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Aluminum Coated Steel. Resistance Welding Lesson Objectives When you finish this lesson you will understand: Learning Activities 1.View Slides; 2.Read.

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Presentation on theme: "Aluminum Coated Steel. Resistance Welding Lesson Objectives When you finish this lesson you will understand: Learning Activities 1.View Slides; 2.Read."— Presentation transcript:

1 Aluminum Coated Steel

2 Resistance Welding Lesson Objectives When you finish this lesson you will understand: Learning Activities 1.View Slides; 2.Read Notes, 3.Listen to lecture 4.Do on-line workbook Keywords

3 Aluminized Coated Steel Hot Dipped (continuous or batch) Electroplated Thermal Spraying Powder Coating with Fusion Diffusion Coating We will consider these

4 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 ( inch thick) Type 2: Commercially Pure Al (Atmospheric Resistance at RT) Lower Electrical Resistance 0.75 oz/ sq ft (0.002 inch thick)

5 Fe Iron-Aluminide Al ASM Handbook, Vol 1, 1990 Hot Dipped Aluminum Coating Type 2

6 Typical Applications of Coated Steels Aluminum Coated –Automotive exhaust systems

7 Diffusion Aluminizing Pure Aluminum Coating + Diffusion Heat Treatment ( Applied by Any of the previous processes)(Furnace Heat Treatment)

8 AWS Welding Handbook

9 Welding Hot Dipped Aluminum Coated Steel

10 Welding Aluminum Coated Steels 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 Spot Welding

11 AWS Welding Handbook

12 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

13 Welding Aluminum Coated Steels Seam Welding AWS Recommendations: % greater welding current than bare steel % 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

14 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

15 Welding Diffusion Aluminized Metals

16 Aluminum Above 1% in the Weld Can Significantly Reduce Ductility and Cause Embrittlement Welding Diffusion Aluminized Metals Close to the same as welding uncoated steel with one exception noted below


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