Welding Tips and Tricks

Hello Folks,
Before I get to my question I would like to thank Jodie for the excellent videos and also thank you to all of the people that take the time to respond to questions posed by us less experienced welders.

I have welded mild steel only. I have read a few posts that refer to the colour of the weld bead stating that a grey or not shiny bead is undesirable. I know that there are various causes for the bead to not be shiny such as inadequate shielding or cleaning. My question is not why the bead may be grey or dull in appearance but what effect does this appearance have on the weld integrity? My results vary, in some instances the bead is nice and shiny, but more often the bead would be better described as a grey. There does not appear to be porosity in the grey welds. I have done rudimentary failure testing, the welds do not fail, they are stronger than the parent material. Do the shiny beads have more strength than those that turn out dull grey?

Cheers.

The bead on low carbon steel will be mostly grey which wire brushes off easily. If you are getting alot of scaling, this may indicate excessive heat which will increase the heat affected zone of the parent metal. This may not be a problem if the parent metal has no particular heat treatment or temper, but the ideal objective of welding is to join two pieces of metal with the least disturbance to the parent metal possible. In this case, you would increase weld speed or reduce current.

Generally speaking, the bead color is an indicator of whether excessive heat was used in the weld. There are other causes, including torch angle, gas flow, wind or draft, contamination (sometimes even from the gas... moisture is a common cause), but, ruling these things out, it's a heat indicator.

Also "generally speaking", if a few seconds with a wire brush gets you back to "shiny", there's no harm to the weld itself. The hardness/ductility of the metal near the weld may be affected by excess heat, but this usually only matters in higher alloys, like stainless steels and 4000 series carbon steels for most of us. There are alloys where it's more critical, but the average welder is not likely to encounter them, especially when starting out on the learning curve.

On plain ol' mild steel, it's not a strength issue, as you've noted through testing (and good on you for doing the testing).

Steve S

Good question as I have been wondering about this myself. Most of my beads on mild steel come out dull and grey, but shine up quite nicely with a wire bruch or wheel.

Well Redacres looks likke you have good responce to your question so welcome to the forum.

I have not noticed any scale and the welds always clean up nicely with a light wire brushing. I think I'm doing okay. I do try not to overheat the parent metal, when overheating does happen porosity is very evident. Thanks.