Tantalum / Q345R steel special brazing filler metal, preparation method and brazing process

Abstract

The present invention discloses a special tantalum / Q345R steel brazing filler metal. The filler metal is composed of the following components by mass percentage: Ni 2% to 5%, Sn 2% to 5%, In 2% to 5%, Ti 1% to 5%, Ag2WO4 1% to 2%, Ce 0% to 1%, and the balance being AgCu eutectic. The present invention also discloses a preparation method and brazing process for the special tantalum / Q345R steel brazing filler metal. The special tantalum / Q345R steel brazing filler metal uses the AgCu eutectic as a matrix and employs Ni, Sn, Ti, In, Ce, and Ag2WO4 to synergistically regulate the properties of the AgCu eutectic. This can enhance the plasticity of the brazing filler metal and the bonding strength of the tantalum / Q345R steel joint after welding, enabling the tantalum and Q345R steel to be connected by brazing. The filler metal is suitable for connecting tantalum and Q345R steel in the field of dissimilar material welding technology.

Description

Technical Field

[0001] The invention belongs to the technical field of welding dissimilar materials, and in particular relates to a special brazing filler metal for tantalum / Q345R steel, a preparation method thereof, and a brazing process. Background Art

[0002] Pressure vessels, as specialized pressure-bearing equipment with potential leakage and explosion risks, are widely used and play an indispensable role in all sectors of the national economy and national defense. With the rapid advancement of science and technology and the continuous innovation of industrial technology, the design, manufacturing, and performance requirements of pressure vessels have reached unprecedented heights. Given the stringent standards for pressure vessels' pressure capacity and sealing performance, selecting the right material is crucial to ensuring their safe and efficient operation. Among numerous materials, tantalum, due to its unique physical and chemical properties, has gradually become the preferred material for the manufacture of high-performance pressure vessels.

[0003] Since the refining process of tantalum is complex and the production cost is high, the cost can be reduced and the material structure can be lightweight by compounding dissimilar metals. Among them, Q345R steel is a widely used steel for pressure vessels, which has the characteristics of good weldability, high yield strength, good toughness, and good ductility. Its production technology and cost are relatively more economical and popular. In order to reduce costs and at the same time give full play to the performance advantages of tantalum and Q345R steel, compounding the two to achieve high-strength connection has become a potential research direction. At present, explosive welding is an effective solution for connecting tantalum and Q345R steel, but it has problems such as complex process, high cost, and greater damage to the environment. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of the prior art by providing a special tantalum / Q345R steel brazing filler metal. This tantalum / Q345R steel brazing filler metal utilizes a AgCu eutectic as a matrix and employs Ni, Sn, Ti, In, Ce, and Ag2WO4 to synergistically regulate the properties of the AgCu eutectic. This filler metal enhances the filler metal's plasticity and the bond strength of the tantalum / Q345R steel joint after brazing, enabling the brazing of tantalum and Q345R steel. This addresses the complex, high-cost, and environmentally damaging explosive welding processes employed in the prior art.

[0005] To achieve the above-mentioned object, the technical solution adopted by the present invention is: a special tantalum / Q345R steel solder, characterized in that the solder is composed of the following components in mass percentage: Ni 2% to 5%, Sn 2% to 5%, In 2% to 5%, Ti 1% to 5%, Ag2WO4 1% to 2%, Ce 0% to 1%, and the balance is AgCu eutectic.

[0006] The present invention adopts AgCu eutectic as the matrix of the tantalum / Q345R steel special solder, and almost no intermetallic compound (IMC) is generated between the matrix and Ta and Fe elements, which is conducive to obtaining relatively excellent welding performance.

