Double-wire submerged arc welding process

Abstract

The invention relates to the technical field of welding processes, and provides a double-wire submerged-arc welding process, which adopts a double-wire submerged-arc welding mode to realize welding, has better applicability to weldments with larger thicknesses, improves the welding efficiency while ensuring the welding quality, and also has better practicability, and comprises the following steps: S1, preparation before welding: preparing welding wires; s2, welding parameter setting: front wires and rear wires are arranged in a tandem manner, the front wires are in direct current reverse connection, the rear wires are powered by alternating current so as to reduce mutual influence and magnetic blow between the front wires and electric arcs, the specification of the front wires is # imgabs0 #, the front wires are perpendicular to the weldment, the distance between the end parts of the front wires and the weldment is 3mm-5mm, the extension length of the front wires is 32mm-40mm, and the diameter of the front wires is 10mm-10mm; the specification of the rear wires is that # imgabs 1 # rear wires incline towards the front wires by 12-15 degrees, the distance between the ends of the rear wires and the weldment is 4-6 mm, the extension length of the rear wires is the same as that of the front wires, and the distance between the front wires and the rear wires is 20-35 mm, S3, arc striking and welding, and S4, welding post-treatment: weld joint cleaning and weld joint inspection.

Description

Technical Field

[0001] The invention relates to the technical field of welding technology, and in particular to a double-wire submerged arc welding technology. Background Art

[0002] As we all know, double-wire submerged arc welding uses two welding wires, the front wire uses a DC power supply, and the rear wire uses an AC power supply. During the welding process, the two welding wires are fed into the weld at the same time, and the heat of the arc melts the welding wires and the base material to form a weld.

[0003] The existing submerged arc welding steps generally include the following steps: first, the position to be welded on the welded part is cleaned, then the welded part is fixed, and then the welding parameters of the welding equipment are adjusted. After the adjustment is completed, welding is carried out. When welding, for thicker welded parts, it is usually necessary to perform groove treatment on the welding position, and in order to ensure the welding quality, the weld is mostly achieved by multiple welding in succession. The welding efficiency needs to be further improved, and the welding quality also needs to be further strengthened. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a double-wire submerged arc welding process, which adopts double-wire submerged arc welding to achieve welding. It has good applicability for weldments with larger thickness, ensures welding quality, and improves welding efficiency, and has good practicality.

[0005] To achieve the above object, the present invention provides the following technical solution: a double-wire submerged arc welding process, characterized in that it comprises the following steps:

[0006] S1: Preparation before welding:

[0007] Welding wire preparation: select appropriate welding wire according to welding requirements and ensure its quality meets the standards;

[0008] Flux preparation: the flux should be kept dry and avoid moisture;

[0009] Equipment inspection: Check whether the double-wire submerged arc welding equipment is operating normally and ensure that the welding equipment is well grounded to ensure safe operation;

[0010] Weldment preparation: clean the weldment and remove impurities such as oil, rust, scale, etc. on the surface to ensure welding quality. Perform groove processing according to welding requirements to ensure that the groove size meets the standards;

[0011] S2: Welding parameter settings:

[0012] The front wire and the rear wire are arranged in a longitudinal column, the front wire is reversely connected to DC, and the rear wire is powered by AC to reduce the mutual influence and magnetic blow between the arc and the front wire. The specifications of the front wire are The front wire is perpendicular to the weldment, the end of the front wire is 3mm-5mm away from the weldment, the extension length of the front wire is 32mm-40mm, and the rear wire specification is The rear wire is inclined 12°-15° to the front wire, the end of the rear wire is 4mm-6mm away from the weldment, the extended length of the rear wire is the same as that of the front wire, and the distance between the front and rear wires is 20mm-35mm;

[0013] S3: Arc starting and welding

[0014] Arc striking: Install the arc striking and extinguishing plate. The material, thickness and groove size of the arc striking and extinguishing plate should be the same as the base material of the weldment as much as possible. After the arc striking and extinguishing plate is grooved, the carbon planing metal slag should be cleaned before welding. Pay attention to safety when striking the arc to avoid arc burning the operator;

[0015] Welding process: the front wire and the rear wire are fed into the weld at the same time, and the heat of the arc melts the front wire, the rear wire and the base material to form a weld. The operator should pay close attention to the arc stability, weld formation and molten pool during the welding process, and adjust the welding parameters in time. The coverage height of the flux should be maintained during the welding process to ensure the protection effect of the weld;

[0016] S4: Post-welding treatment

[0017] Weld cleaning: After welding, the welding slag and spatter on the weld surface should be cleaned in time to ensure the appearance quality of the weld;

[0018] Weld inspection: Perform visual inspection on the weld to check whether the shape, size and surface quality of the weld meet the standards.

