CN112122758A - Ni element-regulated magnetic field-assisted resistance unit welding method for aluminum alloy and steel - Google Patents
Ni element-regulated magnetic field-assisted resistance unit welding method for aluminum alloy and steel Download PDFInfo
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- CN112122758A CN112122758A CN202011003038.6A CN202011003038A CN112122758A CN 112122758 A CN112122758 A CN 112122758A CN 202011003038 A CN202011003038 A CN 202011003038A CN 112122758 A CN112122758 A CN 112122758A
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- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/10—Spot welding; Stitch welding
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- B—PERFORMING OPERATIONS; TRANSPORTING
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Abstract
A Ni element regulated magnetic field assisted resistance unit welding method for aluminum alloy and steel belongs to the technical field of welding. The invention aims to improve the welding performance on the premise of keeping an Al-Si coating on the surface of steel. According to the invention, small holes are prefabricated on the surface of the aluminum alloy, rivets are placed, and a nugget is formed on the interface of the rivets and the steel during welding, so that the connection of the aluminum alloy and the steel is realized. Placing Ni foil at the interface of the rivet and the hot stamping steel, and introducing an alloy element Ni into a molten pool through melting of the foil to increase the stability of austenite and promote the generation of a full martensite structure in the molten pool; meanwhile, the permanent magnet is adopted to generate a constant radial strong magnetic field at the welding position, the flow of Ni element and Al element in the molten pool is promoted through the electromagnetic stirring effect, the uniformity of the structure is improved, the large generation and segregation of ferrite in the molten pool length are inhibited, the solidification behavior of liquid metal is improved, the size of the molten pool is increased, crystal grains are refined, and the defect of air holes is eliminated.
Description
Technical Field
The invention belongs to the technical field of welding; in particular to a Ni element regulated magnetic field assisted resistance unit welding method of aluminum alloy and steel.
Background
In recent years, with the enhancement of environmental protection consciousness of people, energy conservation and emission reduction gradually become the mainstream consciousness of human survival. The vehicle is used as a main walking tool for people to go out, and has a great promotion space in the field of energy conservation and emission reduction. More and more lightweight and strong materials are used in vehicle body manufacturing. The aluminum alloy has the advantages of small density, high strength and the like, and is widely applied to non-main bearing structures such as vehicle body cover plates, vehicle rear covers and the like.
With the continuous maturity of the third generation advanced high-strength steel technology, the hot stamping forming steel represented by 22MnB5 is widely applied to the main bearing structure of the vehicle body due to the superior mechanical property, and the steel is adopted to replace the traditional steel, so that the thickness reduction and the dosage reduction of the used steel can be realized while the service performance is ensured. The formation of large amounts of intermetallic compounds due to excessive reaction between aluminum/steel is likely to cause great difficulty in metallurgical bonding between aluminum/steel, and the weldability between hot press formed steel and aluminum alloy is even worse. This is because the hot stamping steel needs to be quenched during the preparation process, and an Al-Si plating layer needs to be preformed on the steel surface in order to protect the steel surface from severe oxidation and decarburization. The coating is changed into a brittle and hard Fe-Al-Si three-phase intermetallic compound in the quenching process, and the weldability between aluminum and hot stamping steel is further reduced. The Al-Si coating on the hot stamped steel surface not only reduces the weldability between aluminum/steel, but also has a detrimental effect on the metallurgical bond between steel and steel. Al elements in the coating are easy to be partially gathered at a fusion line after being melted into a welding line, and the increase of the Al content in a local area can promote a large amount of generation of welding line ferrite in the solidification process. The bearing performance of ferrite is poor, and compared with a full-martensite structure, the weld structure performance of the ferrite which is generated in large quantity and generates segregation is obviously reduced.
Due to the adverse effect of the Al-Si coating on the surface of the hot stamping formed steel on welding, certain means are required to remove the coating when the steel is applied to welding, which increases the use cost to a certain extent. Therefore, the effective connection of the aluminum alloy and the hot stamping steel becomes a problem which needs to be solved urgently in the vehicle body manufacturing industry.
Disclosure of Invention
The invention aims to provide a magnetic field-assisted aluminum alloy and steel resistance unit welding method which eliminates the performance damage of an Al-Si coating to a welding joint and obtains Ni element regulation and control with good welding performance on the premise of keeping the Al-Si coating.
A Ni-regulated magnetic field assisted resistance cell welding method of aluminum alloys and steels is presented in the present invention, and a brief summary of the method is provided below to provide a basic understanding of some aspects of the invention. It should be understood that the following summary is not an exhaustive overview of the invention. It is not intended to determine the key or critical elements of the present invention, nor is it intended to limit the scope of the present invention.
