How to identify the quality of stainless steel material, how to distinguish the quality of stainless

The magnet is used to adsorb the stainless steel plate to verify its advantages and disadvantages. 304L stainless steel plate does not absorb and is non-magnetic, and is considered to be good, on the contrary, it is considered to be a fake. In fact, this is an unrealistic way to discern it.

There are many types of stainless steel, which can be divided into austenite type and martensitic or ferrite type according to the structure at room temperature. The 310S stainless steel plate austenitic type is non-magnetic or weakly magnetic, and the martensitic or ferritic type is magnetic. However, this is not necessarily the case.

For example, the austenitic 304 stainless steel plate material that is usually used for decoration tube sheet is generally non-magnetic, but magnetic may also occur due to the fluctuation of chemical composition caused by smelting or different processing states, which cannot be regarded as counterfeit or unqualified. Stainless steel pipe** In addition, 304 stainless steel is cold-worked, and the microstructure will also be converted to martensitis, the greater the cold-working deformation, the more martensitic conversion, and the greater the magnetism 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.

How to choose stainless steel; Uses of high-quality stainless steel plates.

1. Before selecting the stainless steel plate, it is necessary to consider the use of the stainless steel plate and the use environment. For example, welded pipes are generally used for decoration, seamless pipes are generally used for fluid transportation, sanitary stainless steel plates are used for medical treatment or kitchens, and thick-walled pipes are used for pressure; Generally indoors.

200 series materials can be used, 304 and other materials need to be used outdoors, and 316 or more materials are generally used in acidic and alkaline places or coastal areas.

Second, when selecting steel pipes, it is necessary to make sure that the material meets the standards. Take the 304 material as an example:

1.From the analysis of **, if the 304 material stainless steel plate is even lower than the general ** of 301 material on the market, it is necessary to carefully distinguish that it is likely to be passed off from other materials;

2.Identify whether the word "304" is stamped on the pipe surface, and ask for the manufacturer's quality certificate as a certificate; 3.It can be tested with acidic reagents, and after 30 seconds, material 304 will not change color, and 201 will turn black;

4.Samples can be taken for large-scale purchase and sent to the national authoritative testing center for component testing.

3. Whether the color of the outer surface and the inner wall of the pipe is bright and smooth, and whether the thickness is uniform or rough. Generally, welded pipes do not need to be inspected, while seamless steel pipes are produced by cold-drawn or hot-rolled methods, and improper operation in the production process is easy to produce thickness.

The degree is uneven, there are cracks on the pipe surface, and the surface roughness is generally the seamless pipe is not polished, if there is no special requirement for the appearance, it will not affect the use. Fourth, the purchase should choose the excellent products assessed by the Quality and Technical Supervision Bureau. Testimonials and good reputation among customers are the most direct and effective ways to buy.

Fifth, there are often internal heavy skins, pittings, and rolled blue lines in the rolled pipe, which can not be avoided under normal circumstances, and basically do not affect the use, but must choose as little as possible when purchasing, especially to check the inner surface. Sixth, be sure to choose a big brand of stainless steel, such as Wuhan Tianshun. We can process the right product for your needs.

1.Generally speaking, the corrosion resistance of stainless steel is related to the nickel content, and the higher the nickel content, the better the corrosion resistance (but not absolutely). Most of the stainless steel used in food contact with food in food factories is 304, with a nickel content of more than 8%, and 316L (containing more than 12% nickel, a medical scalpel) will be used for individual utensils with high requirements.

2.With or without magnetism, it does not fully prove the nickel of stainless steel and its grade. Magnetism is related to the processing of steel during smelting (the arrangement of molecules changes due to different processes such as annealing or quenching after hot melting).

How to distinguish the good from the bad of stainless steel? Try to suck it with a magnet, what you suck is iron, and if you don't suck it, it is stainless steel, look at its brightness, look at its hardness.

1. Identification of color.

After pickling stainless steel, the surface color is silver and white: chromium-nickel stainless steel is silver and jade; Chromium stainless steel, white slightly gray, weak luster; The color of chromium-manganese-nitrogen stainless steel is similar to chromium-nickel stainless steel and slightly lighter. Surface color of stainless steel without pickling:

Chromium-nickel steel is brownish-white, chrome steel is brownish-black, and chromium-manganese nitrogen is black (these three colors refer to the more oxidized color). Cold-rolled non-annealed chromium-nickel stainless steel with a silvery-white and reflective surface.

