Hi,
We have been facing the issue of cracking in Material SS310 with filler wire ER310, GTAW, and T-joint fillet welds.
The product is a burner. We have already reduced heat input and increased throat as an experiment, but the problem still persists.

Can we use ER 309LMo, but as per the application and service point of view, this filler is made for a lower temperature than SS310 in service? What are your suggestions?

Reply:-

Dear Sir,

SS 310 is fully austenitic in microstructure and sensitive to hot cracking. ER 310 SS weld metal doesn’t contain any ferrite; the structure is 100% austenite because it is designed for use in high-temperature service up to 1100 °C.

Ferrite is a trap for impurities like ‘S’ & ‘P’. So, your filler metal ER 310L must be low in C ( <0.02%Wt ) , P (<0.02%Wt) & S (<0.015%Wt) . Hot-cracking problem is increased due to the use of filler metals with high levels of ‘C’ , ‘ S ‘ & ‘ P’. In your product, a fillet joint, under high restraint condition unable to support the weld metal produced. Before welding, proper cleaning of the faying surfaces is utmost important.

So, in order to meet with your application, I advice you to use ER 310 filler material with a H.I. of 1.0 KJ/mm max and an inter pass temperature around 100 °C
If possible, use Sandvic Asia brand (Now Exaton) ER 310 filler metal (with low C, S, and P) with a low H.I. and inter-pass temperature as stated above.
The ER 309LMo weld can withstand a service temperature of up to 300 °C. It contains 5–10 Ferrite. Although resistant to cracking, there is a chance that this ferrite will convert to the brittle Sigma phase when the service temperature is between 593 °C to 704 °C.

Please send me the composition of your base metal and ER 310L SS (deposited weld metal chemistry) or filler metal TC for the weld metal analysis.