The invention is realized by the following technical scheme:
a Ni element regulated magnetic field assisted resistance unit welding method for aluminum alloy and steel comprises the following steps:
and 4, putting a Ni foil between the aluminum alloy base material and the steel base material, putting the rivet into a through hole of the aluminum alloy after lap joint, pressing the rivet, the Ni foil and the steel base material, and then performing resistance unit welding by using the electrode tip with the magnet in the step 3.
According to the Ni element-regulated magnetic field-assisted resistance unit welding method for the aluminum alloy and the steel, in the step 1, the through hole is formed in the center of the lap joint area of the aluminum alloy base material, the diameter of the through hole is the same as that of the rivet, and the length of the rivet column is the same as that of the thickness of the aluminum alloy base material.
According to the Ni element-regulated magnetic field-assisted resistance unit welding method for the aluminum alloy and the steel, in the step 1, the thickness of an aluminum alloy base material is 0.5-3 mm, the thickness of a steel base material is 1-5 mm, the thickness of a Ni foil is 0.05-0.5 mm, and the diameter of the Ni foil is the same as the diameter of a through hole.
According to the Ni element regulated magnetic field assisted resistance unit welding method for the aluminum alloy and the steel, the diameter of the through hole is 1-20 mm.
According to the Ni element-regulated magnetic field-assisted resistance unit welding method for the aluminum alloy and the steel, in the step 1, the steel base material is hot stamping formed steel, an Al-Si coating is plated on the surface of the steel base material, and the thickness of the Al-Si coating is 10-80 mu m.
According to the Ni element-regulated magnetic field-assisted resistance unit welding method for the aluminum alloy and the steel, in the step 2, deoiling cleaning is ultrasonic cleaning in an acetone solvent for 1-2 min.
According to the Ni element regulated magnetic field assisted resistance unit welding method for the aluminum alloy and the steel, in the step 3, the resistance spot welding machine is one of a direct current spot welding machine or an alternating current spot welding machine, and 2 magnets are fixed on 2 electrode heads of the resistance spot welding machine.
According to the Ni element-regulated magnetic field-assisted resistance unit welding method for the aluminum alloy and the steel, the magnet in the step 3 is a permanent magnet, the permanent magnet is vertically fixed with the electrode tip, and the working distance between the bottom surface of the permanent magnet and the welding end of the electrode tip fixed with the permanent magnet is 5-15 mm.
According to the Ni element-regulated magnetic field-assisted resistance unit welding method for the aluminum alloy and the steel, distances from upper and lower magnetic poles to a welding plane are adjusted to be consistent, and when the thicknesses of aluminum and steel plates are different, the distances from magnets to the welding plane are ensured to be the same by adjusting the working distance.
According to the Ni element regulated magnetic field assisted resistance unit welding method for the aluminum alloy and the steel, the working distances between the 2 magnets and the welding ends of the fixed electrode tips in the step 3 are the same, and the like magnetic poles of the 2 magnets are oppositely arranged.
The invention relates to a Ni element regulated magnetic field assisted resistance unit welding method of aluminum alloy and steel.
According to the Ni element-regulated magnetic field-assisted resistance unit welding method for the aluminum alloy and the steel, welding parameters of resistance unit welding in the step 4 are electrode pressure of 2-5 kN, welding current of 5-15 kA, pressurizing time of 800-1200 ms and welding time of 200-500 ms.
According to the Ni element regulated and controlled magnetic field assisted resistance unit welding method for the aluminum alloy and the steel, the rivet in the step 1 is made of steel.
According to the Ni element regulated magnetic field assisted resistance unit welding method for the aluminum alloy and the steel, the annular magnets positioned on the two sides of the upper electrode and the lower electrode are coaxially arranged, and like magnetic poles are oppositely arranged, so that components in the vertical direction on a welding plane are mutually offset, components in the horizontal direction are mutually superposed, and a stable radial magnetic field is formed in a molten pool.
The invention relates to a Ni element regulated magnetic field assisted resistance unit welding method for aluminum alloy and steel, which adopts a resistance unit welding technology, a through hole is prefabricated on the surface of the aluminum alloy, a rivet is inserted, and a nugget is formed between the rivet and the steel to realize the welding of the aluminum alloy and the steel.
According to the Ni element regulated magnetic field assisted resistance unit welding method for the aluminum alloy and the steel, the connection of the aluminum/hot stamping forming steel is realized through the introduction of the alloy element Ni and the auxiliary action of the external magnetic field, wherein the introduction of the alloy element Ni increases the stability of austenite, inhibits the generation and segregation of ferrite, and neutralizes the adverse effect of Al element on the structure and performance of a welding seam. The introduction of the external magnetic field promotes the flow of liquid phase in the molten pool, and effectively increases the uniformity of weld joint structures and elements. In addition, the magnetic field acts on the molten pool metal to improve the solidification behavior of the internal structure of the molten pool, refine crystal grains and eliminate the defects of welding cracks, air holes and the like. The overall performance of the joint is enhanced to meet the actual production needs.
