螺旋钢管焊缝处理
Weld treatment of spiral steel pipe
螺旋钢管将带钢送入焊管机组，经多道轧辊滚压，带钢逐渐卷起，形成有开口间隙的圆形管坯，调整挤压辊的压下量，使焊缝间隙控制在1~3mm，并使焊口两端齐平。  1.如间隙过大，则造成邻近效应减少，涡流热量不足，焊缝晶间接合不良而产生未熔合或开裂。  2.如间隙过小则造成邻近效应增大，焊接热量过大，造成焊缝烧损;或者焊缝经挤压、滚压后形成深坑，影响焊缝表面质量。  将管坯的两个边缘加热到焊接温度后，在挤压辊的挤压下，形成共同的金属晶粒互相渗透、结晶，最终形成牢固的焊缝。螺旋钢管若挤压力过小，形成共同晶体的数量就小，焊缝金属强度下降，受力后会产生开裂;如果挤压力过大，将会使熔融状态的金属被挤出焊缝，不但降低了焊缝强度，而且会产生大量的内外毛刺，甚至造成焊接搭缝等缺陷。
The spiral steel pipe will send the strip steel into the welded pipe mill, and the strip steel will be rolled up gradually to form a round tube blank with opening gap. Adjust the reduction of the extrusion roller to control the weld gap within 1 ~ 3 mm and make both ends of the weld flush. 1. If the gap is too large, the proximity effect will be reduced, the eddy current heat will be insufficient, and the weld intergranular joint will be poor, resulting in incomplete fusion or cracking. 2. If the gap is too small, the proximity effect will be increased, and the welding heat will be too large, which will cause the welding seam burning; or the weld will form a deep pit after extrusion and rolling, which will affect the surface quality of the weld. After the two edges of the tube blank are heated to the welding temperature, the common metal grains are formed under the extrusion of the extrusion roller, which permeates and crystallizes with each other, and finally forms a firm weld. If the extrusion force of spiral steel pipe is too small, the number of common crystals will be small, the strength of weld metal will be reduced, and cracks will occur after stress; if the extrusion force is too large, the molten metal will be extruded out of the weld, which will not only reduce the weld strength, but also produce a lot of internal and external burr, and even cause defects such as welding lap joint.