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: 13
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, students. In our communities, from the burglar-proof bars on our windows to the metal gates at our school entrance, and even the cars we ride in, we see the work of welders everywhere. So far, we have mostly learned about Shielded Metal Arc Welding (SMAW), the common "stick welding" we see at local workshops. However, in modern manufacturing and design, industries require faster, cleaner, and more precise ways to join metals. These methods are called "special welding techniques." Understanding these techniques is crucial for anyone interested in engineering, manufacturing, or even starting a modern fabrication business in Ghana.
In this section, we will delve into the details of specific welding techniques that are considered "special" because they are used for specific applications in industrial design and manufacturing. A. Gas Metal Arc Welding (GMAW) or MIG Welding
GMAW is one of the most common industrial welding processes. You may hear it called by its popular name, MIG (Metal Inert Gas) welding.
Working Principle: Think of a MIG welder as a "hot glue gun for metal." Instead of a glue stick, it uses a continuous spool of metal wire, and instead of just heat, it uses a powerful electric arc.
Here is the step-by-step process: The Wire Electrode: A thin metal wire is fed continuously from a spool, through a flexible tube, and out of the nozzle of the welding gun. This wire is the electrode and also acts as the filler metal. The Electric Arc: The welder pulls the trigger on the gun. This does two things: it starts feeding the wire and it sends an electric current through the wire. When the wire touches the base metal, an electric arc is created. This arc is extremely hot (thousands of degrees Celsius) and it melts both the tip of the wire and the base metal. The Shielding Gas: At the same time, an inert or active gas (like Argon or a Carbon Dioxide mix) flows out of the nozzle around the wire. This shielding gas forms a protective bubble around the molten weld pool, preventing oxygen and nitrogen from the air from contaminating the weld, which would make it weak and brittle. The Weld Bead: The molten wire and base metal mix together in a small pool. As the welder moves the gun along the joint, this pool cools and solidifies, forming a strong, continuous weld bead.