Joints and connections
By forming a joint with controlled diffusion layer thickness and specific chemical compositions for steel and aluminum alloy parts, the joint achieves enhanced strength by preventing intermetallic compounds, addressing the strength deficiencies in existing steel-aluminum alloy joints.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- NIPPON STEEL CORPORATION
- Filing Date
- 2022-10-21
- Publication Date
- 2026-05-20
AI Technical Summary
Existing joints between steel and aluminum alloy materials often fail to achieve sufficient strength, even when made thinner, due to the formation of brittle intermetallic compounds at the joining interface.
A joint configuration comprising a steel part and an aluminum alloy part, with a diffusion layer between them, where the steel part has specific chemical compositions and the aluminum alloy part has different compositions, and the thickness of the diffusion region adjacent to the aluminum alloy part is controlled to 19.5 to 25.0 μm, forming a diffusion layer through the mutual diffusion of Fe and Al instead of intermetallic compounds.
The joint achieves excellent strength by avoiding intermetallic compounds, ensuring sufficient tensile strength through controlled diffusion layer thickness.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a joining joint, and more particularly to a joining joint in which a steel material and an aluminum alloy material are joined.
Background Art
[0002] In mechanical structure parts used in automobiles, industrial machines, etc., strength is required at specific parts, and weight reduction may be required as a whole. In order to meet such requirements, a joining joint has been proposed in which a part where strength is required is made of a steel material and other parts are made of an aluminum alloy material in order to achieve weight reduction of the whole. Such a joining joint is used, for example, for pistons in engines used in automobiles, industrial machines, etc. Specifically, the upper part of the piston where strength is required is made of a steel material, and the lower part of the piston is made of an aluminum alloy material in order to achieve weight reduction of the whole. In this case, excellent strength can be obtained while achieving weight reduction.
[0003] In such a joining joint made of different alloy materials, improvement in the strength of the joining part is required. Therefore, improvement of the joining part of such a joining joint has been proposed in Japanese Patent Application Laid-Open No. 2003-33885 (Patent Document 1).
[0004] The joining structure disclosed in Patent Document 1 joins a first member made of steel and a second member made of an aluminum alloy. And the thickness of the reaction product layer formed at the joining interface between the first member and the second member is set to 0.5 μm or less. A reaction product layer is formed at the joining part between the first member (steel) and the second member (aluminum alloy material). The reaction product layer is composed of an intermetallic compound and is brittle. Therefore, the reaction product layer, which is the joining part, is made thin. Thereby, the probability of cracks occurring starting from the intermetallic compound can be reduced, and it is described in Patent Document 1 that sufficient strength can be ensured in the joining structure.
Prior Art Documents
Patent Documents
[0005] [Patent Document 1] Japanese Patent Publication No. 2003-33885 [Overview of the project] [Problems that the invention aims to solve]
[0006] However, in joints between steel and aluminum alloy materials, even if the joint is made thinner, sufficient strength may not always be obtained.
[0007] The objective of the present invention is to provide a joint with excellent strength. [Means for solving the problem]
[0008] The joint according to the present invention is Steel parts and, Aluminum alloy part, The system comprises a diffusion layer formed between the steel portion and the aluminum alloy portion, The aforementioned steel part is The chemical composition is expressed in mass percent. C: 0.15~0.50%, Si: 0.01~0.50%, Mn: 0.20~1.50%, P: 0.030% or less, S: 0.030% or less, Cr: 0.50~1.50%, Mo: 0.01~0.30%, Al: 0.005~0.060%, N: 0.020% or less, and, It contains O: 0.0050% or less, with the remainder consisting of Fe and impurities. The aforementioned aluminum alloy part is The chemical composition is expressed in mass percent. Cu: 0.80~1.30%, Si: 11.00~13.00%, Mg: 0.70~1.30%, Ni: 0.80~1.50%, Zn: 0.15% or less, Fe: 0.80% or less, Mn: 0.15% or less, Ti: 0.20% or less, and Cr: 0.10% or less, and the balance consists of Al and impurities, The diffusion layer is adjacent to the aluminum alloy part and includes a diffusion region adjacent to the aluminum alloy part where the Fe content ratio is 1.0 - 3.0% when the Fe content in the steel part is taken as 100%, the thickness of the diffusion region adjacent to the aluminum alloy part obtained by performing glow discharge optical emission spectrometry in the thickness direction of the diffusion layer is 19.5 - 25.0 μm.
[0009] The joint according to the present invention comprises a steel part, an aluminum alloy part, and a diffusion layer formed between the steel part and the aluminum alloy part. The steel part has a chemical composition in mass% of C: 0.15 - 0.50%, Si: 0.01 - 0.50%, Mn: 0.20 - 1.50%, P: 0.030% or less, S: 0.030% or less, Cr: 0.50 - 1.50%, Mo: 0.01 - 0.30%, Al: 0.005 - 0.060%, N: 0.020% or less, and O: 0.0050% or less, and further contains one or more selected from the group consisting of Group 1 and Group 2, and the balance consists of Fe and impurities, The aluminum alloy part has a chemical composition in mass% of Cu: 0.80 - 1.30%, Si: 11.00 - 13.00%, Mg: 0.70 - 1.30%, Ni: 0.80 - 1.50%, Zn: 0.15% or less, Fe: 0.80% or less Mn: 0.15% or less, Ti: 0.20% or less, and Cr: 0.10% or less, and the balance consists of Al and impurities, The diffusion layer is adjacent to the aluminum alloy part and includes a diffusion region adjacent to the aluminum alloy part where the Fe content ratio is 1.0 to 3.0% when the Fe content in the steel part is 100%, and the thickness of the diffusion region adjacent to the aluminum alloy part obtained by performing glow discharge optical emission spectrometry in the thickness direction of the diffusion layer is 19.5 to 25.0 μm. [Group 1] Cu: 0.40% or less, Ni: 0.40% or less, Sn: 0.100% or less, Ti: 0.050% or less, Nb: 0.050% or less, and B: 0.0050% or less, and one or more selected from the group consisting of [Group 2] Ca: 0.0050% or less, and Mg: 0.0050% or less, and one or more selected from the group consisting of
Advantages of the Invention
[0010] The joint of the present invention has excellent strength.
