Mobile phones have become ubiquitous. Most people are familiar with the terms 1G, 2G, 3G, 4G, and 5G networks. However, in the welding industry, there is also a classification system for weld positions, referred to as 1G, 2G, 3G, 4G, 5G, and 6G.
Let’s explore this topic further.
Welding Position Code
The positions of groove welds are classified as 1G, 2G, 3G, 4G, 5G, and 6G, respectively representing flat welding, horizontal welding, vertical welding, overhead welding, horizontal fixed welding of pipelines, and 45° inclined fixed welding of pipelines.
Butt welding of plate:
- (1) Flat position, denoted as 1G;
- (2) Horizontal position, denoted as 2G;
- (3) Vertical position, denoted as 3G;
- (4) Overhead position, denoted as 4G.
Butt welding of pipe:
- (1) Horizontal rotation, denoted as 1G;
- (2) Vertical fixed position, denoted as 2G;
- (3) Horizontal fixed position, denoted as 5G, 5GX;
- (4) 45-degree fixed position, denoted as 6G, 6GX.
Butt joint welding between pipe and plate:
- (1) Horizontal rotation, denoted as 2FRC;
- (2) Vertical fixed position, flat welding, denoted as 2FG;
- (3) Vertical fixed position, overhead welding, denoted as 4FG;
- (4) Horizontal fixed position, denoted as 5FG;
- (5) 45-degree fixed position, denoted as 6FG.
Plate fillet welding:
Plate fillet welds are classified as 1F, 2F, 3F, and 4F, representing ship-type welding, horizontal welding, vertical welding, and overhead welding, respectively.
Tubesheet or tube fillet welds are classified as 1F, 2F, 2FR, 4F, and 5F, representing 45-degree rotary welding, transverse welding (with the tube axis vertical), horizontal rotary welding of the tube axis, and horizontal fixed overhead welding of the tube axis, respectively.
- (1) Flat position, denoted as 1S;
- (2) Horizontal position, denoted as 2S;
- (3) Overhead position, denoted as 4S.
- According to AWS, flat position is denoted as F, horizontal position is denoted as H, vertical position is denoted as V, and overhead position is denoted as OH.
Flat welding (1G)
1G is flat welding
1G Welding characteristics:
Fusion welding of metal primarily relies on its own weight to flow into the molten pool.
The shape and composition of the molten pool are simple to maintain and control.
When welding metal with the same plate thickness, the welding current required for flat welding is higher compared to other welding positions, leading to higher production efficiency.
However, slag and the molten pool are prone to mixing, particularly when welding flat fillet welds, causing the slag to easily advance and form slag inclusions.
Acid electrodes can make it difficult to distinguish between the slag and molten pool, while alkaline electrodes provide clarity.
Incorrect welding parameters and techniques can result in defects such as bead formation, undercut, and welding deformation.
In single-side welding, if the back is free-forming, the first weld may exhibit issues such as uneven penetration or poor back formation.
Key points of 1G welding:
According to the thickness of the plate, a welding rod with a larger diameter and a higher welding current can be selected.
When welding, the electrode and the weldment should form an angle of 60-80°, and the separation of slag and liquid metal should be controlled to avoid slag leading.
For plate thicknesses of ≤6mm, a Type I groove should generally be used for butt flat welding, and a 3.2-4mm diameter electrode with a short arc welding technique should be used for the front weld, with penetration reaching 2/3 of the plate thickness.
Before back sealing, the root may not be cleaned, except for in important structures, but the slag should be cleaned, and the current can be higher.
If there is confusion between the slag and molten pool metal in butt flat welding, extend the arc, tilt the electrode forward, and push the slag behind the molten pool to prevent slag inclusion.
For horizontal and inclined welding, uphill welding should be used to avoid slag inclusion and to prevent the molten pool from moving forward.
When multi-layer, multi-pass welding is used, consider the number of welding passes and the welding sequence, with each layer not exceeding 4-5mm.
For T-joints, fillet, and lap flat angle welded joints, if the thickness of the two plates is different, the electrode angle should be adjusted to direct the arc to one side of the thicker plate to ensure even heating of the two plates.
Correct selection of strip transportation method
(1) For welding thickness less than or equal to 6mm, I-groove butt flat welding is used.
Double-sided welding should employ linear strip transportation for the front weld, at a slightly slow pace.
The back weld should also use linear strip transportation, with a slightly larger welding current and faster speed.
(2) For plate thickness less than or equal to 6mm, multi-layer welding or multi-layer multi-pass welding can be used when other groove forms are utilized.
The first layer of backing welding should use low current electrode, low standard current, and linear or serrated electrode welding.
When welding the filler layer, electrodes with larger diameter and short arc welding with higher welding current can be selected.
(3) For T-joint flat fillet welding with leg size less than 6mm, single-layer welding can be chosen and linear, oblique ring or sawtooth strip transportation methods can be used.
For larger welding leg size, multi-layer welding or multi-layer multi-pass welding should be used.
