Mobile phones are already 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 weld positions in the welding industry. Let's learn about it today.
1. The positions of groove welds are divided into: 1G, 2G, 3G, 4G, 5G, and 6G, which represent flat welding, horizontal welding, vertical welding, overhead welding, horizontal fixed welding of pipes, and fixed welding of pipes at an angle of 45 degrees.
2. Plate fillet welds are divided into: 1F, 2F, 3F, and 4F, which are ship-shaped welding, horizontal welding, vertical welding, and overhead welding.
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3. Tube sheet or tube fillet welds are divided into: 1F, 2F, 2FR, 4F, and 5F, which are 45-degree rotation welding, horizontal welding (vertical to the pipe axis), horizontal (rotation) welding of the pipe axis, and horizontal (fixed) welding of the overhead welding pipe axis.
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ping
ping
han
welding
Introduction to flat welding
1G is flat welding.
Welding characteristics:
1. The molten metal mainly relies on its own weight to transfer to the molten pool.
2. The shape of the molten pool and the molten pool metal are easy to maintain and control.
3. When welding metals of the same plate thickness, the welding current at the flat welding position is larger than that at other welding positions, and the production efficiency is high.
4. The slag and the molten pool are prone to mixing, especially when welding flat angle welds, the slag is easy to advance and form slag inclusions.
It is difficult to distinguish the slag and the molten pool of acidic electrodes; the two are relatively clear for alkaline electrodes;
5. When the welding parameters and operations are not appropriate, defects such as weld nodules, undercuts and welding deformations are easy to form.
6. When the back side of the single-sided welding is freely formed, the first weld is prone to uneven penetration and poor back forming.
Key points of welding:
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 electrode and the weldment should be at an angle of 60° to 80°, and the slag and liquid metal should be separated to prevent the slag from advancing.
3. When the plate thickness is ≤6mm, the butt welding generally opens a type I groove, and the front weld should be welded with a short arc welding electrode of φ3.2~4, and the penetration depth can reach 2/3 of the plate thickness; before the back is sealed, the root can be removed (except for important structures), but the slag must be cleaned up and the current can be larger.
4. If there is a phenomenon of unclear mixing of slag and molten pool metal in 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 inclusion.
5. When welding horizontally inclined welds, it is advisable to use uphill welding 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 welds and the welding sequence, and each layer should not exceed 4~5mm.
7. For T-type, corner and lap joints, if the thickness of the two plates is different, the electrode angle should be adjusted to bias the arc toward the thicker plate so that the two plates are heated evenly.
8. Correct selection of electrode feeding method
(1) When the weld thickness is ≤6mm, for type I groove butt welding, when double-sided welding is used, the front weld adopts linear electrode feeding, which is slightly slower; the back weld also adopts linear electrode feeding, with a slightly larger welding current and faster speed.
(2) When the plate thickness is ≤6mm and other forms of grooves are opened, multi-layer welding or multi-layer multi-pass welding can be used. The first layer of base welding should use a small current electrode, a small standard current, linear electrode feeding or a zigzag electrode feeding. When welding the filler layer, a larger diameter electrode and a larger welding current short arc welding can be used.
(3) When the leg size of the T-joint flat fillet weld is less than 6mm, single-layer welding can be selected, using a straight-line, oblique ring or sawtooth-shaped welding method; when the leg size is larger, multi-layer welding or multi-layer multi-pass welding is suitable, and the base welding adopts a straight-line welding method, and the filling layer can choose an oblique sawtooth or oblique ring-shaped welding method.
(4) Multi-layer multi-pass welding is generally suitable for welding with a straight-line welding method.
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Horizontal
han
Welding
Introduction to horizontal welding
2G is horizontal welding.
Welding characteristics:
1. The molten metal is easy to fall on the groove due to its own weight, resulting in undercut defects on the upper side and teardrop-shaped weld nodules or incomplete penetration defects on the lower side.
2. The molten metal and slag are easy to separate, which is slightly similar to vertical welding.
Welding points:
1. The groove for butt horizontal welding is generally V-shaped or K-shaped. Butt joints with a plate thickness of 3~4mm can use type I groove double-sided welding.
2. Use small diameter electrodes, the welding current should be smaller than that of flat welding, and short arc operation can better control the flow of molten metal.
