Vertical-down welding position
Vertical-down position: welding from top to bottom with higher deposition rate for thin sheets, typical in pipeline welding.
Physical-Chemical Mechanism of Action
In the vertical-down position, the welding torch is moved from top to bottom. Gravity helps push the molten metal downward and increases the deposition rate, especially on thinner sheets.
Metallurgical Relevance & Welding Risks
This position can lead to faster cooling of the weld. If cooling is too fast (t8/5 < 5 s), hard, crack-sensitive martensite forms. This increases susceptibility to hot cracking and reduces the mechanical strength of the joint.
Shop Practice & Action Guidelines
• Torch: Move the torch from top to bottom.
• Temperature control: Keep the molten temperature constant to ensure a uniform deposition rate.
• Cooling time: Ensure sufficient cooling time (t8/5 > 25 s) to stabilize the microstructure and increase the toughness of the steel.