Depth of Fusion
Penetration depth is the measure of how deep the molten weld pool penetrates into the surface of the base material. Excessive penetration can lead to embrittlement and porosity, while insufficient penetration can result in poor fusion and hot cracks.
Physico-chemical mechanism of action
Penetration depth refers to the depth of the molten weld pool into the base material. This process is determined by the temperature and the residence time of the weld pool. An excessively high temperature or prolonged residence time leads to deeper penetration, while a low temperature or short residence time reduces it.
Metallurgical relevance & risks when welding
Excessive penetration can lead to embrittlement and porosity, as the molten material penetrates into the microstructure of the base metal and solidifies there. This can impair the mechanical strength and toughness of the weld. Insufficient penetration, on the other hand, results in poor fusion between the materials, which can cause hot cracks and lack of hardness in the weld.
Workshop practice & instructions
To achieve optimal penetration depth, it is important to carefully control the melt temperature and the residence time of the weld pool. A typical penetration depth for steel welds is about 2-3 mm. If penetration is too deep, the welding time can be increased to allow the material to penetrate deeper into the base metal. If penetration is too shallow, the temperature can be increased or the residence time extended to achieve greater penetration.