Silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding and preparation method

Abstract

The present invention discloses a high-toughness silver-based welding wire for welding titanium-steel dissimilar joints. The wire comprises a flux core and a welding sheath. The flux core is composed, by mass, of the following components: 25-30% Co powder, 25-30% Cr powder, 25-30% Ni powder, and the remainder Ag powder. This welding wire is specifically designed to address the cracking problems caused by high stress and Fe-Ti brittle phases during titanium-steel dissimilar joint welding. The present invention also discloses a method for preparing the high-toughness silver-based welding wire for titanium-steel dissimilar joint welding.

Description

Technical Field

[0001] The present 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 present 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 of the same volume can be reduced by nearly half. Replacing steel structures with titanium alloys can not only take advantage of the high specific strength and good corrosion resistance of titanium alloys, but also take into account the excellent weldability and cost-effectiveness of steel. Titanium / steel composite structures have broad application prospects in fields such as petrochemicals, marine engineering, and aerospace. 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 in welding titanium and steel dissimilar materials lies, firstly, in the significant difference in their thermophysical properties, which results in high thermal stress during welding; secondly, and most importantly, in the reaction between the two, which forms a brittle Fe-Ti intermetallic compound. Therefore, achieving high-quality titanium-steel welds requires addressing both of these issues simultaneously. 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 specifically 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 dissimilar joint welding.

[0006] The first technical solution adopted by the present invention is a silver-based welding wire for high-toughness titanium-steel dissimilar 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:

[0008] The particle size of each powder is 100~200 mesh.

[0009] The purity of each drug powder is ≥99.90%.

[0010] The solder skin is Ag45Cu strip with a thickness of 0.3mm and a width of 7mm.

[0011] The powder filling amount of silver-based welding wire is controlled at 30wt%~32wt%.

[0012] 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:

[0013] 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%;

[0014] 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; the dried powder is placed in a powder mixer for thorough mixing for 1-2 hours;

[0015] Step 3: Use Ag45Cu strip as welding skin, remove grease on the surface of Ag45Cu strip with alcohol, and wrap the powder prepared in step 2 inside the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6mm.

[0016] Step 4: After the first drawing process is completed, the die aperture is reduced in sequence to finally obtain a flux-cored welding wire with a diameter of 1.2 mm;

[0017] Step 5: After the flux-cored wire is drawn, it is wound onto a wire reel by a wire winding machine and finally sealed in a flux-cored wire vacuum packaging bag for use.

[0018] The present invention is also characterized in that:

[0019] In step 1, the particle size of each drug powder weighed is 100-200 mesh; the purity of each drug powder is ≥99.90%.

[0020] 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%.

[0021] The beneficial effects of the present invention are:

[0022] (1) The welding wire of the present invention is designed to solve the problems of large difference in thermophysical properties and metallurgical incompatibility (Fe-Ti brittle phase formation) when titanium-steel dissimilar materials are welded. A silver-based high-toughness flux-cored welding wire is designed, and by adding a variety of alloying elements, the excellent strength-toughness matching and welding process performance of the welding wire are guaranteed.

[0023] (2) The present invention adds Co, Cr, and Ni alloy elements to the silver-based welding wire, and combines them with the composition of the Ag45Cu welding skin. The designed weld metal falls within the category of high-entropy alloys. High-entropy alloys have the characteristics of stable crystal structure and excellent comprehensive performance.

[0024] (3) The weld metal formed by the welding wire designed in this invention contains 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 suppressing the formation of Fe-Ti brittle phases and ensuring excellent joint performance.

[0025] (4) The welding wire of the present invention can be directly welded with MIG or TIG arc without complicated welding operations, and has strong on-site applicability.

