Nickel-containing copper-based solder for stainless steel brazing, and preparation method therefor and use thereof

Abstract

A nickel-containing copper-based solder for stainless steel brazing. The solder comprises the following component elements in percentages by weight: 7-13% of tin, 0.5-3.5% of nickel, 0.02-0.4% of phosphorus, 0.0001-0.5% of X and the balance of copper, for a total of 100%, wherein X is selected from at least one of iron, chromium, zinc, titanium and manganese. By means of adding specific elements and controlling the content of the specific elements, the salt spray corrosion resistance of the nickel-containing copper-based solder for stainless steel brazing is improved after synergistic effects in multiple aspects, thereby ensuring the use of stainless steel pipelines or valves under harsh coastal conditions. The present invention further relates to a preparation method for and the use of the nickel-containing copper-based solder for stainless steel brazing.

Description

Nickel-containing copper-based filler metal for stainless steel brazing and preparation method and application thereof

[0001] The present application claims priority to the patent application No. 2024110501344 filed on July 31, 2024 in the State Intellectual Property Office of China, and entitled "Nickel-containing copper-based filler metal for stainless steel brazing and preparation method and application thereof". TECHNICAL FIELD

[0002] The present application relates to the technical field of chemical industry, in particular to a nickel-containing copper-based filler metal for stainless steel brazing and a preparation method and application thereof. BACKGROUND

[0003] With the increasing demand for materials with good comprehensive performance in modern industry, the existing stainless steel products have poor salt mist corrosion resistance, which has been difficult to meet the application in harsh conditions such as coastal areas.

[0004] Therefore, it is urgent to study a brazing filler metal with excellent salt mist corrosion resistance for reducing the above welding defects. SUMMARY

[0005] The main purpose of the present application is to provide a nickel-containing copper-based filler metal for stainless steel brazing and a preparation method and application thereof, so as to solve the problem of poor salt mist corrosion resistance of the stainless steel-bronze brazing filler metal joint in the prior art.

[0006] In order to achieve the above purpose, according to one aspect of the present application, a nickel-containing copper-based filler metal for stainless steel brazing is provided, which comprises the following component elements in percentage by weight:

[0007] tin 7% to 13%, nickel 0.5% to 3.5%, phosphorus 0.02% to 0.4%, X 0.0001% to 0.5%, the balance being copper, and the total being 100%; wherein X is selected from one or more of iron, chromium, zinc, titanium and manganese.

[0008] Further, the nickel-containing copper-based filler metal for stainless steel brazing comprises the following component elements: tin 11% to 13%, nickel 1.5% to 2%, phosphorus 0.05% to 0.2%, X 0.001% to 0.5%, the balance being copper, and the total being 100%.

[0009] Further, tin 11% to 13%, nickel 1.5% to 2%, phosphorus 0.05% to 0.1%, X 0.001% to 0.5%, the balance being copper, and the total being 100%.

[0010] Further, X includes iron, chromium, zinc, titanium and manganese.

[0011] Further, the weight percentage of iron in the solder is 0.0001-0.5%, the weight percentage of chromium in the solder is 0.0001-0.5%, and the weight percentage of zinc in the solder is 0.0001-0.5%; the weight percentage of titanium in the solder is 0.0001-0.5%, and the weight percentage of manganese in the solder is 0.0001-0.5%.

[0012] Further, the weight percentage of iron in the solder is 0.01-0.2%, the weight percentage of chromium in the solder is 0.0001-0.3%, and the weight percentage of zinc in the solder is 0.0001-0.5%; the weight percentage of titanium in the solder is 0.0001-0.005%, and the weight percentage of manganese in the solder is 0.0001-0.3%.

[0013] Further, the nickel is selected from one or more of the following: elemental nickel, copper-nickel binary alloy, chromium-nickel binary alloy, nickel-phosphorus binary alloy, and chromium-nickel-phosphorus ternary alloy.

[0014] Further, the nickel is selected from one or more of the following: BNi7 alloy and / or BNi6 alloy.

[0015] Further, the phosphorus is selected from one or more of the following: copper-phosphorus binary alloy, BNi7 alloy and / or BNi6 alloy.

[0016] Further, the iron is selected from one or more of the following: elemental iron, copper-iron binary alloy, and ternary alloy.

[0017] Further, the chromium is selected from one or more of the following: copper-chromium binary alloy and / or chromium-nickel-phosphorus ternary alloy.

[0018] Further, the zinc is selected from one or more of the following: elemental zinc and / or copper-zinc binary alloy.

[0019] Further, the titanium is selected from one or more of the following: copper-titanium binary alloy.

[0020] Further, the manganese is selected from one or more of the following: elemental manganese and / or copper-manganese binary alloy.

[0021] According to another aspect of the present application, a preparation method of the above-mentioned nickel-containing copper-based solder for stainless steel brazing is provided, and the preparation method comprises the following steps:

[0022] S1: ingredients are prepared according to the proportion of each component in the nickel-containing copper-based solder for stainless steel brazing to obtain a mixture;

[0023] S2: the mixture is sequentially subjected to melting and casting to obtain an ingot;

[0024] S3: the ingot is sequentially subjected to homogenization annealing and hot extrusion treatment to obtain a rod;

[0025] S4, performing first drawing treatment and first annealing treatment on the wire rod to obtain first annealed material;

[0026] S5, performing second drawing treatment on the first annealed material to obtain the wire-shaped stainless steel brazing nickel-containing copper-based filler material.

[0027] Further, in step S2, after the smelting treatment, slag removal, standing, and then casting are performed.

[0028] Further, step S5 further comprises: forming a ring-shaped piece from the wire-shaped stainless steel brazing nickel-containing copper-based filler material, and performing second annealing treatment on the ring-shaped piece to obtain the stainless steel brazing nickel-containing copper-based filler material.

[0029] Further, in step S1, the smelting temperature is 1120-1200℃, and the smelting time is 2-3h.

[0030] Further, in step S3, the homogenizing annealing process comprises: holding the ingot at 600-700℃ for 3-5h.

[0031] Further, in step S4, the first annealing treatment conditions comprise: temperature of 600-700℃, and time of 3-5h.

[0032] Further, in step S4, the first drawing treatment and the first annealing treatment are sequentially cycled for 3-7 times.