[0007] The present invention also discloses a method for preparing the above-mentioned tantalum / Q345R steel special solder, which is characterized in that the preparation method comprises the following steps:

[0008] Step 1: Adding Na2WO4 solution during the stirring process of AgNO4 solution to obtain a precipitate suspension;

[0009] Step 2: Wash the precipitate suspension obtained in step 1 several times, filter and dry it to obtain Ag2WO4 powder;

[0010] Step 3: The Ag2WO4 powder obtained in step 2 and the AgCu eutectic alloy powder, Ni powder, Sn powder, Ti powder, In powder and Ce powder are mixed with anhydrous ethanol and ultrasonically stirred, and then heated and stirred until the anhydrous ethanol is completely volatilized, and then three-dimensionally shaken and mixed to obtain a composite powder;

[0011] Step 4: The composite powder obtained in step 3 is placed in a mold and pressed under a pressure of 50 MPa to 150 MPa, and then the temperature is raised to 600° C. to 700° C. for primary vacuum sintering to obtain a primary sintered block;

[0012] Step 5: Pressing the primary sintered block obtained in step 4 under a pressure of 150 MPa to 300 MPa, and then heating to 600° C. to 700° C. for secondary vacuum sintering to obtain a secondary sintered block;

[0013] Step 6: Pressing the secondary sintered block obtained in step 5 under a pressure of 850 MPa or higher, and then heating to 550° C. to 650° C. and performing vacuum sintering three times to obtain a tertiary sintered block;

[0014] Step 7: Roll the tertiary sintered block obtained in step 6, then heat it to 600°C to 700°C and anneal it. Repeat the process of rolling first and then annealing until the thickness of the tertiary sintered block is no more than 200μm to obtain a tantalum / Q345R steel special brazing filler metal.

[0015] The present invention can promote the internal exhaust of the solder and improve the density of the solder by performing three pressing and sintering. Among them, the first pressing molding sets the pressure at 50MPa to 150MPa, which can ensure that the internal gas is fully discharged and natural shrinkage occurs; the second pressing molding sets the pressure at 150MPa to 300MPa, while improving the density of the primary sintered block, still retaining the exhaust channel, so that the density of the primary sintered block is improved; the third pressing molding sets the pressure at more than 850MPa, further improving the density of the secondary sintered block and ensuring subsequent processing performance; by setting the pressure of the three pressing steps to rise, a high-density tertiary sintered block can be obtained.

[0016] The above-mentioned method for preparing a special tantalum / Q345R steel solder is characterized in that the concentrations of the AgNO4 solution and the Na2WO4 solution in step 1 are both 0.1 mol / L to 0.5 mol / L, and the molar ratio of the solute in the AgNO4 solution to the Na2WO4 solution is not greater than 2:1.

[0017] The above-mentioned method for preparing a special tantalum / Q345R steel solder is characterized in that the particle size of the Ag2WO4 powder in step 2 is not greater than 300nm.

[0018] The above-mentioned method for preparing a special tantalum / Q345R steel solder is characterized in that the particle size of the AgCu eutectic alloy powder in step three is 5μm~20μm, and the mass purity is not less than 99.9%; the particle size of the Ni powder is 0.5μm~3μm, and the mass purity is not less than 99.9%; the particle size of the Sn powder is 1μm~5μm, and the mass purity is not less than 99.9%; the particle size of the Ti powder is 1μm~5μm, and the mass purity is not less than 99.9%; the particle size of the In powder is 1μm~5μm, and the mass purity is not less than 99.9%; the particle size of the Ce powder is 1μm~5μm, and the mass purity is not less than 99.9%.

[0019] The above-mentioned method for preparing a special tantalum / Q345R steel solder is characterized in that the heating rates in step four, step five, step six and step seven are all 5°C / min to 10°C / min.

[0020] The present invention is used to ensure uniform temperature inside and outside the material by controlling the heating rate.

[0021] The method for preparing the above-mentioned tantalum / Q345R steel special solder is characterized in that the deformation amount of the single rolling in step seven is 30% to 70%.

[0022] In addition, the present invention discloses a brazing process for the above-mentioned tantalum / Q345R steel special brazing filler metal, characterized in that the brazing process comprises the following steps:

[0023] Step 1: Polish the tantalum / Q345R steel special brazing filler metal and lay it between the tantalum and Q345R steel to form a tantalum / AgCu-based brazing filler metal / Q345R steel structural component, and fix it to obtain the component to be brazed;

[0024] Step 2: Place the components to be brazed obtained in step 1 in a vacuum brazing furnace and evacuate to 5×10 -3 After Pa, heat it to 600℃~670℃ and keep it warm, then heat it to 750℃~850℃ and keep it warm, and finally cool it with the furnace.

