Lesson Notes By Weeks and Term v4 - SHS 2
WELDING TECHNOLOGY
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WELDING TECHNOLOGY
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Subject: Applied Technology
Class: SHS 2
Term: 1st Term
Week: 15
Grade code: 2.2.2.LI.3
Strand code: 2
Sub-strand code: 2
Content standard code: 2.2.2.CS.1
Indicator code: 2.2.2.LI.3
Theme: METAL TECHNOLOGY
Subtheme: WELDING TECHNOLOGY
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Welcome, students! Today, we are diving into a very practical and essential skill in metalwork. Before a welder can join two pieces of metal to create something useful, those pieces must first be cut and shaped accurately. Think about the local artisan in your community who makes metal trunks ('chop boxes'), gates, coal pots, or even the auto body specialist ('sprayer') who repairs the body of a 'trotro'. Their work begins not with welding, but with marking, cutting, and bending flat sheets of metal. This lesson will give you the foundational skills to do just that. Mastering these operations is the first step to becoming a skilled fabricator or welder.
This section breaks down the core knowledge you need. We will cover the materials, the tools, and the step-by-step processes. A. Sheet Metal: Types and Selection
Sheet metal is simply metal that has been formed into thin, flat pieces. The thickness is often referred to by its gauge – the higher the gauge number, the thinner the metal. For our work in SHS, we will mostly use gauges between 24 (thin) and 18 (thicker).
| Metal Type | Properties | Common Ghanaian Uses | How to Identify | | :--- | :--- | :--- | :--- | | Mild Steel | Strong, affordable, prone to rust if not coated. | Car bodies (trotros, taxis), gates, burglar proofs, metal trunks. | Greyish, magnetic, will rust quickly if left in the open. | | Galvanized Iron (GI) | Mild steel coated with zinc to prevent rust. | Roofing sheets, water tanks ('polytank' stands), buckets, coal pots. | Dull, slightly mottled or crystalline silver-grey surface. Magnetic. | | Aluminium | Lightweight, corrosion-resistant, soft, good conductor of heat. | Cooking pots ('dadesen'), roofing sheets (Aluzinc), window frames. | Bright, silvery-white colour. Very light compared to steel. Not magnetic. |
Selection Criteria: For most general workshop projects like making a small toolbox or tray, mild steel (gauge 22 or 20) is an excellent and affordable choice. B. The Fabrication Process: An Overview All sheet metal projects follow a logical sequence: Marking Out: Transferring dimensions from a drawing onto the metal sheet. Cutting: Separating the desired shape from the main sheet. Bending/Forming: Shaping the flat cutout into a 3D object. Joining: Assembling the parts (e.g., by welding, riveting, or seaming).