It can be seen from Table 3 that the strip surfacing has a higher deposition rate and the plasma arc surfacing has a lower dilution rate. In recent years, on this basis, researchers have further developed advanced strip surfacing technology and plasma arc surfacing technology that are both efficient and low-dilution.
A welding method in which metal is melted by electric welding or gas welding and stacked on tools or machine parts. Usually used to repair worn and cracked parts.
Overview application
At present, there are many surfacing methods used in production, and the dilution ratio and deposition rate of several surfacing methods are shown in [Table].
Comparison of characteristics of several surfacing methods
Surfacing method Dilution rate (%) Cladding speed (kg/h) Submerged arc surfacing monofilament 30～60 4.5～11.3 Multifilament 15～25 11.3～27.2 Series arc 10～25 11.3～15.9 Single band 10～20 12～36 Multi-band pole 8～15 22～68 Plasma arc surfacing automatic powder feeding 5～15 0.5～6.8 Manual wire feeding 5～15 0.5～3.6 Automatic wire feeding 5～15 0.5～3.6 Double hot wire 5～15 13 ～27 Molten gas protection arc welding: self-protection arc surfacing 10～40 0.9～5.4 15～40 2.3～11.3 with electrode electroslag surfacing 10～14 15～75
It can be seen from Table 3 that the strip surfacing has a higher deposition rate and the plasma arc surfacing has a lower dilution rate. In recent years, on this basis, researchers have further developed advanced strip surfacing technology and plasma arc surfacing technology that are both efficient and low-dilution.
Cold welding surfacing technology Cold welding surfacing technology uses the principle of high-frequency electric spark discharge to weld the workpiece without thermal surfacing to repair the surface defects and wear of the metal workpiece, which can ensure the integrity of the workpiece. It can also use its strengthening function. The workpiece is reinforced to achieve wear resistance, heat resistance, corrosion resistance, and the like of the workpiece.
The cold welding surfacing equipment does not deform, does not anneal, has high welding strength and is resistant to wear after repairing metal workpieces. It can pass the metallographic, tensile and hardness tests, and the metallurgical combination of the welding material and the substrate ensures the firmness of the welding. Commonly used in precision castings for pinholes, pores, burrs, flash, bumps, scratches, chipping, sag, blisters, cracks, wear, indentation, manufacturing errors, manufacturing defects, repair of weld defects and mechanical surface strengthening.
Application field of cold welding technology
1. Mold manufacturing industry
The surface of the plastic mold is roughened to increase the beauty and service life; the helmet plastic mold parting surface surfacing repair; the aluminum alloy die-casting mold diversion cone surface strengthening; the mold cavity tolerance, wear, scratch and other repair and strengthening.
2. Plastics and rubber industry
Rubber and plastic machinery parts repair, rubber, plastic parts used for mold tolerance, wear and repair.
3. Aviation and aerospace industry
Aircraft engine parts, turbines, turbine shaft repair or repair, rocket nozzle surface intensive repair, aircraft outer panel repair, satellite external reinforcement or repair, local carburization of titanium alloy parts, local seepage of iron-based superalloy parts Carbon strengthening, anti-corrosion coating such as surface impregnation of magnesium alloy, partial defect surfacing repair of magnesium alloy parts, partial surfacing repair of nickel-base/cobalt-based superalloy blade workpieces, such as: wear of blade crown damping surface and tip And ablation of the vanes.
4. Automobile and locomotive manufacturing and maintenance industry
In the automobile manufacturing and maintenance industry, it is used for complementing and repairing cams, crankshafts, pistons, cylinders, brake discs, impellers, hubs, clutches, friction plates, exhaust valves, etc., and repairing the surface weld bead defects of the automobile body.
5. Shipbuilding and power industry
Repair of electric crankshafts, bushings, bushings, electrical components, resistors, etc., welding of electric railway machine wheels and bottom line rail connecting pieces, electroplating factory conductive roller, metal oxidation treatment of copper and aluminum electrodes.
6, machinery industry
Correcting over-traveled workpieces and repairing machine tool guides, various shafts, cams, hydraulic presses, hydraulic press plungers, cylinder walls, journals, rollers, gears, pulleys, mandrels for spring forming, plug gauges, ring gauges, various rollers , rods, columns, locks, bearings, etc.
7. Foundry industry
Repair of defects such as blowholes in iron, copper and aluminum castings, and repair of aluminum models.