[0019] Preferably, in step S3, since the rear wire is arced in the molten pool of the front wire, the molten pool must be established after the front wire is arced before the rear wire can be arced, so the end of the rear wire must be 3mm±0.5mm higher than the front wire.

[0020] Preferably, in step S3, the size of the arc striking and extinguishing plate is not less than 80mm x 150mm, and the length of the arc striking and extinguishing weld is in the range of 80mm-100mm.

[0021] Preferably, the shape and size of the weld in step S4: the butt weld should be slightly reinforced, at least not lower than the base material, but the excess height should not exceed 10% of the weld width, and the maximum should not exceed 3 mm. If the weld excess height is high, a smooth transition treatment should be formed on both sides of the weld.

[0022] Preferably, the weld outer surface defect detection items include:

[0023] Undercut: Undercut should be avoided during welding, and the local undercut depth of the cover and root should be controlled within 0.25mm;

[0024] Overflow: Overflow is often accompanied by false welding and needs to be removed;

[0025] Incomplete penetration: The weld must be fully penetrated. If the weld is not fully penetrated, the weld needs to be ground off and re-welded.

[0026] Cracks: No cracks of any kind are allowed in the weld. If cracks appear, they must be eradicated and repaired by welding.

[0027] Porosity: All surface pores should be repaired by welding, and whether internal pores need to be repaired by welding depends on the quality grade of the weld.

[0028] Slag inclusion: small slag inclusion is treated as air hole, long slag inclusion is determined according to ISO 5817B grade requirements;

[0029] The weld is too wide: The weld width is generally 3mm±1mm on both sides of the groove. Welds that are too wide must be polished without damaging the parent material.

[0030] Compared with the prior art, the present invention provides a double-wire submerged arc welding process, which has the following beneficial effects:

[0031] In the present invention, the welding speed is greatly improved compared with single-wire submerged arc welding through the simultaneous welding operation of the front wire and the rear wire, which can significantly improve the production efficiency. The arc heat is concentrated and the molten pool depth is large, which can ensure the penetration and quality of the weld. Thicker plates can be welded, which has great advantages for thick plate welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the overall process framework of the present invention;

[0033] Figure 2 It is a schematic diagram of the relative arrangement of the front thread and the rear thread of the present invention;

[0034] Figure 3 It is a schematic diagram of welding the front wire and the rear wire of the present invention;

[0035] Figure 4 This is a schematic diagram of the present invention for forming a smooth transition process on both sides of the weld;

[0036] Figure 5 It is a schematic diagram of the arc starting position of the annular seam of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Example

[0039] See also Figure 1-Figure 5 , a twin-wire submerged arc welding process, characterized in that it comprises the following steps:

[0040] S1: Preparation before welding:

[0041] Material preparation: Select appropriate base material and welding wire according to welding requirements and ensure their quality meets the standards.

[0042] Flux preparation: The flux should be kept dry and avoid moisture.

[0043] Equipment inspection: Check whether the double-wire submerged arc welding equipment is operating normally and ensure that the welding equipment is well grounded to ensure safe operation.

[0044] Weldment preparation: Clean the weldment and remove impurities such as oil, rust, scale, etc. on the surface to ensure welding quality. Perform groove processing according to welding requirements to ensure that the groove size meets the standards.