[0026] (5) The welding wire developed by the method of the present invention has fewer types of powder and is convenient for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a high-magnification microstructure morphology of the titanium-steel heterogeneous joint weld prepared in Example 2 of the present invention;

[0028] Figure 2 This is the tensile fracture morphology of the titanium-steel heterogeneous joint prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] The present invention provides a silver-based welding wire for high-toughness titanium-steel dissimilar joint welding, comprising a flux core and a welding sheath, 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 remainder Ag powder, and the sum of the mass percentages of the above components is 100%.

[0031] The particle size of each powder is 100~200 mesh.

[0032] The purity of each drug powder is ≥99.90%.

[0033] The solder skin is Ag45Cu strip with a thickness of 0.3mm and a width of 7mm.

[0034] The powder filling amount of silver-based welding wire is controlled at 30wt%~32wt%.

[0035] The roles and functions of the main alloy components in the above-mentioned silver-based welding wire for high-toughness titanium-steel dissimilar joint welding are as follows:

[0036] (1) The main elements in the welding wire are Ag and Cu: From the Ag-Ti, Ag-Cu, and Cu-Ti binary phase diagrams, it can be seen that although Ag and Ti can 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 this eutectic structure can actually play a role in improving the joint strength. From the Ag-Fe and Cu-Fe binary phase diagrams, 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 in 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).

[0037] (2) Co is added to the welding wire: From the Ti-Co binary phase diagram, it can be seen that Ti and Co 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 form an infinite solid solution, indicating excellent weldability. Therefore, adding Co to the welding wire can effectively inhibit the reaction between Ti and Fe to form a brittle phase. In addition, Co is one of the important components of forming high-entropy alloy welds.

[0038] (3) Cr is added to the welding wire: From the Ti-Cr binary phase diagram, it can be seen that at high temperatures, 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 temperatures. Therefore, the addition of Cr can ensure good metallurgical properties with both Ti and Fe. There will be no brittle phase formation between Cr and the main elements of the weld, Ag and Cu, and the main solid solution is Ag-Cu based solid solution and Cr based solid solution. In addition, Cr is one of the important components of the formation of high entropy alloy welds.

[0039] (4) Ni is added to the welding wire: The Ti-Ni binary phase diagram shows that the two have a certain solid solubility, and at high temperatures, the amount of Ni that can be dissolved in fcc-Ti reaches 12 wt.%. The Ni-Fe binary phase diagram shows that the two can be dissolved infinitely, resulting in excellent welding performance. Ni can effectively improve the toughness of iron-based welds. In addition, Cr is one of the important components of high-entropy alloy welds.

[0040] (5) Through the combined effects 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 an Ag-Cu solid solution phase, and the bcc phase mainly consists of an 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 are inevitably generated in the weld metal. These intermetallic compound phases will be surrounded by the above soft phases with better toughness, thereby improving the weld strength.

[0041] The present invention also provides a method for preparing a high-toughness silver-based welding wire for welding titanium-steel heterogeneous joints, the specific steps of which are as follows:

[0042] 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%;

[0043] In step 1, the particle size of each drug powder weighed is 100-200 mesh; the purity of each drug powder is ≥99.90%.

[0044] 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; the dried powder is placed in a powder mixer for thorough mixing for 1-2 hours;

[0045] Step 3: Use Ag45Cu strip as welding skin, remove grease on the surface of Ag45Cu strip with alcohol, and wrap the powder prepared in step 2 inside the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6mm.

[0046] 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%.

[0047] Step 4: After the first drawing process is completed, the die aperture is reduced in sequence to finally obtain a flux-cored welding wire with a diameter of 1.2 mm;

[0048] Step 5: After the flux-cored wire is drawn, it is wound onto a wire reel by a wire winding machine and finally sealed in a flux-cored wire vacuum packaging bag for use.

[0049] Example 1

[0050] Step 1: Weigh the powders by mass percentage: 25% Co powder, 25% Cr powder, 25% Ni powder, and the rest Ag powder. The sum of the mass percentages of the above components is 100%;

[0051] In step 1, the particle size of each drug powder weighed is 100 mesh; the purity of each drug powder is ≥99.90%.

