Thickness in welding.

[warrior1987]

Hi everybody,

I would like to hear your opinion on the influence of thickness in welding and why it's so important.

I know that it can affect the cooling rate, for example in carbon steels and low alloy steels. When the thickness is increased, it's more probable that welding generates harder microstructures like martensite.

I also know that welding thicker sections is more difficult, specifically in terms of the soundness of the weld.

I don't have much experience in welding in the field, but I consider that I have a strong basis in metallurgy. However, some aspects are out of my range.

I would like to hear your opinions about this.

Thanks and regards.

 

[weldstan]

As T increases so does residual tension stress across the weld. Weld quality does not really decrease other than the effect of more weld passes generate the probability of more welding flaws introduceed by the welder. The faster cling rates noted by you do require increased preheating and possibly PWHT.

 

[mfgenggear]

it really depends on the method of welding, and manual vs automatic, and robots.

 

[kingnero]

Cooling rate, as you mentioned, causing all kinds of cracking and/or requiring preheat that burns through your gloves
Constraints, as noted by weldstan, thick plates don't accomodate shrinkage that well,
and weld geometry (more difficult to weld in a deep groove like a 4" U-joint of a 1/2" half V) than a 90° fillet weld.
Lack of fusion defects are also more common in thicker materials, but that's a secondary effect,
Z-quality steel becomes important (through-thickness tests to check for MnS or other (de)lamination defects),
that's about all I can think of right now.