Broadband electroslag surfacing technology (1) produces background
The inner surface of the hydrogenation reactor, the raw-flow synthesis tower, the coal liquefaction reactor and the thick-walled pressure vessel of the nuclear power plant in the petrochemical industry require large-area surfacing welding of high-temperature resistant, anti-oxidation and hydrogen sulfide-corroded stainless steel" target=_blank >Stainless steel lining. In the 1970s, a large number of submerged arc surfacing (SAW) technologies were used at home and abroad. The width of the strip also developed from a narrow band to a broadband direction of 60mm, 90mom, 120mm, 150mm. In the dilution rate and deposition rate, there has been a great progress in the submerged arc welding, but with the increasing size and high parameterization of the pressure vessel, the surfacing technology has been promoted to a higher quality and more efficient direction. In the early 1970s, Germany first invented, and was further improved by Japan, the United States, the former Soviet Union and other countries with the electrode electroslag surfacing technology because it has higher production efficiency, lower dilution rate and good weld than the submerged arc. The advantages of forming, etc., have been rapidly developed and widely used at home and abroad in recent years.
(2) Technical content and technical key
The electrode electroslag welding is to use the resistance of the conductive slag to thermally melt the surfacing material and the base material. Except for the introduction stage, the entire surfacing process should be provided with an arc. In order to obtain a stable electroslag surfacing process, there are several technical key points:
1) Welding power supply
In the electroslag surfacing process, the stability of the slag pool has a great influence on the quality of the surfacing, and the fluctuation of the voltage is the most critical factor affecting the stability of the slag pool. Therefore, it is desirable to minimize the voltage fluctuation during the surfacing process. DC power supply with pressure characteristics. In addition, the power supply should have low voltage, high current output, high control accuracy, strong ability to compensate for network voltage fluctuations and reliable protection. The rated current of the power supply varies depending on the bandwidth used. Generally, it is 60mm × 0.5mm, the rated current is 1500A, the 90mm × 0.5mm is 2000A, and the 120mm × 0.5mm is 25O0A.
2) flux
Another necessary condition for obtaining a stable electroslag process is that the flux must have good electrical conductivity. Generally, the electrical conductivity of the electroslag surfacing flux needs to be 2 to 3 Ω-1 cm-1, which is 4 to 5 times that of the ordinary submerged arc welding flux. At present, the electroslag flux used at home and abroad is mostly sintered. The conductivity of the flux depends on the amount of chloride (NaF, CaF2, Na3AIF6, etc.) in the flux composition. When the chloride (mass fraction) is less than 40%, the surfacing process is an arc process, at 40% to 50%. The range is roughly the arc and electroslag combination process; when the chloride is greater than 50%, a full electroslag process can be formed. CaF2 is both a good conductive material and a major slagging agent, so CaF2 is usually the main component of electroslag surfacing flux. In addition to electrical conductivity, the flux also needs to have good surfacing process (slag removal, forming, wettability) and good metallurgical properties (small alloy elements burn less, less adverse element increments), suitable particle size (general ratio Submerged arc welding flux is fine). At present, the above requirements have been met, and there are many types of fluxes that have been used for production, such as foreign FJ-1 (Japan), EST122 (Germany), Sandvik 37S (USA), domestic SJ15, SHD202, and the like.
3) Magnetic control device
For the electroslag surfacing of the broadband pole (with a width greater than 60mm), due to the magnetic contraction effect, the undercut layer will be undercut. As the strip width increases, the surfacing current increases, and the undercut phenomenon becomes heavier. An external magnetic field is used to prevent the occurrence of undercuts (magnetron method). as the picture shows. At the same time, the magnetic pole position must be reasonably arranged, and a reasonable excitation current should be selected. If the applied magnetic field is too strong or too weak, the formation of the surfacing weld bead will be affected (Fig. 2). The magnetron current of the two poles should be adjustable separately. For example, for a workpiece with a non-preheated flat welding position, the control currents of the south and north poles of the magnetron are 1.5A and 3.5A respectively when the belt is extremely 60mm×0.5mm, and 3A for the strips of 90mm×0.5mm respectively. And 3.5A.
4) Control of process parameters
The use of reasonable surfacing process parameters is an effective means to ensure stable electroslag surfacing process and good weld quality. The most important process parameters affecting the quality of electroslag surfacing are welding voltage, current and welding speed, followed by dry elongation, thickness of flux layer, overlap between welds, and welding position.
