Lecture Overview: Welding

Introduction

• Lecturer: Jeera Sardana with 10+ years of experience
• Importance: Welding often has at least one two-mark question in competitive exams
• Duration: 2 to 2.5 hours

Session Announcements

• Upcoming Mega Workshop: Strategy to be in top 1% for GATE 2024
• Date & Time: Tomorrow at 12:30 PM
• Registration: Via session description

Topics Covered

1. Production vs Manufacturing: Explained that manufacturing is a subset of production
2. Introduction to Welding

Welding Basics

• Definition: Process of joining two materials with heat or pressure, with or without filler material
• Types of Welding Explained with Animation
  • Arc Welding: Shown using two plates and electrode
  • Lab Methods: How casting and welding are performed in laboratories

Weld Bead Geometry

• Components:
  • Weld Bead: Area filled with material after welding
    • Penetration: Below surface into plates
    • Reinforcement: Above the plate surface
  • Heat Affected Zone (HAZ): Region affected by welding heat
  • Unaffected Zone: Area untouched by weld heat
• Strength Analysis:
  • Weld Bead: Highest strength
  • HAZ: Lowest strength due to uncontrolled heat treatment
  • Unaffected Zone: Intermediate strength
• Dilution:
  • Formula: Area of penetration divided by total weld bead area
  • Used for numerical calculations in exams

Types of Welding Processes

1. Shielded Metal Arc Welding (SMAW)

• Components: Workpiece, electrode, power source
  • Principle: Utilizes potential difference to ionize air and create welding arc
  • Electrode and Flux: Shields workpiece and improves weld quality
  • Drooper Characteristics: Used to manage current and voltage
  • Categories: Manual, semi-automatic, and automatic welding

2. Submerged Arc Welding

• Setup: Continuous electrode wire and flux drumming
  • Benefits: Continuous welding preferred for mass production like LPG cylinders

3. TIG Welding

• Components: Tungsten electrode, filler rod, inert gas
  • Application: Welding of thin aluminum sheets

4. MIG Welding

• Setup: Continuous metal wire electrode with inert gas
  • Benefit: No filler rod needed, used in industry

5. Other Welding Processes

• Plasma Arc Welding: Achieves temperatures up to 20,000°C
  • Electro-Slag/Gas Welding: Vertical welding for shipbuilding

Resistance Welding

1. Principles

• High Current, Low Voltage
  • Application: Mainly for lap joints

2. Types

• Spot Welding: Defined by phases (Squeeze, Weld, Hold)
  • Projection Welding: Multi-spot welding using embossing
  • Flash Butt Welding: Used for joining railway tracks
  • Seam Welding: Continuous welding for making cylindrical objects
  • High-Frequency Welding: Used in pipe manufacturing

Solid-State Welding

• Explosive Welding: Joins metals using controlled explosions
• Friction Welding: Joins materials by generating heat through friction
• Ultrasonic Welding: Used in electronics for joining small components

Gas Welding

• Oxy-Fuel Welding: Uses gases like acetylene for combustion
• Flame Types: Neutral, oxidizing, and carburizing flames explained

Allied Processes

• Soldering, Brazing, Brace Welding: Techniques that melt filler material but not the base material
  • Applications: Electrical circuits, hydraulic circuits

Radiation Energy Welding

• Electron Beam Welding: Uses electron beams in a vacuum
• Laser Beam Welding: Uses laser light to generate heat for welding
• Atomic Hydrogen Welding: Uses hydrogen for a better thermal efficiency

Casting Defects

• Types & Causes: Blisters, blow holes, porosity, and shrinkage cavities explained
• Remedies: Improving mold strength and porosity

Miscellaneous

• Heat Transfer in Welding
  • Formulas for 2D and 3D Heat Flow
• Duty Cycle: Determines the effective arc-on time during welding
• Arc Blow: Magnetic effects causing weld defects

Conclusion

• Review of important welding techniques and defects
• Announcement of handwritten notes availability and upcoming sessions