[0052] 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; the dried powder is placed in a powder mixer for thorough mixing, and the mixing time is 1 hour;

[0053] Step 3: Use Ag45Cu strip as welding skin, remove grease on the surface of Ag45Cu strip with alcohol, and wrap the powder prepared in step 2 inside the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6mm.

[0054] 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%.

[0055] Step 4: After the first drawing process is completed, the die aperture is reduced in sequence to finally obtain a flux-cored welding wire with a diameter of 1.2 mm;

[0056] Step 5: After the flux-cored wire is drawn, it is wound onto a wire reel by a wire winding machine and finally sealed in a flux-cored wire vacuum packaging bag for use.

[0057] The welding wire of Example 1 was used for butt welding of titanium and steel dissimilar materials. The welding current was 150A and 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 or pores to the naked eye. The mechanical properties of the titanium-steel dissimilar material joint are shown in Table 1.

[0058] Table 1 Mechanical properties of titanium-steel dissimilar joints

[0059]

[0060] Example 2

[0061] Step 1: Weigh the powders by mass percentage: 30% Co powder, 30% Cr powder, 30% Ni powder, and the rest Ag powder. The sum of the mass percentages of the above components is 100%;

[0062] In step 1, the particle size of each drug powder weighed is 200 mesh; the purity of each drug powder is ≥99.90%.

[0063] Step 2: The powder weighed in step 1 is placed 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; the dried powder is placed in a powder mixer for thorough mixing for 2 hours;

[0064] Step 3: Use Ag45Cu strip as welding skin, remove grease on the surface of Ag45Cu strip with alcohol, and wrap the powder prepared in step 2 inside the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6mm.

[0065] 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%.

[0066] Step 4: After the first drawing process is completed, the die aperture is reduced in sequence to finally obtain a flux-cored welding wire with a diameter of 1.2 mm;

[0067] Step 5: After the flux-cored wire is drawn, it is wound onto a wire reel by a wire winding machine and finally sealed in a flux-cored wire vacuum packaging bag for use.

[0068] The welding wire of Example 1 was used for titanium-steel dissimilar material butt welding. The welding current was 180A and 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 or pores to the naked eye. The mechanical properties of the titanium-steel dissimilar material joint are shown in Table 1.

[0069] Figure 1 This is a high-magnification microstructure image of the titanium-steel dissimilar joint weld prepared in Example 2 of the present invention. As can be seen from the figure, 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.

[0070] 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.

[0071] Example 3

[0072] Step 1: Weigh the powders by mass percentage: Co powder 8%, Cr powder 28%, Ni powder 28%, and the rest is Ag powder. The sum of the mass percentages of the above components is 100%;

[0073] In step 1, the particle size of each drug powder weighed is 100 mesh; the purity of each drug powder is ≥99.90%.

[0074] Step 2: The powder weighed in step 1 is placed 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; the dried powder is placed in a powder mixer for thorough mixing for 1.5 hours;

[0075] Step 3: Use Ag45Cu strip as welding skin, remove grease on the surface of Ag45Cu strip with alcohol, and wrap the powder prepared in step 2 inside the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6mm.

[0076] 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%.

[0077] Step 4: After the first drawing process is completed, the die aperture is reduced in sequence to finally obtain a flux-cored welding wire with a diameter of 1.2 mm;

[0078] Step 5: After the flux-cored wire is drawn, it is wound onto a wire reel by a wire winding machine and finally sealed in a flux-cored wire vacuum packaging bag for use.

[0079] The welding wire of Example 1 was used for butt welding of titanium and steel dissimilar materials. The welding current was 165A and 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 or pores to the naked eye. The mechanical properties of the titanium-steel dissimilar material joint are shown in Table 1.

[0080] Example 4

[0081] Step 1: Weigh the powders by 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%;

[0082] In step 1, the particle size of each drug powder weighed is 200 mesh; the purity of each drug powder is ≥99.90%.