Brief Description of the Drawings
[0011] [Figure 1] FIG. 1 is a perspective view showing an example of the joint according to the present embodiment. [Figure 2] FIG. 2 is a diagram showing the relationship between the distance in the thickness direction and the Fe concentration and Al concentration obtained by performing GDS analysis in the thickness direction (axial direction of the joint) of the part including the diffusion layer in the joint of the present embodiment. [Figure 3] FIG. 3 is a diagram showing the relationship between the distance (μm) in the thickness direction (axial direction of the joint) and the Fe content ratio (%) in the diffusion layer. [Figure 4]Figure 4 shows the relationship between the tensile strength (MPa) of the joint and the thickness (μm) of the diffusion region adjacent to the aluminum alloy portion. [Figure 5] Figure 5 is a schematic diagram of a friction bonding device. [Modes for carrying out the invention]
[0012] The inventors of this invention investigated joints with excellent strength. As a result, they obtained the following findings.
[0013] As pointed out in Patent Document 1, in joints between steel and aluminum alloy materials, if the joint portion is made of an intermetallic compound, the strength of the joint portion is reduced. Therefore, the inventors considered that if the joint portion is not made of an intermetallic compound, but rather formed by the diffusion of Fe and Al into each other, the strength of the joint could be increased.
[0014] Therefore, as a result of the above considerations, the steel portion of the joint contains, by mass%, C: 0.15~0.50%, Si: 0.01~0.50%, Mn: 0.20~1.50%, P: 0.030% or less, S: 0.030% or less, Cr: 0.50~1.50%, Mo: 0.01~0.30%, Al: 0.005~0.060%, N: 0.020% or less, and O: 0.0050% or less, and if any element is included, it further contains one or more selected from the groups consisting of the first and second groups mentioned above, with the remainder being Fe and impurities, and the aluminum alloy portion contains, by mass%, Cu: 0.80~1.30 We found that if a material has a chemical composition containing %, Si: 11.00~13.00%, Mg: 0.70~1.30%, Ni: 0.80~1.50%, Zn: 0.15% or less, Fe: 0.80% or less, Mn: 0.15% or less, Ti: 0.20% or less, and Cr: 0.10% or less, with the remainder being Al and impurities, then in the joint, the Fe content gradually decreases from the steel part towards the aluminum alloy part, and the Al content gradually increases from the steel part towards the aluminum alloy part. This allows the joint to be a diffusion layer formed by the mutual diffusion of Fe and Al, rather than an intermetallic compound.
[0015] The inventors further focused on the thickness of the diffusion layer. Patent Document 1 attempts to improve strength by making the joint as thin as possible. However, in the case of a joint composed of a steel part and an aluminum alloy part with the above-mentioned chemical composition and the above-mentioned diffusion layer, it was found that the thickness of the diffusion region adjacent to the aluminum alloy part, where the Fe content ratio is 1.0 to 3.0% when the Fe content in the steel part is 100% by mass, particularly affects the strength of the diffusion layer. Therefore, the thickness of the diffusion region adjacent to the aluminum alloy part was measured by glow discharge optical emission spectrometry (GDS), and the relationship between the thickness of the diffusion region adjacent to the aluminum alloy part and the strength of the joint was investigated. As a result, it was found that sufficient strength can be obtained in the joint if the thickness of the diffusion region adjacent to the aluminum alloy part is 19.5 to 25.0 μm.
[0016] Based on the above findings, the joint of this embodiment has the following configuration.
[0017] [1] Steel parts and, Aluminum alloy part, The system comprises a diffusion layer formed between the steel portion and the aluminum alloy portion, The aforementioned steel part is The chemical composition is expressed in mass percent. C: 0.15~0.50%, Si: 0.01~0.50%, Mn: 0.20~1.50%, P: 0.030% or less, S: 0.030% or less, Cr: 0.50~1.50%, Mo: 0.01~0.30%, Al: 0.005~0.060%, N: 0.020% or less, and, It contains O: 0.0050% or less, with the remainder consisting of Fe and impurities. The aforementioned aluminum alloy part is The chemical composition is expressed in mass percent. Cu: 0.80~1.30%, Si: 11.00~13.00%, Mg: 0.70~1.30%, Ni: 0.80~1.50%, Zn: 0.15% or less, Fe: 0.80% or less, Mn: 0.15% or less, Ti: 0.20% or less, and, It contains Cr: 0.10% or less, with the remainder consisting of Al and impurities. The aforementioned diffusion layer is The aluminum alloy portion is adjacent to the aluminum alloy portion and includes an adjacent diffusion region where the Fe content ratio is 1.0 to 3.0% when the Fe content in the steel portion is set to 100%. The thickness of the diffusion region adjacent to the aluminum alloy portion, obtained by performing glow discharge emission analysis in the thickness direction of the diffusion layer, is 19.5 to 25.0 μm. Joints and connections.
[0018] [2] Steel parts and, Aluminum alloy part, The system comprises a diffusion layer formed between the steel portion and the aluminum alloy portion, The aforementioned steel part is The chemical composition is expressed in mass percent. C: 0.15~0.50%, Si: 0.01~0.50%, Mn: 0.20~1.50%, P: 0.030% or less, S: 0.030% or less, Cr: 0.50~1.50%, Mo: 0.01~0.30%, Al: 0.005~0.060%, N: 0.020% or less, and, Contains O: 0.0050% or less, Furthermore, it contains one or more elements selected from the groups consisting of Group 1 and Group 2, with the remainder being Fe and impurities. The aforementioned aluminum alloy part is The chemical composition is expressed in mass percent. Cu: 0.80~1.30%, Si: 11.00~13.00%, Mg: 0.70~1.30%, Ni: 0.80~1.50%, Zn: 0.15% or less, Fe: 0.80% or less, Mn: 0.15% or less, Ti: 0.20% or less, and, It contains Cr: 0.10% or less, with the remainder consisting of Al and impurities. The aforementioned diffusion layer is The aluminum alloy portion is adjacent to the aluminum alloy portion and includes an adjacent diffusion region where the Fe content ratio is 1.0 to 3.0% when the Fe content in the steel portion is set to 100%. The thickness of the diffusion region adjacent to the aluminum alloy portion, obtained by performing glow discharge emission analysis in the thickness direction of the diffusion layer, is 19.5 to 25.0 μm. Joints and connections. [Group 1] Cu: 0.40% or less, Ni: 0.40% or less, Sn: 0.100% or less, Ti: 0.050% or less, Nb: 0.050% or less, and, B: Select one or more from the group consisting of 0.0050% or less. [Group 2] Ca: 0.0050% or less, and, One or more selected from the group consisting of Mg: 0.0050% or less.
