1. Different process
bluish
High-temperature chemical oxidation is a traditional method of bluing, using a concentrated alkaline treatment solution with sodium nitrite, and treating it at a temperature of about 140 ℃ for 15min-90min. High temperature chemical oxidation obtains an oxide film mainly composed of magnetic iron oxide, and the film thickness is generally only 0.5μm-1.5μm, and finally can reach 2.5μm. The oxide film has a good adsorption type. The corrosion resistance of the oxide film can be greatly improved by immersing the oxide film in oil or doing other post-treatments.
blackened
The work-piece is usually immersed in a strong oxidizing chemical solution. For example, in an aqueous solution of sodium hydroxide (600g/cm3) and sodium nitrite (100g/cm3) with a boiling temperature of 147-152°C, a layer of beautiful, dense and rust-proof black iron oxide will be formed on the surface after a certain period of time. film.
2. Different processing methods
bluish
1. Decontamination: cleaning treatment (decontamination agent), the quality of decontamination rust and oil removal affects the quality of bluing.
2. Cleaning: Rinse with clean water and wipe the surface clean. Let dry.
3. Bluing: Put the work-piece into the tank that has been prepared with water, and start heating, so that the temperature reaches 145-155 ℃, and the time is kept for 50-60 minutes. Special Note: It is strictly forbidden to add water to the liquid in the tank that is being heated or has been heated.
4. Cleaning: It is best to rinse with hot soapy water for a few minutes, then rinse with cold water. Then, rinse with hot water and dry.
5. Anti-rust: Apply engine oil at the end (analyze the content of sodium nitrite and sodium hydroxide in the solution every other week or so, so as to replenish the relevant components in time. Generally, all solutions should be replaced after half a year of use).
blackened
In the metal mold, the commonly used treatment methods are heat treatment (heat treat), TD (TD-coating), blackening (blackening)
3. Different effects
bluish
The bluing film alone has poor corrosion resistance, but after oiling, waxing or varnishing, the corrosion resistance and friction resistance are improved. When bluing, the size and finish of the workpiece have little effect on the quality. Therefore, it is often used in precision instruments, optical instruments, tools, hardness blocks and standard parts in the machinery industry.
Because the oxide film is very thin, it has little effect on the size and accuracy of the parts, so it is widely used in precision instruments, optical instruments, weapons, and machine manufacturing.
blackened
The black oxide film formed by blackening has a thickness of 0.5-1.5 μm, and its corrosion resistance is lower than that of other chemical films.
