Weld Repair 4330 mod

[JT0202]

Looking to repair 4330mod 3/8" PJP on a 3" plate, V bevel.

YS 122ksi ; UTS 135ksi ; CVNs avg 50ftlbs @-4F ; 277/285 BHN

Will use E14018-G, although I have read also E8018-C3 can be used
preheat 600-650F
max interpass 750F
PWHT 1100F for 3hr

The results shall need to comply with CVNs avg 31 ftlbs @-4F ; 350 Hv


Any suggestions and/recommendations would be appreciated.

JT

 

E14018-G filler is off the charts, at least in SFA5.5. Typo?
Assuming this is a well-alloyed designation, I would say you are heading for the #1 pitfall in welding high hardenability steels: aiming to match the alloy content of the filler with that of the base metal. When the weld metal dilutes the higher carbon base metal, the mixture results in an excessively hard deposit.
You should back off and use a much lower alloy filler metal, carbon steel E7018 will probably do just as well.
Your parameters look OK, but I am not very confident you can make the CVN target, at least not in the base metal heat-affected zone, but perhaps someone else has actual data to offer.
Follow strict moisture control practice, including post-heating for 4 hours min. at the preheat temperature.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Tmoose]

I'm curious why the repair is needed, and pix or dwgs of the part geometry.

 

[metengr]

I would recommend using a lower matched strength filler metal, E8018-C3 weld rod. I would also suggest you use a temper bead technique to enhance grain refinement in the BM heat affected zone. Drop the preheat to 450-500 deg F, and make sure you cool to below 200 deg F before applying PWHT to ensure complete transformation products.

For the deposit thickness of 3/8", I would PWHT for 30 minutes at temperature, you don't need 3 hours. Make sure the PWHT temperature is at least 50 deg F below the original tempering temperature of the 4330 mod plate.

Last, qualify a WPS with impact testing before you do anything.

 

[JT0202]

@ironic metallurgist
As per SFA5.5, "in order to meet the alloy requirements of the "G" group, the undiluted weld metal shall have the minimum of at least one of the elements listed in this table. Additional chemical requirements may be agreed upon between the purchaser and supplier".
Thank you for the input

@Tmoose

@metengr
For the PWHT I already checked the PWHT is -50F below the original tempering temperature

E8018-C3
preheat 500F
max interpass 750F
Temper bead layer technique with increased HI and 50% overlap aim
slow cool down to 200F
The final temper bead layer shall be removed afterwards
PWHT 1100F for 30min

 

[bobjustbob]

I have a question for those suggesting a lower strength filler rod. Does this application not require the weld repair to meet or exceed the strength requirements of the base metal? I have not seen either E8018C-3 nor E7018 that would meet the 140ksi tensile strength.

To weld repair castings with similar strengths I would start my testing at a E12018-G rod. I agree to use the rod with the lowest alloy I could and still get the properties. The struggle that I see qualifying the weld procedure is achieving the 31 ft-lbs in the fusion/HAZ. The 4340 is going to get very hard in that area due to the carbon and alloy present in the base metal.

 

[pradipgoswami]

Hi JT 0202,

Q&T steels are always weird. Many a times one may have to use welding electrodes/fillers not matching the exact chemistry of the base metal, however achievable mechanical properties could be close to that of base metal.

Metengr had laid out a very detailed guideline for the repair. I would think using E9018M or 10018M for above repair could be a viable option also.

9018M would be my preference due to superior notch toughness values, and less cracking possibilities. However hardness may be less with such weld metal due to more Nickel Content.

Please find the data sheets of the electrodes as attached.

Thanks.


Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
ca.linkedin.com/pub/pradip-goswami/5/985/299

 

[metengr]

I have a question for those suggesting a lower strength filler rod. Does this application not require the weld repair to meet or exceed the strength requirements of the base metal?

In some cases, lower strength filler metal is selected recognizing that the repair is local and does not affect in-service performance. Being this is a 3/8" deposit on a 3" thick plate, this could fall into that category. The elevated strength filler metals can be tricky regarding delayed cracking and notch toughness. You will need nickel alloying in the filler metal, and having a lower strength can help meet this objective.

 

[JT0202]

All thank you for the great advice. It is nice to have some discussions and feedback like this.

I agree there are thoughts in the industry that some try to match the filler metal strength and then have the consequent risk of delayed cracking and notch toughness. Others go for a lower strength to try and dilute this C from the base metal and soften the HAZ. The main problem with these materials is also the V that will precipitate and also contribute to the hardness of the areas. There are too many "inconveniences" when welding these materials, but it is possible. I just want to have an idea of other minds to have a starting point as I have never welded 4330 mod.

I think to start with I will also check with the designers to see the minimum design requirements and from there know how much of an undermatching filler is an option, as I think this will help a lot when welding.


If you have any other comments or additions they are always welcome

Thank you!

JT