[0019] [3] [2] The joint described above, The steel part contains the first group, Joints and connections.
[0020] [4] A joint described in [2] or [3], The steel part contains the second group, Joints and connections.
[0021] The joint according to this embodiment will be described in detail below. Unless otherwise specified, the "%" in relation to elements refers to mass %.
[0022] [Connection and Joint Configuration] Figure 1 is a perspective view showing an example of a joint according to this embodiment. Referring to Figure 1, the joint 1 comprises a steel part 10, an aluminum alloy part 20, and a diffusion layer 30. The diffusion layer 30 is positioned between the steel part 10 and the aluminum alloy part 20. The diffusion layer 30 corresponds to the joint portion between the steel part 10 and the aluminum alloy part 20. The steel part 10, the aluminum alloy part 20, and the diffusion layer 30 will be described below.
[0023] [Steel Department 10] The chemical composition of the steel part 10 is as follows (by mass%): C: 0.15-0.50%, Si: 0.01-0.50%, Mn: 0.20-1.50%, P: 0.030% or less, S: 0.030% or less, Cr: 0.50-1.50%, Mo: 0.01-0.30%, Al: 0.005-0.060%, N: 0.020% or less, and O: 0.0050% or less, with the remainder being Fe and impurities.
[0024] Carbon (C) increases the strength of the steel part 10. The preferred lower limit of the C content is 0.16%, and more preferably 0.17%. The preferred upper limit of the C content is 0.48%, and more preferably 0.46%.
[0025] Silicon (Si) deoxidizes the steel during the steelmaking process of steel manufacturing. Si further increases the strength of the steel part 10. The preferred lower limit of the Si content is 0.02%, and more preferably 0.03%. The preferred upper limit of the Si content is 0.45%, and more preferably 0.40%.
[0026] Manganese (Mn) increases the strength of the steel part 10. The preferred lower limit of the Mn content is 0.25%, and more preferably 0.30%. The preferred upper limit of the Mn content is 1.20%, and more preferably 0.90%.
[0027] Phosphorus (P) is an impurity. P segregates at grain boundaries, reducing the workability of the steel part 10. The preferred upper limit for P content is 0.025%, and more preferably 0.020%. A lower P content is preferable, but excessive reduction of the P content increases manufacturing costs. Therefore, the preferred lower limit for P content is greater than 0%, more preferably 0.001%, and even more preferably 0.002%.
[0028] Sulfur (S) is an impurity. S segregates at grain boundaries or forms Mn sulfides, reducing the workability of the steel part 10. The preferred upper limit for S content is 0.025%, and more preferably 0.020%. A lower S content is preferable, but excessive reduction of S content increases manufacturing costs. Therefore, the preferred lower limit for S content is greater than 0%, more preferably 0.001%, and even more preferably 0.002%.
[0029] Chromium (Cr) is dissolved in the solid solution to increase the strength of the steel part 10. The preferred lower limit of the Cr content is 0.55%, and more preferably 0.60%. The preferred upper limit of the Cr content is 1.40%, and more preferably 1.30%.
[0030] Molybdenum (Mo) increases the strength of the steel part 10 by solid solution or by forming precipitates. The preferred lower limit of the Mo content is 0.02%, and more preferably 0.05%. The preferred upper limit of the Mo content is 0.25%, and more preferably 0.20%.
[0031] Aluminum (Al) deoxidizes steel during the steelmaking process in the manufacturing of steel. The preferred lower limit of the Al content is 0.010%, and more preferably 0.015%. The preferred upper limit of the Al content is 0.050%, and more preferably 0.040%.
[0032] Nitrogen (N) is an impurity. N reduces the workability of the steel part 10. The preferred upper limit for the N content is 0.015%, and more preferably 0.010%. It is preferable to have as low an N content as possible, but excessive reduction of the N content increases manufacturing costs. Therefore, the preferred lower limit for the N content is greater than 0%, more preferably 0.001%, and even more preferably 0.002%.
[0033] Oxygen (O) is an impurity. O forms oxides, reducing the strength of the steel part 10. The preferred upper limit for the O content is 0.0045%, and more preferably 0.0040%. A lower O content is preferable, but excessive reduction of the O content increases manufacturing costs. Therefore, the preferred lower limit for the O content is greater than 0%, more preferably 0.0001%, and even more preferably 0.0010%.
[0034] The remainder of the steel part 10 consists of Fe and impurities. Here, impurities are substances that are unintentionally included when the steel material, which is the raw material for the steel part 10, is manufactured industrially, from the ore, scrap, or the manufacturing environment, and are acceptable as long as they do not adversely affect the steel part 10 according to this embodiment.
[0035] The chemical composition of the steel part 10 may further include one or more substances selected from the groups consisting of Group 1 and Group 2 in place of a portion of Fe. [Group 1] Cu: 0.40% or less, Ni: 0.40% or less, Sn: 0.100% or less, Ti: 0.050% or less, Nb: 0.050% or less, and, B: Select one or more from the group consisting of 0.0050% or less. [Group 2] Ca: 0.0050% or less, and, One or more selected from the group consisting of Mg: 0.0050% or less.
[0036] The first group of elements, copper (Cu), nickel (Ni), tin (Sn), titanium (Ti), niobium (Nb), and boron (B), are optional elements and may not be included. In other words, the content of each of these elements may be 0%. If included, each of these elements increases the strength of the steel part 10. Therefore, the Cu content is 0-0.40%, and if included, it is 0.40% or less. The Ni content is 0-0.40%, and if included, it is 0.40% or less. The Sn content is 0-0.100%, and if included, it is 0.100% or less. The Ti content is 0-0.050%, and if included, it is 0.050% or less. The Nb content is 0-0.050%, and if included, it is 0.050% or less. The B content is 0-0.0050%, and if included, it is 0.0050% or less.
