Page 212 - CITS - Welder - Trade Theory

WELDER - CITS

decrease of Arc stability, a reduction in weld appearance and more difficult slag removed. In general the flux
of highest basicity consists with stable arc, good weld appearance and easy slag removal should be chosen.

Metallic deoxidizers and ferro-alloys can be incorporated into agglomerated basic fluxes since low temperature
are involved in their manufacture. Use of alloyed flux (also termed active flux) demands a closer control of the
welding parameters, especially the arc voltage to ensure consistent weld metal chemistry. An increase in arc
voltage increases the flux-wire consumption ratio and thereby results in increased alloy transfer to the weld
metal. Like low hydrogen type of electrodes the agglomerated flux to be backed to remove moisture when
stored in humid atmosphere due to the hygroscopic properties.
Agglomerated fluxes have lower bulk density than fused fluxes. This has the advantage that under identical
condition of current and voltage, less flux is melted and forms a slag as compared to fused fluxes.
The use of agglomerated fluxes offers the greatest advantage for hard facing applications. Sinc ferro alloys
can be very easily incorporated into agglomerated fluxes and significant alloying affect obtained, deposits of
varying hardness and wear resistant properties can be obtained by using simple mild steel wire in combination
with variously alloyed agglomerated fluxes. But with fused fluxes, alloy wires invariably have to be used, which
are expensive and not readily obtainable.
3 Aluminate Fluxes: Fluxes high in Al O (40-50%) produced a microstructure of good notch toughness in as
2
2
deposited weld metal as opposed to other flux composition. The level of non-metallic inclusions in the welds
generated from aluminate fluxes is lower than in the case of acidic fluxes, but higher than those produced by
highly basic fluxes,
4 Particle size: Particle size is an important property of a SA flux. For current higher than 800 Amps or for muid
wire applications a finer grain size are suitable. For lower current applications cause grain sizes are to be
used.
Saw procedures: SAW, semi-automatic and fully-automatic, is used for making butt joints in the downhand
position and for making fillet welds in T and lap joints in the downhand and horizontal-vertical positions as
shown in Fig 3. Normally this process cannot be used in vertical and overhead positions, because of the
difficulty of replacing the flux.

Fig 3

(a) AWS A 5-17-1980 specification for carbon steel electrode and fluxes for submerged-arc welding. This
standard gives eight classification based on wire chemistry and divided into three groups according to the
Mn levels, as shown in ANNEXURE - 1. In this classification system, the prefix E designates an electrode.
The letter L. M and H Indicate low, medium and high Mn content respectively. The letter K which appears
in some classes indicate that the electrode is made from the heat of Silicon - killed steel (as is obvious
from the Si levels). The digits 8, 12 etc., indicate in points, the nominal carbon content of the electrode (for
example 8m). Standard electrode diameters in mm are 1.6.1 2.0, 2.4, 3.2, 4.0, 5.6 and 6.4) This standard
also gives the classification system for fluxes based on the mechanical properties of the weld metal they
deposit in combination with certain classifications of electrodes. The mechanical tests, in effect, evaluate
the quality of a flux-wire combination.

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CITS : C G & M - Welder - Lesson 61-76