Smelting flux for transverse welding and preparation method thereof

Abstract

The invention belongs to the field of welding materials, and particularly relates to a smelting flux for transverse welding and a preparation method thereof.Dolomite, flint clay and alumina are adopted for constructing a MgO-Al2O3 slag system framework, through function cooperation of zirconium dioxide, fluorite and barium carbonate, the microalloying effect of low-S and low-P raw materials and zirconium dioxide is controlled, strong support is provided for a transverse welding pool, and therefore the smelting flux for transverse welding is obtained; and metal downward flowing and weld beading formation are effectively prevented, excellent slag detachability is achieved, and it is ensured that weld metal has low-temperature impact toughness.

Description

[0001] This invention belongs to the field of welding materials, specifically, it relates to a molten flux for horizontal welding and its preparation method. Background Technology

[0002] Horizontal welding, as a common welding position, is prone to molten metal flowing downwards due to gravity, leading to defects such as undercut on the upper side and weld beads on the lower side, which places higher demands on the process performance of the flux. Smelted fluxes are widely used due to their good moisture resistance, arc stability, and aesthetically pleasing weld formation, but some problems also exist in horizontal welding applications: insufficient support for the molten pool; the viscosity, solidification temperature, and surface tension of the slag in traditional smelted fluxes are insufficient to effectively support the molten pool and resist metal flow downwards; unsatisfactory slag removal; if the linear expansion coefficient of the slag does not match that of the weld metal, or if the slag shell is too hard or tough, the slag shell is not easy to fall off automatically, requiring manual cleaning and affecting efficiency; and challenges in low-temperature weld toughness. Critical structures operating at low temperatures require welds with excellent low-temperature impact toughness, which requires the flux to effectively desulfurize and dephosphorize, control oxygen content, and finely regulate the alloy composition and microstructure of the weld metal.

[0003] Patent CN100453248C balances the basicity and physical properties of the slag system by introducing the parameter [A] = [CaO] / ([SiO2] + [Al2O3] / 2), aiming to achieve versatility in horizontal, horizontal, and overhead welding positions. Therefore, developing a smelting flux suitable for horizontal welding positions that provides excellent molten pool support, slag removal, and low-temperature toughness in the weld metal is of great significance. Summary of the Invention

[0004] Based on the technical problems mentioned in the background, this invention uses dolomite, coke, and bauxite to construct a MgO-Al2O3 slag framework. Through the functional synergy of zirconium dioxide, fluorite, and barium carbonate, and by controlling the microalloying effect of low S and P raw materials with zirconium dioxide, it provides strong support for the horizontal weld pool, effectively prevents metal from flowing down and weld bead formation, achieves excellent slag removal, and ensures that the weld metal has low-temperature impact toughness.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A molten flux for horizontal welding, wherein the welding direction is parallel to the ground, and the flux raw materials include dolomite, calcined gemstone and bauxite, wherein the mass ratio of dolomite, calcined gemstone and bauxite is 4~6: 2.5~3.5: 1.5~2.5.

[0006] Furthermore, by mass percentage, the dolomite comprises CaCO3 ≥ 30.0% and MgO ≥ 18.0%; the calcined alumina comprises Al2O3 ≥ 45% and SiO2 ≥ 45%; and the bauxite comprises Al2O3 ≥ 70.0% and SiO2 ≤ 15.0%.

[0007] Furthermore, in dolomite, calcined gemstone, and bauxite, S≤0.040 and P≤0.030.

[0008] Furthermore, the particle size of dolomite and calcined gemstone is ≤20 mesh, and the particle size of bauxite is ≤30 mesh.

[0009] Furthermore, the flux raw materials also include fluorite and zirconium dioxide, wherein the fluorite and zirconium dioxide contain S≤0.010, P≤0.010, and the particle size of the fluorite and zirconium dioxide is ≤40 mesh.

[0010] Furthermore, the flux raw materials also include quartz, titanium dioxide, barium carbonate, and manganese ore, wherein the manganese ore and quartz contain S≤0.035 and P≤0.025; the barium carbonate contains S≤0.040 and P≤0.030; the particle size of the quartz is ≤20 mesh, and the particle size of the barium carbonate, manganese ore, and titanium dioxide is ≤40 mesh.

[0011] Furthermore, the flux raw materials are composed of the following components in parts by weight: 18-28 parts dolomite, 12-22 parts calcined bauxite, 8-18 parts bauxite, 12-22 parts quartz, 10-16 parts fluorite, 3-7 parts zirconium dioxide, 2-6 parts titanium dioxide, 2-5 parts barium carbonate, and 0.5-3 parts manganese ore.

