Root cause Analysis of Rust of Stainless Steel
Stainless steel material rust phenomenon, there may be the following reasons:
Chloride is widely present, such as salt / perspiration / sea water / sea breeze / soil and so on. Stainless steel in the presence of chloride ions in the environment, corrosion quickly, even more than ordinary low carbon steel. So the use of stainless steel environment requirements, and the need to often wipe, remove the dust, keep clean and dry. (So that you can give him a "improper use.") The United States has an example: an enterprise with an oak container containing a chloride ion solution, the container has been used for nearly a hundred years, the last century, , Due to oak material is not modern enough, the use of stainless steel after 16 days of container replacement due to corrosion leakage.
2) solution treatment
Alloying elements are not dissolved in the matrix, resulting in low matrix alloy composition, corrosion resistance is poor.
3) intergranular corrosion
This kind of titanium and niobium-free materials tend to have intergranular corrosion. Adding titanium and niobium, coupled with a stable 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, without going through the surface treatment such as color, and play the inherent surface properties of stainless steel, used in more A kind of steel, usually called stainless steel. On behalf of the performance of 13 chrome steel, 18-8 chrome nickel steel and other high alloy steel. From the perspective of metallography, because the stainless steel contains chromium and the surface to form a very thin chromium film, the membrane separated from the steel intrusion of oxygen from the role of corrosion resistance. In order to maintain the inherent corrosion resistance of stainless steel, steel must contain more than 12% of the chromium. For occasions where welding is required. The lower carbon content minimizes the amount of carbides that are precipitated in the heat affected zone near the weld, and the precipitation of carbides can cause intergranular corrosion (weld erosion) in certain environments.
4) surface marks phenomenon
Surface marks phenomenon refers to the deep processing of stainless steel or processed products after grinding, in the product surface line or point-like concave mark defects.
Reason: the surface, the mold surface has foreign body, blanket pad surface scars.
Countermeasures: in the processing before the removal of foreign body, scars, but also through the full grinding to remove Orange peel: Orange peel phenomenon refers to the stainless steel molding in the grinding or other circumstances, the surface of the same shape as the orange peel phenomenon.
Reason: grinding is not sufficient, the greater the processing of orange peel more serious, coarse raw materials, heat treatment softening.
Countermeasures: deep processing of products fully grinding, select the appropriate heat treatment conditions, control the grain size of raw materials.