Welding Inspection & Metallurgy API ICP Self Study Notes

10.3.1 Melting Temperature
The melting temperature of different metals is important to know because the
higher the melting point, the greater the amount of heat that is needed to melt
a given volume of metal. This is seldom a problem in arc welding since the
arc temperatures far exceed the melting temperatures of carbon and low-alloy
steels. The welder simply increases the amperage to get more heat, thus
controlling the volume of weld metal melted per unit length of weld at a given,
voltage or arc length and travel speed. A pure metal has a definite melting
temperature that is just above its solidification temperature. However,
complete melting of alloyed materials occurs over a range of temperatures.
Alloyed metals start to melt at a temperature, which is just above its solidus
temperature, and, because they may contain different metallurgical phases,
melting continues as the temperature increases until it reaches its liquidus
temperature.