1、 Scope

    1. Parts with effective layer depth greater than 0.3mm for carburization and carbonitriding

    2. Parts with a hardness less than 450hv at twice the effective hardening layer from the surface after heat treatment to the final hardness value

    For steel parts that cannot meet the above conditions, the effective hardening layer depth can be determined separately through agreement. For parts with a hardness greater than 450hv at three times the effective hardening layer from the surface, an ultimate hardness value greater than 550hv can be used to determine the effective hardening layer depth.

    2、 Technical regulations

    1. After carburizing and carbonitriding quenching, the effective depth of the hardening layer is the vertical distance from the surface of the part to a Vickers hardness value of 550HV

    2. The test used for measuring hardness is 9.807N.

    In special cases, through agreement, the testing force within the range of 4.903N to 49.03N can also be used, or a surface Rockwell hardness tester can be used for testing

    3. The effective hardened case depth is expressed in the letter DC, and the unit is mm. The Significant figures is two digits after the Decimal separator.

    4. If other testing forces or other extreme hardness values are used, they should be indicated after the letter DC.

    3、 Sample and preparation

    1. The measurement of the depth of the hardened layer should be carried out according to the requirements of the drawing, at the designated location on the drawing

    2. According to regulations, measurements should be made on the cross-sectional area of the parts after final heat treatment

    3. Cut the sample on the vertical hardened surface, and use the section as the testing surface. The testing surface should be polished to a mirror surface. During the cutting and polishing process, pay attention not to affect the hardness of the testing surface due to temperature, deformation, etc. Do not chamfer the edges of the detection surface。

    4、 Hardness testing method

    1. Hardness indentation should be carried out within the specified width range of 1.5mm along one or more parallel lines perpendicular to the surface. The distance between two adjacent indentations should not be less than 2.5 times the diagonal of the indentation.

    2. Based on each curve plotted, the vertical distance from the surface of the part to 550HV can be obtained. If the difference between these two values is less than or equal to 0.1mm, their average value is taken as the effective hardened layer depth; If the difference is greater than 0.1mm, repeat the test to verify accurate data.