Page 99 - CITS - Welder - Trade Theory

WELDER - CITS

It may be noted from the figure that addition of carbon beyond 0.83% cementite will not exist in the combined form
but appear around the crystal boundaries. Carbon, existing in this form, reduces in tensile strength and ductility
but the hardness continues to increase even beyond 0.83% of carbon.
It may be said that plain steel will have a maximum strength at 0.83% carbon - i.e. when the constituent of steel
is fully pearlite. Addition beyond 0.83% reduces its strength and ductility.

Hardness of carbon of plain carbon steel increases proportionately even beyond 0.83% carbon content.
At room temperature in the annealed condition plain carbon steel contains three main constituents.
a Ferrite
b Cementite
c Pearlite

Welding Of Low Carbon Steel, Medium And High Carbon Steel:
Introduction:
A plain carbon steel is one in which carbon is the only allowing element.
The amount of carbon in the steel controls its hardness, strength and ductility. The higher the carbon the lesser
the ductility of the steel.
Carbon steels are classified according to the percentage of carbon they contain. They are refer red to as low,
medium and high carbon steels.
Low Carbon Steels: Steels with arrange of 0.05 to 0.30 percent are called low carbon steel or mild steel. Steels
in this class are tough, ductile and easily machinable and quite easy to weld.
Welding technique: Up to 6mm,left ward technique is a suitable one. Above 6mm right ward technique is
preferable.

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CITS : C G & M - Welder - Lesson 14-26 CITS : C G & M - Welder - Lesson 14-26