Maraging steel is vacuum induction melted plus vacuum arc melted, low carbon Nickel-Cobalt-Molybdenum High Temperature Alloy capable of attaining yield strength in excess of 240 ksi through a heat treatment. The steel exhibits good ductility coupled with high strength and is readily weldable. A aging heat treatment in the temperature range of 454-514 deg C from the solution treated condition will results in high strength.
The chemical composition of the steel is given below:
C-0.03max Mn-0.10max P-0.01max S-0.01max Si-0.10max Ni-18.50 Mo-4.80
Co-7.50 Ti-0.40 Al-0.10 B-0.003 Zr-0.01
Welding was performed on two thicknesses,namely, 5mm and 10mm. Gas tungsten arc welding was adopted using ultra high purity Argon. Matching filler wire was used in all welding trials.Test coupons were welded in solution annealed condition and the weldment was aged after welding and also welding was carried out after solution treatment and aging. The aim was to optimise heat-input to ensure that the development meets the stringent fracture toughness specified apart from meeting the tensile requirements. All the experiments done and the results obtained were compiled in a report which was handed over to MIDHANI which in turn forwarded the report to the customer. This was one of the contract development by R&D of BHPV.
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