Metal blackening

The surface of the metal blackening treatment, there are also called blue.

Blacking treatment is now commonly used methods of blackening and the emergence of the traditional alkaline heating blackening and later room temperature blackening of two kinds:

One, alkaline oxidation method of "bluing" liquid

1. formula: sodium nitrate 50 ~ 100 grams of sodium hydroxide 600 ~ 700 grams of sodium nitrite 100 ~ 200 grams of water 1000 grams

2. method: measured according to the formula, in turn, under the condition of stirring, the surface of the metal blackening treatment is also called bluing. Grams of water 1000 grams

2. Preparation: measured according to the formula, under stirring conditions, the material in turn to add them, dissolve, mix well.

3. Note:

(1) The metal surface must be washed and dried before the "hair basket" treatment.

(2) metal devices for "blue" treatment conditions and the carbon content of the metal, "blue" liquid temperature and metal devices in which the processing time can refer to the following table. Carbon content in the metal % working temperature (℃) processing time (minutes) start to terminate >0.7135-13714310-300.5-0.7135-14015030-50<0.4142-145153-15540-60 alloy steel 142-145153-15560-90

(3) Every other week or so on a regular basis to analyze the solution in the solution, the temperature and metal devices in which the processing time can refer to the following table. Week or so on a regular basis to analyze the content of sodium nitrate, sodium nitrite and sodium hydroxide in the solution in order to supplement the relevant components in a timely manner. Generally, all solutions should be replaced after half a year of use.

(4) metal "blue" treatment, it is best to use hot soapy water rinse for a few minutes, and then rinse with cold water. Then, and rinse with hot water, blowing on.

Two, acid oxidation "blue" solution

1. formula: phosphate 3 ~ 10 grams of calcium nitrate 80 ~ 100 grams of manganese peroxide 10 ~ 15 grams of water 1000 grams

2. method: according to the formula measured in constant stirring conditions, in turn, the phosphoric acid, manganese peroxide and Calcium nitrate into it, dissolve, mix well can be.

3. Note:

(1) The metal devices should be washed and dried first before "blueing" treatment.

(2) the protective film obtained by this method is black, its main component is composed of calcium phosphate and iron oxides, its corrosion resistance and mechanical strength are more than the alkaline oxidation method obtained by the protective film.

4. "Blue" working temperature of 100 ℃, treatment time of 40 ~ 45 minutes. In the treatment of carbon steel, liquid phosphate content control in 3 ~ 5 g / liter; treatment of alloy steel or cast steel, phosphate content control in 5 ~ 10 g / liter. Attention should be paid to regularly analyze the content of phosphoric acid in the liquid.

5. "Blue" treatment of metal devices after the cleaning method as above.