Melt pool temperature, directly affects the quality of welding, high melt pool temperature, larger melt pool, good fluidity of iron, easy to fusion, but too high, the iron is easy to flow, single-sided welding double-sided forming the back side is easy to burn through, the formation of weld tumor, forming is also difficult to control, and joint plasticity decreases, bending easily to crack.
When the melt pool temperature is low, the melt pool is smaller, the iron is darker, poor mobility, easy to produce not welded through, not fused, slag, and other defects.
Melt pool temperature and welding current, welding rod diameter, welding rod angle, arc burning time, etc. have a close relationship, for the relevant factors to take the following measures to control the melting pool temperature.
1. Welding current and welding rod diameter
According to the spatial location of the weld, welding levels to choose the welding current and electrode diameter, open welding, the choice of welding current and electrode diameter is larger, vertical, horizontal elevation position is smaller.
Such as 12mm flat plate butt welding of the sealing layer selected φ3.2mm welding rod, welding current: 80-85A, filling, cover layer selected φ4.0mm welding rod, welding current: 165-175A, a reasonable choice of welding current and diameter of the welding rod, easy to control the temperature of the melt pool, is the basis of the weld forming.
2. The transport method
Circle-shaped transport strip melt pool temperature is higher than the crescent-shaped transport strip temperature, crescent-shaped transport strip temperature is higher than the melt pool temperature of the serrated transport strip, in 12mm flat welding seal bottom layer, the use of serrated transport strip, and with the amplitude of swing and pause on both sides of the bevel, effective control of the melt pool temperature, so that the melt hole size is basically the same, the root of the bevel is not formed weld tumor and burn through the chances have decreased, not weld through has improved, so that the plate Butt welding of single-sided flat welding double-sided forming is no longer a difficult point.
3. Welding rod angle
The angle of the welding rod and welding direction at 90 degrees, the arc concentration, the high temperature of the pool, the angle is small, the arc dispersion and the pool temperature is low, such as a 12mm flat welding seal bottom layer, welding rod angle 50-70 degrees, so that the pool temperature has decreased, to avoid the back of the weld tumor or up high.
Another example is in the 12mm plate vertical welding seal bottom layer after changing the welding rod, the joint using 90-95 degrees of the welding rod angle so that the melt pool temperature quickly increased, the melt hole can be smoothly opened, the back of the formation of a flatter, effective control of the joint point concave phenomenon.
4. Arc burning time
φ57×3.5 tube of horizontal fixed and vertical fixed welding practice teaching, using the arc-break method of welding, sealing bottom layer welding, the frequency of arc-break and arc burning time directly affects the melt pool temperature, due to the thin wall of the tube, arc heat tolerance is limited, if the arc-break frequency to reduce the temperature of the melt pool, easy to produce shrinkage.
Therefore, can only use the arc burning time to control the melt pool temperature, if the melt pool temperature is too high, the melt hole is larger, the arc burning time can be reduced to make the melt pool temperature lower, at this time, the melt hole becomes smaller, the tube internal forming height is moderate, to avoid the tube internal welding seam is super high or produce welding tumor.