Brazing sheet manufacturing method

Abstract

To provide a method for manufacturing a brazing sheet in which a nickel-chromium phosphorus compound layer with corrosion resistance is formed on a surface of a stainless thin plate.SOLUTION: A brazing sheet is manufactured by the following steps of: adding chromium powders to a plating solution containing nickel sulfate, nickel chloride, boric acid, and phosphoric acid; immersing a stainless thin plate into the plating solution in the presence of sodium lauryl sulfate and sodium citrate; and forming a thin layer of a nickel-chromium phosphorus compound composite plating layer on a surface of the stainless thin plate as a nickel-chromium phosphorus compound thin layer by an electrolytic plating method.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a brazing sheet, and more particularly to a method for manufacturing a brazing sheet having a thin layer of nickel-chromium-phosphorus compound on the surface of a thin stainless steel sheet. [Background technology]

[0002] A conventional method for manufacturing this type of brazing sheet has been proposed, in which a stainless steel sheet is immersed in a plating solution containing nickel sulfate, nickel chloride, boric acid, and phosphoric acid in the presence of sodium citrate, and a thin nickel-phosphorus compound composite plating layer is formed on the surface of the stainless steel sheet by electroplating (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-050928 Summary of the Invention [Problem to be solved by the invention]

[0004] Heat exchangers used in solid oxide fuel cells and heat exchangers used to recover waste heat from exhaust gases are preferably made of stainless steel from the perspective of corrosion resistance. Nickel alloy brazing filler metals are typically used for stainless steel, but nickel alloys have high hardness and low ductility and are supplied as rods on the order of several millimeters or as powder pastes on the order of tens to hundreds of micrometers. This makes it difficult to use them to coat the surface of thin stainless steel sheets with a thin film of nickel alloy brazing filler metal to form a stainless steel brazing sheet. The above-mentioned technology forms a brazing sheet with a nickel-phosphorus compound layer 30 μm or less thick on the surface of thin stainless steel sheets, but the brazing filler metal must also be corrosion-resistant.

[0005] The main object of the present invention is to propose a method for manufacturing a brazing sheet in which a corrosion-resistant nickel-chromium-phosphorus compound layer is formed on the surface of a thin stainless steel sheet. [Means for solving the problem]

[0006] The method for producing a brazing sheet of the present invention employs the following means to achieve the above-mentioned main object.

[0007] The first method for producing a brazing sheet of the present invention includes: A method for manufacturing a brazing sheet having a thin layer of nickel-chromium-phosphorus compound on the surface of a stainless steel thin plate, comprising: Nickel sulfate, nickel chloride, and boric acid Phosphorous acid and immersing the stainless steel sheet in the presence of sodium lauryl sulfate and sodium citrate while adding chromium powder to a plating solution containing the above, and forming a thin layer of a nickel-chromium-phosphorus compound composite plating layer on the surface of the stainless steel sheet by an electrolytic plating method as the nickel-chromium-phosphorus compound thin layer, thereby producing the brazing sheet. It is characterized by:

[0008] In the first method for producing a brazing sheet of the present invention, nickel sulfate (NiSO4), nickel chloride (NiCl2), and boric acid (H3BO3) are mixed. Phosphorous acid Chromium powder was added to a plating solution containing sodium lauryl sulfate (NaCl) and 12 H 25A thin layer of nickel-chromium-phosphorus compound composite plating is formed on the surface of a stainless steel sheet by immersing the sheet in the presence of sodium citrate (Na3C6H5O7) and sodium sulfate (SO4). A thin nickel-chromium-phosphorus compound composite plating layer is then formed on the surface of the stainless steel sheet using electroplating. Chromium powder is added and electroplating is performed in the presence of sodium lauryl sulfate and sodium citrate. The thickness of the nickel-chromium-phosphorus compound layer can be adjusted by adjusting the electroplating parameters, such as current density and plating time. This allows the production of a brazing sheet with a corrosion-resistant nickel-chromium-phosphorus compound layer formed on the surface of the stainless steel sheet.

[0009] In the first method for producing a brazing sheet of the present invention, the plating solution contains 1.0 mol / L of nickel sulfate hexahydrate, 0.2 mol / L of nickel chloride hexahydrate, 0.5 mol / L of boric acid, Phosphorous acid The plating solution may be prepared so that the concentration of chromium is in the range of 0.4 mol / L to 0.8 mol / L, and chromium powder having a purity of 99.9% and an average particle size of 10 μm is added in the range of 0.1 to 30 g / L, and the plating solution may contain sodium lauryl sulfate at about 0.1 g / L and sodium citrate at about 0.5 mol / L.

