RELIABILTY OF SAW PROCESS FOR TP 316 L HEAVY WALL PIPE 2

[yergul]

I am using 2 different welding proces For Heavy wall (TP 316L) pipe welding(SAW and GMAW)
both of them semi-automachine

Due to high heat-input of saw proces ,it takes very long time to complete pipe welding

is there any one can advice me how i can decrease welding time for saw ?
(except to use high thick welding wire))

I am thinking to use air cooling for this ?
is it effect weld quality?

Weld paremeter and consumption materials are as follow

AWS-NO:ER316L
F-NO:F6
A-NO:A8
Size of Filler metals:2.4 mm
Electode -Flux class:neutral flux(esab)
AMP RANGE:370-380
VOLT RANGE:24-27
TRAVEL SPEED:31-32(cm/min)
HEAT INPUT:1,7/2(kj/mm)

 

[mcguire]

Yergul
We have better experts in welding than me, so I'll hope they respond to the primary question, but I would caution you to specify the base metal to have as low a sulfur as you can, at least below 0.003%. Sulfur doesn't benefit SAW and it does screw up corrosion resistance in the unmixed zone of the base metal, lowering the critical pitting temperature by up to 20C if you cannot post weld anneal or thorougly pickle.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[metengr]

I would evaluate switching to a narrow groove welding process, in lieu of SAW. The narrow groove welding is available and we have used it on several large (thick walled) piping jobs. The process is performed using auto-GTAW. The side wall of the weld prep is typically 2 degrees or less for the full thickness. The maximum depth of penetration using narrow groove welding is limited to about 6".

A second option if you can do this is to use demin water backing during welding. After the root and cushion passes are completed, you can fill the pipe with treated water and attempt to dissipate heat. I had seen this concept used for AISI Type 304 ss nuclear plant recirc piping in service. The concept was called “heat sink welding”, and actually resulted in local compressive stress formation on the ID of the pipe adjacent to the HAZ. This resulted in less susceptibility to IGSCC in service.

 

[weldtek]

metengr,
do you mean .6" for depth of penetration?

 

[metengr]

weldtek;
No. The narrow groove welding process is rather unique and can be performed on weld joints up to 6" in thickness. The torch head is a special design with a boot that can direct shielding gas into the narrow groove weld joint. The weld joint itself is typically a J-groove geometry with 2 degree sidewall angles.

This process was specifically developed for welding heavy wall components to reduce weld distortion, weld metal volume (total arc time) and heat input. GE has a similar process called "fine line welding".

 

[weldtek]

Maybe I'm confusing depth of penetration with thickness of the weld joint. I can see a J groove with 2 degree bevel, providing adequate access to the root, but then the depth of penetration required for a full penetration weld would just be the thickness of the land. Am I confused or what?

 

[metengr]

No, you are not confused, you are correct. The maximum depth of penetration I was referring too in the above post was the stick out length of the tungsten electrode in the weld joint for weld joint thickness, and not the depth of weld penetration at the root.

 

[stanweld]

yergul,
Your main concern regarding maintenance of a low (300F-350F) maximum interpass temperature and the necessity to halt welding after each weld pass to permit cooling before resuming the next weld pass can be mitigated with water cooling as described by metengr or by air cooling. I have used these techniques for over 30 years with excellent results.

To further enhance production, you may wish to explore narrow groove, SAW welding with square wave AC power supplies.

 

[weldtek]

My experience with 'J' groove welding has led me to believe that it has certain advantages as mentioned above, as well as very consistent root penetration, however, one of the drawbacks is that it is difficult to prepare the joint edges. We typically machined the prep and that added cost, and for us time, because we had to send them out to a local m/c shop. There are certain applications though where it is the best option, such as in making critical one sided butt welds in aluminum. It may very well be the way to go here too, but I tend to favor filling the narrow groove with SAW after the root is welded. As noted above forced cooling should not compromise material properties.

 

[yergul]

Could u please give me more detail about that u meantioned norrow grove in saw process?

Our heavvy wall pipe joint desings are typical and in accordance with in ASME B 16.25

Over 22 mm wall thickness compound bevel angles are 37.5 and 10 degree and I cant change them

We use piping up to 32 " diameter and up to 48 mm wall thickness

 

[stanweld]

yergul,
Suggest contacting Lincoln Electric. Most of the original narrow groove welding SAW work was done in Japan and was used for much thicker application than yours, but Lincoln has AC controlled wave power supplies that should prove effective. I doubt that it will prove highly cost effective in your application, though, due to higher equipment costs.