Tempering - Temperature - Audit Test
This test is a means for checking whether products were tempered at the specified temperature. The hardness (mean hardness of three hardness readings) of a bolt, screw, or stud as manufactured shall be measured. The product shall be retempered for a minimum of 30 min. per 25 mm of nominal diameter, but not less than 30 min., at a temperature 10C less than the minimum tempering temperature specified for the property class and material (See 4.4.4.1 The hardness of the retempered product shall then be measured. The difference between the hardness of the product before and after retempering shall not exceed 2 points HRC for DX520506 and 3 points HRC for DX520504 and DX520505.