“Hydrogen embrittlement” is a term that is not commonly used, but it is the most important phenomenon for the screw and bolt industry. (In other words, this is the point that those involved in the screw industry should pay the most attention to during manufacturing). Metals have a property of absorbing hydrogen, and when hydrogen is absorbed, the crucial toughness in iron and stainless materials is lost. Particularly for screws and bolts, especially for high-strength bolts that undergo heat treatment, during processes like galvanizing high-strength bolts, hydrogen can be absorbed, or factors like the heat during plating can cause a sudden loss of toughness, making them brittle. The preventive measure is to perform a baking process (dehydrogenation process). However, for bolts with high hardness of 10.9 or higher, manufacturers do not recommend this practice. gilding process. Therefore, in this case, it is necessary to pay attention that the dry firing process does not guarantee hardness.