[0033] Further, in step S5, the second annealing treatment conditions comprise: temperature of 150-200℃, and time of 0.5-1h.

[0034] According to another aspect of the present application, the application of the above-mentioned stainless steel brazing nickel-containing copper-based filler material or the stainless steel brazing nickel-containing copper-based filler material prepared according to the above-mentioned preparation method in the brazing of stainless steel products is provided.

[0035] By applying the technical solution of the present application, a stainless steel brazing nickel-containing copper-based filler material controls the content of Sn element in the filler material at 7-13%, the content of Ni element at 0.5-3.5%, and the content of P at ≤0.4%, and controls the content of other components X (iron element, chromium element, zinc element, titanium element, and manganese element) at 0.0001%-0.5%. By adding specific elements and controlling the content of specific elements, the salt mist corrosion resistance is significantly improved on the basis of ensuring excellent performance of the filler material in wire drawing forming and filler material strength, etc., and the application of stainless steel pipelines / valves in harsh conditions such as coastal areas is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0036] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The illustrations, together with the description, serve to explain the application, but do not limit the application. In the drawings:

[0037] Figure 1 shows the SEM morphology of the stainless steel interface of the brazing piece of Example 1 of the present application after neutral salt spray test for 1000h;

[0038] Figure 2 shows the SEM morphology of the stainless steel interface of the brazing piece of Example 2 of the present application after neutral salt spray test for 1000h;

[0039] Figure 3 shows the SEM morphology of the stainless steel interface of the brazing piece of Example 3 of the present application after neutral salt spray corrosion test for 1000h;

[0040] Figure 4 shows the SEM morphology of the stainless steel interface of the brazing piece of Comparative Example 1 of the present application;

[0041] Figure 5 shows the SEM morphology of the stainless steel interface of the brazing piece of Comparative Example 1 of the present application in partial enlargement;

[0042] Figure 6 shows the SEM morphology of the solder of Comparative Example 1 of the present application;

[0043] Figure 7 shows the SEM morphology of the solder of Comparative Example 1 of the present application at the front end of the corrosion path (i.e. the place where corrosion starts to occur, and the corrosion amount is small) at the stainless steel interface after neutral salt spray test for 1000h;

[0044] Figure 8 shows the SEM morphology of the solder of Comparative Example 1 of the present application at the middle and rear end of the corrosion path (the corrosion amount is large) at the stainless steel interface after neutral salt spray test for 1000h;

[0045] Figure 9 shows the SEM morphology of the stainless steel interface of the brazing piece of Comparative Example 2 of the present application; DETAILED DESCRIPTION

[0046] It should be noted that the embodiments and features in the present application can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0047] The applicant found in the research of copper-based solder formula that in the traditional copper-based solder BCuSn12P, the Sn content is 11-13%, and the P content is 0.2-0.4%. Due to unreasonable component element ratio, when metallurgical reaction occurs between the stainless steel and the solder, and element mutual diffusion occurs, the P element in the solder diffuses to the surface of the stainless steel, and a P diffusion layer is generated at the interface of the stainless steel, the P content in the diffusion layer is about 0.1-1.0%; the Cu element in the solder diffuses to the surface of the stainless steel, and a Cu diffusion layer is generated at the interface of the stainless steel, the Cu content in the diffusion layer is about 1-7%; especially, the Fe, Cr, Ni and Mn elements at the interface of the stainless steel also diffuse to the solder, and about 1-3% Fe, 3-6% Ni, 0.5-2% Cr and 1-1.5% Mn in the stainless steel interface dissolve into the solder within 5-10 μm, so that the Cr, Ni and Mn element contents at the interface of the stainless steel (the original interface component can be considered as Fe-18Cr-8Ni-1.5Mn) are reduced, the Cu and P element contents are increased, and the interface component is changed into, for example, Fe-16Cr-2Ni-0.5Mn-4Cu-0.3P; the excessive P combines with the diffused Cr and Fe to generate phosphide at the interface, and the Cr content reduction at the interface is aggravated, and the Cr content reduction causes the local corrosion resistance to be reduced. The above phenomenon will cause the following defects: (1) the change of the interface component of the stainless steel, the Ni and Mn are austenite forming elements, and the brazing diffusion causes the Ni and Mn element contents to be reduced, and the austenite at the surface of the substrate within 5-10 μm is changed into ferrite rich in Cu and P elements; (2) due to the interface being ferrite rich in Cu and P elements, the change of the interface component of the stainless steel, and the galvanic corrosion, the ferrite is more susceptible to corrosion, and the solder joint is leaked.

[0048] In order to solve the problems in the prior art, the embodiments of the present application provide a nickel-containing copper-based solder for brazing stainless steel. The nickel-containing copper-based solder for brazing stainless steel comprises the following component elements in percentage by weight: tin 7%-13%, nickel 0.5%-3.5%, phosphorus 0.02%-0.4%, X 0.0001%-0.5%, and the balance being copper, and the total is 100%; wherein X is at least one selected from iron element, chromium element, zinc element, titanium element and manganese element.

[0049] The applicant found in the research that the solid solution content of the Ni element in the CuSn solder is about 0.5-3%, so the corrosion resistance is improved by controlling the Ni content in the solder to be 0.5%-3.5% in use; the Ni element is added to the solder in a specific ratio, so that the diffusion trend of the Ni at the interface of the stainless steel to the solder is reduced; the Ni content at the interface of the stainless steel after welding is equivalent to the Ni content on the surface of the stainless steel, so that the austenite to ferrite transformation is prevented.

[0050] The application finds in the research that when the content of Ni in the solder is lower than 0.5%, the content of Ni at the welding interface and the content of Ni in the stainless steel substrate form a certain concentration difference, and the content of Ni in the stainless steel substrate cannot be obviously improved to diffuse to the welding interface, to further promote the formation of ferrite, and to reduce the salt mist corrosion resistance of the welded joint; when the content of Ni in the solder is higher than 3.5%, too much NiSn and NiP hard particle phases are formed by Ni, Sn and P, which leads to the increase of brittleness and affects the plastic processing; therefore, by adding the above-mentioned specific proportion of 0.5-3.5% of Ni element in the solder, the application can reduce the diffusion trend of Ni in the stainless steel interface to the solder, the content of Ni at the welding interface is equivalent to the content of Ni on the surface of the stainless steel substrate; the transformation of austenite to ferrite is prevented, and the solder also has good strength; when the content of Ni in the solder is preferably 1.5-2.5%, the welding mechanical properties and corrosion resistance effect are best.