[0045] S2: Welding parameter settings:

[0046] The front wire and the rear wire are arranged in a longitudinal column, the front wire is DC reversed (DCEP), the front wire can be welded alone, the rear wire is powered by AC (AC) to reduce the mutual influence and magnetic blow between the arc and the front wire, the rear wire cannot be welded alone, the front wire specification is The front wire is perpendicular to the weldment, the end of the front wire is 3mm-5mm away from the weldment, the extension length of the front wire is 32mm-40mm, and the rear wire specification is The rear wire is inclined 12°-15° to the front wire, and the end of the rear wire is 4mm-6mm away from the weldment. The extended length of the rear wire is the same as that of the front wire, because the rear wire starts the arc in the molten pool of the front wire. The molten pool must be established after the front wire starts the arc before the rear wire can start the arc. Therefore, the end of the rear wire should be 3mm±0.5mm higher than the front wire. The distance between the front and rear wires is 20mm-35mm. If the distance between the front and rear wires is too large, the rear wire will not be easy to start the arc, it will be easy to leak light, and it will be easy to explode the arc. If the distance between the front and rear wires is too small, the distance between the front and rear wires will increase the arc interference between the front and rear wires, and the failure to spread the molten pool will have a certain impact on the forming. The distance between the front and rear wires is as follows: Figure 2As shown, the front wire and the rear wire act on the same molten pool. The welding arc of the front wire is to ensure penetration, with the aim of obtaining a greater molten depth. The welding arc of the rear wire is to increase the molten width. The direction of the rear wire arc has a great influence on the weld formation. When the rear wire arc blows in the welding direction, the molten depth and width are large, and a good weld formation can be obtained. On the contrary, although the molten depth increases, the molten width is not large, which is not conducive to weld formation. In double-wire welding, the front wire arc and the rear wire arc act on a molten pool together. The molten pool is enhanced by the stirring effect of the arc, which can effectively eliminate the weld. The weld edge is not fused and not fully penetrated. At the same time, the molten pool formed during welding is longer. The metal stays in its solid solution state for a longer time. Compared with the cooling speed and thermal cycle of single arc, the trace elements in the weld have a longer time to diffuse and the gas has a longer time to escape, which plays a key role in preventing cold cracks. The bottom area of ​​the molten pool is larger than that of a single molten pool, and it is not easy to form a pear-shaped weld bead, which can reduce the probability of thermal cracks at the root of the weld. At the same time, it also effectively avoids the formation of pores. The comparison between front wire welding and rear wire welding can be seen in Figure 3 .

[0047] S3: Arc starting and welding

[0048] Arc striking: Install the arc striking and extinguishing plate. The material, thickness and groove size of the arc striking and extinguishing plate should be the same as the base material of the weldment as much as possible. After the arc striking and extinguishing plate is grooved, the carbon planer metal slag should be cleaned before welding. Pay attention to safety when striking the arc to avoid arc burning the operator. The size of the arc striking and extinguishing plate should not be less than 80mmx150mm, and 100mmx180mm is recommended. The arc striking and extinguishing weld length should be within the range of 80mm-100mm;

[0049] Welding process: Two welding wires are fed into the weld at the same time, and the heat of the arc melts the welding wires and the base material to form a weld. The operator should pay close attention to the arc stability, weld formation and molten pool during the welding process, and adjust the welding parameters in time. The coverage height of the flux should be maintained during the welding process to ensure the protective effect of the weld. Flux needs to be added during the welding process.

[0050] S4: Post-welding treatment

[0051] Weld cleaning: After welding is completed, the welding slag and spatter on the weld surface should be cleaned in time to ensure the appearance quality of the weld.

[0052] Weld inspection: Perform visual inspection on the weld to check whether the shape, size and surface quality of the weld meet the standards.

[0053] The specific specifications of welding wire and flux are:

[0054]

[0055] Weld shape and size: butt welds should be slightly enhanced, at least not lower than the parent material, but the excess height should not exceed 10% of the weld width, and the maximum should not exceed 3mm. If the weld excess height is high, a smooth transition treatment should be formed on both sides of the weld, as shown in the following example: Figure 4 As shown, there are three types of fillet welds: with excess height, smooth transition, and weakened transition. Weakened welds should be selected for dynamic loads, and strengthened welds are allowed for static loads, but the excess height does not exceed 3mm. Unless otherwise specified, the weld feet are symmetrical (the long angle side of the weld throat with a long side ≤ 1.5mm + 15% is acceptable).

[0056] Weld surface defect detection items include but are not limited to:

[0057] Undercut: Undercut should be prevented during welding, but it is difficult to avoid. The local undercut depth of the cover and root should be controlled within 0.25mm. In principle, undercut is not allowed.

[0058] Overflow: Overflow is often accompanied by false welding and needs to be removed;

[0059] Incomplete penetration: The weld must be fully penetrated. If the weld is not fully penetrated, the weld needs to be ground off and re-welded.

