- Welding heat input
In the actual high-frequency straight seam steel pipe welding process, the welding power used directly determines the heat input of the steel pipe welding. When the external conditions are certain and the heat input is insufficient. The heated strip edge can not reach the welding temperature, still maintain a solid structure, thus forming a cold weld, and even can not be fused.
This incomplete fusion is usually manifested in the flattening test failed. Pipe bursting during hydrotesting or weld cracking during pipe straightening is a serious defect. In addition, weld heat input can be affected by the quality of the strip edges. For example, when the strip has a burr on the edge, the burr causes a spark before it enters the weld joint at the extrusion roll, resulting in a loss of weld power and reduced heat input, resulting in an incomplete melt or cold weld. When the heat input is too high, the edge of the heating tape exceeds the welding temperature, resulting in overheating or even excessive burning, the weld cracks under pressure, and sometimes the molten metal splatters to form holes due to weld rupture.
- Welding pressure (reduce)
Welding pressure is very important in the welding process, especially when the strip edge is heated to a certain welding temperature. The metal atoms combine with each other to form the weld seam under the squeezing pressure of the extrusion rollers. Welding pressure affects the strength and toughness of the weld. If the applied welding pressure is too low. Weld edges can not be completely melted, the weld residual metal oxides can not be discharged to form inclusions, resulting in a significant reduction in the tensile strength of the weld, the weld is easy to crack after stress. Of course, the same, if the welding pressure applied in the welding process is too high, most of the metal up to the welding temperature will be squeezed. This not only reduces the strength and toughness of the weld, but also produces defects such as excessive internal and external burrs or lap welds.
Welding pressure is usually measured and judged by the variable diameter of the tube before and after the squeeze roll and the size and shape of the burr.
- The effect of welding squeeze on the shape of the burr
Welding extrusion is too large, spatter, extrusion of molten metal, burr, molten metal on both sides of the weld flip; extrusion is too small, almost no spatter, burr small, pile up. When the amount of extrusion is moderate, the extruded burr is vertical, and the height is generally controlled at 2.5 ~ 3 mm. If the amount of welding extrusion is controlled, the angle of the metal flow line of the weld is basically symmetrical up and down, with an angle of 55 ~ 65.