[0051] By controlling the content of P element in the solder to be 0.02-0.4%, the application can obviously reduce the content of phosphide generated at the interface of the stainless steel.

[0052] The main components CuSnNi of the solder of the application control the melting range of the solder, by controlling the content of Sn to be 7-13%, the liquidus temperature of the solder is lower than 1040℃, the liquidus range is 980-1040℃, therefore the brazing temperature is controlled to be lower than the melting temperature of copper 1083℃; when the content of Ni element is controlled to be 0.5-3.5%, compared with the CuSn alloy without nickel, the liquidus temperature is slightly increased by 2-10℃, and the liquidus temperature of the solder is still within a certain range from the melting temperature of copper, and the change of the brazing temperature is small.

[0053] The application adds other components X to the solder raw material, which includes at least one of Fe, Cr, Zn, Ti and Mn; the mechanism of each element of the newly added X is described from the aspects of corrosion resistance, solder strength, segregation reduction, wire drawing forming and the like: a trace amount of Fe element added in the solder can be solid-solved in the Cu solid solution, and the solder strength is improved through solid solution strengthening and dispersion precipitation mechanism; a small amount of Fe element has the effect of refining grains, and the alloy strength is improved, but the corrosion resistance is reduced; too much Fe can intensify the segregation structure, and the strength and hardness are improved more, resulting in difficulty in wire drawing; the Cr element added in the solder has similar effects as the Fe element, and in addition to improving the solder strength, the Cr element also plays a role in reducing the diffusion of Cr in the stainless steel matrix; the solder itself has Cr, which can reduce the diffusion of Cr in the stainless steel matrix (similar to Ni), so that the Cr in the stainless steel matrix is sufficient to form a dense Cr oxide film, and the corrosion resistance of the solder joint is further improved; a small amount of Mn added in the solder can improve the toughness of the material, is conducive to wire drawing forming, reduces the diffusion of Mn in the matrix, and is also an austenite forming element, and has a part of the effect of preventing the transformation of austenite into ferrite, but too much Mn can easily absorb gas during smelting, resulting in difficulty in wire drawing; a small amount of Zn added in the solder can improve the fluidity of the alloy liquid, reduce the crystallization range, reduce segregation, reduce corrosion resistance, and has no obvious effect on the strength and hardness of the matrix, but can significantly improve the elongation and simplify the wire drawing forming; a trace amount of Ti element added in the solder as a small precipitate phase provides more nucleation sites for the formation of hard phases, and can improve the solder strength.

[0054] In the application, the weight percentage of the nickel element in the nickel-containing copper-based solder for brazing stainless steel is selected from any value or a range value between any two of 0.5%, 1%, 1.2%, 1.5%, 1.8%, 2.0%, 2.3%, 2.5%, 3%, 3.5%; the weight percentage of the phosphorus element is selected from any value or a range value between any two of 0.02%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%; the weight percentage of the tin element is selected from any value or a range value between any two of 7%, 8%, 9%, 10%, 11%, 12%, 13%; and the weight percentage of the X element (a specific element added) is selected from any value or a range value between any two of 0.0001%, 0.001%, 0.01%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%.

[0055] In the experimental process, the solid-solution content of the Ni element in the CuSn solder is about 1-1.5%, therefore, the applicant controls the Ni content in the solder to be 0.5%-3.5%, and further preferably 1.5%-2.5%, and the corrosion resistance has the best use effect.

[0056] The P content in the solder is controlled at 0.02% to 0.4% in the application, which can significantly reduce the phosphide content generated at the interface of the stainless steel. Since P effectively removes gas and deoxidizes, it also improves the fluidity of the copper liquid, which is a key material in the solder production process. However, P can also increase the formation of network segregation structure, affecting plastic processing, and excessive P can also cause the formation of (Cr, Fe)-P second phase at the interface of the base body, so the P content in the solder base body is preferably 0.05% to 0.2%, and further preferably 0.1% to 0.2%.

[0057] In order to further improve the corrosion resistance, solder strength, reduce segregation, wire forming and other performance, the nickel-containing copper-based solder for stainless steel brazing includes the following component elements: tin 7% to 13%, nickel 1.5% to 2.5%, phosphorus 0.05% to 0.2% (theoretically, the less phosphorus, the better the deaeration and subsequent wire drawing, but in actual process, it is relatively easy to control the phosphorus content at 0.05% to 0.1%, and further control at 0.1% to 0.2%), X 0.0001% to 0.5%, the balance being copper, totaling 100%; wherein X is iron, chromium, zinc, titanium and manganese; wherein the weight percentage of iron in the solder is 0.0001 to 0.5%, the weight percentage of chromium in the solder is 0.0001 to 0.5%, the weight percentage of zinc in the solder is 0.0001 to 0.5%; the weight percentage of titanium in the solder is 0.0001 to 0.5%, and the weight percentage of manganese in the solder is 0.0001 to 0.5%.

[0058] Preferably, in order to further improve the above performance, the weight percentage of iron in the solder is 0.01% to 0.2%, the weight percentage of chromium in the solder is 0.001 to 0.3%, preferably 0.05% to 0.1%; the weight percentage of zinc in the solder is 0.0001 to 0.5%; the weight percentage of titanium in the solder is 0.0001 to 0.005%; and the weight percentage of manganese in the solder is 0.05 to 0.3%.

[0059] As a specific embodiment, the total weight percentage of X in the solder is 0.0001% to 0.5%, wherein X can be selected from iron, chromium, zinc, titanium and manganese (weight ratio of 8-12:3-8:18-22:0.005-0.015:8-12), or X is iron, zinc and manganese (weight ratio of 1:2-4:8-12), or X is iron, chromium, zinc and titanium (weight ratio of 4-6:8-12:25-30:0.3-0.5), or X is chromium, titanium, zinc and manganese (weight ratio of 8-12:4-6:8-12:12-18), or X is iron, chromium, titanium and manganese (weight ratio of 12-18:15-20:0.04-0.06:4-6), or X is chromium, titanium and manganese (weight ratio of 22-27:0.04-0.06:18-22), or X is iron, chromium, zinc and manganese (weight ratio of 8-12:13-17:8-12:8-12), or X is iron, chromium and manganese (weight ratio of 8-12:20-30:8-12).

