Consumables for A217 WC6 (MIG + SAW) 1

[starflex]

Der All,

I am developing a repair procedure for a coal mill wheel. It is made with A 217 Grade WC 6 and some eroded parts need to be built up.

As the eroded section is not regular across the profile , my idea was to machine it (as minimum as possible) to create a regular profile first, and then use a combination of MIG (for the first runs) + Sub-arc (for the subseqneunt ones) to build up the missing material. The wheel can be put in a support to make it spin, so that the process can be fairly automated with the head of the subarc on top.

Rationale behind it is that we cannot do PWHT, we have limited pre-heat capacity (it's a fairly large component) and the SAW passes would temper the MIG ones and the SAW subsequents. Finally the part will be machined to restore the original profile, so that the final, untempered beams will be removed. Not the best solution ever, but the best we can do.

I was looking for some hints from you in terms of consumables.

Thank you!

 

[arunmrao]

I would use E 8018-B2 grade .

"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[metengr]

Use the GMAW equivalent and SAW wire/flux of what arunmrao mentioned above. Suggest you qualify the above weld procedure, if anything, to show the client you have thought about the repair and justified it.

 

[starflex]

Gents,

Thank you for your inputs. That's the direction I was looking at.

For the GMAW wire, I was looking at ER70S-B2L (we are not in creep range and maybe a softer material would help, considering that we cannot do PWHT). However, I cannot find the equivalent for the SAW (I found F8P2-EG-B2).. but I still kind of like the idea of having a "softer buttering layer". Maybe I am wrong.

I am definitely going to write a welding procedure and to qualify it. In terms of mechanical test, do you have any standard on top of your mind that I can use for cladding NDT & mechanical test?

 

[metengr]

No. Use ASME Section IX for WPS qualification.

 

[CWEng]

The B2 compositions are designed for PWHT (and usually preheat). If this is for wear resistance, why is the relatively soft WC6 being used? Why not use a filler metal that is more forgiving, but at least as strong as WC6 or stronger, such as ER80S-Ni1, ER80S-D2, ER90S-D2 and the matching SAW consumable?

 

[starflex]

Thanks guys.

@Metengr: I will, I was thinking in the same direction. Need to get my head around about how to do the test coupon (thickness & tests).

@CWEng: I am aware that te B2 required PWHT, that's why my first choice for the ER70S-B2L..that forgive a bit more in terms of PWHT. We will put a bit more runs on top, to machine them later on and have a tempered surface (left after the tempering rung). Basically, we wil use the temper beads and we will machine them out.

Why did they use that material in first place? I have no idea. Why am I using that material ? Because the client asked so. My first idea was doing laser cladding with a buffering layer and a hard surfacing on top, but the client insists to have a like-to-like material. Honestly, that part should not really be exposed to erosion(it's the first time they are doing this job after several years of service), as the blades (that actually are in contact the material) are made with Hardox. The 1.25Cr is just the support plate of the Hardox blades.

 

[starflex]

Gents,

Here I am again. I spent a bit of time on it. A bit of confusione between "weld build-up" and "overlay"...

QW-202.3 Weld Repair and Buildup. WPS qualified on groove welds shall be applicable for weld repairs to groove and fillet welds and for weld buildup under the following provisions:
(a) There is no limitation on the thickness of base metal or deposited weld metal for fillet welds.
(b) For other than fillet welds, the thickness range for base metal and deposited weld metal for each welding process shall be in accordance with QW-451, except there need be no upper limit on the base metal hickness provided qualification was made on base metal having a thickness of 11/2 in. (38 mm) or more.

Do I have to go with a test plate of 38mm min to qualify the weld procedure, with a V prep groove weld ? Is there any other way to qualify in a sound way the procedure (e.g. QW-453), that apaprently specify "wear resistant" and "corrosion resistant" ? I need to build up probably 10/15mm of missing material.

Thank you in advance!

 

[metengr]

You have two options - a weld build-up restores structural integrity to the component. A weld overlay is for wear or corrosion resistance and does not take credit for strength of the component.
With that said, since you are using welding consumables that are closer to the strength of the base metal, I would qualify a WPS using a groove weld and consider it a weld build-up.

 

[starflex]

Metengr,
It makes perfectly sense.
Thank you.

 

[starflex]

Second part of the question: qualifying the personnel.

This is the current situation:

and this is how I was thinking to proceed:

The welder and welding operator will be qualified anyway for the groove weld, but still, I am probably doing a second test coupon to demonstrate that they can achieve the desired results welding against a copper shim (used to re-create the profile and to protect the adjacent components).

I would go with a slotted plate that resembles the actual conditions: cannot really find anything specific in ASME IX, so I guess that if I do my due diligence (test base metal coupon that represent the size of the production part), plus liquid penetrant, 4 guided side bend test, hardnesses, macro.. I am covering pretty much the requirement.

Your call?

 

[metengr]

Looks good. Watch out for MIG because you could have LOF defects.

 

[starflex]

Yep, I know... that's the big threat. But being a 4 meters diameter wheel I cannot really propose SMAW or TIG for the root run...

I will try to stay a reasonably highish with the HI for the root run (around 1.8/2.2 kJ/mm) and for the filling / tempering runs I will try to adjust consequently (maybe 1.3 / 1.5 times).