WELDING - Bolt 8.8 and S355

[ALANIT]

thread725-449248


Hello,

Since I've found a thread which treated this issue but it is closed now, I'd like to readress this question and add some reflections.

In fact, I've digged the EN ISO 898-1, EN 683-2 and EN 10025-2. I've found for example that the S355, by the IIS formula, that the equivalent carbon is about 0.52 %, and by the same formula some steels, which are suitable for 8.8 class, seems compatible with that (ex.: 25MnB5) and have even a smaller equivalent carbon amount. However, the 25MnB5 integrates BORE in 0.005 % max.

Why it should the 8.8 bolt should not be weldable to the S355 steel, with pre-heating? I'm not a weld expert, and I've always heard about to NOT DO this, but I'm asking: Why ? It seems that it should be possible, with the adequate precautions.

 

[ALANIT]

Hello to all and many thanks for your active participation, it is really great!

@desertfox: the article you linked is very interesting. I'm not expert of US steel grades, but it seems that exists some steel bolts with an high enough elastic limit that in case of necessity can be welded. If I'm not wrong, the stress limit is similar to S420 (ex. A307), so it confirms the existence of steels that have a fyk > 400 MPa and a internal structure that are not affected by weld temperatures.

@r6155: I never thought about test coupon in weldings, but in fact it is a great idea. However, I'm not in charge of site aspect so I will not be able to do that. I have to show a design that can be effectively and easily realized in workshop and then delivered on site. All heat treatment and welds are not up to me, but I have to make specifications that will not create problems to the others engineers (I'm not in direct contact with them, since we are from different companies). There will be surely a welding engineer that will follow equipment realization, but I don't want that he finds impossible specifications.

@mfgenggear: even if I don't work with sheet metal, the video is really interesting. As I said to r6155, I did not thought about tests (because I didn't know it was a common practice) but I think that's an intelligent approach. However, all welds will be performed in a controlled ambient by specialized workers before site delivery, so heat treatment is almost certain. I think that with the S420ML steel round bars as bolts no problem should be present.

 

[r6155]

@ ALANIT
We have little information about your design.
Please can you tell us what this anchor bolt is for? Is it for vertical or horizontal pressure vessel?

Regards

 

[DekDee]

Maybe the statement Never, Never, Never weld a fastener or bolt should have been qualified with never weld a fastener or bolt of Grade 8.8 and above.
I am on a structural project where the Contractor is welding thousands of Grade 4.8 threaded studs daily.
Qualified welding procedures coming out my ears so I cannot see any issue with it.

 

[TugboatEng]

Anything can be done if you can produce a qualified procedure. Codes and standards exist to save you money on creating qualified procedures.

 

[3DDave]

Can you use pucks with recesses for the heads and weld the pucks in place to retain the bolts?

 

[r6155]

See AWS D1.1 2020 Structural Welding Code-Steel.

Regards

 

[ALANIT]

Hello,

@r6155: it's an horizontal pressure vessel. There is a baseplate casted in concrete and then the equipment is bolted on this baseplate. The anchor bolt which I'm talking about in this thread is the headed stud that will be inside concrete and CANNOT pass through the baseplae, so it's welded. This design has been proposed/accepted long time ago by someone else and I'm finalizing design. I've understood why 8.8 grades should not be used, it is mainly the mechanical degradation of steel bolt characteristics, which will be much lower and unknown. Even if probably there will be margin, since it's bad practice and it is very hard/impossible to justify, it will not done. If needed, we will use an higher steel class for welded bolts like the S420ML or 460, which do not present any problem for welding as 8.8 grades. However, I'll look also in AWS D1.1 2020 document. Thanks!

@DekDee: I don't know the procedures that are in place for realization. I'm pretty sure that the assembling company has all the needed experience, since it is one of the most known for steam systems.

@TugboatEng: yes, but if I don't understand the reason why something is inside a code, I must investigate, always.

@3DDave: I've seen that some weldable nuts exist, but my bolts should be welded on the bottom face of baseplate, and they cannot pass through...

 

[saplanti]

ALANIT,

I suggest to use low strength ductile bolting material (such as 4.8, 5.8) for anchor unless the connection requires high tensioning force.

In case the pressure vessel is vertical and high you may need prestressed high strength anchor bolts for high tensioning, so I suggest talk to Dywadag for your options but you may need hydraulic tensioning, and a bit large space above bolts with bolt extension.

In case the vessel horizontal you’d better use ductile anchor bolts which are more manageable.

In your particular case there are some problems with bolt welding onto the plate. Welding itself may not be problem with ductile bolt materials, however the behaviour of bolts and welded connection on to the plate may not be suitable with the application. In case you are seeing there will not be a problem under the loads, and you can provide an adequate calculation, it seems acceptable. Please be careful with plate behaviour as well, you may/may not know how it was attached to the steelwork in the concrete foundation.

 

[3DDave]

Picture a counterbored washer. Put the bolt though the washer with the head inside the counterbore. Then place that counterbored washer with the bolt extended upward and the head of the bolt against the beam. Weld the washer made of whatever material seems reasonable to the beam.

If the bolt has a hex head, then instead of a counterbore cut a slot to match that hex width.

Is that what you assumed I meant by "puck"? Because that is a puck shape with the bolt extending though it.

 

[kingnero]

Up until 4.8 bolts, material is similar to what you are suggesting (S420/460). Werkstoff no. 1.02XX. Weldable if you (really) KNOW the base material.
Going a bit higher, they start using higher carbon steel. Sometimes with heat treatment. Werkstoff 1.11XX Don't weld those!
8.8 and up are "exotics" (CrMo's) and using weird (and non-weldable) alloying elements like Boron. There is also often(always?) a heat treatment after coldforming the threads. Again, welding is NOT advised! Werkstoff 1.5xxx, 1.6xxx and 1.7xxx

 

[r6155]

Anchor bolt tensioning is not required for horizontal pressure vessel, so SA-307 low strength bolt is enough, 25.4mm diameter is normal. I do not agree to weld any bolts.
If a weld is made, it will be full penetration, with all the required conditions.
See Process Industry Practices -Structural- PIP STE05121 Anchor Bolt Design Guide (my copy is 2008 edit.)

Regards

 

[mfgenggear]

again testing is a must