Fraunhofer Institute for Mechanics of Materials IWMHydrogen embrittlement causes unexpected edge cracks during the forming of high-strength galvanized steels, rendering entire production batches scrap. This project systematically unravels the interplay between cutting processes, dwell time, and hydrogen diffusion at the cut edges of high-strength steels. By combining a defined hydrogen loading, state-of-the-art microstructure analysis, and coupled simulation, the time-dependent damage mechanism is quantified. The results lead to practical recommendations for optimal process routes (cutting – storage – forming). This enables companies to safely exploit the full formability of high-strength steels while drastically reducing scrap costs.
Prevention of hydrogen-induced cracking in prefabricated blanks and semi-finished products
Ongoing research project
Project description
Market Demand and Challenges
High-strength dual-phase and complex-phase steels are key materials for lightweight automotive construction, roll forming, and, increasingly, for components in the hydrogen economy. Their processing—cutting close to the final contour followed by forming—is energy- and resource-efficient and is extensively used in forming technology, toolmaking, and metalworking. During shear cutting of galvanized high-strength sheets, a zone of extreme deformation and high residual stresses forms at the cut edge. Hydrogen trapped in the steel by the zinc coating diffuses into this zone over time. This results in spontaneous edge cracks during subsequent forming—often only after a certain dwell time between cutting and further processing. Until now, it has not been possible to predict this failure.
Contribution of the Project
The IGF project “H2 Cracking” systematically investigates the interaction between cutting methods (shear cutting, laser cutting, waterjet cutting), time-dependent hydrogen diffusion, and edge crack susceptibility. At Fraunhofer IWM, samples are intentionally hydrogen-loaded, their cut edges are characterized using nanoindentation, EBSD, and hydrogen analysis (TGH/TDS), and coupled microstructure and diffusion simulations are performed. The Fraunhofer IWU is conducting three complementary edge crack testing methods while systematically varying holding time, hydrogen loading level, and material. The key results yield two recommendations for action: one for optimal process routes (the sequence of cutting–aging–forming) and one for suitable testing methods to evaluate the edge crack susceptibility of hydrogen-loaded sheet metal.
Fraunhofer IWM’s work packages in the project:
Fraunhofer IWM sets defined hydrogen concentrations and analyzes the hydrogen using thermal desorption spectroscopy (TDS) and carrier gas hot extraction (TGH). In addition, the institute analyzes the interaction between highly formed regions and hydrogen absorption to provide the basis for validating simulation models.
Fraunhofer IWM is developing a coupled simulation approach that quantifies the influence of the highly deformed microstructure at the cut edge on hydrogen embrittlement. This simulation is intended to enable a quantitative prediction of when and where critical hydrogen concentrations are reached at the cut edge, thereby allowing the derivation of general rules for minimizing the risk of failure.
Based on the project results, Fraunhofer IWM can offer industrial companies the following research and development services:
Assessment of hydrogen sensitivity for high-strength steels
Fraunhofer IWM offers comprehensive characterization, including defined hydrogen loading, microstructure analysis using EBSD and nanoindentation, as well as quantitative hydrogen measurement via TDS and TGH. In addition, hydrogen permeation measurements and mechanical characterization of materials after hydrogen loading or under in situ loading can be performed.
Benefits for you:
- Reliable conclusions regarding whether—and after what dwell time—your own process chain poses a risk of hydrogen-induced edge cracks
- Avoidance of costly batch failures through early risk detection
- Reliable and well-founded process planning based on material-specific measurement data
- Determination of materials’ susceptibility to hydrogen embrittlement
Coupled microstructure and hydrogen diffusion simulation for individual materials and processes
Fraunhofer IWM develops material- and process-specific simulation models that quantitatively calculate the time-dependent redistribution of hydrogen in different microstructural states.
Your benefits:
- Virtual determination of critical dwell times, optimal process sequences, and safe forming windows
- Significant reduction in time-consuming and expensive experimental test series
- A digital tool for process design and proactive damage prevention
