How to calculate resistance of a weld of a bolt welded to structural steel?

[user277418]

Hello

I have a bolt M20 8.8 fyb=640MPa that should be weld to a structural steel S355 fy=355MPa. How to calculate a thickness of the weld?

Is it permissible, in general, to weld bolt steels by any other method than like Nelson studs welded?

Best regards

 

[kingnero]

I would not weld 8.8 bolts, they're high-strength and welding will probably ruin their mechanical properties.
I have heard of weldable nuts, most likely weldable bolts exist as well (???).

as for calculations, it's just a circular fillet weld. Check shear and tension, combine them and check for unity (to fu of the weaker material).

 

[Tmoose]

I agree with the King's concerns about welding tampering with the bolt's mechanical properties in unexpected and detrimental ways.

What load is the bolt subjected to, that the weld must resist??
Arbitrarily matching the strength of the weld to the structure may be completely un-necessary.
For instance do you need to :
- retain the bolt
- allow tightening just the nut ? A couple of snips of bar stock welded strategically to the structure snug against the bolt head can be quite effective at prevent rotation and allow easy replacement of the bolt later.
- something else altogether

https://secure.amesperf.com/qilan/D...7DC&order_number_e=MzE1MTE1NA== &web_access=Y

 

[user277418]

Thank you for quick reply

I would not weld 8.8 bolts, they're high-strength and welding will probably ruin their mechanical properties.

I agree with the King's concerns about welding tampering with the bolt's mechanical properties in unexpected and detrimental ways.

I had a feeling that there should be some peculiarity.

I have heard of weldable nuts, most likely weldable bolts exist as well (???).

Can you tell some details about it?

What load is the bolt subjected to, that the weld must resist??

Tension 100kN and shear 37.5kN in two directions

 

[klaus.]

DO NOT weld a high Grade bolt ...never ever !!!!!!!!!!!!!!!

 

[kingnero]

Define "high grade"
Would you allow 4.6 bolts/gr4 nuts to be welded?
There you have a specified minimum yield strength of 240 MPa, similar to most construction steels. Not exactly high grade I'd say.
However, I still don't like to see them welded.

Can you tell some details about it?

Google for "weld nuts and bolts" yielded many results.

 

[user277418]

Would you allow 4.6 bolts/gr4 nuts to be welded?

it should be fine, if it is a PD stud M20 4.8 welded by stud welding method

 

[kingnero]

PD studs are designed to be welded, I'm sure the chemical composition and heat treatment is considered for this, unlike "normal" 4.6 bolts.

 

[Tmoose]

Quote (Tmoose)
What load is the bolt subjected to, that the weld must resist??

OP replied "Tension 100kN and shear 37.5kN in two directions."

Are these forces applied once, or alternating.

1 - I can believe the BOLT may be subjected to 100kN tension, but unless there is a gap under the bolt head after welding, I don't think the WELD would see any of that.

2 - Is the 100 kN bolt pre-tension/installation clamp load? If so, I guess there is a possibility the bolted components will slip, and the bolt body will end up resisting the shear forces, and the head weld will be the link to the component to which it is welded.

 

[klaus.]

Define "high grade" glasses

usually in Europe high strength bolts are 8.8 or 10.9
You cannot weld these bolts ...never ever

Lower grade bolts can maybe be welded ...but better to user weldable bolts or stud bolts

 

[user277418]

You cannot weld these bolts ...never ever

Can you send any refer to standard or book where this is stated or point approximately where to search it? I believe you, but to say it to my chief I need some heavy arguments.

 

[kingnero]

Just ask your supplier for the material certificate of any 8.8 or higher grade bolt, and analyse the chemical composition and heat treatment. The carbon equivalent should already tell you a lot about the weldability.

 

[drawoh]

user277418,

High-strength bolts are heat treated. When you weld them, you anneal them and they are not high-strength anymore.

--
JHG

 

[bridgebuster]

One thing about weldable nuts: They exist; the problem is trying to find them.

 

[BrianPetersen]

A google search of "m20 weld stud" turns up a number of possibilities. If you HAVE to use the bolt that you have on hand for whatever reason ...

What precludes sticking the bolt through a hole through both parts and putting nuts on the other side? (i.e. make a normal bolted connection)

Can't get to one side of the connection? What precludes tapping threads in one of the parts? Or making an access hole to be able to get to the bolt head?

Or you can get to the connection to stick the bolt through, but it wants to spin and you can't get to it to stop that once it's assembled? Stick the bolt through a through-hole, and weld a bar adjacent to one of the flats of the bolt to stop it spinning.

 

[klaus.]

Can you send any refer to standard or book where this is stated or point approximately where to search it? I believe you, but to say it to my chief I need some heavy arguments.

You do not need a code...all you need is common engineering sense and some knowledge of steel materials ....

 

[user277418]

Thank you very much for your replies!

I checked the chemical composition for the rod. The carbon content up to 0.55% + Q/T. In the end, there would be a hole in a structure with 2 additional nuts.

Best regards to all of you.