Composite flux and preparation method thereof

Abstract

The present invention provides a high-performance composite flux and a preparation method thereof. A high-performance composite flux comprises the following components by mass percentage: SiO 2 16%~19%, TiO 2 7% to 9% of tungsten (Mg), 18% to 20% of CaO, 15% to 18% of MnO, 22% to 25% of CaF2, 0.4% to 0.6% of Y, and 13% to 17% of Al-Mg alloy. This high-performance composite flux is a sintered flux with low slag viscosity and excellent slag removal after welding. The weld has excellent mechanical properties and can maintain good mechanical properties even in extreme environments.

Description

Technical Field

[0001] The present invention relates to the technical field of welding, in particular to a composite flux and a preparation method thereof. Background Art

[0002] Welding technology is one of the core processes of modern industrial manufacturing, and the quality of its welds directly determines the reliability and safety of engineering structures. In submerged arc welding, flux, as the key medium for metallurgical reactions, performs important functions such as protecting the molten pool, stabilizing the arc, and participating in alloying. Sintered flux, through a granulation process, combines the advantages of precise controllable composition with efficient mechanized production. It is widely used in welding applications such as pipelines and ships, where strict requirements are placed on weld mechanical properties and corrosion resistance.

[0003] In recent years, fluorine-alkali sintered fluxes have significantly improved the desulfurization and dephosphorization efficiency during welding by optimizing the ratio of fluoride to alkaline oxides, while effectively reducing the oxygen content in the weld, thereby improving the low-temperature impact toughness of the weld metal. However, existing technologies still face two major challenges: first, excessive fluoride can easily cause welding fume pollution, posing an environmental risk; second, the dynamic matching between the flux composition and the molten pool reaction is insufficient, resulting in post-weld corrosion resistance that is difficult to meet the requirements of extreme environments such as marine engineering.

[0004] Therefore, the present invention is specially proposed to solve the above technical problems. Summary of the Invention

[0005] The first purpose of the present invention is to provide a composite flux, which has excellent arc stability during the welding process, good slag removal and weld formability after welding, and the weld surface obtained after welding has no obvious defects such as pores and cracks. In addition, the obtained weld has corrosion resistance while maintaining excellent mechanical properties and can adapt to the needs of extreme environments.

[0006] The second object of the present invention is to provide a method for preparing the composite flux.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0008] The present invention first provides a composite flux, which is composed of the following components by mass percentage: SiO2 16%-19%, TiO2 7%-9%, CaO 18%-20%, MnO 15%-18%, CaF2 22%-25%, Y 0.4%-0.6% and Al-Mg alloy 13%-17%.

[0009] Preferably, the slag removal rate of the composite flux weld is ≥94%.

[0010] Preferably, the impact toughness of the weld using the composite flux in a simulated seawater extreme environment at -40°C is ≥98J;

[0011] The tensile strength of the weld using the composite flux in a simulated seawater extreme environment for 30 days is ≥645 MPa;

[0012] The yield strength of the weld using the composite flux in a simulated seawater extreme environment for 30 days is ≥533 MPa;

[0013] The elongation of the weld using the composite flux in a simulated seawater extreme environment for 30 days is ≥29%.

[0014] The present invention further provides a method for preparing the composite flux, comprising the following steps:

[0015] S1. Weigh SiO2, TiO2, CaO, MnO, CaF2, Y, and Al-Mg alloy in proportion and put them into a mixer. Add sodium water glass and stir at 15-20 r / min for 15-20 minutes.

[0016] S2, the wet mixed material is granulated into balls by a disc, and the balls are put into a dryer for drying;

[0017] S3, passing the dried flux particles through a 10-60 mesh sieve to obtain a semi-finished flux;

[0018] S4. Put the semi-finished flux into a muffle furnace for sintering to obtain a finished flux.

[0019] Preferably, in step S2, the pelletized material is dried at 200-250° C. for 30-60 minutes.

[0020] Preferably, in step S4, the semi-finished flux is sintered at 700-800° C. for 2-3 hours.

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

[0022] 1. The composite flux provided by the present invention has excellent slag removal after welding, beautiful weld shape, stable arc during welding, and excellent weld mechanical properties.

