Mobile phones have become very common, and everyone basically knows what 1G, 2G, 3G, 4G, and 5G networks mean. In fact, in the machinery industry, there is also a classification standard for 1G, 2G, 3G, 4G, 5G, and 6G. This standard is the classification of welding seam positions in the welding industry. Let's find out today.
1. The positions of groove welds are divided into: 1G, 2G, 3G, 4G, 5G and 6G, which respectively represent flat welding, horizontal welding, vertical welding, overhead welding, horizontal fixed welding of pipelines and fixed welding of pipelines at an angle of 45 degrees. .
2. Plate fillet welds are divided into: 1F, 2F, 3F and 4F, which are ship welding, horizontal welding, vertical welding and overhead welding respectively.
3. Tube sheet or pipe fillet welds are divided into: 1F, 2F, 2FR, 4F and 5F, which are 45-degree rotation welding, horizontal welding (pipe axis vertical), pipe axis horizontal (rotation) welding, and overhead welding with the pipe axis horizontal ( Fixed) welding.
Introduction to flat welding
1G is flat welding.
Welding features:
1. The molten welding metal mainly relies on its own weight to transfer to the molten pool.
2. The shape of the molten pool and the metal of the molten pool are easy to maintain and control.
3. When welding metal of the same plate thickness, the welding current in the flat welding position is larger than that in other welding positions, and the production efficiency is high.
4. The molten slag and the molten pool are prone to mixing, especially when welding flat-angle welds, the molten slag is prone to advance and form slag inclusions.
The slag and molten pool of acidic welding rods are difficult to distinguish; the two are relatively clear in alkaline welding rods;
5. Improper welding parameters and operations can easily cause defects such as welding nodules, undercuts and welding deformations.
6. When the back side is free-formed by single-sided welding, the first weld seam is prone to uneven penetration and poor back-side forming.
Welding points:
1. According to the thickness of the plate, a larger diameter electrode and a larger welding current can be used for welding.
2. During welding, the welding rod and the weldment should form an angle of 60° to 80° to control the separation of slag and liquid metal to prevent the slag from leading.
3. When the plate thickness is ≤6mm, a Type I groove is generally used for butt welding. The front weld should be short-arc welded with a φ3.2~4 electrode, and the penetration depth can reach 2/3 of the plate thickness; before back sealing, It is not necessary to clear the roots (except for important structures), but the slag must be cleaned up and the current can be larger.
4. If there is unclear mixing of slag and metal in the molten pool during butt welding, the arc can be lengthened, the electrode can be tilted forward, and the slag can be pushed to the back of the molten pool to prevent slag inclusions.
5. When welding horizontally inclined welds, uphill welding should be used to prevent slag inclusion and molten pool from moving forward and avoid slag inclusion.
6. When using multi-layer and multi-pass welding, attention should be paid to selecting the number of welding passes and the welding sequence. Each layer should not exceed 4~5mm.
7. For T-shaped, corner and lap joints, if the thickness of the two plates is different, the angle of the welding rod should be adjusted to deflect the arc to the side of the thick plate so that the two plates are heated evenly.
8. Choose the correct shipping method
(1) When the welding thickness is ≤6mm, Type I groove butt welding is used for flat welding. When double-sided welding is used, the front weld adopts a linear movement, which is slightly slower; the back weld also adopts a linear movement, and the welding current is slightly larger. , faster.
(2) When the plate thickness is ≤6mm, when making other forms of grooves, multi-layer welding or multi-layer multi-pass welding can be used. The first layer of bottom welding should use a small current electrode, a small standard current, a linear rod or a sawtooth electrode. Shape transport bar welding. When filling layer welding, short arc welding with larger diameter electrodes and larger welding current can be used.
(3) When the welding leg size of T-shaped joint flat fillet welding is less than 6mm, single-layer welding can be used, and linear, oblique ring or zigzag strip transportation methods are used; when the welding leg size is larger, multi-layer welding or multi-layer welding should be used For multi-pass welding, the bottom welding adopts linear strip transport method, and the filling layer can use oblique zigzag or oblique ring transport method.
(4) For multi-layer and multi-pass welding, it is generally advisable to use linear welding method.
Introduction to horizontal welding
2G is horizontal soldering.
Welding features:
1. The molten metal tends to fall on the groove due to its own weight, causing undercut defects on the upper side and teardrop-shaped welding nodules or incomplete welding defects on the lower side.
2. Molten metal and slag are easily separated, slightly like vertical welding.
Welding points:
1. The groove for butt transverse welding is generally V-shaped or K-shaped. Butt joints with a plate thickness of 3~4mm can be welded with type I groove on both sides.