The invention has the beneficial effects that:
according to the Ni element-regulated magnetic field-assisted resistance unit welding method for the aluminum alloy and the steel, the connection of aluminum/steel dissimilar materials is ingeniously changed into the connection of the same material between the rivet and the steel through the resistance unit welding method, so that the problem of generation of brittle intermetallic compounds caused by excessive reaction between Fe and Al is avoided to the greatest extent; the Ni element is an austenite stabilizing element, and after the Ni element is added, the stability of austenite generated in the solidification process of liquid metal is increased, the stable existence of the austenite leads a weld joint structure to be more easily transformed into a full martensite structure with good performance at a certain cooling speed, the generation and segregation of ferrite are inhibited, and the adverse effects of the Al element on the weld joint structure and the performance are neutralized. The introduction of the external magnetic field promotes the liquid phase flow in the molten pool, wherein Al element is more uniformly distributed in the molten pool under the action of violent stirring brought by the external magnetic field, the possibility of segregation at the position of a fusion line is reduced, and the dispersion degree of the distribution of alloy elements in the molten pool is improved. In addition, the magnetic field acts on the molten pool metal to improve the solidification behavior of the internal structure of the molten pool, refine crystal grains and eliminate the defects of welding cracks, air holes and the like. The adverse effect caused by the Al-Si coating on the surface of the hot stamping forming steel is effectively reduced through the alloy element-magnetic field auxiliary co-regulation and control effect, high-quality welding with the coating can be realized, the use cost of the 22MnB5 steel is reduced, and the production efficiency is improved.
According to the Ni element-regulated magnetic field-assisted resistance unit welding method for the aluminum alloy and the steel, the maximum bearing capacity can be improved by 20% -50% by performing a tensile test on a welding joint.
Drawings
FIG. 1 is a schematic view of an assembly structure of a Ni element regulated and controlled magnetic field assisted resistance unit welding method for aluminum alloy and steel in preparation for welding according to the present invention;
FIG. 2 is a schematic diagram of a welding process of the Ni element regulated magnetic field assisted resistance unit welding method of aluminum alloy and steel according to the present invention;
FIG. 3 is a schematic view of the magnetic field distribution of the Ni element regulated magnetic field assisted aluminum alloy and steel resistance unit welding method of the present invention;
FIG. 4 is a schematic diagram of the direction of a welding plane external magnetic field of the Ni element regulated magnetic field assisted aluminum alloy and steel resistance unit welding method of the present invention;
FIG. 5 shows the current and voltage waveforms of the AC input to the AC spot welder according to the Ni element regulated and controlled magnetic field assisted welding method for the resistance units of aluminum alloy and steel;
FIG. 6 is a photograph of the joint structure of the aluminum alloy/hot stamp formed steel electrical resistance cell welding method made by the method of one embodiment;
FIG. 7 is a photograph of the joint structure morphology of the aluminum alloy/hot stamp formed steel resistance cell welding method prepared by the comparative example method;
in fig. 1, 1 is an aluminum alloy base material, 2 is a steel base material, 3 is a rivet, 4 is a Ni foil, 5 is an electrode tip, and 6 is a magnet.
Detailed Description
The first embodiment is as follows:
a Ni element regulated magnetic field assisted resistance unit welding method for aluminum alloy and steel comprises the following steps:
and 4, putting a Ni foil between the aluminum alloy base material and the steel base material, putting the rivet into a through hole of the aluminum alloy after lap joint, pressing the rivet, the Ni foil and the steel base material, and then performing resistance unit welding by using the electrode tip with the magnet in the step 3.
In the method for welding the Ni element-regulated magnetic field-assisted aluminum alloy and steel resistance units, in the step 1, the through hole is formed in the center of the lap joint area of the aluminum alloy base material, the diameter of the through hole is the same as the diameter of the rivet, and the length of the rivet column is the same as the thickness of the aluminum alloy base material.
In the method for welding the Ni-element-regulated magnetic-field-assisted aluminum alloy and steel resistance units according to the embodiment, in step 1, the thickness of an aluminum alloy base material is 1.5mm, the thickness of a steel base material is 1.5mm, the thickness of a Ni foil is 0.1mm, and the diameter of the Ni foil is the same as the diameter of a through hole.
In the method for welding the Ni-element-regulated magnetic-field-assisted aluminum alloy and steel resistance units according to the embodiment, the aluminum alloy base material in the step 1 is a 60601-T6 aluminum alloy plate, and the diameter of the circular through hole is 5 mm.
