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 division standard for 1G, 2G, 3G, 4G, 5G, and 6G, which is the division of the welding industry on the position of the weld. Let's find out today.
1. The position of the groove weld is divided into: 1G, 2G, 3G, 4G, 5G, and 6G, which respectively represent flat welding, horizontal welding, vertical welding, vertical welding, vertical welding, horizontal fixed welding of pipelines and fixed welding of pipelines at 45 degrees oblique.
2. Plate fillet welds are divided into: 1F, 2F, 3F and 4F, which are respectively ship-type welding, horizontal welding, vertical welding and vertical welding.
3. The fillet weld of the tube sheet or pipe is divided into: 1F, 2F, 2FR, 4F and 5F, which are respectively 45 degree rotary welding, horizontal welding (vertical pipe axis), horizontal (rotational) welding of pipe axis, and horizontal (fixed) welding of pipe axis upward welding.
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Introduction to flat welding
1G is flat welding.
Welding features:
1. Fusion welding metal mainly relies on its own weight to the weld pool.
2. The shape of the melt pool and the molten pool metal are easy to maintain and control.
3. Welding metal with the same thickness, the welding current of the flat welding position is larger than that of other welding positions, and the production efficiency is high.
4. The slag and the molten pool are prone to mixing, especially when welding the flat fillet weld, the slag is easy to advance and form slag inclusion.
It is not easy to distinguish between the slag of acid electrode and the molten pool; Alkaline electrodes are relatively clear;
5. Improper welding parameters and operation are easy to form defects such as welding nodules, undercuts and welding deformations.
6. When the backside of single-sided welding is freely formed, the first weld is prone to the image of uneven welding penetration procedure and poor backside molding.
Welding points:
1. According to the thickness of the plate, the welding rod with larger diameter and the welding current can be selected.
2. When welding, the welding rod and the weldment are at an angle of 60°~80°, and the separation of slag and liquid metal is controlled to prevent the slag from being ahead of time.
3. When the plate thickness is ≤6mm, the butt flat welding is generally open I. groove, and the front weld should be welded with a short arc of φ3.2~4 electrode, and the penetration depth can reach 2/3 of the plate thickness; Before the back cover, the roots can not be cleared (except for important structures), but the slag should be cleaned up, and the current can be larger.
4. If there is unclear mixing of slag and molten metal in butt flat welding, the arc can be elongated, the electrode can be tilted forward, and the action of pushing slag to the rear of the molten pool can be done to prevent slag inclusion.
5. When welding horizontal 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 multi-pass welding, attention should be paid to the number of welding passes and welding sequence, and each layer should not exceed 4~5mm.
7. For T-shaped, corner joints and lap joints, if the thickness of the two plates is different, the angle of the welding rod should be adjusted to deviate the arc to the side of the thick plate, so that the two plates are heated evenly.
8. Correct selection of transport methods
(1) When the welding thickness is ≤6mm, the I. groove butt is flat welding, and when double-sided welding is used, the front weld adopts a straight transport strip, which is slightly slower; The back weld is also made of straight strips, and the welding current is slightly larger and the speed is faster.
(2) The thickness of the plate is ≤6mm, and when opening other forms of grooves, multi-layer welding or multi-layer multi-pass welding can be used. For filler welding, short-arc welding with a larger diameter and a larger welding current can be used.
(3) When the size of the welding leg of the T-joint flat fillet welding is <6mm, single-layer welding can be selected, and the straight, oblique annular or zigzag transport strip method is used; When the size of the welding leg is large, it is advisable to use multi-layer welding or multi-layer multi-pass welding, the root welding adopts the linear strip method, and the filling layer can choose oblique zigzag and oblique annular strip.
(4) Multi-layer and multi-pass welding should generally be welded by linear transport strip method.
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Introduction to horizontal welding
2G is horizontal welding.
Welding features:
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 welds or non-penetrating defects on the lower side.
2. The molten metal is easy to separate from the slag, which is slightly similar to vertical welding.
Welding points:
1. The butt cross welding bevel is generally V-type or K-type, and the butt joint with a plate thickness of 3~4mm can be double-sided welding with I-type groove.
