Strength, Ductility/Toughness and Fine-Blanking of Nonmagnetic High Mn Steel and Its Accelerator Superconducting Magnets Application

Abstract

The authors have developed anew a nonmagnetic steel (KHMN) containing high Mn content up to 30% for the cryogenic uses, being engaged in its application to accelerator superconducting magnets as structural materials. A paper is proposed here to present some experiments and discussions related to the strength, ductility/toughness and fineblankability of the steel and also its R/D applications to particle accelerator magnets: (1) The high strength is essential at cryogenic temperature to sustain the magnetic force. However, it depends on a magnet design and relates to fine-blanking behavior at room temperature. The developing steel shows that the strength is controllable with almost no degradation of magnetic permeability. (2) The low temperature ductility/toughness is not negligible, particularly in case of the magnet like a LHC insertion quadrupole. The present steel will be described in terms of such experimental results. (3) The fine-blankability of the steel developed is studied in connection with the strength at the ambient temperature as mentioned above. An innovated technique will also be reported associated with the stacking process. (4) This nonmagnetic high Mn steels have been trially applied to accelerator magnets collar for the on-going LHC R/D works compared with the previous SSC project as well.