The surface of night cooking process is very bright. Can you cook directly in the jar without salting?

You can't. Cooking at night is also called black cooking. The chemical solution reacts with the material of the workpiece itself to form a coating, and the thickness of the coating after oxidation treatment is 0.5- 1.5 micron, which has no significant influence on the size and accuracy of the part. Oxidation treatment of steel parts is widely used for the general protection and decoration of mechanical parts, precision instruments, cylinders, springs, weapons and daily necessities. Its film has good wear resistance, dark color and luster, and is extremely beautiful.

The general technological process of blackening is: decontamination and degreasing-cleaning-pickling and derusting-cleaning-blackening-cleaning-saponification-oil soaking-finished product.

Oxidation treatment of steel surface-blackening

1。 Alkali boiling black

2。 Acid-based cooking

Formula proportion of base boiling black:

650 grams of sodium hydroxide

250 grams of sodium nitrite

Water 1L

Temperature135 ——145℃ (boiling)

Time: 10-30 minutes.

Advantages: the price is cheap and the materials are easily available. With the increase of specific concentration (within a certain range) and reaction time, the oxide film gradually becomes thicker.

Disadvantages: the mechanical strength-wear resistance and adhesion are relatively weak, so it is relatively difficult to apply alloy materials.

Formula proportion of acid-base cooking black:

Barium nitrate: 40-50g

Phosphoric acid: 3-5g.

Water: one liter

Temperature: 98- 100℃

Time: 30 minutes

Advantages: Good mechanical strength-wear resistance and adhesion, and can also be used for alloy reaction. With the increase of concentration (within a certain range) and reaction time, the oxide film gradually becomes thicker.

Disadvantages: the material price is relatively high. Barium has great influence on human body and environment.

Note: For the first two treatments, the surface must be clean. After oxidation, it must be washed and dried with clear water in time.

Supplementary treatment-saponified film and oiled film.

After cleaning and drying, the blackened saponified film is boiled in 80-90 degree soapy water solution containing 2-3% soapy water (20-30g solid soap/1 liter of water) for 5- 10 degree minutes.

The oil film, after saponification, is washed with clean water, dried, and immersed in 100- 120 degree engine oil for 5- 10 minute.

Note: With different steel grades, the alloy composition and carbon content will have different colors after the reaction. For example, manganese steel is brown after reaction, and chromium steel is gray.