[0010] The second method for producing a brazing sheet of the present invention is as follows: A method for manufacturing a brazing sheet having a thin layer of nickel-chromium-phosphorus compound on the surface of a stainless steel thin plate, comprising: The brazing sheet is manufactured by immersing the stainless steel sheet in a plating solution containing nickel chloride as a nickel source, sodium hypophosphite as a phosphorus source, and chromium chloride as a chromium source, and also containing a chromium complexing agent, a nickel complexing agent, a pH buffer, a conductive salt, and a surfactant, and forming a thin nickel-chromium-phosphorus compound plating layer on the surface of the stainless steel sheet by electrolytic plating. It is characterized by:

[0011] In a second brazing sheet manufacturing method of the present invention, a stainless steel sheet is immersed in a plating solution containing nickel chloride (NiCl) as a nickel source, sodium hypophosphite (NaHPO·H O) as a phosphorus source, and chromium chloride (CrCl / 6H O) as a chromium source, as well as a chromium complexing agent, a nickel complexing agent, a pH buffer, a conductive salt, and a surfactant. A thin nickel-chromium-phosphorus compound composite plating layer is then formed on the surface of the stainless steel sheet by electroplating. The thickness of the nickel-chromium-phosphorus compound layer can be adjusted by adjusting the electroplating parameters, such as current density and plating time. This allows the production of a brazing sheet having a corrosion-resistant nickel-chromium-phosphorus compound layer formed on the surface of the stainless steel sheet.

[0012] In the second method for producing a brazing sheet of the present invention, glycine (C2H5NO2) is used as a complexing agent for chromium, sodium citrate (Na3C6H5O7) is used as a complexing agent for nickel, boric acid (H3PO4) is used as a pH buffering agent, ammonium chloride (NH4Cl) and / or sodium chloride (NaCl) are used as conductive salts, and saccharin sodium (C7H4NO3SNa·2H2O) and / or sodium lauryl sulfate (NaC 12 H 25In this case, the plating solution may be prepared as follows: nickel chloride hexahydrate (NiCl2·6H2O) 0.25 mol / L, sodium hypophosphite monohydrate (NaH2PO2·H2O) 0.14 mol / L, chromium chloride hexahydrate (CrCl3·6H2O) 0.4 mol / L, glycine 0.5 mol / L, sodium citrate 0.2 mol / L, boric acid 0.5 mol / L, ammonium chloride 0.5 mol / L, sodium chloride 0.5 mol / L, saccharin sodium dihydrate (C7H4NO3SNa·2H2O) 0.6 g / L, and sodium lauryl sulfate 0.1 g / L. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a configuration diagram showing an example of an experimental plating apparatus 20. [Figure 2] This is a graph showing the experimental results of the components of nickel-chromium-phosphorus compound composite plating when the amount of chromium powder added is changed as a parameter when the phosphoric acid is 0.4 mol / L. [Figure 3] This is a graph showing the experimental results of the components of nickel-chromium-phosphorus compound composite plating when the amount of chromium powder added is changed as a parameter when the phosphoric acid is 0.8 mol / L. [Figure 4] 10 is a graph showing the results of galvanic current measurements. [Figure 5] 10 is a table showing plating conditions and plating film components as experimental results in the manufacturing method of the brazing sheet according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Next, embodiments of the present invention will be described. In a method for manufacturing a brazing sheet according to a first embodiment, chromium powder is added to a plating solution containing nickel sulfate (NiSO), nickel chloride (NiCl), boric acid (HBO), and phosphoric acid (HPO), and sodium lauryl sulfate (NaCl) is added to the plating solution. 12 H25 A thin layer of nickel-chromium-phosphorus compound composite plating is formed on the surface of a stainless steel sheet by electroplating, immersing the sheet in the presence of nickel sulfate hexahydrate (NiSO4·6H2O) and sodium citrate (Na3C6H5O7). The plating solution is prepared with 1.0 mol / L of nickel sulfate hexahydrate (NiSO4·6H2O), 0.2 mol / L of nickel chloride hexahydrate (NiCl2·6H2O), 0.5 mol / L of boric acid (H3BO3), and a range of 0.4 mol / L to 0.8 mol / L of phosphoric acid (H3PO3). The phosphoric acid concentration is set to 0.4 mol / L to 0.8 mol / L because, when the brazing temperature of the brazing sheet is approximately 1000°C, Ni-8 to 13P (by weight) is an effective component of the nickel-phosphorus compound thin layer, given the state of the nickel-phosphorus binary alloy. The chromium powder to be added to the plating solution is 99.9% pure chromium powder with an average particle size of 10 μm, in the range of 0.1 to 30 g / L, and sodium lauryl sulfate (NaC 12 H 25 The preferred concentrations of chromium are about 0.1 g / L for sodium citrate (Na3C6H5O7) and about 0.5 mol / L for sodium citrate (Na3C6H5O7). By adding chromium powder to the plating solution and electroplating in the presence of sodium lauryl sulfate and sodium citrate, a membrane-like nickel-chromium-phosphorus compound composite plating layer can be formed on the surface of thin stainless steel sheet. The thickness of the nickel-chromium-phosphorus compound layer can be adjusted by adjusting the parameters of the electroplating process, such as the current density and plating time.