[0012] The present invention also provides a method for preparing the above-mentioned smelting flux for horizontal welding, comprising the following steps: Step 1) Weigh out the required weights as described above; Step 2) Place dolomite, quartz, calcined gemstone, and bauxite into a smelting furnace for smelting. Then add fluorite and zirconium dioxide. After the materials in the furnace have melted evenly, add manganese ore and titanium dioxide in sequence, and finally add barium carbonate. The total time from feeding to the end of smelting should be controlled at 45 to 70 minutes. Step 3) The molten material is water-cooled and granulated, followed by wet magnetic separation; Step 4) Dry the granulated raw material after magnetic separation at 380-450℃ to ensure that the moisture content of the flux after drying is ≤0.08%; Step 5) Mechanical crushing and screening, with a screening mesh size of 12-70 mesh, to obtain the final product.

[0013] Furthermore, in step 1), the dolomite, quartz, and calcined gemstone are preheated at 250°C.

[0014] Furthermore, in step 2), the current of the melting circuit is 2800A.

[0015] The present invention has the following beneficial effects: This invention uses dolomite, coke, and bauxite to construct a MgO-Al2O3 slag framework, which improves the high-temperature viscosity and solidification rate of the slag, provides strong support for the horizontal welding pool, and effectively prevents metal from flowing down and weld beads from forming. This invention utilizes the synergistic effect of zirconium dioxide, fluorite, and barium carbonate, taking advantage of the negative expansion coefficient of zirconium dioxide, the dilution effect of fluorite, and the modifying effect of barium carbonate, to cause the slag shell to automatically lift up due to internal stress during cooling, thus achieving excellent slag removal performance.

[0016] This invention selects raw materials with low S and P content and combines them with wet magnetic separation process to reduce the impurity content and oxygen content in the weld. At the same time, zirconium dioxide introduces trace amounts of zirconium into the weld, which plays a role in refining the grains and ensuring that the weld metal has excellent low-temperature impact toughness. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] Example 1 23 parts dolomite, 17 parts quartz, and 17 parts calcined alumina were preheated at 250°C for 1 hour. The preheated raw materials, along with 13 parts bauxite, were placed in a melting furnace and smelted at 2800A. Subsequently, 13 parts fluorite and 5 parts zirconium dioxide were added. After the materials in the furnace had basically melted and formed a homogeneous melt, 1.5 parts manganese ore and 4 parts titanium dioxide were added sequentially, and finally 3.5 parts barium carbonate were added. The total time from material feeding to the end of smelting was controlled within 60 minutes. The resulting molten flux was discharged from the furnace and water-cooled and granulated using a 0.8MPa high-pressure water flow. The granulated wet slag was then subjected to wet magnetic separation. The granulated raw material after magnetic separation was placed in a drying furnace and dried at 420°C for 2 hours to reduce the moisture content to below 0.05%. The dried flux was mechanically crushed, and particles between 12-70 mesh were collected by vibrating sieve to obtain the molten flux for horizontal welding.

[0019] Example 2 20 parts dolomite, 15 parts quartz, and 15 parts calcined alumina were preheated at 250°C for 1 hour. The preheated raw materials, along with 10 parts bauxite, were placed in a melting furnace and smelted at 2800A. Subsequently, 11 parts fluorite and 4 parts zirconium dioxide were added. After the materials in the furnace had basically melted and formed a homogeneous melt, 1 part manganese ore, 3 parts titanium dioxide, and finally 3 parts barium carbonate were added. The total time from material feeding to the end of smelting was controlled within 50 minutes. The resulting molten flux was discharged from the furnace and water-cooled and granulated using a 0.8MPa high-pressure water jet. The granulated wet slag was then subjected to wet magnetic separation. The granulated raw material after magnetic separation was placed in a drying furnace and dried at 400°C for 2 hours until the moisture content was reduced to below 0.05%. The dried flux was mechanically crushed and particles between 12 and 70 mesh were collected by vibrating sieve to obtain the molten flux for horizontal welding.

[0020] Example 3 26 parts dolomite, 20 parts quartz, and 19 parts calcined alumina were preheated at 250°C for 1 hour. The preheated raw materials, along with 16 parts bauxite, were placed in a melting furnace and smelted at 2800A. Subsequently, 15 parts fluorite and 6 parts zirconium dioxide were added. After the materials in the furnace had basically melted and formed a homogeneous melt, 2.5 parts manganese ore, 5 parts titanium dioxide, and finally 4 parts barium carbonate were added. The total time from material feeding to the end of smelting was controlled within 70 minutes. The resulting molten flux was discharged from the furnace and water-cooled and granulated using a 0.8MPa high-pressure water flow. The granulated wet slag was then subjected to wet magnetic separation. The granulated raw material after magnetic separation was placed in a drying furnace and dried at 450°C for 2 hours until the moisture content was reduced to below 0.05%. The dried flux was mechanically crushed and particles between 12 and 70 mesh were collected by vibrating sieve to obtain the molten flux for horizontal welding.

[0021] Comparative Example A commercially available general-purpose fusion flux (HJ431D) is used, whose composition and preparation method are different from those of this invention.