[0025] The above-mentioned brazing process is characterized in that the fixing method described in step one is: the edges and end points of the tantalum / AgCu-based solder / Q345R steel structure component are fixed with a clamp, and a pressure of 1kPa to 3kPa is applied to the top center of the tantalum / AgCu-based solder / Q345R steel structure component.

[0026] The present invention can ensure uniform weld thickness by fixing the edges and end points of a tantalum / AgCu-based solder / Q345R steel structural component and applying pressure to the center, thereby avoiding welding defects caused by edge warping and improving the mechanical properties of the weld.

[0027] The brazing process is characterized in that the heating rate in step 2 is 5°C / min to 15°C / min, and the cooling rate is 3°C / min to 5°C / min.

[0028] The present invention is used to prevent internal stress and thermal cracks in the weld by controlling the cooling rate.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. The present invention uses AgCu eutectic as a matrix to lower the melting point of the solder, thereby avoiding the degradation of Q235 steel performance due to excessively high brazing temperatures. Ni, Sn, Ti, In, Ce, and Ag2WO4 are used to synergistically regulate the performance of the AgCu eutectic. The addition of Ti reacts with Ta to form a good connection, but easily generates a brittle phase. The addition of Ni inhibits the generation of brittle phases and effectively refines the solder structure. Ni also reacts with Ta, and the combination of the two enhances plasticity, improving joint bonding strength, corrosion resistance, and high-temperature performance. However, excessive Ni and Ti increase the solidus-liquidus temperature of the solder. Therefore, the addition of Sn and In can appropriately lower the solder melting point and regulate the weld structure, improving weld uniformity. The addition of Ce and Ag2WO4 further regulates the phase interface and improves the spreading wettability of the solder. Through the combined effects of the above elements and components, a brazing filler metal suitable for brazing tantalum and Q345R steel can be obtained, avoiding the complex, high-cost and environmental damage caused by explosive welding.

[0031] 2. The preparation method of the present invention generates small-sized Ag2WO4 by adding Na2WO4 solution while stirring AgNO4 solution, which can form a coating on other phase particles, melt and flow during the sintering process, and help to regulate the solder structure and wettability; at the same time, since the melting point of Ag2WO4 is about 600℃~650℃, the temperature is first raised to 600℃~670℃ and kept warm during the brazing process, so that Ag2WO4 is melted first, which is beneficial to improve the spreading wettability of the solder and reduce weld defects.

[0032] 3. The preparation method of the solder of the present invention adopts three-dimensional oscillation powder mixing to maximize the uniformity of the composition of the solder, avoiding the different sedimentation rates due to the differences in specific gravity and particle size of the powder particles in the early stirring process, which in turn leads to limited powder uniformity in some areas; then, by performing three pressing and sintering, the solder can be continuously shrunk, the gas content inside the solder can be reduced, the workability of the solder rolling can be improved, and it can be ensured that there is no bulging problem after rolling and annealing.

[0033] 4. The solder prepared by the present invention has easy controllable composition, no segregation problem, and has good processing performance and welding performance.

[0034] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the metallographic structure diagram of the tantalum / Q345R steel special solder obtained in Example 1 of the present invention.

[0036] Figure 2This is the metallographic structure diagram of the tantalum / Q345R steel weld obtained in Example 3 of the present invention. DETAILED DESCRIPTION

[0037] Example 1

[0038] The solder of this embodiment is composed of the following components in mass percentage: Ni 2%, Sn 2%, In 2%, Ti 5%, Ag2WO41%, Ce 1%, and the balance is AgCu eutectic. The preparation method of the solder comprises the following steps:

[0039] Step 1, adding a 0.1 mol / L Na2WO4 solution to a 0.1 mol / L AgNO4 solution during stirring to obtain a precipitate suspension; the molar ratio of the solute in the AgNO4 solution to that in the Na2WO4 solution is not greater than 2:1;

[0040] Step 2: The precipitate suspension obtained in step 1 was washed several times and then filtered and dried to obtain Ag2WO4 powder with a particle size of 300 nm;

