What are the requirements for galvanized coil property performance?
1. Mechanical performance index
The first is the mechanical properties of hot galvanized steel coil
.The mechanical properties can be defined as steel properties 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, there is a phenomenon of aging, then press once aging occurs after a long time, a slip occurs. This is the steel plate after the surface of the orange peel, that is, slip. This is a serious piece of orange peel after a piece of stamping. The normal countermeasures are to ensure the production process, such as ensuring smooth elongation, yield platform to eliminate the steel, and, steel users recommendations against on these steel problem is to use them out as soon as possible to prevent
2. Zinc layer performance index
Hot-dip galvanized steel, the most important property performance is the coating performance, mainly refers to the corrosion resistance of the coating, coating adhesion properties. Corrosion resistance, including resistance to salt spray and moisture and other properties, coating adhesion refers to the product resistance in the processing of the coating cracking, peeling, powder and other properties.
On the salt spray test, we must first understand, is to evaluate the coating or evaluation of zinc layer.
Q: Please tell us about salt spray test, 80g zinc layer neutral salt spray test can pass 48 hours?
A: We said that the salt spray test is to do a white rust or one is to do red rust. Do white rust is to evaluate the coating, do red rust is to evaluate the zinc layer. If this 48 hour is to do white rust, it is the evaluation of the coating, that is, this layer of passive film and fingerprint-resistant film evaluation. In general, now with the chrome-free passivization and fingerprints can reach 48 hours. Galvanized sheet without post-treatment coating is then put inside the box salt spray, white rust came out a few hours, the treated film was evaluated after the white rust, the corrosion resistance of the zinc layer to be evaluated, it is done red rust. Red rust is the evaluation of zinc layer, 80g generally 48 hours to ensure that can be achieved.
The evaluation of the adhesion of the zinc coating was mainly evaluated by a coating adhesion test.
These two pictures are specific ways of folding test, a piece of steel sheet creases 180 °, in the case of 0T, looking at the surface where the bend classification.
Level 1: no zinc layer off, curved surface smooth, no obvious cracks.
Level 2: with a tape pinch, tape or curved surface shows a grain dezincification, curved surface with a clear crack, hand touch a rough feeling, that is, in the 2 or so.
Level 3: apparent zinc layer off, it is 3 level.
Users in the use of hot-dip galvanized products, often encounter dezincification problems. Dezincification may be the reason for the poor adhesion of the zinc layer, or it may be the reason that the abrasive gap is too small and the finish is poor. If the adhesion of the zinc layer is poor, it is usually sheet off. If it is the same as burrs off the zinc layer, which is caused due to the mold. So for specific zinc layer off, we detailed analysis of specific issues. Countermeasures on the one hand is to ensure normal hot dip galvanizing process, the user is done mainly mold of reasonable adjustments, including clearance, finish and so on.
3. Other performance indicators
There is no test capable of very fit actual usage. Other important properties of galvanized steel coil, is as well as, surface quality. Such as automobiles outer steel plate and appliances plate is looking the surface quality as the very important factor. For the automotive industry, steel surface roughness control is also very important.
On the surface quality of hot-dip galvanized steel products, such as FC, FB or FD, there are O3, O4 or O5 sheet.
FB allow a small corrosion spots, dark spots, with marks, small chromate passivation of defects and small zinc particles;
FC is not subject to corrosion, but in a small range to allow the existence of a slight indentation, scratches, zinc flow wave marks, slight chromated passivation defects, the other side should be at least to maintain the FB surface;
FD is a better side must be further restrictions on the lack of that can not affect the appearance of the painted quality, and should have a uniform and good coating, the other side should be at least to maintain the FB surface.
For the definition of the surface quality, in fact, a few words can not fully be described, is preferably not directly used in a different course, first be verified.
There are also some explanations, such as the alloying steel products or ordinary hot-dip galvanized steel products, there are still trimming and non-trimming difference. No trimming steel strip allows the existence of tiny zinc cracks and white side in the edge.