Study on Submerged Arc Welding with Bonded Fluxes (6 th Report)
Properties of Weld Metal for 70, 80kg/mm2 High Tensile Strength Steel
1965 Volume 34 Issue 9 Pages 895-902
Details
1965 Volume 34 Issue 9 Pages 895-902
In the previous reports, characteristics of bonded flux and various properties of weld metal which was deposited by submerged arc welding with expermentally manufactured bonded flux for stainless steel, low carbon steel and high tension steel up to 60 kg/mm2 was described. This time, bonded fluxes was manufactured for the purpose of automatic welding on steels having 80 kg/mm2, that is, super high tension steels which have been required for the manufacturing of chemical phants equipment, spherical thnks and rail cars due to rapid progress of various industries. Primarily tensile strength and low temperature impact properties of weld metal was obtained by using this flux. The summary of the results of this invesigation is the following.
(1) Bonded flux for superior high tension steel is made of fundamental composition of bonded flux H-550 for low carbon steel. Its operational property is good and formation of bubbles is not observed in weld beads. Certain irregularities are observed, however, on beads' surface due to deposition of added deoxydizer and alloying elements.
(2) In welding of superior high tension steel of 70 kg/mm2 class, the combinations of flux and wire S-7 C+H-555 and #56+H-700 gives weld metal of good tensile strength and tonghness, and welding of superior high tension steel of 80 kg/mm2 class, the combinations of S-7 C+H-803 and #56+H-600 gives good result.
(3) The maximam hardness of heat affedted zone by welding for 2 H ultra steel of 80 kg/mm2 class becomes about Hv : 350 in as welded, condition and by stress reliving annealing yf 600°C 1 h, the hardness decreases some what. Also 7 QC of 70 kg/mm2 class has the maximum hardness of about Hv : 300.
(4) According to Fisco cracking test result, crack occurs 100% for welding at ordinary temperature even for any combination. Therefore, in welding, preheating to 250°C-300°C is neccessary.
(5) Welded jonts of 80 kg/mm2 class steel with conbination of 056+H-800 showed fatigue strength of about 48 kg/mm2 against repeated tension load of 2 × 106.