The linear strip transportation method is employed for backing welding, and inclined sawtooth or inclined ring strip transportation can be chosen for the filling layer.
(4) Multi-layer and multi-pass welding should generally use the linear strip welding method.
Horizontal welding (2G)
2G is horizontal welding
2G Welding characteristics:
The molten metal can easily drop into the groove due to its own weight, leading to undercut defects on the upper side and tear drop weld beading or incomplete penetration defects on the lower side.
The separation of molten metal and slag is relatively easy, similar to vertical welding.
Key points of 2G welding:
The V-type or K-type groove is generally used for butt horizontal welding, and for butt joints with a plate thickness of 3 to 4mm, both sides can be welded using type I groove.
A small diameter electrode should be selected and the welding current should be smaller than that used for flat welding. Short arc operation can better control the flow of molten metal.
For welding thick plates, multi-layer and multi-pass welding should be adopted in addition to backing welds.
When using multi-layer and multi-pass welding, special attention should be paid to controlling the overlapping distance between welding passes. Each overlap welding should start at 1/3 of the previous weld to prevent unevenness.
The appropriate electrode angle should be maintained according to the specific situation and the welding speed should be slightly blocked and uniform.
The correct strip transportation method should be used:
(1) For type I butt horizontal welding, the front weld is best done using the reciprocating linear strip transportation method.
For thicker parts, linear or small inclined annular strip should be used and linear strip should be used on the back. The welding current can be increased appropriately.
(2) For other groove butt horizontal welding, if the gap is small, straight-line strip transportation can be used for backing welding.
If the gap is large, the backing layer should use reciprocating linear strip transportation and other layers can use inclined ring strip transportation during multi-layer welding. Linear strip transportation should be used during multi-layer multi-pass welding.
Vertical welding (3G)
3G is vertical welding
3G Welding characteristics:
The molten metal and slag separate easily due to gravity, which can result in defects such as weld beading, undercut, and slag inclusion.
The high temperature of the molten pool makes the metal flow downwards, leading to uneven welding.
Incomplete penetration can occur at the root of T-joint welds and it is easier to control the degree of penetration.
However, the productivity of welding is lower compared to flat welding.
Key points of 3G welding:
Maintain the correct electrode angle;
Vertical upward welding is commonly used in production and a specialized welding rod should be used for vertical downward welding to ensure quality.
The welding current for vertical upward welding is 10 to 15% less than that for flat welding, and a smaller electrode diameter (less than 4mm) should be selected.
Short-arc welding is used to reduce the distance from droplet transfer to the molten pool.
Adopt the correct strip transportation method.
(1) When vertically welding upward on a T-groove butt joint (commonly used for thin plates), the linear, serrated, and crescent strip transportation methods are commonly used. The maximum arc length should not exceed 6mm.
(2) For other forms of groove butt vertical welding, the first layer of welding often employs broken welding, crescent welding with a small swing, and triangular strip welding. Subsequent layers can be transported using a crescent or sawtooth shape.
(3) During vertical welding of T-joints, the electrode should have an appropriate dwelling time on both sides and top corners of the weld, and the swing amplitude of the electrode should not be larger than the width of the weld. The electrode transportation operation is similar to that of vertical welding of other groove forms.
(4) When welding the cover layer, the shape of the weld surface will depend on the strip transportation method. A crescent-shaped strip can be used if a slightly higher surface quality is required, while a sawtooth strip transportation method can be used for a flat surface (the middle concave shape is related to the pause time).
Overhead welding (4G)
4G is overhead welding
4G Welding characteristics:
Molten metal falls due to gravity, and the control of the shape and size of the molten pool is challenging.
The transportation of the strip is difficult, and a flat surface on the weldment is not easily achievable.
Defects such as slag inclusion, incomplete penetration, weld beading, and poor weld formation are commonly seen. The splashing and diffusion of molten weld metal can cause burn accidents.
Overhead welding is less efficient compared to other welding positions.
Key points of 4G welding:
For butt weld overhead welding, when the thickness of the weldment is ≤ 4mm, type I groove should be used, a 3.2mm electrode should be selected, and the welding current should be moderate.
When the weld thickness is ≥ 5mm, multi-layer and multi-pass welding should be used.
For overhead welding of T-joint welds, single-layer welding should be used when the weld leg is less than 8mm and multi-layer and multi-pass welding should be used when the weld leg is greater than 8mm.
The correct strip transportation method should be selected based on the specific situation:
(1) When the size of the welding leg is small, linear or linear reciprocating strip transportation should be used, and single-layer welding should be completed.
When the size of the welding leg is large, multi-layer welding or multi-layer and multi-pass welding strip transportation can be used.
The first layer should be transported using linear strip transportation, and subsequent layers can use inclined triangular or inclined ring strip transportation.
(2) No matter which strip transportation method is used, the amount of weld metal added to the molten pool at one time should not be excessive.
