Steel material for metal connection joint with high interface bonding strength, metal connection joint and manufacturing method

Abstract

The present invention belongs to the technical field of steel-aluminum dissimilar metal connection, and specifically relates to a steel material, a metal connection joint and a manufacturing method for a metal connection joint with high interfacial bonding force. A plurality of concave structures are provided in the surface area of the steel material. The total area of the projections of the plurality of concave structures on the surface of the steel material is denoted as S1, the area of the region formed by enclosing the projections is denoted as S0, the maximum depth of the plurality of concave structures is denoted as D0, the projected area of a single concave on the surface of the steel material is denoted as S2, and the width of the region formed by enclosing the projections is denoted as W0; the following conditions are satisfied: W0≥3mm, 0.05mm≤D0≤1.0mm, 0.25D0 2 ≤S2≤25D0 2 ; S1 and S0 satisfy relationship 1. Applying the steel material to the steel-aluminum dissimilar metal joint can improve the spreadability of the liquid weld metal on the surface of the steel material, enhance the crack propagation resistance of the interface layer, improve the bonding force at the connection interface, and problems such as fracture failure will not occur at the interface connection.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel-aluminum dissimilar metal connection, and specifically relates to a steel material for a metal connection joint with high interface bonding strength, a metal connection joint and a manufacturing method. Background Art

[0002] At present, there are two main directions for lightweight strategies in vehicle body structure design. One is to use advanced high-strength steel materials to achieve thinning and weight reduction of structural parts, and the other is to use lightweight materials instead of steel materials to achieve weight reduction. Aluminum alloy has a low density, about 1 / 3 of that of steel materials, high specific strength and specific stiffness, and can reduce the weight of vehicle body parts with the same performance by more than 30%. It is one of the most promising lightweight materials in vehicle body lightweight design. Although aluminum alloy has more potential than steel materials in terms of vehicle body lightweighting, the collision performance of aluminum alloy in some key safety parts of the vehicle body cannot be compared with advanced high-strength steel. Therefore, from the dual perspectives of lightweight and safety, steel-aluminum hybrid vehicles will become the mainstream vehicle body lightweight design solution in the future.

[0003] The bottleneck problem that needs to be solved in the steel-aluminum hybrid body solution is the connection problem between steel and aluminum. The inherent disparity in physical properties between steel and aluminum alloys determines that the two cannot be connected together using traditional fusion welding technology, and only fusion brazing technology can be used to connect steel and aluminum alloys. During the steel-aluminum fusion brazing process, under the action of the heat source, the steel does not melt, and the aluminum alloy and filler metal are melted and mixed to form liquid weld metal, which spreads a certain width on the surface of the steel plate. In the subsequent cooling and solidification process, an intermetallic compound layer with a certain thickness is formed on the interface between the liquid weld metal and the steel, thereby realizing the metallurgical connection of steel and aluminum dissimilar metals.

[0004] For steel-aluminum dissimilar metal fusion brazing joints, the interfacial bonding strength between steel and weld metal is the core factor that determines the performance of steel-aluminum dissimilar metal fusion brazing joints. The effective spreading width of the liquid weld metal on the steel surface directly determines the interfacial bonding strength between steel and weld metal. Regarding steel-aluminum dissimilar metal connections, although some improvement methods have been proposed in recent years, there is still a large gap between the performance of the joint and the aluminum alloy parent material. Under load conditions, the steel-aluminum joint will fail and fracture due to insufficient interfacial bonding strength. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problems of the prior art steel-aluminum joint interface, such as insufficient crack propagation resistance and insufficient interface bonding strength, and easy interface failure and fracture, so as to provide a steel material, a metal connection joint and a manufacturing method for a high interface bonding strength metal connection joint.

[0006] To this end, the present invention provides the following technical solutions.

[0007] In a first aspect, the present invention provides a steel material for a metal connection joint with high interface bonding strength, wherein at least a plurality of recessed structures are arranged on the surface of the steel material connected to the aluminum alloy, the total area of ​​the projections of the plurality of recessed structures on the surface of the steel material is recorded as S1, the area of ​​the area formed by the projections is recorded as S0, the maximum depth of the plurality of recessed structures is recorded as D0, the projection area of ​​a single recess on the surface of the steel material is recorded as S2, and the width of the area formed by the projections is recorded as W0; W0 ≥ 3 mm; D0: 0.05 mm ≤ D0 ≤ 1.0 mm; S2: 0.25 D0 2 ≤S2≤25D0 2 ; S1 and S0 satisfy the relation 1;

[0008] Relationship 1.

