In the welding industry, the position and shape of the weld seam have a significant impact on the quality and efficiency of the weld. Similar to the 1G to 5G nomenclature of communication technology, the welding field has also divided weld positions from 1G to 6G. These division criteria cover not only bevel and plate fillet welds, but also pipe plate or pipe fillet welds.
Weld Position Division
1. Bevel welds: 1G to 6G represent flat, transverse, vertical, backside, horizontal pipe tack welds and inclined 45-degree pipe tack welds, respectively.
2. Plate fillet welds: 1F, 2F, 3F and 4F correspond to shipboard weld, transverse weld, vertical weld and elevation weld respectively.
3. Pipe plate or pipe fillet welds: 1F, 2F, 2FR, 4F and 5F correspond to 45-degree rotation welds, transverse (pipe axis vertical) welds, pipe axis horizontal (rotation) welds, and elevation pipe axis horizontal (fixed) welds, respectively.
Introduction to Flat Welding
1G is flat welding.
Welding Characteristics:
1. The molten weld metal mainly relies on self-weight to the molten pool over.
2. The shape of the molten pool and the molten metal are easy to maintain and control.
3. Welding the same plate thickness of metal, flat welding position of the welding current than other welding position of the current, high productivity.
4. The slag and the molten pool are easy to be mixed, especially when welding flat fillet welds, the slag is easy to overrun and form slag inclusions. Acid electrode slag and molten pool is not easy to distinguish; alkaline electrode both clearer;
5. Welding parameters and improper operation, easy to form weld tumor, biting edge and welding deformation and other defects.
6. When the back of the single-sided welding free molding, the first weld is prone to produce uneven weld penetration procedures, the back of the poor molding and other images.
Welding points:
1. According to the thickness of the plate can choose a larger diameter welding rod and larger welding current welding.
2. Welding rod and weldments into 60 ° ~ 80 ° angle, control the slag and liquid metal separation, to prevent the slag from appearing ahead of the phenomenon.
3. When the plate thickness ≤ 6mm, butt-flat welding generally open Ⅰ bevel, the front weld should be φ3.2 ~ 4 of the electrode short arc welding, depth of fusion up to 2 / 3 of the plate thickness; the back of the back cover before the bottom, you can not clear the root (except for the important structure), but the slag should be cleaned up, the current can be larger.
4. Butt flat welding if there is slag and pool metal mixing phenomenon, you can lengthen the arc, welding rod forward, and do to the back of the pool to push the slag action, to prevent slag generation.
5. Welding horizontal inclined weld, it is appropriate to use uphill welding to prevent slag and molten pool to the front to avoid slag.
6. When using multi-layer multi-channel welding, attention should be paid to the number of weld passes and welding order, each layer should not exceed 4~5mm.
7. T-type, angle and lap welding joints, if the thickness of the two boards are different, should adjust the angle of the electrode will be biased towards the thick side of the arc, so that the two boards are heated evenly.
8. The correct choice of transport method
(1) welding thickness ≤ 6mm, Ⅰ type bevel butt welding, using double-sided welding, the front weld using straight-line transport bar, a little slow; back weld also use straight-line transport bar, welding current is slightly larger, faster.
(2) plate thickness ≤ 6mm, open other forms of beveling, can be used for multi-layer welding or multi-layer multi-channel welding, the first layer of bottoming welding should be used for small current electrodes, small specification current, linear electrode or sawtooth shaped electrode welding. Filler layer welding, can choose a larger diameter electrode and larger welding current short arc welding.
(3) T-type joints, flat angle welding foot size <6mm, can choose a single layer of welding, with a straight line, diagonal ring or serrated rod method; foot size is larger, it is appropriate to use multi-layer welding or multi-layer multi-channel welding, bottoming weld with a straight line rod method, filler layer can be used to select the diagonal sawtooth, diagonal ring rod.
(4) Multi-layer multi-pass welding is generally preferred to use linear rod welding method.
Introduction of cross welding
2G is cross welding.
Welding characteristics:
1. The molten metal is easy to fall on the bevel due to self-weight, resulting in the upper side of the biting defects, the lower side of the formation of tear-drop weld bead or weld defects.
2. The molten metal and slag are easy to separate, slightly like vertical welding.
Welding points:
1. butt cross weld beveling is generally V-type or K-type, plate thickness 3 ~ 4mm butt joints available Ⅰ bevel double-sided welding.
2. Choose a small diameter electrode, welding current is smaller than the flat welding, short arc operation, can better control the flow of molten metal.
3. thick plate welding, in addition to the bottom weld, it is appropriate to use multi-layer multi-channel welding.
4. multi-layer multi-channel welding, pay special attention to the control of the overlap distance between the welding channel. Each overlap welding, should be in the previous weld 1 / 3 of the beginning of welding, in order to prevent the production of unevenness.
