Silver-based welding wire for welding high-toughness titanium-steel dissimilar joint and preparation method of silver-based welding wire

Abstract

The silver-based welding wire comprises a flux core and a welding skin, and the flux core is composed of, by mass, 25%-30% of Co powder, 25%-30% of Cr powder, 25%-30% of Ni powder and the balance Ag powder. The welding wire is specially used for solving the problems that when a titanium-steel dissimilar joint is welded, stress is large, and cracking is caused by a Fe-Ti brittle phase. The invention further discloses a preparation method of the silver-based welding wire for welding the high-toughness titanium-steel dissimilar joint.

Description

Technical Field

[0001] The invention belongs to the technical field of metal materials, and in particular relates to a silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding. The invention also relates to a preparation method of the silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding. Background Art

[0002] Steel is one of the most commonly used metal materials in industry due to its low price and mature processing technology. However, with the rapid development of engineering machinery, the use of a single steel material cannot meet the growing manufacturing needs, which has promoted the development of iron-based composite structures. Compared with steel structures, the mass of titanium alloy structures under the same volume can be reduced by nearly half. Replacing the steel structure with titanium alloy can not only give full play to the advantages of titanium alloy such as high specific strength and good corrosion resistance, but also take into account the excellent weldability and cost-effectiveness of steel. Titanium / steel composite structural parts have broad application prospects in the fields of petrochemicals, marine engineering, aerospace, etc. However, due to the large differences in the physical and chemical properties between Ti and Fe, it is difficult to achieve reliable welding of titanium-steel dissimilar materials.

[0003] The difficulty of welding titanium-steel dissimilar materials is that on the one hand, the thermal physical properties of the two are quite different, resulting in greater thermal stress during welding; on the other hand, and most importantly, the two will react to form brittle Fe-Ti intermetallic compounds. Therefore, to achieve high-quality welding connection of titanium-steel, the above two problems must be solved at the same time. Summary of the invention

[0004] The purpose of the present invention is to provide a high-toughness silver-based welding wire for titanium-steel heterogeneous joint welding, which is specially used to solve the cracking problem caused by high stress and Fe-Ti brittle phase during titanium-steel heterogeneous joint welding.

[0005] The second object of the present invention is to provide a method for preparing a silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding.

[0006] The first technical solution adopted by the present invention is a silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding, comprising a flux core and a weld skin, wherein the flux core is composed of the following components by mass percentage: 25-30% Co powder, 25-30% Cr powder, 25-30% Ni powder, and the rest is Ag powder.

[0007] The present invention is also characterized in that: The particle size of each drug powder is 100~200 mesh.

[0008] The purity of each drug powder is ≥99.90%.

[0009] The solder skin is Ag45Cu strip with a thickness of 0.3mm and a width of 7mm.

[0010] The powder filling amount of silver-based welding wire is controlled at 30wt%~32wt%.

[0011] The second technical solution adopted by the present invention is a method for preparing a silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding, and the specific steps are as follows: Step 1: Weigh the powders by mass percentage: Co powder 25-30%, Cr powder 25-30%, Ni powder 25-30%, and the rest is Ag powder. The sum of the mass percentages of the above components is 100%; Step 2: Place the powder weighed in step 1 in a vacuum heating furnace for heating and drying at a temperature of 250-300°C for 1-2 hours to remove the crystal water in the powder; place the dried powder in a powder mixer for sufficient mixing for 1-2 hours; Step 3: Use Ag45Cu strip as welding skin, use alcohol to remove grease on the surface of Ag45Cu strip, and wrap the powder prepared in step 2 in the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6 mm; Step 4: After the first drawing process is completed, the die aperture is reduced in sequence, and finally a flux-cored welding wire with a diameter of 1.2 is obtained; Step 5: After the flux-cored welding wire is drawn, it is wound on the welding wire reel by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for standby use.

[0012] The present invention is also characterized in that: In step 1, the particle size of each drug powder weighed is 100-200 mesh; the purity of each drug powder is ≥99.90%.

[0013] In step 3, the thickness of the Ag45Cu strip is 0.3 mm and the width is 7 mm; the powder filling amount of the silver-based welding wire is controlled at 30 wt% to 32 wt%.

[0014] The beneficial effects of the present invention are: (1) The welding wire of the present invention is designed to address the large difference in thermophysical properties and metallurgical incompatibility (Fe-Ti brittle phase formation) problems that occur when titanium-steel dissimilar materials are welded. A silver-based high-toughness flux-cored welding wire is designed, and by adding a variety of alloy elements, the excellent strength-toughness matching and welding process performance of the welding wire are ensured.

