Study on Submerged Arc Welding with Bonded Flux (8th Report)

Properties of Welded Metal for 9%Ni Steel

Abstract

Performances of submerged arc welds by using a bonded flux experimentally produced for low temperature material (Aluminum killed steel, 35% Ni steel) were described in the previous report.
Using the bonded flux experimentally manufactured for the purpose of achieving automatic welding of 9% Ni steel for lower temperature use (from -101°C to-196°C) use, the tests of tensile strength and impact vafue at low temperature of submerged arc welded metal have been conducted.
The results obtained are summarized as follows:
(1). Because the bonded flux H-900 for 9% Ni steel is low hydrogen type of mixture without SiO₂ content it is somewhat poor in operating property, whereas the use of direct current reversed polarity results in good operating property and bead weld.
(2) The mechanical properties of 9% Ni steel plate at -196°C were satisfactory : 100 kg/mm₂ in tensile strength, 80 kg/mm₂ in yield point, 20% in elongation and 6 kg-m in impact value. Accordingly, when designing equipments with this steel, it is possible to reduce its thickness considerably.
(3) The mechanical properties of all deposited metal at -196°C are 87 kg/mm₂ in tensile strength, 55 kg/mm₂ in yield point, 30% in elongation, and 3.5 kg-m in impact value, all of which satisfy the standards at low temperature prescribed in ASTM.
(4) The highest hardness of heat-affected zone is approximately 360 in Hv as welded, while it decreases to about 290 in Hv after stress relief annealing at 570°C for 2 hours. There is found no transverse crack of bead weld and no crack of heat-affected zone, but the non-removed crater leads to a development of crater cracks.