Horizontal fixing port of the pipeline (5G)
The horizontal fixing port of the pipeline is 5g position
45 °oblique welded junction of the pipe (6G)
The 45 °oblique welded junction of the pipe is the 6G position
Welding Methods and Their Codes
Each welding method can be performed using manual welding, mechanized welding, or automatic welding, with their codes as shown in the table below.
|Plasma Arc Welding||GMAW|
|Submerged Arc Welding||SAW|
|Plasma Arc Welding||PAW|
|Gas Tungsten Arc Welding in the vertical position||EGW|
|Stud Arc Welding||SW|
Test Piece Forms, Positions, and Their Codes
The forms, positions, and their codes of test pieces are shown in the table below. The test piece position basically determines the welding position.
Table 1. Test Piece Forms, Positions and Codes.
|Test Piece Form||Test Piece Position||Code|
|Sheet metal butt-welding test piece||Flat welding test piece||1G|
|Horizontal welding test piece||2G|
|Vertical welding test piece||3G|
|Overhead welding test piece||4G|
|Pipe butt-welding test piece||Horizontal rotation welding test piece||1G|
|Vertical fixed welding test piece||2G|
|Horizontal fixed welding test piece||Upward welding||5G|
|45°fixed welding test piece||Upward welding||6G|
|Pipe-to-plate corner joint test piece||Horizontal rotation welding test piece||2FRG|
|Vertical fixed flat welding test piece||2FG|
|Vertical fixed overhead welding test piece||4FG|
|Horizontal fixed welding test piece||5FG|
|45°fixed welding test piece||6FG|
|Sheet metal corner welding test piece||Flat welding test piece||1F|
|Horizontal welding test piece||2F|
|Vertical welding test piece||3F|
|Overhead welding test piece||4F|
|Pipe corner welding test piece |
(including pipe-to-plate corner welding test piece and pipe-to-pipe corner welding test piece).
|45°rotation welding test piece||1F|
|Vertical fixed horizontal welding test piece||2F|
|Horizontal rotation welding test piece||2FR|
|Vertical fixed overhead welding test piece||4F|
|Horizontal fixed welding test piece||5F|
|Threaded stud welding test piece||Flat welding test piece||1S|
|Horizontal welding test piece||2S|
|Overhead welding test piece||4S|
Test Pieces With and Without Backing Pads
The sheet metal butt-welding test piece, pipe butt-welding test piece, and pipe-to-plate corner joint test piece can be divided into two types: with and without backing pads.
For double-sided fillet welds, groove welds, and pipe-to-plate corner joints where full penetration is not required, they are considered as with backing pads.
However, when single-sided welding is used with inert gas shielded welding, it cannot be considered as with backing pads.
(1) Sheet metal butt-welding test piece (when there is no groove, it is a fillet welding test piece).
(2) Sheet metal corner welding test piece.
Table 2. Applicable Welding Positions for Test Pieces
|Test Piece||Applicable Welding Range|
|Butt Welding Position||Corner Welding Position||Pipe-to-plate corner joint welding position|
|Form||Code||sheet metal and pipes with an outer diameter greater than 600mm||pipes with an outer diameter smaller than or equal to 600mm|
|Sheet metal butt-welding (Note A-2)||1G||Flat||Flat||Flat||/|
|2G||Flat and horizontal||Flat and horizontal||Flat and horizontal||/|
|3G||Flat and vertical||Flat||Flat, horizontal and vertical||/|
|4G||Flat and overhead||Flat||Flat, horizontal and overhead||/|
|Pipe butt-welding test piece||1G||Flat||Flat||Flat||/|
|2G||Flat and horizontal||Flat and horizontal||Flat and horizontal||/|
|5G||Flat, vertical and overhead||Flat, vertical and overhead||Flat, vertical and overhead||/|
|5GX||Flat, vertical downward, and overhead||Flat, vertical downward, and overhead||Flat, vertical downward and overhead||/|
|6G||Flat, horizontal, vertical, and overhead||Flat, horizontal, vertical, and overhead||Flat, horizontal, vertical and overhead||/|
|6GX||Flat, vertical downward, horizontal, and overhead.||Flat, vertical downward, horizontal, and overhead.||Flat, vertical downward, horizontal and overhead||/|
|Pipe-to-plate corner joint||2FG||/||/||Flat and horizontal||2FG|
|2FRG||/||/||Flat and horizontal||2FRG|
|4FG||/||/||Flat, horizontal and overhead||4FG|
|5FG||/||/||Flat, horizontal, vertical and overhead||5FG|
|6FG||/||/||Flat, horizontal, vertical and overhead||All positions|
|Sheet metal corner welding||1F||/||/||Flat||/|
|2F||/||/||Flat and horizontal||/|
|3F||/||/||Flat, horizontal and vertical||/|
|4F||/||/||Flat, horizontal and overhead||/|
|Pipe corner welding||1F||/||/||Flat||/|
|2F||/||/||Flat and horizontal||/|
|2FR||/||/||Flat and horizontal||/|
|4F||/||/||Flat, horizontal and overhead||/|
|5F||/||/||Flat, vertical, horizontal and overhead.||/|