Foreword
Aluminum and its alloys are increasingly used in industrial production and social life. Due to their small specific gravity, good electrical and thermal conductivity, excellent castability and machinability, aluminum plays an important role in modern industrial materials.
Aluminum is more difficult to weld than ferrous metals, especially hard aluminum, super hard aluminum and cast aluminum. The poor soldering process of aluminum is mainly manifested in the difficulty in removing the oxide film.
The Ukrainian Barton Welding Institute invented the active flux in the early 1960s when welding titanium alloys. At the time, a thin mixture of metal was applied to the surface of the metal. The main function of the coating was to compress the arc, rather than chemically affecting the molten pool. The American Edison Welding Institute (EWI) began the development of active flux in the 1990s and was funded by EWI and other members under the auspices of the Naval Connection Center (NJC). Currently, active flux in the US has been commercially available. Application on. The TWI Welding Institute of the United Kingdom has applied the active flux as the core of research.
The main function of the active flux is to compress the arc, rather than chemically affecting the molten pool, but it is also feasible to use an activator to break or reduce the oxide film of aluminum. The cored aluminum wire is a solder that itself contains certain active elements that act as fluxes.
The products of the reducing agent reacted with Al2O3 are AlCl3 and AlxFy. AlCl3 can be converted into a gas to evaporate. The Al2O3 film is simultaneously broken during the evaporation of AlCl3. AlxFy is a composite salt with good fluidity, density less than aluminum, floating on the surface and edge of the weld. The color is light gray.
The use of a flux-cored aluminum wire to weld aluminum alloys can save energy and increase production efficiency, especially in improving weld quality. Compared with the traditional AC TIG welding, the TIG positive welding process based on the cored aluminum welding wire has many advantages, such as smooth appearance, smooth, deep penetration, less slag inclusion, and almost no porosity.
1. Manufacturing technology of core aluminum wire
The manufacturing technology of the cored aluminum welding wire can draw on the manufacturing method of the steel flux cored wire. The manufacturing process of the steel flux cored wire includes several processes such as rolling, wire drawing, post-treatment and layer winding. The raw material of the seamless flux cored wire is a coiled steel pipe, which may be a seamless steel pipe or a welded steel pipe.
The tubular electrode method for manufacturing the flux-cored wire is to first mix the core powder into a sintered flux form, and then fill the steel pipe (16-25mm) to fill the core by vibration, and then roll, rough, annealed and finely drawn. Finished products are produced by processes such as copper plating and layer winding. This method was tested during the research process. The reducing agent and the alloy powder were placed in an aluminum tube, and rolled-drawn-diffused and annealed to form a tubular electrode. The main problem is the low production efficiency and the unstable filling factor of the powder.
In the casting method, the reduced powder is added to an aluminum alloy ingot and fully compacted to form a core ingot. In the first step, the brazing filler metal is formed into a porous casting blank, and then the honeycomb green material is immersed in the active flux solution to immerse the solution in the voids in the blank. The ingot is cooled and then extruded. The key to the process of this method is the pretreatment and addition process of the active flux.
The mechanical alloying method is to mix, press and extrude the powdery raw materials according to the principle of powder metallurgy. The process is to fully mix the reduced powder, aluminum powder and other added metal powder, pressurize the mixed metal powder at a certain temperature to form a powder ingot with a certain strength, and keep the powder in a controlled atmosphere. The ingot forms a "brazing ingot" which is finally extruded into a material and reduced in diameter by means of a rolling die.
The laminar extrusion method is to manufacture the flux-cored wire by continuous casting and isothermal extrusion technology. The continuous casting technology can obtain the “Lotus†ingot with uniform structure and stable composition. The isothermal extrusion technology can obtain the flux-cored wire blank with stable filling coefficient. .
2. Ingot casting and isothermal extrusion of flux-cored wire
The laminar extrusion method is to compress and deform the aluminum solder ingot containing the active flux in a laminar flow, and the aluminum solder containing no other components is cast into a porous ingot in the form of continuous casting, the outer diameter of the ingot and The inner bore is of constant size, the active flux is filled into the inner bore and compacted.
The compacted solder ingot containing active flux has the following characteristics: the ratio of flux to solder is constant in different cross sections; reinforcing particles (such as SiC) can be added to the active flux to form a composite; the flux is fully coated with solder. .