[0041] Step 3. According to the composition of the target solder, AgCu eutectic alloy powder, Ni powder, Sn powder, Ti powder, In powder, Ce powder and the Ag2WO4 powder obtained in step 2 are weighed, mixed with anhydrous ethanol, and ultrasonically stirred. Then, heated and stirred until the anhydrous ethanol is completely volatilized, and then three-dimensionally shaken and mixed to obtain a composite powder; the particle size of the AgCu eutectic alloy powder is 20 μm, and the mass purity is not less than 99.9%; the particle size of the Ni powder is 3 μm, and the mass purity is not less than 99.9%; the particle size of the Sn powder is 5 μm, and the mass purity is not less than 99.9%; the particle size of the Ti powder is 5 μm, and the mass purity is not less than 99.9%; the particle size of the In powder is 5 μm, and the mass purity is not less than 99.9%, and the particle size of the Ce powder is 5 μm, and the mass purity is not less than 99.9%;

[0042] Step 4: The composite powder obtained in step 3 is placed into a mold and pressed at a pressure of 150 MPa for 2 minutes, and then the vacuum degree is less than 10 -3 Pa, the temperature was raised to 700 °C at a rate of 10 °C / min and vacuum sintered for 2 h to obtain a primary sintered block;

[0043] Step 5: The primary sintered block obtained in step 4 is pressed into shape at a pressure of 300 MPa for 2 minutes, and then the vacuum degree is less than 10 -3 Pa, the temperature was raised to 700 °C at a rate of 10 °C / min and subjected to secondary vacuum sintering for 2 h to obtain a secondary sintered block;

[0044] Step 6: The secondary sintered block obtained in step 5 is pressed into shape at a pressure of 850 MPa for 2 minutes, and then the vacuum degree is less than 10 -3 Pa, the temperature was raised to 650 °C at a rate of 10 °C / min and vacuum sintered for three times for 1 h to obtain a three-times sintered block;

[0045] Step 7: The tertiary sintered block obtained in step 6 is rolled once using a double-roll mill with a deformation of 30% to 70%, and then the vacuum degree is less than 10 -3 Pa, the temperature was raised to 700°C at a rate of 10°C / min and then annealed for 2h. The process of first rolling and then annealing was repeated until the thickness of the thrice-sintered block was no more than 200μm, and a special tantalum / Q345R steel brazing filler metal was obtained.

[0046] The metallographic structure of the tantalum / Q345R steel special brazing filler metal obtained in this embodiment was analyzed. Figure 1 As shown in the figure, the solder exhibits obvious Ag-Cu eutectic, indicating that the components of the solder are fully fused and there are no defects such as pores.

[0047] The brazing process using the above-mentioned brazing filler metal comprises the following steps:

[0048] Step 1: Polish the tantalum / Q345R steel special brazing filler metal to 100 μm and then lay it between the tantalum and Q345R steel to form a tantalum / AgCu-based brazing filler metal / Q345R steel structural component. Fix the edges and end points of the tantalum / AgCu-based brazing filler metal / Q345R steel structural component with a clamp, and apply a pressure of 1 kPa at the top center of the tantalum / AgCu-based brazing filler metal / Q345R steel structural component to obtain the component to be brazed;

[0049] Step 2: Place the components to be brazed obtained in step 1 in a vacuum brazing furnace and evacuate to 5×10 -3 After Pa, the temperature was raised to 600℃ at a rate of 5℃ / min and kept for 10min, then raised to 850℃ at a rate of 5℃ / min and kept for 20min, and finally cooled with the furnace at a rate of 3℃ / min to 5℃ / min to obtain a tantalum / Q345R steel weld.

[0050] Example 2

[0051] The solder of this embodiment is composed of the following components in percentage by mass: Ni 5%, Sn 5%, In 5%, Ti 3%, Ag2WO42%, Ce 1%, and the balance is AgCu eutectic. The preparation method of the solder comprises the following steps:

[0052] Step 1, adding a 0.3 mol / L Na2WO4 solution during stirring of a 0.3 mol / L AgNO4 solution to obtain a precipitate suspension; the molar ratio of the solute in the AgNO4 solution to that in the Na2WO4 solution is not greater than 2:1;

[0053] Step 2: The precipitate suspension obtained in step 1 was washed several times and then filtered and dried to obtain Ag2WO4 powder with a particle size of 200 nm;