In the resistance unit welding method of the Ni-element-regulated magnetic-field-assisted aluminum alloy and the steel according to the embodiment, in step 1, the steel base material is 22MnB5 hot-stamping steel, the surface of the steel base material is plated with an Al-Si plating layer, and the thickness of the Al-Si plating layer is 40 μm.
In the method for welding the Ni element-regulated magnetic field-assisted aluminum alloy and steel resistance units, in the step 2, degreasing and cleaning are ultrasonic cleaning in an acetone solvent for 1 min.
In the method for welding the resistance unit of the magnetic field-assisted aluminum alloy and steel regulated and controlled by the Ni element according to the embodiment, the resistance spot welder in the step 3 is an alternating current spot welder, and 2 magnets are fixed on 2 electrode heads of the resistance spot welder.
In the method for welding the Ni-element-regulated magnetic-field-assisted aluminum alloy and steel resistance units according to the embodiment, the magnet in the step 3 is a permanent magnet, the permanent magnet is vertically fixed to the electrode tip, and the working distance between the bottom surface of the permanent magnet and the welding end of the electrode tip fixed to the permanent magnet is 10 mm.
In the method for welding the Ni-regulated magnetic field-assisted aluminum alloy and steel resistance units according to this embodiment, in step 3, the working distances between the 2 magnets and the welding ends of the fixed electrode tips thereof are the same, and the like magnetic poles of the 2 magnets are arranged oppositely.
In the method for welding a Ni-controlled magnetic field-assisted aluminum alloy and steel resistance element according to the present embodiment, the permanent magnet is an NdFeB magnet.
In the method for welding the resistance unit of the magnetic field-assisted aluminum alloy and steel regulated and controlled by the Ni element in the embodiment, welding parameters of welding of the resistance unit in the step 4 are electrode pressure 5kN, welding current 10kA, pressurization time 1000ms and welding time 200 ms.
In the resistance unit welding method of magnetic field-assisted aluminum alloy and steel regulated and controlled by Ni element according to the embodiment, the specification of the designed steel base material and aluminum alloy base material to be welded is 25 × 100mm, the lap joint size is 25 × 25mm, and the position of the through hole is the center of the square lap joint area; the Ni foil is placed at the interface of the rivet and the hot stamping steel, and the shape of the Ni foil is the same as the cross section of the rivet.
In the method for welding the Ni-regulated magnetic field-assisted aluminum alloy and steel resistance units according to the embodiment, the ring magnets on the two sides of the upper and lower electrodes are coaxially arranged, and the like magnetic poles are oppositely arranged, so that components in the vertical direction on the welding plane are offset, components in the horizontal direction are superposed, and a stable radial magnetic field is formed in the molten pool. The schematic view of the magnetic field distribution of the Ni element-regulated magnetic field-assisted aluminum alloy and steel resistance unit welding method is shown in fig. 3, and the schematic view of the welding plane external magnetic field direction of the Ni element-regulated magnetic field-assisted aluminum alloy and steel resistance unit welding method is shown in fig. 4.
In the method for welding the resistance units of the magnetic field-assisted aluminum alloy and the steel by adjusting the Ni element according to the present embodiment, the current and voltage waveforms of the input ac power of the ac spot welder are as shown in fig. 5, and when the ac spot welder is used, although the current changes in one period, the charged particles still move in one direction.
In the method for welding the resistance unit of the magnetic-field-assisted aluminum alloy and the steel by adjusting and controlling the Ni element, the structural morphology picture of the prepared aluminum alloy/hot-stamping steel resistance unit welding head is shown in fig. 6, as can be seen from fig. 6, the interface is well formed, no obvious pore defects exist, the shape of a molten pool is flattened under the combined action of the alloy element and the magnetic field assistance, and the structure distribution in the nugget is fine and uniform and is a martensite structure. The joint strength is tested, the sample is in a button fracture mode, the maximum bearing capacity is 5980N, and the maximum bearing capacity is improved by 20% compared with that of a comparative example.
The structural morphology photograph of the resistance unit welding head of the comparative example is shown in fig. 7, the comparative example is consistent with the specifications of the base material and the rivet selected in the embodiment, the selected welding parameters are consistent, and in the welding process, no Ni foil is added and no magnetic field is added for assistance, so that as can be seen from fig. 7, the nugget size of the comparative example is smaller, white ferrite structure precipitation exists at the nugget boundary, and the grain size in the nugget is increased. And (3) carrying out a tensile test on the joint, wherein the sample is broken along the interface of the rivet and the hot stamping steel, and the maximum bearing capacity is 4980N.
The second embodiment is as follows:
a Ni element regulated magnetic field assisted resistance unit welding method for aluminum alloy and steel comprises the following steps:
and 4, putting a Ni foil between the aluminum alloy base material and the steel base material, putting the rivet into a through hole of the aluminum alloy after lap joint, pressing the rivet, the Ni foil and the steel base material, and then performing resistance unit welding by using the electrode tip with the magnet in the step 3.
