CHAPTER 15
METALLURGY AND HEAT TREATMENT
CHAPTER LEARNING OBJECTIVES
Upon completing this chapter, you should be able to do the following:
Explain the internal structures of metals.
Identify and explain the use of heat-treating equipment.
Explain the principles of heat treating.
Explain the heat treatment of metals.
Identify heat-treating problems.
Identify and explain hardness tests.
CHEMICAL METALLURGY deals with the
As a Machinery Repairman, you work with many
reduction of metals from their ores and the creation of
different types of metals and alloys. The more
alloys by changing the chemical structure of the base
knowledge you have of metals and alloys, the better you
metals. For example, steel is made from iron, which is
will be able to perform your repair and maintenance
produced from iron ore. During this process, coke is
duties. The information you have already learned about
the characteristics of metals and alloys in chapter 3 will
help you better understand the theory of metallurgy and
PHYSICAL METALLURGY deals with the
heat treatment.
nature, structure, and physical properties of metals and
alloys. The subject of physical metallurgy includes
There have been many books written on metallurgy
metallography (study of metals with a microscope),
and heat treatment. This chapter will only be an
mechanical testing, and heat treatment, which we will
overview. For more detailed information of the theory
discuss later in this chapter.
and of metallurgy and heat treatment, consult a
machinist handbook or any textbook on physical
MECHANICAL METALLURGY deals with the
metallurgy.
working and shaping of metals through operations such
as machining, casting, and forging.
As with any shop equipment you must observe all
posted safety precautions. Review your equipment
operators manual for safety precautions and any
STRUCTURE OF METAL
chapters of Navy Occupational Safety and Health
Throughout your career as a Machinery Repairman,
(NAVOSH) Program Manual for Forces Afloat,
OPNAV instruction 5100.l9B, which pertain to the
you have become familiar with the physical properties,
such as hardness, brittleness, malleability, and ductility,
equipment you will be operating.
associated with various metals. These properties of
Metallurgy is the art or science of separating metals
metal are directly related to the internal, or atomic,
from their ores, making and compounding alloys, and
structure of the metals. This section will explain to you
working or heat-treating metals to give them certain
how various arrangements of atoms result in these and
desired shapes or properties. Metallurgy has been
other properties.
broken down into three branches--chemical
Metals in liquid state have a noncrystalline
metallurgy, physical metallurgy, and mechanical
metallurgy.
structural form. The crystals in solid metal are called
15-1