[0054] Step 3. According to the composition of the target solder, AgCu eutectic alloy powder, Ni powder, Sn powder, Ti powder, In powder, Ce powder and the Ag2WO4 powder obtained in step 2 are weighed, mixed with anhydrous ethanol, and ultrasonically stirred, and then heated and stirred until the anhydrous ethanol is completely volatilized, and then three-dimensionally shaken and mixed to obtain a composite powder; the particle size of the AgCu eutectic alloy powder is 5 μm, and the mass purity is not less than 99.9%; the particle size of the Ni powder is 0.5 μm, and the mass purity is not less than 99.9%; the particle size of the Sn powder is 1 μm, and the mass purity is not less than 99.9%; the particle size of the Ti powder is 1 μm, and the mass purity is not less than 99.9%; the particle size of the In powder is 1 μm, and the mass purity is not less than 99.9%, and the particle size of the Ce powder is 1 μm, and the mass purity is not less than 99.9%;

[0055] Step 4: put the composite powder obtained in step 3 into the mold and press it under a pressure of 50 MPa for 5 minutes, and then press it under a vacuum degree of less than 10 -3 Pa, the temperature was raised to 600 °C at a rate of 5 °C / min and vacuum sintered for 3 h to obtain a primary sintered block;

[0056] Step 5: The primary sintered block obtained in step 4 is pressed into shape at a pressure of 150 MPa for 5 minutes, and then the vacuum degree is less than 10 -3 Pa, the temperature was raised to 600 °C at a rate of 5 °C / min and subjected to secondary vacuum sintering for 3 h to obtain a secondary sintered block;

[0057] Step 6: The secondary sintered block obtained in step 5 is pressed into shape at a pressure of 850 MPa for 5 minutes, and then the vacuum degree is less than 10 -3 Pa, the temperature was raised to 550 °C at a rate of 5 °C / min and vacuum sintered for three times for 2 h to obtain a three-times sintered block;

[0058] Step 7: The tertiary sintered block obtained in step 6 is rolled once using a double-roll rolling mill with a deformation of 30% to 70%, and then the vacuum degree is less than 10 -3Pa, the temperature was raised to 600°C at a rate of 5°C / min and then annealed for 3h. The process of rolling followed by annealing was repeated until the thickness of the thrice-sintered block was no more than 200μm, thereby obtaining a special tantalum / Q345R steel brazing filler metal.

[0059] The brazing process using the above-mentioned brazing filler metal comprises the following steps:

[0060] Step 1: Polish the tantalum / Q345R steel special brazing filler metal to 80 μm and then lay it between the tantalum and Q345R steel to form a tantalum / AgCu-based brazing filler metal / Q345R steel structural component. Fix the edges and end points of the tantalum / AgCu-based brazing filler metal / Q345R steel structural component with a clamp, and apply a pressure of 2 kPa at the top center of the tantalum / AgCu-based brazing filler metal / Q345R steel structural component to obtain the component to be brazed.

[0061] Step 2: Place the components to be brazed obtained in step 1 in a vacuum brazing furnace and evacuate to 5×10 -3 After Pa, the temperature was raised to 600℃ at a rate of 10℃ / min and kept for 10min, then raised to 750℃ at a rate of 10℃ / min and kept for 15min, and finally cooled with the furnace at a rate of 3℃ / min to 5℃ / min to obtain a tantalum / Q345R steel weld.

[0062] Example 3

[0063] The solder of this embodiment is composed of the following components in mass percentage: Ni 3%, Sn 4%, In 3%, Ti 1%, Ag2WO42%, and the balance is AgCu eutectic. The preparation method of the solder comprises the following steps:

[0064] Step 1, adding a 0.2 mol / L Na2WO4 solution during stirring of a 0.2 mol / L AgNO4 solution to obtain a precipitate suspension; the molar ratio of the solute in the AgNO4 solution to that in the Na2WO4 solution is not greater than 2:1;

[0065] Step 2: The precipitate suspension obtained in step 1 was washed several times and then filtered and dried to obtain Ag2WO4 powder with a particle size of 260 nm;