[0015] (2) The present invention adds Co, Cr, and Ni alloy elements to the silver-based welding wire and matches the composition of the Ag45Cu welding skin. The designed weld metal is in the category of high entropy alloy. High entropy alloy has the characteristics of stable crystal structure and excellent comprehensive performance.

[0016] (3) The weld metal formed by the welding wire designed by the present invention has both a face-centered cubic phase (fcc structure) with good toughness and a body-centered cubic structure (bcc structure) with good strength. The weld metal is composed of a two-phase solid solution of fcc and bcc, which can effectively inhibit the diffusion and reaction of Fe and Ti elements, thereby inhibiting the formation of Fe-Ti brittle phase and ensuring excellent joint performance.

[0017] (4) The welding wire of the present invention can be directly welded using a MIG or TIG arc without the need for complex welding operations, and has strong on-site applicability.

[0018] (5) The welding wire developed by the method of the present invention has a small number of powder types and is easy to mass produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a high-magnification microstructure morphology of the titanium-steel heterogeneous joint weld prepared in Example 2 of the present invention; Figure 2 This is the tensile fracture morphology of the titanium-steel heterogeneous joint prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0020] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] The invention provides a silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding, comprising a flux core and a welding skin, wherein the flux core is composed of the following components by mass percentage: 25-30% Co powder, 25-30% Cr powder, 25-30% Ni powder, and the rest is Ag powder, and the sum of the mass percentages of the above components is 100%.

[0022] The particle size of each drug powder is 100~200 mesh.

[0023] The purity of each drug powder is ≥99.90%.

[0024] The solder skin is Ag45Cu strip with a thickness of 0.3mm and a width of 7mm.

[0025] The powder filling amount of silver-based welding wire is controlled at 30wt%~32wt%.

[0026] The roles and functions of the main alloy components in the above-mentioned silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding are as follows: (1) The main elements in the welding wire are Ag and Cu: From the binary phase diagrams of Ag-Ti, Ag-Cu, and Cu-Ti, it can be seen that although Ag and Ti have multiple phase compositions, due to the addition of Cu, Ag-Cu-Ti can form a ternary eutectic structure with good toughness and low melting point. The Cu-Ti intermetallic compounds distributed in the eutectic structure can improve the strength of the joint. From the binary phase diagrams of Ag-Fe and Cu-Fe, it can be seen that Ag and Fe, Cu and Fe will not form brittle phases, but will form solid solution phases with good toughness. From the metallurgical reaction characteristics of the main elements Ag and Cu of the welding wire with titanium and steel, it can be seen that the main solid solution phases in the weld are composed of fcc face-centered cubic phase (Ag-based solid solution, Cu-based solid solution) and bcc iron-based cubic phase (Fe-based solid solution).

[0027] (2) Co is added to the welding wire: From the Ti-Co binary phase diagram, it can be seen that Ti and Co will form a limited solid solution, indicating that welding is possible; from the Fe-Co binary phase diagram, it can be seen that Co and Fe can be infinitely solid-soluble, and the weldability is excellent. Therefore, adding Co to the welding wire can effectively inhibit the reaction of Ti and Fe to form a brittle phase. In addition, Co is one of the important components for forming high-entropy alloy welds.

[0028] (3) Cr is added to the welding wire: From the Ti-Cr binary phase diagram, it can be seen that at high temperature, when Ti is in a bcc structure, the two can be infinitely dissolved; from the Fe-Cr binary phase diagram, it can be seen that the two can be infinitely dissolved at high temperature. Therefore, the addition of Cr can ensure good metallurgical properties with both Ti and Fe. There will be no brittle phase between Cr and the main elements of the weld, Ag and Cu, and mainly Ag-Cu based solid solution and Cr based solid solution will be generated. In addition, Cr is one of the important components for forming high entropy alloy welds.

[0029] (4) Ni is added to the welding wire: From the Ti-Ni binary phase diagram, it can be seen that the two have a certain solid solubility, and the amount of Ni that can be dissolved in fcc-Ti at high temperature reaches 12wt.%; from the Ni-Fe binary phase diagram, it can be seen that the two can be infinitely dissolved, and the welding performance is excellent. Ni can effectively improve the toughness of iron-based welds. In addition, Cr is one of the important components of high-entropy alloy welds.

