|
Posted by Ken Lamb on July 3, 2007, 2:54 pm
Please log in for more thread options
Greetings-
We have a project welding gussets and C channel made of 304SS to the
back of 1" thick x 90" square 304SS. The print calls for 1/4 stitch
welds. We are asking to use a continous weld because it can me a semi
automated process. This process will introduce less heat during the
welding and will make for a stronger and better looking product.
Our customer will give us approval if we thermal stress relieve the
parts after weld prior to machining.
We think this type of stress relieve is not beneficial to the part and
would rather not introduce this process to the part.
I need objective evidence to provide our customer that thermal stress
relieve prior to machining will not help the weldment.
I am not a welder I am a project coordinator with a manufacturing
background.
Is it better to thermal stress relieve this part after weld?
The semi automated welding process actually introduces less heat by a
lower temperature and moving faster than the manual welding process
used prior.
Thank you in advance,
Ken
|
|
Posted by Ken Lamb on July 3, 2007, 3:05 pm
Please log in for more thread options
> Greetings-
>
> We have a project welding gussets and C channel made of 304SS to the
> back of 1" thick x 90" square 304SS. The print calls for 1/4 stitch
> welds. We are asking to use a continous weld because it can me a semi
> automated process. This process will introduce less heat during the
> welding and will make for a stronger and better looking product.
>
> Our customer will give us approval if we thermal stress relieve the
> parts after weld prior to machining.
>
> We think this type of stress relieve is not beneficial to the part and
> would rather not introduce this process to the part.
>
> I need objective evidence to provide our customer that thermal stress
> relieve prior to machining will not help the weldment.
>
> I am not a welder I am a project coordinator with a manufacturing
> background.
>
> Is it better to thermal stress relieve this part after weld?
> The semi automated welding process actually introduces less heat by a
> lower temperature and moving faster than the manual welding process
> used prior.
>
> Thank you in advance,
>
> Ken
I apologize for posting to my post. I failed to mention we vibratory
stress relieve the weldments.
Thank you,
Ken
|
|
Posted by Ernie Leimkuhler on July 3, 2007, 8:12 pm
Please log in for more thread options
> > Greetings-
> >
> > We have a project welding gussets and C channel made of 304SS to the
> > back of 1" thick x 90" square 304SS. The print calls for 1/4 stitch
> > welds. We are asking to use a continous weld because it can me a semi
> > automated process. This process will introduce less heat during the
> > welding and will make for a stronger and better looking product.
> >
> > Our customer will give us approval if we thermal stress relieve the
> > parts after weld prior to machining.
> >
> > We think this type of stress relieve is not beneficial to the part and
> > would rather not introduce this process to the part.
> >
> > I need objective evidence to provide our customer that thermal stress
> > relieve prior to machining will not help the weldment.
> >
> > I am not a welder I am a project coordinator with a manufacturing
> > background.
> >
> > Is it better to thermal stress relieve this part after weld?
> > The semi automated welding process actually introduces less heat by a
> > lower temperature and moving faster than the manual welding process
> > used prior.
> >
> > Thank you in advance,
> >
> > Ken
>
> I apologize for posting to my post. I failed to mention we vibratory
> stress relieve the weldments.
>
> Thank you,
>
> Ken
OK so have the parts been TIG welded or Stick welded?
The 2 processes are both manual, yet very different.
MIG versus dual-shield is another problem.
MIG is a very fast process, but on stainless steel creates severe
localized distortion, and therefore stress.
Dual-shield is a hotter process, and does a better job of fusing the
material, while introducing less stress.
You need to clarify your processes.
There are some very experienced members of this newsgroup.
I personally have about 25 years of metals experience and I am a
certified weld inspector.
I have extensive experience welding and machining stainless steel and I
would want more info before rendering a judgment.
A benefit of stitch welds is that if a crack develops in a weld it can't
propagate.
On 1" stainless steel I do hope you are allowing for a preheat of the
weldment.
You also have not stated how or if you are dealing with post weld
passivation of the surface.
Passivation is a critical step of stainless steel welding if the part is
to have any atmospheric exposure.
MIG on 1" plate stainless steel is not something I would recommend.
Dual-shield would be my favored process.
Thermal stress relief will also help restore corrosion resistance of the
part.
Also are you using 308L, 308LSI, or 309L filler?
I answer these kinds of question several times a year for manufacturers
in the greater Seattle area, as a fabrication consultant.
|
|
Posted by Wally on July 4, 2007, 1:42 am
Please log in for more thread options On Wed, 04 Jul 2007 00:12:18 GMT, Ernie Leimkuhler
Ernie, your reply raised a couple questions. It would seem to me the
added heat of the dual shield would cause more distortion, not less.
Is there a reason why doesn't it? Not doubting you, just wondering
why.
Do the stitch welds have to have a break between them? If I stitch
weld and then come back and fill in to form a continuous weld, does
that defeat the stitch welding benefits?
Thank you, and I hope to be able to meet you one of these days, I'm in
the Bremerton area.
>
>OK so have the parts been TIG welded or Stick welded?
>The 2 processes are both manual, yet very different.
>
>MIG versus dual-shield is another problem.
>MIG is a very fast process, but on stainless steel creates severe
>localized distortion, and therefore stress.
>Dual-shield is a hotter process, and does a better job of fusing the
>material, while introducing less stress.
>
>You need to clarify your processes.