[0009] As an example, the ratio of S1 to S0 is 0.05, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.95 or any two numerical ranges. W0 is any value such as 3mm, 6mm, 9mm, 12mm, 15mm, 18mm, 21mm, 24mm, 27mm, etc. D0 is any value such as 0.05mm, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, etc. The projection area of ​​a single concave structure on the surface of the steel material satisfies 0.25D0 2 ≤S2≤25D0 2 , no specific requirements are made.

[0010] In an optional embodiment, the shape of the projection of the recessed structure on the surface of the steel material is an arbitrary shape. Preferably, the shape of the projection of the recessed structure on the surface of the steel material includes at least one of a regular shape and an irregular shape; the shape of the projection of the recessed structure on the surface of the steel material includes but is not limited to at least one of a circle, a triangle, a polygon and an irregular shape.

[0011] In an optional embodiment, from outside to inside, the surface of the steel material includes a non-oxidized layer and a transition layer;

[0012] Preferably, the oxygen content in the grain boundary of the transition layer is 5-47wt%. As an example, the oxygen content in the grain boundary of the transition layer is 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 47wt% or any two numerical ranges.

[0013] In an optional embodiment, the thickness T1 of the transition layer is 0.1-15 μm;

[0014] Preferably, the thickness of the steel material is not greater than 8 mm;

[0015] Preferably, the tensile strength of the steel material at room temperature is not less than 200 MPa.

[0016] In an optional embodiment, a coating is provided on the surface of the steel material;

[0017] Preferably, the material of the coating is at least one of a zinc-based material, an aluminum-based material and a nickel-based material;

[0018] Preferably, the coating is made of zinc-based material.

[0019] A second aspect of the present invention provides a metal connection joint, comprising a steel material, an aluminum alloy and a weld; the steel material comes from the above-mentioned steel material.

[0020] In an optional embodiment, the weld includes an intermetallic compound layer, and the thickness T of the intermetallic compound layer is IMC Not more than 30μm;

[0021] Preferably, the thickness T of the intermetallic compound layer is IMC :T IMC ≥2μm.

[0022] In an optional embodiment, the aluminum alloy is 5XXX series or 6XXX series; it should be noted that 5XXX series and 6XXX series refer to the types of aluminum alloys;

[0023] Preferably, the thickness of the aluminum alloy is not greater than 8 mm.

[0024] A third aspect of the present invention provides a method for manufacturing a metal connecting joint, which uses the above-mentioned steel material; filler material and aluminum alloy are melted to form liquid metal, and the liquid metal spreads on the surface of the steel material and solidifies.

[0025] In an optional embodiment, the spreading width L0 is not greater than W0;

[0026] Preferably, the spreading width L0 is not less than 1 mm;

[0027] Preferably, the spreading width L0: L0≤15mm.

[0028] The spreading width refers to the distance that the liquid metal spreads on the surface of the steel material perpendicular to the welding direction.

[0029] The technical solution of the present invention has the following advantages:

[0030] 1. The steel material for high interface bonding strength metal connection joint provided by the present invention is provided with a plurality of recessed structures at least in the surface area of ​​the steel material connected with the aluminum alloy, the total area of ​​the projections of the plurality of recessed structures on the surface of the steel material is recorded as S1, the area of ​​the area formed by the projections is recorded as S0, the maximum depth of the plurality of recessed structures is recorded as D0, the projection area of ​​a single recess on the surface of the steel material is recorded as S2, and the width of the area formed by the projections is recorded as W0; W0 ≥ 3 mm; D0: 0.05 mm ≤ D0 ≤ 1.0 mm; S2: 0.25 D0 2 ≤S2≤25D0 2 ; The S1 and S0 satisfy the relationship 1. The application of the steel material to the steel-aluminum dissimilar metal joint can improve the spreadability of the liquid weld metal on the steel material surface, enhance the ability of the interface layer to resist crack propagation, improve the bonding strength at the connection interface, and the interface connection will not have problems such as fracture failure. The steel material can be connected to the aluminum alloy by generating intermetallic compounds with the weld metal to form a steel-aluminum dissimilar metal connection joint with high interface bonding strength. Under tensile shear loads, the joint will preferentially fail at the aluminum alloy parent material fracture rather than at the interface. The steel material surface is provided with a number of recessed structures. This non-planar three-dimensional structure increases the spreading width and area of ​​the liquid weld metal on the steel material surface, improves the ability of the interface layer to resist crack propagation, and enhances the spreadability of the liquid weld metal. Finally, a steel-aluminum dissimilar metal connection joint with high interface bonding strength is obtained, which solves the problem of interface failure of the steel-aluminum joint.