[0060] In order to further consider the solder processing performance, the weight ratio of iron and copper tin (total amount of copper and tin) in the solder of the present application is 0.0001-0.03:1, the weight ratio of nickel and copper tin is 0.005-0.02:1, the weight ratio of phosphorus and copper tin is 0.1-0.2:1, and the weight ratio of zinc and copper tin is 0.1-0.2:1. By limiting the proportion of the four components to copper tin, the solder processing effect such as wire drawing can be further improved.

[0061] As a preferred embodiment, the nickel is selected from one or more of the elemental state of nickel, copper-nickel binary alloy, chromium-nickel binary alloy, nickel-phosphorus binary alloy, chromium-nickel-phosphorus ternary alloy; preferably, the nickel is metallic nickel, BNi7 alloy and / or BNi7; the iron is selected from one or more of the elemental state of iron, copper-iron binary alloy, ternary alloy; the chromium is selected from the elemental state of chromium, copper-chromium binary alloy, chromium-nickel-phosphorus ternary alloy; the zinc is selected from the elemental state of zinc and / or copper-zinc binary alloy; the titanium is selected from copper-titanium binary alloy; the manganese is selected from the elemental state of manganese and / or copper-manganese binary alloy; the phosphorus is selected from one or more of copper-phosphorus binary alloy, BNi7 alloy and / or BNi6 alloy.

[0062] According to another aspect of the present application, a preparation method of the above-mentioned nickel-containing copper-based solder for stainless steel brazing is provided, comprising:

[0063] S1: ingredients are prepared according to the proportion of each component in the nickel-containing copper-based solder for stainless steel brazing to obtain a mixture;

[0064] S2: the mixture is sequentially subjected to melting and casting to obtain an ingot;

[0065] S3: the ingot is sequentially subjected to homogenization annealing and hot extrusion treatment to obtain a rod.

[0066] S4, the wire rod is subjected to first drawing treatment and first annealing treatment to obtain first annealed material;

[0067] S5, the first annealed material is subjected to second drawing treatment to obtain the welding wire, i.e. the nickel-containing copper-based filler material for stainless steel brazing.

[0068] In step S2, after the smelting treatment, the slag is removed, and then the casting is performed.

[0069] After step S5, there is further step S6: the welding wire is made into a ring-shaped piece, and the ring-shaped piece is subjected to second annealing treatment to obtain the nickel-containing copper-based filler material for stainless steel brazing.

[0070] In step S1, the temperature of smelting is 1120-1200℃, and the time of smelting is 2-3h.

[0071] In step S3, the process of homogenizing annealing includes: the ingot is kept at 600-700℃ for 3-5h.

[0072] In step S4, the conditions of first annealing treatment include: the temperature is 600-700℃, and the time is 3-5h.

[0073] In step S4, the first drawing treatment and the first annealing treatment are sequentially cycled for 3-7 times.

[0074] In step S6, the conditions of second annealing treatment include: the temperature is 150-200℃, and the time is 0.5-1h.

[0075] The number of times in step S4 of the present application is related to the final required wire diameter, for example, after extrusion of the ingot, a 2.5mm wire diameter is obtained, and the cold working rate is controlled at 20-55%, the first drawing obtains 1.5mm, and the cold working rate is 40% (at this time, the required 1.5mm or more wire diameter can be subjected to second annealing treatment); the second drawing obtains 1.2mm, and the deformation rate is subjected to first annealing treatment, and the second drawing treatment continues until the required wire diameter is obtained.

[0076] The present application will be further described in detail below in combination with specific embodiments, and these embodiments cannot be understood as limiting the scope of the present application.

[0077] Example 1

[0078] The preparation method of the nickel-containing copper-based filler material for stainless steel brazing includes the following steps:

[0079] S1: ingredients are prepared according to the following proportions to obtain a mixture;

[0080] By weight percentage, including: tin 7%, nickel 1%, phosphorus 0.1, X 0.14%, (weight percentage of iron element, chromium element, zinc element, titanium element, manganese element in the solder is 0.01%, 0.03%, 0.10% in turn, wherein / represents no element), the balance is copper, total 100%;

[0081] S2, the mixed material is subjected to smelting treatment, the smelting temperature is 1120℃, and the smelting time is 3h; then, slagging and standing are carried out, and then casting is carried out, to obtain an ingot;

[0082] S3, the ingot is subjected to heat preservation at 600-700℃ for 5h (homogenization annealing), and is sent into an extruder to be subjected to hot extrusion treatment, to obtain a wire rod with a diameter of 6mm;

[0083] S4, the wire rod is subjected to drawing treatment and first annealing treatment for 7 times, to obtain an annealed material; the drawing is carried out in a drawing machine, and the annealing is carried out in a pit-type annealing furnace, the annealing temperature is 700℃, and the time is 3h;

[0084] S5, the annealed material is subjected to drawing treatment, to obtain a welding wire; then, the welding wire is made into a ring, to obtain a ring-shaped piece, and the making is carried out on a ring-making machine;

[0085] S6, the ring-shaped piece is subjected to second annealing treatment, the annealing treatment temperature is 150℃, and the time is 0.5h, to obtain a nickel-containing copper-based solder for stainless steel brazing.

[0086] The copper-based solder for stainless steel brazing is used for brazing of stainless steel and copper, to obtain a brazed piece of stainless steel and copper, stainless steel and stainless steel material.

