4.1 Decarburization and carburization are two surface conditions created, either intentionally or unintentionally, as with a pre-existing condition created during the rod rolling process, the rod/wire annealing process, or while heat treating threaded steel products. Too much of either will adversely affect the safety and performance of the threaded product. Therefore, limits have been established for three different product groups: the harder and greater the tensile strength of the product, the more susceptible to failure the product becomes if these limits are exceeded.

4.2 When testing to a particular product specification that lists the dimensions and microindentation data to be used, that data shall take precedence over the tables in this test method.

4.3 There are only two viable methods available to detect these deficiencies, either by the visual method or the microindentation method. Both methods are used for routine inspections when evaluations are conducted at a single location on the product sample.

4.3.1 Because an evaluation at a specific location may not be representative of the whole part, the referee method employs the microindentation method taken as an average of evaluations conducted on four adjacent threads. This procedure significantly reduces the random test variables when compared to testing on a single thread.

4.4 Specifying this test method does not specify or imply that testing shall be for either decarburization or carburization alone or for both conditions. When either test method is performed, both conditions will be apparent and shall be reported. For example, if an order is placed to test for decarburization and none is found, but the presence of carburization is detected, it shall be reported on the test report that carburization was found.