Quenching method and furnace

Abstract

Small hot metal objects such as engineering components are quenched in gas by tumbling them in an upward flow of gas distributed uniformly from a multiplicity of openings 18 in the horizontal floor 4 of a quenching chamber 2. The tumbling is performed for a sufficient period of time for the objects to be quenched to a desired temperature. The quenching chamber 2 has a lower region 8 through which the flow of quenching gas is at an uniform velocity and an upper region 10 in which the velocity of the quenching gas is decreased.

What is claimed is:  
     
         1 . A method for the gaseous quenching of small hot metal objects, comprising tumbling the small hot metal objects in an upward flow of quenching gas distributed uniformly from a multiplicity of openings in a horizontal floor, the quenching gas flowing from the floor at a uniform tumbling velocity and being subjected to deceleration so as to keep down the number of the objects carried away by the quenching gas, the tumbling being performed for a sufficient period of time for the objects to be quenched to a desired temperature.  
     
     
         2 . The method of  claim 1 , in which the quenching gas is nitrogen.  
     
     
         3 . The method of  claim 2 , in which the quenching gas contains up to 2% by volume of hydrogen.  
     
     
         4 . The method of  claim 1 , in which the uniform tumbling velocity is in the range of 15 to 150 m/s.  
     
     
         5 . The method of  claim 1 , in which the floor is provided by a flat perforate member having an open area of less than 20%.  
     
     
         6 . The method of  claim 5 , in which the perforations are uniformly spaced and are all of the same size and shape.  
     
     
         7 . The method of  claim 5 , in which the perforations are all of circular cross-section.  
     
     
         8 . The method of  claim 1 , in which the floor defines the top of a plenum chamber to which the quenching gas is supplied at an elevated pressure.  
     
     
         9 . The method of  claim 8 , in which the elevated pressure is in the range of 2 bar to 20 bar.  
     
     
         10 . The method of  claim 1 , wherein the metal objects are engineering components.  
     
     
         11 . A heat treatment furnace having associated therewith a quenching chamber for performing the gaseous quenching of small hot metal objects by tumbling the small hot metal objects in an upward flow of quenching gas, the quenching chamber having a horizontal floor, there being a multiplicity of openings in the horizontal floor for the distribution of quenching gas to the quenching chamber, wherein the quenching chamber has a region of constant cross-sectional area bounded at its lower end by the floor and at its upper end by a region of increasing cross-sectional area in the direction of flow of the quenching gas.  
     
     
         12 . The heat treatment furnace of  claim 11 , wherein the furnace is of a batch, semi-continuous or continuous kind.  
     
     
         13 . A method for quenching hot metal objects, comprising: 
 providing a flow of a quenching gas;    passing the flow of the quenching gas through a plurality of orifices to facilitate tumbling of the quenching gas to impact and quench hot metallic objects; and    decelerating the tumbling quenching gas to prevent the hot metal objects from being carried away.    
     
     
         14 . The method of  claim 13 , further comprising subjecting the hot metal objects to the tumbling quenching gas for a select period of time sufficient to quench the hot metal objects to a desired temperature.  
     
     
         15 . The method of  claim 13 , wherein the flow of the quenching gas is an upward flow.  
     
     
         16 . An apparatus for quenching hot metal objects in a upward flow of quenching gas, comprising: 
 a chamber having a lower region for receipt of a quenching gas, and an upper region having an increasing cross-sectional area; and    a planar floor member disposed between the lower region and the upper region, the planar floor member having a multiplicity of orifices therethrough for distribution of quenching gas from the lower region into the upper region in a tumbling flow to contact the hot metal objects and be decelerated.