[0037] The preferred lower limit for the Cu content is 0.01%, and more preferably 0.05%. The preferred upper limit for the Cu content is 0.35%, and more preferably 0.30%. The preferred lower limit for the Ni content is 0.01%, and more preferably 0.05%. The preferred upper limit for the Ni content is 0.35%, and more preferably 0.30%. The preferred lower limit for the Sn content is 0.001%, more preferably 0.002%, and even more preferably 0.005%. The preferred upper limit for the Sn content is 0.080%, and even more preferably 0.060%. The preferred lower limit for the Ti content is 0.001%, and more preferably 0.005%. The preferred upper limit for the Ti content is 0.045%, and more preferably 0.040%. The preferred lower limit for the Nb content is 0.001%, and more preferably 0.005%. The preferred upper limit for the Nb content is 0.045%, and more preferably 0.040%. The preferred lower limit for the B content is 0.0001%, and more preferably 0.0005%. The preferred upper limit for the B content is 0.0045%, and more preferably 0.0040%.
[0038] Calcium (Ca) and magnesium (Mg), which belong to the second group, are optional elements and do not need to be included. In other words, the content of each of these elements may be 0%. If included, both of these elements refine sulfides and improve the workability of the steel. Therefore, the Ca content is 0 to 0.0050%, and if included, it is 0.0050% or less. The Mg content is 0 to 0.0050%, and if included, it is 0.0050% or less. The preferred lower limit for the Ca content is 0.0001%, and more preferably 0.0005%. The preferred upper limit for the Ca content is 0.0045%, and more preferably 0.0040%. The preferred lower limit for the Mg content is 0.0001%, and more preferably 0.0005%. The preferred upper limit for the Mg content is 0.0045%, and more preferably 0.0040%.
[0039] [Aluminum alloy part 20] The chemical composition of the aluminum alloy part 20 is as follows (by mass%): Cu: 0.80-1.30%, Si: 11.00-13.00%, Mg: 0.70-1.30%, Ni: 0.80-1.50%, Zn: 0.15% or less, Fe: 0.80% or less, Mn: 0.15% or less, Ti: 0.20% or less, and Cr: 0.10% or less, with the remainder being Al and impurities.
[0040] Copper (Cu) dissolves in the α-Al phase of the aluminum alloy 20, increasing its strength. Cu further combines with Al to form precipitates, further increasing the strength of the aluminum alloy 20. However, if the Cu content is too high, the mass of the aluminum alloy 20 increases. Therefore, the Cu content is between 0.80 and 1.30%. The preferred lower limit for the Cu content is 0.90%, and more preferably 1.00%. The preferred upper limit for the Cu content is 1.20%, and more preferably 1.10%.
[0041] Silicon (Si) forms fine primary Si and eutectic Si particles within the aluminum alloy portion 20. This increases the strength of the aluminum alloy portion 20. However, if the Si content is too high, excessive Si precipitates are formed, reducing the workability of the aluminum alloy portion 20. Therefore, the Si content is 11.00 to 13.00%. The preferred lower limit for the Si content is 11.30%, and more preferably 11.60%. The preferred upper limit for the Si content is 12.70%, and more preferably 12.40%.
[0042] Magnesium (Mg) dissolves in the α-Al phase of the aluminum alloy part 20, increasing its strength. Therefore, the Mg content is 0.70-1.30%. The preferred lower limit of the Mg content is 0.80%, and more preferably 0.90%. The preferred upper limit of the Mg content is 1.20%, and more preferably 1.10%.
[0043] Nickel (Ni) forms an intermetallic compound with Al, increasing the strength of the aluminum alloy part 20. Therefore, the Ni content is 0.80-1.50%. The preferred lower limit for the Ni content is 0.90%, and more preferably 1.00%. The preferred upper limit for the Ni content is 1.40%, and more preferably 1.30%.
[0044] Zinc (Zn) reduces the corrosion resistance of the aluminum alloy part 20. Furthermore, Zn promotes crack formation during the casting of the aluminum alloy. For this reason, the Zn content is 0.15% or less. A low Zn content is preferable. However, excessive reduction of the Zn content increases manufacturing costs. Therefore, the preferred lower limit of the Zn content is greater than 0%, more preferably 0.01%, and even more preferably 0.02%. The preferred upper limit of the Zn content is 0.14%, and even more preferably 0.13%.
[0045] Iron (Fe) suppresses galling between the alloy and the mold during the casting of aluminum alloys. Furthermore, Fe improves the castability of the aluminum alloy. However, excess Fe forms intermetallic compounds, reducing the strength of the aluminum alloy portion 20. Therefore, the Fe content should be 0.80% or less. The preferred lower limit of the Fe content is greater than 0%, more preferably 0.10%, and even more preferably 0.20%. The preferred upper limit of the Fe content is 0.70%, and even more preferably 0.60%.
[0046] Manganese (Mn) forms intermetallic compounds such as Al-Mn-Si and Al-Fe-Mn-Si, increasing the strength of the aluminum alloy part 20. However, if the Mn content is too high, a large amount of coarse precipitates will be formed. In this case, the strength of the aluminum alloy part 20 will actually decrease. Therefore, the Mn content should be 0.15% or less. The preferred lower limit of the Mn content is greater than 0%, more preferably 0.01%, and even more preferably 0.05%. The preferred upper limit of the Mn content is 0.13%, and even more preferably 0.11%.
[0047] Titanium (Ti) refines the crystal grains, increasing the strength of the aluminum alloy part 20. However, if the Ti content is too high, coarse Al-Ti precipitates will form. In this case, the strength of the aluminum alloy part 20 will decrease. Therefore, the Ti content should be 0.20% or less. The preferred lower limit of the Ti content is greater than 0%, more preferably 0.01%, and even more preferably 0.02%. The preferred upper limit of the Ti content is 0.18%, and even more preferably 0.16%.
