REPUBLIC OF SERBIA

MINISTRY OF DEFENCE

www.mod.gov.rs

MINISTRY OF DEFENCE

Material Resources Sector

Defensive Technologies Department

Military Technical Institute

www.vti.mod.gov.rs

The influence of the heat treatment on the properties of flow formed rocket motor cases of 30crMoV4 and

41cr4 steels

milutin nikačević

Military Technical Institute, Belgrade, nikacevic.milutin@gmail.com

LJUBICA RADOVIĆ

Military Technical Institute, Belgrade

JELENA MARINKOVIĆ

Military Technical Institute, Belgrade

Abstract: The aim of this work was to evaluate the possibility of substitution of 30CrMoV9 steel with cheaper 41Cr4 for rocket motor cases. Different heat treatments applied on the preforms, resulted in different microstructures and tensile strength from 700 MPa to 1000 MPa. Flow forming was performed using mandrels with diameters of 50 mm and 122 mm. Total and partial wall thickness reductions were varied. Microstructure, mechanical properties, toughness and macroscopic residual stress of the preforms, as well as flow formed tubes, were examined. It was shown that in some cases 30CrMoV9 steel can be substituted with 41Cr4 steel.

Keywords: rocket motor case, flow forming, 30CrMoV4 steel, 41Cr4 steel.