WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
(a) Homogeneous Armor. The metal edges of holes or cracks made
by an anti-tank projectile in homogeneous armor plate are ragged
and bent, with the metal drifted in the direction of penetration.
Cracks in homogeneous armor are usually caused by stresses in the
metal. These cracks are present at severe bulges or bends in the
damaged armor plate.
(b) Face Hardened Armor.
The metal edges of holes and cracks
in face hardened armor are relatively clean cut and sharp.
The
plates do not bulge to any great extent before cracking.
By
examining the edges of freshly broken face hardened armor, it can
be noted that the metal at the face side is brighter and of a
finer structure than the metal at the soft side.
The brighter
metal extends to a depth of approximately 1/5 to 1/4 inch in
thickness from the outside surface.
4.
Cutting Armor Plate
a. Homogeneous Armor Plate. Either the oxygen cutting torch or
the electric arc can be used to cut homogeneous armor plate. The
oxygen cutting torch, however, is preferable. The carbon arc can
be used to cut out welds and to cut castings and plates, but the
shielded metal-arc is preferred when oxygen and acetylene are not
available.
b.
Face Hardened Armor Plate.
(1) General.
The procedure for cutting this type of armor is
essentially the same as that required for homogeneous armor.
However, every precaution should be taken to keep as much heat as
possible away from the hard face side of the plate. This is done
by cutting from the soft side of the armor plate. Cutting from
the soft side limits the extent of heating and consequent
softening of the hard face side.
(2) Cutting with the Oxygen Torch.
(a) The general practice used for oxygen torch cutting
can be
applied for cutting armor plate, but the tip size,
cutting
oxygen, and preheating gas temperatures should be kept
at the
minimum,
consistent
with
good
quality
cuts,
to
prevent
overheating.
(b) Stainless steel is a nonoxidizing metal.
Therefore, when
cutting stainless steel type welds
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