[0087] The SEM morphology of the brazed piece prepared from the stainless steel brazing copper-based solder of the above-mentioned embodiment 1 is shown in FIG. 1 (light gray area is solder, dark gray is base), wherein the acceleration voltage is 15.00kV, the probe type is CBS, the beam current is 0.55nA, the beam spot is 4.5, the working distance is 10.2mm, the magnification is 1000x, and the field width is 127μm; the composition (wt%) of region 1, region 2, region 3, region 4, region 5, region 6, region 7, region 8 in FIG. 1 is shown in Table 1. The following points can be seen from the SEM morphology:

[0088] (1) The stainless steel interface, region 1, region 2, the Ni content decreases by about 0.15% relative to the base region 4, region 5. The Cr content decreases by about 0.9%, the Mn content is relatively high, and the surface is enriched with 0.2-0.4% P and 1.0-1.3% Cu;

[0089] (2) The stainless steel interface, sporadic and independent distribution of phosphide particles can be observed, region 3;

[0090] (3) In the solder, the Sn-rich Cu-based solid solution dissolves about 1.8-1.9% of Fe and 0.3% of Cr, and no P element is detected, indicating that P has a stronger tendency to preferentially react with the stainless steel matrix.

[0091] Since no austenite-to-ferrite transformation occurs at the stainless steel interface, no local pitting leakage defects occur in the stainless steel matrix. The neutral salt spray test shows that the corrosion resistance can be achieved for 2000h without leakage, far exceeding the 1000h standard.

[0092] Table 1

[0093] The tensile strength of the brazed piece of Example 1 is 331 MPa, and the shear strength is 175 MPa, and the mechanical properties are not deteriorated, meeting the product use requirements.

[0094] Example 2

[0095] The preparation method of the nickel-containing copper-based solder for brazing stainless steel comprises the following steps:

[0096] S1: according to the following proportioning, a mixture is obtained;

[0097] In terms of weight percentage, it includes: tin 10%, nickel 1.5%, phosphorus 0.15%, X 0.454% (the weight percentages of iron, chromium, zinc, titanium and manganese in the solder are 0.05%, 0.1%, 0.3%, 0.004% respectively), and the balance is copper, totaling 100%;

[0098] S2, the mixture is subjected to smelting treatment, the smelting temperature is 1200℃, and the smelting time is 2h; then the slag is removed, and the cast ingot is obtained by casting after standing;

[0099] S3, the cast ingot is kept at 700℃ for 3h, and then sent to an extruder for hot extrusion treatment to obtain a wire rod with a diameter of 6mm;

[0100] S4, the wire rod is subjected to drawing treatment and first annealing treatment for 5 times to obtain an annealed material; the drawing is carried out in a drawing machine, and the annealing is carried out in a pit-type annealing furnace, the annealing temperature is 700℃, and the time is 4h;

[0101] S5, the annealed material is subjected to drawing treatment to obtain a welding wire; then the welding wire is made into a ring to obtain a ring-shaped piece, and the ring making is carried out on a ring making machine;

[0102] S6, the ring-shaped piece is subjected to second annealing treatment, the annealing treatment temperature is 200℃, and the time is 1h, to obtain a nickel-containing copper-based solder for brazing stainless steel.

[0103] The above-mentioned copper-based solder for brazing stainless steel is used for brazing stainless steel and copper to obtain a brazed piece of stainless steel and copper, and a brazed piece of stainless steel and stainless steel material.

[0104] The SEM morphology of the brazing joint stainless steel interface of the brazing piece prepared by Example 2 after the ferric chloride corrosion test is shown in Figure 2, wherein the acceleration voltage is 15.00 kV, the detector type is CBS, the beam current is 0.91 nA, the beam spot is 5.0, the working distance is 9.9 mm, the magnification is 2000x, and the field width is 63.5 μm; the composition (wt%) of region 1, region 2, region 3, region 4, region 5, region 6, region 7, and region 8 in Figure 2 is shown in Table 2. The following points can be seen from the SEM morphology graph:

[0105] (1) The stainless steel interface, region 1, region 2, and region 3, relative to the base region 4 and region 5, do not have a significant decrease in Ni and Cr content with the increase of Ni and Cr content in the solder. Due to the decrease of the main element Sn content, the welding temperature rises, the Mn content diffuses obviously into the solder, and the surface is enriched with 0.4-0.5% P and 1.6-2.3% Cu;

[0106] (2) No phosphide particles are observed at the stainless steel interface, but there are local regions surrounded by CuSn second phase, region 8. Due to the stronger solid solution capacity of the solder to Fe and Ni, a local Fe-Cr-based second phase region 9 is generated;

[0107] (3) Since no austenite to ferrite transformation occurs at the stainless steel interface, no local pitting leakage defects occur in the stainless steel base. The neutral salt spray test shows that the corrosion resistance can be achieved for 2000 h without leakage, far exceeding the 1000 h standard.

[0108] Table 2

[0109] The tensile strength of the brazing piece of Example 2 is 300 MPa, and the shear strength is 165 MPa, which meets the use requirements.

[0110] Example 3

[0111] The preparation method of the nickel-containing copper-based solder for brazing stainless steel includes the following steps:

[0112] S1: according to the following proportioning, a mixture is obtained;

[0113] In terms of weight percentage, it includes: tin 13%, nickel 2.0%, phosphorus 0.22%, X 0.4% (the weight percentages of iron, chromium, zinc, titanium, and manganese in the solder are 0.10%, 0.05%, 0.1%, 0.15%, respectively), and the balance is copper, totaling 100%;

[0114] S2, the mixture is subjected to smelting treatment, the smelting temperature is 1150℃, the smelting time is 2.5h; then slagging, standing, and then casting, to obtain an ingot;

[0115] S3, the ingot is kept at 750℃ for 4h, and then is sent into an extruder for hot extrusion treatment, to obtain a wire rod with a diameter of 6mm;

[0116] S4, the wire rod is subjected to drawing treatment and first annealing treatment for 6 times, to obtain an annealed material; the drawing is carried out in a drawing machine, and the annealing is carried out in a pit-type annealing furnace, the annealing temperature is 750℃, and the time is 4h;

[0117] S5, the annealed material is subjected to drawing treatment, to obtain a welding wire; then the welding wire is made into a ring, to obtain a ring-shaped piece, the making is carried out on a ring-making machine;

[0118] S6, the ring-shaped piece is subjected to second annealing treatment, the annealing treatment temperature is 200℃, and the time is 1h, to obtain a copper-based filler material containing nickel for stainless steel brazing.

[0119] The copper-based filler material containing nickel for stainless steel brazing is used for brazing of stainless steel and copper, to obtain a brazed piece of stainless steel and copper, stainless steel and stainless steel material.

