Class: Senior Secondary School 2 (SS2 / SSS 2)
Term: First Term
Week: 5
Age: 16 years
Duration: 45 minutes
Subject: Metal Work
Curriculum Theme: Pre-Vocational Studies
Previous Lesson: Torch Brazing.
Topic: Introduction to Welding
Subject Matter: Meaning of welding (permanent joining of metals by fusion), importance of welding, welding groups and processes, methods of applying welding

Specific Objectives

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

Cognitive Domain:

Define welding.
State the importance of welding in society.
Identify different welding groups.
Explain various methods of applying welding.

Affective Domain:

Appreciate the significance of welding in various industries.
Develop an interest in learning more about welding processes.

Psychomotor Domain:

Prepare metal work pieces for arc welding.
Demonstrate basic safety practices related to welding.

Collaborate with peers during practical demonstrations.

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 by A.O. Akinola and others

Instructional Materials

The teacher will teach this lesson with the aid of:

Arc welding machine
Electrodes
Steel plates
Welding helmet
Welding gloves
Leather apron

Rationale for the Lesson

This lesson helps pupils understand how metals are permanently joined, which is a fundamental skill in many technical fields. Knowing about welding prepares pupils for practical applications in fabrication, construction, and repair, making them aware of a valuable vocational skill.

Prerequisite/Previous Knowledge

Pupils have basic knowledge of different types of metals and simple workshop tools.

Lesson Content/Board Summary

Introduction to Welding

Meaning of Welding

Welding is a fabrication process that joins materials, usually metals or thermoplastics, by causing fusion, which is distinct from lower temperature metal-joining techniques such as brazing and soldering, which do not melt the base metal. It involves applying heat to melt the workpieces and add a filler material to form a pool of molten material that cools to form a strong joint.

Importance of Welding

The importance of welding includes:

It is used to join different types of metals permanently.
It is essential in the construction of buildings, bridges, and other structures.
It is vital in the manufacturing of vehicles, ships, and aircraft.
It is used for repairing broken metal parts and equipment.
It plays a key role in the fabrication of various industrial and domestic products.

Welding Groups and Processes

Welding processes can be broadly grouped based on their level of automation:

Semi-automatic Welding: In this process, the welding operator controls the travel speed and direction of the weld, but the filler wire feeding is automated. Examples include MIG/MAG welding.
Automatic Welding: Both the travel and wire feeding are automated, requiring minimal human intervention during the welding operation. Examples include Submerged Arc Welding (SAW) and Robotic Welding.

Methods of Applying Welding

There are several common methods used for applying welding, each suited for different materials and applications. These include:

Arc Welding (Shielded Metal Arc Welding – SMAW): Uses an electric arc between an electrode and the workpiece to melt the metals. It is widely used due to its versatility and cost-effectiveness.
Gas Welding (Oxy-fuel Welding): Uses a flame produced by burning a mixture of oxygen and a fuel gas (like acetylene) to melt the metals.
MIG/MAG Welding (Gas Metal Arc Welding – GMAW): Uses a continuous solid wire electrode fed through a welding gun and a shielding gas (Metal Inert Gas / Metal Active Gas) to protect the weld from contamination.
TIG Welding (Gas Tungsten Arc Welding – GTAW): Uses a non-consumable tungsten electrode and an inert shielding gas to produce the weld. It is known for high-quality, precise welds.
Resistance Welding: Uses heat generated by resistance to electric current flow at the interface of two workpieces held together under pressure.

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 greets the pupils and asks them to recall how different parts of a metal gate or window frame are joined together.
Pupils’ Activity: Pupils respond by mentioning methods like bolting, riveting, and possibly welding.
Learning Point: Pupils connect prior knowledge to the new topic of joining metals permanently.

Step 2: Meaning and Importance of Welding

Time: 10 minutes
Teaching Skill: Explanation/Lecture
Teacher’s Activity: The teacher defines welding as a permanent joining process by fusion and explains its importance in various industries and daily life, using examples.
Pupils’ Activity: Pupils listen attentively, take notes, and ask questions for clarification.
Learning Point: Pupils understand the definition and significance of welding.

Step 3: Welding Groups

Time: 8 minutes
Teaching Skill: Classification/Discussion
Teacher’s Activity: The teacher introduces the two main groups of welding: semi-automatic and automatic, explaining the difference in operator involvement.
Pupils’ Activity: Pupils identify and differentiate between semi-automatic and automatic welding based on the teacher’s explanation.
Learning Point: Pupils learn about the different classifications of welding processes.

Step 4: Methods of Applying Welding

Time: 10 minutes
Teaching Skill: Explanation/Illustration
Teacher’s Activity: The teacher explains various methods of applying welding, such as Arc welding, Gas welding, MIG/MAG welding, and TIG welding, focusing on their basic principles.
Pupils’ Activity: Pupils listen, observe, and engage in discussion about the different welding methods.
Learning Point: Pupils gain knowledge of common welding techniques.

Step 5: Practical Demonstration/Preparation for Arc Welding

Time: 7 minutes
Teaching Skill: Demonstration/Practical Application
Teacher’s Activity: The teacher demonstrates how to safely prepare metal work pieces for arc welding, including cleaning and proper alignment, using the provided materials.
Pupils’ Activity: Pupils observe the demonstration carefully and ask questions regarding the preparation steps.
Learning Point: Pupils learn the practical steps involved in preparing materials for welding.

Step 6: Safety Precautions in Welding

Time: 5 minutes
Teaching Skill: Emphasizing Safety
Teacher’s Activity: The teacher emphasizes important safety precautions that must be observed during welding operations, such as wearing protective gear and ensuring proper ventilation.
Pupils’ Activity: Pupils listen and note the safety precautions, understanding their importance.
Learning Point: Pupils understand the critical need for safety when 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:

Define welding.
State three importance of welding.
Mention two main groups of welding.
List two methods of applying 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 and assigns homework, asking pupils to research different types of welding electrodes.
Pupils’ Activity: Pupils listen to the summary and copy down the homework.
Learning Point: Pupils consolidate their learning and prepare for further study.

Lesson Keywords

Welding – A fabrication process that joins materials, usually metals or thermoplastics, by causing fusion.
Fusion – The process or result of joining two or more things together to form a single entity.
Electrodes – Conductors through which electricity enters or leaves an object, used in arc welding to create the arc and often as filler material.
Arc welding – A welding process that uses an electric arc to create heat to melt and join metals.
Semi-automatic welding – A welding process where the operator controls travel speed and direction, but wire feeding is automated.
Automatic welding – A welding process where both travel and wire feeding are automated.

Differentiation

For pupils who grasp concepts quickly, the teacher can provide additional reading on specific welding technologies or ask them to research the applications of different welding methods. For those needing more support, the teacher can use simplified diagrams, provide one-on-one explanations during practical sessions, and encourage peer learning.

Note for teachers using this lesson plan

Emphasize safety protocols rigorously before any practical demonstration. Ensure all pupils understand the potential hazards and necessary precautions. Encourage active participation during the practical preparation phase to ensure all pupils get a hands-on feel for the process. Use visual aids like charts or short videos showing different welding processes if available.