What are the ways to identify the authenticity of stainless steel pipes?

1. Magnetic test Magnetic test is the easiest way to distinguish annealed austenitic stainless steel from ferritic stainless steel. Austenitic stainless steel is a non-magnetic steel, but it will have a slight magnetic property after being cold worked under high pressure; Whereas, pure chromium steel and low-alloy steel are both highly magnetic steels.

2. Nitric acid point test A significant feature of stainless steel pipes is that they have inherent corrosion resistance to concentrated nitric acid and dilute nitric acid. This property makes it easy to distinguish from most other metals or alloys. However, high-carbon 420 and 440 steels are slightly corroded during the nitric acid point test, and non-ferrous metals will be corroded immediately when they encounter concentrated nitric acid.

Whereas, dilute nitric acid is strongly corrosive to carbon steel.

3. Copper sulfate point test The copper sulfate point test is the easiest way to quickly distinguish ordinary carbon steel from all types of stainless steel. The concentration of the copper sulfate solution used is 5 10%. Before the point test, the test area should be completely removed from grease or various impurities, and a small area should be polished with a soft cloth, and then the copper sulfate solution should be dripped into the cleaned area with a drop bottle.

Ordinary carbon steel or iron forms a layer of surface metallic copper in a matter of seconds, while the surface of stainless steel does not produce copper precipitation or show the color of copper.

4. Sulfuric acid test The sulfuric acid immersion stainless steel pipe test can distinguish 302 and 304 from 316 and 317. The cut edges of the specimen should be finely ground and then cleaned and passivated for half an hour with nitric acid at a volume concentration of 20 30% and a temperature of 60 66. The volume concentration of the sulfuric acid test solution is 10% and heated to 71 o'clock.

When 302 and 304 steels are immersed in this hot solution, they are rapidly corroded and produce a large number of bubbles, and the specimen turns black in a few minutes; Specimens of 316 and 317 steels, on the other hand, are not corroded or react very slowly (do not produce bubbles), and the specimens do not change color within 10 to 15 minutes. Approximate comparisons can be made by testing specimens with known compositions at the same time, which can be made more accurate.

1. The appearance quality, rust-free, high surface finish, and defect-free stainless steel are made by large factories with better performance.

2. Chemical composition, generally speaking, stainless steel with high nickel content and low carbon content has better corrosion resistance, but it is also relatively high.

3. To put it simply, the corrosion resistance of stainless steel (austenitic) is better than that of stainless steel (ferritic) with magnetism.

Look at the surface for defects, such as cracks and finish.

Then look at whether the nickel content of the sign is high or not.

The simple distinction of 316 stainless steel is also the most basic and the most convenient is to use a magnet to distinguish, and another is to use a drop test with medicinal solution.

To judge more accurately, you need to play the spectrum, which is more professional. Therefore, it is very important to identify the manufacturer in the purchase of stainless steel materials.

At present, the international corrosion resistance of materials is divided into three categories according to the annual corrosion rate, the first type is complete corrosion resistance, and its corrosion rate is less than the year, and high-quality stainless steel belongs to this type of material; The second type is corrosion resistance, and its corrosion rate is years, which belongs to general stainless steel; The third category is non-corrosion resistant, and its corrosion rate is greater than per year. The stainless steel products found that the corrosion rate was as high as several years, which was seriously insolvent. After further analysis of the composition of the product, it was found that the chromium content, which represents an important indicator of stainless steel, was only and below, which was lower than the minimum chromium requirement for stainless steel.

Taking advantage of the loopholes of the people's lack of understanding of stainless steel, the fraud was carried out.

There are special tests for 304 stainless steel and 316 stainless steel potions on the market, if you want to judge whether your stainless steel is made of 316 material, you can buy 316 stainless steel potions to test.

Now the most commonly used two stainless steels 304,316 (or corresponding to the German and European standards,,The main difference between 316 and 304 in terms of chemical composition is that 316 contains MO,And it is generally recognized that 316 has better corrosion resistance,More corrosion resistance than 304 in high temperature environments。 Therefore, in a high-temperature environment, engineers generally choose parts made of 316 material.

2. Spectrometer detection.

The stainless steel detection spectrometer can detect the elemental content of stainless steel wires; As long as you test it, you can know whether it is 316 stainless steel wire.

There is a liquid test, ** purchase.

Hello, glad to answer for you.

1.When the steel is 304 stainless steel, the 304 corresponding test solution is used for testing, and if it is true, the corresponding test result will appear. This is a nose-specific test method that can be distinguished between different grades of steel.