[0120] The SEM morphology of the brazed piece prepared from Example 3 after ferric chloride corrosion test at the stainless steel interface is shown in FIG. 3, wherein the acceleration voltage is 15.00kV, the detector type is CBS, the beam current is 0.91nA, the beam spot is 5.0, the working distance is 9.6mm, the magnification is 2000x, and the field width is 63.5μm; the components (wt%) of region 1, region 2, region 3, region 4, region 5, region 6, region 7, and region 8 in FIG. 3 are shown in Table 3. The following points can be seen from the SEM morphology graph:

[0121] (1) At the stainless steel interface, the content of Ni in region 1, region 2, and region 3 decreases slightly by about 0.02% relative to the base region 4 and region 5, which can be considered as no obvious change. The content of Cr decreases by about 0.7%, and the content of Mn diffuses obviously into the filler material, with 0.4-0.5% P and 2.9%-4.3% Cu enriched on the surface.

[0122] (2) With the increase of P content in the filler material, more phosphides are formed on the surface of the stainless steel base;

[0123] (3) Since no austenite to ferrite transformation occurs at the stainless steel interface, no local pitting leakage defects of the stainless steel base occur, and the neutral salt spray test shows that the corrosion resistance can be realized for 1000h without leakage, reaching the 1000h standard.

[0124] Table 3

[0125] The tensile strength of the brazing piece of Example 3 is 295 MPa, and the shear strength is 155 MPa, which meets the use requirements.

[0126] Example 4

[0127] The difference between Example 4 and Example 3 is that the copper-based filler metal for brazing stainless steel comprises, by weight percentage: tin 12%, nickel 2.5%, phosphorus 0.3%, X 0.3705% (the weight percentages of iron, chromium, zinc, titanium, and manganese in the filler metal are 0.15%, 0.17%, 0.0005%, and 0.05%, respectively), and the balance is copper, totaling 100%.

[0128] The SEM morphology of the brazing piece in Example 4 after the ferric chloride hydrochloric acid corrosion resistance test is similar to that of Figure 3; the component distribution in the similar area is similar to that in Table 3; the tensile strength of the brazing piece of Example 4 is 300 MPa, and the shear strength is 158 MPa.

[0129] Example 5

[0130] The difference between this Example 5 and Example 3 is that the copper-based filler metal for brazing stainless steel comprises, by weight percentage: tin 12%, nickel 2.5%, phosphorus 0.4%, X 0.3705% (the weight percentages of iron, chromium, zinc, titanium, and manganese in the filler metal are 0.15%, 0.17%, 0.0005%, and 0.05%, respectively), and the balance is copper, totaling 100%.

[0131] The SEM morphology of the brazing piece in Example 5 after the ferric chloride hydrochloric acid corrosion resistance test is similar to that of Figure 3; the component distribution in the similar area is similar to that in Table 3; the tensile strength of the brazing piece of Example 5 is 286 MPa, and the shear strength is 158 MPa.

[0132] Example 6

[0133] The difference between this Example 6 and Example 3 is that the copper-based filler metal for brazing stainless steel comprises, by weight percentage: tin 12%, nickel 2%, phosphorus 0.2%, X 0.4505% (the weight percentages of iron, chromium, zinc, titanium, and manganese in the filler metal are 0.25%, 0.0005%, and 0.2%, respectively), and the balance is copper, totaling 100%.

[0134] The SEM morphology of the brazing piece in Example 6 after the ferric chloride hydrochloric acid corrosion resistance test is similar to that of Figure 3; the component distribution in the similar area is similar to that in Table 3; the tensile strength of the brazing piece of Example 6 is 310 MPa, and the shear strength is 162 MPa.

[0135] Example 7

[0136] The difference between this embodiment 7 and embodiment 3 is that the copper-based solder for brazing stainless steel comprises, by weight percentage: tin 12%, nickel 2%, phosphorus 0.2%, X 0.4501% (the weight percentages of iron, chromium, zinc, titanium, and manganese in the solder are 0.1%, 0.05%, 0.2%, 0.0001%, and 0.1%, respectively), and the balance being copper, with the total being 100%.

[0137] The SEM morphology of the brazed piece after the corrosion test in ferric chloride hydrochloric acid in embodiment 7 is similar to that in Figure 3, and the component distribution in similar regions is similar to that in Table 3; the tensile strength of the brazed piece in embodiment 7 is 298 MPa, and the shear strength is 157 MPa.

[0138] Embodiment 8

[0139] The difference between this embodiment 8 and embodiment 3 is that the copper-based solder for brazing stainless steel comprises, by weight percentage: tin 12%, nickel 3.0%, phosphorus 0.3%, X 0.45% (the weight percentages of iron, chromium, zinc, titanium, and manganese in the solder are 0.1%, 0.15%, 0.1, and 0.1%, respectively), and the balance being copper, with the total being 100%.

[0140] The SEM morphology of the brazed piece after the corrosion test in ferric chloride hydrochloric acid in embodiment 8 is similar to that in Figure 3; the component distribution in similar regions is similar to that in Table 3; the tensile strength of the brazed piece in embodiment 8 is 220 MPa, and the shear strength is 124 MPa.

[0141] Embodiment 9

[0142] The difference between this embodiment 9 and embodiment 3 is that the copper-based solder for brazing stainless steel comprises, by weight percentage: tin 12%, nickel 2%, phosphorus 0.1%, X 0.45% (the weight percentages of iron, chromium, zinc, titanium, and manganese in the solder are 0.1%, 0.25%, 0, 0, and 0.1%, respectively), and the balance being copper, with the total being 100%.

[0143] The SEM morphology of the brazed piece after the corrosion test in ferric chloride hydrochloric acid in embodiment 9 is similar to that in Figure 3; the component distribution in similar regions is similar to that in Table 3; the tensile strength of the brazed piece in embodiment 9 is 201 MPa, and the shear strength is 120 MPa.

[0144] Comparative Example 1 (conventional solder)

[0145] The difference between comparative example 1 and embodiment 3 is that the copper-based solder BCuSn12P for brazing stainless steel has a formula comprising: the solder has a Sn content of 11-13% and a P content of 0.2-0.4%, and the balance is copper.

[0146] The same test method was used to test the stainless steel interface SEM and corrosion resistance of the welding piece of Comparative Example 1, and the results are shown in Figures 4, 5, 6, 7, and 8.

