1 SpotWelding

 

 

OXY-ACETYLENE WELDING AND CUTTING MATERIALS

Welding.--Oxy-acetylene welding is an autogenous welding process, in
which two parts of the same or different metals are joined by causing the
edges to melt and unite while molten without the aid of hammering or
compression. When cool, the parts form one piece of metal.

The oxy-acetylene flame is made by mixing oxygen and acetylene gases in a
special welding torch or blowpipe, producing, when burned, a heat of 6,300
degrees, which is more than twice the melting temperature of the common
metals. This flame, while being of intense heat, is of very small size.

Cutting.--The process of cutting metals with the flame produced from
oxygen and acetylene depends on the fact that a jet of oxygen directed upon
hot metal causes the metal itself to burn away with great rapidity,
resulting in a narrow slot through the section cut. The action is so fast
that metal is not injured on either side of the cut.

Carbon Removal.--This process depends on the fact that carbon will
burn and almost completely vanish if the action is assisted with a supply
of pure oxygen gas. After the combustion is started with any convenient
flame, it continues as long as carbon remains in the path of the jet of
oxygen.

Materials.--For the performance of the above operations we require
the two gases, oxygen and acetylene, to produce the flames; rods of metal
which may be added to the joints while molten in order to give the weld
sufficient strength and proper form, and various chemical powders, called
fluxes, which assist in the flow of metal and in doing away with many of
the impurities and other objectionable features.

Instruments.--To control the combustion of the gases and add to the
convenience of the operator a number of accessories are required.

The pressure of the gases in their usual containers is much too high for
their proper use in the torch and we therefore need suitable valves which
allow the gas to escape from the containers when wanted, and other
specially designed valves which reduce the pressure. Hose, composed of
rubber and fabric, together with suitable connections, is used to carry the
gas to the torch.

The torches for welding and cutting form a class of highly developed
instruments of the greatest accuracy in manufacture, and must be thoroughly
understood by the welder. Tables, stands and special supports are provided
for holding the work while being welded, and in order to handle the various
metals and allow for their peculiarities while heated use is made of ovens
and torches for preheating. The operator requires the protection of
goggles, masks, gloves and appliances which prevent undue radiation of the
heat.

Torch Practice.--The actual work of welding and cutting requires
preliminary preparation in the form of heat treatment for the metals,
including preheating, annealing and tempering. The surfaces to be joined
must be properly prepared for the flame, and the operation of the torches
for best results requires careful and correct regulation of the gases and
the flame produced.

Finally, the different metals that are to be welded require special
treatment for each one, depending on the physical and chemical
characteristics of the material.

It will thus be seen that the apparently simple operations of welding and
cutting require special materials, instruments and preparation on the part
of the operator and it is a proved fact that failures, which have been
attributed to the method, are really due to lack of these necessary
qualifications.

 


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