304, 316
mysterious code names?
In our daily life
Stainless steel is a common metal material
It is widely used
As small as a spoon
As large as aerospace equipment
Stainless steel can be seen everywhere
Stainless steel is carbon steel (carbon content is less than 2%) A branch that adds chromium (Cr), nickel (Ni), molybdenum (Mo), manganese (Mn), titanium (Ti), niobium (Nb) and other chemical elements during the smelting process to change the metallographic structure of the steel. Changes form a dense protective film on the surface of the material, giving it a beautiful appearance and good corrosion resistance.
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304 stainless steel , 316 stainless steel
The most common stainless steels in our lives are mainly 304 and 316. What do these two code names mean? The digital grade is actually equivalent to the "ID card" of stainless steel. Different regions have different numbering methods for stainless steel:
American standard
uses fixed-digit numbers to represent the steel series, and the last two digits are numbered in order
American standard 304
American standard 316
National standard
Use chemical element symbols and Arabic numerals to directly display the alloy composition of stainless steel.
is equivalent to the American standard 304
is equivalent to the American standard 316
. Most of the stainless steel on the market is manufactured in accordance with the American ASTM standards, and the numerical grades are simple, easy to remember and easy to circulate, so people are more accustomed to it. Use numbers to represent stainless steel types.
304 stainless steel metallographic diagram
316 stainless steel metallographic diagram
304 stainless steel generally requires a chromium content of more than 18% and a nickel content of more than 8%. Due to its good corrosion resistance, heat resistance and other advantages, it is often used in food processing , storage and transportation, or used in agriculture, auto parts, building materials, chemical industry and other industries. It is the most widely used stainless steel, accounting for almost more than half of the total stainless steel production. 316 stainless steel generally requires a chromium content of more than 16%, a nickel content of more than 10%, and a molybdenum content of more than 2%. The increase in the proportion of the two alloying elements of nickel and molybdenum makes it have better resistance to (acid) Corrosion resistance, welding performance, etc., therefore have a higher price, and play a greater role in medical surgery, precision industrial components, etc.
What is food grade stainless steel ?
According to the "Hygienic Standard for Stainless Steel Tableware Containers" GB 4806.9-2016, food-grade stainless steel should pass a migration test, that is, put the stainless steel material into a simulated food solution (usually an acidic solution) for immersion, and meet the requirements. After a certain amount of time, test whether some elements precipitate out of the solution.
If the amount of precipitation of the above five harmful substances does not exceed the standard, it can be called food-grade stainless steel.
When we buy tableware and kitchenware on a daily basis, in addition to looking at the stainless steel grade, we should also pay attention to whether the product packaging clearly states that it meets GB 4806.9-2016. Only food-grade stainless steel that has passed standard testing can be used with confidence.
stainless steel ≠ does not rust
If rust spots appear on the surface of stainless steel,
is there a problem with the product quality?
is not! The reason why stainless steel is not easy to rust is because the addition of chromium forms a protective self-repairing oxide film on the surface of the steel. Therefore, it has better resistance to atmospheric corrosion and corrosive media such as acids, alkalis, and salts. . However, the corrosion resistance changes with the chemical composition of the material itself (production process level), usage conditions and environmental type. 304 stainless steel, which is as strong as "Taiwan Balm", has absolutely excellent corrosion resistance in a dry and clean atmosphere. However, if it is moved to sea fog containing a large amount of salt, it will soon rust.
Pay attention to the maintenance of stainless steel in daily life
Increase the service life of stainless steel products
1
Do not store vinegar, salt and other food for a long time. Such food may produce electrolyte reactions with stainless steel, destroy the protective film, and release toxic substances that are harmful to health.
2
Try to keep the use environment as dry as possible to prevent other metal elements from adhering to the surface and reduce the possibility of electrochemical corrosion caused by electrochemical reactions.
3
Regularly remove organic juice (such as vegetable and fruit residues, soup, etc.) adhered to the surface of stainless steel. Under the action of water, organic acids will be formed, causing corrosion to the metal.
4
Do not use stainless steel products to cook items containing alkaloids, such as traditional Chinese medicine, and try to avoid spraying alkaline water , lime water , etc. to avoid corrosion.
(some information comes from the Internet)
provided by: Municipal Special Inspection Institute
