SSAB

Investigation of the fracture toughness of hot-rolled steel grades for fine blanking applications-correlation with blanking behaviour

SSAB is a global steel company with a leading position in high-strength steels and related services. With a strong Nordic heritage, SSAB is committed to revolutionizing steelmaking to offer fossil-free steel and reduce carbon emissions.

The company’s innovative high-strength steels contribute to lighter and more fuel-efficient products, making a positive impact on the environment. SSAB’s core values of creating value together, doing what is right, and keeping the future in mind drive its global presence and dedication to being the preferred innovation partner for customers, building lasting relationships based on trust and responsibility.

Motivation

Investigation of the fracture toughness of hot-rolled steel grades for fine blanking applications. The primary objective was to explore potential correlations between fracture toughness and the cutting behaviour of these hot-rolled steels.

In the final application, hot-rolled grades are frequently utilized with punched, sheared, or fine-blanked edge conditions. The study aimed to shed light on this aspect and provide valuable insights for optimizing the selection and performance of hot-rolled steels in fine-blanking applications.

Under the framework of Toughsteel we could analyse five steel grades in terms of fracture toughness and found distinctive differences between the materials. Now we want to understand how to influence these properties for further material optimisation

Vili Kesti, Senior Forming Specialist, SSAB Europe

Case study results

The fracture toughness of five hot-rolled steel grades with similar tensile strength (around 800 MPa) but different microstructures has been characterized by means of the EWF methodology.

In parallel, SSAB performed hole expansion, punching and fine-blanking tests in some steel grades. The aim was to identify correlations between fracture toughness and the cutting behaviour of the studied hot-rolled steels.

Fracture toughness results showed large differences in the crack propagation resistance of the different steels. A good correlation between we and hole expansion ratio was obtained for most of the steels.

The different behaviour in fine blanking tests was very well correlated with fracture toughness values.

The study concluded that EWF testing may be a very useful tool to analyse in detail the crack propagation behaviour of hot rolled steel grades during cutting or blanking.

Other aspects like the effect of microstructure on the steel grades studied are open for further research.

Results for the SSAB case study. Comparison between fracture behaviour in fracture tests and punching.