1G To 6G in The Welding Industry: Weld Positioning And Welding Techniques

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 welding generally open Ⅰ bevel, front weld should be φ3.2 ~ 4 of the electrode short arc welding, the 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 welding rod method.

Introduction to cross-welding
2G is cross weld.
Welding characteristics:
1. The molten metal is easy to fall on the bevel due to self-weight, resulting in biting defects on the upper side and tear-drop weld beads or unwelded defects on the lower side.
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.
5. According to the specific conditions, maintain the appropriate welding rod angle, welding speed should be slightly block and uniform.
6. Use the correct method of transporting the rod.
(1) Ⅰ type butt cross weld, the front weld using reciprocating straight line welding method is better; slightly thicker parts should be used in straight line or small diagonal ring type welding rod, the back of the straight line welding rod, welding current can be appropriately increased.
(2) the use of other bevel butt cross weld, the gap is small, bottom welding can be used straight transport; gap is large, the bottom layer using reciprocating straight transport, the other layers when the multi-layer welding, can be used oblique ring transport, multi-layer multi-channel welding, should be used in a straight transport.
Introduction of Vertical Welding
3G is vertical welding.
Welding characteristics:
1. The molten pool metal and slag are easily separated due to the fall of self-weight.
2. When the molten pool temperature is too high, the molten pool metal is easy to flow down to form weld tumor, biting edge and slag and other defects, and the weld seam is not flat.
3. The root of the T-joint weld is easy to form a non-welded-through.
4. The degree of penetration is easy to grasp.
5. Welding productivity is lower than flat welding.
Welding points:
1. Maintain the correct angle of the welding rod;
2. Commonly used in the production of upward vertical welding, downward vertical welding to use a special electrode to ensure the quality of the weld. Upward vertical welding welding current is 10% to 15% smaller than the flat welding, and should use a smaller electrode diameter (<φ4mm)
3. Adopt short arc welding, shorten the distance of the molten drop transition to the molten pool.
4. Use the correct method of transportation.
(1) T-bevel butt (commonly used in thin plate) upward vertical welding, commonly used straight line, sawtooth and crescent-shaped transport method of welding, the maximum arc length is not less than 6mm.
(2) open other forms of bevel butt vertical welding, the first layer of weld is often used to break the weld, the swing is not large crescent-shaped, triangular transport welding. Subsequent layers can be crescent-shaped or sawtooth-shaped transport method.
(3) T-joint vertical welding, the electrode should be on both sides of the weld and the top corner of the appropriate residence time, the electrode swing should not be greater than the width of the weld, the operation of transporting the electrode and other bevel forms of vertical welding similar.
(4) When welding the cover layer, the shape of the weld surface is determined by the method of transporting the electrode. Weld surface requirements are slightly higher can choose crescent-shaped transport bar; surface flat can be used serrated transport bar (the middle concave shape and pause time).
Introduction of back welding
4G is back welding.
Welding characteristics:
1. The molten metal falls down due to gravity, and the shape and size of the molten pool should not be controlled.
2. It is difficult to transport the electrode, and the surface of the weldment should not be welded flat.
3. Prone to slagging, imperfections, weld lumps and poorly formed welds and other defects.
4. Melted weld metal splash spreading, easy to cause scalding accidents.
5. The efficiency of back welding is lower than that of other welding positions.
Welding points:
1. Butt weld back welding, when the thickness of the weldment ≤ 4mm, using Ⅰ type bevel, choose φ3.2mm electrode, welding current should be moderate; welding thickness ≥ 5mm, should be used multi-layer multi-channel welding.
2.T-joint weld back welding, when the welding foot is less than 8mm, should be used single layer welding, welding foot is greater than 8mm when using multi-layer multi-pass welding.
3. According to the specific situation, use the correct method of transportation:
(1) welding foot size is small, the use of linear or linear reciprocating type transport bar, single layer welding completed; welding foot size is large, can be used for multi-layer welding or multi-layer multi-channel welding transport bar, the first layer should be used for linear transport bar, the rest of the layers can be used to select the oblique triangular type or oblique ring type transport bar method.
(2) No matter what kind of transport method, each time to the molten pool excessive weld metal should not be too much.
The horizontal fixed port of the pipe is the 5G position.
Pipe 45 ° oblique welding mouth is 6G position.