[0048] Chromium (Cr) enhances the wear resistance of the aluminum alloy part 20. However, if the Cr content is too high, it reduces the machinability of the aluminum alloy part 20. Therefore, the Cr content is 0.10% or less. The preferred lower limit of the Cr content is greater than 0%, more preferably 0.01%, and even more preferably 0.02%. The preferred upper limit of the Cr content is 0.09%, and even more preferably 0.08%.
[0049] The remainder of the aluminum alloy part 20 consists of Al and impurities. Here, impurities are substances that are introduced unintentionally during the industrial manufacturing of the aluminum alloy material, which is the material for the aluminum alloy part 20, from the raw materials or the manufacturing environment, and are acceptable within a range that does not adversely affect the aluminum alloy part 20 according to this embodiment.
[0050] [Method for measuring the chemical composition of steel part 10] The chemical composition of the steel part 10 can be measured using a well-known component analysis method in accordance with JIS G0321:2017. Specifically, chips are collected from the inside of the steel part 10 to a depth of 1 mm or more from the surface using a drill. The collected chips are dissolved in acid to obtain a solution. Elemental analysis of the chemical composition is performed on the solution using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry). The C and S content is determined by a well-known high-frequency combustion method (combustion-infrared absorption method). The N content is determined using a well-known inert gas melting-thermal conductivity method. The O content is determined using a well-known inert gas melting-infrared absorption method.
[0051] [Method for measuring the chemical composition of the aluminum alloy part 20] The chemical composition of the aluminum alloy part 20 can be measured using a well-known component analysis method in accordance with JIS H1305:2005. Specifically, a test specimen is taken from a depth of 1 mm or more from the surface of the aluminum alloy part 20 using a drill. The test specimen is cylindrical and has a diameter of 12 mm or more. Elemental analysis of the chemical composition is performed on the collected test specimen by emission spectroscopy.
[0052] Furthermore, the content of each element is rounded to the minimum digit of the element content specified in this embodiment, based on the significant figures defined in this embodiment. For example, the carbon content of the steel part 10 is defined to two decimal places. Therefore, the carbon content is the value obtained by rounding the third decimal place of the measured value to two decimal places.
[0053] Similarly, for the carbon content of the steel part 10, the content of other elements besides carbon is determined by rounding the measured value to the minimum digit specified in this embodiment.
[0054] Rounding means that if the fractional part is less than 5, it is rounded down, and if the fractional part is 5 or greater, it is rounded up.
[0055] [Diffusion layer 30] The diffusion layer 30 is formed between the steel part 10 and the aluminum alloy part 20. Figure 2 shows the relationship between the distance in the thickness direction and the Fe and Al concentrations, obtained by performing GDS analysis in the thickness direction (axial direction of the joint 1) of the portion of the joint 1 including the diffusion layer 30.
[0056] Referring to Figure 2, in the diffusion layer 30, the Fe content decreases in the thickness direction from the steel portion 10 to the aluminum alloy portion 20, while the Al concentration increases. If the diffusion layer is made of an intermetallic compound, as described in Patent Document 1, the Fe content ratio in the axial direction should be relatively constant. This is because the chemical composition of the intermetallic compound is constant.
[0057] On the other hand, in the diffusion layer 30, the Fe content and Al content change in the thickness direction. Therefore, in the diffusion layer 30 formed between the steel part 10 that satisfies the above chemical composition and the aluminum alloy part 20 that satisfies the above chemical composition, there are almost no intermetallic compounds. The diffusion layer 30 is formed by the diffusion of Fe from the steel part 10 toward the aluminum alloy part 20, and the diffusion of Al from the aluminum alloy part 20 toward the steel part 10.
[0058] Figure 3 shows the relationship between the distance (μm) in the thickness direction (axial direction of the joint 1) and the Fe content ratio (%) in the diffusion layer 30. Here, the Fe content ratio (%) refers to the ratio (%) of the Fe content at the corresponding position (corresponding distance in the thickness direction) of the diffusion layer 30, when the Fe content of the steel part 10 is set to 100%. The length in the thickness direction from position D10 to position D20 in Figure 3 corresponds to the thickness (μm) of the diffusion layer 30.
[0059] Referring to Figure 3, the region of the diffusion layer 30 adjacent to the aluminum alloy portion 20, where the Fe content ratio is 1.0 to 3.0%, is defined as the aluminum alloy portion adjacent diffusion region 32. The aluminum alloy portion adjacent diffusion region 32 is the region of the diffusion layer 30 that includes an inflection point where the Fe content ratio decreases from the steel portion 10 towards the aluminum alloy portion 20 and then becomes constant.
[0060] [Regarding the thickness of the diffusion region 32 adjacent to the aluminum alloy part] Figure 4 shows the relationship between the tensile strength (MPa) of the joint 1 and the thickness of the diffusion region 32 adjacent to the aluminum alloy part. Referring to Figure 4, if the thickness of the diffusion region 32 adjacent to the aluminum alloy part is less than 19.5 μm, or if the thickness exceeds 25.0 μm, sufficient tensile strength cannot be obtained in the joint 1. Therefore, the thickness of the diffusion region 32 adjacent to the aluminum alloy part is between 19.5 and 25.0 μm. The preferred lower limit of the diffusion region 32 adjacent to the aluminum alloy portion is 20.0 μm, more preferably 20.5 μm, and even more preferably 21.0 μm. The preferred upper limit of the diffusion region 32 adjacent to the aluminum alloy portion is 24.5 μm, more preferably 24.0 μm, and even more preferably 23.5 μm.
[0061] [Method for measuring the thickness of the adjacent diffusion region 32 in the aluminum alloy section] The thickness of the diffusion region 32 adjacent to the aluminum alloy portion of the joint 1 is determined by the following method.