[0066] Step 3. According to the composition of the target solder, AgCu eutectic alloy powder, Ni powder, Sn powder, Ti powder, In powder, Ce powder and the Ag2WO4 powder obtained in step 2 are weighed, mixed with anhydrous ethanol, and ultrasonically stirred, and then heated and stirred until the anhydrous ethanol is completely volatilized, and then three-dimensionally shaken and mixed to obtain a composite powder; the particle size of the AgCu eutectic alloy powder is 8 μm, and the mass purity is not less than 99.9%; the particle size of the Ni powder is 1 μm, and the mass purity is not less than 99.9%; the particle size of the Sn powder is 2 μm, and the mass purity is not less than 99.9%; the particle size of the Ti powder is 2 μm, and the mass purity is not less than 99.9%; the particle size of the In powder is 2 μm, and the mass purity is not less than 99.9%;

[0067] Step 4: The composite powder obtained in step 3 is placed in a mold and pressed at a pressure of 100 MPa for 3 minutes, and then the vacuum degree is less than 10 -3 Pa, the temperature was raised to 650 °C at a rate of 8 °C / min and vacuum sintered for 3 h to obtain a primary sintered block;

[0068] Step 5: Press the primary sintered block obtained in step 4 under a pressure of 200 MPa for 3 minutes, and then press the block under a vacuum of less than 10 -3 Pa, the temperature was raised to 650 °C at a rate of 8 °C / min and vacuum sintered for 3 h to obtain a secondary sintered block;

[0069] Step 6: The secondary sintered block obtained in step 5 is pressed into shape at a pressure of 850 MPa for 3 minutes, and then the vacuum degree is less than 10 -3 Pa, the temperature was raised to 650 °C at a rate of 8 °C / min and vacuum sintered for 3 h to obtain a tertiary sintered block;

[0070] Step 7: The tertiary sintered block obtained in step 6 is rolled once using a double-roll mill with a deformation of 30% to 70%, and then the vacuum degree is less than 10 -3 Pa, the temperature was raised to 650°C at a rate of 8°C / min and then annealed for 3h. The process of rolling followed by annealing was repeated until the thickness of the thrice-sintered block was no more than 200μm, thereby obtaining a special tantalum / Q345R steel brazing filler metal.

[0071] The brazing process using the above-mentioned brazing filler metal comprises the following steps:

[0072] Step 1: Polish the tantalum / Q345R steel special brazing filler metal to 80 μm and then lay it between the tantalum and Q345R steel to form a tantalum / AgCu-based brazing filler metal / Q345R steel structural component. Fix the edges and end points of the tantalum / AgCu-based brazing filler metal / Q345R steel structural component with a clamp, and apply a pressure of 3 kPa at the top center of the tantalum / AgCu-based brazing filler metal / Q345R steel structural component to obtain the component to be brazed;

[0073] Step 2: Place the components to be brazed obtained in step 1 in a vacuum brazing furnace and evacuate to 5×10 -3 After Pa, the temperature was raised to 600℃ at a rate of 15℃ / min and kept for 10min, then raised to 800℃ at a rate of 15℃ / min and kept for 18min, and finally cooled with the furnace at a rate of 3℃ / min to 5℃ / min to obtain a tantalum / Q345R steel weld.

[0074] The metallographic structure of the tantalum / Q345R steel weld obtained in this embodiment was analyzed. Figure 2 As shown in the figure, the weld and the base materials on both sides show obvious transition layers, indicating that obvious atomic diffusion occurs at the interface and the welding quality is good.

[0075] Example 4

[0076] The solder of this embodiment is composed of the following components in percentage by mass: Ni 4%, Sn 4%, In 3%, Ti 2%, Ag2WO4 2%, Ce 1%, and the balance is AgCu eutectic. The preparation method of the solder comprises the following steps:

[0077] Step 1, adding a 0.5 mol / L Na2WO4 solution during stirring of a 0.5 mol / L AgNO4 solution to obtain a precipitate suspension; the molar ratio of the solute in the AgNO4 solution to that in the Na2WO4 solution is not greater than 2:1;

[0078] Step 2: The precipitate suspension obtained in step 1 was washed several times and then filtered and dried to obtain Ag2WO4 powder with a particle size of 100 nm;

