Patent ID: 7547410

Claim:
A hot-gas quenching apparatus for quenching a workpiece preheated at an initial temperature to an intermediate temperature at around an isothermal holding temperature for transformation of the workpiece and holding the isothermal holding temperature before cooling the workpiece to room temperature or below with an inert gas and quenching, the apparatus comprising: a workpiece container configured to contain the preheated workpiece in an inert gas atmosphere or in a vacuum; a flow path provided with the workpiece container; a hot-gas circulation duct configured to hold the inert gas as a hot-gas at an intermediate temperature close to an isothermal transformation temperature of the workpiece, wherein the hot-gas circulation duct is provided separately from a space for preheating the workpiece, and the hot-gas circulation duct is arranged to hold the hot-gas therein constantly until the hot-gas is used to quench the workpiece; a first duct and a second duct, respectively, provided with a control window having an aperture that is controlled, the first duct and the second duct diverging from the flow path, a surface of the workpiece container being connected to an input terminal of the hot-gas circulation duct through the control windows; a gas cooling unit provided in the second duct and configured to cool the inert gas to room temperature with a cooling medium at room temperature; a mixer connected at each end of the first duct and the second duct and configured to mix the inert gas introduced, respectively, from the first duct and the second duct for equalization of a temperature of the inert gas from the first duct and the inert gas from the second duct; a distributor connecting an output terminal of the hot-gas circulation duct to the workpiece container and configured to blow mixed inert gas evenly onto a surface of the workpiece; a blower provided between the mixer and the distributor and configured to supply the inert gas under pressure from the mixer to the distributor; an inert gas introducing unit configured to introduce a required amount of the inert gas to the first duct and the second duct, respectively; a controller configured to control the aperture of the control window to hold a temperature of the mixed inert gas at the intermediate temperature and configured to blow the inert gas of the hot-gas circulation duct to the workpiece for quenching the workpiece with the hot-gas of the intermediate temperature and then hold the workpiece at a constant temperature equal to the isothermal transformation temperature of the workpiece for an isothermal holding of the workpiece; a heater configured to prevent the workpiece from being cooled due to heat loss during the isothermal holding of the workpiece; and a heat storage contact media provided in the hot-gas circulation duct for controlling the hot-gas at a stable temperature.