A method of and apparatus for determining the required surface hardening conditions for cylindrical workpieces

摘要

In a method for determining the appropriate conditions for the surface hardening of cylindrical workpieces such as rolls there is produced from the workpiece a sample segment having an arcuate face conforming to the cylindrical surface of the workpiece. The plane faces of this segment are lagged with thermally insulating material, and the segment is then heated and quenched from the arcuate end face. Temperature distribution during treatment may be monitored continuously by means of thermocouples inserted into the specimen, or the treated specimen may be subsequently examined micrographically. Preferably the examined micrographically. Preferably the sample is in the form of a sector-shaped prism taken from a disc-shaped section of the workpiece. In the case of rolls, the sample disc may be cut off prior to forging of the roll necks, may be taken from the end of a neck, or the roll may be forged with one neck larger than the other and an annular disc then removed whose outer diameter is that of the roll face and inner diameter that of the neck. The method is applicable both to induction and flame-hardening processes. Where hardening of the roll is carried out by passing it axially through a ring inductor, so that some axial flow of heat occurs it is preferable to use prisms as shown in Fig. 4 in which the height substantially exceeds the width. In a particular form of apparatus (Fig. 5), segment 8 on holder 15 may oscillate about axis 16 in either of positions 18 or 19. In position 18 the segment moves with its arcuate face in close proximity to inductor 20, while in position 19 it is subjected to water spray 22. Action of the spray is preferably confined to face by means of shield 23 shaped as shown in Fig. 6.