CN113478060A - Double-phase steel resistance spot welding method - Google Patents
Double-phase steel resistance spot welding method Download PDFInfo
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- CN113478060A CN113478060A CN202110766109.6A CN202110766109A CN113478060A CN 113478060 A CN113478060 A CN 113478060A CN 202110766109 A CN202110766109 A CN 202110766109A CN 113478060 A CN113478060 A CN 113478060A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- 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
- B23K11/11—Spot welding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- 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
- B23K11/34—Preliminary treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- 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
- B23K11/36—Auxiliary equipment
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/06—Surface hardening
- C21D1/09—Surface hardening by direct application of electrical or wave energy; by particle radiation
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints
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- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Resistance Welding (AREA)
Abstract
The invention discloses a resistance spot welding method for dual-phase steel, which comprises the following steps: s1, overlapping two steel plates to be welded on the welding platform, wherein the overlapping length direction of the two steel plates to be welded is the rolling direction, and S2 welding the two steel plates to be welded through a spot welding machine, wherein the welding point is the overlapping central point of the two steel plates to be welded; s3, pre-pressing the two steel plates to be welded for 100 ms; s4, adjusting the welding pulse current from small to large, welding the two steel plates to be welded, and tempering after welding; s5, performing tensile shear performance test and nugget diameter measurement on the two steel plates welded together in the step S4; and S6, repeating the steps S3 to S5 for a plurality of times under the condition of the same welding process parameters until welding spatters appear. The welding method is simple and does not need other auxiliary equipment, such as an intermediate layer or a backing plate. The tempering pulse adopts a single pulse mode, so that the welding process time is shortened and the energy consumption is further reduced.
Description
Technical Field
The invention relates to the technical field of electric welding, in particular to a resistance spot welding method for dual-phase steel.
Background
In order to meet increasingly stringent environmental regulations, automobile manufacturers are striving to reduce the weight of automobiles because the lighter the body, the lower the fuel consumption and gas emissions. Among them, advanced high strength steels possess excellent strength and weight ratio, which is driving the advanced high strength steels to gradually replace traditional carbon steels under lighter body weight requirements. Advanced high strength steels, such as dual phase steels, complex phase steels, transformation induced plasticity steels, and quench portioned steels, have been widely used in the automotive industry. In the manufacturing of automobile bodies, welding parts including underbody, side walls, frames, automobile body assemblies and the like are welded, a large number of resistance spot welding processes are adopted in the welding process, thousands of spot welding processes are adopted on the automobile bodies, and the performance of the spot welding processes can affect the durability and the collision resistance of the automobiles, so the resistance spot welding performance of the advanced high-strength steel is particularly important, and the defects of welding cracks, shrinkage cavities, splashing and the like can all have adverse effects on the mechanical performance of a spot welding head. The plastic temperature range of the advanced high-strength steel is narrow in the welding process, and compared with the traditional low-carbon steel, the plastic temperature range needs larger electrode pressure for obtaining the same plastic deformation, so that the welding window is narrowed, the process is difficult to control, and welding defects are easy to occur to influence the welding performance.
The advanced high-strength steel has high carbon equivalent, the structure of the molten core area is basically martensite after rapid cooling, the hardness is very high, and in a tensile shear test, the higher yield strength of the material can generate larger stress concentration at the edge of a spot welding joint, so that complete button fracture is not easy to occur, and therefore, an interface or partial interface fracture mode can be more easily generated in the process of testing the mechanical property of a welding spot. For advanced high strength steels, i.e. where this type of fracture mode occurs, the weld strength for the intended application can still be achieved, but is relatively low. The traditional failure mode criterion considers that the nugget diameter is larger than a critical value to ensure that the spot welding joint fails in a complete button fracture mode, the critical value depends only on the thickness of a welded steel plate, but the critical nugget diameter of the advanced high-strength steel not only depends on the thickness of the steel plate, but also depends on the ratio of the hardness of a failure part to the hardness of a welding spot nugget, so that the traditional failure criterion is not enough for evaluating the resistance spot welding performance.
