2.20 1 consists of 17cr-4.5ni-6mn-n, which is a nickel-saving steel and a substitute for 30 1 steel. Magnetic after cold working, used for railway vehicles.
The composition of 3.304 is 18cr-9ni, which is the most widely used stainless steel and heat-resistant steel. Used in food production equipment, Xitong chemical equipment, nuclear energy, etc.
4.20 1 Mn has high content, bright surface and dark brightness. High manganese content is easy to rust. 34 contains more chromium, the surface is dull and does not rust. These two kinds are compared together. The most important thing is that the corrosion resistance of 20 1 is very poor, so the price is much cheaper. Moreover, the corrosion resistance of 20 1 is not as good as that of 304 because of its low nickel content and low price.
The difference between 5.20 1 and 304 is the problem of nickel. And now the price of 304 is relatively expensive, generally close to 30 thousand tons, but if it is 304, at least you can use liquid medicine to do experiments)
6. Stainless steel is not easy to rust, because chromium-rich oxide formed on the steel surface can protect the steel body. Material 20 1 belongs to high manganese stainless steel, which has higher hardness, higher carbon content and lower nickel content than material 304.
7. Different compositions (mainly from carbon, manganese, nickel and chromium, 20 1 and 304 stainless steel are different)
C-Si-Mn-P-S-Cr-Ni-Mo-Cu
Aisi (304)
≤0.08
≤ 1.00
≤2.00
≤0.045
≤0.03
18-20
8- 10
Aisi (20 1)
≤0. 15
≤ 1.00
5.5-7.5
≤0.05
≤0.03
16- 18
3.5-5.5
attract
People often think that magnets adsorb stainless steel materials and verify their advantages and disadvantages, which are considered as good goods and genuine products. If it is magnetic, it is considered a fake. In fact, this is an extremely one-sided and unrealistic way of mistaken identification.
There are many kinds of stainless steel, which can be divided into several categories according to the structure at room temperature:
1. Austenite types: such as 304, 32 1, 3 16, 3 10, etc.
2. Martensite or ferrite type: such as 430, 420, 4 10, etc. ;
Austenite is nonmagnetic or weakly magnetic, while martensite or ferrite is magnetic.
Stainless steel usually used as decorative tube sheet is mostly austenitic 304 material, which is generally non-magnetic or weakly magnetized. However, due to the fluctuation of chemical composition or different processing conditions caused by smelting, magnetism may also occur, but this cannot be considered as forgery or unqualified. What is the reason?
As mentioned above, austenite is nonmagnetic or weakly magnetic, while martensite or ferrite is magnetic. Due to composition segregation or improper heat treatment during smelting, a small amount of martensite or ferrite will be produced in austenitic 304 stainless steel. In this way, 304 stainless steel will have weak magnetism.
In addition, the microstructure of 304 stainless steel will also transform into martensite after cold working. The greater the cold deformation, the more martensitic transformation and the stronger the magnetism of steel. Like a batch of steel belts, φ76 tubes and φ9.5 tubes are produced, and there is no obvious magnetic induction. Due to the large cold bending deformation, the magnetic induction is more obvious, and the rectangular tube on the production side is more deformed and stronger than the circular tube, and the magnetic effect is more obvious, especially at the corner.
In order to completely eliminate the magnetism of 304 steel caused by the above reasons, stable austenite structure can be restored by high temperature solution treatment, thus eliminating magnetism.
In particular, the magnetism of 304 stainless steel caused by the above reasons is completely different from that of 430, carbon steel and other stainless steels, which means that the magnetism of 304 steel is always very weak.