[0062] A 3 mm thick plate-shaped test specimen is prepared by cutting the joint 1 perpendicular to its axial direction (the thickness direction of the diffusion layer 30). Here, the cut surface of the plate-shaped test specimen is called the main surface. The plate-shaped test specimen is taken so that the diffusion layer 30 is positioned at the center of the plate-shaped test specimen in the thickness direction (corresponding to the axial direction of the joint 1). GDS analysis is performed in the thickness direction from the center of the main surface of the plate-shaped test specimen. Specifically, using a high-frequency glow emission spectrometer (GD-OES), the elemental concentration in the thickness direction is measured by applying a power output of 25 W with the plate-shaped test specimen as the cathode in an argon atmosphere (Ar pressure: 0.27 MPa). The elements to be measured are C, O, Si, Mn, Cu, Cr, Ni, Fe, Mg, Al, V, Ti, and Zn. The measurement area is a circle with a diameter of 10 mm (10 mmφ), the measurement time is 1600 seconds, and the measurement interval is 0.3 seconds. Based on the above measurements, the spectra of Fe and Al shown in Figure 2 were obtained.
[0063] Using the obtained glow emission spectrum of Fe, a graph is created as shown in Figure 3, with the Fe content of the steel part 10, obtained by the chemical composition measurement method of the steel part 10 described above, set to 100%, and the vertical axis representing the Fe content ratio (%) and the horizontal axis representing the axial distance (μm) of the joint 1. Based on the Fe content ratio in the created graph, the thickness of the diffusion region 32 adjacent to the aluminum alloy part is defined as follows.
[0064] Thickness of the diffusion region 32 adjacent to the aluminum alloy part: Axial distance (μm) for Fe content ratios in the range of 1.0 to 3.0% The Fe content ratio (%) is defined as the ratio of the Fe content in the adjacent diffusion region 32 of the aluminum alloy to the Fe content in the steel part 10, where the Fe content in the steel part 10 by mass is set to 100%, and is given by the following formula. Fe content ratio (%) = Fe content in mass % of the adjacent diffusion region 32 of the aluminum alloy part / Fe content in mass % of the steel part 10 × 100
[0065] [Effects of the joint 1 of this embodiment] In this embodiment, the steel portion 10 of the joint has the chemical composition described above, and the aluminum alloy portion 20 also has the chemical composition described above. Furthermore, the thickness of the diffusion region 32 adjacent to the aluminum alloy portion is 19.5 to 25.0 μm. Therefore, the joint 1 of this embodiment has excellent strength.
[0066] [Applications of the joint 1 of this embodiment] The joint 1 of this embodiment is suitable for applications requiring excellent strength. For example, the joint 1 of this embodiment is suitable as a mechanical structural component in automobiles and industrial machinery. However, the joint 1 of this embodiment is not limited to mechanical structural components and can be widely applied to applications requiring excellent strength.
[0067] [Shape of the joint 1 in this embodiment] In Figure 1, the joint 1 is cylindrical. However, the shape of the joint 1 is not particularly limited. The joint 1 is not particularly limited in shape as long as it comprises a steel part 10, an aluminum alloy part 20, and a diffusion layer 30.
[0068] [Manufacturing method] An example of a method for manufacturing the joint 1 according to this embodiment will be described. The method for manufacturing the joint 1 described below is just one example for manufacturing the joint 1 according to this embodiment. Therefore, a joint 1 that satisfies the above-described features may be manufactured by a manufacturing method other than the one described below. However, the manufacturing method described below is a preferred example of a method for manufacturing the joint 1 according to this embodiment.
[0069] The manufacturing method for the joint 1 of this embodiment is as follows, for example. (Process 1) Material preparation process (Process 2) Friction bonding process The following describes each step.
[0070] [(Process 1) Material preparation process] In the material preparation process, the steel material that will be used for the steel portion 10 of the joint 1, and the aluminum alloy material that will be used for the aluminum alloy portion 20 are prepared. The steel material and the aluminum alloy material may be manufactured or supplied by a third party.
[0071] [(Process 2) Friction bonding process] In the friction bonding process, steel and aluminum alloy materials are joined by friction bonding to manufacture a joint 1. Figure 5 is a schematic diagram of a friction bonding apparatus. Referring to Figure 5, the friction bonding apparatus 100 comprises clamps 110 and 120, a rotary drive device 130 to which clamp 110 is attached, and a push device 140 attached to clamp 120.
[0072] Clamp 110 secures the aluminum alloy material 20R. Rotary drive device 130 rotates clamp 110, to which the aluminum alloy material 20R is secured, around the central axis of the aluminum alloy material 20R. Clamp 120 is positioned opposite clamp 110. Clamp 120 secures the steel material 10R. At this time, the end face of the steel material 10R is positioned opposite the end face of the aluminum alloy material 20R. Pushing device 140 pushes clamp 120, to which the steel material 10R is secured, toward clamp 110, bringing the steel material 10R secured by clamp 120 into contact with the aluminum alloy material 20R secured by clamp 110, and then pushes it in further. Alternatively, the steel material 10R may be secured to clamp 110 and the aluminum alloy material 20R may be secured to clamp 120. The friction bonding process using the friction bonding device 100 described above includes the following steps. (Step 21) Preparation step (Step 22) Friction step (Process 23) Upset Process The following describes each step.
[0073] [(Step 21) Preparation step] In the preparation step, the aluminum alloy material 20R and the steel material 10R, which are the materials for the joint 1, are fixed to the friction joint device 100. Specifically, the aluminum alloy material 20R is fixed with clamp 110 and the steel material 10R is fixed with clamp 120. At this time, the end face of the aluminum alloy material 20R is positioned opposite the end face of the steel material 10R. Preferably, the aluminum alloy material 20R and the steel material 10R are positioned coaxially.
[0074] [(Step 22) Friction step] In the friction process, the end face of the aluminum alloy material 20R is brought into contact with the end face of the steel material 10R, and the aluminum alloy material 20R is rotated relative to the steel material 10R around its central axis to generate contact heating.
[0075] Specifically, in the preparation process, the aluminum alloy material 20R fixed to the clamp 110 and the steel material 10R fixed to the clamp 120 are positioned separated by a gap. The rotary drive device 130 rotates the aluminum alloy material 20R at rotational speed N. After rotation, the pushing device 140 moves the steel material 10R toward the aluminum alloy material 20R, bringing the end face of the steel material 10R into contact with the end face of the aluminum alloy material 20R. After contact, the pushing device 140 further pushes the steel material 10R toward the aluminum alloy material 20R to adjust the clearance U1 and friction pressure P1.