The key to the laminar extrusion process is the sequential flow of flux and solder. The conditions for sequential flow are the consistency of the rheological properties of the two materials. The rheological properties of the material are related to temperature and compressive stress, and the extrusion temperature and extrusion are adjusted. The pressure can make the rheological properties of two different materials similar, and the well-designed extrusion die shape can make the two materials stably deform in the form of laminar flow.
The isothermal extrusion technique is used in the research process. The flux-cored wire with stable cross-section and uniform filling coefficient can be obtained under specific extrusion temperature and extrusion speed.
3. Flux and wire winding of flux cored wire
Compared with the solid wire, the main features of the internal structure of the cored aluminum wire are as follows: the core is sand-like, viscosity-free, non-plastic, and the deformation and flow of the core are mainly caused by the pressing force generated when the surrounding material is deformed. Friction; wire deformation ability is significantly reduced.
During the drawing process of the flux-cored wire, the deformation of the wire is divided into two parts, one is the plastic deformation of the metal, and the other is the flow and volume compression of the internal powder, and the two deformations interact and influence each other. The plastic deformation ability of the metal determines whether the drawing can be carried out continuously. The rheological behavior and volume compression degree of the core are related to whether the filling curve of the flux-cored wire is stable, thereby affecting the use of the flux-cored wire and the stability of the welding process.
Due to the presence of the core, the effective cross-sectional area of ​​the flux-cored wire is much smaller than that of the solid wire, so the broken wire during the process of drawing the flux-cored wire is common. Optimizing the deformation mode of the wire during the drawing process is an effective way to improve the drawing processability of the core aluminum wire. The roll die drawing technology used in the research improves the wire deformation mode and significantly improves the wire deformation ability.
The flux-cored wire drawn to the finished size is wound into a disk by a layer winding technique.
4 Conclusion
(1) There are four methods for manufacturing the cored aluminum welding wire, and the laminar extrusion method has the most industrial application prospects.
(2) The continuous casting technology can obtain the “Lianhua†ingot with uniform organization and stable composition, and the isothermal extrusion technology can obtain the flux-cored wire blank with stable filling coefficient.
(3) Roller drawing ensures uniform deformation of the core, super-fine scraping technology ensures the cleanliness of the wire, and the layer winding technology ensures the stability of the wire pointing during the welding process.
Aluminum and its alloys are increasingly used in industrial production and social life. Due to their small specific gravity, good electrical and thermal conductivity, excellent castability and machinability, aluminum plays an important role in modern industrial materials.
Aluminum is more difficult to weld than ferrous metals, especially hard aluminum, super hard aluminum and cast aluminum. The poor soldering process of aluminum is mainly manifested in the difficulty in removing the oxide film.
The Ukrainian Barton Welding Institute invented the active flux in the early 1960s when welding titanium alloys. At the time, a thin mixture of metal was applied to the surface of the metal. The main function of the coating was to compress the arc, rather than chemically affecting the molten pool. The American Edison Welding Institute (EWI) began the development of active flux in the 1990s and was funded by EWI and other members under the auspices of the Naval Connection Center (NJC). Currently, active flux in the US has been commercially available. Application on. The TWI Welding Institute of the United Kingdom has applied the active flux as the core of research.
The main function of the active flux is to compress the arc, rather than chemically affecting the molten pool, but it is also feasible to use an activator to break or reduce the oxide film of aluminum. The cored aluminum wire is a solder that itself contains certain active elements that act as fluxes.
The products of the reducing agent reacted with Al2O3 are AlCl3 and AlxFy. AlCl3 can be converted into a gas to evaporate. The Al2O3 film is simultaneously broken during the evaporation of AlCl3. AlxFy is a composite salt with good fluidity, density less than aluminum, floating on the surface and edge of the weld. The color is light gray.
The use of a flux-cored aluminum wire to weld aluminum alloys can save energy and increase production efficiency, especially in improving weld quality. Compared with the traditional AC TIG welding, the TIG positive welding process based on the cored aluminum welding wire has many advantages, such as smooth appearance, smooth, deep penetration, less slag inclusion, and almost no porosity.
1. Manufacturing technology of core aluminum wire
The manufacturing technology of the cored aluminum welding wire can draw on the manufacturing method of the steel flux cored wire. The manufacturing process of the steel flux cored wire includes several processes such as rolling, wire drawing, post-treatment and layer winding. The raw material of the seamless flux cored wire is a coiled steel pipe, which may be a seamless steel pipe or a welded steel pipe.