In the method for welding the Ni element-regulated magnetic field-assisted aluminum alloy and steel resistance units, in the step 1, the through hole is formed in the center of the lap joint area of the aluminum alloy base material, the diameter of the through hole is the same as the diameter of the rivet, and the length of the rivet column is the same as the thickness of the aluminum alloy base material.
In the method for welding the Ni-element-regulated magnetic-field-assisted aluminum alloy and steel resistance units according to the embodiment, in step 1, the thickness of an aluminum alloy base material is 2mm, the thickness of a steel base material is 1mm, the thickness of a Ni foil is 0.2mm, and the diameter of the Ni foil is the same as the diameter of a through hole.
In the method for welding the Ni-controlled magnetic field-assisted aluminum alloy and the steel with the resistance unit according to the embodiment, in step 1, the steel base material is hot-stamped steel, the surface of the steel base material is plated with an Al-Si coating, and the thickness of the Al-Si coating is 30 μm.
In the method for welding the Ni element-regulated magnetic field-assisted aluminum alloy and steel resistance units, in the step 2, degreasing and cleaning are ultrasonic cleaning in an acetone solvent for 1 min.
In the method for welding the resistance unit of the magnetic field-assisted aluminum alloy and steel regulated and controlled by the Ni element according to the embodiment, the resistance spot welder in the step 3 is a direct current spot welder, and 2 magnets are fixed on 2 electrode heads of the resistance spot welder.
In the method for welding the Ni-element-regulated magnetic-field-assisted aluminum alloy and steel resistance units according to the embodiment, the magnet in the step 3 is a permanent magnet, the permanent magnet is vertically fixed to the electrode tip, and the working distance between the bottom surface of the permanent magnet and the welding end of the electrode tip fixed to the permanent magnet is 15 mm.
In the method for welding the Ni-regulated magnetic field-assisted aluminum alloy and steel resistance units according to this embodiment, in step 3, the working distances between the 2 magnets and the welding ends of the fixed electrode tips thereof are the same, and the like magnetic poles of the 2 magnets are arranged oppositely.
In the method for welding a Ni-controlled magnetic field-assisted aluminum alloy and steel resistance element according to the present embodiment, the permanent magnet is an NdFeB magnet.
In the method for welding the resistance unit of the magnetic field-assisted aluminum alloy and steel regulated and controlled by the Ni element in the embodiment, welding parameters of welding of the resistance unit in the step 4 are electrode pressure 2kN, welding current 15kA, pressurization time 800ms, and welding time 300 ms.
According to the resistance unit welding method of the magnetic field-assisted aluminum alloy and the steel regulated and controlled by the Ni element, the welding joint interface of the prepared aluminum alloy/hot stamping steel resistance unit is well formed, no obvious pore defect exists, the shape of a molten pool is flattened under the combined action of the alloy element and the magnetic field assistance, and the texture distribution in a molten core is fine and uniform and is a martensite texture. The strength of the joint is tested, the sample is in a button fracture mode, and the maximum bearing capacity is improved by 25% compared with that of a unit welding joint without the addition of a Ni foil and the assistance of a magnetic field.
The third concrete implementation mode:
a Ni element regulated magnetic field assisted resistance unit welding method for aluminum alloy and steel comprises the following steps:
and 4, putting a Ni foil between the aluminum alloy base material and the steel base material, putting the rivet into a through hole of the aluminum alloy after lap joint, pressing the rivet, the Ni foil and the steel base material, and then performing resistance unit welding by using the electrode tip with the magnet in the step 3.
In the method for welding the Ni element-regulated magnetic field-assisted aluminum alloy and steel resistance units, in the step 1, the through hole is formed in the center of the lap joint area of the aluminum alloy base material, the diameter of the through hole is the same as the diameter of the rivet, and the length of the rivet column is the same as the thickness of the aluminum alloy base material.
In the method for welding the Ni-element-regulated magnetic-field-assisted aluminum alloy and steel resistance units according to the embodiment, in step 1, the thickness of an aluminum alloy base material is 3mm, the thickness of a steel base material is 5mm, the thickness of a Ni foil is 0.5mm, and the diameter of the Ni foil is the same as the diameter of a through hole.
In the method for welding the Ni-controlled magnetic field-assisted aluminum alloy and the steel with the resistance unit according to the embodiment, in step 1, the steel base material is hot-stamped steel, the surface of the steel base material is plated with an Al-Si coating, and the thickness of the Al-Si coating is 80 μm.