[0015] An experiment was conducted using an experimental plating apparatus 20 shown in Fig. 1 to produce a brazing sheet according to the first embodiment. The experimental plating apparatus 20 includes a plating tank 22 that stores 500 mL of plating solution 24, a nickel electrode 26 as an anode, a stainless steel electrode 28 as a cathode, a power supply 30 that applies a current (voltage) to the nickel electrode 26 and the stainless steel electrode 28, a temperature sensor 32 that detects the temperature of the plating solution 24, a heater 34 that heats the plating solution 24, a temperature control device 36 that turns the heater 34 on and off based on the temperature from the temperature sensor 32, an air pump 40, and an aeration pipe 38 that aerates the plating solution 24 with air supplied from the air pump 40. The stainless steel electrode 28 is L-shaped and made of SUS304 stainless steel plate, and plating is performed on the vertical portion in the figure. In the experiment, the plating solution 24 was prepared to contain 1.0 mol / L of nickel sulfate hexahydrate, 0.2 mol / L of nickel chloride hexahydrate, 0.5 mol / L of boric acid, 0.4 mol / L and 0.8 mol / L of phosphoric acid, 0.1 g / L of sodium lauryl sulfate, and 0.5 mol / L of sodium citrate. 1 g / L, 2 g / L, and 5 g / L of chromium powder with a purity of 99.9% and an average particle size of 10 μm were added. The plating solution 24 was kept at 50°C and sufficiently aerated, and the current density flowing through the horizontal part of the stainless steel electrode 28 was 3 [A / dm 2 ] was carried out.

[0016] Figure 2 shows the experimental results of the components of nickel-chromium-phosphorus compound composite plating when the amount of chromium powder added is changed as a parameter when the phosphoric acid is 0.4 mol / L, and Figure 3 shows the experimental results of the components of nickel-chromium-phosphorus compound composite plating when the amount of chromium powder added is changed as a parameter when the phosphoric acid is 0.8 mol / L. In Figures 2 and 3, the current density is 3 [A / dm 2The bars in the figure represent, from bottom to top, the weight percentages of nickel (Ni), phosphorus (P), chromium (Cr), and carbon (C), and the numbers to the left of the bars indicate the weight percentage of each component. According to the liquidus surface diagram based on the nickel-chromium-phosphorus ternary phase diagram, considering that the upper limit temperature of the hydrogen furnace used for brazing is 1120°C and the brazing temperature is approximately 1000°C, a phosphorus (P) content of 9-13% is desirable. To prevent the precipitation of brittle trinickel phosphide (Ni3P) during solidification, a phosphorus (P) content of 9-11% is preferable. In Figures 2 and 3, the composition at the left end, with 0.8 mol / L of phosphoric acid and 1 g / L of chromium powder, is considered optimal for nickel-chromium-phosphorus compound composite plating. This alloy contains 11% chromium and 11% phosphorus by weight (hereafter referred to as Ni-11Cr-11P).

