A PROCESS OF PRODUCING SOUND WELDED JOINTS FOR ATMOSPHERIC AND MARINE-CORROSION RESISTANT STEEL BARS

摘要

The invention provides a process of producing sound welded joints, which are adequately strong and free from welding defects, In atmospheric-corrosion resistant (Cu-TMT) steel bars and marine-corrosion resistant (Cu-Cr-TMT) steel bars, comprising the steps: (a) preparing the joint areas of the steel bars in known methods, (b) selecting the electrode wire of low hydrogen type conforming to AWA A 5.5 E 8018-W code and its coating material of suitable type, (c) using up to 7 passes for butt-welding, (d) following the conditions for butt-welding as (l) both Cu-TME and Cu-Cr-TMT bars are welded without being preheated; (ii) for welding Cu-THT bars, electrodes are used without being rebaked; (iii) for welding Cu-Cr-TMT bars, electrodes are used after baking at 350°C for 2h or at 400°C for 1h; (iv) both Cu-TMT and Cu-Cr-TMT .. bars are welded at a heat input of 7-10 KJcm-1 for electrode diameter of 2,5 mm and 10-15 KTcm1 for electrode diameter of 3.15 mm; (v) both Cu-TMT and Cu-Cr-TMT bars are welded at a current-voltage-heat input combination of 80-1OOA, 20-24V, 7-10 KJcm1 for electrode diameter of 2.5 mm; and of 100-140A, 22-25V, 10-15 KJcm1 for electrode diameter of 3.15 mm; and (vi) both Cu-TMT and Cu-Cr-TMT bars are welded at an electrode inter-pass temperature of 225°C max. and without any post-welding heat treatment of the bars; and for lap welding as (i) both Cu-TMT and Cu-Cr-TMT bars are welded without being preheated; (ii) for welding Cu-TMT bars, electrodes are used without being rebaked and for welding of Cu-Cr-TMT bars, electrodes are rebaked at 350°C - 2 hrs or 400°C - 1 hr before use; (ill) both Cu-TWT and Cu-Cr-TMT bars are welded at heat Input of 7-10 KJcm1 for electrode diameter of 2.5 mm; and (iv) Cu-TMT bars are welded at an overlapped length of 70 mm (min.) and Cu-Cr-TMT bars are welded at an overlapped length of 100 mm (min.).