In the method for welding the Ni element-regulated magnetic field-assisted aluminum alloy and steel resistance units, in the step 2, degreasing cleaning is ultrasonic cleaning in an acetone solvent for 2 min.
In the method for welding the resistance unit of the magnetic field-assisted aluminum alloy and steel regulated and controlled by the Ni element according to the embodiment, the resistance spot welder in the step 3 is an alternating current spot welder, and 2 magnets are fixed on 2 electrode heads of the resistance spot welder.
In the method for welding the Ni-element-regulated magnetic-field-assisted aluminum alloy and steel resistance units according to the embodiment, the magnet in the step 3 is a permanent magnet, the permanent magnet is vertically fixed to the electrode tip, and the working distance between the bottom surface of the permanent magnet and the welding end of the electrode tip fixed to the permanent magnet is 5 mm.
In the method for welding the Ni-regulated magnetic field-assisted aluminum alloy and steel resistance units according to this embodiment, in step 3, the working distances between the 2 magnets and the welding ends of the fixed electrode tips thereof are the same, and the like magnetic poles of the 2 magnets are arranged oppositely.
In the method for welding a Ni-controlled magnetic field-assisted aluminum alloy and steel resistance element according to the present embodiment, the permanent magnet is an NdFeB magnet.
In the method for welding the resistance unit of the magnetic field-assisted aluminum alloy and steel regulated and controlled by the Ni element in the embodiment, welding parameters of welding of the resistance unit in the step 4 are electrode pressure of 5kN, welding current of 15kA, pressurization time of 1200ms, and welding time of 500 ms.
According to the resistance unit welding method of the magnetic field-assisted aluminum alloy and the steel regulated and controlled by the Ni element, the welding joint interface of the prepared aluminum alloy/hot stamping steel resistance unit is well formed, no obvious pore defect exists, the shape of a molten pool is flattened under the combined action of the alloy element and the magnetic field assistance, and the texture distribution in a molten core is fine and uniform and is a martensite texture. The strength of the joint is tested, the sample is in a button fracture mode, and the maximum bearing capacity is improved by 15% compared with a unit welding joint without the addition of Ni foil and magnetic field assistance.
The fourth concrete implementation mode:
a Ni element regulated magnetic field assisted resistance unit welding method for aluminum alloy and steel comprises the following steps:
and 4, putting a Ni foil between the aluminum alloy base material and the steel base material, putting the rivet into a through hole of the aluminum alloy after lap joint, pressing the rivet, the Ni foil and the steel base material, and then performing resistance unit welding by using the electrode tip with the magnet in the step 3.
In the method for welding the Ni element-regulated magnetic field-assisted aluminum alloy and steel resistance units, in the step 1, the through hole is formed in the center of the lap joint area of the aluminum alloy base material, the diameter of the through hole is the same as the diameter of the rivet, and the length of the rivet column is the same as the thickness of the aluminum alloy base material.
In the method for welding the Ni-element-regulated magnetic-field-assisted aluminum alloy and steel resistance units according to the embodiment, in step 1, the thickness of an aluminum alloy base material is 0.5mm, the thickness of a steel base material is 1mm, the thickness of a Ni foil is 0.05mm, and the diameter of the Ni foil is the same as the diameter of a through hole.
In the method for welding the Ni-controlled magnetic field-assisted aluminum alloy and the steel with the resistance unit according to the embodiment, in step 1, the steel base material is hot-stamped steel, the surface of the steel base material is plated with an Al-Si coating, and the thickness of the Al-Si coating is 10 μm.
In the method for welding the Ni element-regulated magnetic field-assisted aluminum alloy and steel resistance units, in the step 2, degreasing and cleaning are ultrasonic cleaning in an acetone solvent for 1 min.
In the method for welding the resistance unit of the magnetic field-assisted aluminum alloy and steel regulated and controlled by the Ni element according to the embodiment, the resistance spot welder in the step 3 is one of a direct current spot welder or an alternating current spot welder, and 2 magnets are fixed on 2 electrode heads of the resistance spot welder.
In the method for welding the Ni-element-regulated magnetic-field-assisted aluminum alloy and steel resistance units according to the embodiment, the magnet in the step 3 is a permanent magnet, the permanent magnet is vertically fixed to the electrode tip, and the working distance between the bottom surface of the permanent magnet and the welding end of the electrode tip fixed to the permanent magnet is 15 mm.
In the method for welding the Ni-regulated magnetic field-assisted aluminum alloy and steel resistance units according to this embodiment, in step 3, the working distances between the 2 magnets and the welding ends of the fixed electrode tips thereof are the same, and the like magnetic poles of the 2 magnets are arranged oppositely.
In the method for welding a Ni-controlled magnetic field-assisted aluminum alloy and steel resistance element according to the present embodiment, the permanent magnet is an NdFeB magnet.
