CJP T-joint on #8 - Don't know where to begin!

Date 02-21-2008 12:56

Totally clueless on this, we can't even get started.

Need a new PQR for a D1.4 requirement. The production joint will be a CJP for #8 Grade 60 rebar tee'ed into flat steel plate (I believe the plate will be ASTM A 108 grade 1018 to 1020).

Will be faced with high production rate so we need speed - I am thinking either FCAW or a pulsed MIG procedure. What would your preferences be?

The rebar specs or any subsidiary document give me no info on material composition. NONE!! Since I will be working with high tensile (UTS 90ksi) ASTM A615 grade 60, I presume there will be a high carbon content? What about the dreaded sulfur? Should I be thinking about using a high manganese wire for this?

What about preheat?
Post weld heat treat?
Interpass issues?

To make the CJP on #8 bar there will be about a 7/16 (minimum) single sided bevel all around:
Is there a backgouge type situation that I have to think about? i.e., when we weld the root do I do this in two parts with a backgouge in between? or should I not worry about this?

Any advantage to stick weld the root and then fillout with FCAW or MIG?

After the root, how many passes should I be able to fill out the rest of the 7/16 bevel?

My single advantage is that this will all be portable assemblies built in the shop.

Thankyou for helping get me started.

By Lawrence (*****)

Date 02-21-2008 13:34

For process, I'm a big fan of Gas Shielded FCAW..

It will weld in any position.. It will provide a deeper penetration cross section than SMAW and it is WAY faster.

With the variety of filler diameters now available for FCAW you can make some pretty good sized fillets in a single pass.

By Bob Garner (***)

Date 02-22-2008 21:22

Can you talk them into specifying ASTM A706 rebar? It's more "weldable".

By 803056

Date 02-27-2008 02:59

Go with a double bevel. Weld the first side, back gouge and weld the second side.

Do you have a copy of D1.4? I'm traveling, so I can't do the leg work for you.

Make sure you have CMTRs for the rebar received so you know what you are dealing with. If the sulfur is more than 0.04%, make sure you use a high manganese filler metal. Compare the deposited weld metal chemistry for several manufactures to get the right balance of manganese. The manganese should be 10 times the sulfur content. You may have to specify a specific manufacturer and trade name for the filler metal to get what you want. Not all electrodes are created equal.

For preheat; use the higher of either D1.4 or the calculated preheat using the annex of D1.1. If you elect to use the annex of D1.1 assume you have medium restraint condition and a H2 condition if you are using SMAW (EXX18) or FCAW with low hydrogen characteristics. Not all FCAW electrodes meet the low hydrogen requirements, i.e., 16 ml [H] /100 g of weld deposit. Even the standard H16 may be too high for the material you're working with. The strength of the filler metal can match the strength of the lower strength material being joined. You will have to qualify the procedure, so you will be able to verify the minimum tensile strength is met. I would weld the rebar to a plate, one rebar to each side of the plate so that you can evaluate the joint detail, filler metal, etc.

Best regards - Al

Attachment: RebarPlateRebar26Feb08.wmf (2k)

Attachment: RebarPlateRebar26Feb08.dwg (23k)

By tom cooper (**)

Date 02-28-2008 20:42

Thanks for the advice Al. And we are getting the material spec changed! so we will be getting better quality A706 to start with.

By 803056

Date 02-29-2008 04:59

No problem. The advice is worth exactly what you paid for it.:)

Best regards - Al