[0031] Furthermore, the steel material of the present invention satisfies W0 not less than 3 mm, 0.05 mm ≤ D0 ≤ 1.0 mm, 0.25 D0 2 ≤S2≤25D0 2 , and the ratio of S1 to S0 satisfies 0.05-0.95, which can greatly increase the spreading area of ​​the liquid weld metal. Under the same spreading width, the special structure of the steel material of the present invention increases the spreading area by about 40% compared with the flat structure. In addition, the concave structure of the special structure can also ensure the spreading width L0 of the liquid weld metal.

[0032] 2. The steel material for high interface bonding strength metal connection joints provided by the present invention is provided with a special transition layer, which can improve the spreading performance of the weld metal on the surface of the steel material, and help the liquid weld metal to form an intermetallic compound layer with uniform thickness, complete structure and no crack defects on the surface of the steel material. The surface of the steel material is provided with an oxygen-free layer and a transition layer, and the oxygen-free layer can reduce the interfacial tension between the weld metal and the surface of the steel material, and significantly improve the spreading ability of the liquid weld metal on the surface of the steel material; the present invention is the first to apply a steel material with a transition layer having a certain grain boundary oxygen content on the secondary surface to a metal connection joint, and can prepare an intermetallic compound layer with more uniform thickness and higher structural consistency, which can further effectively avoid the formation of microcracks in the intermetallic compound layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 is a schematic diagram of the area formed by enclosing the projection in the present invention;

[0035] Figure 2 is another schematic diagram of the area formed by enclosing the projection in the present invention;

[0036] Figure 3 This is a schematic diagram of the enclosed projection area of ​​the steel material in Example 1 of the present invention;

[0037] Figure 4 is a schematic structural diagram of a metal joint according to Embodiment 1 of the present invention;

[0038] Figure 5 This is a schematic diagram of the enclosed projection area of ​​the steel material in Example 9 of the present invention;

[0039] Figure 6 This is a schematic diagram of the enclosed projection area of ​​the steel material in Example 10 of the present invention;

[0040] Figure 7 This is a schematic diagram of the fracture interface of a metal joint in a comparative example of the present invention;

[0041] Reference numerals:

[0042] 1-first line; 2-second line; 3-third line; 4-fourth line; 5-fifth line; 6-sixth line; 7-seventh line; 8-eighth line; 9-steel material; 10-weld; 11-aluminum alloy. DETAILED DESCRIPTION

[0043] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0044] In the prior art, when aluminum alloy is overlapped on the surface of steel material for welding to form a steel-aluminum dissimilar connection joint, the interface crack propagation resistance and bonding strength are insufficient, and interface failure and fracture are prone to occur. In order to solve the problems existing in the prior art, the present invention provides a steel material, which is applied to the metal connection joint, and the interface joint has good interface bonding strength and crack propagation resistance. The solution provided by the present invention is as follows.

[0045] The present invention provides a steel material for a metal connection joint with high interface bonding strength. The surface of the steel material is pre-processed in advance by rolling, machining or laser processing to form a non-planar three-dimensional structure on the surface. A plurality of recessed structures are arranged on the surface area of ​​the steel material connected to the aluminum alloy. The non-planar three-dimensional structure, the total area of ​​the projections of the plurality of recessed structures on the surface of the steel material is recorded as S1, the area of ​​the area formed by the projections is recorded as S0, the maximum depth of the plurality of recessed structures is recorded as D0, and the width of the area formed by the projections is recorded as W0; W0≥3mm; D0: 0.05mm≤D0≤1.0mm; S2: 0.25D0 2 ≤S2≤25D0 2 ; S1 and S0 satisfy the relation 1;

[0046] Relationship 1.

