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Aluminum Coated Steel. Resistance Welding. Learning Activities View Slides; Read Notes, Listen to lecture Do on-line workbook. Lesson Objectives When you finish this lesson you will understand:. Keywords. Aluminized Coated Steel. Hot Dipped (continuous or batch) Electroplated
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Resistance Welding • Learning Activities • View Slides; • Read Notes, • Listen to lecture • Do on-line workbook • Lesson Objectives • When you finish this lesson you will understand: Keywords
Aluminized Coated Steel • Hot Dipped (continuous or batch) • Electroplated • Thermal Spraying • Powder Coating with Fusion • Diffusion Coating We will consider these
Hot Dipped Aluminum Coating Type 1: Al - 8% Si (Oxidation Resistance Up to 1200F - 649C)- Reduced Formability T1-40 = 0.40 oz/ sq ft (0.001 inch thick) T1-25 = 0.25 oz/ sq ft (0.0005 inch thick) Type 2: Commercially Pure Al (Atmospheric Resistance at RT) Lower Electrical Resistance 0.75 oz/ sq ft (0.002 inch thick)
Hot Dipped Aluminum Coating Type 2 Al Iron-Aluminide Fe ASM Handbook , Vol 1, 1990
Aluminum Coated Automotive exhaust systems Typical Applications of Coated Steels
Diffusion Aluminizing Pure Aluminum Coating + Diffusion Heat Treatment (Applied by Any of the previous processes) (Furnace Heat Treatment)
Welding Aluminum Coated Steels Spot Welding • Welding Current 20-50% higher than uncoated steel • Electrode Force 20-50% higher than uncoated Steel • Weld Time 40-60% longer than uncoated steel • Electrode Dressing somewhat more frequent than Galvanized Steel • Class II Truncated Cone Electrodes have been successful • More electrode indentation with type 2 Aluminized Sheet because it has lower resistance than type 1 Aluminized & generally Thicker Coating
Welding Aluminum Coated Steels Projection Welding Benefit of Projection Welding: Reduces need for frequent electrode dressing • Type 1 coating • Recommend slightly larger projects than for Uncoated steel • Normally flat class II Electrodes Recommended
Welding Aluminum Coated Steels Seam Welding • AWS Recommendations: • 20 - 50% greater welding current than bare steel • 20 - 50% greater pressure than bare steel • Class II wheels wit Type 1 Material • Pick up of Aluminum on Wheel must be countered • Knurled Drive Wheel • Power Brushes • Large amount of flood water • Mash seam welding is sometimes hampered by the refractory Oxide present AWS Welding Handbook
Welding Aluminum Coated Steels ERW & High-Frequency Seam Welding • Both 60 Hz and High Frequency Welds can be made • Edges must be square & free of Aluminum to prevent Aluminum Oxide, thus Centerline defects
Welding Diffusion Aluminized Metals Close to the same as welding uncoated steel with one exception noted below Aluminum Above 1% in the Weld Can Significantly Reduce Ductility and Cause Embrittlement