Class: Senior Secondary School 2 (SS2 / SSS 2)
Term: First Term
Week: 3
Age: 16 years
Duration: 45 minutes
Subject: Metal Work
Curriculum Theme: Pre-Vocational Studies
Previous Lesson: Soldering: Soft and Hard Soldering.
Topic: Brazing
Subject Matter: Meaning of brazing and brazing methods.

Specific Objectives

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

Cognitive Domain:

Define brazing.
State different methods of brazing.
Identify the materials used in brazing.

Affective Domain:

Appreciate the importance of brazing in metal joining.
Value safety precautions during brazing operations.

Psychomotor Domain:

Identify the components of a brazing setup.
Observe the process of joining metals by brazing.

Collaborate effectively during group discussions on brazing techniques.
Communicate ideas clearly regarding metal joining processes.

Reference Materials

The following resources were used in planning this lesson:

Senior Secondary Schools Education Curriculum
State Unified Scheme of Work
D. N. Onwuka (2010). Metal Work Technology for Senior Secondary Schools. Evans Brothers (Nigeria Publishers) Limited.

Instructional Materials

The teacher will teach this lesson with the aid of:

Brass rod
Mild steel plates
Furnace (if available or pictures/diagrams)
Oxy-acetylene torch (if available or pictures/diagrams)
Safety goggles and gloves
Charts showing brazing methods

Rationale for the Lesson

This lesson enables pupils to understand brazing as an important metal joining technique. It helps them to differentiate it from other joining methods and to recognize its applications in various industries and daily life.

Prerequisite/Previous Knowledge

Pupils are expected to have some basic knowledge of different types of metals and other metal joining processes such as welding or soldering.

Lesson Content/Board Summary

Brazing

Meaning of Brazing

Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metal into the joint. The filler metal has a lower melting point than the base metal. Brazing uses a brass filler rod and is performed at high temperatures, typically above 450°C, but below the melting point of the base metals.

Methods of Brazing

There are several methods used for brazing, depending on the application and type of metals being joined:

Dip Brazing: In this method, the parts to be joined are assembled with the filler metal in place and then dipped into a molten bath of flux or filler metal. The molten bath heats the assembly uniformly, causing the filler metal to flow into the joint.
Furnace Brazing: The parts are assembled with filler metal and flux, then placed in a controlled atmosphere furnace. The furnace heats the entire assembly uniformly to the brazing temperature, which melts the filler metal and forms the joint.
Resistance Brazing: Heat is generated by passing a high electric current through the joint area. Electrodes are often used to hold the parts together and apply pressure while the current flows, melting the filler metal.
Torch Brazing: This is a common manual method where a torch (e.g., oxy-acetylene or oxy-propane) is used to heat the joint area. The filler metal is then fed into the heated joint, where it melts and flows by capillary action.

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 mention different ways metals can be joined together. The teacher then introduces brazing as another method of joining metals.
Pupils’ Activity: Pupils respond to the teacher’s questions by mentioning methods like welding and soldering. They listen attentively as the teacher introduces the topic.
Learning Point: Pupils recall previous knowledge about metal joining and are introduced to brazing.

Step 2: Meaning of Brazing

Time: 10 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher explains the meaning of brazing, emphasizing the use of a filler metal with a lower melting point than the base metals and the high temperature involved.
Pupils’ Activity: Pupils listen, take notes, and ask questions for clarification regarding the definition of brazing.
Learning Point: Pupils understand the definition and key characteristics of brazing.

Step 3: Materials for Brazing

Time: 5 minutes
Teaching Skill: Identification
Teacher’s Activity: The teacher displays or shows pictures of materials like brass rods and mild steel plates, explaining their roles in the brazing process.
Pupils’ Activity: Pupils observe the materials and identify them, noting down their uses.
Learning Point: Pupils identify the essential materials used for brazing.

Step 4: Brazing Methods

Time: 10 minutes
Teaching Skill: Explanation/Differentiation
Teacher’s Activity: The teacher explains the different methods of brazing: dip, furnace, resistance, and torch brazing, highlighting the differences between each method.
Pupils’ Activity: Pupils listen, take notes, and ask questions to understand the various brazing methods.
Learning Point: Pupils learn about the different techniques used in brazing.

Step 5: Demonstration/Observation of Brazing Process

Time: 5 minutes
Teaching Skill: Demonstration/Practical Application
Teacher’s Activity: The teacher guides pupils to observe a demonstration (if possible, or through a video/detailed diagrams) of joining thin mild steel plates using a brass rod with an oxy-acetylene flame or furnace.
Pupils’ Activity: Pupils prepare metal samples and carefully observe the brazing process, noting the steps involved and the equipment used.
Learning Point: Pupils gain practical insight into how brazing is performed.

Step 6: Safety Precautions

Time: 5 minutes
Teaching Skill: Safety Awareness
Teacher’s Activity: The teacher discusses important safety precautions to be observed during brazing operations, such as wearing safety goggles, gloves, and working in a well-ventilated area.
Pupils’ Activity: Pupils listen and contribute to the discussion on safety, understanding the risks and preventive measures.
Learning Point: Pupils learn about the necessary safety measures for brazing.

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 brazing?
Mention two materials used as filler metals in brazing.
List three methods of brazing.
State one safety precaution to observe during brazing.

Pupils’ Activity: Pupils answer orally and in writing.
Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 5 minutes
Teaching Skill: Summarization/Assignment
Teacher’s Activity: The teacher summarizes the main points of the lesson on brazing and assigns homework: “Draw and label the setup for torch brazing.”
Pupils’ Activity: Pupils listen to the summary and copy the homework assignment.
Learning Point: Pupils consolidate their learning and prepare for further study.

Lesson Keywords

Brazing – A metal-joining process using a filler metal that melts below the base metals’ melting point.
Filler metal – The metal added to fill the joint during brazing, typically brass.
Brass rod – A common filler material used in brazing, made of copper and zinc.
Oxy-acetylene torch – A tool used for heating metals in torch brazing.
Furnace brazing – A brazing method where parts are heated in a controlled atmosphere furnace.
Dip brazing – A brazing method where parts are immersed in a molten bath.
Resistance brazing – A brazing method using electric current to generate heat.

Differentiation

For pupils who grasp the concepts quickly, the teacher can encourage them to research specific applications of brazing in different industries. For pupils who require more support, the teacher will provide simplified diagrams and allow more time for practical observation and questions, using peer tutoring where appropriate.

Note for teachers using this lesson plan

Teachers should ensure that safety precautions are strictly followed, especially if a practical demonstration involving heat is conducted. If actual equipment is unavailable, visual aids like videos, pictures, and diagrams should be used extensively to illustrate the concepts and processes clearly. Encourage pupils to ask questions to deepen their understanding of this practical skill.