New national standard for galvanized sheets GB-T/2518-2008
1 Scope
This standard specifies the definition, classification and codes, dimensions, appearance, weight and allowable deviations, technical requirements, experimental methods, inspection rules, packaging, marking and Quality certificate, etc.
This standard applies to continuous hot-dip galvanized ordinary grade, mechanical engagement grade, stamping grade (grade 03, 04, 05, 06), structural grade steel plates and steel strips with a width of not less than 600mm and a nominal thickness of 0.20 mm ~5.0 mm.
Continuous hot-dip galvanized steel sheets and steel strips are obtained by hot-dip plating on a continuous production line by immersing cold-rolled steel strips or hot-rolled pickled steel strips in a plating bath with a zinc content (mass fraction) of not less than 98%. Zinc steel plate and steel strip.
2 categories
Classification and code of zinc layer surface structure and smooth surface
Normal zinc plating N
During the normal solidification process of the zinc layer, the zinc grains grow freely to form a coating with obvious zinc flower morphology.
Small zinc flower coating M
During the solidification process of the zinc layer, the zinc grains are artificially restricted to form the tiniest possible zinc flower coating.
No zinc flower coating F
By adjusting the chemical composition of the plating solution, a coating with a uniform surface without visible spangles is obtained.
Zinc-iron alloy coating ZF
The steel strip after passing through the galvanizing bath is heat treated so that the entire coating forms an alloy layer of zinc and iron. This coating has a dark gray appearance with no metallic luster and is easily powdered during the violent forming process. It is suitable for use in addition to general A coating that can be painted directly without further processing other than cleaning.
Differential thickness coating +S
For both sides of galvanized steel sheets, coatings with different zinc layer weights are required.
finishing
Finishing is a cold rolling process with slight deformation on galvanized steel sheets for one or more of the following purposes.
Classification and code of zinc layer surface structure and smooth surface
Normal surface FA Higher surface FB Advanced surface FC
3 Classification and code of surface treatment
Passivation C
The passivation treatment of the galvanized layer can reduce the occurrence of fold rust (white rust) under humid temperature storage and transportation conditions. However, the anti-corrosion properties of this chemical treatment are limited and, moreover, hinder the adhesion of most coatings. This treatment is generally not used in zinc-iron alloy coatings. In addition to the smooth surface, as a routine, manufacturers perform passivation treatment on other types of zinc coatings.
Oil O
Oiling can reduce the corrosion of steel plates under humid storage and transportation conditions. Applying oil to passivated steel plates and steel strips will further reduce corrosion under humid storage conditions. The oil layer should be removable with a degreasing agent that will not damage the zinc layer.
Lacquer seal L
By applying an extremely thin transparent organic coating film, an additional protection against corrosion and, in particular, fingerprint resistance is provided. Improves lubricity during molding and serves as an adhesive base for subsequent coatings.
Phosphate P
Through phosphating treatment, galvanized steel sheets with various coating types can be coated without further treatment except normal cleaning. This treatment can improve the adhesion and anti-corrosion properties of the coating and reduce the risk of corrosion during storage and transportation. After phosphating, it can be used with suitable lubricant to improve the molding performance.
Do not process U
Only if the orderer makes a request not to process and is responsible for this, the steel plates and steel strips supplied in accordance with this standard may not be passivated, oiled, painted, sealed, phosphated or other surface treatments.
