Xray GMAW
Xray GMAW
(OP)
Is is acceptable to xray a gmaw weld. Im thinking it is not, but also thinking is has to do with short circuit transfre.
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RE: Xray GMAW
RE: Xray GMAW
RE: Xray GMAW
RE: Xray GMAW
The question is not whether the welds would fail radiography, but rather if radiograph is capable of detecting serious flaws that can be present in a short circuit GMAW joint. I believe weldtek has the correct approach, and it seems Redhead1963 agrees.
RE: Xray GMAW
RE: Xray GMAW
If the planetary discontinuity is parallel to the beam the probability of detection is high. If the orientation of the planetary discontinuity is perpendicular to the beam the probability is very poor. Radiographic examination is not likely to detect discontinuities such as laminations, delaminations, or incomplete fusion to a backing bar. The discontinuity does not represent a change in thickness or density along the axis of the radiation.
Incomplete fusion between layers of weld beads may fall into the same category as a lamination because it may not be oriented in a favorable direction relative to the radiation.
A crack is often parallel to the axis of the radiation beam and detects cracks that do represent a change in material thickness.
Incomplete fusion, especially when welding with GMAW-S, may occur between the weld bead and the groove face. Depending on the orientation of the radiation, it may or may not detect the discontinuity. This can be very troublesome when “shooting” with an offset. The incomplete fusion parallel to the beam will be detected while the opposite groove face will be more perpendicular to the radiation beam and may be missed entirely. Consider a bevel groove with a groove angle of 45 degrees. If the radiation source is located on the side opposite the bevel and places such that it is 45 degrees to the test surface places the incomplete fusion to the groove face perpendicular to the energy beam. It is highly improbable the incomplete fusion will be detected. Changing the position of the source such that the axis of the radiation beam is parallel to the 45 degree groove face changes everything. The probability of detecting the incomplete fusion between the weld and the groove face is excellent.
The same tricks can be played when using ultrasonic testing with a shear wave, but the favorable orientation is perpendicular to the sound beam.
Best regards - Al
RE: Xray GMAW
The question was -is it acceptable to xray gmaw welds-- By every code the answer is yes short arc or not.
RE: Xray GMAW
I don't disagree that welds deposited with GMAW-S can be examined using RT. However, since GMAW-S is known for the tendency to suffer fusion type discontinuities, it is something to keep in mind when performing any volumetric examination.
Best regards - Al
RE: Xray GMAW
RE: Xray GMAW
All GMAW can be susceptible to LOF problems based on the welders technique.
I was in the unique position years ago in New Zealand where I would witness the welder qualification tests as a third party and then take them back to our lab and radiograph them myself.
I could basically tell who was going to fail before I had even radiographed them based on the welders who tried to "push" the torch rather than pull/drag.
Even with spray transfer, if the molten puddle is getting pushed ahead of the arc then the arc cannot come in to contact with "clean" metal and LOF problems come into play.
Agree totally with Als comments regarding the difficulty of identifying all LOF discontinuities with RT,
Cheers,
DD
RE: Xray GMAW
RE: Xray GMAW
kgp