WELD JOINT: TP100 to C1030 Q/T 90ksi

[lhud]

Just some background regarding a joint our shop uses often.
They mig weld 1/2" TP100 to an 8' steel ring (C1030, Q&T to 90ksi) at approx. 20 equally spaced points with two oval welds at each point. The steel ring is 3.5" thick and is preheated to 150 deg. F. The 1/2" TP100 is not preheated. The shop uses the ER-110 metal core wire. The TP100 is similar to ASTM A514 and has a minimum yield of 100ksi but with a maximum of .1% carbon.
I am experiencing cracks after the unit has been in service and also had some failure analysis done and found the cracks to originate in the HAZ of the weld.
I am not directly involved with the shop procedures but think the shop should be preheating to a higher temperature - 400 deg. F and using a filler wire to match the lower strength material such as a 7018 or 8018 type wire.

Comments?

 

[backpurge]

Are they controlling the cool down rate after welding has been completed, not familiar with USA material grades but it sounds as if it could be hydrogen cracking.

Someone far more intelligent will be along shortly to give you a better answer

 

[TechnicAl]

Is the 1030 the same as AISI 1030 which is a 0.30 carbon steel?
You say the cracks start in the HAZ....is that the TP100 or the 1030 HAZ?

Having asked that I would consider a ring 8 feet diameter x 3.5 inches thick to need a higher preheat than 150 oF. It also needs to be consistently heated preferably in an oven for a at least 2 hours to soak through.

I agree that there is absolutely no point in trying to match the higher strength steel. The lower strength is all thats needed, after all this will be the weak point.

Having said that if its cracking in the HAZ its probably Hydrogen related and if so the crack will usually appear in the higher strength part of the weld. If the weld metal has higher strength than the plate the crack will often appear in the weld.....and vice versa.

I dont know what TP100 is either but if like you say its mild steel then the 7018 and a 400 oF preheat sounds good to me

 

[backpurge]

Wwell put Al

Like I said, someone far more intelligent will be along

 

[lhud]

Thanks guys.
Yes the CS 1030 ring is 0.30% carbon and the TP100 is similar to ASTM A514, with a minimum yield of 100ksi and 0.1% carbon. I am not sure if the crack in the HAZ is in the TP100 or the 1030. I too am suspicious of the cold cracking but have not been able to do any post weld NDE within the 72 hour time frame where the cold cracking is likely to occur after which time it is not as likely to occur.

Thanks for your input. Good day.

 

[TechnicAl]

Thats right, if it hasnt cracked after 72 hours it probably wont.....well not through H2 anyway