, there is another kind of stainless steel magnet that cannot be sucked.

That is, stainless steel with high manganese content, low nickel content or no nickel. This stainless steel market is more than 1,000 yuan per ton lower than stainless steel with high nickel content. Some dealers just take advantage of people's misunderstanding that "good stainless steel magnets can't be sucked" to deceive consumers, ** as expensive as high nickel stainless steel.

There are more than 100 types of stainless steel, and the characteristics and functions are also different. Generally, austenitic stainless steel is used for decoration, landscape and sculpture. Because austenitic stainless steel has low thermal conductivity, it is not suitable to use it as kettles, woks, and rice pots, which will waste energy and prolong the time of boiling water for cooking.

Using ferritic stainless steel to make woks and rice pans not only has excellent corrosion resistance, but also its thermal conductivity is nearly half higher than that of austenitic stainless steel. Washing machine barrels, water heaters, vegetable basins, etc., as long as the utensils in contact with water should be made of ferritic stainless steel. Some people complain that stainless steel knives are not fast, and this is because the wrong stainless steel is chosen.

Austenitic stainless steel cannot be hardened and is not suitable for knives and cutting tools. Tools made of martensitic stainless steel can change the hardness of stainless steel by heat treatment, such as quenching and tempering.

The easiest way is to visually inspect and take a magnet at the same time, if it can be adsorbed, it is not stainless steel. Of course, it is best to take a small piece into some appraisal agency for testing and identification.

To identify the quality of stainless steel, we can not only look at the surface, but also check whether there is "material" inside, and buy a bottle of "stainless steel test solution" for more than 10 yuan to buy "stainless steel test solution", also known as "stainless steel test solution", "manganese test box", "manganese test solution", etc.

Test method: clean the stainless steel surface to ensure that there are no stains; After grinding off the surface coating, a drop of the measurement solution is used to remove the coating, and the best choice for the coating is to choose the edge with a cut to observe the color change of the stainless steel in the test area; Compare the color of the stainless steel or the time it takes to turn red, and roughly determine the grade of the stainless steel.

There are many types of stainless steel, such as. The biggest difference between these materials is rigidity, hardness, and corrosion resistance, 316 has the best corrosion resistance, 201 is the worst, and 316 is the highest in each grade of stainless steel. Stainless steel with poor quality will change color on the surface after a long time, and it is easy to be covered with oil and water, stains, etc., and it is not easy to clean, rust, and bacteria.

False 201 stainless steel: It will turn red in about 5 seconds, and after 10 seconds, the red will be the same as on the color card.

201 Stainless Steel (Authentic 201): It turns red in about 50 seconds, and its red color will be the same as on the color card.

202 stainless steel: turns red in about 1 minute.

301 stainless steel: It turns red in about 3 minutes, and the color is very light, so you should look carefully.

304 Stainless Steel: No change for 3 minutes, may be darker in color, but not red.

316 stainless steel: no color change can be seen for about 10 minutes.

People often use magnets to adsorb stainless steel to verify its advantages and disadvantages. 304 stainless steel plate does not absorb and is non-magnetic, which is considered good, and on the contrary, it is considered to be a counterfeit. In fact, this is an unrealistic way to discern it.

There are many types of stainless steel, which can be divided into several categories according to the organizational structure at room temperature:

1 Austenite type: such as etc.;

2 Martensite or ferrite type: such as etc.;

The austenite type is amagnetic or weakly magnetic, and the martensitic or ferrite is magnetic.

Most of the stainless steel commonly used as decorative tube sheets is austenitic 304 material, which is generally non-magnetic or weakly magnetic, but magnetic may also occur due to fluctuations in chemical composition or different processing states caused by smelting, but this cannot be regarded as counterfeit or unqualified, what is the reason for this? As mentioned above, austenite is non-magnetic or weakly magnetic, while martensitic or ferrite is magnetic, due to improper segregation or heat treatment during smelting, it will cause a small amount of martensitic or ferrite structure in austenite 304 stainless steel. In this way, there will be a weak magnetic property in 304 stainless steel.

