(57) A process is provided for heat treating steel in which each segment of a piece of
steel is quenched in a quenching zone, such as inflow chamber (20) by directing the
flow of a sufficient amount of a cooling medium against a surface of each segment
to lower the temperature of the segment to a desired temperature while vaporizing
substantially all of the cooling medium to create a vapor blanket around at least
one surface of each segment so cooled. In one embodiment, steel pipe (16) is heated
above its critical transformation temperature in a furnace (11) and then each iongitudi-
nal segment of the pipe (16) is sequentially quenched by substantially simultaneously
sending a sufficient amount of water against the inside and outside surfaces of each
segment to reduce the temperature of the segment to within a predetermined range while
vaporizing substantially all of the water to create a steam blanket around the segment.
The steam blanket is then maintained on at least the inside surface of each segment
in order to control the temperature change of each segment until the pipe (16) is
subjected to further processing. An apparatus for heat treating a steel pipe (16)
is also provided including a preheater, such as furnace (11) for heating the steel
pipe (16); feeding means, such as rollers (76) adapted to feed the steel pipe at a
variable rate from the preheater, such as furnace (11); a flow chamber (20) into which
the steel pipe (16) is fed, the flow chamber (20) being adapted to bring a cooling
medium into contact with the outer surface of a segment of the steel pipe (16); and
an internal feeder (40) having an outside diameter less than that of the steel pipe
(16) and adapted to direct a cooling medium against a contoured surface of a plug
(50). The plug (50) is of sufficient size to slidably seal the inside cross section
of the steel pipe (16) as it passes into the flow chamber (20).
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