Study on Mechanical Properties and Failure Mechanism of Deep Seam Electron Beam Welding of Ultra-high Strength 300M Steel

Abstract

The ultra-high strength 300M steel is applied in aircraft landing gear because of excellent mechanical properties. The tests of static tensile strength, three-point bending properties and Charpy impact properties are conducted. It reveals the mechanical properties and failure mechanism of electron beam deep seam welding of 300M steel. Macroscopic and microscopic analysis of typical specimens fracture after testing and fractography of weldment fracture surface are investigated by SEM(scanning electron microscope). Results indicate that both parent metal and weldment appear obvious tension plastic behavior, and there is little difference between stiffness and strength. However, the fracture strain and toughness of weldment become weaker compared with the parent metal. The bending strength of weldment is slightly lower than that of the parent metal, and the bending deformation and ductility decline. In Charpy impact test, both absorbed energy and fracture toughness of weldment are lower than parent metal. Thus the impact toughness of weldment decreases.

Keywords

• ultra-high strength 300m steel
• deep weld seam
• electron beam welding
• tensile strength
• bending strength
• impact toughness