Experts will show you what is the fastener blackening technology

Fasteners are a kind of parts that are widely used in our daily life, and the blackening process of fasteners is a processing technology that optimizes fasteners and prevents rust and aging.

Blackening is the blackening during tempering in the heat treatment process. The production process of blackening will have various specific technical quality problems due to different companies, and these changes will directly affect the quality of fasteners.

1. There are three main types of common problems in the use of waste heat blackening agent:

The problem of fasteners during wire phosphating is that the phosphating film is too thick. In severe cases, it will peel off and affect the adhesion of the blackened film. Redness and rust on the working surface will appear after tempering during the heat treatment process. The solution to this problem, such as pretreatment before the fastener is fed into the heat treatment, that is, cleaning with alkali or acid, to remove the phosphate film on the surface of the workpiece.

2. Red rust is produced on the surface of the workpiece after heat treatment and tempering. There are several situations that may cause:

a, produced by surface phosphate film;

b. After the processing fastener enters the heat treatment, the cleaning liquid in the cleaning tank adheres to the surface of the part. When the furnace mouth temperature is too low when entering the heating furnace, rust will occur during the moisture drying process; (Guide: What do you know Is it electrophoresis? Detailed explanation of fastener electrophoresis process) c. After oil quenching, due to the aging of the oil or the high temperature of use, the carbon in the quenching oil is precipitated and adsorbed on the surface of the workpiece (small workpieces are especially common). After entering the tempering furnace, due to the effect of carbon and temperature, iron oxide is produced, resulting in a red rust color;

d. If the water quenching medium is used for a long time, the anti-rust ability in the medium will decrease and the parts will rust.

In view of the above problems, the methods to deal with are:

a Removal of phosphating film;

b Increase the heating temperature of zone 1 of the mesh belt furnace;

c. When using oil quenching agent, the reasonable temperature should be below 60℃ to reduce the aging process of the oil;

d, the control of the carbon potential in the furnace, under the premise of ensuring no decarburization, reduce the carbon potential as much as possible;

e, often check the data of water quenching medium, add rust inhibitor if necessary.

3. It should be noted here that the blackening agent should be used under the prescribed operating methods. It is strictly forbidden to bring in acid and alkali substances, which will destroy the film-forming performance of the blackening agent. The use temperature should be kept between 40-50 ℃, and it must be stirred frequently when not in use to keep the blackening agent in good condition. Attention should be paid to the use of post-cleaning liquid, and avoid the use of inorganic salt cleaning agents as much as possible. Because inorganic salts have the ability to reduce the water film after drying, they will bring the salts in the cleaning liquid into the blackening agent, resulting in quantitative changes. Changes to qualitative change will eventually destroy the performance. After the blackening agent has been used for a period of time, usually half a year, the tank must be adjusted to replace the blackening agent.

The quality problems caused by the blackening of fasteners can be solved by the following methods: (1) Blacken again from the tempering furnace; (2) Adjust the concentration of the blackening agent; (3) Replace the cleaning fluid.

To sum up, it is the basic knowledge of fastener surface blackening technology.

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