2.The use of copper sulfate solution, drip solution on the product, if there is no change, it belongs to **, otherwise it is inferior.

The above is to introduce you to the two methods of identifying the authenticity of stainless steel, the testing process is both scientific and accurate, and you can quickly make a judgment.

Stainless steel pipes play an extremely important role in our daily life, but we are still a little unfamiliar with this "familiar friend", what elements do they have?

Hardness, toughness, corrosiveness, the proportion of different elements determines the performance difference of stainless steel pipes, and a variety of steel pipes with different hardness and corrosion resistance will be formed.

1.Carbon: It can be said that carbon is an indispensable raw material in pipes, as important as human blood. High carbon means strong resistance, sufficient stiffness, and not easy to deform; Of course, the corrosion performance is reduced on the contrary.

2.Manganese: It can improve high temperature resistance and wear resistance, and high-strength alloy steel contains a large amount of manganese, which increases its strength.

3.Nickel: Ensures the stability of stainless steel, but because nickel is scarce, other elements should be used instead.

4.Aluminum: Refine the crystal structure of steel, improve material toughness, oxidation resistance, and durability.

5.Phosphorus: This is different from the above elements, phosphorus is harmful to stainless steel pipes, making their performance worse and inferior, so the industry requires that the phosphorus content should be less than.

The stainless steel pipe manufacturers with real standards and thickness are directly hitting the stainless steel pipe specifications, thickness, materials, brands and other information on the pipe body.

The most intuitive thing is to ask the other party to provide a quality inspection report.

There is also the use of potion testing.

Magnetic identification. A long time ago, we had the concept of using magnets to judge the authenticity of stainless steel, although this is inaccurate, but there is a certain basis. 304 stainless steel is austenitic stainless steel, which is non-magnetic, but after various processing, it will have weak magnetism, so 304 stainless steel pipe is not magnetic or has weak magnetism.

Therefore, if you use a magnet to get close to ordinary stainless steel and 304 materials, you can clearly feel the difference in magnetic force between the two.

Potion identification. Austenite is non-magnetic, so there will be used to pass off 304 tubes, so if it is magnetic judgment is also inaccurate, there is a medicine can quickly identify the 304 material, the liquid of this agent drops a little on the stainless steel products to be tested, according to the color change can easily identify which stainless steel.

Stamped logo. Basically, many regular manufacturers of 304 stainless steel products will have the corresponding steel seal logo, which is the most direct identification method. All the stainless steel pipes produced by Xiyouwo stainless steel are stamped, I hope it will help you!

1. Reagent identification method.

Use a bottle of potion, put 2 drops on stainless steel, and after two minutes, the color of the potion turns red is not 304 stainless steel. On the contrary, the color does not turn red is 304 stainless steel. Isn't it very convenient and very simple.

304 stainless steel.

Second, the use of the dialectic.

It is generally possible to distinguish 304 stainless steel by looking at the material and use of stainless steel. The faucets, toiletries, and kitchen utensils are basically made of 304 stainless steel. On the contrary, the stainless steel used for handrails, guardrails, doors and windows is not 304 stainless steel.

304 stainless steel.

3. Hardness discrimination.

Find a hard wire, draw a line on the surface of stainless steel, if the scratch is not obvious, it means that the stainless steel is very hard, it is not 304 stainless steel. On the contrary, it is made of 304 stainless steel.

Fourth, magnet discrimination.

It is to use a magnet to absorb on the surface of stainless steel, if it is magnetic, it is not 304 stainless steel, on the contrary, if the magnetism is weak, it is 304 stainless steel.

1. Spectroscopy with a high-voltage electric excitation spectroscopy gun (the instrument is small in size and easy to carry) can qualitatively distinguish the types of elements of steel, and the approximate content of the content.

Second, color. The surface color of pickled stainless steel: 300 series stainless steel is silvery-white and jade-colored; 400 series stainless steel is white and slightly orange gray, and the luster is weak; The color of 200 series stainless steel is similar to that of 300 series stainless steel, but slightly lighter.

Surface color of unpickled stainless steel: 300 series stainless steel is brownish-white; 400 series stainless steel is brownish-black; 200 series stainless steel is black.

