Case study: Our steel is in space

The aerospace industry is undergoing rapid growth, driven by an increasing number of research and commercial space missions. With it rises the demand for materials capable of withstanding some of the harshest environments. These materials must demonstrate outstanding performance in terms of thermal stability, mechanical strength, fatigue resistance, and long-term reliability.

Meeting these challenges requires more than just manufacturing capability – it calls for expertise in metallurgy, R&D, and process integration. SIJ Group has proven it can meet these expectations and more.

Challenge: Engineering steel beyond industry standards

A client approached SIJ Group with a unique challenge: they required custom-developed steel with a specific chemical composition and physical and mechanical properties that exceeded those of typical industrial alloys.

The requested material was intended for structural elements that had to withstand thermomechanical stress and thermal cycling.

Due to this demanding application, the steel required exceptional mechanical properties and the ability to withstand rapid temperature changes as it transitioned from the extreme heat of propulsion engine operation to extremely low temperatures outside Earth's orbit.

What set SIJ Group apart during the selection process?

• Proven track record in R&D and high-performance alloys
• Extensive process integration across both SIJ Group steel mills
• Fast development cycles – offering a two-month turnaround vs. a two-year lead from competitors
• Commitment to quality with in-house labs and rigorous quality management
• Flexibility and close client collaboration

Approach: From lab to launchpad

Feasibility assessment & planning

Our metallurgists and R&D specialists first evaluated the feasibility of producing steel that matched the client’s specifications. Together, we created a plan which covered the development path from laboratory test melts to industrial-scale production.

Laboratory scale testing

Partnering with the Institute of Metals and Technology, Slovenia (IMT), we produced two lab-scale melts. These allowed us to:

• Verify chemical composition
• Evaluate mechanical and physical properties
• Simulate processing behaviour

Continuous collaboration with the customer ensured real-time feedback and agile development.

Industrial-scale production

Following successful lab results, we scaled up to full industrial production using the combined technological capabilities of SIJ Acroni and SIJ Metal Ravne.

Steel was cast at SIJ Metal Ravne, where Electro Slag Remelting (ESR) was used to ensure high material purity. The material was then forged into large blocks or slabs, followed by ultrasonic testing. The steel was transported to SIJ Acroni, where it was ground and cut to dimensions suitable for further processing.

The material was heated in a pusher-type furnace and rolled, producing long plates that were subsequently solution-treated. The steel was then transported back to Ravne na Koroškem, where it was cooled in liquid nitrogen. Afterwards, it was returned to SIJ Acroni for final heat treatments, including annealing and ageing. The process concluded with surface treatments, straightening, and shotblasting.

Quality control

Throughout the process, in-house laboratories conducted extensive testing to ensure conformance to required specifications. Every stage was closely monitored under our certified quality management systems, ensuring consistent results and traceability.

The suitability of the steel was also confirmed through independent third-party testing, as well as the client’s own verification.

Results: Delivering high-performance aerospace steel

• 500 tons of steel were delivered (solution annealed, supercooled, and precipitation hardened) with a new order of 600 tons secured. 
• Independent third-party testing, as well as the client's own verification, confirmed compliance with performance and safety criteria.
• The final product was used in components of the rocket, functioning in zones with extreme temperature variation and high stress.
• This material now plays a key role in ensuring mechanical stability and long-term reliability in one of the most demanding operational environments known to engineering – space.

A trusted partner for the future of space

This project confirms SIJ Group as a reliable, strategic development partner for the space industry, able to:

• Develop tailored materials 
• Accelerate time-to-market with rapid development cycles (2 months vs. 2 years)
• Integrate advanced technologies and R&D
• Deliver high-quality steel for critical applications

Our successful collaboration with the aerospace client underlines the capabilities of Slovenian industry to supply high-quality materials for global high-tech applications.