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Ultragal®

Applications

With its ability to limit repeated waviness during deformation, combined with the proven qualities of Extragal® (surface quality, corrosion protection), Ultragal® is a coating specifically recommended for visible part applications in the automotive sector.

With the Ultragal® production process, waviness in steel products can be controlled both before and after forming. In an optimized painting process configuration, Ultragal® lends the painted part very high-quality paint appearance (even better than a standard galvanized substrate). With waviness reduced to a very low value, Ultragal® also contributes to enhanced reproducibility of paint appearance quality.

 

Technical characteristics

Surface appearance

The crystal structure of Ultragal® is not visible to the naked eye and the product offers optimum surface quality before and after painting. Control of the operating drive factors amplifying waviness at the secondary processing stage, in particular during drawing, further enhances paint appearance.

We offer a waviness guarantee expressed as Wa 0.8 mm after drawing, which ensures product quality.

 

Hardness
Ultragal® coating is relatively ductile, which reduces the risk of coating damage in the drawing tool.

Morphology

Surface appearance of Ultragal® coating (scanning electron micrograph)

Cross-section of Ultragal® coating

Coating thickness

Unless otherwise specified, the standard coating thicknesses offered for Ultragal® (per side, measured at 3 points) are as follows:

Similar standard

Minimum

(2 sides)

(g/m²)

Minimum

(per side)

µm          g/m²

Maximum

(per side)

µm          g/m²

Z100

100

  7.0          50

  9.0          65

Z140

140

10.0          70

12.0          85

Other coating thicknesses may be considered. Please consult us.

Coating process

Ultragal® coating is obtained by hot dip galvanizing (the steel sheet is fed through a bath of molten zinc) of a steel substrate which can be selected from most of our cold rolled steels.
The Ultragal® manufacturing process involves adaptations at all process stages, from steelworks to skin pass. It is subject to rigorous control and inspection. These measures produce an exceptional galvanized coating with surface optimized for top-quality paint appearance in automotive body parts.

Typical layout of a galvanizing line

Recommendations for use and secondary processing

Corrosion
Ultragal® coating provides excellent corrosion protection, even in the event of damage (impact, scratches, gravel impingement), due to the electro-chemical behavior of the Fe-Zn galvanic couple, in which the zinc acts as a sacrificial anode.

Drawing

Ultragal® offers drawing quality equivalent to that of Extragal®, the galvanized steel product with pure zinc coating on both sides. Ultragal® has a friction coefficient of approximately 0.10 to 0.14 (with standard oiling), which lends it excellent drawability. The type and quantity of lubricant and the surface texture are obviously of prime importance during sheet-tool contact; any comparison of coatings must be carried out under identical conditions. Furthermore, the ductility of pure zinc limits the risk of powdering in the drawing tools.

Welding

Ultragal® coated products offer a welding range suited to industrial requirements. The welding process, and in particular electrode life (typically 400 spot welds without current adjustment according to ISO standard 18278-2 on a 0.8 mm substrate), can be optimized by fine-tuning electrode composition, geometry and current adjustment frequency as well as welding parameters (current type and intensity, current incrementation, joining pressure, cycle time).
ArcelorMittal specialist teams are available to assist customers in optimizing the welding process.

Adhesive bonding
Ultragal®
coating has good adhesive bonding behavior, good adhesion to the coating, good adhesion of the coating to the metal and good cohesion of the coating.
The most significant parameters determining bond quality remain the type of adhesive, the joining conditions, the nature of the protective oil, and any chemical treatments that may have been performed.

Surface treatment
Ultragal® can be phosphated and painted at the user's premises using current trication processes (Zn, Ni, Mn). Alternative "environmentally-friendly" (particularly nickel-free) treatment processes are being developed; however any change in the bodywork surface treatment process must undergo prior validation.

Recommendations:

  • Alkali degreasing to remove any organic residues and oxides present on the surface;
  • F- ions should be present in the bath to neutralize any Al3+ ions that may reduce its activity.

ArcelorMittal can provide specialized technical assistance regarding these issues.

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