Stainless steel generally contains high-quality metal elements such as chromium (Cr), nickel (Ni), molybdenum (Mo), and titanium (Ti). Common stainless steels are chromium stainless steels, which contain Cr>=12% or more. Nickel-chromium stainless steel contains Cr>=18% and Ni>=12%.
Classification from stainless steel metallographic structure: austenitic stainless steel, martensitic stainless steel, ferritic stainless steel, duplex stainless steel and precipitation hardening stainless steel.
Varieties of stainless steel surface treatment:
(1) Surface bleaching treatment
(2) Bright treatment of surface mirror stone
(3) Surface coloring treatment
1. Surface natural whitening
During the processing of stainless steel, black oxide scale is produced by coiling, edging, welding or warm surface treatment. This hard gray-black oxide scale was previously removed by strong corrosion methods using hydrofluoric acid and nitric acid. However, this method is costly, pollutes the environment and is harmful to the human body, and is gradually being eliminated.
There are currently two methods for this oxide scale treatment:
(1) Use sandblasting (pill) sand method. (2) Adopt chemical method.
That is, use a one-minute non-polluting pickling passivation paste and a non-toxic cleaning solution with inorganic additives at room temperature for dip washing. So as to achieve the purpose of whitening treatment of stainless steel. Basically it looks like white light. This method is more suitable for large and complex products, and it is worth popularizing and applying.
2. Brightening treatment method of mirror surface on stainless steel
According to the complexity of stainless steel products and the requirements of users, mechanical polishing, chemical polishing, electrochemical polishing and other methods can be used to achieve mirror stone gloss.
3. Surface coloring
The coloring of stainless steel not only gives various colors to stainless steel products, increases the variety of products, but also improves the wear resistance and corrosion resistance of products.
The stainless steel coloring methods are as follows:
(1) Ion deposition oxide or oxide method
(2) High temperature oxidation method
(3) Chemical oxidation method, electrochemical oxidation method
(4) Gas phase cracking method
A brief overview of the various methods is as follows:
(1) Ion deposition oxide or oxide method is to place the stainless steel workpiece in the vacuum coating machine for vacuum evaporation plating: for example: titanium gold-plated watch case and watch strap. Generally golden. This method is suitable for mass production. Because of the large investment and high cost, small batch products are not cost-effective.
(2) The high-temperature oxidation method is to immerse the workpiece in a specific molten salt and maintain it within a certain process range, so that the workpiece forms an oxide film with a certain thickness and exhibits various colors.
(3) The chemical method refers to the color of the film formed by chemical oxidation in a specific solution. Generally, the "inco method" is often used. However, to ensure that the color of a batch of products is consistent, it must be controlled by reference telegram.
(4) The electrochemical method is to form the color of the film through electrochemical oxidation in a specific solution, which is used commercially.
(5) The gas-phase cracking method is more complicated and less used in industry.
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