[0079] Step 3. According to the composition of the target solder, AgCu eutectic alloy powder, Ni powder, Sn powder, Ti powder, In powder, Ce powder and the Ag2WO4 powder obtained in step 2 are weighed, mixed with anhydrous ethanol, and ultrasonically stirred, and then heated and stirred until the anhydrous ethanol is completely volatilized, and then three-dimensionally shaken and mixed to obtain a composite powder; the particle size of the AgCu eutectic alloy powder is 12 μm, and the mass purity is not less than 99.9%; the particle size of the Ni powder is 1 μm, and the mass purity is not less than 99.9%; the particle size of the Sn powder is 2 μm, and the mass purity is not less than 99.9%; the particle size of the Ti powder is 2 μm, and the mass purity is not less than 99.9%; the particle size of the In powder is 2 μm, and the mass purity is not less than 99.9%, and the particle size of the Ce powder is 2 μm, and the mass purity is not less than 99.9%;

[0080] Step 4: put the composite powder obtained in step 3 into the mold and press it under a pressure of 50 MPa for 5 minutes, and then press it under a vacuum degree of less than 10 -3 Pa, the temperature was raised to 670 °C at a rate of 5 °C / min and vacuum sintered for 3 h to obtain a primary sintered block;

[0081] Step 5: The primary sintered block obtained in step 4 is pressed into shape at a pressure of 150 MPa for 5 minutes, and then the vacuum degree is less than 10 -3 Pa, the temperature was raised to 670 °C at a rate of 5 °C / min and subjected to secondary vacuum sintering for 3 h to obtain a secondary sintered block;

[0082] Step 6: The secondary sintered block obtained in step 5 is pressed into shape at a pressure of 850 MPa for 5 minutes, and then the vacuum degree is less than 10 -3 Pa, the temperature was raised to 620 °C at a rate of 5 °C / min and vacuum sintered for three times for 2 h to obtain a three-times sintered block;

[0083] Step 7: The tertiary sintered block obtained in step 6 is rolled once using a double-roll mill with a deformation of 30% to 70%, and then the vacuum degree is less than 10 -3 Pa, the temperature was raised to 600°C at a rate of 5°C / min and then annealed for 3h. The process of rolling followed by annealing was repeated until the thickness of the thrice-sintered block was no more than 200μm, thereby obtaining a special tantalum / Q345R steel brazing filler metal.

[0084] The brazing process using the above-mentioned brazing filler metal comprises the following steps:

[0085] Step 1: Polish the tantalum / Q345R steel special brazing filler metal to 100 μm and then lay it between the tantalum and Q345R steel to form a tantalum / AgCu-based brazing filler metal / Q345R steel structural component. Fix the edges and end points of the tantalum / AgCu-based brazing filler metal / Q345R steel structural component with a clamp, and apply a pressure of 2 kPa at the top center of the tantalum / AgCu-based brazing filler metal / Q345R steel structural component to obtain the component to be brazed;

[0086] Step 2: Place the components to be brazed obtained in step 1 in a vacuum brazing furnace and evacuate to 5×10 -3 After Pa, the temperature was raised to 670℃ at a rate of 15℃ / min and kept for 10min, then raised to 820℃ at a rate of 15℃ / min and kept for 18min, and finally cooled with the furnace at a rate of 3℃ / min to 5℃ / min to obtain a tantalum / Q345R steel weld.

[0087] The tantalum / Q345R steel welds obtained in Examples 1 to 4 were subjected to shear strength tests. The results are shown in Table 1.

[0088] Table 1 Shear strength of tantalum / Q345R steel welds in Examples 1 to 4

[0089] sample Weld strength / MPa Example 1 145.6 Example 2 178.4 Example 3 163.3 Example 4 154.5

[0090] As shown in Table 1, the shear strength of the tantalum / Q345R steel welds obtained in Examples 1 to 4 is greater than 140 MPa, indicating that the brazing filler metal and the brazing process of the present invention can effectively connect tantalum and Q345R steel.

