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: 13
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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Welcome, future engineers and artisans! Look around our community in Ghana. From the burglar-proof bars that keep our homes safe, the gates to our compounds, the metal frames for market stalls, to the repair of our trotros and taxis, welding is everywhere. Electric arc welding is one of the most common and important skills in the metal fabrication industry. It is a powerful process that allows us to join pieces of metal together permanently, creating strong and useful products. Understanding the tools and equipment involved is the first and most critical step to becoming a safe and skilled welder.
What is Electric Arc Welding?
Imagine creating a small, controlled bolt of lightning. That's essentially what electric arc welding is! It is a process that uses electricity to create an electric arc (a bright, hot spark) between a metal stick called an electrode and the metal pieces you want to join (the base metal). This arc is incredibly hot (over 3,000°C), hot enough to melt both the electrode and the edges of the base metal. The molten metals mix together, and as they cool, they form a single, strong piece of metal. This solid joint is called a weld.
We will now explore the specific tools and equipment needed to perform this process safely and effectively. We can group them into three main categories. A. Welding Machine and Its Accessories
These are the core components that generate and control the electric arc. Welding Machine (Power Source) Description: A heavy metal box, often with dials, switches, and connection points for cables. They can be large (transformer type) or smaller and more portable (inverter type). Function: This is the heart of the setup. Its main job is to take the regular electricity from the wall socket (high voltage, low current) and convert it into the type of electricity needed for welding (low voltage, very high current/amperage). This high current is what creates the powerful arc. The dials are used to adjust the amperage based on the thickness of the metal being welded. Ghanaian Context: You see these in every roadside welding shop. The big, red or blue ones are usually transformer types, common in established shops. Electrode Holder (or "Stinger") Description: An insulated handle with a clamp-like jaw mechanism at the end. It is connected to the welding machine by a thick cable. Function: The welder holds this tool to grip the welding electrode firmly. It safely conducts the welding current from the cable to the electrode, allowing the welder to control the position of the arc. The insulation on the handle protects the welder from electric shock. Earth Clamp (or Ground Clamp) Description: A sturdy, spring-loaded metal clamp, similar to a car battery jumper clamp. It is also connected to the welding machine by a thick cable. Function: To complete the electrical circuit. The earth clamp is attached directly to the metal workpiece or the metal welding table. Without it, the electric arc cannot form. It ensures that the electricity flows from the machine, through the electrode holder, across the arc, into the workpiece, and back to the machine through the earth cable. Welding Cables Description: Two thick, flexible copper cables covered in a durable rubber or synthetic insulator. Function: One cable connects the electrode holder to the machine, and the other connects the earth clamp to the machine. They are designed to carry high electrical currents safely without overheating. Electrodes (or Welding Rods) Description: Metal rods covered with a special chemical coating called flux. They come in various diameters and types for different metals and welding positions. Function: The electrode is the consumable part of the process. It conducts the electricity to create the arc and also melts to provide filler metal to the joint, making it stronger. The flux coating melts and forms a protective gas shield around the weld to keep oxygen from the air out (which would weaken the weld). It also forms a solid layer on top of the cooling weld called slag, which needs to be cleaned off later. B. Hand Tools