Preheat for Backgouge? Help me!

By Lang khach Date 10-27-2014 11:34

Hello All,
I have some questions about backgoue for higher strength Quenched and tempered materials(EQ47, EQ63...) . To avoid cracks, do I have to preheat before gouging? And there're some informations, standards or codes which notice that. Absolutely, I think preheat will use for thick plate, but I haven't yet found some details which related that. I am urgently, so anyone can give some advices.

Sorry about my English,

Kindly,
Tan

By Superflux (****)

Date 10-27-2014 13:25

Tan,

Preheat requirements prior to a thermal (Air Carbon Arc Gouging) backgouge "Should" be included in a well crafted procedure. It is often overlooked unfortunately. Production supervisors can see this as a waste of time and resources and if not stated in the procedure, they are not going to enforce this.
D1.1 does NOT address this directly according to my research.
The comments in the following link do however express mine and many others opinion.
D1.1 Table 3.2 will be the place to start.

http://www.eng-tips.com/viewthread.cfm?qid=290167

Since I am stating opinions, if it were an issue, I assume it would be a code requirement.
Double check your project documents to see if preheat is or not included. It very well could be required and hidden in there.

By welderbrent (*****)

Date 10-27-2014 13:44

Tan,

WELCOME TO THE AWS WELDING FORUM!!

John's last sentence is my main additional point, that is often found in your contract documents but not the applicable codes. I'll have to look later, but that application may be in a code as well. My memory just can't pull it out right now. But I know I have found it in the General Notes in Job Specifications many times. Usually preheat to 150°F minimum before carbon arc gouging or oxy-fuel torch operations is required.

I'll keep looking to see if I can reference my failing memory that it MAY be in a code somewhere.

He Is In Control, Have a Great Day, Brent

By Cumminsguy71 (*****)

Date 12-18-2014 03:21

So why would you preheat before......well, heating during gouging?

I am thinking it's because the steel is so thick that it may cause cracks in the material due to temperature differential? Am I on the right track? Read this post an another asking the same question and began to wonder why, wheels started turning.

Shawn

By welderbrent (*****)

Date 12-18-2014 13:05

Shawn,

Check out Henry's post responding to the current questioner. But, yes, the sudden and large amount of heat combined with the way many use an air arc with it coming on, off, on off, (at least when they first hit it) instead of a good steady arc can cause some negative metallurgical reactions.

But, the D1 codes do not deal with it.

He Is In Control, Have a Great Day, Brent

By welderbrent (*****)

Date 11-16-2014 22:52

That's the one I was looking for, but, it is also "in which the curved surface of the access hole is thermally cut" and "thermally cut surfaces of beam copes and weld access holes" in heavy sections. It does not apply to just any cutting or gouging of Heavy Shapes though that is where I have found it referenced in the contract documents was when the engineer wanted to extend the preheat to all cutting applications, usually on A913 Gr 65 WF columns.

He Is In Control, Have a Great Day, Brent

By 803056

Date 11-16-2014 23:35

No argument. It is the only reference to preheat prior to thermal cutting that I saw.

Al

By 99205

Date 12-20-2014 09:10

Well, I had to go find the yellow highlighter for that one.