1 Precise control of the welding voltage is of great significance for the electrode slag surfacing. When the voltage is too low, there is a tendency to adhere to the base metal. The voltage is too high, the arc phenomenon is significantly increased, the molten pool is unstable, and the splash is also increased. The recommended welding voltage can be preferably between 20 and 30V.
2 The welding current has a great influence on the quality of the electroslag surfacing. As the welding current increases, the penetration depth, melt width and stack height of the weld bead increase with this, while the dilution rate decreases slightly, but the current is too large and the splash increases. Different widths of the strip should be selected for different welding currents. For example, for a strip of φ75 mm × 0.4 mm, the current can be preferably between 1000 and 1300 A.
3 As the welding speed increases, the weld width and stack height decrease, the penetration depth and dilution rate increase, and the welding speed is too high, which will increase the arc rate, and control the certain dilution rate to ensure the performance of the weld overlay. The welding speed is generally controlled at 15 to 17 cm/min.
4 When the graded electroslag surfacing is used, the inclination of the base metal will affect the dilution rate and bead forming. It is generally recommended to use the horizontal position or the slope with a slight slope (1o~2o).
5 Other recommended values ​​are: the extension length of the strip is 25~35mm, the thickness of the flux is 25~35mm, and the weld overlap is 5~l0mm.
(3) Advantages, disadvantages and application range
The combination of electroslag surfacing and arc submerged arc welding has the following advantages:
1) The deposition efficiency is high, at medium current, 50% higher than submerged arc welding;
2) The melting depth is shallow and uniform, the base material dilution rate is low, generally can be controlled below 10%, which is twice as small as submerged arc welding, and single layer surfacing can meet the performance requirements.
3) The surfacing layer is well formed, it is not easy to have defects such as slag inclusion, the surface quality is excellent, the surface irregularity is less than 0.5mm (more than lmm during submerged arc surfacing), so the surface does not need mechanical processing, saving material and saving time.
4) The burning of the alloy elements in the strip and the increase of the unfavorable elements are rare, and the plasticity and toughness of the surfacing layer are higher than that of the submerged arc.
5) Because the carbon diffusion layer of the joint fusion zone is narrow and the martensite zone width is small, the joint fusion zone performance is better than that of the submerged arc surfacing. Due to the above advantages, the electrode slag surfacing has been widely used in large-area surfacing of pressure vessels in hydrogenation control reactors, gas engineering hot wall exchange furnaces and nuclear power plant equipment in recent years.
Http://news.chinawj.com.cn Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn
A welding method in which metal is melted by electric welding or gas welding and stacked on tools or machine parts. Usually used to repair worn and cracked parts.
Overview application
At present, there are many surfacing methods used in production, and the dilution ratio and deposition rate of several surfacing methods are shown in [Table].
Comparison of characteristics of several surfacing methods
Surfacing method Dilution rate (%) Cladding speed (kg/h) Submerged arc surfacing monofilament 30～60 4.5～11.3 Multifilament 15～25 11.3～27.2 Series arc 10～25 11.3～15.9 Single band 10～20 12～36 Multi-band pole 8～15 22～68 Plasma arc surfacing automatic powder feeding 5～15 0.5～6.8 Manual wire feeding 5～15 0.5～3.6 Automatic wire feeding 5～15 0.5～3.6 Double hot wire 5～15 13 ～27 Molten gas protection arc welding: self-protection arc surfacing 10～40 0.9～5.4 15～40 2.3～11.3 with electrode electroslag surfacing 10～14 15～75
It can be seen from Table 3 that the strip surfacing has a higher deposition rate and the plasma arc surfacing has a lower dilution rate. In recent years, on this basis, researchers have further developed advanced strip surfacing technology and plasma arc surfacing technology that are both efficient and low-dilution.
Cold welding surfacing technology Cold welding surfacing technology uses the principle of high-frequency electric spark discharge to weld the workpiece without thermal surfacing to repair the surface defects and wear of the metal workpiece, which can ensure the integrity of the workpiece. It can also use its strengthening function. The workpiece is reinforced to achieve wear resistance, heat resistance, corrosion resistance, and the like of the workpiece.
The cold welding surfacing equipment does not deform, does not anneal, has high welding strength and is resistant to wear after repairing metal workpieces. It can pass the metallographic, tensile and hardness tests, and the metallurgical combination of the welding material and the substrate ensures the firmness of the welding. Commonly used in precision castings for pinholes, pores, burrs, flash, bumps, scratches, chipping, sag, blisters, cracks, wear, indentation, manufacturing errors, manufacturing defects, repair of weld defects and mechanical surface strengthening.