[0147] In Figure 4, the acceleration voltage was 15.00 kV, the probe type was CBS, the beam current was 0.28 nA, the beam spot was 4.0, the working distance was 9.9 mm, the magnification was 1000x, and the field width was 127 μm.

[0148] In Figure 5, the acceleration voltage was 15.00 kV, the probe type was CBS, the beam current was 0.28 nA, the beam spot was 4.0, the working distance was 9.9 mm, the magnification was 4000x, and the field width was 31.8 μm.

[0149] In Figure 6, the acceleration voltage was 15.00 kV, the probe type was CBS, the beam current was 0.55 nA, the beam spot was 4.5, the working distance was 9.9 mm, the magnification was 4000x, and the field width was 31.8 μm.

[0150] In Figure 7, the acceleration voltage was 15.00 kV, the probe type was ETD, the working distance was 10.0 mm, the magnification was 1000x, and the field width was 127 μm.

[0151] In Figure 8, the acceleration voltage was 15.00 kV, the probe type was ETD, the working distance was 10.1 mm, the magnification was 1000x, and the field width was 127 μm.

[0152] Figure 4 is a metallographic phase of the stainless steel interface after welding, Figure 5 is a partial enlarged view of Figure 4, used to analyze the composition of different regions, and Table 4 is obtained, from which it can be seen that the interface Cr, Ni, and Mn decrease significantly.

[0153] Figure 6 is the composition of the solder itself after welding, from which it can be seen that Cr increases slightly by 0.1%, Mn increases slightly by 0.1-0.2%, Fe and Ni differ in different phases of the solder, but increase significantly by about 1%. According to the original composition, it can be considered that the four elements of Cr, Mn, Fe, and Ni all come from the stainless steel matrix. In addition, it can be seen that the P content is 0, and it can be considered that P diffuses to the surface of the stainless steel.

[0154] Figures 7 and 8 are the solder after salt spray corrosion, from which it can be seen that there is a clear corrosion path at the interface, which extends along the ferrite zone of the stainless steel surface. Figure 7 shows less corrosion, and Figure 8 shows more corrosion.

[0155] P in the solder diffuses to the surface of the stainless steel, a P diffusion layer of 5-10 μm is formed at the interface of the stainless steel, the P content in the diffusion layer is about 1.0%; Cu in the solder diffuses to the surface of the stainless steel, a Cu diffusion layer of 5-10 μm is formed at the interface of the stainless steel, the Cu content in the diffusion layer is about 1-7%; Fe, Cr, Ni and Mn in the interface of the stainless steel diffuse to the solder, the solder dissolves about 1-3% Fe, 1-3% Ni, 0.5-1% Cr and 1.5% Mn, so that the interface of the stainless steel becomes Fe-18Cr-8Ni-1.5Mn, the contents of Cr, Ni and Mn decrease, the contents of Cu and P increase, and the interface composition is changed into, for example, Fe-16Cr-2Ni-4Cu-0.1P; the excess P combines with the diffused Cr and Fe to form phosphide at the interface. This phenomenon will result in the following defects: the interface composition of the stainless steel is changed, Ni and Mn are both austenite forming elements, and the brazing diffusion causes the contents of Ni and Mn to decrease, so that the austenite at the surface of the base body of 5-10 μm is changed into ferrite rich in Cu and P. Because the interface is ferrite rich in Cu and P, and the interface composition of the stainless steel is changed, galvanic corrosion is formed, the ferrite is more easily corroded, and the solder joint is leaked.

[0156] Figures 5 and 6 show the interface of the stainless steel and the solder after the soldering of the solder, regions 1 and 2 are at the interface of the stainless steel of 3 μm, and the contents of P, Cr, Ni and Cu are 0.9-1.0, 14.2-14.5, 1.4-1.7 and 2.6-2.7 respectively, as shown in Tables 4 and 5; regions 3 and 4 have different contrasts in the secondary electron imaging.

[0157] Table 4

[0158] Table 5

[0159] Figures 7 and 8 show the typical interface corrosion morphology of the solder of the comparative example 1, which are the front end and the middle section of the corrosion respectively, and it can be seen that the corrosion occurs at the interface of 5-10 μm.

[0160] Comparative example 2 (X contains only chromium element)

[0161] The difference between the comparative example 2 and the example 3 is that the copper-based solder formula for brazing the stainless steel comprises: chromium 0.28%, nickel 1.52%, phosphorus 0.2%, tin 11.76% and the balance of copper; the SEM morphology at the interface of the stainless steel is shown in Figure 9, wherein EHT=15.00 kV, WD=9.4 mm, Signal A=AsB, Mag=500x, and the compositions (wt%) of points ABCDE in Figure 9 are shown in Table 6; and the tensile strength thereof is 200 MPa, and the shear strength thereof is 115 MPa.

[0162] Table 6

[0163] The Cr content is also adjusted in the embodiments. In actual processing, it is found that the wire drawing performance decreases when Cr > 0.1, the solder matrix is more cracked when the Cr content is higher, the solder wire becomes brittle when the Cr content is 0.28%, and the wire drawing is finer when the Cr content is lower.

[0164] Comparative Example 3 (X overage)

[0165] Comparative Example 3 differs from Example 3 in that the copper-based solder formulation for brazing stainless steel includes: tin 13%, nickel 2.0%, phosphorus 0.2%, X 0.8001% (the weight percentages of iron, chromium, zinc, titanium, and manganese in the solder are 0.25%, 0.40%, 0.1%, 0.0001%, and 0.05%, respectively), and the balance is copper, totaling 100%.

[0166] When the total addition amount of iron, chromium, zinc, titanium, and manganese is too large, too much X element forms too many hard phases, cracks the matrix, increases the cracking probability during solder casting and hot extrusion, and makes it more difficult to draw into wire.

[0167] Comparative Example 4 (phosphorus overage)

[0168] Comparative Example 4 differs from Example 3 in that the copper-based solder formulation for brazing stainless steel includes: tin 13%, nickel 2.0%, phosphorus 0.5%, X 0.3% (the weight percentages of iron, chromium, zinc, titanium, and manganese in the solder are 0.1%, 0.05%, 0.1%, 0.05%, respectively), and the balance is copper, totaling 100%.

