Method for heat treating steel

摘要

A process is provided for heat treating steel in which each segment of a piece of steel is quenched in a quenching zone 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 is heated above its critical transformation temperature and then each longitudinal segment of the pipe 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 is subjected to further processing. An apparatus for heat treating a steel pipe is also provided including a preheater for heating the steel pipe; feeding means adapted to feed the steel pipe at a variable rate from the preheater; a flow chamber into which the steel pipe is fed, the flow chamber being adapted to bring a cooling medium into contact with the outer surface of a segment of the steel pipe; and an internal feeder having an outside diameter less than that of the steel pipe and adapted to direct a cooling medium against a contoured surface of a plug. The plug is of sufficient size to seal slidably the inside cross section of the steel pipe as it passes into the flow chamber.