[0047] Among them, a plurality of concave structures are arranged regularly or irregularly on the surface of the steel material, a plurality of concave structures can be the same or different, the depths of a plurality of concave structures can be the same or different, the shape of their projection on the surface of the steel material is any shape, and the shape of the projection of the concave structure on the surface of the steel material includes at least one of a regular shape and an irregular shape, including but not limited to at least one of a circle, a triangle, a polygon and an irregular shape. The shape of the concave structure can be any non-planar three-dimensional structure such as a hemisphere, an inverted pyramid, an inverted quadrangular pyramid, etc. The projection of a single concave structure on the surface of the steel material satisfies 0.25D0 2 ≤S2≤25D0 2 That is, there is no specific restriction on the projection area of ​​a single recessed structure, and the projection areas of different recessed structures may be the same or different.

[0048] It should be noted that other areas on the surface of the steel material may be provided with a number of recessed structures or may be planar structures, depending on demand and cost. The projection refers to the projection of the recessed structure on the surface of the steel material along the thickness direction of the steel material. The area enclosed by the projection refers to a closed area formed by the outermost points of the projection located at the edge of the area (also called edge points) enclosed in sequence by straight lines and / or the reverse extension of the straight lines; the area is preferably a regular shape, such as a polygon such as a triangle, rectangle, pentagon, hexagon, etc., refer to Figure 1 and Figure 2 , not limited to Figure 1 and Figure 2 Shapes listed.

[0049] by Figure 1 For example, the first line 1 and the second line 2 are formed by the straight lines connecting the two different tangent points of the circle and the points outside the two quadrilaterals and their reverse extension lines, and the third line 3 is formed by the straight lines connecting the points outside the quadrilaterals and their reverse extension lines. The closed area formed by the first line 1, the second line 2 and the third line 3 is the area enclosed by the projection, and the area is recorded as S0. Figure 2 For example, the fourth line 4 formed by the ellipse tangent point, the circular tangent point and the prism edge point, the fifth line 5 formed by the prism edge point, the sixth line 6 formed by the prism and the triangle edge point, the seventh line 7 formed by the edge points of two triangles, the eighth line 8 formed by the triangle edge point, the prism edge point and the ellipse tangent point, the fourth line 4, the fifth line 5, the sixth line 6, the seventh line 7 and the eighth line 8 are formed by the closed area, which is the area enclosed by the projection, and the area is recorded as S0. It can be understood that the area line can cover a certain side of the projection; the area cannot pass through the projection.

[0050] The width of the area enclosed by the projection refers to the average value of the minimum length and the maximum length of the area enclosed by the projection along the direction perpendicular to the welding direction. It can be understood that the minimum length includes the case of 0.

[0051] From the outside to the inside of the steel material, the surface of the steel material includes a non-oxidized layer and a transition layer; wherein the non-oxidized layer means that the surface of the steel material is not oxidized; the transition layer is located on the side of the non-oxidized layer away from the surface of the steel material, and the transition layer grain boundary contains a certain amount of oxygen, which exists in the form of oxides, and the oxidized elements are alloy elements in the steel matrix, such as iron, manganese, silicon, etc. It should be noted that the oxygen content in the transition layer grain boundary is obtained by testing according to methods known in the art, such as: X-ray energy spectrum (Energy-dispersive X-ray spectroscopy, EDS) micro-area composition analysis.

[0052] In the present invention, the tensile strength of the steel material at room temperature is not less than 200 MPa; the tensile strength of the steel material is tested by conventional testing methods in the art, such as GB / T 228-2010 Room temperature test method for tensile testing of metallic materials.

[0053] The present invention also provides a metal connecting joint, comprising a steel material, an aluminum alloy and a weld; the steel material comes from the above-mentioned steel material.

[0054] The steel and aluminum alloy joints are overlapped, and the aluminum alloy is overlapped on the surface of the steel material. The aluminum alloy and the filler material are melted by laser, electric arc, laser arc combination, etc. The aluminum alloy and the filler material form liquid weld metal and spread on the unmelted steel surface. The liquid weld metal has good spreadability on the surface of the above-mentioned special structural steel material, and after solidification, it generates intermetallic compounds, which are three-dimensional interface layers. Compared with the traditional plane structure interface layer, when the crack propagates in the three-dimensional interface layer with the same surface, this three-dimensional interface layer increases the crack propagation resistance in the interface layer and increases the crack propagation distance, so that the interface of the connection joint has excellent crack propagation resistance.

