UPI.GalXC Technical Bulletin

Product Attributes

UPI.GalXC is a hot dipped galvanized sheet product that has a coating weight under G-30. It is temper passed to provide an ultra smooth surface that has an attractive, "out of this world", look and feel. Not only does the product have superior surface quality, but UPI.GalXC's sheet or coil flatness is world class. UPI.GalXC does not discolor or absorb finger prints when touched, and has excellent conductive properties. Formability characteristics have been developed by a team of our technical experts to meet the critical demands of the computer component and chassis markets. As an added bonus, our new product has at least 1.5 times the corrosion resistance of ASTM A591 electro-galvanized steel. It will be an economical alternative to current products supplying the high tech industry.

Market Focus

UPI.GalXC was developed to meet the critical needs of computer and electronic chassis and cabinet applications. Computer companies' procurement engineers, working with USS-POSCO's technical engineers, have determined that the product attributes needed to meet these applications are: formability, consistency in appearance, conductivity, resistance to "finger printing", resistance to corrosion, and paintability. UPI.GalXC's features meet these market requirements. In addition, many end users have asked that the producer be ISO 9000 certified, and USS-POSCO has just passed our third surveillance audit maintaining ISO 9002 compliance.

Formability

The formability characteristics of UPI.GalXC have been developed by a team of metallurgical engineers. the product can be subjected to moderate drawing, hole piercing and expansion, bending and embossing without cracking of the steel or flaking of the zinc coating. UPI.GalXC has formability characteristics equivalent to ASTM A653 Forming Steel (FS) Type A. It can be used for all applications from roll forming and bending, to moderate drawing, hole piercing and expansion. Direct contact with USS-POSCO's metallurgical engineers in new applications of UPI.GalXC to forming can be helpful and is recommended.

Weldability

UPI.GalXC exhibits projection and spot welding characteristics similar to electro-galvanized sheets. See Attachment 2 for specific recommendations.

Surface Appearance

UPI.GalXC has an attractive, high tech appearance. Because the product is temper mill processed, it has a very uniform surface finish within each coil, between coils, and between orders.

Conductivity

UPI.GalXC exhibits extremely low resistivities (less than 0.10 ohms/ sq. in.). This will provide low impedance bonds between adjacent metal components and connectors. The purpose of low impedance bonding is to provide electromagnetic shielding and low impedance paths for electrostatic discharge currents. UPI.GalXC may provide superior conductivity ratings compared to competing products.

Corrosion Resistance

UPI.GalXC has an ultra light coating of metallic hot-dipped zinc that provides superior corrosion resistance when compared to flash coated products like ASTM A591 electro-galvanized steel. Until recently, technology was unavailable to supply hot-dip galvanized product with coating this light.

Corrosion protection of zinc coated products is in direct proportion to the thickness of the zinc coating, the zinc coating is at least 1.5 times thicker than ASTM A591 electro-galvanized steel product and, therefore, provides 1.5 times more corrosion protection in equivalent environments.

Because the zinc coating protects the steel by acting as a sacrificial anode, any exposed parts of the steel (such as cut edges from shearing or punching operations) are also protected longer by the thicker zinc coating.

Non "Finger Printing"

UPI.GalXC's metallic zinc coating is non-porous and inherently resistant to "finger printing". Unlike some competitive materials, UPI.GalXC has no insulating coatings that detract from the metallic steel and zinc coating conductivity; yet its surface is inherently resistant to absorbing any oil (including finger print residue) that may be present during the fabrication process. Any oils that may be deposited on the surface can be easily removed by normal cleaning processes.

Good Paintability

When chemical treatment of the galvanized surface is required, USS-POSCO uses a chemical treatment supplied by Oakite, designated "Oakite F-2". Many of our customers have found paint systems, including electrostatically applied epoxy based paints, can be applied directly over the chemical treatment film. Oakite also recommends pre-cleaning of parts with a strong, hot alkaline cleaner before paint application. The pre-cleaning removes any soils that have accumulated in fabrication and activates the surface for best paint retention. Oakite markets a proprietary cleaner, designated "Oakite STC", where pre-cleaning is indicated. Obviously, other commercially available cleaning agents can also be considered.

UPI.GalXC can be provided with or without the chemical treatment film. Chemical treatment provides in-process protection against white rust formation from humidity in the air, and is available at no extra charge to our customers.

ISO 9002 Certification

USS-POSCO Industries received certification to the ISO 9002 Standard for quality assurance of production and manufacturing, effective 4/10/96. UPI achieved certification of its' Quality System - QUEST, through ABS Quality Evaluations, Inc., a RAB certified ISO 9000 registrar. This certification confirms UPI's commitment to total quality satisfaction of its customer's requirements.