Disclosure of Invention
The invention aims to solve the problems, provides a resistance spot welding method for dual-phase steel, improves the failure mode of advanced high-strength steel, and improves the mechanical property of welding spots, and specifically comprises the following steps:
a resistance spot welding method for dual-phase steel comprises the following steps:
s1, overlapping two steel plates to be welded on the welding platform, wherein the overlapping length direction of the two steel plates to be welded is the rolling direction, and the two steel plates to be welded are made of 800 MPa-grade hot-dip galvanized dual-phase steel;
s2, welding the two steel plates to be welded through a spot welding machine, wherein the welding point is the lap joint central point of the two steel plates to be welded;
s3, pre-pressing the two steel plates to be welded, wherein the pre-pressing time is 100 ms;
s4, adjusting the welding pulse current from small to large, welding the two steel plates to be welded, and tempering after welding;
s5, performing tensile shear performance test and nugget diameter measurement on the two steel plates welded together in the step S4;
and S6, repeating the steps S3 to S5 for a plurality of times under the condition of the same welding process parameters until welding spatters appear.
Preferably, the welding parameters in step S4 are: setting the welding time between 200ms and 400ms, setting the interval time after welding between 500ms and 1000ms, setting the tempering pulse current between 4kA and 6kA, and setting the tempering pulse time between 100ms and 300 ms.
Preferably, the spot welder is a medium frequency direct current resistance spot welder.
Preferably, the electrode tip used by the spot welder is a dome-shaped electrode with an end face diameter of 6mm, and the welding pressure ranges from 3.5kN to 6.5 kN.
Preferably, the steel plates to be welded are two steel plates with the same size, shape, material and thickness, and the contact position of the two steel plates during lapping is square.
Preferably, the two steel plates to be welded have a length of 150mm and a width of 50mm, and form a square of 50mm × 50mm when overlapped.
Preferably, the tensile shear performance test is carried out on an electronic universal testing machine, and the displacement rate of the electronic universal testing machine is 5mm/min to 10 mm/min.
Preferably, the tempering treatment is in a single pulse mode.
Has the advantages that: the welding method is simple and does not need other auxiliary equipment, such as an intermediate layer or a backing plate. The tempering pulse adopts a single pulse mode, so that the welding process time is shortened and the energy consumption is further reduced. The method has different material thicknesses, adopts a single pulse mode to adjust welding heat input by adjusting tempering pulse time and tempering pulse current, and regulates and controls the softening degree of a heat affected zone. The method can obviously improve the tensile-shear strength of the spot-welded joint, improve the plasticity and toughness of the spot-welded joint, reduce the brittleness and hardness tendency, and increase the absorption energy of the spot-welded joint, so that the welding process window of the 800 MPa-grade hot-galvanized dual-phase steel resistance spot welding is widened, the tempering pulse is increased to further reduce the welding defects, the initial nugget is formed by the welding pulse, the final nugget size is further increased by combining the tempering pulse, the mechanical property is improved, in addition, the nugget size is further increased by combining the tempering pulse, and the splashing caused by overlarge welding current in the welding pulse process is avoided.
Drawings
FIG. 1 is a schematic view of a welding process according to an embodiment of the present invention;
FIG. 2 illustrates an embodiment of the present invention.
Wherein the relevant data in fig. 1 are interpreted as:
I1: welding pulses; i is2: tempering pulse; t is t0: time t of pre-pressing1: welding time; t is t2: spacing after welding; t is t3: the pulse time; t is t4: the pressing time is continued.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It is noted that the terms first, second, third, etc. are used herein to describe various components or features, but these components or features are not limited by these terms. These terms are only used to distinguish one element or part from another element or part. Terms such as "first," "second," and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. For convenience of description, spatially relative terms such as "inner", "outer", "upper", "lower", "left", "right", "upper", "left", "right", and the like are used herein to describe the orientation relation of the components or parts in the present embodiment, but these spatially relative terms do not limit the orientation of the technical features in practical use.
The invention provides a dual-phase steel resistance spot welding method for changing the fracture mode of a spot welding joint and improving the mechanical property of the spot welding joint, and tests prove that the tensile-shear strength of the spot welding joint obtained by using the method is greatly improved, the ductility and toughness are improved, the brittleness and hardness tendency is reduced, the absorption energy of the spot welding joint is increased, the welding process window is widened, meanwhile, the spot welding joint which is completely in a button fracture mode can be obtained under specific welding process parameters, and the performance level of the spot welding joint is effectively improved, and the method specifically comprises the following steps:
a resistance spot welding method for dual-phase steel comprises the following steps:
s1, overlapping two steel plates to be welded on the welding platform, wherein the overlapping length direction of the two steel plates to be welded is the rolling direction, and the two steel plates to be welded are made of 800 MPa-grade hot-dip galvanized dual-phase steel.