Application field of cold welding technology
1. Mold manufacturing industry
The surface of the plastic mold is roughened to increase the beauty and service life; the helmet plastic mold parting surface surfacing repair; the aluminum alloy die-casting mold diversion cone surface strengthening; the mold cavity tolerance, wear, scratch and other repair and strengthening.
2. Plastics and rubber industry
Rubber and plastic machinery parts repair, rubber, plastic parts used for mold tolerance, wear and repair.
3. Aviation and aerospace industry
Aircraft engine parts, turbines, turbine shaft repair or repair, rocket nozzle surface intensive repair, aircraft outer panel repair, satellite external reinforcement or repair, local carburization of titanium alloy parts, local seepage of iron-based superalloy parts Carbon strengthening, anti-corrosion coating such as surface impregnation of magnesium alloy, partial defect surfacing repair of magnesium alloy parts, partial surfacing repair of nickel-base/cobalt-based superalloy blade workpieces, such as: wear of blade crown damping surface and tip And ablation of the vanes.
4. Automobile and locomotive manufacturing and maintenance industry
In the automobile manufacturing and maintenance industry, it is used for complementing and repairing cams, crankshafts, pistons, cylinders, brake discs, impellers, hubs, clutches, friction plates, exhaust valves, etc., and repairing the surface weld bead defects of the automobile body.
5. Shipbuilding and power industry
Repair of electric crankshafts, bushings, bushings, electrical components, resistors, etc., welding of electric railway machine wheels and bottom line rail connecting pieces, electroplating factory conductive roller, metal oxidation treatment of copper and aluminum electrodes.
6, machinery industry
Correcting over-traveled workpieces and repairing machine tool guides, various shafts, cams, hydraulic presses, hydraulic press plungers, cylinder walls, journals, rollers, gears, pulleys, mandrels for spring forming, plug gauges, ring gauges, various rollers , rods, columns, locks, bearings, etc.
7. Foundry industry
Repair of defects such as blowholes in iron, copper and aluminum castings, and repair of aluminum models.
Broadband electroslag surfacing technology (1) produces background
The inner surface of the hydrogenation reactor, the raw-flow synthesis tower, the coal liquefaction reactor and the thick-walled pressure vessel of the nuclear power plant in the petrochemical industry require large-area surfacing welding of high-temperature resistant, anti-oxidation and hydrogen sulfide-corroded stainless steel" target=_blank >Stainless steel lining. In the 1970s, a large number of submerged arc surfacing (SAW) technologies were used at home and abroad. The width of the strip also developed from a narrow band to a broadband direction of 60mm, 90mom, 120mm, 150mm. In the dilution rate and deposition rate, there has been a great progress in the submerged arc welding, but with the increasing size and high parameterization of the pressure vessel, the surfacing technology has been promoted to a higher quality and more efficient direction. In the early 1970s, Germany first invented, and was further improved by Japan, the United States, the former Soviet Union and other countries with the electrode electroslag surfacing technology because it has higher production efficiency, lower dilution rate and good weld than the submerged arc. The advantages of forming, etc., have been rapidly developed and widely used at home and abroad in recent years.
(2) Technical content and technical key
The electrode electroslag welding is to use the resistance of the conductive slag to thermally melt the surfacing material and the base material. Except for the introduction stage, the entire surfacing process should be provided with an arc. In order to obtain a stable electroslag surfacing process, there are several technical key points:
1) Welding power supply
In the electroslag surfacing process, the stability of the slag pool has a great influence on the quality of the surfacing, and the fluctuation of the voltage is the most critical factor affecting the stability of the slag pool. Therefore, it is desirable to minimize the voltage fluctuation during the surfacing process. DC power supply with pressure characteristics. In addition, the power supply should have low voltage, high current output, high control accuracy, strong ability to compensate for network voltage fluctuations and reliable protection. The rated current of the power supply varies depending on the bandwidth used. Generally, it is 60mm × 0.5mm, the rated current is 1500A, the 90mm × 0.5mm is 2000A, and the 120mm × 0.5mm is 25O0A.
