Will need further information.
1) What type or types of materials are you joining?
2) What type of joint (lap, butt,...)?

Does sound like hot cracking. Volts seem alittle high to me for the amps you are running. Also dont like the 25mm wide bead compared to 3mm depth.

kam

Hi Sidekick

From your question, I understand that you are welding stainless steel using a 309 filler with a 100°C pre-heat and 400°C maximum interpass temperature. Is this correct? If so, I have the following comments:

1) For 300 series stainless steels (is this what you are welding?) one would try to weld as cold as possible. This means NO pre-heat, with a maximum interpass temperature of 175°C.
2) The bead size is way too wide. For a wide weld, use string beads that are laid next to each other. I would not like to go wider that around 14mm or so.
3) Theoretically 309 filler should give you a relatively hot-crack resistant weld, because it contains around 10% ferrite. As long as you do not have excessive contamination on your base metal or filler, hot cracking SHOULD not be a problem.

The big warning light about your weld parameters is the fact that you are welding with a very high heat. This will lead to excessive grain growth in austenitic stainless steels, leading to a weakened structure. (Weakness in tensile strength and low ductility.) If, in addition, you have a weld with a high restraint, you could quite easily get a type of overstress cracking.

Let us also know where the cracks are located (In the weld metal, in the HAZ, at the toe of the weld etc.) and appearance. (Long crack in the centre of the weld metal, cracks accross the weld metal, branched cracks etc.) As well as any possible contamination possibilities. (Sulphour containing compounds, chloride containing compounds etc.)

Hope this helps.

Regards
Niekie Jooste
Fabristruct Solutions