Weld Metal Solidification
Weld metal solidification is the process where the liquid weld pool transitions to a solid crystalline state during cooling. This affects the structure and crack resistance of the weld.
Physical-Chemical Mechanism of Action
The liquid weld pool solidifies into a crystal structure during cooling. This transition from liquid to solid depends on the cooling rate and the interaction of metal elements in the weld metal.
Metallurgical Relevance & Risks in Welding
Incorrect cooling rates can lead to different microstructures with varying resistance to cracking. Too-fast solidification can produce glass-hard martensite, which is prone to cracking. Too-slow cooling can lead to coarse grains and reduced toughness.
Workshop Practice & Action Guidelines
To achieve a homogeneous microstructure with good crack resistance, the cooling rate must be controlled. For steels with high carbon content, fast cooling (t8/5 < 10 s) is often necessary to avoid brittle microstructures. For low-carbon steels, slower cooling (t8/5 > 20 s) can help minimize grain coarsening.