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View Full Version : HAZ cracks during bend test (MAGp)?

xixiubin
02-25-2009, 01:37 PM
Is there anyone know well about pulsed spray transfer arc welding technique(MAGp) on low temperature steel, low alloy steel or heat resistant steel?by using the 80+20 mixed gas with no spatter.Now the problem is a little cracks (or folds)come out after bend test in the HAZ. What caused this? (Φ1.2mm, vertical up welding)
BTW, it's excellent for other test data.
http://i44.tinypic.com/ncxvfp.jpghttp://i35.tinypic.com/dma4py.jpg
DesertRider33
02-25-2009, 01:58 PM
Possibly too much CO2 in the gas mix? Spray is usually done with less than 15% CO2, or with 2% oxygen instead of CO2.
MoonRise
02-25-2009, 02:01 PM
The cracks/tears are in the HAZ on the parent material and not in the weld filler/bead?

I'd guess improper pre/post heat leading to increased hardness and loss of ductility/elongation in the HAZ.

And as DesertRider33 mentioned, usually spray is done with 15% or less CO2 in the gas mix, or a 98-2 argon-oxygen mix.
qaqc
02-25-2009, 05:16 PM
How about posting pics of the bend specimens. Hard to go off of a description
xixiubin
02-25-2009, 09:39 PM
Through the test procedures,I think 20%CO2 is OK, whether considered the efficiency or the spatter.
maybe next time I will upload the pic.
Is there any chance for low heat input or welding skills? I mean it seemed didn't fusion well.
mre_powers
02-25-2009, 09:50 PM
any chance a slight breeze/fan/ac/heater is blowing protective gass away?
El_Lloydeo
02-25-2009, 09:54 PM
are your grind marks transverse to the weld?
pistolnoon
02-26-2009, 02:24 AM
Whats the criteria for failure?
jamz
02-26-2009, 09:03 AM
true spray transfer requires 85% Argon
A_DAB_will_do
02-26-2009, 09:26 AM
True HAZ cracks are in the base metal. To help diagnose your problem, we need more specifics on the base metal alloy. What is the grade of material? Please give the closest western equivalent, if this is an alloy spec from China.

If forced to guess, I'd speculate that there is a problem with pre-heat, interpass temperature, or post-weld heat treatment. But without more data on the base metal, I can't give you a better answer.

Is there anyone know well about pulsed spray transfer arc welding technique(MAGp) on low temperature steel, low alloy steel or heat resistant steel?by using the 80+20 mixed gas with no spatter.Now the problem is a little cracks (or folds)come out after bend test in the HAZ. What caused this? (Φ1.2mm, vertical up welding)
BTW, it's excellent for other test data.
http://i44.tinypic.com/ncxvfp.jpghttp://i35.tinypic.com/dma4py.jpg
qaqc
02-26-2009, 09:39 AM
true spray transfer requires 85% Argon

Then why has AWS D1.5 (bridge welding code) listed 80% min Ar for GMAW spray?
El_Lloydeo
02-26-2009, 04:42 PM
D1.5 (at least the one im looking at) doesnt say 80% min. for spray, it just says anything less than 80% argon is considered to be short circuiting. while there is a prohibition of GMAW-S without written consent of the engineer, globular transfer isnt prohibited. will check out the newest edition tomorrow at work. the min. argon everywhere i have read has been 90%.
qaqc
02-26-2009, 05:23 PM
Feel free to limit yourself.
lotechman
02-27-2009, 09:17 AM
If you are doing a bend test with HSLA you might check to see if it is possible to do. Often the ductility of these alloys is limited and so a bend test is not a fair test.
Failure in the HAZ means to me that there is nothing wrong with the welding bead. Something is wrong with pre or post heats, or as I mentioned you are using the wrong test for that alloy.