A rapid brazing copper-based filler metal and its preparation method

Abstract

This invention belongs to the field of copper-based brazing filler metal technology, and relates to a rapid brazing copper-based filler metal and its preparation method. The invention provides a rapid brazing copper-based filler metal, which, by mass percentage, consists of 15-40% Mn, 5-10% Ni, 1-8% Sn, 0.5-1% Si, 0.5-1% B, 0.5-1% Nd, 0.1-0.5% Cr, with the balance being Cu. This rapid brazing copper-based filler metal exhibits high strength and good wetting properties. The introduction of Nd improves its performance, and the addition of Si, B, and Cr further enhances its performance.

Description

Technical Field

[0001] This invention belongs to the field of copper-based brazing filler metal technology, and relates to a rapid brazing copper-based filler metal and its preparation method. Background Technology

[0002] Brazing is a welding method in which both the filler metal and the workpiece are heated to their melting temperatures, with the liquid filler metal filling the gaps between the solid workpieces to join the metals. Brazing is an effective method for joining dissimilar metals, but the diverse compositions of dissimilar metals pose challenges to improving the mechanical properties of brazed joints. As a key factor in brazing, the composition of the filler metal directly affects the metallurgical bonding strength of the brazed joint interface. Simultaneously, intermetallic compounds (IMCs) in the joint can cause uneven fiber structure, reducing the shear strength of the joint.

[0003] Cu-Mn-Ni ternary solders have a moderate melting point (approximately 900℃) and a predominantly solid solution microstructure, balancing strength and ductility. Existing techniques involve adding Sn to Cu-Mn-Ni ternary solders to induce lattice distortion in the matrix phase. The lattice constant of the matrix phase gradually increases with increasing Sn content until it remains constant. While Sn effectively lowers the liquidus point of Cu-Mn-Ni ternary solders, increased Sn content also reduces solder strength, widens the melting range, and deteriorates wettability and radiation resistance. Rare earth (RE) elements, as important alloying elements, can refine the alloy microstructure, improve the wettability of the fiber to the substrate, and enhance solder joint performance when added in appropriate amounts. Extensive research and applications have been conducted on this topic. RE elements can refine the solder alloy microstructure and promote interfacial reactions, improving solder joint bonding strength. However, excessive RE elements (>0.3wt%) can lead to the aggregation of RE compounds at the interface, resulting in uneven microstructure in the joint and a significant decrease in bonding strength. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a copper-based solder that balances reduced liquidus point and performance, as well as a method for its preparation.

[0005] To achieve the above objectives, the present invention provides a rapid brazing copper-based filler metal and its preparation method to meet this need in the art.

[0006] On the one hand, the present invention provides a rapid brazing copper-based brazing filler metal, which, by mass percentage, consists of 15-40% Mn, 5-10% Ni, 4-10% Sn, 0.5-1% Si, 0.5-1% B, 0.3-0.5% Nd, 0.1-0.5% Cr, and the balance being Cu.

[0007] Furthermore, the rapid brazing copper-based filler metal provided by the present invention comprises, by mass percentage, 32% Mn, 6% Ni, 10% Sn, 0.8% Si, 0.6% B, 0.3% Nd, 0.4% Cr, and the balance being Cu.

[0008] Furthermore, in the rapid brazing copper-based filler metal provided by the present invention, the purity of any element is not less than 99.99 wt%.

[0009] On the other hand, the present invention relates to a method for preparing a rapid brazing copper-based solder, comprising: melting and holding Cu and Mn to obtain a first liquid alloy, and melting and holding Ni, Sn, Nd and Cr to obtain a second liquid alloy; The second liquid alloy, Si, and B are added sequentially to the first liquid alloy, and then the elements are homogenized under a protective atmosphere. After cooling, the rapid brazing copper-based filler metal is obtained.

[0010] On the other hand, the present invention relates to the application of the aforementioned rapid brazing copper-based filler metal in brazing.