[0030] (5) Through the combined effect of the above alloying elements, the titanium-steel dissimilar material weld is mainly composed of fcc and bcc phases. The fcc phase mainly consists of Ag-Cu solid solution phase, and the bcc phase mainly consists of Fe-based solid solution phase. The above two solid solution phases fully guarantee the plasticity and toughness of the titanium-steel dissimilar weld and can effectively release welding residual stress. Fe-Ti and Cu-Ti intermetallic compound phases will inevitably be generated in the weld metal. These intermetallic compound phases will be surrounded by the above soft phases with better toughness, thereby playing a role in improving the strength of the weld.

[0031] The present invention also provides a method for preparing a silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding, and the specific steps are as follows: Step 1: Weigh the powders by mass percentage: Co powder 25-30%, Cr powder 25-30%, Ni powder 25-30%, and the rest is Ag powder. The sum of the mass percentages of the above components is 100%; In step 1, the particle size of each drug powder weighed is 100-200 mesh; the purity of each drug powder is ≥99.90%.

[0032] Step 2: Place the powder weighed in step 1 in a vacuum heating furnace for heating and drying at a temperature of 250-300°C for 1-2 hours to remove the crystal water in the powder; place the dried powder in a powder mixer for sufficient mixing for 1-2 hours; Step 3: Use Ag45Cu strip as welding skin, use alcohol to remove grease on the surface of Ag45Cu strip, and wrap the powder prepared in step 2 in the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6 mm; In step 3, the thickness of the Ag45Cu strip is 0.3 mm and the width is 7 mm; the powder filling amount of the silver-based welding wire is controlled at 30 wt% to 32 wt%.

[0033] Step 4: After the first drawing process is completed, the die aperture is reduced in sequence, and finally a flux-cored welding wire with a diameter of 1.2 is obtained; Step 5: After the flux-cored welding wire is drawn, it is wound on the welding wire reel by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for standby use.

[0034] Example 1 Step 1: Weigh the powders according to mass percentage: 25% Co powder, 25% Cr powder, 25% Ni powder, and the rest is Ag powder. The sum of the mass percentages of the above components is 100%; In step 1, the particle size of each drug powder weighed is 100 mesh; the purity of each drug powder is ≥99.90%.

[0035] Step 2: Place the powder weighed in step 1 in a vacuum heating furnace for heating and drying at a temperature of 250°C for 1 hour to remove the crystal water in the powder; place the dried powder in a powder mixer for sufficient mixing for 1 hour; Step 3: Use Ag45Cu strip as welding skin, use alcohol to remove grease on the surface of Ag45Cu strip, and wrap the powder prepared in step 2 in the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6 mm; In step 3, the thickness of the Ag45Cu strip is 0.3 mm and the width is 7 mm; the powder filling amount of the silver-based welding wire is controlled at 30 wt%.

[0036] Step 4: After the first drawing process is completed, the die aperture is reduced in sequence, and finally a flux-cored welding wire with a diameter of 1.2 is obtained; Step 5: After the flux-cored welding wire is drawn, it is wound on the welding wire reel by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for standby use.

[0037] The welding wire of Example 1 was selected for titanium-steel dissimilar material butt welding, the welding current was selected to be 150A, the welding voltage was 12V, the arc was stable during the welding process, the molten pool had good fluidity, and the weld showed no defects such as cracks and pores to the naked eye. After testing, the mechanical properties of the titanium-steel dissimilar material joint are shown in Table 1.

[0038] Table 1 Mechanical properties of titanium-steel dissimilar joints

[0039] Example 2 Step 1: Weigh the powders by mass percentage: 30% Co powder, 30% Cr powder, 30% Ni powder, and the rest is Ag powder. The sum of the mass percentages of the above components is 100%; In step 1, the particle size of each drug powder weighed is 200 mesh; the purity of each drug powder is ≥99.90%.

[0040] Step 2: Place the powder weighed in step 1 in a vacuum heating furnace for heating and drying at a temperature of 300°C for 2 hours to remove the crystal water in the powder; place the dried powder in a powder mixer for sufficient mixing for 2 hours; Step 3: Use Ag45Cu strip as welding skin, use alcohol to remove grease on the surface of Ag45Cu strip, and wrap the powder prepared in step 2 in the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6 mm; In step 3, the thickness of the Ag45Cu strip is 0.3 mm and the width is 7 mm; the powder filling amount of the silver-based welding wire is controlled at 31 wt%.

[0041] Step 4: After the first drawing process is completed, the die aperture is reduced in sequence, and finally a flux-cored welding wire with a diameter of 1.2 is obtained; Step 5: After the flux-cored welding wire is drawn, it is wound on the welding wire reel by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for standby use.