In the method for welding the resistance unit of the magnetic field-assisted aluminum alloy and steel regulated and controlled by the Ni element in the embodiment, welding parameters of welding of the resistance unit in the step 4 are electrode pressure 2kN, welding current 5kA, pressurization time 800ms, and welding time 200 ms.
According to the resistance unit welding method of the magnetic field-assisted aluminum alloy and the steel regulated and controlled by the Ni element, the welding joint interface of the prepared aluminum alloy/hot stamping steel resistance unit is well formed, no obvious pore defect exists, the shape of a molten pool is flattened under the combined action of the alloy element and the magnetic field assistance, and the texture distribution in a molten core is fine and uniform and is a martensite texture. The strength of the joint is tested, the sample is in a button fracture mode, and the maximum bearing capacity is improved by 22% compared with a unit welding joint without the addition of Ni foil and magnetic field assistance.
The fifth concrete implementation mode:
a Ni element regulated magnetic field assisted resistance unit welding method for aluminum alloy and steel comprises the following steps:
and 4, putting a Ni foil between the aluminum alloy base material and the steel base material, putting the rivet into a through hole of the aluminum alloy after lap joint, pressing the rivet, the Ni foil and the steel base material, and then performing resistance unit welding by using the electrode tip with the magnet in the step 3.
In the method for welding the Ni-regulated magnetic field-assisted aluminum alloy and steel resistance units according to the embodiment, the ring magnets on the two sides of the upper and lower electrodes are coaxially arranged, and the like magnetic poles are oppositely arranged, so that components in the vertical direction on the welding plane are offset, components in the horizontal direction are superposed, and a stable radial magnetic field is formed in the molten pool.
According to the resistance unit welding method for the magnetic field-assisted aluminum alloy and the steel regulated and controlled by the Ni element, the resistance unit welding technology is adopted, the through hole is prefabricated in the surface of the aluminum alloy, the rivet is inserted, and the nugget is formed between the rivet and the steel, so that the aluminum alloy and the steel are welded.
According to the Ni element-regulated magnetic field-assisted aluminum alloy and steel resistance unit welding method, the connection of aluminum/hot-stamped formed steel is realized through the introduction of the alloy element Ni and the auxiliary action of an external magnetic field, wherein the introduction of the alloy element Ni increases the stability of austenite, inhibits the generation and segregation of ferrite, and neutralizes the adverse effect of Al element on the structure and performance of a weld joint. The introduction of the external magnetic field promotes the flow of liquid phase in the molten pool, and effectively increases the uniformity of weld joint structures and elements. In addition, the magnetic field acts on the molten pool metal to improve the solidification behavior of the internal structure of the molten pool, refine crystal grains and eliminate the defects of welding cracks, air holes and the like. The overall performance of the joint is enhanced to meet the actual production needs.
The sixth specific implementation mode:
according to the fifth specific embodiment, in the step 1, the through hole is formed in the center of the overlapping area of the aluminum alloy base material, the diameter of the through hole is the same as the diameter of the rivet, and the length of the rivet column is the same as the thickness of the aluminum alloy base material.
The seventh embodiment:
according to the fifth specific embodiment, in the step 1, the thickness of the aluminum alloy base material is 0.5-3 mm, the thickness of the steel base material is 1-5 mm, the thickness of the Ni foil is 0.05-0.5 mm, and the diameter of the Ni foil is the same as the diameter of the through hole.
The specific implementation mode is eight:
according to the fifth specific embodiment, in the step 1, the steel base material is hot-stamping formed steel, the surface of the steel base material is plated with an Al-Si coating, and the thickness of the Al-Si coating is 10 to 80 μm.
The specific implementation method nine:
according to the resistance unit welding method of the magnetic field-assisted aluminum alloy and steel regulated and controlled by the Ni element in the fifth embodiment, in the step 2, deoiling cleaning is ultrasonic cleaning in an acetone solvent for 1-2 min.
The detailed implementation mode is ten:
according to the fifth specific embodiment of the method for welding the Ni-regulated magnetic field-assisted aluminum alloy and steel resistance units, in the step 3, the resistance spot welder is one of a direct current spot welder and an alternating current spot welder, and 2 magnets are fixed on 2 electrode heads of the resistance spot welder.
The concrete implementation mode eleven:
according to the fifth specific embodiment, in the resistance unit welding method of the Ni-element-regulated magnetic field-assisted aluminum alloy and steel, the magnet in the step 3 is a permanent magnet, the permanent magnet is vertically fixed to the electrode tip, and the working distance between the bottom surface of the permanent magnet and the welding end of the electrode tip fixed to the permanent magnet is 5-15 mm.