2. Choose small-diameter electrodes, 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, it is advisable to use multi-layer and multi-pass welding.
4. When multi-layer and multi-pass welding, special attention should be paid to controlling the overlap distance between weld beads. For each stack weld, the welding should be started at 1/3 of the previous weld to prevent unevenness.
5. According to the specific situation, keep the appropriate welding rod angle, and the welding speed should be slightly block and uniform.
6. Adopt the correct shipping method.
(1) When the I-type butt is cross-welded, it is better to use the reciprocating straight line transportation method for the front weld; Slightly thicker parts should be used straight or small oblique annular transport strips, and the back side should be used linear transport strips, and the welding current can be appropriately increased.
(2) Other groove butt horizontal welding is adopted, and when the gap is small, the bottom welding can be used to carry straight strips; When the gap is large, the bottom layer adopts the reciprocating linear transport strip, and when the other layers are multi-layer welding, the oblique annular transport strip can be used, and the linear transport strip should be used when multi-layer multi-pass welding.
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Introduction to vertical welding
3G is vertical welding.
Welding features:
1. The molten pool metal and the slag fall due to their own weight, and they are easy to separate.
2. When the temperature of the molten pool is too high, the metal in the molten pool is easy to flow down to form defects such as welding nodules, undercuts and slag inclusions, and the weld is uneven.
3. The root of the weld of the T-joint is easy to form unwelded penetration.
4. The degree of penetration is easy to master.
5. The welding productivity is lower than that of flat welding.
Welding points:
1. Maintain the correct electrode angle;
2. Commonly used in production is upward vertical welding, and downward vertical welding requires special welding rods to ensure the quality of the weld. The welding current is 10%~15% smaller than that of flat welding, and a smaller electrode diameter (<φ4mm) should be selected
3. Short-arc welding is used to shorten the distance from the molten droplet to the molten pool.
4. Adopt the correct shipping method.
(1) When T-groove butt (often used for thin plate) upward vertical welding, linear, zigzag and crescent-shaped transport strip methods are commonly used for welding, and the maximum arc length is not more than 6mm.
(2) When opening other forms of groove butt vertical welding, the first layer of weld is often welded by broken welding, crescent-shaped and triangular transport strips with small swing. The subsequent layers can be transported in a crescent or zigzag shape.
(3) When the T-joint is vertically welded, the electrode should have an appropriate residence time on both sides of the weld and the top angle, the swing amplitude of the electrode should not be greater than the width of the weld, and the operation of the transport rod is similar to that of vertical welding in other groove forms.
(4) When welding the cover layer, the surface shape of the weld is determined by the transport method. If the weld surface requirements are slightly higher, a crescent-shaped transport strip can be selected; If the surface is flat, a zigzag strip can be used (the middle concave shape is related to the pause time).
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Introduction to back welding
4G is back 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 bar, and the surface of the weldment should not be smooth.
3. It is prone to defects such as slag inclusion, lack of penetration, welding nodules and poor welding seam forming.
4. The melted weld metal spreads and spreads, which is easy to cause scalding accidents.
5. The efficiency of vertical welding is lower than that of welding in other positions.
Welding points:
1. Butt weld upward welding, when the thickness of the weldment is ≤ 4mm, the I. groove is used, the welding rod of φ3.2mm is selected, and the welding current should be moderate; when the welding thickness is ≥5mm, multi-layer multi-pass welding should be used.
2. T-joint weld upward welding, when the welding leg is less than 8mm, single-layer welding should be used, and multi-layer multi-pass welding should be used when the welding leg is greater than 8mm.
3. According to the specific situation, adopt the correct shipping method:
(1) When the size of the welding leg is small, the linear or linear reciprocating transport strip is adopted, and the single-layer welding is completed; When the size of the welding leg is larger, multi-layer welding or multi-layer multi-channel welding can be used, the first layer should be a linear transportation strip, and the remaining layers can choose the oblique triangle type or oblique ring transportation strip method.
(2) No matter which method of transporting the strip is adopted, the excessive weld metal to the molten pool should not be too much each time.
The horizontal fixed port of the pipeline is the 5G position.
The 45° diagonal weld of the pipe is the 6G position.