2) flux
Another necessary condition for obtaining a stable electroslag process is that the flux must have good electrical conductivity. Generally, the electrical conductivity of the electroslag surfacing flux needs to be 2 to 3 Ω-1 cm-1, which is 4 to 5 times that of the ordinary submerged arc welding flux. At present, the electroslag flux used at home and abroad is mostly sintered. The conductivity of the flux depends on the amount of chloride (NaF, CaF2, Na3AIF6, etc.) in the flux composition. When the chloride (mass fraction) is less than 40%, the surfacing process is an arc process, at 40% to 50%. The range is roughly the arc and electroslag combination process; when the chloride is greater than 50%, a full electroslag process can be formed. CaF2 is both a good conductive material and a major slagging agent, so CaF2 is usually the main component of electroslag surfacing flux. In addition to electrical conductivity, the flux also needs to have good surfacing process (slag removal, forming, wettability) and good metallurgical properties (small alloy elements burn less, less adverse element increments), suitable particle size (general ratio Submerged arc welding flux is fine). At present, the above requirements have been met, and there are many types of fluxes that have been used for production, such as foreign FJ-1 (Japan), EST122 (Germany), Sandvik 37S (USA), domestic SJ15, SHD202, and the like.
3) Magnetic control device
For the electroslag surfacing of the broadband pole (with a width greater than 60mm), due to the magnetic contraction effect, the undercut layer will be undercut. As the strip width increases, the surfacing current increases, and the undercut phenomenon becomes heavier. An external magnetic field is used to prevent the occurrence of undercuts (magnetron method). as the picture shows. At the same time, the magnetic pole position must be reasonably arranged, and a reasonable excitation current should be selected. If the applied magnetic field is too strong or too weak, the formation of the surfacing weld bead will be affected (Fig. 2). The magnetron current of the two poles should be adjustable separately. For example, for a workpiece with a non-preheated flat welding position, the control currents of the south and north poles of the magnetron are 1.5A and 3.5A respectively when the belt is extremely 60mm×0.5mm, and 3A for the strips of 90mm×0.5mm respectively. And 3.5A.
4) Control of process parameters
The use of reasonable surfacing process parameters is an effective means to ensure stable electroslag surfacing process and good weld quality. The most important process parameters affecting the quality of electroslag surfacing are welding voltage, current and welding speed, followed by dry elongation, thickness of flux layer, overlap between welds, and welding position.
1 Precise control of the welding voltage is of great significance for the electrode slag surfacing. When the voltage is too low, there is a tendency to adhere to the base metal. The voltage is too high, the arc phenomenon is significantly increased, the molten pool is unstable, and the splash is also increased. The recommended welding voltage can be preferably between 20 and 30V.
2 The welding current has a great influence on the quality of the electroslag surfacing. As the welding current increases, the penetration depth, melt width and stack height of the weld bead increase with this, while the dilution rate decreases slightly, but the current is too large and the splash increases. Different widths of the strip should be selected for different welding currents. For example, for a strip of φ75 mm × 0.4 mm, the current can be preferably between 1000 and 1300 A.
3 As the welding speed increases, the weld width and stack height decrease, the penetration depth and dilution rate increase, and the welding speed is too high, which will increase the arc rate, and control the certain dilution rate to ensure the performance of the weld overlay. The welding speed is generally controlled at 15 to 17 cm/min.
4 When the graded electroslag surfacing is used, the inclination of the base metal will affect the dilution rate and bead forming. It is generally recommended to use the horizontal position or the slope with a slight slope (1o~2o).
5 Other recommended values ​​are: the extension length of the strip is 25~35mm, the thickness of the flux is 25~35mm, and the weld overlap is 5~l0mm.
(3) Advantages, disadvantages and application range
The combination of electroslag surfacing and arc submerged arc welding has the following advantages:
1) The deposition efficiency is high, at medium current, 50% higher than submerged arc welding;
2) The melting depth is shallow and uniform, the base material dilution rate is low, generally can be controlled below 10%, which is twice as small as submerged arc welding, and single layer surfacing can meet the performance requirements.
3) The surfacing layer is well formed, it is not easy to have defects such as slag inclusion, the surface quality is excellent, the surface irregularity is less than 0.5mm (more than lmm during submerged arc surfacing), so the surface does not need mechanical processing, saving material and saving time.
4) The burning of the alloy elements in the strip and the increase of the unfavorable elements are rare, and the plasticity and toughness of the surfacing layer are higher than that of the submerged arc.
5) Because the carbon diffusion layer of the joint fusion zone is narrow and the martensite zone width is small, the joint fusion zone performance is better than that of the submerged arc surfacing. Due to the above advantages, the electrode slag surfacing has been widely used in large-area surfacing of pressure vessels in hydrogenation control reactors, gas engineering hot wall exchange furnaces and nuclear power plant equipment in recent years.
Http://news.chinawj.com.cn Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn
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