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What is stainless steel
Stainless steel is a chromium content of more than 12%, which has a stainless steel characteristics of a large group of iron-based alloy steel collectively.
The role of nickel in stainless steel is played after the combination of chromium
Nickel is an excellent corrosion-resistant materials, alloy steel is also an important alloying elements, nickel in the steel is the formation of austenite elements, but low-carbon nickel steel to get a pure austenite combination, nickel content to reach 24% And only 27% of nickel when the steel in some medium corrosion resistance significantly changed, so the nickel can not constitute a separate stainless steel. However, when nickel and chromium are present in stainless steel, nickel-containing stainless steel has many valuable properties.
The role of chromium in stainless steel
There are only one element that determines the properties of the stainless steel, which is chrome, and each of the stainless steels contains a certain amount of chrome. So far, there is no chromium-free stainless steel. The reason why chromium has become the main element of the performance of stainless steel, the fundamental reason is to add chromium as alloy elements to the steel, to promote its internal contradictory movement to help resist corrosion damage aspects of development. This change can be explained from the following:
1. The electrode potential of the chromium-based solid solution is increased.
2. Chromium absorption of iron by iron to iron
Purification is due to the anode reaction is blocked and caused by corrosion resistance of metals and alloys is improved. There are many theories that make up the purification of metal and alloy, mainly film theory, adsorption theory and electronic arrangement theory.
The thicker the same type of profile is harder?
In some cases, there are some tumbling materials on the market due to the production technology, carbon content is too high and contains a small amount of nitrogen lead to increased hardness; In addition, if Cr, Ni reduce the content, hardness will rise, the two types of material toughness and corrosion resistance Will also drop.
What kind of stainless steel is not easy to rust?
The main factors affecting the corrosion of stainless steel are three points:
First, the content of alloying elements, in general, the content of chromium in 14% and 1% nickel, steel is not easy to rust, the higher the content of chromium and nickel the better corrosive, such as 304 material nickel content in the 8- 10%, chromium content of 17-20%, such stainless steel in general will not rust.
Second: the manufacturing enterprises of the smelting process will also affect the corrosion resistance of stainless steel. Smelting technology is good, advanced equipment, advanced technology of large stainless steel plant Whether in the alloy element control, the removal of impurities, billet cooling temperature control can be guaranteed, so the product quality is stable and reliable, the inherent quality is not easy to rust. On the contrary some small steel plant equipment behind, backward technology, smelting process, impurities can not be removed, the production of products will inevitably rust.
Third: the external environment, the climate is dry and good environment is not easy to rust. And the air humidity, continuous rainy weather, or air containing high degree of acidification of the environment is easy to rust. 304 stainless steel, if the surrounding environment is too bad will be rusty.
Stainless steel is no magnetic, no magnetic is good stainless steel?
Many customers to the market to buy stainless steel, with a small piece of their own to see the goods when the suction, that is not good to absorb the stainless steel. Without the magnet will not rust. In fact, this is a wrong understanding. Stainless steel with no magnetic structure is determined by the organization, the molten steel in the solidification process due to the different temperature of the solidification will form a "ferrite", "austenite", "martensite" and other different structure of stainless steel " Body "" martensitic "stainless steel are with magnetic. While the "austenitic" stainless steel without magnetic. Our decorative stainless steel is generally "austenitic" stainless steel. This is because the "austenitic" stainless steel its comprehensive mechanical properties, process performance are good solderability, but only from the corrosion resistance with magnetic "ferrite" stainless steel is stronger than the "austenitic" stainless steel. The current market circulation of high manganese containing less nickel so-called 200 series, 300 series stainless steel without magnetic, but its performance and high nickel-containing 304 gap is large, so with stainless steel with no magnetic to determine the pros and cons of stainless steel is A misunderstanding is unscientific.
Why does stainless steel rust?
When the stainless steel pipe surface appears brown rust (point) when people were surprised: that "stainless steel will not rust, rust is not stainless steel, and may be what the steel out of the problem." In fact, this is a lack of understanding of stainless steel a one-sided error view.
Stainless steel has the ability to resist atmospheric oxidation - that is, stainless. But also has the ability to resist corrosion in media containing acids, alkalis and salts - that is, corrosion resistance. But its corrosion resistance is the size of its steel chemical composition, mutual state, the use of conditions and environmental media types and changes, such as 304, in a clean and clean atmosphere, there is absolutely excellent corrosion resistance, but will It moved to the beach area, with a large amount of salt in the sea fog, will soon rust, and 316 steel pipe is doing well. Therefore, not any kind of stainless steel, at any time can be resistant to corrosion, no rust.
Stainless steel is formed by its surface layer of very thin and strong and stable and stable chromium oxide film (protective film), to prevent oxygen atoms continue to infiltrate, continue to oxygen, and get the ability to resist corrosion. But for some reason, the film is constantly destroyed, the air or liquid oxygen atoms will continue to infiltrate or metal atoms in the iron constantly separated from the formation of loose iron oxide, metal surface will be constantly Rust. This surface film is damaged in many forms, more common in daily life are the following:
1. The surface of stainless steel deposits with other metal elements of dust or heterogeneous metal particles attached to the flow of air, the mixture of stainless steel and the condensed water, the two together into a micro-battery, triggering an electrochemical reaction, Protective film is damaged, called electrochemical corrosion.
2. Stainless steel surface adhesion of organic juice (such as melon, soup soup sputum, etc.), in the case of water and oxygen; constitute organic acids, long time to form organic acid corrosion of metal surface.
3. Stainless steel surface adhesion containing acid, alkali, salt substances (such as decorative walls of alkaline water, lime water spray test) caused by local corrosion.
4. In contaminated air (containing a lot of sulfide, oxide, hydrogen oxide atmosphere), in case of condensate, the formation of sulfuric acid, nitric acid, acetic acid liquid point, causing chemical corrosion.
The above situation can cause damage to the stainless steel surface protective film, causing corrosion. So, to ensure that the metal surface is permanently bright, we recommend:
1. Always clean the surface of the decorative stainless steel scrub, remove the attachment, to eliminate the external factors that cause corrosion.
2. There is a 201 stainless steel in the market is easy to rust in the coastal area, suitable for use in industrial pollution and air corrosion environment.
3. The sea area to use 304 stainless steel, 304 material can resist seawater corrosion.
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