High Strength Blackened Bolt
Blackening process is blackening during tempering in heat treatment process. Different blackening process will directly affect the quality of screws.
Attention should be paid to the following problems in the treatment process of high strength blackened bolt:
Acid and alkali substances are strictly prohibited, which will damage the film-forming function of the blackening agent. The application temperature should be maintained between 40-50 ℃, and the blackening agent should be mixed frequently when it is not used, so as to ensure that the blackening agent is in good condition. At the same time, attention should be paid to the use of post cleaning solution, and inorganic salt cleaners should be prevented as far as possible, because inorganic salt has the function of reducing after the water film is dry, As a result, the salts in the cleaning solution will be brought into the blackening agent, and the change from quantitative change to mutation will eventually damage the application function.

After the blackening agent has been used for a period of time, usually half a year, the blackening agent must be exchanged in the whole tank.
The quality problems occurred in the blackening process of high strength blackened bolts can be dealt with in the following ways: 1. blackening again from the tempering furnace. 2. Adjust the concentration of blackening agent. 3. Replace the rear cleaner.

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