[0017] Brazing was performed using Ni-11Cr-11P composite plating films in a continuous furnace under a hydrogen atmosphere (dew point: -50°C) at a brazing temperature of 1020°C for 15 minutes. The Ni-11Cr-11P composite plating films produced good joints, with a shear strength of 58.0 MPa, a better result than the 47.3 MPa shear strength of the Ni-11P brazed joint. Figure 4 shows the galvanic current measurements when stainless steel (SUS304) was used as the anode and the composite plating films (Ni-11P, Ni-11Cr-11P) were used as the cathode. Graph A shows the results when Ni-11Cr-11P was used as the cathode, and graph B shows the results when Ni-11P was used as the cathode. As can be seen, the corrosion current was reduced when Ni-11Cr-11P was used as the cathode compared to when Ni-11P was used as the cathode. This shows that Ni-11Cr-11P as a brazing material has higher corrosion resistance than Ni-11P.

[0018] In the method for manufacturing a brazing sheet according to the first embodiment described above, chromium powder is added to a plating solution containing nickel sulfate, nickel chloride, boric acid, and phosphoric acid, and a stainless steel sheet is immersed in the presence of sodium lauryl sulfate and sodium citrate, and an electrolytic plating method is used to form a thin nickel-chromium-phosphorus compound composite plating layer on the surface of the stainless steel sheet as the nickel-chromium-phosphorus compound thin layer, thereby manufacturing a brazing sheet having a thin, highly corrosion-resistant nickel-chromium-phosphorus compound thin layer formed on the surface of the stainless steel sheet.

[0019] Next, a method for manufacturing a brazing sheet according to a second embodiment will be described. A stainless steel sheet is immersed in a plating solution containing nickel chloride (NiCl2) as a nickel source, sodium hypophosphite (NaH2PO2) as a phosphorus source, and chromium chloride (CrCl3) as a chromium source, and also containing a chromium complexing agent, a nickel complexing agent, a pH buffer, a conductive salt, and a surfactant. A thin layer of nickel-chromium-phosphorus compound plating is formed on the surface of the stainless steel sheet by electroplating. Glycine (C2H5NO2) is used as a chromium complexing agent, sodium citrate (Na3C6H5O7) is used as a nickel complexing agent, boric acid (H3PO4) is used as a pH buffer, ammonium chloride (NH4Cl) or sodium chloride (NaCl) is used as a conductive salt, and saccharin sodium (C7H4NO3SNa) or sodium lauryl sulfate (NaC) is used as a surfactant. 12 H 25 It is preferable to use a plating solution containing 1,000 ppm or more of nickel, chromium, and phosphorus. By electrolytic plating using such a plating solution, a thin nickel-chromium-phosphorus compound plating layer can be formed on the surface of a thin stainless steel sheet. The thickness of the nickel-chromium-phosphorus compound layer can be adjusted by adjusting the parameters of the electrolytic plating method, such as the current density and plating time.

[0020] An experiment was also conducted on the brazing sheet manufacturing method of the second embodiment using the experimental plating apparatus 20 illustrated in Fig. 1. The plating solution used in the experiment was prepared containing 0.25 mol / L of nickel chloride hexahydrate (NiCl2·6H2O), 0.14 mol / L of sodium hypophosphite monohydrate (NaH2PO2·H2O), 0.4 mol / L of chromium chloride hexahydrate (CrCl3·6H2O), 0.5 mol / L of glycine, 0.2 mol / L of sodium citrate, 0.5 mol / L of boric acid, 0.5 mol / L of ammonium chloride, 0.5 mol / L of sodium chloride, 0.6 g / L of sodium saccharin dihydrate (C7H4NO3SNa·2H2O), and 0.1 g / L of sodium lauryl sulfate. The plating solution 24 was kept at 30°C and pH 1.8, and was sufficiently aerated. The current density flowing through the horizontal part of the stainless steel electrode 28 was set to 10, 15, and 20 [A / dm 2 ] and the total current is 900C / cm 3 Figure 5 shows the plating conditions and plating film components as experimental results. To remove carbon (C) and oxygen (O) from the obtained samples A and B before brazing, they were subjected to melting treatment at 1020°C for 15 minutes in a continuous furnace in a hydrogen atmosphere (dew point: -50°C). Brazing was then performed under the same conditions. Experimental sample A (Ni-6Cr-11P) produced a good joint, with a shear strength of 58.1 MPa. Experimental sample B (Ni-13Cr-12P) also produced a good joint, with a shear strength of 64.6 MPa. The plating film of Experimental sample B (Ni-13Cr-12P) produced by the brazing sheet manufacturing method of the second embodiment is believed to exhibit high corrosion resistance, similar to the plating film (Ni-11Cr-11P) produced by the brazing sheet manufacturing method of the first embodiment.

