Lesson Notes By Weeks and Term v4 - SHS 3
WELDING TECHNOLOGY
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WELDING TECHNOLOGY
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Subject: Applied Technology
Class: SHS 3
Term: 1st Term
Week: 14
Grade code: 3.2.2.LI.5
Strand code: 2
Sub-strand code: 2
Content standard code: 3.2.2.CS.1
Indicator code: 3.2.2.LI.5
Theme: METAL TECHNOLOGY
Subtheme: WELDING TECHNOLOGY
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Welcome, future engineers and technicians! We have all seen the local "akokora" welder in our communities using stick welding to create strong metal gates, burglar-proof windows, and repair broken metal parts. That method, Shielded Metal Arc Welding (SMAW), is very useful. However, in modern industry, from car manufacturing at Kantanka to constructing large oil storage tanks in Tema, more advanced and specialised welding techniques are needed. These "special" techniques offer greater speed, precision, cleaner results, and the ability to join different types of metals like aluminium and stainless steel.
Recap: What is Basic Welding? The welding you are most familiar with is likely Shielded Metal Arc Welding (SMAW), or "stick welding". How it works: An electric arc is formed between a consumable, flux-covered electrode (the "stick") and the metal workpiece. The heat melts both the electrode and the base metal, fusing them. The flux coating burns to create a shielding gas and slag, protecting the weld from air contamination. Common Use: General fabrication, repairs, construction (gates, burglar proofs). It is versatile and good for outdoor work. What Makes a Welding Technique "Special"? Special welding techniques are processes developed for specific needs that basic SMAW cannot easily meet. These needs include: Higher Speed: For mass production (e.g., making car parts). Greater Precision: For delicate or complex joints. Joining Different Materials: Welding aluminium, stainless steel, or very thin sheets. Cleaner Welds: Requiring little to no clean-up after welding. Automation: Using robots for repetitive tasks.
Let's explore three key special techniques.
Technique 1: Gas Metal Arc Welding (GMAW / MIG) Full Name: Gas Metal Arc Welding. Often called MIG (Metal Inert Gas) welding. Working Principle: GMAW is like a semi-automatic version of stick welding. Instead of a short stick that needs constant replacement, GMAW uses a continuously fed wire electrode from a spool. This wire passes through a "welding gun." When the trigger is pulled, the wire feeds out, an electric arc is created, and a shielding gas (like Argon or Carbon Dioxide) flows from a cylinder through the gun to protect the molten weld pool from the air.
*Imagine a glue gun, but instead of a glue stick, it feeds a metal wire, and instead of just heat, it uses an electric arc and a protective gas.* Key Equipment: Welding Power Source Wire Feeder Unit (feeds the wire from a spool) Welding Gun (looks like a pistol with a trigger) Shielding Gas Cylinder and Regulator Ground Clamp Advantages: Fast: Much faster than stick welding because there is no need to stop and change electrodes. Clean: Produces very little slag, meaning less time spent chipping and grinding after welding. Easy to Learn: The basic technique is relatively easy for beginners to pick up. Versatile: Can weld thin and thick materials, including steel, stainless steel, and aluminium. Disadvantages: Portability: The gas cylinder and wire feeder make it less portable than a simple SMAW setup. Sensitivity to Wind: The shielding gas can be blown away by wind, making it difficult to use outdoors without protection. Requires Clean Metal: The workpiece must be very clean (free of rust, paint, and oil) for a good weld. Ghanaian Context Application: Used in modern fabrication shops in cities like Accra and Kumasi for making high-quality furniture, vehicle exhaust systems, and light structural frames. It is a major step-up in productivity from traditional stick welding.