[0060] Cracks: No cracks of any kind are allowed in the weld. If cracks appear, they must be eradicated and repaired by welding.

[0061] Porosity: All surface pores should be repaired by welding, and whether internal pores need to be repaired by welding depends on the quality grade of the weld.

[0062] Slag inclusion: small slag inclusion is treated as air hole, long slag inclusion is determined according to ISO 5817B grade requirements;

[0063] The weld is too wide: The weld width is generally 3±1mm on both sides of the groove. Welds that are too wide must be polished without damaging the parent material;

[0064] Defects not listed are based on ISO 5817 B grade.

[0065] In summary, under normal circumstances, as the welding current increases, the arc voltage increases accordingly, the root weld is deep, the arc voltage should be low, and the welding speed should be fast to avoid undercutting and slag removal difficulties. The welding current depends on the requirements. If the root penetration is to be guaranteed, the current can be slightly larger, but the upper limit cannot be selected. Excessive current (when the voltage is low) often results in a small forming coefficient (melt width to melt depth) and easy cracking. Too low a welding speed will cause coarse grains and easily lead to a decrease in the mechanical properties of the weld. In order to avoid undercutting and grooves, the wire position must be accurate, the groove is wide, and multiple passes should be used for the same layer. The overlap between the two passes should be 1 / 1 of the melt width. / 3~1 / 2, submerged arc welding is short-circuit arc starting. The higher the no-load voltage of the equipment, the greater the short-circuit current, and the easier it is to start the arc. To facilitate arc starting, the wire head can be clamped with wire pliers to sharpen the corners or ground into a thinner shape with a grinder. To avoid incomplete welding due to poor arc starting, the contact tightness between the welding wire and the weldment should be appropriate. Generally, it is better to be able to easily scratch. Too tight contact between the welding wire and the weldment often causes a short circuit, failure to start the arc, the entire section of the welding wire turns red, or even explodes, causing overflow at the arc starting point, no penetration, and easily causing misalignment. The contact tightness between the welding wire and the weldment is too loose and isolated by the flux, resulting in circuit blockage and even the head of the machine being lifted up, and the arc starting position of the annular seam is seen Figure 5 The smaller the diameter of the weldment, the greater the offset value b required. A small b value will result in a high, sharp weld, deep penetration, and even cause molten iron loss. A large b value will result in a flat weld, shallow penetration, molten iron backflow, and cause an unstable welding process. The influence of the b' value is not as sensitive as b. A small b' value will produce the same situation as a large b value, and a large b' value will produce the same situation as a small b value. Usually the offset is between 40mm and 80mm. For girth welding, the weldment can be controlled to rotate first, causing friction between the welding wire and the weldment, and then power on to start the arc. When the submerged arc welding is ended, the equipment control circuit stops feeding the wire first and then cuts off the power. To prevent To prevent the welding wire from sticking to the molten pool, the wire feeding must be stopped before pressing the stop button. The longitudinal weld should be extinguished on the arc extinguishing plate. The arc pit should be completely outside the weldment, with a length of 80mm-100mm. The arc starting and extinguishing positions of the circumferential seam should be located within the 300mm-500mm interval of the intersection of the T-seam (the intersection of the longitudinal circumferential seam), and the length of the arc extinguishing overlapping area should be not less than 50mm. If the arc is started and extinguished in other areas, it must be marked in time. Before welding the next weld, the slag on the previous weld should be cleaned up. The flux used should be in accordance with TT1-WI-TQ-040 "Welding Material Quality Management Regulations".

[0066] Reference standards include

[0067] GB / T 14957 Steel wire for fusion welding

[0068] GB / T 5293 Carbon steel welding wire and flux for submerged arc welding

[0069] AWS A5.17 Carbon Steel Welding Wire and Flux Standard for Submerged Arc Welding

[0070] EN 756 Specification for solid wires, fluxes and tube wire-flux combinations for submerged arc welding of non-alloy and fine grain steels

[0071] EN 760 Specification for submerged arc welding fluxes

[0072] ISO 5817 Quality inspection grades for welded joints of steel, nickel, titanium and their alloys

[0073] ISO 14171 Welding consumables - Electrodes and electrode-flux mixtures for submerged arc welding of non-alloy and fine-grained steels