[0091] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural transformation made to the above embodiment based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A tantalum / Q345R steel special brazing filler metal, the brazing filler metal comprising the following components in percentage by mass: Ni 2%~5%, Sn 2%~5%, In 2%~5%, Ti 1%~5%, Ag2WO4 1%~2%, Ce 0%~1%, and the balance is AgCu eutectic. The preparation method of the solder comprises the following steps: Step 1: Adding Na2WO4 solution during the stirring process of AgNO4 solution to obtain a precipitate suspension; Step 2: Wash the precipitate suspension obtained in step 1 several times, filter and dry it to obtain Ag2WO4 powder; Step 3: The Ag2WO4 powder obtained in step 2 and the AgCu eutectic alloy powder, Ni powder, Sn powder, Ti powder, In powder and Ce powder are mixed with anhydrous ethanol and ultrasonically stirred, and then heated and stirred until the anhydrous ethanol is completely volatilized, and then three-dimensionally shaken and mixed to obtain a composite powder; Step 4: The composite powder obtained in step 3 is placed in a mold and pressed under a pressure of 50 MPa to 150 MPa, and then heated to 600° C. to 700° C. for primary vacuum sintering to obtain a primary sintered block; Step 5: Pressing the primary sintered block obtained in step 4 under a pressure of 150 MPa to 300 MPa, and then heating to 600° C. to 700° C. for secondary vacuum sintering to obtain a secondary sintered block; Step 6: Pressing the secondary sintered block obtained in step 5 under a pressure of 850 MPa or higher, and then heating it to 550°C to 650°C for three vacuum sintering to obtain a tertiary sintered block; Step 7: Roll the tertiary sintered block obtained in step 6, then heat it to 600°C~700°C and anneal it. Repeat the process of rolling first and then annealing until the thickness of the tertiary sintered block is no more than 200μm to obtain a tantalum / Q345R steel special brazing filler metal.

2. The tantalum / Q345R steel special brazing filler metal according to claim 1, characterized in that: The concentrations of the AgNO4 solution and the Na2WO4 solution in step 1 are both 0.1 mol / L to 0.5 mol / L, and the molar ratio of the solute in the AgNO4 solution to that in the Na2WO4 solution is not greater than 2:

1.

3. The tantalum / Q345R steel special brazing filler metal according to claim 1, characterized in that: The particle size of the Ag2WO4 powder in step 2 is not greater than 300 nm.

4. The tantalum / Q345R steel special brazing filler metal according to claim 1, characterized in that: The particle size of the AgCu eutectic alloy powder in step three is 5μm~20μm, and the mass purity is not less than 99.9%; the particle size of the Ni powder is 0.5μm~3μm, and the mass purity is not less than 99.9%; the particle size of the Sn powder is 1μm~5μm, and the mass purity is not less than 99.9%; the particle size of the Ti powder is 1μm~5μm, and the mass purity is not less than 99.9%; the particle size of the In powder is 1μm~5μm, and the mass purity is not less than 99.9%, and the particle size of the Ce powder is 1μm~5μm, and the mass purity is not less than 99.9%.

5. The tantalum / Q345R steel special brazing filler metal according to claim 1, characterized in that: The heating rates in step 4, step 5, step 6 and step 7 are all 5°C / min to 10°C / min.

6. The tantalum / Q345R steel special brazing filler metal according to claim 1, characterized in that: The deformation of the first rolling in step seven is 30% to 70%.

7. A brazing process using the tantalum / Q345R steel special brazing filler metal according to any one of claims 1 to 6, characterized in that: The brazing process includes the following steps: Step ①, polishing the tantalum / Q345R steel special brazing filler metal and laying it between the tantalum and Q345R steel to form a tantalum / AgCu-based brazing filler metal / Q345R steel structural component, and fixing it to obtain the component to be brazed; Step ②: Place the components to be brazed obtained in step ① in a vacuum brazing furnace and evacuate to 5×10 -3 After Pa, heat it up to 600℃~670℃ and keep it warm, then heat it up to 750℃~850℃ and keep it warm, and finally cool it with the furnace.

8. The brazing process according to claim 7, characterized in that: The fixing method described in step ① is: fix the edges and end points of the tantalum / AgCu-based solder / Q345R steel structure component with a clamp, and apply a pressure of 1kPa~3kPa at the top center of the tantalum / AgCu-based solder / Q345R steel structure component.

9. The brazing process according to claim 7, characterized in that: The heating rate in step ② is 5°C / min~15°C / min, and the cooling rate is 3°C / min~5°C / min.

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