Repairing cast A351 Gr. HK40 baffle plate

[QCJT]

Admin please delete the duplicate of this post submitted earlier without a subject.

Hello all,

We are revamping some old ethylene furnaces. A baffle plate (18mm thick casting - ASTM A351 Gr. HK40) has broken loose in the Hot steam superheat pipes area of the furnace above the firebox. So for being able to pull the new hot steam tubes in place our construction wants to have an ad-hoc solution to the issue by basically "glueing" the baffle plate together. I'm saying glueing meaning welding but without any proper assessment, WPS/PQR and not even consulting for a proper filler material. So they just used what was at hand from fillers and that was ErCrMo-3... 65% Ni... The ASTM recommends to use matching filler for casting repairs but in this case we have 65% Ni of the filler against 20% Ni of the plate... I'm not a welding engineer or metallurgist but something is telling me that this isn't right.
However, I understand the urgent need for them to be able to pull these pipes on time and to finish the project on schedule... as usual - our client doesn't seem to care (as we are providing them Mech. guarantee for 2 years at least). So we are welding without WPS/PQR and client approval... They said they'll preheat to 200 Deg C (in order to avoid the need for PWHT). Unfortunately we do not have Er 310H consumable available here, which I think would be best to be used in this case. What we have in stock besides above is Er 308H, ErNiCr-3.

Please tell me:
- what would be the best suitable material from the available ones in our stock?
- if we preheat to 200 C, do we still need to do PWHT?
- Any other thoughts?

Thanks to all in advance

 

[metengr]

Preheat is unnecessary. Based on what you have on-hand, I would use ERNiCr-3.

 

[arunmrao]

HK 40 grade casting is difficult to weld, as the carbon content is high. I am not familiar with the atmosphere of the furnace. Hope,it has not resulted in any carburising of the plate rendering it brittle.

Using a higher grade Ni electrode is helpful in reducing cracks during welding.

No preheat required.

Caution, my comments are general in nature to HK40 grade casting, but not specific to parts in ethylene furnace.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[QCJT]

Thanks guys.
Arunmrao, what do you mean by a higher grade Ni electrode? Like ErCrMo-3? It has 60% Ni - is that what you mean?
Metengr ErCr-3 was also my suggestion from what we have at hand. However, since they are going to be pulling 16 meter pipes through this plate I hope this structure will withstand this. Again, this is totally of the records / ad-hoc solution (at least our guys try to make everyone see it that way).
Arunmrao, definetly carburising has taken it's toll on the plate but a weldability test showed no cracks using ErCrMo-3 filler with 200 deg preheat.

 

[metengr]

The ERNiCr-3 filler metal being nickel-base will help you regarding weldability because nickel is an austenite stablizer and helps with dilution issues with base material. It is not a long term solution because matching filler material would be the obvious choice given high temperature performance. So, what you have on hand will work.

 

[arunmrao]

Sorry for the delay. Blame the New Year revelry! . Agree that higher Ni containing rod will be beneficial.

The fact that a 18 mm thick casting has cracked must ring alarm bells. The casting has possibly embrittled due to carburisation and exposure to high temperatures.

You may drop test a new 18mm thick casting ,it will not crack.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[QCJT]

Metengr, is this a correct understanding that the higher the nickel, the better? In this case why not use ErCrMo-3 which has higher Ni content (60%) than ErCrNi-3?

 

[metengr]

QCJT;
You can use the higher nickel-base filler. However, you stated earlier what you have on hand for weld repair. If you decide to purchase ERNiCrMo-3 for repair I would purchase the matching filler metal as mentioned in your earlier post.

 

[stanweld]

Generally, HK40 is welded with E/ER310. High nickel filler metals are more resistant to carburization but the HK40 baffle plate is subject to an oxidizing environment and depending on the operation of your furnaces the expansion coefficient mismatch may lead to thermal fatigue cracking. The HK40 may also have sigma; one way to check for sigma is to hammer a pointed punch into the HK40 casting and PT for the indentation. Cracking eminating from the indentation is evidence of sigma. If sigma is evident, replace the part.

 

[arunmrao]

stanweld, agree with your comment of replacing the part. The casting in my opinion is embrittled .

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year