Oil Bath Quenching
A 60 mm diameter bar stock made from 4340 steel is quenched in an agitated oil bath. What is the expected hardness (R_c) at the bar stock's center?
Hint
Quenching is rapidly cooling a workpiece in water, oil, or air to obtain certain material properties. When looking at the cooling rates for bars quenched in agitated oil graph, we need to find the
$$D_{qe}$$
that is associated with our given bar stock diameter intersecting the center cooling curve C.
Hint 2
Quenching is rapidly cooling a workpiece in water, oil, or air to obtain certain material properties. When looking at the cooling rates for bars quenched in agitated oil graph, we need to find the
$$D_{qe}$$
that is associated with our given bar stock diameter intersecting the center cooling curve C.
The distance from quenched end,
$$D_{qe}$$
, for a 60 mm quenched in agitated oil is around 19.5 mm. This can be used to determine the 4340 hardness via the Jominy end-quench test, which is a standardized method of measuring the hardenability of steels.
On the Jominy Curve, the 19.5 mm distance from the quenched end intersects the 4340 steel line at around
$$R_c=52$$
. Thus, the expected center hardness for a 4340 steel of diameter 60 mm when quenched in an agitated oil bath is 52.
52