2. Use a small-diameter welding rod, the welding current is smaller than that of flat welding, and the short arc operation can better control the flow of molten metal.
3. When welding thick plates, in addition to the bottom weld, multi-layer and multi-pass welding should be used.
4. When welding multiple layers and multiple passes, special attention should be paid to controlling the overlap distance between weld passes. For each pass of stack welding, welding should be started at 1/3 of the previous weld to prevent unevenness.
5. According to the specific situation, maintain an appropriate welding rod angle, and the welding speed should be slightly blocky and uniform.
6. Use the correct shipping method.
(1) When type I butt welding is carried out horizontally, it is better to use the reciprocating straight-line transport method for the front weld; for slightly thicker parts, straight-line or small-incline circular transport is recommended, and for the back, straight-line transport is used, and the welding current can be appropriately increased.
(2) Other groove butt welding is used for horizontal welding. When the gap is small, the backing welding can use a straight line; when the gap is large, the bottom layer can use a reciprocating linear welding. When the other layers are multi-layer welded, the oblique welding can be used. Circular transport, linear transport should be used for multi-layer and multi-pass welding.
Introduction to vertical welding
3G is vertical welding.
Welding features:
1. The molten pool metal and slag fall due to their own weight and are easily separated.
2. When the temperature of the molten pool is too high, the metal in the molten pool will easily flow down to form defects such as weld nodules, undercuts and slag inclusions, and the weld will be uneven.
3. The root of the T-shaped joint weld is prone to incomplete penetration.
4. The degree of penetration is easy to control.
5. Welding productivity is lower than flat welding.
Welding points:
1. Maintain the correct angle of the welding rod;
2. Upward vertical welding is commonly used in production. Special welding rods are required for downward vertical welding to ensure the quality of the weld. When welding upward, the welding current is 10% to 15% smaller than when welding flat, and a smaller electrode diameter (<φ4mm) should be selected.
3. Use short arc welding to shorten the distance between the molten droplet and the molten pool.
4. Use the correct shipping method.
(1) When T-shaped groove butt joints (commonly used for thin plates) are welded vertically upward, linear, zigzag and crescent-shaped strip methods are commonly used, and the maximum arc length is not greater than 6mm.
(2) When other forms of groove butt welding are used for vertical welding, the first layer of welding seam is often welded with crescent-shaped or triangular strips with small swing and broken welding. Subsequent layers can be transported in a crescent or zigzag shape.
(3) When vertical welding of T-shaped joints, the welding rod should have an appropriate residence time on both sides of the weld and at the top corner. The swing amplitude of the welding rod should not be greater than the width of the weld. The rod transport operation is similar to that of other bevel forms of vertical welding.
(4) When welding the cover layer, the surface shape of the weld depends on the strip transport method. If the weld surface requirements are slightly higher, crescent-shaped strips can be used; if the surface is flat, zigzag-shaped strips can be used (the concave shape in the middle is related to the dwell time).
Introduction to overhead welding
4G is overhead welding.
Welding features:
1. The molten metal falls due to gravity, and the shape and size of the molten pool should not be controlled.
2. It is difficult to transport the rod, and the surface of the weldment should not be smooth.
3. Defects such as slag inclusion, incomplete welding penetration, welding nodules and poor welding seam formation are prone to occur.
4. The melted weld metal spatters and spreads, easily causing burn accidents.
5. Overhead welding is less efficient than other positions.
Welding points:
1. For overhead welding of butt welds, when the thickness of the weldment is ≤ 4mm, type I groove should be used, and a φ3.2mm electrode should be used. The welding current should be moderate; when the welding thickness is ≥ 5mm, multi-layer and multi-pass welding should be used.
2. T-type joint welding seam is upward welded. When the welding leg is less than 8mm, single-layer welding should be used. When the welding leg is larger than 8mm, multi-layer and multi-pass welding should be used.
3. According to the specific situation, adopt the correct shipping method:
(1) When the size of the welding leg is small, linear or linear reciprocating strip welding is used, and single-layer welding is completed; when the size of the welding leg is large, multi-layer welding or multi-layer multi-pass welding strip can be used, and the first layer should be The strips are transported in a straight line, and the remaining layers can be transported in an oblique triangle or an oblique ring type.
(2) No matter which method of transporting the rod is adopted, the amount of weld metal that passes into the molten pool at each time should not be too much.
The horizontal fixed opening of the pipeline is the 5G location.
The 45° oblique welding joint of the pipeline is the 6G position.
