Can steel machining tured metal parts do black oxidation？

In daily life, you will encounter a variety of colors, everyone has their favorite color, there are many people who have special favorite blacks, whether it is a design master or ordinary, some people are fascinated. It is fascinated.

Whether it is a classic black costume or black household items, cars, art, etc. have a very important status. Various steel machining tured metal parts products have also produced constant improvement and improvement. Although iron products have great convenience, they are also very easy to rust. Because iron is exposed to air, oxygen will produce oxidative reaction results in rust. Considering our product durability and environmental protection, we usually have a rear surface treatment.

What is the black oxidation of steel machining tured metal parts?


 

After the various steel machining tured metal parts products are in contact with the air, a layer of oxide film is naturally formed on the surface, but the film is not very complete and dense, so it is easy to oxidize and corrode from surfaces.

Black oxidation uses various chemicals to produce chemical reactions on the steel machining tured metal parts surface to attach a black oxide film.

The purpose of black oxidation is to prevent the oxidation of steel machining tured metal parts, to completely isolate the metal parts from the air, and to improve the anti-rust ability. After the black is oxidized, the surface gloss of the steel machining tured metal parts can be increased, making it more beautiful, and reducing the number of parts. Deformation of the workpiece caused by internal or external forces.

Because steel machining tured metal parts black oxidation has many advantages such as short machining turning time, low cost, simple and safe operation, etc., it is widely used in steel machining tured metal parts surface treatment; but at the same time, the disadvantage of black oxidation is also particularly obvious,that is,the pollution is more serious.

Black oxidation method

The black surface treatment of steel machining tured metal parts is made of asphalt or paint, which can adhere to the surface of steel to achieve corrosion resistance after drying.

There are now two commonly used black oxidation methods.

One is to use alkali heating to blacken the steel machining tured metal parts surface. This black oxidation process is usually used for high carbon steel.

The other is to oxidize at room temperature, and low-carbon steel is commonly used, which has a better effect.
 

The black oxidation on the surface of the steel is also called blue oxidation. The surface oxidation layer is dense and smooth to protect the interior of the workpiece from oxidation.

At a high temperature of 550°C, it becomes blue after oxidation, so it is called blue oxidation.

At low temperatures, the oxidized oxide layer appears black, which is called black oxidation.

Production process: blue (black) operation process steel machining tured metal parts clamping → oiling → cleaning → pickling passivation → oxidation → cleaning → saponification liquid → boiling water washing → inspection.

steel machining tured metal parts oxidation process

(1) Workpiece

Use workpiece, size, design, professional fixture. Sufficient voids can remain in the middle of the workpiece, and the workpiece cannot touch such that each steel machining tured metal parts can be completely immersed in an oxidized solution.

(2) Degreasing

The purpose is to remove oil stains on the surface of the steel machining tured metal parts. There should be no oil stains on the surface of the workpiece, and an anti-rust agent should be used for anti-rust treatment. Oil will affect the quality of black oxidation and will contaminate the degreasing liquid pool.

Heat the oil to 80~90℃, and then immerse the work piece within 30 minutes. If there are more stains, it will increase the oiling time.
 

(3) Pickling

The purpose of pickling is to remove oxides and rust on the surface of the steel machining tured metal parts. Even if no rust on the surface is observed, pickling should be carried out. This is good for oxidation and does not affect quality.

The pickling solution usually uses industrial concentrated hydrochloric acid with a concentration of about 15%, and the steel machining tured metal parts is completely placed in the solution for about 30 minutes.

(4) Black oxidation

After degreasing and pickling, the clean workpiece can turn black.

The temperature of the blackening solution is about 130°C, and the temperature of the bluing solution is 550°C. The soaking time must be controlled according to different steel machining tured metal parts workpiece materials. For example: medium carbon steel with high carbon content oxidizes faster and the immersion time can be shorter. High-carbon steel with low carbon content is slower to oxidize, so the immersion time must be longer. Carbon steel, especially ferritic stainless steel, has some residual austenite on the surface of the workpiece, which has strong resistance to alkaline solutions and is not easy to transform into Fe3O4, because the steel machining tured metal parts surface immersion time takes a long time.

For some steel machining tured metal parts with high black oxidation requirements, perform black oxidation again after the first water washing, and after repeated many times, a uniform and dense oxide film can be obtained.

(5) Saponification liquid

After the blackening treatment, remove the workpiece from the blackening liquid pool, and rinse the chemical solution on the surface of the steel machining tured metal parts with clean water.

The steel machining tured metal parts product is baked or blown to remove the moisture on the surface of the workpiece, and then the workpiece is soaked in a soap solution and coated with oil. These steps are to increase the corrosion resistance of the workpiece and increase its surface gloss to make it more beautiful.

(6) Inspection

After the oxidation is completed, check the appearance，corrosion resistance and adhesion of the steel machining tured metal parts to see if it meets the standards. Take three pieces at random and put them in a 2% sodium sulfate solution for 20 seconds. If the oxidation of a certain part is not up to standard, the steel turned machined parts in the entire tank needs to be black-oxidized to increase the thickness of Fe3O4, which takes a long time.

TO sum up

If you want to understand the black oxidation process of steel machining tured metal parts, our expert team has a wealth of knowledge of anodizing processing technology to ensure the surface quality of steel turned machined parts for our customers. If you want to know what kind of surface treatment and the best processing solution are suitable for your part, please contact a member of the VMT team. We will provide you with 24-hour online service and quotation!