HAZ zone breakage on c1018/a-36

Date 04-10-2008 16:33

o.k. here is my dillema, I have .625 diameter c1018 shaft 1.5" long, necked down to .562 x .250 in at one end. this end is pressed into a 3/8" thick a-36 plate leaving an 1/8" deep recess on the back surface for a plug weld. I am using er70s wire gmaw-s . gas mixture is ar/he/co2 steel mix extra. the shafts have started to break off of thier plates right at the haz .What would be some possible solutions to this problem. this design was about to go into prodution. so if anyone has insight on some pwht ideas or possible different filler/ base metal combos I would greatly appreciate them
thanks

By fej2816 Date 04-10-2008 17:22

Any particular reason for 70s procedure? Have you tried 309L SS filler yet? Better for the 18-8 grades of steel.

By RBeldyk (**)

Date 04-10-2008 17:38 Edited 04-10-2008 17:42

The necked down shaft to plate joint is highly restrained; cracks are forming during the welding process and thern upon cooling proprogating. Being a plug weld it is impossible to do a visual examination. A couple things that might help:
- Increase the preheat to 300 F this will decrease the thermal and residual stress that develop.
- Change the joint from a plug weld to a single vee that goes around the shaft welded from the other side of the plate, not the back side where the plug weld is now.

On a economic issue why are you using that expensive of gas?

By GRoberts (***)

Date 04-10-2008 19:18

RB already covered the probable causes, but somethign else to look at is after machining- are the parts being properly cleaned? You could be picking up hydrogen from the machinig fluds and causing hydrogen cracking. More than likely is is from the joint restraint though.

I also 2nd the gas-mix question.

By natecf

Date 04-10-2008 20:41 Edited 04-11-2008 02:14

thank you all for your responses, just finished a new part that was completely cleaned prior to assembly, preheated to 325 f . did not change joint geometry yet.
though, the small vee groove can be easily added
as for the gas-mix, I fully expected the response. My G.M. is good friends with the regional sales guy at our welding supply co. go figure
my earlier post stated that the process was gmaw-s, to clarify, it is actually spray transfer, not short circut. one other reason for the gas mix also