Lesson Notes By Weeks and Term v4 - SHS 1
WELDING TECHNOLOGY
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WELDING TECHNOLOGY
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Subject: Applied Technology
Class: SHS 1
Term: 2nd Term
Week: 10
Grade code: 1.4.2.LI.2
Strand code: 4
Sub-strand code: 2
Content standard code: 1.4.2.CS.1
Indicator code: 1.4.2.LI.2
Theme: METAL TECHNOLOGY
Subtheme: WELDING TECHNOLOGY
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Welding is a skill we see in action all around us in Ghana. From the strong metal gates that protect our homes and schools, the burglar-proof bars on our windows, the frames of market stalls, to the repair of vehicle parts and farm tools, welding is essential. Understanding the tools and equipment for electric arc welding is the first step towards learning this valuable trade, which offers many opportunities for entrepreneurship and careers in construction, manufacturing, and art. This lesson will introduce you to the fundamental tools you need to know, with a strong focus on safety.
What is Electric Arc Welding? Electric arc welding is a process that uses electricity to create an extremely hot electric arc (like a controlled, miniature lightning bolt) between a welding electrode and the metal pieces to be joined. This intense heat melts the edges of the metal parts and the electrode. The molten metals mix together and, as they cool, they solidify to form a strong, permanent joint.
To understand how the equipment works, think of a simple electrical circuit. For electricity to flow and create the arc, there must be a complete, unbroken path. A. The Core Welding Machine and Components
These are the essential parts that generate and control the electric arc. Welding Machine (Power Source): What it is: This is the "engine" of the welding setup. It's a transformer or an inverter that takes high-voltage, low-current electricity from the mains (like a wall socket) and converts it into low-voltage, high-current electricity suitable for welding. Function: It provides the power needed to create and sustain the welding arc. It has controls to adjust the amperage (the "heat" or intensity of the arc) depending on the thickness of the metal and the type of electrode being used. In Ghana, you will see both older, heavy transformer types and newer, lighter inverter types. Electrode Holder (or "Stinger"): What it is: An insulated handle with a clamp (jaws) at the end. It is connected to the welding machine by a heavy electrical cable. Function: The welder holds this tool to grip the welding electrode firmly. It conducts the welding current from the cable to the electrode, allowing the welder to direct the arc precisely where it is needed. The insulation protects the welder from electric shock. Ground Clamp (or "Earth Clamp"): What it is: A sturdy metal clamp, usually made of copper or brass, connected to the welding machine by the other heavy electrical cable. Function: This clamp is attached directly to the workpiece (the metal being welded) or to the metal welding table. Its job is to complete the electrical circuit. Without the ground clamp properly attached, the circuit is open, and no arc can be formed. It ensures that the current flows from the machine, through the electrode holder, across the arc, into the workpiece, and back to the machine. Welding Cables (or "Leads"): What it is: Two thick, insulated copper cables. Function: One cable connects the electrode holder to the machine, and the other connects the ground clamp to the machine. They must be thick to carry the high current without overheating and well-insulated to prevent electric shock.
*A simple diagram showing the connection: Power Source -> Electrode Cable -> Electrode Holder -> Electrode -> Arc -> Workpiece -> Ground Clamp -> Ground Cable -> Power Source.* B. The Consumable: Welding Electrode What it is: A metal rod covered with a special chemical coating called flux. Function: The electrode has two jobs: Filler Metal: The inner metal rod melts in the arc and adds material to the joint, filling the gap and strengthening the weld. Flux Shielding: The flux coating burns and vaporizes in the arc, creating a protective cloud of gas. This gas shield pushes the surrounding air (oxygen and nitrogen) away from the molten weld pool. This is crucial because if oxygen gets into the molten metal, the weld will become weak, porous, and brittle. The burnt flux also forms a hard, protective layer on top of the cooling weld called slag, which is chipped off later. Ghanaian Context Example: The most common electrode you will see in local workshops is the E6013. It is a general-purpose rod used for mild steel projects like making gates and burglar-proof bars. C. Personal Protective Equipment (PPE) - SAFETY FIRST!