On the whole, we are resistant to air, water vapor and other weak corrosive media at the same time to prevent rust bar steel become stainless steel, in our lives, stainless steel is extremely wide range of applications, with the increasing number of stainless steel, a variety of types of stainless steel is also constantly appearing, austenitic stainless steel, as a common and widely used stainless steel on the market, has a high degree of toughness and Easy to cut, is widely used in industry and decoration, food and medical fields, however, is not stainless steel will not really rust? In recent years, austenitic as a common stainless steel, it will also rust, then, it rust what is the reason?
Rust causes
304 stainless steel material rust phenomenon, there may be the following reasons:
1. Chloride ions
Chloride ions are widely available, such as salt/sweat stains/seawater/sea breeze/soil and so on. Stainless steel in the presence of chloride ions in the environment, corrosion is very fast, even more than ordinary mild steel. So there are requirements for the use of stainless steel in the environment, and it needs to be wiped frequently to remove dust and keep it clean and dry. (This will give him a "misuse.") The following is an example from the United States. The United States has an example: an enterprise with an oak container containing a solution containing chlorine ions, the container has been used for nearly a hundred years, the nineties of last century, plans to replace the oak material is not modern enough to use stainless steel to replace the 16 days after the container due to corrosion leakage.
2. Solid solution treatment
The alloying elements are not dissolved into the matrix, resulting in low alloy content of the matrix organization, poor corrosion resistance.
3. Intergranular corrosion
This material without titanium and niobium has a tendency to intergranular corrosion. The addition of titanium and niobium, together with stabilization treatment, can reduce intergranular corrosion. In the air or chemical corrosion medium can resist corrosion of a high-alloy steel, stainless steel is a beautiful surface and good corrosion resistance, do not have to go through the color plating and other surface treatments, but to play the stainless steel inherent surface properties, used in a variety of aspects of a steel, usually called stainless steel. The representative performance of 13 chromium steel, 18-8 chromium-nickel steel and other high-alloy steel. Analyzed from the metallurgical point of view, because stainless steel contains chromium and the surface of the formation of a very thin film of chromium, this film is separated from the steel invasion of oxygen to play a role in corrosion resistance. In order to maintain the corrosion resistance inherent in stainless steel, steel must contain more than 12% chromium. It is used where welding is required. Lower carbon content allows the precipitation of carbides in the heat-affected zone near the weld to be minimized, and the precipitation of carbides may lead to intergranular corrosion of stainless steel in some environments. (Weld erosion)
4. Surface phenomenon
Surface mark phenomenon is 304 stainless steel deep processing or processed products after grinding, the occurrence of line or point concave mark defects on the surface of the product.
Causes: foreign matter on the surface, mold surface, scarring on the surface of the crimping pad.
Countermeasures: Remove foreign objects and scars before processing, and also remove orange peel by sufficient grinding.
The orange peel phenomenon refers to the 304 stainless steel molding products in the grinding or other circumstances, the surface of the phenomenon produced like the shape of the orange peel.
Reason: insufficient grinding?
Reasons: Inadequate grinding, the larger the processing, the more serious the orange peel, the larger the processing, the more serious the orange peel. Raw material grain coarseness, heat treatment softening.
Countermeasures: deep-processed products fully ground, choose the appropriate heat treatment conditions, control the grain size of raw materials.
We all know that a lot of things will change after mixing, the reaction of chemical experiments also let us have a deeper understanding of a kind of items change and not unexpected, no matter which kind of stainless steel, we can not guarantee that it will never rust, due to the different stainless steel processing materials, we can not be determined in the use of a certain day, the material inside the material of certain elements will be and the outside world of the item Reaction and rust, so it may be due to chlorine ions and solid solution treatment and other factors and rust, these need to be explored to understand the causes of rust, if your home austenitic stainless steel rust, there may be one of the above is the cause of rust.
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