3. When welding thick plates, except for the base weld, multi-layer and multi-pass welding should be used.
4. When welding multi-layer and multi-pass, special attention should be paid to controlling the overlapping distance between welds. Each overlap welding should start at 1/3 of the previous weld to prevent unevenness.
5. According to the specific situation, maintain an appropriate electrode angle, and the welding speed should be slightly faster and uniform.
6. Use the correct electrode feeding method.
(1) When welding type I butt joints horizontally, it is better to use the reciprocating linear electrode feeding method for the front weld; for slightly thicker parts, it is better to use linear or slightly oblique circular electrode feeding, and linear electrode feeding on the back, and the welding current can be appropriately increased.
(2) When other grooves are used for butt welding, when the gap is small, the base welding can be carried out in a straight line; when the gap is large, the base layer adopts a reciprocating straight line type of welding, and when the other layers are welded in multiple layers, the inclined ring type of welding can be adopted. When welding in multiple layers and multiple passes, the straight line type of welding should be adopted.
li
Vertical
han
Welding
Introduction to vertical welding
3G is vertical welding.
Welding characteristics:
1. The molten pool metal and slag fall due to their own weight and are easy to separate.
2. When the molten pool temperature is too high, the molten pool metal is easy to flow down to form defects such as weld nodules, undercuts and slag inclusions, and the weld is uneven.
3. The root of the T-joint weld is prone to incomplete penetration.
4. The degree of penetration is easy to control.
5. The welding productivity is lower than that of flat welding.
Key points of welding:
1. Maintain the correct electrode angle;
2. Vertical welding upwards is commonly used in production, and special electrodes are required for vertical welding downwards to ensure the quality of the weld. When welding vertically upward, the welding current is 10% to 15% lower than that of flat welding, and a smaller electrode diameter (<φ4mm) should be used.
3. Use short arc welding to shorten the distance from the molten droplet to the molten pool.
4. Use the correct electrode movement method.
(1) When welding T-shaped groove butt joints (commonly used for thin plates) vertically upward, straight, zigzag and crescent-shaped electrode movement methods are often used, and the maximum arc length is not more than 6mm.
(2) When welding other forms of groove butt joints vertically, the first layer of welds is often welded with crescent-shaped or triangular-shaped electrode movement with a short welding and small swing. The subsequent layers can use crescent-shaped or zigzag-shaped electrode movement methods.
(3) When welding T-shaped joints vertically, the electrode should have an appropriate stay time on both sides and the top corner of the weld, and the electrode swing amplitude should not be greater than the weld width. The electrode movement operation is similar to vertical welding with other groove forms.
(4) When welding the cover layer, the surface shape of the weld is determined by the electrode movement method. For welds with slightly higher surface requirements, crescent-shaped rod feeding can be used; for welds with smooth surface, sawtooth-shaped rod feeding can be used (the concave shape in the middle is related to the pause time).
yang
Upward
han
Welding
Introduction to overhead welding
4G is overhead welding.
Welding characteristics:
1. The molten metal falls due to gravity, and the shape and size of the molten pool are not easy to control.
2. It is difficult to feed the rod, and the surface of the weld is not easy to be welded flat.
3. Defects such as slag inclusion, incomplete penetration, weld nodules and poor weld formation are prone to occur.
4. The molten weld metal splashes and spreads, which can easily cause scalding accidents.
5. Overhead welding is less efficient than other positions.
Key points of welding:
1. For overhead welding of butt welds, when the thickness of the weldment is ≤4mm, use type I groove, use φ3.2mm welding rod, and the welding current should be moderate; when the welding thickness is ≥5mm, multi-layer and multi-pass welding should be used.
2. For T-joint welds, when the weld leg is less than 8mm, single-layer welding should be used; when the weld leg is larger than 8mm, multi-layer and multi-pass welding should be used.
3. Use the correct wire feeding method according to the specific situation:
(1) When the weld leg size is small, use linear or linear reciprocating wire feeding, and complete the single-layer welding; when the weld leg size is large, multi-layer welding or multi-layer and multi-pass welding wire feeding can be used. The first layer should use linear wire feeding, and the remaining layers can use oblique triangle or oblique ring wire feeding methods.
(2) Regardless of which wire feeding method is used, the amount of weld metal transferred to the molten pool each time should not be too much.
The horizontal fixed port of the pipeline is the 5G position.
The 45° oblique welding port of the pipeline is the 6G position.