[0022] Performance testing The fluxes from Examples 1-3 and the comparative example were tested. Before the welding test, the fluxes were baked at 250℃ for 2 hours. ERNiCrMo-4 submerged arc welding wire was used. Taking a Φ4.0 mm wire as an example, the welding position was horizontal welding. The welding process parameters were: DC reverse polarity welding power supply, welding current 320~350A, welding voltage 28~30V, and interpass temperature 100~150℃. The test results are as follows: Table 1. Chemical composition (wt%) of weld metal deposited with flux matched to ERNiCrMo-4 welding wire in examples and comparative cases.

[0023] Table 2 Mechanical properties of weld metal deposited with flux matched to ERNiCrMo-4 welding wire in examples and comparative cases

[0024] Table 3 Evaluation of Flux Process Performance

[0025] As shown in Tables 1-3, the tensile strength of the horizontal welding flux and welding wire proposed in this invention is greater than 670 MPa, the average impact energy at -40℃ exceeds 90 J, and the weld has good low-temperature toughness. This invention selects raw materials with low S and P content to reduce the impurity content and oxygen content in the weld. At the same time, zirconium dioxide introduces trace amounts of zirconium into the weld, which plays a role in refining the grains and ensuring that the weld metal has excellent low-temperature impact toughness.

[0026] This invention uses dolomite, coke, and bauxite to construct a MgO-Al2O3 slag framework, which improves the high-temperature viscosity and solidification rate of the slag, provides strong support for the horizontal welding pool, and effectively prevents metal from flowing down and weld beads from forming.

[0027] This invention utilizes the synergistic effect of zirconium dioxide, fluorite, and barium carbonate, taking advantage of the negative expansion coefficient of zirconium dioxide, the dilution effect of fluorite, and the modifying effect of barium carbonate, to cause the slag shell to automatically lift up due to internal stress during cooling, thus achieving excellent slag removal performance.

[0028] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flux for horizontal welding, wherein the welding direction is parallel to the ground, characterized in that, The flux raw materials include dolomite, calcined sapphire and bauxite, wherein the mass ratio of dolomite, calcined sapphire and bauxite is 4~6: 2.5~3.5: 1.5~2.

5.

2. The flux for horizontal welding according to claim 1, characterized in that, By mass percentage, the dolomite comprises CaCO3 ≥ 30.0% and MgO ≥ 18.0%; the calcined alumina comprises Al2O3 ≥ 45% and SiO2 ≥ 45%; and the bauxite comprises Al2O3 ≥ 70.0% and SiO2 ≤ 15.0%.

3. The flux for horizontal welding according to claim 2, characterized in that, In dolomite, calcined gemstone, and bauxite, S≤0.040 and P≤0.

030.

4. The flux for horizontal welding according to claim 2, characterized in that, The particle size of dolomite and calcined gemstone is ≤20 mesh, and the particle size of bauxite is ≤30 mesh.

5. The flux for horizontal welding according to claim 1, characterized in that, The flux raw materials also include fluorite and zirconium dioxide, wherein the fluorite and zirconium dioxide contain S≤0.010, P≤0.010, and the particle size of the fluorite and zirconium dioxide is ≤40 mesh.

6. The flux for horizontal welding according to claim 5, characterized in that, The flux raw materials also include quartz, titanium dioxide, barium carbonate, and manganese ore, wherein the manganese ore and quartz contain S≤0.035 and P≤0.025; the barium carbonate contains S≤0.040 and P≤0.030; the particle size of the quartz is ≤20 mesh, and the particle size of the barium carbonate, manganese ore, and titanium dioxide is ≤40 mesh.

7. The flux for horizontal welding according to claim 1, characterized in that, The flux raw materials consist of the following components in parts by weight: 18-28 parts dolomite, 12-22 parts calcined bauxite, 8-18 parts bauxite, 12-22 parts quartz, 10-16 parts fluorite, 3-7 parts zirconium dioxide, 2-6 parts titanium dioxide, 2-5 parts barium carbonate, and 0.5-3 parts manganese ore.

8. A method for preparing a molten flux for horizontal welding as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1) Weigh out the required weights as described above; Step 2) Place dolomite, quartz, calcined gemstone, and bauxite into a smelting furnace for smelting. Then add fluorite and zirconium dioxide. After the materials in the furnace have melted evenly, add manganese ore and titanium dioxide in sequence, and finally add barium carbonate. The total time from feeding to the end of smelting should be controlled at 45 to 70 minutes. Step 3) The molten material is water-cooled and granulated, followed by wet magnetic separation; Step 4) Dry the granulated raw material after magnetic separation at 380-450℃ to ensure that the moisture content of the flux after drying is ≤0.08%; Step 5) Mechanical crushing and screening, with a screening mesh size of 12-70 mesh, to obtain the final product.

9. The method for preparing molten flux for horizontal welding according to claim 8, characterized in that, In step 1), the dolomite, quartz, and calcined gemstone are preheated at 250°C.

10. The method for preparing molten flux for horizontal welding according to claim 8, characterized in that, In step 2), the current in the melting circuit is 2800A.

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