Influence of the Local Hydrogen Concentration in Multi-Phase Steels on their Tendency to Hydrogen Induced Cracks

汽车车身和发电厂工程的高质量技术标准不断提高，导致高强度钢的使用增加。由于这些钢材的使用，例如在车身结构中可以减轻重量，从而降低燃料消耗。然而，运营条件必须适应这些新的需求。随着强度的增加，氢致开裂的敏感性也随之增加。众所周知，即使是少量的氢也会导致损害。这种氢在高晶格膨胀的区域，例如在缺口附近集中到更高的水平。在其他条件不变的情况下，铁素体、珠光体、贝氏体或马氏体等特定的组织成分对氢致开裂的影响尚不清楚。由于这些微结构被专门调整以增加强度，然而，这一知识将与高强度钢的安全使用相关。以前的项目能够证明高应力区域的氢浓度不断增加。对局部氢的分析表明，不同的结构修饰具有不同的行为。由于我们看到成功研究的巨大潜力，我们决定不提出第三年的支持，而是提出这一新的应用。该项目的目的是描述受力高强度多相钢的单一结构部分的临界氢浓度，并评估它们对钢的氢致开裂倾向的影响。这些研究成果将对氢致开裂控制高强度钢的进一步发展起到重要的推动作用。

Increasing technological high-quality standards of car body- and power plant engineering lead to an increased use of high-strength steels. Due to the usage of these steels it is possible for example in car body construction to reduce the weight and thus the fuel consumption. Operation conditions however have to be adapted to these new demands. With increasing strength the sensibility for hydrogen induced cracking rises, too. It is known that even low amounts of hydrogen can lead to damage. This hydrogen concentrates to a higher level in areas of high lattice expansion, e.g. near notches. If a limiting concentration has been met sudden component failure will occur.There does not exist any knowledge so far about the influence of specific microstructure constituents as e.g. ferrite, perlite, bainit or martensite on hydrogen induced cracking at conditions which other from that are constant. As these mirostructures are adjusted specifically to increase the strength, this knowledge however would be relevant for a safe usage of high-strength steels.Previous projectwas able to prove the increasing concentration of hydrogen in areas of high stress. The analysis of local hydrogen showed evidence of different behavior of various structure modifications. As we see high potential for successful research we decided not to propose a third year of support but to propose this new application.The aim of the project is to characterize single structure parts of stressed high-strength multi-phase steels concerning their critical hydrogen concentration and to evaluate their impact on the tendency to hydrogen-induced cracking of a steel. The obtained insights finally are supposed to significantly promote further development of high-strength steels with controlled hydrogen-induced cracking.