The tubular electrode method for manufacturing the flux-cored wire is to first mix the core powder into a sintered flux form, and then fill the steel pipe (16-25mm) to fill the core by vibration, and then roll, rough, annealed and finely drawn. Finished products are produced by processes such as copper plating and layer winding. This method was tested during the research process. The reducing agent and the alloy powder were placed in an aluminum tube, and rolled-drawn-diffused and annealed to form a tubular electrode. The main problem is the low production efficiency and the unstable filling factor of the powder.
In the casting method, the reduced powder is added to an aluminum alloy ingot and fully compacted to form a core ingot. In the first step, the brazing filler metal is formed into a porous casting blank, and then the honeycomb green material is immersed in the active flux solution to immerse the solution in the voids in the blank. The ingot is cooled and then extruded. The key to the process of this method is the pretreatment and addition process of the active flux.
The mechanical alloying method is to mix, press and extrude the powdery raw materials according to the principle of powder metallurgy. The process is to fully mix the reduced powder, aluminum powder and other added metal powder, pressurize the mixed metal powder at a certain temperature to form a powder ingot with a certain strength, and keep the powder in a controlled atmosphere. The ingot forms a "brazing ingot" which is finally extruded into a material and reduced in diameter by means of a rolling die.
The laminar extrusion method is to manufacture the flux-cored wire by continuous casting and isothermal extrusion technology. The continuous casting technology can obtain the “Lotus†ingot with uniform structure and stable composition. The isothermal extrusion technology can obtain the flux-cored wire blank with stable filling coefficient. .
2. Ingot casting and isothermal extrusion of flux-cored wire
The laminar extrusion method is to compress and deform the aluminum solder ingot containing the active flux in a laminar flow, and the aluminum solder containing no other components is cast into a porous ingot in the form of continuous casting, the outer diameter of the ingot and The inner bore is of constant size, the active flux is filled into the inner bore and compacted.
The compacted solder ingot containing active flux has the following characteristics: the ratio of flux to solder is constant in different cross sections; reinforcing particles (such as SiC) can be added to the active flux to form a composite; the flux is fully coated with solder. .
The key to the laminar extrusion process is the sequential flow of flux and solder. The conditions for sequential flow are the consistency of the rheological properties of the two materials. The rheological properties of the material are related to temperature and compressive stress, and the extrusion temperature and extrusion are adjusted. The pressure can make the rheological properties of two different materials similar, and the well-designed extrusion die shape can make the two materials stably deform in the form of laminar flow.
The isothermal extrusion technique is used in the research process. The flux-cored wire with stable cross-section and uniform filling coefficient can be obtained under specific extrusion temperature and extrusion speed.
3. Flux and wire winding of flux cored wire
Compared with the solid wire, the main features of the internal structure of the cored aluminum wire are as follows: the core is sand-like, viscosity-free, non-plastic, and the deformation and flow of the core are mainly caused by the pressing force generated when the surrounding material is deformed. Friction; wire deformation ability is significantly reduced.
During the drawing process of the flux-cored wire, the deformation of the wire is divided into two parts, one is the plastic deformation of the metal, and the other is the flow and volume compression of the internal powder, and the two deformations interact and influence each other. The plastic deformation ability of the metal determines whether the drawing can be carried out continuously. The rheological behavior and volume compression degree of the core are related to whether the filling curve of the flux-cored wire is stable, thereby affecting the use of the flux-cored wire and the stability of the welding process.
Due to the presence of the core, the effective cross-sectional area of ​​the flux-cored wire is much smaller than that of the solid wire, so the broken wire during the process of drawing the flux-cored wire is common. Optimizing the deformation mode of the wire during the drawing process is an effective way to improve the drawing processability of the core aluminum wire. The roll die drawing technology used in the research improves the wire deformation mode and significantly improves the wire deformation ability.
The flux-cored wire drawn to the finished size is wound into a disk by a layer winding technique.
4 Conclusion
(1) There are four methods for manufacturing the cored aluminum welding wire, and the laminar extrusion method has the most industrial application prospects.
(2) The continuous casting technology can obtain the “Lianhua†ingot with uniform organization and stable composition, and the isothermal extrusion technology can obtain the flux-cored wire blank with stable filling coefficient.
(3) Roller drawing ensures uniform deformation of the core, super-fine scraping technology ensures the cleanliness of the wire, and the layer winding technology ensures the stability of the wire pointing during the welding process.
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