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Delayed fracture characteristics of high strength steel hardened state

 In the production of high-strength components, if it is low-carbon steel, but also for your use in the case in the quenched state. Adding Si infiltration of hydrogen can be suppressed to improve the delayed fracture (fracture time in this case). In the quenched carbide does not precipitate, as the position of the hydrogen capture only dislocations and grain boundaries, dislocations are evaluated according to the X-ray diffraction lattice distortion, grain boundaries are based on the measurement of grain size, grain boundary area After calculating the evaluation. After adding Si, trapping hydrogen position will be reduced, inhibited the infiltration of hydrogen. In the Si content is high, the phase transition point will rise, and therefore to increase the quenching temperature. As a result, the original austenite grain size will increase. Although the grain size is increased to a high Si steel the same, but no corresponding decrease in the lattice distortion, delayed fracture characteristics are not changed. It can be believed that the main factors affecting the delayed fracture Quenching is the reduction factor is greater than the grain boundary dislocations reduction factor.

In addition, high strength parts delayed fracture is a phenomenon that occurs under static load, but must also consider the parts subject to fatigue properties after repeated stress. When the high-strength steel, as long as there is a trace amount of hydrogen may fracture. Hydrogen can be seen will affect the fatigue properties. As we all know, high-strength steel inclusions occur due to fatigue fracture. Based on detailed observation of the fatigue fracture surface found that the presence of inclusions in the surrounding area is known as ODA (optically dark area), it will have a fracture due to hydrogen.
Automotive bearings under high temperature and pressure state and after use of lubricants and oil H react will penetrate the steel, has a relationship with the fracture of the steel, and therefore lubricant and steel development and improvement. As there are many parts of fatigue objects, carburizing and induction hardening of parts mostly high-strength steel, and therefore it is necessary to conduct material development in this view.