First, as shown in fig. 2, a preferred overlapping manner is as follows: the steel plates to be welded are two steel plates with the same size, shape, material and thickness, the contact positions of the two steel plates during lapping are square, namely the two rectangular steel plates with the same size and thickness are lapped, one of the two rectangular steel plates is placed on the other rectangular steel plate but the two rectangular steel plates are not completely overlapped, the other two steel plates form a straight line, only part of the two steel plates are overlapped, specifically, as shown in a lapping mode shown in figure 2, the overlapped part is limited, the overlapped part needs to form a square, namely, the overlapped length is equal to the width of the rectangular steel plate.
For example, one way of overlapping: the length of the two steel plates to be welded is 150mm, the width of the two steel plates to be welded is 50mm, and a square of 50mm multiplied by 50mm is formed during overlapping. The 50mm × 50mm square is the shape and area of the overlapping portion.
The specific operation of step S1 is: firstly, two steel plates with the same size, shape, thickness and material are selected for lapping, a lap joint overlapped part forms a square, and the length direction of the whole formed by lapping is the rolling direction. Then, step S2 is performed:
and S2, welding the two steel plates to be welded through a spot welding machine, wherein the welding point is the lap joint central point of the two steel plates to be welded.
The spot welding machine adopted in the method is a medium-frequency direct-current resistance spot welding machine, and the medium-frequency direct-current resistance spot welding machine is used for electrically welding two steel plates with good wearability, wherein the spot welding position is not randomly arranged, in order to ensure that the two steel plates are uniformly contacted, the center of the lap joint part needs to be firstly spot-welded,
and S3, pre-pressing the two steel plates to be welded, wherein the pre-pressing time is 100 ms.
And S4, adjusting the welding pulse current from small to large, welding the two steel plates to be welded, and tempering after welding.
The welding parameters in step S4 are: setting the welding time between 200ms and 400ms, setting the interval time after welding between 500ms and 1000ms, setting the tempering pulse current between 4kA and 6kA, and setting the tempering pulse time between 100ms and 300 ms.
And S5, performing tensile shear performance test and nugget diameter measurement on the two steel plates welded together in the step S4.
And S6, repeating the steps S3 to S5 for a plurality of times under the condition of the same welding process parameters until welding spatters appear.
In a preferred embodiment, the spot welder is a medium frequency direct current resistance spot welder. The electrode tip used by the spot welding machine is a dome-shaped electrode with the end surface diameter of 6mm, and the welding pressure range is between 3.5kN and 6.5 kN. The steel plates to be welded are two steel plates with the same size, shape, material and thickness, and the contact position of the two steel plates in the lapping process is square. The length of the two steel plates to be welded is 150mm, the width of the two steel plates to be welded is 50mm, and a square of 50mm multiplied by 50mm is formed during overlapping. The tensile shear performance test is carried out on an electronic universal testing machine, and the displacement rate of the electronic universal testing machine is 5mm/min to 10 mm/min. The tempering treatment adopts a single pulse mode.
The method has the specific principle that: the invention relates to a resistance spot welding method, which uses a medium-frequency direct-current resistance spot welding machine to weld, wherein an electrode is a dome-shaped electrode with the end surface diameter of 6mm and is made of chromium, zirconium and copper. The electrode pressure is 3.kN 5-6.5 kN, the reservation time is 100ms, the interval after welding is 500-1000 ms, and the quenching time required for completely transforming the welding spot into martensite is met. In order to avoid rapid cooling of the spot welded joint due to the presence of the water cooled copper electrode and its quenching effect, the holding time after the tempering pulse was set to 0ms to prevent rapid cooling of the weld spot, and a schematic diagram of the welding process is shown in fig. 1.
The tensile shear test was conducted by welding a 150mm long and 50mm wide steel plate which was lapped in the manner shown in FIG. 2.