[0011] Furthermore, in the application provided by the present invention, the process conditions for brazing the rapid brazing copper-based filler metal include: a holding temperature of 840~880℃ and a holding time of 0.25~30min.

[0012] Furthermore, in the applications provided by this invention, the rapid brazing copper-based filler metal is used for brazing under a protective atmosphere or a vacuum atmosphere.

[0013] Furthermore, in the application provided by the present invention, the rapid brazing copper-based filler metal is used for brazing MnCuAl alloy and SUS430 stainless steel.

[0014] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages: Introducing Sn into Cu-Mn-Ni ternary solders can effectively lower the liquidus point, but low Sn content has little effect on reducing the liquidus point, while high Sn content leads to a decline in various solder properties. This invention introduces Nd into Cu-Mn-Ni-Sn solders to improve their performance; however, low Nd content has little effect on performance improvement, while high Nd content leads to the aggregation of RE compounds at the interface, resulting in uneven microstructure and a significant decrease in bonding strength. This invention further introduces Si, B, and Cr. The introduction of these three elements has no significant effect on the liquidus point, but when used for brazing MnCuAl alloys to SUS430 stainless steel, it effectively inhibits the excessive growth of RE compounds and significantly improves bonding strength and wetting properties. Detailed Implementation

[0015] The technical solution of the present invention will be described below with reference to embodiments. However, the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental methods and detection methods described in each embodiment are conventional methods; unless otherwise specified, the reagents and materials can be purchased commercially. Example 1

[0016] This embodiment provides a rapid brazing copper-based filler metal.

[0017] Raw materials: by mass percentage, they consist of 15% Mn, 5% Ni, 4% Sn, 0.5% Si, 0.5% B, 0.3% Nd, 0.1% Cr, with the balance being Cu. The purity of all raw materials is 99.99 wt%.

[0018] Cu and Mn were melted and held at 1300°C under argon atmosphere to obtain a first liquid alloy. Ni, Sn, Nd and Cr were melted and held at 1300°C under argon atmosphere to obtain a second liquid alloy. The second liquid alloy, Si and B were added to the first liquid alloy in sequence, and then held at 1300°C for 30 min under argon atmosphere for element homogenization. After the holding period, the mixture was cooled to 120°C under argon atmosphere and finally cooled to room temperature to obtain a rapid brazing copper-based solder. Example 2

[0019] This embodiment provides a rapid brazing copper-based filler metal.

[0020] Raw materials: by mass percentage, they consist of 25% Mn, 7% Ni, 7% Sn, 0.8% Si, 0.8% B, 0.4% Nd, 0.3% Cr, with the balance being Cu. The purity of all raw materials is 99.99 wt%.

[0021] The preparation method is the same as in Example 1. Example 3

[0022] This embodiment provides a rapid brazing copper-based filler metal.

[0023] Raw materials: by mass percentage, they consist of 32% Mn, 6% Ni, 10% Sn, 0.8% Si, 0.6% B, 0.3% Nd, 0.4% Cr, with the balance being Cu. The purity of all raw materials is 99.99 wt%.

[0024] The preparation method is the same as in Example 1. Example 4

[0025] This embodiment provides a rapid brazing copper-based filler metal.

[0026] Raw materials: by mass percentage, they consist of 40% Mn, 10% Ni, 10% Sn, 1% Si, 0.6% B, 0.5% Nd, 0.5% Cr, with the balance being Cu. The purity of all raw materials is 99.99 wt%.

[0027] Comparative Example 1 This comparative example is the same as Example 3, except that it does not contain Si.

[0028] Comparative Example 2 This comparative example is the same as Example 3, except that it does not contain Cr.

[0029] Comparative Example 3 This comparative example is the same as Example 3, except that it does not contain Si, B and Cr. Example 4

[0030] This embodiment provides the liquid point measurement results of the brazing filler metal.

[0031] The liquidus point of the solder was measured using differential scanning calorimetry (DSC), with the peak temperature being the liquidus point of the solder. T 1. The measurement results are shown in Table 1.

