WELDING BASICS FOR BEGINNER Part-1

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Most of the Welding process utilises heat and or pressure for making a weld joint. Based on the method of heat generation and its application the welding process can be grouped into six main classes.

Under most of these classes, there are a number of welding processes with special characteristics and fields of applications.

the figure shows all significant welding and allied processes, used in the plant sector.

Factors for Arc Welding:

  •   Arc Length
  • Current Setting
  • Correct Welding Angle
  •   Correct Travel Speed
What is Arc Length ?

Distance between the tip of an electrode & workpiece

Types of Arc Length:

  1. Standard -3 mm
  2. Short-Less than 3 mm
  3. Long-more than 3mm
Advantages of Standard & Short-Arc Length:

  1. Good Weld Joint
  2. Good Penetration
  3.  Max. Strength
  4.  Less chance of porosity
  5. Maximum ductility
  6.  Less or no oxidation

 Correct Current:

  • If very high: The electrode melts too quickly and molten metal is large and  irregular
  •  If very low: There would not be sufficient heat to melt the base metal and the  molten  pool will be too small, besides it would pipe up and look irregular
Correct Travel Speed

  • Correct weld speed is weld appearance is neither Narrow or broad
  • This is achieved by practice
CORRECT WELD ANGLE:


ELECTRODE:
  • The electrode consists of metallic wire –
  • Core Wire - Wire was drawn depending on size (2.5/3.15/4/5 mm)
  • Coated with Flux covering it uniformly.
Electrode
Selection of Electrodes:
  • Composition of Base Metal
  •  Type of Joint
  •   Position of Weld
  •  Physical Properties Required
  •    Condition of fit up
  •  Application
Function of Flux Coating:
  •  Helps to Strike & maintain the arc
  •  Makes core wire rust-proof
  •  Makes electrodes insulative
  •  Produces protective gaseous shield
  •  Produces slag to protect from atm. contamination (O2 and N2)
  •  Helps to deoxidize and refine because of deoxidizers (ferro-silicon, ferro- titanium, ferro-manganese)
  •   Helps to form a sleeve at the burning end which concentrate welding heat
  •  Helps for positional welding
  •  Helps to prevent spatter loss
Methods of Striking Arc
  • Method of Striking
  • Scratching Method
  •  Tapping Method

Note-

Methods of striking arc also depend on type of electrode – Joining hard facing and also importantly depends on the type of flux coating 

AWS Codification for CS & LASCE:

Joint Design (Edge Preparation):

Advantages:

  •  Controls Distortion      
  •  Minimize Residual Stresses
  • Facilitate good workmanship
  • Achieve proper weld strength
  •  Reduce welding costs, and
  • Result in greater reliability


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