Welding A992/A572-50

By Drake181 Date 07-19-2008 17:49

Hey guys. We are having major difficulty joining W14x256 A992 to 2" A572-50 base plate, In principal they are the same material.
The joint required is a full pen butt weld,welded from both sides ( TC U5 GF) in the flat position using FCAW.
We have used 300F preheats.E71 wire and 75%Ar 25%CO2 gas (for cleanliness)the surfaces have been cleaned back to bare metal.
The results are cracks throughout. cracking occurs at the base material and in the middle of the weld deposit on both flanges and web.

has anyone ever had any cracking issues using A572-50 or A992?

By aevald

Date 07-19-2008 18:03

Hello Drake181, forgive me if this sounds like a simple question, but is the wire that you are using rated to be used with the 75/25 gas? If you are using a wire that was designed to be run with CO2 only, the change to 75/25 could lead to a hard weld deposit that could be prone to cracking. One other consideration would be wire diameter, in some cases if you are welding on thicker sections and using a smaller diameter filler wire, yet you are running it excessively high on the volts and amps it can cause some adverse metallurgical issues. With the thicknesses that you have described in your post you should probably be using at least 1/16" diameter filler wire and not trying to press the upper limits of the volt/amp parameters. Something to consider. Best regards, aevald

By Drake181 Date 07-20-2008 01:48

One of the wire 's we have tried is Lincoln ultracore E71T1. Lincoln rep's tell me it can be used with either gas. We have been using .45 wire, due to the thought process that more runs = refinement in the grain structure. We tried usind a 1/16 wire with the mid range parameters as Lincoln recommend . . .it failed, Cracks close to the base metal as with most other welds.

By aevald

Date 07-20-2008 05:11 Edited 07-20-2008 05:22

Hello again Drake181, I just went to one of the sites that lists some of the Lincoln wires and their shielding gas requirements, confusing as hell. I looked at this site and you have to very carefully follow the exact wire description to verify whether this wire will allow the use of multiple gases or specifically a straight CO2 application. Check this out for yourself and see if it is indeed the correct wire/gas combination. Best regards, aevald

EDIT: you will need to scroll down quite a ways to find the Lincoln Ultracore 71, there are a few different Ultracore descriptions, all of them list the E71T-1, yet they have different additional descriptions following the initial numbers. Which one do you have?

http://www.dot.state.oh.us/testlab/applists/misc/Electrodes/electrodes3.htm

By 803056

Date 07-20-2008 18:27

Most flux cored electrodes (other than self shielded FCAW) are developed and qualified with carbon dioxide as the shielding gas. The argon rich mixes can result in weld deposits that are harder and more prone to cracking than the CO2.

CO2 shielding gas requires the filler metal to contain more deoxidizers than argon rich mixes. The elements not utilized for deoxidation increase the alloy content, hence stronger more brittle welds.

Best regards - Al