[0055] The filling material is a material known in the art, such as welding wire, metal powder, etc.

[0056] The process parameters of the laser, arc, laser arc composite and other methods are selected from the parameters known in the art to ensure that the aluminum alloy and the filling material can be melted, without strict requirements on the parameters, and different parameters do not affect the effect of the present invention.

[0057] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0058] Example 1

[0059] This embodiment provides a method for manufacturing a metal connection joint, comprising the following steps:

[0060] (1) Low alloy high strength steel is selected as the steel material with a thickness of 1.4 mm. Several inverted triangular pyramid structures are prefabricated at the position to be welded by rolling. Along the thickness direction of the steel material, the projection shape of the concave structure on the surface of the steel material is triangular and of the same size. The average value W0 of the minimum and maximum widths of the area enclosed by these projections is 10 mm. The area of ​​this area is recorded as S0, and the length of this area along the welding direction is recorded as W1. The schematic diagram of the enclosed projection area is shown in Figure 3 ,by Figure 3 As shown, S0=W0×W1; the maximum depth D0 of all the concave structures is 0.3mm, and the schematic diagram of the maximum depth D0 is shown in Figure 4 , Figure 4 9 is steel material, 10 is weld, and 11 is aluminum alloy; the projection area S2 of a single concave structure on the surface of the steel material is 4D0 2 The total area of ​​all the concave structures projected on the steel surface is recorded as S1. The ratio of the sum of the projected areas of all the concave structures on the steel surface S1 to the area S0 formed by all the projections is 0.5 (S1 / S0). The thickness of the transition layer of the steel is T1, which is 2.3 μm. The oxygen content of the grain boundary in the transition layer is C. O In this embodiment, the region is a closed region formed by connecting the outermost points of the projection located at the edge in sequence with straight lines and / or reverse extensions of adjacent straight lines.

[0061] Select 5XXX series aluminum alloy sheet with a thickness of 1.6 mm.

[0062] Commercial ER4043 aluminum-based welding wire is used as the filler material, and the diameter of the welding wire is 1.2 mm.

[0063] (2) Laser is selected as the heat source, the heat source moving speed is 600 mm / min, and the heat input is 220 J / mm; the filling rate of the welding wire is 1500 mm / min, and the welding wire and part of the aluminum alloy melt to form a liquid weld metal that spreads on the surface of the steel material. The schematic diagram of the spreading width L0 and the width W0 of the area formed by the enclosed projection is shown in Figure 4 After solidification, a steel-aluminum dissimilar metal connection joint is obtained.

[0064] A scanning electron microscope is used to test the linear spreading width of the weld metal in the steel-aluminum dissimilar metal connection joint and the thickness of the intermetallic compound formed by the weld metal on the surface of the steel material.

[0065] Embodiment 2-8

[0066] Embodiment 2-8 provides a method for manufacturing a metal connection joint, which differs from Embodiment 1 in that the recess structure and parameters are different, the thickness and oxygen content of the transition layer are different, and the heat source during the preparation process is different.

[0067] The recessed structures and parameters, transition layer thickness and oxygen content, and heat sources during the preparation process of each embodiment are shown in Table 1-2.

[0068] Example 9

[0069] This embodiment provides a method for manufacturing a metal connection joint, comprising the following steps:

[0070] (1) Low alloy high strength steel is selected as the steel material with a thickness of 1.6 mm. Laser processing is used to prefabricate inverted triangular pyramids, inverted quadrangular pyramids, and hemispherical concave structures at the positions to be welded on the steel material. The concave structures of the same shape have the same size. Along the thickness direction of the steel material, the projection of the concave structure on the surface of the steel material is in the shape of a triangle, a quadrilateral, and a circle, with the proportions of 10%, 40%, and 50% respectively. The width W0 of the area enclosed by these projections is 12 mm, and the area is recorded as S0. See the schematic diagram. Figure 5 ; The maximum depth D0 of all the concave structures is 0.23mm, and the single area of ​​the triangle projected is 4.6D0 2 , the single area of ​​the projection as a quadrilateral is 7.6D0 2 , the single area projected as a circle is 2.8D0 2 The total area of ​​all the concave structures projected on the steel surface is recorded as S1. The ratio of the sum of the projected areas of all the concave structures on the steel surface S1 to the area S0 formed by all the projections is 0.3 (S1 / S0). The thickness of the transition layer of the steel is T1, which is 3.8 μm. The oxygen content of the grain boundary in the transition layer is C. O is 25%.

