Well, if nobody has "Weldcomed" you yet then may i be the first... WELDCOME RICHARD! To The Worlds' Greatest Welding Forum of The AWS!!!
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HELLO HENRY AND HAPPY AGAIN TO JOIN THE AWS TEAM.....
Okay then... Many questions come to mind from your initial query so I'm going to ask a few if you don't mind so you can help us to fill in as many details as possible...
1.) What is the governing welding code or standard for this job? Are you working from a WPS? Does the WPS state that you must use FCAW? THERE IS NO WELD CODE/NOTES THAT SAID WE MUST USE FCAW
2.) What position is the welding? Any out of position welding involved? Are you thoroughly cleaning each pass from the root pass up to the cover pass after each weld deposit? FLAT POSITION. THAT IS THE ISSUE CLEANING THE SLAG. THATS WHY I WOULD LIKE TO USE A SOLID WIRE
3.) Is this a repair? Why do I ask this? Because you wrote: "4140 base 12" dia. 1' thick. Weld v-groove is approx 5/8" deep and 5/8"wide using multiple passes." Also, what is the length of the weld groove? NEW PART. IT IS A DIAMETER>WELD DIA APPROX 6-8 IN.
4.) On which material is the weld groove? BOTH - THE V-GROOVE IS IN THE CENTER OF BOTH MATERIALS. THEY HAVE A FLANGE ON THEM.
5.) Why are you using FCAW when you could be using GMAW Spray transfer instead in order to eliminate your slag removal problem in the first place? Is it because it's an out of position V groove? Why not use another process instead? I AM FAIRLY NEW TO COMPANY - I THINK THE OLD SPEC CALL OUT IS FOR E-7018.
THAT IS WHY WE WENT TO FCAW. WE CAN USE AN OPTIONAL SOLID MIG WIRE RECOMMENDED FOR 4140 TO 1045. WE ARE APPLYING PREHEATS AND SLOW COOL. CAN YOU PLEASE RECOMMEND WIRE AND PREHEATS. YOUR THOUGHTS ON USING ER70S-6 WIRE.
6.) How are the 2 members connected or are they separate from each other? Do you have a drawing or a sketch? A picture is like quite a few words explaining much more at times...NOT SURE ON HOW TO ATTACH A SKETCH.
7.)When you say pre-heat temp of 500 degrees F slow cool, what is the maximum interpass temp? And is there Post weld Heat treatment (PWHT) afterwards? CONSTANT TEMP OF 500F THROUGHOUT WELD PROCESS WITH TORCH AFTER WELD WE COVER PARTS WITH HEAT BLANKET.
8.) What are your welding parameters (voltage and current and what diameter wire are you using as well as your shielding gas if any and what are your gun parameters such as the contact tip to work distance, etc...
9.) Why are you using FCAW instead of GMAW Spray transfer?
10.) Why are you using FCAW instead of GMAW spray transfer or even GTAW @ a higher than usual current and the appropriate rated torch with 1/8" dia filler wire instead?
There's so many more questions to post but I'll just leave the 10 I posted in order to get a slightly better visualization of what type of actual job this is and possibly understand why FCAW is being used in the first place because the use of a different, non slag-producing process would instantly eliminate your problem it it is indeed slag that's remaining on the surface of the weld deposit... And if this is your only problem with this job.
Respectfully,
Henry