>There are some very experienced members of this newsgroup.
>I personally have about 25 years of metals experience and I am a
>certified weld inspector.
>
>I have extensive experience welding and machining stainless steel and I
>would want more info before rendering a judgment.
>
>A benefit of stitch welds is that if a crack develops in a weld it can't
>propagate.
>
>On 1" stainless steel I do hope you are allowing for a preheat of the
>weldment.
>
>You also have not stated how or if you are dealing with post weld
>passivation of the surface.
>
>Passivation is a critical step of stainless steel welding if the part is
>to have any atmospheric exposure.
>
>MIG on 1" plate stainless steel is not something I would recommend.
>Dual-shield would be my favored process.
>
>Thermal stress relief will also help restore corrosion resistance of the
>part.
>Also are you using 308L, 308LSI, or 309L filler?
>
>I answer these kinds of question several times a year for manufacturers
>in the greater Seattle area, as a fabrication consultant.
|
|
Posted by Ernie Leimkuhler on July 4, 2007, 12:47 pm
Please log in for more thread options
> On Wed, 04 Jul 2007 00:12:18 GMT, Ernie Leimkuhler
>
> Ernie, your reply raised a couple questions. It would seem to me the
> added heat of the dual shield would cause more distortion, not less.
> Is there a reason why doesn't it? Not doubting you, just wondering
> why.
>
Dual-shield is hotter than MIG, but the flux layer prevents the weld
from cooling as fast as MIG, which reduces the severity of the weld
contraction, and stress.
Preheating the base metal also helps to reduce the thermal shock of wire
feed processes.
Preheat and interpass temps are listed in reference books.
> Do the stitch welds have to have a break between them? If I stitch
> weld and then come back and fill in to form a continuous weld, does
> that defeat the stitch welding benefits?
>
Somewhat yes.
You would still get the benefit of reduced heat input, but cracks could
propagate from one stitch to the next, if they touch.
Back filling between stitch welds is commonly used on long seams on boat
hulls to reduce the distortion of the weld process.
The full process is back-stepping skip-stitches, but most of that has
been eliminated with modern pulsed MIG equipment, which allows
continuous seam welds without stitching at all.
> Thank you, and I hope to be able to meet you one of these days, I'm in
> the Bremerton area.
>
>
> >
> >OK so have the parts been TIG welded or Stick welded?
> >The 2 processes are both manual, yet very different.
> >
> >MIG versus dual-shield is another problem.
> >MIG is a very fast process, but on stainless steel creates severe
> >localized distortion, and therefore stress.
> >Dual-shield is a hotter process, and does a better job of fusing the
> >material, while introducing less stress.
> >
> >You need to clarify your processes.
> >There are some very experienced members of this newsgroup.
> >I personally have about 25 years of metals experience and I am a
> >certified weld inspector.
> >
> >I have extensive experience welding and machining stainless steel and I
> >would want more info before rendering a judgment.
> >
> >A benefit of stitch welds is that if a crack develops in a weld it can't
> >propagate.
> >
> >On 1" stainless steel I do hope you are allowing for a preheat of the
> >weldment.
> >
> >You also have not stated how or if you are dealing with post weld
> >passivation of the surface.
> >
> >Passivation is a critical step of stainless steel welding if the part is
> >to have any atmospheric exposure.
> >
> >MIG on 1" plate stainless steel is not something I would recommend.
> >Dual-shield would be my favored process.
> >
> >Thermal stress relief will also help restore corrosion resistance of the
> >part.
> >Also are you using 308L, 308LSI, or 309L filler?
> >
> >I answer these kinds of question several times a year for manufacturers
> >in the greater Seattle area, as a fabrication consultant.
|
| Similar Threads | Posted | | Re: Thermal Arc 351 | April 12, 2006, 10:58 pm |
| Weldment rust protection query | May 25, 2007, 3:57 pm |
| ? using a pull back ram to correct a weldment | August 23, 2008, 9:51 am |
| Thermal Arc 10xr | April 18, 2008, 1:30 pm |
| Feedback on new Thermal Arc TIG welders? | April 14, 2007, 4:47 pm |
| Thermal Arc 3 or single phase | April 7, 2008, 6:55 pm |
| Thermal Arc 300 GTSW Torch Connections | March 24, 2008, 10:13 am |
| Thermal Arc wire feed machines | April 12, 2008, 8:33 am |
| FS: Thermal Dynamics circle/straight plasma guide kit | August 9, 2008, 2:03 pm |
|
|
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap
>
> We have a project welding gussets and C channel made of 304SS to the
> back of 1" thick x 90" square 304SS. The print calls for 1/4 stitch
> welds. We are asking to use a continous weld because it can me a semi
> automated process. This process will introduce less heat during the
> welding and will make for a stronger and better looking product.
>
> Our customer will give us approval if we thermal stress relieve the
> parts after weld prior to machining.
>
> We think this type of stress relieve is not beneficial to the part and
> would rather not introduce this process to the part.
>
> I need objective evidence to provide our customer that thermal stress
> relieve prior to machining will not help the weldment.
>
> I am not a welder I am a project coordinator with a manufacturing
> background.
>
> Is it better to thermal stress relieve this part after weld?
> The semi automated welding process actually introduces less heat by a
> lower temperature and moving faster than the manual welding process
> used prior.
>
> Thank you in advance,
>
> Ken