Impact test fails FCAW process

[chakote...@gmail.com]

Dear experts,
We have carried out FCAW WPQR with PWHT. Welding consumable is E71 T12 CJ. Below are the conditions

Test coupon thk- 70 mm
Parent material- S355 G8+N
Process- FcAW
Welding consumable- E71T-12CJ
PWHT Temp- 580 deg C
Soaking time - 280 minutes
Impact test temp- minus 40 deg C
Heat input range (root)- 1.0-1.6 KJ/mm
Heat input range (cap)- 1.0-1.4 KJ/mm
Thermal efficiency- 0.8
Welding position-3G


The above welding consumable is recommended for PWHT.

The impact values are too low at root as well as cap.

Energy values- 16,15,25 J (root)
Energy values- 30,30,31 J (cap)

Can you please focus on impact values failure reasons?

Even if keeping low heat inputs the test has failed.

What could be the possible reasons of failure?

And with the same conditions WPQR passed with 2G position.

Please focus on possible reasons.

Regards,

Vishal

[Ahmed Osman]

Dear Mr Vishal ,

And with the same conditions WPQR passed with 2G position.

welding position is a factor .. as in uphill 3g welding heat is more due to the uphill movement is slow (welding speed ) which lead to increasing the size of grains for the lower pass (like a normalizing effect .. "heating" then "cooling in air" ) which lead to decrease the CVN values ( very clear comparing with the cap passes CVN impact values )

the electrode used is "J" will give 27J@-40c which is already get at the cap.

dilution for FCAW is low comparing to SAW which restrict you for using the benefits of the base metal 

so , 

you can try to change your joint design to minimize the number of passes above the root ( if it possible try double V ) 

also u need to check the consumables MTC for Mn% which affect also the CVN values

Best Regards ,

Ahmed Osman

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[Kannayeram Gnanapandithan]

Fill and caping shall be in Tempering process

THANKS & BEST REGARDS,

KG.PANDITHAN, BE, IWE,  CSWIP 3.1,

ISO 9712 Level 2 in VT,

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International Welding Engineer. 

CONSULTANT-WELDING & QUALITY

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[chakote...@gmail.com]

Yes the general theory says increasing heat input will reduce the impact values. But the feedback from the consumable manufacturer is because of low heat input PQR fails. He is suggesting to increase the heat input for better values. Manufacturer feedback is somehow contradictory. Now can't proceed further without correct root cause.

One more thing, can welding consumable with more nickel content will satisfy the requirement?

[Kannayeram Gnanapandithan]

Not only heatinput ,u have to consider interpass temperature also. Very high and low heat. Input will not be appreciated for better impact values. 

On Tue, 20 Aug 2019 11:09 am , <chakote...@gmail.com> wrote:

Yes the general theory says increasing heat input will reduce the impact values. But the feedback from the consumable manufacturer is because of low heat input PQR fails. He is suggesting to increase the heat input for better values. Manufacturer feedback is somehow contradictory. Now can't proceed further without correct root cause.

One more thing, can welding consumable with more nickel content will satisfy the requirement?

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[PGoswami]

Hi,

 

Please see the attached, info on typical FCAW consumable conforming to AWS E71 T12 CJ specifications. Qualifying PQR with FCAW process  on 70mm thk plates with PWHT and with impact @-46 Deg C is not easy. Following areas should need attention:-

 

·         Impact values of the consumable, qualification position , 1G or 3G?

·         If required ask the consumable manufacturer for impact results in 3G position.

·         Your coupon passed in 2G, that’s due to the stringer bead technique and lower heat input, what were the recorded heat input??

·         Any data on results of the similar product with PWHT(ask consumable manufacturer).

·         In order to have a good and consistent impact 1.2.-1.4% Mn or more would be desirable. However in case of hardness restrictions, Manganese have to be restricted.

·         Last of shielding gas, for consistent -46 Deg C impact on 70mm thk coupons, use  of mixed gas, 80/20 Argon+CO₂ or better(90/10).  Would be advisable.

 

Thanks.

 

P.Goswami.P.Eng, IWE.

Independent  & Consulting Welding & Metallurgical Specialist

Linkedin: https://www.linkedin.com/in/pradip-goswami-2999855/

Email:pgos...@quickclic.net,pradip....@gmail.com

Cell/Whasapp:1-905-9793232

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[chandraknat vaidya]

Yes I agree with Goswami sir.

It is not easy to qualify with impact with low temperature.

Need to control & record minor data for conclusion of any results,including position of welding, Groove geometry, no of passes, heat input & deposition of each pass,gas composition/mixtures,& finally manufacturer/ brand.

Please share.

CLV

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[Amitabh Bhattacharya]

Vishal

Attached PDS may give you an idea of expected sub-zero Impact properties of C-Steel filler alloys.   

Hope this helps

Thanks 

Amitabh 

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[sandeep kumar]

First of all, in FCAW wires, consumable manufacturer control the weld chemistry by the core filling formulation which control the toughness. So the results varies with manufacturers. You didnt specify the brand name. 

As per my experience, go with Kiswel brand manufactured in Korea (1st solution).

Further, as you specified that the lower heat input also didn't help you to achieve the toughness, the failures can be attributed to coarse grain ferrite/ pearlite in your weld micro structure presents in root and cap. You are able to achieve the toughness in center which is highly possible due to grain refinement by successive weld beads. For a improved microstructure you can go with argon mix as advised by Mr. Goswami as using poor CO2 will give high arc efficiency with increased heat input in the weldment and this will not reflect by general heat input equation.

Follow as stated above along with stringer beads, weld with maximum weld passes so you will have a better grain refinement. You can use controlled weld deposition for the capping pass.

regards
Sandeep Kumar

Welding Specialist

MSc.welding Engg, IWE, IWT

[Amit Singh]

Dear Vishal,

Please refer to the attached Test result of Kobelco Product DW-100KS ( E71T-9C J).

It can help you for your requirement. 

Regards.

Amit Singh