[0042] The welding wire of Example 1 was selected for titanium-steel dissimilar material butt welding, the welding current was selected to be 180A, the welding voltage was 18V, the arc was stable during the welding process, the molten pool had good fluidity, and the weld showed no defects such as cracks and pores to the naked eye. After testing, the mechanical properties of the titanium-steel dissimilar material joint are shown in Table 1.

[0043] Figure 1 This is a high-magnification microstructure morphology of the titanium-steel heterogeneous joint weld prepared in Example 2 of the present invention. It can be seen from the figure that the weld is mainly composed of Ag-Cu based solid solution, Fe based solid solution, and Cu-Ti compound, and the Cu-Ti compound is surrounded by Ag-Cu solid solution and Fe based solid solution.

[0044] Figure 2 This is the tensile fracture morphology of the titanium-steel heterogeneous joint prepared in Example 2 of the present invention. As can be seen from the figure, the fracture surface is mainly composed of dimples, indicating that the titanium-steel dissimilar material joint has good toughness.

[0045] Example 3 Step 1: Weigh the powders by mass percentage: 8% Co powder, 28% Cr powder, 28% Ni powder, and the rest Ag powder. The sum of the mass percentages of the above components is 100%; In step 1, the particle size of each drug powder weighed is 100 mesh; the purity of each drug powder is ≥99.90%.

[0046] Step 2: Place the powder weighed in step 1 in a vacuum heating furnace for heating and drying at a temperature of 280°C for 1.5 hours to remove the crystal water in the powder; place the dried powder in a powder mixer for sufficient mixing for 1.5 hours; Step 3: Use Ag45Cu strip as welding skin, use alcohol to remove grease on the surface of Ag45Cu strip, and wrap the powder prepared in step 2 in the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6 mm; In step 3, the thickness of the Ag45Cu strip is 0.3 mm and the width is 7 mm; the powder filling amount of the silver-based welding wire is controlled at 32 wt%.

[0047] Step 4: After the first drawing process is completed, the die aperture is reduced in sequence, and finally a flux-cored welding wire with a diameter of 1.2 is obtained; Step 5: After the flux-cored welding wire is drawn, it is wound on the welding wire reel by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for standby use.

[0048] The welding wire of Example 1 was selected for titanium-steel dissimilar material butt welding, the welding current was selected as 165A, the welding voltage was 15V, the arc was stable during the welding process, the molten pool had good fluidity, and the weld showed no defects such as cracks and pores to the naked eye. After testing, the mechanical properties of the titanium-steel dissimilar material joint are shown in Table 1.

[0049] Example 4 Step 1: Weigh the powders according to mass percentage: Co powder 27%, Cr powder 27%, Ni powder 27%, and the rest is Ag powder. The sum of the mass percentages of the above components is 100%; In step 1, the particle size of each drug powder weighed is 200 mesh; the purity of each drug powder is ≥99.90%.

[0050] Step 2: Place the powder weighed in step 1 in a vacuum heating furnace for heating and drying at a temperature of 270°C for 1.2 hours to remove the crystal water in the powder; place the dried powder in a powder mixer for sufficient mixing for 1.2 hours; Step 3: Use Ag45Cu strip as welding skin, use alcohol to remove grease on the surface of Ag45Cu strip, and wrap the powder prepared in step 2 in the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6 mm; In step 3, the thickness of the Ag45Cu strip is 0.3 mm and the width is 7 mm; the powder filling amount of the silver-based welding wire is controlled at 30 wt%.

[0051] Step 4: After the first drawing process is completed, the die aperture is reduced in sequence, and finally a flux-cored welding wire with a diameter of 1.2 is obtained; Step 5: After the flux-cored welding wire is drawn, it is wound on the welding wire reel by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for standby use.

[0052] The welding wire of Example 1 was selected for titanium-steel dissimilar material butt welding, the welding current was selected as 160A, the welding voltage was 13V, the arc was stable during the welding process, the molten pool had good fluidity, and the weld showed no defects such as cracks and pores to the naked eye. After testing, the mechanical properties of the titanium-steel dissimilar material joint are shown in Table 1.

[0053] Example 5 Step 1: Weigh the powders according to mass percentage: Co powder 29%, Cr powder 29%, Ni powder 29%, and the rest is Ag powder. The sum of the mass percentages of the above components is 100%; In step 1, the particle size of each drug powder weighed is 100 mesh; the purity of each drug powder is ≥99.90%.

