Class: Senior Secondary School 2 (SS2 / SSS 2)
Term: Second Term
Week: 1
Age: 16 years
Duration: 45 minutes
Subject: Metal Work
Curriculum Theme: Pre-Vocational Studies
Previous Lesson: .
Topic: Arc Welding
Subject Matter: Meaning of arc welding (joining metals by electric arc), basic types of arc welding (non consumable electrode arc welding, consumable electrode arc welding)

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

Define arc welding.
Identify the principle involved in establishing an electric arc.
State the basic types of arc welding.

Affective Domain:

Appreciate the importance of safety precautions in arc welding.
Show interest in learning different metal joining techniques.

Psychomotor Domain:

Demonstrate the basic steps to establish an electric arc.
Practice simple butt joint welding under supervision.

Work cooperatively with peers during practical sessions.

Reference Materials

The following resources were used in planning this lesson:

Senior Secondary Schools Education Curriculum
State Unified Scheme of Work
Metalwork for Senior Secondary Schools, Book 2.

Instructional Materials

The teacher will teach this lesson with the aid of:

Arc welding machine
Electrodes
Mild steel plates
Welding helmet
Safety gloves
Chipping hammer
Wire brush

Rationale for the Lesson

This lesson helps pupils understand a common method of permanently joining metals, which is essential for fabrication and repairs in various industries. Knowing arc welding provides pupils with a fundamental skill in metalwork and engineering applications.

Prerequisite/Previous Knowledge

Pupils have basic knowledge of different metal joining methods and general workshop safety rules.

Lesson Content/Board Summary

Arc Welding

Meaning of Arc Welding

Arc welding is a process that joins metals by using electricity to create enough heat to melt the base metal and the filler metal (electrode). This forms a molten pool that, upon cooling, solidifies to create a strong joint between the metals.

Principle of Arc Welding

The principle of arc welding involves establishing an electric arc between an electrode and the workpiece. This arc generates intense heat (around 6,500°F or 3,600°C) which melts the edges of the metals to be joined and the electrode, creating a weld pool. As the molten metal cools, it solidifies, forming a strong metallurgical bond.

Basic Types of Arc Welding

The two basic types of arc welding are:

Non-Consumable Electrode Arc Welding: In this type, the electrode does not melt and become part of the weld. An example is Tungsten Inert Gas (TIG) welding, where a separate filler rod is often used.
Consumable Electrode Arc Welding: In this type, the electrode melts and becomes the filler metal for the weld. Examples include Shielded Metal Arc Welding (SMAW or ‘stick welding’), Gas Metal Arc Welding (GMAW or MIG welding), and Flux-Cored Arc Welding (FCAW).

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher asks pupils about different ways metals can be joined permanently and introduces arc welding as one of the most common methods.
Pupils’ Activity: Pupils respond to the questions and listen attentively.
Learning Point: Pupils are introduced to the topic of arc welding and its relevance.

Step 2: Meaning of Arc Welding

Time: 10 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines arc welding as a process of joining metals by electric arc and explains how heat is generated to melt the metals.
Pupils’ Activity: Pupils listen, take notes, and ask clarifying questions.
Learning Point: Pupils understand the definition of arc welding.

Step 3: Principle of Arc Welding

Time: 5 minutes
Teaching Skill: Explanation
Teacher’s Activity: The teacher further explains the principle of arc formation and the role of the electric arc in melting the metals.
Pupils’ Activity: Pupils observe and listen to the explanation.
Learning Point: Pupils grasp the fundamental principle behind arc welding.

Step 4: Basic Types of Arc Welding

Time: 10 minutes
Teaching Skill: Classification
Teacher’s Activity: The teacher explains and lists the basic types of arc welding: non-consumable electrode arc welding and consumable electrode arc welding, giving examples.
Pupils’ Activity: Pupils identify and differentiate between the types of arc welding.
Learning Point: Pupils learn about the different categories of arc welding processes.

Step 5: Demonstration of Arc Welding

Time: 5 minutes
Teaching Skill: Demonstration
Teacher’s Activity: The teacher demonstrates how to set up the arc welding machine, select an electrode, and establish an arc on a mild steel plate, emphasizing safety precautions.
Pupils’ Activity: Pupils observe the demonstration carefully, paying attention to safety procedures.
Learning Point: Pupils see a practical application of arc welding and understand safety.

Step 6: Practical Practice

Time: 5 minutes
Teaching Skill: Practical Application
Teacher’s Activity: The teacher guides pupils to practice making simple butt joints on provided mild steel plates using the arc welding machine and electrodes, ensuring close supervision.
Pupils’ Activity: Pupils, in groups or individually (depending on equipment), practice establishing an arc and welding a simple butt joint under supervision.
Learning Point: Pupils gain hands-on experience in arc welding.

Step 7: Evaluation/Review

Time: 5 minutes
Teaching Skill: Questioning/Assessment
Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

What is arc welding?
Briefly explain the principle of arc welding.
Mention two basic types of arc welding.
State two safety precautions to observe during arc welding.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson on arc welding and assigns homework to research specific applications of arc welding in industry.
Pupils’ Activity: Pupils listen to the summary and copy the homework assignment.
Learning Point: The lesson is reinforced, and pupils are encouraged to explore further.

Lesson Keywords

Arc Welding – A process that joins metals using heat from an electric arc.
Electrode – A metal rod or wire that conducts electricity and often melts to become part of the weld.
Butt Joint – A type of weld joint where two metal pieces are placed edge-to-edge and welded.
Consumable Electrode – An electrode that melts and becomes part of the weld.
Non-Consumable Electrode – An electrode that does not melt during the welding process.

Differentiation

For struggling learners, the teacher will provide more one-on-one guidance during the practical session and simplify explanations. Advanced learners can be challenged to identify different types of electrodes and their applications or research advanced welding techniques.

Note for teachers using this lesson plan

Ensure all safety equipment is available and in good working condition before commencing any practical demonstration or activity. Emphasize safety throughout the lesson. Provide sufficient supervision during pupils’ practical sessions to prevent accidents.