[0076] The rotational speed N, frictional pressure P1, and push-in allowance U1 in the friction process are as follows. Here, the push-in allowance U1 refers to the amount the steel material 10R is pushed into the aluminum alloy material 20R at the completion of the friction process, assuming that the contact position between the end face of the aluminum alloy material 20R and the end face of the steel material 10R is 0 mm. (Condition 1) Rotational speed N: 1000 rpm or higher (Condition 2) Friction pressure P1: 15 MPa or higher (Condition 3) Approach margin U1: 1.5 mm or more (Condition 4) F1 defined by equation (1) is 5.0 or less. F1=-0.0036N+1 / (0.0257P1)+8.1436 (1)
[0077] If the rotational speed N is less than 1000 rpm, the frictional pressure P1 is less than 15 MPa, or the fringe width U1 is less than 1.5 mm, sufficient frictional heating will not occur. In this case, the thickness of the diffusion region 32 adjacent to the aluminum alloy part will be less than 19.5 μm. Also, if F1 is greater than 5.0, the time required for sufficient frictional heating to occur will be longer. In this case, the thickness of the diffusion region 32 adjacent to the aluminum alloy part will be greater than 25.0 μm. Therefore, in the friction process, the rotational speed N, friction pressure P1, and threading allowance U1 and F1 are adjusted to satisfy conditions 1 to 4.
[0078] [(Process 23) Upset Process] In the upsetting process, first, the relative rotation of the aluminum alloy material 20R with respect to the steel material 10R is stopped. Then, the pressing device 140 further presses the steel material 10R into the aluminum alloy material 20R. This forms the diffusion layer 30.
[0079] The upsetting pressure P2 and the push-in allowance U2 in the upsetting process are as follows. Here, the push-in allowance U2 is defined as the amount the steel material 10R is pushed into the aluminum alloy material 20R at the completion of the upsetting process, assuming that the contact position between the end face of the aluminum alloy material 20R and the end face of the steel material 10R at the start of the upsetting process is 0 mm. (Condition 5) Upset pressure P2: 250 MPa or higher (Condition 6) Approach margin U2: 2.0 mm or more
[0080] If the upset pressure P2 is less than 250 MPa or the fringe allowance U2 is less than 2.0 mm, the thickness of the diffusion region 32 adjacent to the aluminum alloy part will be less than 19.5 mm. If the upset pressure P2 is 250 MPa or more and the fringe allowance U2 is 2.0 mm or more, the thickness of the diffusion region 32 adjacent to the aluminum alloy part will be between 19.5 and 25.0 mm.
[0081] The upper limit of the upset pressure P2 is not particularly limited. However, if the upset pressure P2 is too high, the aluminum alloy part 20 may buckle. Therefore, a preferred upper limit for the upset pressure P2 is 350 MPa.
[0082] Furthermore, there is no upper limit to the fringing allowance U2. This is because, as long as the upset pressure P2 is between 250 and 350 MPa, the thickness of the diffusion region 32 adjacent to the aluminum alloy portion will be between 19.5 and 25.0 mm even if the steel material 10R is pushed into the aluminum alloy material 20R until the steel material 10R and aluminum alloy material 20R have cooled sufficiently (until the pushing stops naturally). When considering improved manufacturing efficiency, the preferred upper limit for the fringing allowance U2 is 8.0 mm. The joint 1 of this embodiment is manufactured through the above process.
[0083] [Other processes] The manufacturing method for the joint in this embodiment may include a machining step after the friction welding step. In the machining step, burrs and the like formed on the joint portion of the joint after the friction welding step are removed by machining to manufacture the final product, the joint. [Examples]
[0084] The effects of the joint of this embodiment will be further explained in detail by the following examples. The conditions in the following examples are just one example of conditions adopted to confirm the feasibility and effects of the joint of this embodiment. Therefore, the joint of this embodiment is not limited to this one example of conditions.
[0085] [Manufacturing process] Steel materials having the chemical compositions shown in Tables 1-1 and 1-2, and aluminum alloy materials having the chemical compositions shown in Table 2 were prepared.
[0086] [Table 1-1]
[0087] [Table 1-2]
[0088] [Table 2]
[0089] A cylindrical steel material and a cylindrical aluminum alloy material were fixed to the clamp of the friction bonding device shown in Figure 5. A friction process was then performed. The rotational speed N, friction pressure P1, flex U1, and F1 during the friction process are shown in Table 3.
[0090] [Table 3]
[0091] After the friction process, an upsetting process was performed. The upsetting pressure P2 and the fray allowance U2 during the upsetting process are shown in Table 3. Through the above process, joints for each test number were manufactured.
[0092] The following evaluation tests were performed on the joints of each test number. (Test 1) Measurement test of the chemical composition of the steel part and the aluminum alloy part (Test 2) Measurement test of the thickness of the diffusion region adjacent to the aluminum alloy part (Test 3) Tensile strength evaluation test The following explains Exams 1 through 3.
[0093] [(Test 1) Measurement test of the chemical composition of the steel part and the chemical composition of the aluminum alloy part] The chemical composition of the steel part 10 and the aluminum alloy part 20 was measured in accordance with the method described in [Method for measuring the chemical composition of the steel part 10 and the aluminum alloy part 20] above. As a result, the chemical composition of the steel part of the joint for each test number is shown in Tables 1-1 and 1-2, and the chemical composition of the aluminum alloy part is shown in Table 2.
[0094] [(Test 2) Measurement test of the thickness of the diffusion region adjacent to the aluminum alloy part] The thickness of the aluminum alloy adjacent diffusion region 32 for each test number was determined in accordance with the method described in [Method for measuring the thickness of the aluminum alloy adjacent diffusion region 32] above. The obtained thicknesses of the aluminum alloy adjacent diffusion regions are shown in the "Aluminum alloy adjacent diffusion region thickness (μm)" column in Table 4.