2. Identification with magnet.

Magnets can basically distinguish between two types of stainless steel. Because chromium stainless steel can be attracted to magnets in any state; Chromium-nickel stainless steel is generally non-magnetic in the annealed state, and some will be magnetic after cold working. But high-manganese steels with higher manganese content are non-magnetic; The magnetic situation of Inconel stainless steel is more complicated:

Some are non-magnetic, some are magnetic, and some are non-magnetic in the longitudinal plane and magnetic in the transverse plane. Therefore, although the magnet can basically distinguish between chromium stainless steel and chromium-nickel stainless steel, it can not correctly distinguish some special properties of steel, let alone distinguish specific steel grades.

3. Identification with copper sulfate.

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

To distinguish the advantages and disadvantages of stainless steel, as long as the stainless steel solder joint pickling solution (also called washing steel) is coated on the surface of the steel pipe, if the pipe surface does not change color, it is not easy to rust; On the contrary, if it turns black faster, the worse the quality, and it is easy to turn black and rust. Stainless steel is generally divided according to the organizational structure, which can be divided into several categories such as austenite, ferrite, and martensitic. Stainless steel has the characteristics of stainless steel, acid resistance, high temperature resistance, wear resistance and austenitic general non-magnetism.

The corrosion resistance of stainless steel is mainly determined by the content of chromium and nickel, and the higher the content, the less likely it is to rust.

It won't be poisoned.

The 400 series is a ferrite series. Commonly known as stainless iron. It has strong magnetic conductivity and is suitable for making a double-bottom outer layer for induction cooker.

But the corrosion resistance is not enough. It is not possible to make a pot body. The lid of the pot is ok.

Only 304 steel can be used for the pot body. Now the 400 series is used for low-end products.

201 stainless steel has certain acid and alkali resistance, high density, polishing without bubbles, no pinholes, etc., and is a high-quality material for the production of various cases and strap covers. It is mainly used for decorative pipes, industrial pipes, and some shallow drawing products.

200 series stainless steel, such as 201, turns reddish-brown after 30 seconds with the test agent. It indicates that a large number of manganese ions have been precipitated, 301 has turned light brown, and a small amount of manganese ions have been precipitated. Long-term use is harmful to the human body.

430 stainless steel

430 stainless steel is a general steel grade with good corrosion resistance, better thermal conductivity than austenite, smaller thermal expansion coefficient than austenite, heat fatigue resistance, addition of stabilized element titanium, and good mechanical properties of weld parts. 430 stainless steel is used for building decoration, fuel burner parts, household appliances, and home appliance parts.

430F is a steel grade with easy machinability added to 430 steel, which is mainly used for automatic lathes, bolts and nuts, etc. 430LX is mainly used in hot water tanks, hot water supply systems, sanitary appliances, household durable appliances, bicycle flywheels, etc., by adding Ti or NB to 430 steel and reducing C content, which improves processability and weldability.

It is also known as 18 0 or 18-0 due to its chromium content. Compared to 18 8 and 18 10, it contains slightly less chromium and has a corresponding reduction in hardness.

Stainless steel should not be caught by magnets. If the stainless steel can be absorbed by the magnet, it means that it contains high iron and nickel elements, and the quality of this stainless steel is very poor, the corrosion resistance is not good, and it is easy to rust. The stainless steel in stainless steel is mainly due to chromium, but the addition of manganese to stainless steel also prevents it from being adsorbed by magnets.

How to choose a good stainless steel product1. Look at the classification of stainless steel. Stainless steel can be divided into ferrite, austenitic, martensitic and other kinds according to different chromium-nickel content, consumers need to choose according to actual needs, than the fiber such as martensitic, because of poor weldability, so can not be used to make anti-theft windows.

2. Look at the quality of the process. When purchasing stainless steel, first look at whether the construction process of the surface is intact, whether the surface paint plating is uniform and smooth, if it is welded, it is necessary to focus on the welding point process to ensure that there is no imitation leakage welding, unwelded and so on.

Professionals can see the spark at the time of cutting. You can find the testing department and use spectroscopy instruments for testing. Use stainless steel material to identify water, also known as stainless steel potion.

Stainless steel whole materials, which are generally ordered by steel mills or imported from abroad and processed commodities with overstocked social reserves. The method of identification of stainless steel is also different.