Ss 310 welding

Date 04-16-2007 13:45

You need to be more descriptive of the type of cracking involved. And there is nothing inherently deficient with 310 in an application of high temp as long as the stresses are within the allowable.
Another thing is that the restraint against alloys of lesser thermal expansion could strain the weld to cracking. If microfissuring has occured, even at a amount generally not problematic, the thermal restraint, especially cyclic, could initiate cracking.

By chuck meadows (***)

Date 04-17-2007 02:52

310 should be able to withstand these temperatures if your heat input and interpass temperatures are within recommended guidelines. Heat input should be 1.0 kJ/mm (25.4 kJ/in) maximum, and the interpass temperature should be 100C (212F). 310 (fully austenitic) is more sensitive to hot cracking than, for example a 309L filler metal. So, the interpass temperature and heat input are very important.

By tom cooper (**)

Date 04-19-2007 16:34

Hi folks- I hope you don't mind if I join in on this question;
where would you find "recommended" max heat input values for SS? or any other alloy for that matter? Related to this question is another about technique - we have a couple of our aces who believe that the technique of "walking the cup" is a means to minimize heat input when working with SS, but we haven't use this yet since the technique is not specifically listed on any WPS. While we always monitor for interpass temps, we have never monitored V, A or speed. Should we?

By js55

Date 04-19-2007 17:11

Not sure the 'walking the cup' technique argument for reduced heat input is valid. Walking the cup by its very definition implies an oscillation/weave as opposed to a free hand stringer type technique.
Having said that, there is nothing that says walking the cup can't provide less heat input than a free hand, because heat input is based upon V/A and forward motion. Walking the cup is self limiting to a certain extent on forward motion whereas free hand can move about as fast as you can run your hand over the joint, but as an absolute it doesn't really matter. Adequate heat input limitations can be easily achieved by both methods.
As for monitoring V/A and TS, it is my opinion that it is unecessary for SS's, except for the usual spot verification by QC personnel for WPS compliance. I would control HI by limiting V and A on the WPS and not concern myself with TS.
That way its a simple process of a QC person passing by a power source or feeder and taking a glance at the meters.

By Lawrence (*****)

Date 04-19-2007 17:52 Edited 04-19-2007 19:33

I've never heard of a WPS limitation on cup walking technique in pipe welding application. On the other hand I'm with J55 when he mentions travel speed compliance... if you can walk the cup and comply with the travel speed limitations I see no ground to forbid it. Reducing heat? Thats a stretch... Controlling pipe distortion? I can see that happening as a competent cup walker may have a more predictable outcome time after time.

Personally, in restricted areas I find walking the cup with my more awkward hand a great benefit. I can walk the cup with my bad hand way better than if I was compelled to free hand with it.

Alot of welders (always an exception) can make more consistant cap contours with a cup walking technique.

I've worked for formen that demanded cup walking on Sch. 5 autogenous pipe welds. Never the other way around.

By js55

Date 04-19-2007 18:20

Lawrence,
Thats a good point on distortion. We have threads in here on distortion control. I don't know that the walkin the cup subject has come up in those contexts.
And I always preferred WTC. Never free handed unless, for whatever reason, I had to.

By Lawrence (*****)

Date 04-19-2007 19:37

Control is the key word here too :)

With stainless, sometimes trying to reduce/eliminate distortion is like banging your head on a wall. But if you can make the suff distort predictably, than you can take preemptive measures to make the finished widget comply with deminsion requirements.

I like walking the cup on pipe (when I get to weld pipe), everything else I do with GTA is freehand.

By ssbn727 (*****)

Date 04-19-2007 22:09 Edited 04-20-2007 05:04

Like you Lawrence, I like walking the cup with my so-called weak hand especially with a mirror because you have more control than mirror welding free-hand on pipe although, I've had to resort to both in the past.