[0032] Table 1 Liquidation point of brazing filler metal

[0033] As shown in Table 1, the liquidus point of Cu-34Mn-6Ni (wt%) brazing filler metal is 903℃, which is higher than the melting point of the base material MnCuAl alloy (888℃), making it unsuitable as a brazing filler metal for its brazing connections. Comparative Examples 1-3 show that the liquidus point is mainly affected by the Sn content, while the addition of Si, B, and Cr has no significant effect on the change in liquidus point. p <0.05). Example 5

[0034] This embodiment provides performance test results of the brazing filler metal used for rapid brazing.

[0035] Rapid brazing was performed on the copper-based brazing filler metals provided in Examples 1-3 and Comparative Examples 1-3. The base materials used for fiber brazing were Mn-44Cu-1.5Al (wt%) and SUS430 stainless steel, with hardnesses of 146HV and 195HV, respectively. The brazed joints were assembled in a sandwich structure, with the stainless steel plate at the bottom and the copper alloy plate on top. The fiber filler was placed between the two base materials, and an agent was applied to the outer perimeter of the copper plate at the interface with the stainless steel plate. Induction brazing was used to prepare the welded joints. The assembled samples were placed inside an induction coil, heated to a preset temperature of 880℃, held for 15 seconds, and then air-cooled to room temperature. The induction heating frequency was 20kHz, and the power was 30kW. The shear test results and wetting performance test results are shown in Table 2.

[0036] Table 2. Results of shear test and wetting performance test

[0037] Table 2 shows that the introduction of Nd can improve its performance, but a low amount of Nd (0.1 wt%) has little effect on performance improvement, while a high amount of Nd (0.3 wt%) leads to the aggregation of RE compounds at the interface, resulting in uneven microstructure in the joint and a significant decrease in bonding strength. Further introduction of Si, B, and Cr has no significant effect on the liquidus point of the solder. p <0.05), but when used for brazing MnCuAl alloys with SUS430 stainless steel, it can effectively inhibit the excessive growth of RE compounds and effectively improve the bond strength and wetting properties. The absence of any of the elements Si, B and Cr will lead to a weakening of the shear strength of the weld joint, especially the absence of Cr.

[0038] As described above, the basic principles, main features, and advantages of the present invention have been well described. The above embodiments and specifications are merely descriptions of preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A rapid brazing copper-based filler metal, characterized in that, It consists of 15-40% Mn, 5-10% Ni, 4-10% Sn, 0.5-1% Si, 0.5-1% B, 0.3-0.5% Nd, 0.1-0.5% Cr, and the balance Cu by mass percentage. The purity of any elemental raw material used to prepare the rapid brazing copper-based filler metal shall not be less than 99.99 wt%; The process conditions for using the rapid brazing copper-based filler metal for brazing include: a holding temperature of 840~880℃ and a holding time of 0.25~30min.

2. The rapid brazing copper-based filler metal according to claim 1, characterized in that, It consists of 32% Mn, 6% Ni, 10% Sn, 0.8% Si, 0.6% B, 0.3% Nd, 0.4% Cr, and the balance Cu by mass percentage.

3. The method for preparing the rapid brazing copper-based filler metal according to claim 1, characterized in that, include: Cu and Mn are melted and held at a certain temperature to obtain a first liquid alloy, and Ni, Sn, Nd and Cr are melted and held at a certain temperature to obtain a second liquid alloy; The second liquid alloy, Si, and B are added sequentially to the first liquid alloy, and then the elements are homogenized under a protective atmosphere. After cooling, the rapid brazing copper-based filler metal is obtained.

4. The application of the rapid brazing copper-based filler metal according to claim 1 in brazing, characterized in that, The rapid brazing copper-based filler metal is used for brazing MnCuAl alloy with SUS430 stainless steel.

5. The application according to claim 4, characterized in that, The rapid brazing copper-based filler metal is used for brazing under a protective atmosphere or vacuum atmosphere.

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