Solving the Solidification Cracking in Maraging Steel during Mass Production by Adjusting High-Temperature Delta Ferrite

Abstract

Maraging steels hardened by Cu + NiAl precipitation have recently garnered attention owing to their relatively low cost and exceptionally high strength. However, the high alloy content can cause issues such as solidification cracking, particularly in mass production. In this study, solidification cracking was observed in a Cu + NiAl-hardened maraging steel manufactured via an electroslag remelting process, and an improvement strategy was adopted to solve this problem. Increasing the aluminum content from 1.0 wt.% to 1.2 wt.% can adjust the δ ferrite, which affects the thermal expansion coefficient and density of the system, thereby reducing the rate of cooling shrinkage. The extra addition of 0.2 wt.% aluminum had a negligible effect on the final microstructure and mechanical properties, with both steels demonstrating excellent tensile properties. The reduction in internal stress from the increased aluminum content was also confirmed using X-ray diffraction (XRD) measurement and the finite element method (FEM). This strategy provides valuable insights for the manufacturing of such high-alloy steels on a mass production scale.

Keywords

• maraging steel
• solidification
• cracking
• aluminum
• δ ferrite