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Main performance index

1, mechanical performance indicators

The first is the mechanical properties of hot-dip galvanized products.

Mechanical properties can be defined as the properties of the product that can be confirmed by tensile tests, such as yield strength, tensile strength, elongation, n value, r value, and so on.

BH steel or aluminum killed steel has an aging phenomenon, and once the aging occurs and stamping is carried out after a long time, slip will occur. This is the orange peel on the surface of the steel plate after stamping, which is slippage. This is a serious orange peel phenomenon after the stamping of a part. Normally, it is necessary to ensure the production process, such as ensuring the flat elongation rate, eliminating the yield platform during production, and suggesting to the user that these steel be used as soon as possible after leaving the factory to prevent aging.

2, coating performance index

The most important performance of hot-dip galvanized products is the coating performance, which mainly refers to the corrosion resistance of the coating and the adhesion performance of the coating.

Corrosion resistance includes resistance to salt spray and moisture, and coating adhesion refers to the product's resistance to cracking, peeling, powder and other properties of the coating during processing.

Regarding the salt spray test, it is necessary to understand first whether to evaluate the coating or the zinc layer.

The following is a transcript of a lecture.

Q: Please introduce the salt spray test. Can the 80g zinc layer neutral salt spray test pass 48 hours?

A: The salt spray test we're talking about is one for white rust and one for red rust. The white rust is to evaluate the coating, and the red rust is to evaluate the zinc layer.

If this 48 hours is to do white rust, it is to evaluate the coating, that is, to evaluate this layer of passivation film and fingerprint resistant film. In general, the chromium-free passivation and fingerprint resistance used now can reach 48 hours.

If the hot galvanized plate has no post-treatment coating, it is put into the salt spray box, and the white rust comes out in a few hours. The white rust is used to evaluate the post-treatment film. Red rust is the evaluation of the zinc layer, 80g generally 48 hours to ensure that it can be achieved.

The evaluation of coating adhesion is mainly through the simple evaluation of coating adhesion folding test

Grade 1: No zinc layer falling off, smooth bending surface, no obvious cracks.

Level 2: Pinch it with tape, tape or bending surface shows granular dezincification, bending surface has obvious cracks, and the hand feels rough, that is, about level 2.

Level 3: The zinc layer is clearly seen to fall off, which is level 3.

Users often encounter dezincification problems when using hot-dip galvanized products. Dezincification may be the cause of poor adhesion of zinc layer, and may also be the cause of too small abrasive gap and poor finish. If the zinc layer has poor adhesion, it is usually flaky. If the zinc layer falls off like there are burrs, this is due to the influence of the mold. Therefore, for the specific zinc layer shedding, we need to analyze specific problems. On the one hand, it is necessary to ensure the normal hot-dip galvanizing process, and the user's side is mainly the reasonable adjustment of the mold, including the gap and finish.

3. Other performance indicators

None of the tests closely matched actual use. Other important performance is the surface quality, such as the surface quality of the exterior plate of the automobile and the exterior plate of home appliances. For the automotive industry, the surface roughness control of steel plates is also very important.

Regarding the surface quality of hot-dip galvanized products, such as FC, FB or FD, there are also O3, O4 or O5 plates.

FB is allowed to have small corrosion spots, dark spots, scars, small chromic acid passivation processing defects and small zinc particles;

FC should not have corrosion points, but there should be slight indentation, scratches, zinc flow ripple marks, and slight chromic acid passivation defects in a small range, and the other side should at least maintain the surface of FB;

The better side of FD must be further limited to the defects, that is, it cannot affect the appearance quality after painting, and there should be a uniform and good coating, and the other side should at least maintain the FB surface.

For the definition of surface quality, a few words can not actually be completely explained, the best is not to use directly in different use processes, to verify first.

The automotive industry has a very strict requirement that it must be verified first.

In addition, there are some instructions, such as for alloyed products or ordinary hot-dip galvanized products, there are also cut and uncut edges, and the edge of the uncut strip steel is allowed to have small zinc layer cracks and white edges.