What is Blue Tempered Steel Strip?

The reaction formula can be expressed by the following equation:

3Fe + 4H2O(g) = Fe3O4 + 4H2 (under high temperature conditions) .

There are many methods of "blue tempered", and alkaline or acidic liquids are often used to produce a blue-black protective layer on the metal surface. In ancient China, the method of blue tempered was commonly used for silver jewelry. 

The silver was put into alkali or acid solution and heated, and the temperature generally reached 90--110 degrees. The silver began to yellow, then turned blue-red, then blue-black, and finally black. Whichever color is needed, just take it out in time, and then wash it, so that no matter if it is blue-black or black, it can be called "blue tempered".

This is steel blue tempered steel strip, few coils packed in one coil.

There are some coils are going to be packed.

Application of Blue Tempered Steel

The most common use of blue tempered steel is to slited in blue tempered strip as steel packing tape, packing strip.

This photo shows 4 coils of carbon blue tempered steel strip will be packed into one package, and you can see our production line in this photo too.

Production Method of Blue Tempered Steel

Ⅰ. Alkaline oxidation method "blue tempered" liquid

1. Recipe: 50-100 grams of sodium nitrate, 600-700 grams of sodium hydroxide, 100-200 grams of sodium nitrite, 1000 grams of water

2. Preparation method: After measuring according to the formula, under stirring conditions, add each material in turn, dissolve and mix evenly.

3. illustrate:

(1) The metal surface must be washed and dried before "blue tempered" treatment.

(2) The conditions for "baking blue" treatment of metal devices are related to the carbon content in the metal. The temperature of the "blue tempered" liquid and the processing time of metal devices in it can refer to the following table. Carbon content in metal % Working temperature (℃) Treatment time (min) Start and end > 0.7-0.7135 < 0.4142-145 Alloy steel 142-145

(3) Analyze the content of sodium nitrate, sodium nitrite and sodium hydroxide in the solution on a regular basis every one week or so, so as to replenish the relevant components in time. Generally, all solutions should be replaced after half a year of use.

(4) After the metal "blue tempered" treatment, it is best to rinse with hot soapy water for a few minutes, and then rinse with cold water. Then, rinse again with hot water and blow dry.

Ⅱ. Acid oxidation method "blue tempered" liquid

1. Recipe: 3-10 grams of phosphoric acid, 80-100 grams of calcium nitrate, 10-15 grams of manganese peroxide, 1000 grams of water

2. Preparation method: After measuring according to the formula, under the condition of constant stirring, add phosphoric acid, manganese peroxide and calcium nitrate in sequence, dissolve and mix evenly.

3. illustrate:

(1) Metal parts should be cleaned and dried before "blue tempered" treatment.

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

4. The working temperature of "blue tempered" is 100℃, and the processing time is 40-45 minutes. When treating carbon steel, the phosphoric acid content in the liquid is controlled at 3-5 g/L; when treating alloy steel or cast steel, the phosphoric acid content is controlled at 5-10 g/L. It should be noted that the content of phosphoric acid in the liquid medicine should be analyzed regularly.

5. The cleaning method of metal parts after "blue tempered" treatment is the same as above.

This photo shows a part of our workshop of steel strip production line.

Our factory in production and do not influenced by COVID-19, every labor and staff Nucleic Acid Test Negative and vaccinated 3 doses of the COVID-19 vaccine.