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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

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Aluminum Coated Steel

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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

  • 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)


AWS Welding Handbook


Welding Hot Dipped Aluminum Coated Steel


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


AWS Welding Handbook


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


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


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