FLUXES

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FLUXES
Difficulty would be experienced in welding with only the metal and rod to
work with because of the scale that forms on many materials under heat,
the oxides of other metals and the impurities found in almost all metals.
These things tend to prevent a perfect joining of the metals and some
means are necessary to prevent their action.

Various chemicals, usually in powder form, are used to accomplish the
result of cleaning the weld and making the work of the operator less
difficult. They are called fluxes.

A flux is used to float off physical impurities from the molten metal; to
furnish a protecting coating around the weld; to assist in the removal of
any objectionable oxide of the metals being handled; to lower the
temperature at which the materials flow; to make a cleaner weld and to
produce a better quality of metal in the finished work.

The flux must be of such composition that it will accomplish the desired
result without introducing new difficulties. They may be prepared by the
operator in many cases or may be secured from the makers of welding
apparatus, the same remarks applying to their quality as were made
regarding the welding rods, that is, only the best should be considered.

The flux used for cast iron should have a softening effect and should
prevent burning of the metal. In many cases it is possible and even
preferable to weld cast iron without the use of a flux, and in any event
the smaller the quantity used the better the result should be.

Flux should not be added just before the completion of the work because
the heat will not have time to drive the added elements out of the metal
or to incorporate them with the metal properly.

Aluminum should never be welded without using a flux because of the oxide
formed. This oxide, called alumina, does not melt until a heat of 5,000°
Fahrenheit is reached, four times the heat needed to melt the aluminum
itself. It is necessary that this oxide be broken down or dissolved so
that the aluminum may have a chance to flow together. Copper is another
metal that requires a flux because of its rapid oxidation under heat.

While the flux is often thrown or sprinkled along the break while
welding, much better results will be obtained by dipping the hot end of
the welding rod into the flux whenever the work needs it. Sufficient
powder will stick on the end of the rod for all purposes, and with some
fluxes too much will adhere. Care should always be used to avoid the
application of excessive flux, as this is usually worse than using too
little.

SUPPLIES AND FIXTURES
Goggles.--The oxy-acetylene torch should not be used without the
protection to the eyes afforded by goggles. These not only relieve
unnecessary strain, but make it much easier to watch the exact progress
of the work with the molten metal. The difficulty of protecting the sight
while welding is even greater than when cutting metal with the torch.

Acetylene gives a light which is nearest to sunlight of any artificial
illuminant. But for the fact that this gas light gives a little more
green and less blue in its composition, it would be the same in quality
and practically the same in intensity. This light from the gas is almost
absent during welding, being lost with the addition of the extra oxygen
needed to produce the welding heat. The light that is dangerous comes
from the molten metal which flows under the torch at a bright white heat.

Goggles for protection against this light and the heat that goes with it
may be secured in various tints, the darker glass being for welding and
the lighter for cutting. Those having frames in which the metal parts do
not touch the flesh directly are most desirable because of the high
temperature reached by these parts.

Gloves.--While not as necessary as are the goggles, gloves are a
convenience in many cases. Those in which leather touches the hands
directly are really of little value as the heat that protection is
desired against makes the leather so hot that nothing is gained in
comfort. Gloves are made with asbestos cloth, which are not open to this
objection in so great a degree.

Tables and Stands.--Tables for holding work while being welded are
usually made from lengths of angle steel welded together. The top should
be rectangular, about two feet wide and two and one-half feet long. The
legs should support the working surface at a height of thirty-two to
thirty-six inches from the floor. Metal lattice work may be fastened or
laid in the top framework and used to support a layer of firebrick bound
together with a mixture of one-third cement and two-thirds fireclay. The
piece being welded is braced and supported on this table with pieces of
firebrick so that it will remain stationary during the operation.

Holders for supporting the tanks of gas may be made or purchased in forms
that rest directly on the floor or that are mounted on wheels. These
holders are quite useful where the floor or ground is very uneven.

Hose.--All permanent lines from tanks and generators to the torches are
made with piping rigidly supported, but the short distance from the end
of the pipe line to the torch itself is completed with a flexible hose so
that the operator may be free in his movements while welding. An accident
through which the gases mix in the hose and are ignited will burst this
part of the equipment, with more or less painful results to the person
handling it. For that reason it is well to use hose with great enough
strength to withstand excessive pressure.

A poor grade of hose will also break down inside and clog the flow of
gas, both through itself and through the parts of the torch. To avoid
outside damage and cuts this hose is sometimes encased with coiled sheet
metal. Hose may be secured with a bursting strength of more than 1,000
pounds to the square inch. Many operators prefer to distinguish between
the oxygen and acetylene lines by their color and to allow this, red is
used for the oxygen and black for acetylene.

Other Materials.--Sheet asbestos and asbestos fibre in flakes are used to
cover parts of the work while preparing them for welding and during the
operation itself. The flakes and small pieces that become detached from
the large sheets are thrown into a bin where the completed small work is
placed to allow slow and even cooling while protected by the asbestos.

Asbestos fibre and also ordinary fireclay are often used to make a
backing or mould into a form that may be placed behind aluminum and some
other metals that flow at a low heat and which are accordingly difficult
to handle under ordinary methods. This forms a solid mould into which the
metal is practically cast as melted by the torch so that the desired
shape is secured without danger of the walls of metal breaking through
and flowing away.

Carbon blocks and rods are made in various shapes and sizes so that they
may be used to fill threaded holes and other places that it is desired to
protect during welding. These may be secured in rods of various diameters
up to one inch and in blocks of several different dimensions.

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Warmly,
Pat Mitchell
http://www.weldingsecrets.net/main.html