T.O. 33B-1-1
SECTION VII
DISCONTINUITIES AND THEIR MPI INDICATIONS
3.7
FORMATION OF DISCONTINUITIES AND THEIR MPI INDICATIONS.
3.7.1
Iron and Steel Manufacturing Processes.
Knowledge of iron and steel manufacturing processes is necessary to enable an inspector to interpret and
evaluate magnetic particle indications. It is not possible in this manual to explain all of the processes used in
the manufacture of iron and steel parts, but a brief review will explain how some discontinuities are formed.
3.7.1.1
Purpose of Processing.
Iron ore is converted into metal by heating it in a furnace. When it is liquid or molten it can be poured into
molds and allowed to cool and solidify. In the molten state it is possible to remove impurities and also to add
other elements to form alloys. These additions, along with other appropriate metal processing steps, impart
desirable properties to the finished metal that can make it:
Harder
Softer
Tougher
Stronger
Easier to machine
Resistant to heat
Resistant to corrosion
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