[0071] Select 5XXX series aluminum alloy sheet with a thickness of 1.8 mm.

[0072] Commercial ER4043 welding wire is used as the filler material, and the diameter of the welding wire is 1.2 mm.

[0073] (2) The arc is selected as the heat source, the heat source movement rate is 25 mm / s, and the heat input is 1500 J / mm; the filling rate of the welding wire is 2300 mm / min, and a steel-aluminum dissimilar metal connection joint is obtained after solidification.

[0074] A scanning electron microscope is used to test the linear spreading width of the weld metal in the steel-aluminum dissimilar metal connection joint and the thickness of the intermetallic compound formed by the weld metal on the surface of the steel material.

[0075] Example 10

[0076] This embodiment provides a method for manufacturing a metal connection joint, comprising the following steps:

[0077] (1) Low alloy high strength steel is selected as the steel material with a thickness of 1.0 mm. A hemispherical concave structure is prefabricated at the position to be welded on the steel material by machining. Along the thickness direction of the steel material, the projection of the concave structure on the surface of the steel material is circular. The width W0 of the area enclosed by these projections is 8 mm, and the area is recorded as S0. See the schematic diagram Figure 6The maximum depth D0 of all the concave structures is between 0.18 and 0.35 mm. The projection area of ​​different concave structures is different, but the projection area of ​​a single concave is between 0.9 and 3.6 D0. 2 The total area of ​​all the concave structures projected on the steel surface is recorded as S1. The ratio of the sum of the projected areas of all the concave structures on the steel surface S1 to the area S0 formed by all the projections is 0.7 (S1 / S0). The thickness of the transition layer of the steel is T1, which is 1.5 μm. The oxygen content of the grain boundary in the transition layer is C. O In this embodiment, the area is a closed area formed by connecting the outermost tangent points of the circle located at the edge with straight lines or the reverse extension lines of adjacent straight lines, referring to Figure 6 .

[0078] Select 5XXX series aluminum alloy sheet with a thickness of 1.4 mm.

[0079] Commercial ER4047 welding wire is used as the filler material, and the diameter of the welding wire is 1.2 mm.

[0080] (2) Laser / arc was selected as the heat source, the heat source moving rate was 500 mm / s, and the heat input was 1100 J / mm; the filling rate of the welding wire was 1800 mm / min, and a steel-aluminum dissimilar metal connection joint was obtained after solidification.

[0081] A scanning electron microscope is used to test the linear spreading width of the weld metal in the steel-aluminum dissimilar metal connection joint and the thickness of the intermetallic compound formed by the weld metal on the surface of the steel material.

[0082] Comparative Example 1-2

[0083] Comparative Example 1-2 provides a method for manufacturing a metal connection joint, which is different from Example 1 in that the steel material surface is not subjected to a concave treatment and has a planar structure. The parameters of the manufacturing process are shown in Table 1-2.

[0084] Comparative Examples 3-5

[0085] Comparative Examples 3-5 provide a method for manufacturing a metal connection joint, which differs from Example 1 in that the parameters of the recessed structure are different. The recessed structures and parameters, transition layer thickness and oxygen content, and heat sources during the preparation process of each comparative example are shown in Table 1-2.

[0086] Table 1 Parameters of metal connection joints

[0087]

[0088] Note: Unless otherwise specified, the projection shape and size are the same; the same heat source uses the same process parameters; “-” means that the parameter does not exist.

[0089] Table 2 Parameters of metal connection joints

[0090]

[0091] Note: “-” means the parameter does not exist.

[0092] The performance of metal connection joints was tested according to GB / T 228-2010 Metal Material Tensile Test Room Temperature Test Method. The results are shown in Table 3.

