Wide Seam And No Weld Penetration; Uneven Seam/Hole Formation At The End Of Welding - Orbitalum ORBIMAT 300 SW Traduccion Del Manual De Instrucciones Originales

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9.2.3

Wide seam and no weld penetration

When welding without a filler wire, is the seam unusually "wide" without going "deep"?
Does increasing the current amplify the effect?
Is proper weld penetration (even on comparatively thinner walls) not possible?
Possible causes
The so-called "Marangoni effect".
In stainless steel, the percentage component of sulfur is always limited upward, as sulfur forms inclusions (manga-
nese sulfide) which lead to small craters and other defects and which ultimately reduce the corrosion resistance of the
material. For this reason, the sulfur content is limited, for example to a maximum of 0.030%. With this level of sulfur,
welding is no problem.
If the sulfur content is reduced further (approx. 0.005% or lower), the so-called "convection streams" in the melt pool
(in simplified terms) tend to flow more horizontally and on the surface. This leads to widening of the seam without
penetration.
Remedy
X Carry out a material analysis for confirmation.
X Change the material if appropriate (it may be sufficient to just change the batch).
X Weld with filler wire so that a correspondingly higher sulfur content arises in the melting pool thanks to the wire.
9.2.4

Uneven seam/hole formation at the end of welding

Do the weld seams look as if the torch "moved sideways" in an uncontrolled fashion?
Does the seam not remain centered over the joint, instead pulling to one side or moving "back and forth"?
Possible causes and remedies
• When welding pipe and molded part: "Marangoni effect".
The sulfur content tends to be high with materials for machining. The effect is seen on one side of the pipe joint
with the result of a seam which is heavily asymmetrical to the joint. The root inside the pipe is then often formed
completely outside an next to the pipe joint.
If the seam regularly wanders off to the side only in one or two places when welding, the corresponding different
material composition in the base material and in the seam is responsible for the effect at a longitudinal pipe seam.
X Shorten the arc gap slightly.
• Gas quantity set too high (weld gas or forming gas):
If an excessive gas quantity is set for small cassette heads (especially OW12), turbulence occurs in the pocket,
which can lead to an extremely irregular arc. The same applies if too much forming gas is used and it comes out at
the weld joint at relatively high pressure.
X Regulate the gas quantity.
• Excessively high forming gas pressure:
Heavy outward bulging of the seam with a type of "hollow groove" inside the pipe. Hole formation also often occurs
at the end of welding if the excessive pressure of the gas can only be "relieved" over the liquid melt pool. With cas-
sette weld heads in particular, liquid metal dripping in the head can cause considerable consequential damage.
X Regulate the forming gas pressure.
• Worn electrode without proper grinding:
The beginning point of the arc often "dances" back and forth on the electrode. With a poor-quality electrode, lateral
migration of the arc from the electrode can be observed now and then. The reason for this can be that the alloy
components in the base material are not evenly distributed.
X Grind the electrode properly.
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orbitalum tools GmbH, D-78224 Singen, www.orbitalum.com, Phone +49 (0) 77 31 792-0
ORBIMAT 300 SW
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