[0169] After testing the corrosion resistance and mechanical properties of the welded parts, too much phosphorus currently forms phosphides at the interface. Currently, only the low potential of phosphides is found, and too much phosphides have not been found to have a significant impact on neutral salt spray, but more impact on joint strength and more brittle phases during wire drawing processing, making it difficult to draw wire.

[0170] The test methods used in the above examples and comparative examples are as follows:

[0171] 1. Neutral salt spray corrosion test: use a saltwater concentration of 5%, pH = 6.5-7.2, constant temperature 35±2℃, place the sample on the sample holder 25cm to the left of the nozzle, seal the salt spray chamber and continuously spray for a period of time, then take out, use 4.3MPa gas pressure to detect its airtightness;

[0172] 2. Mechanical property test: test according to GB / T11363-2008 "Brazed joint strength test method".

[0173] The application controls the content of Sn element in the solder at 7-13%, the content of Ni at 0.5-3.5%, and the content of P at ≤0.4%, the content of X at 0.0001%-0.5%, and controls the content of specific elements by adding specific elements, and the salt spray corrosion resistance of the nickel-containing copper-based solder for stainless steel brazing is significantly improved by the synergistic effect in many aspects, and the application of stainless steel pipelines / valves under severe conditions such as coastal areas is ensured.

[0174] The above only describes the preferred embodiments of the application and is not intended to limit the application. Those skilled in the art can make various modifications and changes to the application. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A nickel-containing copper-based solder for brazing stainless steel, characterized in that, By weight percentage, the nickel-containing copper-based solder for stainless steel brazing comprises the following components: Tin 7%–13%, nickel 0.5%–3.5%, phosphorus 0.02%–0.4%, X 0.0001%–0.5%, balance copper, totaling 100%; wherein X is selected from one or more of iron, chromium, zinc, titanium and manganese.

2. The nickel-containing copper-based solder for brazing stainless steel according to claim 1, characterized in that, The nickel-copper-based solder for brazing stainless steel comprises the following elements: 11%–13% tin, 1.5%–2% nickel, 0.05%–0.2% phosphorus, 0.001%–0.5% x, with the balance being copper, totaling 100%. Preferably, the composition is 11%–13% tin, 1.5%–2% nickel, 0.05%–0.1% phosphorus, 0.001%–0.5% x, with the balance being copper, totaling 100%.

3. The nickel-containing copper-based solder for brazing stainless steel according to claim 1 or 2, characterized in that, X includes iron, chromium, zinc, titanium, and manganese; Preferably, the iron content in the solder is 0.0001–0.5% by weight, the chromium content in the solder is 0.0001–0.5% by weight, the zinc content in the solder is 0.0001–0.5% by weight, the titanium content in the solder is 0.0001–0.5% by weight, and the manganese content in the solder is 0.0001–0.5% by weight.

4. The nickel-containing copper-based solder for brazing stainless steel according to claim 3, characterized in that, The iron content in the solder is 0.01% to 0.2% by weight; the chromium content in the solder is 0.0001% to 0.3% by weight; the zinc content in the solder is 0.0001% to 0.5% by weight; the titanium content in the solder is 0.0001% to 0.005% by weight; and the manganese content in the solder is 0.0001% to 0.3% by weight.

5. The nickel-containing copper-based solder for brazing stainless steel according to any one of claims 1 to 4, characterized in that, The nickel is selected from one or more of elemental nickel, copper-nickel binary alloys, chromium-nickel binary alloys, nickel-phosphorus binary alloys, and chromium-nickel-phosphorus ternary alloys; preferably, the nickel is selected from BNi7 alloy and / or BNi6 alloy. And / or, the phosphorus is selected from one or more of copper-phosphorus binary alloys, BNi7 alloys, and BNi6 alloys; And / or, the iron is selected from one or more of elemental iron, copper-iron binary alloys, and ternary alloys; And / or, the chromium is selected from copper-chromium binary alloys and / or chromium-nickel-phosphorus ternary alloys; And / or, the zinc is selected from elemental zinc and / or copper-zinc binary alloys; And / or, the titanium is selected from copper-titanium binary alloys; And / or, the manganese is selected from elemental manganese and / or copper-manganese binary alloys.

6. The method for preparing the nickel-containing copper-based solder for stainless steel brazing according to any one of claims 1 to 5, characterized in that, The preparation method includes the following steps: S1: Prepare the mixture according to the proportion of each component in the nickel-copper-based solder for stainless steel brazing; S2, the mixture is melted and cast sequentially to obtain an ingot; S3, the ingot is subjected to homogenization annealing and hot extrusion treatment in sequence to obtain wire rod; S4, the wire rod is subjected to a first drawing process and a first annealing process to obtain a first annealed material; S5, the first annealed material is subjected to a second drawing process to obtain a wire-shaped nickel-copper based solder for brazing stainless steel.

7. The method for preparing nickel-containing copper-based solder for stainless steel brazing according to claim 6, characterized in that, In step S2, after smelting, the material is removed from slag, allowed to stand, and then cast. And / or, step S5 further includes: forming a ring from the filamentous stainless steel brazing nickel-copper-based solder to obtain an annular component, and subjecting the annular component to a second annealing treatment to obtain the stainless steel brazing nickel-copper-based solder.

8. The method for preparing nickel-containing copper-based solder for stainless steel brazing according to claim 6, characterized in that, In step S1, the melting temperature is 1120℃~1200℃, and the melting time is 2~3h; And / or, in step S3, the homogenization annealing process includes: holding the ingot at 600℃~700℃ for 3~5 hours.

9. The method for preparing nickel-containing copper-based solder for stainless steel brazing according to claim 7, characterized in that, In step S4, the conditions for the first annealing treatment include: a temperature of 600℃~700℃ and a time of 3~5h; And / or, in step S4, the first drawing process and the first annealing process are performed sequentially 3 to 7 times. And / or, in step S5, the conditions for the second annealing treatment include: a temperature of 150–200°C and a time of 0.5–1 h.

10. The application of the nickel-containing copper-based solder for brazing stainless steel according to any one of claims 1 to 5, or the nickel-containing copper-based solder for brazing stainless steel obtained by the preparation method according to any one of claims 6 to 9, in the brazing of stainless steel products.

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