[0095] [Table 4]
[0096] [(Test 3) Tensile Strength Evaluation Test] The strength of the joints for each test number was evaluated using the following method. A round bar tensile test specimen was prepared by machining (turning) from the center of the cross-section perpendicular to the longitudinal direction of the joint for each test number. The length of the parallel section of the round bar tensile test specimen was set to 80 mm, and the diameter of the parallel section was set to 14 mm. The central axis of the round bar tensile test specimen approximately coincided with the central axis of the joint. The central position in the axial direction of the parallel section corresponded to the joint position of the joint (i.e., the diffusion layer portion).
[0097] Tensile strength (MPa) was obtained by conducting tensile tests on the prepared round bar tensile test specimens at room temperature and in air, in accordance with JIS Z 2241:2011. The obtained tensile strengths are shown in the "Tensile Strength (MPa)" column of Table 4.
[0098] [Evaluation Results] Referring to Tables 1-1, 1-2, and 2-4, the chemical composition of the steel and aluminum alloy parts was appropriate in the joints with test numbers 1-21, and furthermore, the thickness of the diffusion region adjacent to the aluminum alloy part was also appropriate. As a result, the tensile strength was 250 MPa or higher, and excellent strength was obtained even in joints.
[0099] On the other hand, in tests 22 and 23, the rotational speed N during the friction process was low. As a result, the diffusion region adjacent to the aluminum alloy was too thin. Consequently, the tensile strength of the joint was low.
[0100] In tests 24 and 25, the friction pressure P1 during the friction process was low. Therefore, the diffusion region adjacent to the aluminum alloy section was too thin. As a result, the tensile strength of the joint was low.
[0101] In tests 26 and 27, the friction allowance U1 during the friction process was too short. As a result, the adjacent diffusion region of the aluminum alloy was too thin. Consequently, the tensile strength of the joint was low.
[0102] In tests 28 and 29, F1 was too high during the friction process. As a result, the diffusion region adjacent to the aluminum alloy was too thick. Consequently, the tensile strength of the joint was low.
[0103] In tests 30 and 31, the upset pressure P2 during the upset process was too low. As a result, the diffusion region adjacent to the aluminum alloy was too thin. Consequently, the tensile strength of the joint was low.
[0104] In tests 32 and 33, the fray allowance U2 during the upsetting process was too short. Consequently, the adjacent diffusion region of the aluminum alloy was too thin. As a result, the tensile strength of the joint was low.
[0105] The embodiments of this disclosure have been described above. However, the embodiments described above are merely examples for implementing this disclosure. Therefore, this disclosure is not limited to the embodiments described above, and the embodiments described above can be modified as appropriate without departing from the spirit of this disclosure. [Explanation of Symbols]
[0106] 1. Joint 10 Steel Department 20 Aluminum alloy part 30 Diffusion layer 32 Diffusion region adjacent to the aluminum alloy part
Claims
1. Steel parts and, Aluminum alloy part, The system comprises a diffusion layer formed between the steel portion and the aluminum alloy portion, The aforementioned steel part is The chemical composition is expressed in mass percent. C: 0.15-0.50%, Si: 0.01 to 0.50%, Mn: 0.20-1.50%, P: 0.030% or less, S: 0.030% or less, Cr: 0.50-1.50%, Mo: 0.01-0.30%, Al: 0.005-0.060%, N: 0.020% or less, and It contains O: 0.0050% or less, with the remainder consisting of Fe and impurities. The aforementioned aluminum alloy part is The chemical composition is expressed in mass percent. Cu: 0.80 to 1.30%, Si: 11.00-13.00%, Mg: 0.70-1.30%, Ni: 0.80 to 1.50%, Zn: 0.15% or less, Fe: 0.80% or less, Mn: 0.15% or less, Ti: 0.20% or less, It contains Cr: 0.10% or less, with the remainder consisting of Al and impurities. The aforementioned diffusion layer is The aluminum alloy portion is adjacent to the aluminum alloy portion and includes an adjacent diffusion region where the Fe content ratio is 1.0 to 3.0% when the Fe content in the steel portion is set to 100%. The thickness of the diffusion region adjacent to the aluminum alloy portion, obtained by performing glow discharge emission analysis in the thickness direction of the diffusion layer, is 19.5 to 25.0 μm. Joints and connections.
2. Steel parts and, Aluminum alloy part, The system comprises a diffusion layer formed between the steel portion and the aluminum alloy portion, The aforementioned steel part is The chemical composition is expressed in mass percent. C: 0.15-0.50%, Si: 0.01 to 0.50%, Mn: 0.20-1.50%, P: 0.030% or less, S: 0.030% or less, Cr: 0.50-1.50%, Mo: 0.01-0.30%, Al: 0.005-0.060%, N: 0.020% or less, and O: Contains 0.0050% or less, Furthermore, it contains one or more elements selected from the groups consisting of Group 1 and Group 2, with the remainder being Fe and impurities. The aforementioned aluminum alloy part is The chemical composition is expressed in mass percent. Cu: 0.80 to 1.30%, Si: 11.00-13.00%, Mg: 0.70-1.30%, Ni: 0.80 to 1.50%, Zn: 0.15% or less, Fe: 0.80% or less, Mn: 0.15% or less, Ti: 0.20% or less, It contains Cr: 0.10% or less, with the remainder consisting of Al and impurities. The aforementioned diffusion layer is The aluminum alloy portion is adjacent to the aluminum alloy portion and includes an adjacent diffusion region where the Fe content ratio is 1.0 to 3.0% when the Fe content in the steel portion is set to 100%. The thickness of the diffusion region adjacent to the aluminum alloy portion, obtained by performing glow discharge emission analysis in the thickness direction of the diffusion layer, is 19.5 to 25.0 μm. Joints and connections. [Group 1] Cu: 0.40% or less, Ni: 0.40% or less, Sn: 0.100% or less, Ti: 0.050% or less, Nb: 0.050% or less, B: One or more selected from the group consisting of 0.0050% or less. [Group 2] Ca: 0.0050% or less, One or more selected from the group consisting of Mg: 0.0050% or less.
3. A joint according to claim 2, The steel part contains the first group, Joints and connections.
4. A joint according to claim 2, The steel part contains the second group, Joints and connections.