Some Knowledge about Stainless Steel Pipes that you may Not know

February 26, 2024
Some Knowledge about Stainless Steel Pipes that you may Not know

Some Knowledge about Stainless Steel Pipes that you may Not know

1. Stainless steel plate weight calculation formula: length * width * thickness * specific gravity = weight

       For example: 1.5mm*1000mm*2000mm, 1*2*1.5*7.93=23.79kg

 2. Stainless steel pipe weight calculation formula: (diameter - wall thickness) * wall thickness * specific gravity = meter weight

       For example: 108*4mm tube, (108-4)*4*0.02491=10.36kg

3. What is the difference between 304 and 201 stainless steel pipes:

      1. Prices are different: 304 has better quality but is more expensive, while 201 is worse but has cheaper price.

      2. Different compositions: 304 is 8 nickel 18 chromium, 201 is 1 nickel 13 chromium

      3. Different anti-rust properties: 304 has strong anti-rust properties, while 201 has weak anti-rust properties.

      4. Different strengths: The yield point of 304 steel is 205MP and the anti-resistance strength is ≥515Mpa, while the yield point of 201 steel is 275MPa and the tensile strength is ≥520MPa.

Why does stainless steel rust?

      1. Many people think that stainless steel pipes will definitely not rust. This is a wrong and one-sided view. 

First of all, the rustlessness and corrosion resistance of stainless steel pipes are conditional. 

Stainless steel pipes are steel pipes that do not rust in weakly corrosive environments such as atmosphere and fresh water, and the chromium content in the steel must be ≥12%. 

If the chromium content is low or it is not used in a weakly corrosive environment such as the atmosphere (including in a weakly corrosive environment such as the atmosphere, 

but there is local enrichment and concentration of Cl-), rust will occur. Acid-resistant steel pipes are corrosion-resistant steel pipes in strong corrosive media such as acids, alkalis, and salts. 

However, they are also corrosion-resistant under certain conditions, such as medium type, temperature, concentration, impurity content, flow rate, pressure, etc. 

There is no stainless steel pipe in the world that will not rust or be corrosion-resistant under any conditions.

     2. The surface of stainless steel accumulates dust containing other metal elements or attachments of heterogeneous metal particles.

In humid air, the condensed water between the attachments and stainless steel connects the two into a micro-battery, triggering an electrochemical reaction. , 

the protective film is damaged, which is called electrochemical corrosion.

   3. Organic juices (such as vegetables, noodles, etc.) adhere to the surface of stainless steel. 

In the presence of water and oxygen, organic acids are formed. For a long time, organic acids will corrode the metal surface.

     4. Substances containing acids, alkalis, and salts adhered to the surface of stainless steel (such as alkaline water and lime water sprayed when decorating walls) cause local corrosion.

     5. In polluted air (an atmosphere containing a large amount of sulfide, oxide, and hydrogen oxide), when it encounters condensed water, 

nitric acid and acetic acid liquid points are formed, causing chemical corrosion.

4. The difference between stainless steel intermediate frequency furnace and refining furnace:

       1: Intermediate frequency is used for smelting scrap metal. It uses alternating current to generate an alternating magnetic field. 

The metal in the alternating magnetic field generates alternating induced potential and induced current. 

The direction of the induced current is the same as the direction of the current in the furnace induction coil. on the contrary. Under the action of induced electromotive force, 

the heated metal generates an induced current. When the current passes through the stainless steel plate, it does work to overcome the resistance of the metal and generates heat. 

The intermediate frequency furnace uses this heat to heat and melt the metal, thereby achieving the purpose of melting. 

The intermediate frequency furnace can only make steel once, especially in terms of raw materials, which cannot be flexibly controlled. 

Therefore, stainless steel scrap and iron sand are generally used for smelting 321 stainless steel plates. 

This smelting method cannot control the content of certain elements, so the product quality is relatively inferior, and it is generally not used in deep processing and other product industries.

       2: The refining furnace is for raw ore smelting, commonly known as the AOD refining furnace. 

While blowing oxygen into the molten steel under standard atmospheric pressure, it blows in inert gases (Ar, N2) to achieve a false vacuum effect by reducing the CO partial pressure, 

thereby making the carbon The content is reduced to very low levels and inhibits the oxidation of chromium in steel. 

It is suitable for the production of low-carbon and ultra-low carbon stainless steel, and it is easy to control the S content in special steel below 0.005%. 

The AOD refining furnace can perform secondary steelmaking, and generally can flexibly add or reduce relevant elements to achieve refining purposes; 

during the smelting process Scrap iron and iron sand are generally used for steelmaking. 

The product quality is relatively high and the ductility is good. Deep-drawn products of 321 stainless steel plates are generally smelted in refining furnaces.

      Three: The material of the intermediate frequency furnace is unstable and easy to rust, while the material of the refining furnace is stable and not easy to rust.

      Four: Elemental distinction: The carbon content of the intermediate frequency furnace is C 0.1% or more, and the carbon content of the refining furnace is less than 0.1%.

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