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What are the general methods for preventing rust on the surface of forgings?

Update:07-01-2021
Summary:

After the forgings are heat treated, they need to be cl […]

After the forgings are heat treated, they need to be cleaned first to remove the residual salt, oil and dirt on the surface of the forgings, and then sandblasting or shot blasting must be used to remove various oxides such as oxide scales that are difficult to remove. The link is to carry out surface anti-rust treatment on the forging. Surface anti-rust treatment includes two stages: preparation before anti-rust and anti-rust treatment using anti-rust oil.

1. Preparation before rust prevention

Although the forgings have been cleaned and cleaned after the heat treatment, the surface of the forgings needs to be cleaned again before the anti-rust treatment. Because in the process of forging turnover, the surface of forgings will also be contaminated by oil (due to the oil burst in the transfer box). For precision forgings, operators will also stick sweat on the surface of the forgings when carrying them by hand. These surface pollution must be completely eliminated before rust prevention.

The preparation work at this stage is exactly the same as the above-mentioned surface cleaning process and will not be repeated.

Forging

2. Anti-rust oil and anti-rust

The use of anti-rust oil for anti-rust is based on grease or resin as the main body, and then a temporary anti-rust paint composed of oil-soluble corrosion inhibitor. The anti-rust effect is mainly manifested in the following aspects:

1. The corrosion inhibitor molecules dispersed in the oil film can be directionally adsorbed on the metal and the oil surface to form a multi-molecule interface film, which has a shielding effect on corrosion factors.

2. The anti-rust oil is hydrophobic, which can stabilize the displaced water in the oil.

3. It can improve the absorption force of the oil film to the metal, increase the resistance and reduce the activity.

4. It can inhibit the formation of corroded batteries and prevent atmospheric corrosion.

In the anti-rust operation, the anti-rust oil is usually cold coated, and the anti-rust grease is usually hot coated. When hot dip coating is used, the temperature should be reduced as much as possible to increase the thickness of the oil film. At the same time, with plastic film packaging, the anti-rust effect of forgings can be greatly improved.

Three, the choice of anti-rust oil

Depending on the machining process, the rust prevention after heat treatment can be a temporary rust prevention between processes, or it can be the final rust prevention of the finished product. The requirements of the two are different, and the rust prevention oil used is also different.

When selecting an anti-rust oil between processes, consider that the forgings are in contact with the operator's hands during processing and turnover, which will easily produce fingerprint rust on the surface of the forgings. At this time, it is best to choose a replacement anti-rust oil. Its quality requirements should meet the standard of No. 4 replacement type antirust oil in SH/T0692-2000. In its performance indicators, human sweat changeability and human sweat cleansing are the key points.

Forging

Sometimes, because forgings cannot be turned around in time, when overlapping storage is required in intermediate warehouses, rust or overprinting on the overlapping surface must be avoided, especially for cast iron products.

The length of the anti-rust period of the finished product storage requires consideration of factors such as whether the product is backlogged in the factory or whether it can be sold in time, whether it is used directly at the user or needs long-term storage. The commonly used anti-rust oils for sealing of finished products include solvent-diluted anti-rust oil, lubricating oil-type anti-rust oil, grease-type anti-rust oil and gas phase anti-rust oil. Its quality should conform to SH/T0692-2000 standards.

In addition, export products need to be transported by air or sea to tropical or frigid regions. At this time, it is necessary to choose anti-rust oil according to the structure and material of the product.More about:p20 steel

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