[0093] Table 3 Performance of metal connection joints

[0094]

[0095] Conclusion: According to the results in Table 3, the present invention provides a plurality of concave structures on the surface of the steel material, and the concave structures satisfy W0 not less than 3mm, 0.05mm≤D0≤1.0mm, 0.25D0 2 ≤S2≤25D0 2 , and the ratio of S1 to S0 satisfies 0.05-0.95, thereby forming a steel-aluminum dissimilar metal connection joint with high interface bonding strength. Under tensile shear load, the joint preferentially fails at the aluminum alloy base material rather than at the interface, thereby improving the ability of the interface layer to resist crack propagation and greatly increasing the spreading area of ​​the liquid weld metal. Under the condition of the same spreading width, the spreading area of ​​the special steel material structure of the present invention is increased by about 40% compared with the plane structure.

[0096] From comparative examples 1-2, the recessed structure provided in the present invention can greatly improve the joint strength, will not break at the joint, and has significantly higher strength; Figure 7 This is the fractured sample of Example 1, indicating that the performance of the comparative joint is poor and fracture occurs at the interface. From Comparative Examples 3-5, it can be seen that the concave structure W0 of the present invention is not less than 3mm, 0.05mm≤D0≤1.0mm, 0.25D0 2 ≤S2≤25D0 2 , and the ratio of S1 to S0 satisfies 0.05-0.95, forming a steel-aluminum dissimilar metal connection joint with high interface bonding strength, which has great application value for dissimilar metal brazing. From comparative examples 1-5, although comparative examples 3-5 break at the interface between the weld metal and the steel material, the joint strength is still higher than that of the steel material without the recessed structure.

[0097] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A steel material for a metal connection joint with high interface bonding strength, characterized in that: At least a plurality of recessed structures are provided in the surface area of ​​the steel material connected to the aluminum alloy, the total area of ​​the projections of the plurality of recessed structures on the surface of the steel material is recorded as S1, the area of ​​the area formed by the projections is recorded as S0, the maximum depth of the plurality of recessed structures is recorded as D0, the projection area of ​​a single recess on the surface of the steel material is recorded as S2, and the width of the area formed by the projections is recorded as W0; W0 ≥ 3 mm; D0: 0.05 mm ≤ D0 ≤ 1.0 mm; S2: 0.25 D0 2 ≤S2≤25D0 2 ; S1 and S0 satisfy the relation 1; Relation 1; From the outside to the inside, the surface of the steel material includes a non-oxidized layer and a transition layer; The oxygen content in the grain boundaries of the transition layer is 5-47wt%.

2. The steel material according to claim 1, characterized in that: The projection shape of the recessed structure on the surface of the steel material is any shape; The width of the area enclosed by the projection is the average of the minimum length and the maximum length of the area enclosed by the projection along the direction perpendicular to the welding direction.

3. The steel material according to claim 2, characterized in that: The shape of the projection of the concave structure on the surface of the steel material includes at least one of a regular shape and an irregular shape.

4. The steel material according to claim 2, characterized in that: The projection shape of the concave structure on the surface of the steel material includes at least one of a circular shape, a polygonal shape and an irregular shape.

5. The steel material according to claim 1, characterized in that: The thickness T1 of the transition layer is 0.1-15 μm; The thickness of the steel material is not more than 8mm; The tensile strength of the steel material at room temperature is not less than 200 MPa.

6. The steel material according to claim 1, characterized in that: A coating is provided on the surface of the steel material; The material of the coating is at least one of a zinc-based material, an aluminum-based material and a nickel-based material.

7. The steel material according to claim 6, characterized in that: The material of the coating is zinc-based material.

8. A metal connection joint, characterized in that: It comprises steel material, aluminum alloy and welding seam; the steel material is the steel material described in any one of claims 1-7.

9. The metal connection joint according to claim 8, characterized in that: The weld includes an intermetallic compound layer, the thickness of the intermetallic compound layer is T IMC Not more than 30μm; The thickness T of the intermetallic compound layer IMC :T IMC ≥2μm.

10. The metal connection joint according to claim 8 or 9, characterized in that: The aluminum alloy is 5XXX series or 6XXX series; The thickness of the aluminum alloy is not greater than 8 mm.

11. A method for manufacturing a metal connection joint, characterized in that: The steel material according to any one of claims 1 to 7 is used; the filler material and the aluminum alloy are melted to form liquid metal, and the liquid metal spreads on the surface of the steel material and solidifies.

12. The manufacturing method according to claim 11, characterized in that: The spreading width L0 is not greater than W0; The spreading width L0 is not less than 1 mm; The spreading width L0: L0≤15mm.

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