METAL PROPERTIES, CHAR, USES, AND CODES - OD1643 - LESSON 1/TASK 2
oxidation of elements present in the specimen.
For example, gray
cast iron is much lower in resistance than a ductile steel and its
initial sparks are proportionately lower in color temperature.
The
presence of carbon in the iron causes high intensity spurts as the
carbon burns in the air a short distance from the grinding wheel.
Carbon is a necessary element for spurts or bursts.
Some soft
nonferrous metals, such as copper, brass, and aluminum, yield no true
grinding sparks in the air.
The first temperature glow color is
produced by heat generated when a chip is torn from the metal
specimen.
As the chip of iron or steel speeds through the air,
higher temperatures and more brilliant color are reached through
oxidation. Spear points at the end of the visible lines are observed
from several steels, but are especially noticeable when the steel
contains molybdenum.
Figures 4 and 5 below and on the following
page, also serve to illustrate the variations in the direction of
fire sparks near the grinding wheel.
FIGURE 4.
SPARK TEST CHARACTERISTICS OF METALS.
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