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Aluminum Coated Steel PowerPoint PPT Presentation


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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 - PowerPoint PPT Presentation

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Aluminum Coated Steel

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Aluminum Coated Steel


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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


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Aluminized Coated Steel

  • Hot Dipped (continuous or batch)

  • Electroplated

  • Thermal Spraying

  • Powder Coating with Fusion

  • Diffusion Coating

We will consider these


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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)


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Hot Dipped Aluminum Coating

Type 2

Al

Iron-Aluminide

Fe

ASM Handbook , Vol 1, 1990


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Aluminum Coated

Automotive exhaust systems

Typical Applications of Coated Steels


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Diffusion Aluminizing

Pure Aluminum Coating + Diffusion Heat Treatment

(Applied by Any of the previous processes)(Furnace Heat Treatment)


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AWS Welding Handbook


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Welding Hot Dipped Aluminum Coated Steel


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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


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AWS Welding Handbook


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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


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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


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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


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Welding Diffusion Aluminized Metals


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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