The specific implementation mode twelve:
according to the fifth specific embodiment of the method for welding the Ni-regulated magnetic field-assisted aluminum alloy and steel resistance units, in the step 3, the working distances between the 2 magnets and the welding ends of the fixed electrode tips thereof are the same, and the like magnetic poles of the 2 magnets are oppositely arranged.
The specific implementation mode is thirteen:
according to the fifth specific embodiment, the Ni-controlled magnetic field-assisted resistance element welding method for aluminum alloy and steel is performed, and the permanent magnet is an NdFeB magnet.
The specific implementation mode is fourteen:
according to the fifth specific embodiment, in the resistance unit welding method of the magnetic field-assisted aluminum alloy and steel regulated and controlled by the Ni element, welding parameters of resistance unit welding in the step 4 are electrode pressure of 2-5 kN, welding current of 5-15 kA, pressurization time of 800-1200 ms, and welding time of 200-500 ms.
Although the embodiments of the present invention have been described above, the contents thereof are merely embodiments adopted to facilitate understanding of the technical aspects of the present invention, and are not intended to limit the present invention. It will be apparent to persons skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A Ni element regulated magnetic field assisted resistance unit welding method for aluminum alloy and steel is characterized in that: the method comprises the following steps:
step 1, preparing a steel base material, an aluminum alloy base material, a rivet and a Ni foil piece to be welded, and enabling a through hole to be formed in the surface of the aluminum alloy base material to be welded for later use;
step 2, deoiling and cleaning a steel base material to be welded, an aluminum alloy base material after the through hole, a rivet and a Ni foil, and then air-drying for later use;
step 3, fixing the magnet on an electrode head of the resistance spot welding machine for standby;
and 4, putting a Ni foil between the aluminum alloy base material and the steel base material, putting the rivet into a through hole of the aluminum alloy after lap joint, pressing the rivet, the Ni foil and the steel base material, and then performing resistance unit welding by using the electrode tip with the magnet in the step 3.
2. The Ni element regulated and controlled magnetic field assisted resistance unit welding method of aluminum alloy and steel according to claim 1, characterized in that: in the step 1, the through hole is arranged in the center of the lap joint area of the aluminum alloy base material, the diameter of the through hole is the same as the diameter of the rivet, and the length of the rivet column is the same as the thickness of the aluminum alloy base material.
3. The Ni element regulated magnetic field assisted resistance unit welding method of aluminum alloy and steel according to claim 2, wherein: in the step 1, the thickness of the aluminum alloy base material is 0.5-3 mm, the thickness of the steel base material is 1-5 mm, the thickness of the Ni foil piece is 0.05-0.5 mm, and the diameter of the Ni foil piece is the same as the diameter of the through hole.
4. The Ni element-regulated magnetic field-assisted resistance unit welding method of aluminum alloy and steel according to claim 3, wherein the Ni element-regulated magnetic field-assisted resistance unit welding method comprises the following steps: in the step 1, the steel base material is hot stamping formed steel, an Al-Si coating is plated on the surface of the steel base material, and the thickness of the Al-Si coating is 10-80 mu m.
5. The Ni element regulated magnetic field assisted resistance unit welding method of aluminum alloy and steel according to claim 1 or 4, wherein: and in the step 2, deoiling cleaning is ultrasonic cleaning in an acetone solvent for 1-2 min.
6. The Ni element-regulated magnetic field-assisted resistance unit welding method of aluminum alloy and steel according to claim 5, wherein the Ni element-regulated magnetic field-assisted resistance unit welding method comprises the following steps: and 3, fixing the 2 magnets on the 2 electrode heads of the resistance spot welding machine, wherein the resistance spot welding machine is one of a direct current spot welding machine or an alternating current spot welding machine.
7. The Ni element-regulated magnetic field-assisted resistance unit welding method of aluminum alloy and steel according to claim 6, wherein: and 3, the magnet is a permanent magnet, the permanent magnet is vertically fixed with the electrode tip, and the working distance between the bottom surface of the permanent magnet and the welding end of the electrode tip fixed with the permanent magnet is 5-15 mm.
8. The Ni element-regulated magnetic field-assisted resistance unit welding method of aluminum alloy and steel according to claim 7, wherein: and 3, working distances between the 2 magnets and the welding ends of the electrode tips fixed by the magnets are the same, and the homonymous magnetic poles of the 2 magnets are oppositely placed.
9. The Ni element-regulated magnetic field-assisted resistance unit welding method of aluminum alloy and steel according to claim 7, wherein: the permanent magnet is an NdFeB magnet.
10. The Ni element-regulated magnetic field-assisted resistance unit welding method of aluminum alloy and steel according to claim 7, wherein: in the step 4, welding parameters of the resistance unit welding are 2-5 kN of electrode pressure, 5-15 kA of welding current, 800-1200 ms of pressurizing time and 200-500 ms of welding time.
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