Page 71 - SSAB Welding Handbook Edition 2

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Welding handbook 12.0 The use of shielding gas

The pulsed arc technique is similar to the spray arc
technique with the main exceptions being:
©SSAB
4 Thinner plate thicknesses can be welded using
Single globular the pulsed arc technique since welding can be
transfer
Welding gun carried out with lower heat input in relation to
conventional spray arc welding. Even the
Droplet
Consumable thinnest plate thicknesses in the Hardox and
electrode Strenx range can be welded with the pulsed
Shielding gas
arc technique.
4 A disadvantage of the pulsed arc technique is
Weld pool
lower productivity, compared to spray arc welding.
Base metal
The selection of shielding gas compositions for pulsed
Spray transfer arc welding is the same as for spray arc welding. The
issues regarding pulsed arc welding are, therefore,
Fig. 12.3: MAG welding with a spray arc. included in the recommendations for spray arc
welding.

The sound from spray arc welding can be Because of the continuous developments in MAG
distinguished from short arc welding by its welding of high strength steels, there are other, more
uniform character. unconventional, arc types than those mentioned in
this chapter. For updated information in these
Welding with a pulsed arc technique means that a matters, contact SSAB.
spray arc can be attained with relatively low heat
inputs. This technique uses a pulsed current where
the top values of the parameters are high enough Shielding gases for MAG welding
for a spray arc to form while, at the same time, the When applying a gas mixture of argon and carbon
mean value of the current is proportionally low. dioxide in MAG welding, there are advantages as
Each pulse peak of the current enables a droplet well as drawbacks associated with each chemical
transfer, without short-circuiting, from the consumable component. The objective is to optimize the mixture
to the melt, which is illustrated in fig. 12.4.
for each specific welding situation by drawing on
the benefits of both chemicals while minimizing the
drawbacks as much as possible.
Pulse peak current
2 3
There are alternatives to the suggested gas mixtures
4 5 mentioned in this chapter. One alternative is to partly
Current , A or completely replace CO with oxygen. Since these
2
Background current 1 mixtures have a limited usage, they are not mentioned
1 2 3 45 further in this context. Additional information
regarding these shielding gas mixtures can be
Time
obtained from the gas manufacturers.
Fig. 12.4: Typical current appearance during pulsed arc welding.

This handbook contains general suggestions and information without any expressed or implied warranty of any kind. SSAB hereby expressly disclaims
all liability of any kind, including any damages, in connection with the use of the information and for their suitability for individual applications. 71
It is the responsibility of the user of this brochure to adapt the recommendations contained therein to the requirements of individual applications.