Tube to Tube sheet welding, Orbital welding parameters for header box

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orbital

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Apr 9, 2020, 12:24:02 AM4/9/20
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Guys i am developing weld procedures for automated orbital welding and having trouble trouble with achieving required hardness.
SA-516-70N 2"Thk tube sheet / SA-179 1"OD x 6"Lg Tubes different wall thickness. Preheating 400 interpass 600 F

I am having isues with hardness on the heat affected zone. The criteria to meet is 248 Hv10 (vickers). Especially at the Haz zone iam getting 300 vickers.
Anyone have experience in tube to tube sheet welding can offer some suggestions that will be great.

My best results were in 0.095 wall thickness where HAZ readings were close to 250 still failed becauseit was marginally over. 0.065, 0.83 failed with HAZ hardness averaging at 300.
Best reagrds
Tesh

d...@btinternet.com

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Apr 9, 2020, 6:31:09 AM4/9/20
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Try a slower welding speed and a closer arc length.

Regards, 9 4 2020.

David Harvey

james gerald

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Apr 9, 2020, 7:05:02 AM4/9/20
to 'dwh@btinternet.com' via Materials & Welding
Problems related to Hardness may be due to High Heat Input or preheat being applied not properly (temperature is OK) you may look at the option of reducing the cooling rate or checking at the Carbon Equivalent

Thanks & Regards

J.Gerald Jayakumar




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Vinay Thattey

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Apr 11, 2020, 3:11:51 AM4/11/20
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Yes. I agree kindly check CE .

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George Dilintas

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Apr 12, 2020, 12:20:36 AM4/12/20
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Higher hardness could mean:
Higher residual stresses
Martensite formation
The most probable cause are Higher residual stresses. 
To reduce the residual stresses are following options:
1. Increase preheat. You may try 100degC
2. Decrease interpass temperature. You May try 150 degC
3. Decrease heat Input by shortening the arc or Increase welding spead

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Ahmed Osman

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Apr 15, 2020, 2:28:55 AM4/15/20
to Materials & Welding
- check the hardness of BM away from welding and what Is the welding HV values ?
- HAZ prosperities mainly related to the base metal 
- your base metal SA516 in normalised condition .. after welding the mech. priorities gained by heat treatment is lost unless u keeping the transformation temp. and cooling rate as the original treatment condition
- any way .. as much as u can try to increase HI for getting the lowest cooling rate 

best regards

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orbital

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Apr 28, 2020, 11:37:18 AM4/28/20
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Harness of BM: attached pic's for 0.65,0.083 & 0.095. I am doing something right on the 0.095 W as previously mentioned because it is pretty close to the 248 hv requirement. Readings attached.


On Wednesday, April 15, 2020 at 1:28:55 AM UTC-5, Ahmed Osman wrote:
- check the hardness of BM away from welding and what Is the welding HV values ?
- HAZ prosperities mainly related to the base metal 
- your base metal SA516 in normalised condition .. after welding the mech. priorities gained by heat treatment is lost unless u keeping the transformation temp. and cooling rate as the original treatment condition
- any way .. as much as u can try to increase HI for getting the lowest cooling rate 

best regards

On Thursday, April 9, 2020, 07:24:00 a.m. GMT+3, orbital <sati...@gmail.com> wrote:


Guys i am developing weld procedures for automated orbital welding and having trouble trouble with achieving required hardness.
SA-516-70N 2"Thk tube sheet / SA-179 1"OD x 6"Lg Tubes different wall thickness. Preheating 400 interpass 600 F

I am having isues with hardness on the heat affected zone. The criteria to meet is 248 Hv10 (vickers). Especially at the Haz zone iam getting 300 vickers.
Anyone have experience in tube to tube sheet welding can offer some suggestions that will be great.

My best results were in 0.095 wall thickness where HAZ readings were close to 250 still failed becauseit was marginally over. 0.065, 0.83 failed with HAZ hardness averaging at 300.
Best reagrds
Tesh

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0.065W.JPG
0.083W.JPG
0.095W.JPG

orbital

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Apr 28, 2020, 11:27:39 PM4/28/20
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The CE on the plate was 0.44, thanks in advance,


On Thursday, April 9, 2020 at 6:05:02 AM UTC-5, gerr...@yahoo.com wrote:
Problems related to Hardness may be due to High Heat Input or preheat being applied not properly (temperature is OK) you may look at the option of reducing the cooling rate or checking at the Carbon Equivalent

Thanks & Regards

J.Gerald Jayakumar




On Thursday, April 9, 2020, 05:31:05 PM GMT+7, 'd...@btinternet.com' via Materials & Welding <material...@googlegroups.com> wrote:



Try a slower welding speed and a closer arc length.

Regards, 9 4 2020.

David Harvey

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orbital

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Apr 28, 2020, 11:27:39 PM4/28/20
to Materials & Welding
Doesent increasing heat input accelerate cooling, provided i cant control the quick loosing of temperature from the interpass. I was thinking about increasing roatational speed and simultaneously reducing amperages, which somewhat keeps the cooling rate down.


On Wednesday, April 15, 2020 at 1:28:55 AM UTC-5, Ahmed Osman wrote:
- check the hardness of BM away from welding and what Is the welding HV values ?
- HAZ prosperities mainly related to the base metal 
- your base metal SA516 in normalised condition .. after welding the mech. priorities gained by heat treatment is lost unless u keeping the transformation temp. and cooling rate as the original treatment condition
- any way .. as much as u can try to increase HI for getting the lowest cooling rate 

best regards

On Thursday, April 9, 2020, 07:24:00 a.m. GMT+3, orbital <sati...@gmail.com> wrote:


Guys i am developing weld procedures for automated orbital welding and having trouble trouble with achieving required hardness.
SA-516-70N 2"Thk tube sheet / SA-179 1"OD x 6"Lg Tubes different wall thickness. Preheating 400 interpass 600 F

I am having isues with hardness on the heat affected zone. The criteria to meet is 248 Hv10 (vickers). Especially at the Haz zone iam getting 300 vickers.
Anyone have experience in tube to tube sheet welding can offer some suggestions that will be great.

My best results were in 0.095 wall thickness where HAZ readings were close to 250 still failed becauseit was marginally over. 0.065, 0.83 failed with HAZ hardness averaging at 300.
Best reagrds
Tesh

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https://www.linkedin.com/groups/122787
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orbital

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Apr 28, 2020, 11:27:40 PM4/28/20
to Materials & Welding
David thank you for your reply. Can you tell me the reasoning behind slower weld speed.

orbital

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Apr 28, 2020, 11:27:40 PM4/28/20
to Materials & Welding
Decreasing the heat input makes sense. I am goi ng to try reducing the amperage and increasing weld speed.


On Saturday, April 11, 2020 at 11:20:36 PM UTC-5, George Dilintas wrote:
Higher hardness could mean:
Higher residual stresses
Martensite formation
The most probable cause are Higher residual stresses. 
To reduce the residual stresses are following options:
1. Increase preheat. You may try 100degC
2. Decrease interpass temperature. You May try 150 degC
3. Decrease heat Input by shortening the arc or Increase welding spead

Στις Πέμ, 9 Απρ 2020, 13:31 ο χρήστης 'd...@btinternet.com' via Materials & Welding <material...@googlegroups.com> έγραψε:


Try a slower welding speed and a closer arc length.

Regards, 9 4 2020.

David Harvey

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Vanchinath S.A.

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Apr 29, 2020, 1:20:00 AM4/29/20
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What's the method for preheating?  You have to ensure whole thickness is covered for preheating to reduce the cooling rate. 
Regards

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