FED-STD-791D
5.2 Five steel test bars, made from steel meeting the requirements of ASTM A 576,
A675A, 675M, Steel No. 1050, approximately 2.5 cm (1 in) diameter by 6.4 cm (2-1/2 in) long,
with loop on one end, scale free, weighing 250 5 g.
5.3 Abrasive paper, 280 grit (ANSI B74.18).
5.4 1,1,1-Trichloroethane (ASTM D 4126).
5.5 Facial tissue.
6. PROCEDURE
6.1 Polish all five steel test bars with 280 grit abrasive paper to a uniform finish. Place
the five test bars in the furnace and permit them to remain for at least one hour. The atmosphere
in the furnace must be so controlled as to prevent the formation of carbon smut or scale. Clean
the inside of the two insulated containers with 1,1,1-trichloroethane and facial tissue. Place 2000
10 mL of the quenching oil under test in each of the containers. The oil must be at the
temperature of the furnace room. Number the containers l and 2. Place the stirrer in container 1
and stir until the oil has reached a constant temperature. Record the temperature of the oil in
this container. Turn off the stirrer. Remove one of the test bars from the furnace using the hook
and vertically immerse the test bar beneath the surface of the oil. Start the stirrer and record the
highest temperature obtained.
6.2 Place the stirrer in position in the second container and stir until the oil has reached a
constant temperature. Record the temperature of the oil in this container and turn off the stirrer.
Remove one test bar from the furnace and plunge it vertically beneath the surface of the
unagitated oil. Hold the test bar in the oil for 5 0.10 s. Remove the bar from the oil and start
the stirrer. Operate the stirrer for approximately 15 s. Stop the stirrer and plunge the third test
bar into the oil. Repeat this sequence until all of the test bars have been quenched. Record the
total rise in temperature for the 4 test bars. The total rise in temperature produced by the four
test bars quenched in container 2, divided by 4 gives the average temperature rise for each 5-
second test.
NOTE: Speed and timing are essential in order to avoid heat losses. Stirring should not be
violent, only sufficient to produce a uniform temperature.
7. CALCULATIONS.
a
Quenching speed = * 100
b
7.1 Calculate the quenching speed of the oil by the following formula:
where:
a = the average rise in temperature produced by the four test bars quenched in container 2.
b = temperature rise produced by the fully quenched test bar (quenched in container 1).
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