And (4) carrying out three times of repeated welding under the condition of the same welding process parameters, and respectively testing the tensile shear performance. To maintain alignment during the tensile test, shims made of the test material were used in each test, with the same thickness as the samples for the tensile shear test. And (3) performing a tensile test on an electronic universal testing machine, wherein the strain rate is 5-10 mm/min, simultaneously recording a load-displacement curve, extracting the maximum load from the load-displacement curve, and measuring the absorption energy.
The welding method is simple and does not need other auxiliary equipment, such as an intermediate layer or a backing plate. The tempering pulse adopts a single pulse mode, so that the welding process time is shortened and the energy consumption is further reduced. The method has different material thicknesses, adopts a single pulse mode to adjust welding heat input by adjusting tempering pulse time and tempering pulse current, and regulates and controls the softening degree of a heat affected zone. The method can obviously improve the tensile-shear strength of the spot-welded joint, improve the plasticity and toughness of the spot-welded joint, reduce the brittleness and hardness tendency, and increase the absorption energy of the spot-welded joint, so that the welding process window of the 800 MPa-grade hot-galvanized dual-phase steel resistance spot welding is widened, the tempering pulse is increased to further reduce the welding defects, the initial nugget is formed by the welding pulse, the final nugget size is further increased by combining the tempering pulse, the mechanical property is improved, in addition, the nugget size is further increased by combining the tempering pulse, and the splashing caused by overlarge welding current in the welding pulse process is avoided.
The above embodiments are not limited to the technical solutions of the embodiments themselves, and the embodiments may be combined with each other into a new embodiment. The above embodiments are only for illustrating the technical solutions of the present invention and are not limited thereto, and any modification or equivalent replacement without departing from the spirit and scope of the present invention should be covered within the technical solutions of the present invention.
Claims (8)
1. A resistance spot welding method for dual-phase steel is characterized by comprising the following steps:
s1, overlapping two steel plates to be welded on the welding platform, wherein the overlapping length direction of the two steel plates to be welded is the rolling direction, and the two steel plates to be welded are made of 800 MPa-grade hot-dip galvanized dual-phase steel;
s2, welding the two steel plates to be welded through a spot welding machine, wherein the welding point is the lap joint central point of the two steel plates to be welded;
s3, pre-pressing the two steel plates to be welded, wherein the pre-pressing time is 100 ms;
s4, adjusting the welding pulse current from small to large, welding the two steel plates to be welded, and tempering after welding;
s5, performing tensile shear performance test and nugget diameter measurement on the two steel plates welded together in the step S4;
and S6, repeating the steps S3 to S5 for a plurality of times under the condition of the same welding process parameters until welding spatters appear.
2. A dual phase steel resistance spot welding method according to claim 1, wherein said welding parameters in step S4 are: setting the welding time between 200ms and 400ms, setting the interval time after welding between 500ms and 1000ms, setting the tempering pulse current between 4kA and 6kA, and setting the tempering pulse time between 100ms and 300 ms.
3. A method of resistance spot welding of dual phase steel as claimed in claim 1 wherein said spot welder is a medium frequency direct current resistance spot welder.
4. A resistance spot welding method for dual phase steel according to claim 3 wherein said spot welder uses an electrode tip which is a dome shaped electrode having an end face diameter of 6mm and a welding pressure in the range of 3.5kN to 6.5 kN.
5. A resistance spot welding method for dual phase steel according to claim 1, wherein said steel plates to be welded are two steel plates having the same size, shape, material and thickness, and the contact position of said two steel plates when they are overlapped is a square.
6. A dual phase steel resistance spot welding method according to claim 5, wherein said two steel sheets to be welded have a length of 150mm and a width of 50mm, and form a 50mm x 50mm square shape when overlapped.
7. A dual phase steel resistance spot welding method according to claim 1, wherein said tensile shear performance test is performed on an electronic universal tester having a displacement rate of 5mm/min to 10 mm/min.
8. A dual phase steel resistance spot welding method according to claim 1 wherein said tempering is in a single pulse mode.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114850644A (en) * | 2022-05-06 | 2022-08-05 | 本钢板材股份有限公司 | Resistance spot welding method for 2000 MPa-level hot-formed steel plate |
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2021
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| CN106363288A (en) * | 2016-09-14 | 2017-02-01 | 重庆科技学院 | Resistance spot welding technology for improving quality of welding spots of dual-phase steel |
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