Sulfur influence on surface tension
Sulfur in the weld pool increases surface tension, which leads to a wider and flatter penetration. This can affect weld bead sharpness.
Physico-Chemical Mechanism of Action
Sulfur in the molten pool increases the surface tension through its molecular structure and chemical interactions. This leads to an increased stress state on the metal surface, which in turn changes the penetration depth during welding.
Metallurgical Relevance & Welding Risks
A higher sulfur content can lead to a larger penetration depth and a flatter weld profile. This can affect the sharpness of the weld and alter the metal's structure, posing risks to strength and toughness. Too much sulfur can also cause distortion and porosity.
Workshop Practice & Action Guidelines
To minimize the effect of sulfur on surface tension, the sulfur content in the molten pool should be controlled. A typical sulfur content is about 0.1 to 0.3 %. If the sulfur content is unusual, the penetration depth and metal structure must be closely monitored. If the sulfur content is too high, adjusting the welding parameters or changing the steel grade may be necessary.