In addition, after cold working, the microstructure of 304 stainless steel will also be transformed to martensitic, and the greater the deformation degree of cold working, the more martensitic transformation, and the greater the magnetic property of the steel. Like a batch of steel strips, 76 tubes are produced, and there is no obvious magnetic inductance, and tubes are produced. Due to the large deformation of the bend, the magnetic induction is more obvious, and the production of rectangular pipes is larger than that of round pipes, and the extraordinary is the corner part, the deformation is more intense, and the magnetic is more obvious.

In order to completely eliminate the magnetism of 304 steel caused by the above reasons, the austenite structure can be stabilized by high-temperature solution treatment, so as to eliminate the magnetism. Extraordinary should be mentioned that the magnetism of 304 stainless steel caused by the above reasons is not at the same level as that of stainless steel of other materials, such as 430 and carbon steel, that is to say, the magnetism of 304 steel always shows weak magnetism.

This tells us that if the stainless steel strip is weakly magnetic or not magnetic at all, it should be judged to be 304 or 316 material; If it is the same as the magnetism of carbon steel, it shows strong magnetism, because it is not judged to be 304 material. In addition, 304 stainless steel is cold-worked, and the microstructure will also be converted to martensitis, and the greater the cold-working deformation, the more martensitic transformation, and the greater the magnetic property of the steel. On the other hand, the inferior quality of the 200 series stainless steel is likely to be non-magnetic, so it would be a mistake to judge that it is genuine.

Sometimes, we see that when customers buy stainless steel screws, they will bring a magnet to experiment with the magnetic size of stainless steel, in fact, this practice is unscientific. In fact, stainless steel is non-magnetic in the normal state, slightly magnetic after cold work processing, and it is possible to be completely non-magnetic only in the vacuum state.

Commonly used materials: 304m slightly magnetic after cold working (left and right); 304HC magnetic (left and right); The magnetic properties of 316 material are less than those after cold working. Each material has good ductility, easy cold working molding, tensile strength, yield strength, can meet the requirements.

As long as you choose the right product according to the actual use requirements, I believe it will meet your needs.

Not very accurate. However, it can be roughly distinguished, and some other conditions can be added to make a judgment;

Most of the commercially available stainless steel identification solutions are based on the time of discolorationEstimatedThe proportion of nickel (or chromium) in stainless steel, but the steel index that meets the requirements of the grade is not only the nickel (or chromium) content.

For example, the difference between 304 and 304L and 304H is the carbon content, and it is not possible to distinguish between the two grades by identifying the nickel or chromium content alone.

Therefore, the identification of stainless steel by identification fluid is usually only reliable when distinguishing between known grades of stainless steel (e.g., distinguishing between 201 and 304), and other times can only be judged approximately, or with some other conditions (e.g., the number of sparks generated by L and 304H on the grinding wheel or cutting machine is significantly different).

We often use stainless steel products in our lives, especially 304 stainless steel materials are deeply loved by the majority of consumers, so how to identify stainless steel? Let me take you to understand it, I hope it will be helpful to you.

1. Grinding identification: put the stainless steel on the grinder to see how the spark is. If the sparks appear to be streamlined and the sparks are dense, it proves that it is a high-manganese steel or manganese-nitrogen steel with high manganese content; If there is no knotted flower, it is certified as stainless steel.

2. Identification by annealing method: Generally, the cold-worked chromium-nickel stainless steel itself will be magnetic, which can be burned in the fire with small pieces, and then let it cool when the whole is red, under normal circumstances, the magnetism will disappear after annealing. However, some chromium-nickel stainless steels, due to the addition of iron, are still magnetic even in the hot state.

3. Chemical qualitative identification: dissolve a small piece of stainless steel in aqua regia, add ammonia to neutralize, and gently inject nickel reagent. If a red velvety substance appears on the liquid surface, it proves that the stainless steel contains nickel; If there is no red substance, it means that there is no nickel.

Identification is real stainless steel, stainless steel reagent can be used to detect the nickel content of steel to distinguish which series of stainless steel, for the on-site rapid detection of stainless steel materials, stainless steel waste sorting, reuse, has an irreplaceable role.

In addition, magnetism can be used to judge whether stainless steel is real, because stainless steel is weakly magnetic, so when using a magnet to absorb stainless steel, it will show that the magnetism is not strong, so to distinguish whether stainless steel is true or false.