[0054] Step 2: Place the powder weighed in step 1 in a vacuum heating furnace for heating and drying at a temperature of 290°C for 1.8 hours to remove the crystal water in the powder; place the dried powder in a powder mixer for sufficient mixing for 1.8 hours; Step 3: Use Ag45Cu strip as welding skin, use alcohol to remove grease on the surface of Ag45Cu strip, and wrap the powder prepared in step 2 in the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6 mm; In step 3, the thickness of the Ag45Cu strip is 0.3 mm and the width is 7 mm; the powder filling amount of the silver-based welding wire is controlled at 32 wt%.

[0055] Step 4: After the first drawing process is completed, the die aperture is reduced in sequence, and finally a flux-cored welding wire with a diameter of 1.2 is obtained; Step 5: After the flux-cored welding wire is drawn, it is wound on the welding wire reel by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for standby use.

[0056] The welding wire of Example 1 was selected for titanium-steel dissimilar material butt welding, the welding current was selected as 155A, the welding voltage was 14.5V, the arc was stable during the welding process, the molten pool had good fluidity, and the weld showed no defects such as cracks and pores to the naked eye. After testing, the mechanical properties of the titanium-steel dissimilar material joint are shown in Table 1.

[0057] Example 6 Step 1: Weigh the powders according to mass percentage: Co powder 29%, Cr powder 29%, Ni powder 29%, and the rest is Ag powder. The sum of the mass percentages of the above components is 100%; In step 1, the particle size of each drug powder weighed is 100 mesh; the purity of each drug powder is ≥99.90%.

[0058] Step 2: Place the powder weighed in step 1 in a vacuum heating furnace for heating and drying at a temperature of 290°C for 1.8 hours to remove the crystal water in the powder; place the dried powder in a powder mixer for sufficient mixing for 1.8 hours; Step 3: Use Ag45Cu strip as welding skin, use alcohol to remove grease on the surface of Ag45Cu strip, and wrap the powder prepared in step 2 in the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6 mm; In step 3, the thickness of the Ag45Cu strip is 0.3 mm and the width is 7 mm; the powder filling amount of the silver-based welding wire is controlled at 31 wt%.

[0059] Step 4: After the first drawing process is completed, the die aperture is reduced in sequence, and finally a flux-cored welding wire with a diameter of 1.2 is obtained; Step 5: After the flux-cored welding wire is drawn, it is wound on the welding wire reel by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for standby use.

Claims

1. Silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding, characterized in that: The invention comprises a flux core and a welding skin, wherein the flux core is composed of the following components by mass percentage: 25-30% of Co powder, 25-30% of Cr powder, 25-30% of Ni powder, and the rest of Ag powder.

2. The silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding according to claim 1 is characterized in that: The particle size of each drug powder is 100~200 mesh.

3. The silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding according to claim 1 is characterized in that: The purity of each drug powder is ≥99.90%.

4. The silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding according to claim 1 is characterized in that: The soldering sheet is Ag45Cu strip with a thickness of 0.3 mm and a width of 7 mm.

5. The silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding according to claim 1, characterized in that: The powder filling amount of the silver-based welding wire is controlled at 30wt%-32wt%.

6. A method for preparing a silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding, characterized in that: The specific steps are as follows: Step 1: Weigh the powders by mass percentage: Co powder 25-30%, Cr powder 25-30%, Ni powder 25-30%, and the rest is Ag powder. The sum of the mass percentages of the above components is 100%; Step 2: Place the powder weighed in step 1 in a vacuum heating furnace for heating and drying at a temperature of 250-300°C for 1-2 hours to remove the crystal water in the powder; place the dried powder in a powder mixer for sufficient mixing for 1-2 hours; Step 3: Use Ag45Cu strip as welding skin, use alcohol to remove grease on the surface of Ag45Cu strip, and wrap the powder prepared in step 2 in the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6 mm; Step 4: After the first drawing process is completed, the die aperture is reduced in sequence, and finally a flux-cored welding wire with a diameter of 1.2 is obtained; Step 5: After the flux-cored welding wire is drawn, it is wound on the welding wire reel by a wire winding machine and finally sealed in a flux-cored welding wire vacuum packaging bag for standby use.

7. The method for preparing the silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding according to claim 6, characterized in that: In step 1, the particle size of each drug powder weighed is 100-200 mesh; the purity of each drug powder is ≥99.90%.

8. The method for preparing the silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding according to claim 6, characterized in that: In step 3, the thickness of the Ag45Cu strip is 0.3 mm and the width is 7 mm; the powder filling amount of the silver-based welding wire is controlled at 30 wt% to 32 wt%.

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