Nowadays most of the pipe I weld is schedule 10 & rarely schedule 40 316Ti or 316L and schedule 40 Grade 2 Ti... On the butt joints (groove welds) I prefer walking the cup as well as when I'm welding the slip-on or ANSI flanges... The branch fillets (no weld-o-lets here) on the smaller ( 2" or less I.D.) schedule 10 diameter pipe has such a fit-up due to the hole diameters we drill enable us to contour the branch fitting so that the I.D. wall mates with the appropriate hole wall leaving plenty of "meat" where the outside fillet weld is to be deposited & still have CJP... As a result, my free-hand welds are superior to walking the cup & HI is much less (we've got a real nice heat sink set up that virtually eliminates any type of movement or distortion but, my company wo'nt let me share the details!) + they're completed in much less time so long as I've got the parameters set just right so that I can "fly" around the joint with my pedal to the metal and I remember that "once I'm halfway around the track so to speak, I can start to let off the gas and get ready to coast a bit until I get towards where I started!"

Also, once I'm over the place where I started - I slowly ramp down the current myself with the (gotta love a foot control or a torch mounted amptrol!!!) foot control which is hard to do if one is welding superheater tubes in a boiler because, "They Aint no foot pedals in a boiler house Son!!!" "You've got to use yo eyes, yo head & hands Son!!!" This is where walking the cup really helps and you can "move like the dickens" around pipe if you focus on what going on where you're welding... Now an on-off switch connected to a power source with a downslope control is a pretty good option to have in a boiler house as most tube welders will attest, but that's still was considered a rare luxury when I was a tube welder back in the day!

Bottom line is, most pipe joints can be welded either way but "walking the cup" gives you better puddle/penetration control in most situations although there are some situations whereby free-hand welding with GTA results in superior deposits than one would have with WTC! This has been my experience but, others may disagree -big deal!!! Especially if the HI is within specs, every other parameter is followed and the weld pases NDT!!! NEXT!!!

Respectfully,
Henry

By tom cooper (**)

Date 04-20-2007 09:23

Henry-
you said "(we've got a real nice heat sink set up that virtually eliminates any type of movement or distortion but, my company wo'nt let me share the details!)" - You can share with us, I promise we won't tell! LOL.

Thanks Chuck - that info will be a big help to us.

I may have misstated our concern with WTC technique - our WPS do not forbid us to use it, but most often they will dictate stringer or weave (or either when appropriate) and we just were not sure if WTC was generally accepted as a weave. We have to get more informed that's all. And send some of the younger guys out for training!!! But thanks for all the advice and ideas.

Have a good day.
T

By ssbn727 (*****)

Date 04-20-2007 15:52

Hi Tom!

First of all, let me "Weldcome" you to the AWS forum!

Second:
The reason I mentioned why the company I work for does'nt want me to share the particulars is because of a worry that our competition will also get wind of it and enable them to offer our customers a product of matching quality at a competitive price or possibly at a more advantageous price which would result in a loss of profit margins from our current rate.

I can tell you this... The system we use was designed in-house & of a proprietary nature that originated in Germany yet, modified/improved here in the US for maximum efficiency.

The only clues that I can reveal to you are a few key terms that were used in the design: water cooled torch design adaptation into a working, easily removeable heat sink/purging gas delivery system which removes heat build-up both internally & externally, Aluminum & Brass and proper fixturing to compensate for movement/distortion... The rest you'll have to figure out on your own - which should'nt be too difficult to sort out.

Respectfully,
Henry

By chuck meadows (***)

Date 04-19-2007 21:52

Tom,
Send me yoour e-mail address and I will send you the Avesta Welding Manual and it will give you recommended interpass temps and heat input, along with a great deal of data concerning stainless steel welding. chuck.meadows@avestawelding.com

Chuck

By Shane Feder (****)

Date 04-20-2007 01:30

Hello guys,
The only minor thing that I think wasn't touched on was arc length.
WTC allows better control of the arc length, thereby giving more control over the volts, thereby giving better control of the heat input.
WTC can also give a more uniform travel speed which again would give better control of the heat input.
The differences in volts and travel speed may only be miniscule but what is the most common thing said about a WTC weld done by an experienced welder "Looks like it was done by a machine". And generally a machine will give more consistent results than a manual weld.
Regards,
Shane