[0074] ISO 14174 Welding consumables - Fluxes for submerged arc welding and electroslag welding - Classification

[0075] JIS Z3351 Submerged arc welding solid wire for carbon steel and low alloy steel

[0076] JIS Z3352 Carbon steel and low alloy steel submerged arc welding flux

[0077] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A twin-wire submerged arc welding process, characterized in that: The following steps are involved: S1: Preparation before welding: Welding wire preparation: select appropriate welding wire according to welding requirements and ensure its quality meets the standards; Flux preparation: the flux should be kept dry and avoid moisture; Equipment inspection: Check whether the double-wire submerged arc welding equipment is operating normally and ensure that the welding equipment is well grounded to ensure safe operation; Weldment preparation: clean the weldment, remove the oil, rust, scale and impurities on the surface to ensure the welding quality, perform groove processing according to welding requirements, and ensure that the groove size meets the standard; S2: Welding parameter settings: The front wire and the rear wire are arranged in a longitudinal column, the front wire is reversely connected to DC, and the rear wire is powered by AC to reduce the mutual influence and magnetic blow between the arc and the front wire. The specifications of the front wire are The front wire is perpendicular to the weldment, the end of the front wire is 3mm-5mm away from the weldment, the extension length of the front wire is 32mm-40mm, and the rear wire specification is The rear wire is inclined 12°-15° to the front wire, the end of the rear wire is 4mm-6mm away from the weldment, the extended length of the rear wire is the same as that of the front wire, and the distance between the front and rear wires is 20mm-35mm; S3: Arc starting and welding Arc striking: Install the arc striking and extinguishing plate. The material, thickness and groove size of the arc striking and extinguishing plate should be the same as the base material of the weldment as much as possible. After the arc striking and extinguishing plate is grooved, the carbon planing metal slag should be cleaned before welding. Pay attention to safety when striking the arc to avoid arc burning the operator; Welding: The front wire and the rear wire are fed into the weld at the same time. The heat of the arc melts the front wire, the rear wire and the base material to form a weld. The operator should pay close attention to the arc stability, weld formation and molten pool during the welding process, and adjust the welding parameters in time. The coverage height of the flux should be maintained during the welding process to ensure the protection effect of the weld. S4: Post-welding treatment Weld cleaning: After welding, the welding slag and spatter on the weld surface should be cleaned in time to ensure the appearance quality of the weld; Weld inspection: Perform visual inspection on the weld to check whether the shape, size and surface quality of the weld meet the standards.

2. A double-wire submerged arc welding process according to claim 1, characterized in that: In step S3, since the rear wire is arced in the molten pool of the front wire, the molten pool must be established after the front wire is arced before the rear wire can be arced, so the end of the rear wire must be 3mm±0.5mm higher than the front wire.

3. A double-wire submerged arc welding process according to claim 2, characterized in that: In step S3, the size of the arc striking and extinguishing plate is not less than 80 mm x 150 mm, and the length of the arc striking and extinguishing weld is in the range of 80 mm to 100 mm.

4. A double-wire submerged arc welding process according to claim 3, characterized in that: The shape and size of the weld in step S4: the butt weld should be slightly enhanced, at least not lower than the base material, but the excess height should not exceed 10% of the weld width, and the maximum should not exceed 3 mm. If the weld excess height is high, a smooth transition treatment should be formed on both sides of the weld.

5. A double-wire submerged arc welding process according to claim 4, characterized in that: The weld outer surface defect detection items include: Undercut: Undercut should be avoided during welding, and the local undercut depth of the cover and root should be controlled within 0.25mm; Overflow: Overflow is often accompanied by false welding and needs to be removed; Incomplete penetration: The weld must be fully penetrated. If the weld is not fully penetrated, the weld needs to be ground off and re-welded. Cracks: No cracks of any kind are allowed in the weld. If cracks appear, they must be eradicated and repaired by welding. Porosity: All surface pores should be repaired by welding, and whether internal pores need to be repaired by welding depends on the quality grade of the weld. Slag inclusion: small slag inclusion is treated as air hole, long slag inclusion is determined according to ISO 5817B grade requirements; The weld is too wide: The weld width is generally 3±1mm on both sides of the groove. Welds that are too wide must be polished without damaging the parent material.

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