[0083] Step 2: The powder weighed in step 1 is placed 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; the dried powder is placed in a powder mixer for thorough mixing for 1.2 hours;

[0084] Step 3: Use Ag45Cu strip as welding skin, remove grease on the surface of Ag45Cu strip with alcohol, and wrap the powder prepared in step 2 inside the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6mm.

[0085] 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%.

[0086] Step 4: After the first drawing process is completed, the die aperture is reduced in sequence to finally obtain a flux-cored welding wire with a diameter of 1.2 mm;

[0087] Step 5: After the flux-cored wire is drawn, it is wound onto a wire reel by a wire winding machine and finally sealed in a flux-cored wire vacuum packaging bag for use.

[0088] The welding wire of Example 1 was used for butt welding of titanium and steel dissimilar materials. The welding current was 160A and 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 or pores to the naked eye. The mechanical properties of the titanium-steel dissimilar material joint are shown in Table 1.

[0089] Example 5

[0090] Step 1: Weigh the powders by 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%;

[0091] In step 1, the particle size of each drug powder weighed is 100 mesh; the purity of each drug powder is ≥99.90%.

[0092] Step 2: The powder weighed in step 1 is placed 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; the dried powder is placed in a powder mixer for thorough mixing for 1.8 hours;

[0093] Step 3: Use Ag45Cu strip as welding skin, remove grease on the surface of Ag45Cu strip with alcohol, and wrap the powder prepared in step 2 inside the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6mm.

[0094] 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%.

[0095] Step 4: After the first drawing process is completed, the die aperture is reduced in sequence to finally obtain a flux-cored welding wire with a diameter of 1.2 mm;

[0096] Step 5: After the flux-cored wire is drawn, it is wound onto a wire reel by a wire winding machine and finally sealed in a flux-cored wire vacuum packaging bag for use.

[0097] The welding wire of Example 1 was used for butt welding of titanium and steel dissimilar materials. The welding current was 155A and 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 or pores to the naked eye. The mechanical properties of the titanium-steel dissimilar material joint are shown in Table 1.

[0098] Example 6

[0099] Step 1: Weigh the powders by 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%;

[0100] In step 1, the particle size of each drug powder weighed is 100 mesh; the purity of each drug powder is ≥99.90%.

[0101] Step 2: The powder weighed in step 1 is placed 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; the dried powder is placed in a powder mixer for thorough mixing for 1.8 hours;

[0102] Step 3: Use Ag45Cu strip as welding skin, remove grease on the surface of Ag45Cu strip with alcohol, and wrap the powder prepared in step 2 inside the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6mm.

[0103] 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%.

[0104] Step 4: After the first drawing process is completed, the die aperture is reduced in sequence to finally obtain a flux-cored welding wire with a diameter of 1.2 mm;

[0105] Step 5: After the flux-cored wire is drawn, it is wound onto a wire reel by a wire winding machine and finally sealed in a flux-cored wire vacuum packaging bag for use.

Claims

1. Silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding, characterized in that: The method comprises 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; The solder paste is Ag45Cu strip with a thickness of 0.3 mm and a width of 7 mm; The powder filling amount of the silver-based welding wire is controlled to be 30wt% to 32wt%.

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

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

4. 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; the dried powder is placed in a powder mixer for thorough mixing for 1-2 hours; Step 3: Use Ag45Cu strip as welding skin, remove grease on the surface of Ag45Cu strip with alcohol, and wrap the powder prepared in step 2 inside the Ag45Cu strip through flux-cored wire drawing equipment. The aperture of the first drawing die is 2.6mm. 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%; Step 4: After the first drawing process is completed, the die aperture is reduced in sequence to finally obtain a flux-cored welding wire with a diameter of 1.2 mm; Step 5: After the flux-cored wire is drawn, it is wound onto a wire reel by a wire winding machine and finally sealed in a flux-cored wire vacuum packaging bag for use.

5. The method for preparing a silver-based welding wire for high-toughness titanium-steel heterogeneous joint welding according to claim 4, 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%.

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