[0021] In the method for manufacturing a brazing sheet according to the second embodiment described above, a stainless steel sheet is immersed in a plating solution containing nickel chloride as a nickel source, sodium hypophosphite as a phosphorus source, and chromium chloride as a chromium source, to which a chromium complexing agent, a nickel complexing agent, a pH buffer, a conductive salt, and a surfactant have been added, and a thin nickel-chromium-phosphorus compound plating layer is formed on the surface of the stainless steel sheet by electrolytic plating. This makes it possible to manufacture a brazing sheet having a thin, highly corrosion-resistant nickel-chromium-phosphorus compound layer formed on the surface of the stainless steel sheet.

[0022] The above describes the form for carrying out the present invention using examples, but the present invention is not limited to these examples in any way, and it goes without saying that the present invention can be carried out in various forms within the scope that does not deviate from the gist of the present invention. [Industrial Applicability]

[0023] The present invention can be used in the brazing sheet manufacturing industry and the like. [Explanation of symbols]

[0024] 20 Experimental plating apparatus, 22 Plating tank, 24 Plating solution, 26 Nickel electrode, 28 Stainless steel electrode, 30 Power supply unit, 32 Temperature sensor, 34 Heater, 36 Temperature control unit, 38 Aeration pipe, 40 Air pump.

Claims

1. A method for manufacturing a brazing sheet having a thin layer of nickel-chromium-phosphorus compound on the surface of a stainless steel thin plate, comprising: The brazing sheet is manufactured by adding chromium powder to a plating solution containing nickel sulfate, nickel chloride, boric acid, and phosphorous acid, and immersing the stainless steel sheet in the presence of sodium lauryl sulfate and sodium citrate, and forming a thin nickel-chromium-phosphorus compound composite plating layer on the surface of the stainless steel sheet by an electrolytic plating method as the nickel-chromium-phosphorus compound thin layer. A method for manufacturing a brazing sheet, comprising:

2. A method for producing the brazing sheet according to claim 1, The plating solution is prepared so that nickel sulfate hexahydrate is 1.0 mol / L, nickel chloride hexahydrate is 0.2 mol / L, boric acid is 0.5 mol / L, and phosphorous acid is in the range of 0.4 mol / L to 0.8 mol / L, Chromium powder having a purity of 99.9% and an average particle size of 10 μm is added to the plating solution in an amount ranging from 0.1 to 30 g / L, The plating solution contains sodium lauryl sulfate at 0.1 g / L and sodium citrate at 0.5 mol / L. A method for manufacturing a brazing sheet.

3. A method for manufacturing a brazing sheet having a thin layer of nickel-chromium-phosphorus compound on the surface of a stainless steel thin plate, comprising: The brazing sheet is manufactured by immersing the stainless steel sheet in a plating solution containing nickel chloride as a nickel source, sodium hypophosphite as a phosphorus source, and chromium chloride as a chromium source, and also containing a chromium complexing agent, a nickel complexing agent, a pH buffer, a conductive salt, and a surfactant, and forming a thin nickel-chromium-phosphorus compound plating layer on the surface of the stainless steel sheet by electrolytic plating. A method for manufacturing a brazing sheet, comprising:

4. A method for producing the brazing sheet according to claim 3, Glycine is used as a complexing agent for chromium. Sodium citrate is used as a nickel complexing agent. Boric acid is used as a pH buffer, Ammonium chloride and / or sodium chloride is used as the conductive salt, using sodium saccharin and / or sodium lauryl sulfate as surfactants; A method for manufacturing a brazing sheet.

5. A method for producing a brazing sheet according to claim 4, The plating solution is prepared to contain 0.25 mol / L of nickel chloride hexahydrate, 0.14 mol / L of sodium hypophosphite monohydrate, 0.4 mol / L of chromium chloride hexahydrate, 0.5 mol / L of glycine, 0.2 mol / L of sodium citrate, 0.5 mol / L of boric acid, 0.5 mol / L of ammonium chloride, 0.5 mol / L of sodium chloride, 0.6 g / L of sodium saccharin dihydrate, and 0.1 g / L of sodium lauryl sulfate. A method for manufacturing a brazing sheet.

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