Attachment 1: Formability Considerations

Actions to Promote Good Surface Quality of the Parts

For fabricators currently using electro-galvanized sheets, changes to forming fabrication parameters will be minimal. Relative to other hot-dipped galvanized sheets, extra low carbon steel sheets exhibit very good substrate properties. UPI.GalXC is an extra low carbon steel.

  1. Clean feed rolls on blanking presses to eliminate dirt that might otherwise be rolled into the coating during blanking.
  2. Minimize blanking burrs.
  3. Float blanks into the stacking box on an air cushion, or drop vertically.
  4. Protect lifts of UPI.GalXC blanks from any sources of dirt immediately after they are removed from the blanker.
  5. Steam clean all dies in the press line before running UPI.GalXC panels.
  6. Pick blanks off the lift and place into the draw die using vacuum cup lifter to prevent damage from any blank edge burrs.
  7. Spray blanks with drawing compound if lubrication is required at the draw die (re-circulating systems and rollers can deposit dirt on the strip).
  8. Clean all tooling on a regular basis as determined by SPC methods.
  9. Avoid porous cast iron tool surfaces which can contribute to powdering, flaking and buildup in dies.
  10. Use improved die cleaning procedures, avoid rags or cloth gloves.
  11. Avoid metal finishing on formed UPI.GalXC panels because it reduces corrosion protection and upsets surface appearance.

Attachment 2: Welding Recommendations

General Comments: Hot-dipped galvanized sheets have been joined by welding processes for many years by modifying practices used for bare steel sheets. Because of the light zinc coating weight applied to UPI.GalXC, the welding characteristics are closer to those of electro-galvanized and bare cold rolled sheets.

Process Recommendation: Where a welding process must be used in fabrication, projection welding is the preferred welding process for joining parts. The direct spot welding process may also by used, series spot welding is not recommended because the shunting circuit results in excessive electrode heating.

Electrode Recommendation: For best surface appearance, use the RWMA Class 1 electrode. For best electrode life, use the RWMA Class 2 electrode. For the spot welding process, a truncated cone with an included angle of 120 degrees to 140 degrees should be selected. The welding electrodes will require more frequent cleaning than that experienced when welding cold rolled sheet steel. Maintaining an electrode cooling water flow rate of about two-gallons per minute is recommended to minimized cleaning frequency.

Welding Conditions: Using cold rolled sheets as a reference; weld time (cycles) must be increased by 10% or more, electrode force will require about a 5% to 10% increase, and post weld hold time should be increased slightly to insure best surface appearance.

Specific welder setups and more detailed information on welding zinc coated steel can be found in the American Welding Society Welding Handbook, or Volume 6 of the ASM Metals Handbook.

Attachment 3: Corrosion Testing of Low Coating Weight Zinc-Based Coatings
(UPI.GalXC vs. EGL)

Abstract

Sets of UPI.GalXC and electrogalvanized (EGL) panels were tested under salt spray conditions. Panels of UPI.GalXC showed better resistance to the corrosive environment than the panels of electrogalvanized.

Introduction

Samples of UPI.GalXC and electrogalvanized were forwarded to U.S. Steel Technical Center for an evaluation of their corrosion behavior under salt spray testing. The materials were evaluated for metallic coating weight and type, and surface chromium levels. The materials were tested per ASTM B117 Salt Spray Specification.

Discussion

The characteristics and properties of the coatings is given in Table 1 (below). The UPI.GalXC sample has a higher zinc coating and lower chromium coating than the electrogalvanized sample. (reported to be Usiminas EG with chromate from Brazil.)

Photographs of the samples after termination of test at 120 hours (5 days) in the salt fog environment are given in Figure 1. The purpose of this testing was to run all of the panels to a uniform endpoint so that they could be compared directly to one another. Panels are tested in triplicate to reduce possible anomalous behavior due to non-uniformity in either the samples themselves or in the test environment. This very aggressive salt spray test readily shows differences between the materials. The UPI.GalXC panels show some white rusting (zinc corrosion product) along with localized red rusting (iron-based corrosion products.) The electrogalvanized panels shows almost complete red rust coverage. Even with the slightly higher elevated chromium level of 2.1 mg/ft2, the electrogalvanized panel set suffered the most extensive corrosive attack.

Conclusion

Of the materials tested, UPI.GalXC outperformed the electrogalvanized panels in the salt spray corrosion test of 120 hours
(5 days).

Sample Identity and Side
Metallic Coating Weight (g/m2)
Metallic Coating Weight (oz/ft2)
Chromium Level (mg/ft2)
Coating Type
UPI.GalXC 
   Top 
   Bottom
 
32.9 
27.9
 
.108 
.091
1.3
Hot Dipped Galvanized
EGL 
   Top 
   Bottom
 
24.1 
24.0
 
.079 
.079
2.1
Electrogalvanized

 

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