3. Chemical reagents.

There is a special reagent called nickel qualitative solution, which is dropped on the surface of stainless steel, and oxidized instantly after being energized to produce light white or light yellow, indicating that the stainless steel does not contain nickel; It produces a pale rose red color and immediately fades into a dark yellow, indicating that the nickel content of the stainless steel is about 1%-2%; The rose red color is produced and does not fade, indicating that the nickel content of the stainless steel is more than 4%, and the more vivid the rose red, the higher the nickel content.

Fourth, sparks. Spark identification is to grind stainless steel on a grinder and observe its sparks. If the spark is streamlined and has more dense knots, it is 200 series stainless steel with high manganese content; If there is no knotted flower, it is 300 or 400 series stainless steel.

1.It is made of aluminum, and the pipe is cultivated to protect the outer layer of the insulation layer. Galvanized iron or aluminum sheets are usually used.

2.It is a stainless steel pipe, and it is clearly written on the pipe.

3.The blue ring mark is a Zen blind zinc pipe, and the other pipes should be stainless steel pipes.

It is not difficult to distinguish between cast iron pipes, stainless steel pipes, and galvanized pipes.

1.Look at the material.

The main component of cast iron pipe is iron, so it will be easy to rust and corrode at room temperature, so the cast iron pipe is usually made of a relatively reliable anti-corrosion layer, generally asphalt paint or silver powder paint, and there are also epoxy resin paints, so what you see and feel on the appearance is the color and texture of the paint.

The main component of stainless steel pipe is alloy steel, as the name suggests, it is difficult to rust at room temperature, so what you see is the true color of stainless steel. As for the shiny decorative stainless steel, it has basically been polished.

Galvanized steel pipe is electroplated with a layer of zinc on the outside of the steel pipe. Because ordinary steel pipes (called welded steel pipes in engineering) are the same as cast iron pipes, they are easy to rust and corrode at room temperature, and the outer layer of galvanizing is to protect the pipe. What you usually see is the color of the galvanized layer, as shown in the comparison of pipes in Figure 3, the difference between stainless steel pipes and galvanized pipes is still obvious.

2.Look at the connection.

The cast iron pipe is not welded, and the socket connection, clamp connection, flange connection, etc., looks obvious.

The principle of galvanized steel pipe is not allowed to be welded, because welding will destroy the galvanized layer, and there will be electrochemical corrosion between the solder and the galvanized layer. Therefore, it is usually threaded connection, clamp connection, and threaded flange connection. The welding practice in Figure 3 should be wrong.

Stainless steel pipes are basically welded, and there are also welded flange connections and clamp connections. Because the stainless steel pipe has high strength, it is not easy to thread.

3.There are basically manufacturing standards, models, specifications and other parameters on the pipeline, just take a look at it.

Identification by magnets.

Magnets can basically distinguish between two types of stainless steel. Because chromium stainless steel can be attracted to magnets in any state; 304 chromium-nickel stainless steel is generally non-magnetic in the annealed state of bright search, and some will be magnetic after cold working.

However, 201 high manganese steel with higher manganese content is non-magnetic; The magnetic situation of Inconel stainless steel is more complex: 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.

Stainless steel pipes are widely used in our daily life and can be seen everywhere, so how to distinguish the quality of stainless steel pipe fittings? The difference between the quality of stainless steel pipe fittings is mainly due to the different nickel content, nickel is an excellent corrosion-resistant material, and the corrosion resistance and process performance of stainless steel are improved after being matched with chromium in stainless steel. However, in order to obtain pure austenitic structure of low-carbon nickel steel, the nickel content should reach 24, and only when the nickel contains 27 can the corrosion resistance of the steel in some media be significantly changed.

The corrosion resistance of 310S stainless steel plate mainly depends on its alloy composition (chromium, nickel, titanium, silicon, aluminum, etc.) and internal structure, and the chromium element plays a major role.

The positioning welding arc and end of the stainless steel pipe should be smoothly transitioned, the welding bead should not be too high, and the fusion must be good to prevent defects such as unwelded penetration and slag inclusion. If the positioning weld is cracked, the weld at the crack must be removed and the positioning weld must be repositioned. After positioning welding, if the interface is not flush, it should be corrected before it can be officially welded.

Try to avoid forced assembly, in case in the welding process, the positioning weld of weldment or formal weld cracking, if necessary, can increase the length of positioning weld, and reduce the spacing of positioning weld, or adopt heat treatment measures.

There are also many processing methods for stainless steel pipes. Many of them also belong to the category of machining, and the most commonly used are stamping, forging, roller processing, rolling, bulging, stretching, bending and combined processing. Stainless steel pipe processing is an organic combination of machining and metal pressure processing.