[0023] 2. The composite flux provided by the present invention has a moderate content of CaF2 components, which can reduce the formation of pores in the weld, improve the fluidity of the flux, ensure uniform coverage of the welding area, and reduce the pollution to the environment caused by excessive CaF2 components.

[0024] 3. The composite flux provided by the present invention, by adding heavy rare earth yttrium powder and aluminum-magnesium alloy, is beneficial to improving the strength, corrosion resistance and thermal stability of the weld metal, so that the weld metal can still maintain excellent mechanical properties under extreme environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart for preparing the flux of the present invention;

[0026] Figure 2 This is a scanning electron microscope image of the microstructure of the weld obtained after welding using the flux prepared in Comparative Example 1 of the present invention;

[0027] Figure 3 This is a scanning electron microscope image of the microstructure of the weld obtained after welding with the flux prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0028] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0029] Example 1

[0030] The composite flux provided in this embodiment is composed of the following components in percentage by mass: SiO 2: 16%, TiO 2: 7%, CaO: 20%, MnO: 17%, CaF 2: 23%, Y: 0.4%, Al-Mg alloy: 16.6%.

[0031] The preparation method of the composite flux provided in this embodiment includes the following steps:

[0032] S1. Weigh SiO2, TiO2, CaO, MnO, CaF2, Y, and Al-Mg alloy according to the mass ratio and put them into a mixer. Add sodium water glass and mix at 15 r / min for 20 minutes.

[0033] S2. The wet mixed material is granulated into balls by a disc, and then put into a dryer for drying at a temperature of 200°C and a drying time of 60 minutes;

[0034] S3, passing the dried flux particles through a 10-60 mesh sieve to obtain a semi-finished flux;

[0035] S4. Put the semi-finished flux into a muffle furnace for sintering at a sintering temperature of 700° C. for 3 h to obtain a finished flux.

[0036] Example 2

[0037] The composite flux provided in this embodiment is composed of the following components in percentage by mass: SiO 2:17%, TiO 2: 8%, CaO: 18%, MnO: 15%, CaF 2: 25%, Y: 0.5%, Al-Mg alloy: 16.5%.

[0038] The preparation method of the composite flux provided in this embodiment includes the following steps:

[0039] S1. Weigh SiO2, TiO2, CaO, MnO, CaF2, Y, and Al-Mg alloy according to the mass ratio and put them into a mixer. Add sodium water glass and mix at 20 r / min for 15 minutes.

[0040] S2, the wet mixed material is disc granulated into balls, and after the balls are put into the dryer for drying, the drying temperature is 250 ° C, and the drying time is 45 min;

[0041] S3, passing the dried flux particles through a 10-60 mesh sieve to obtain a semi-finished flux;

[0042] S4. Put the semi-finished flux into a muffle furnace for sintering at a sintering temperature of 750° C. for 2.5 h to obtain a finished flux.

[0043] Example 3

[0044] The composite flux provided in this embodiment is composed of the following components in percentage by mass: SiO 2: 19%, TiO 2: 9%, CaO: 18%, MnO: 15%, CaF 2: 22%, Y: 0.6%, Al-Mg alloy: 16.4%.

[0045] The preparation method of the composite flux provided in this embodiment includes the following steps:

[0046] S1. Weigh SiO2, TiO2, CaO, MnO, CaF2, Y, and Al-Mg alloy according to the mass ratio and put them into a mixer. Add sodium water glass and stir at 17 rpm for 15 minutes.

[0047] S2, the wet mixed material is disc granulated into balls, and then put into the dryer for drying at a temperature of 300 ° C and a drying time of 30 min;

[0048] S3, passing the dried flux particles through a 10-60 mesh sieve to obtain a semi-finished flux;

[0049] S4. Put the semi-finished flux into a muffle furnace for sintering at a temperature of 800° C. for 2 h to obtain a finished flux.

[0050] Comparative Example 1

[0051] The sintered flux provided in this comparative example is composed of the following components by mass percentage: SiO 2: 19%, TiO 2: 9%, CaO: 18%, MnO: 15%, CaF 2: twenty two%.

[0052] The preparation method of the sintered flux provided in this comparative example is basically the same as that of Example 3.

[0053] Comparative Example 2

[0054] The sintered flux provided in this comparative example is composed of the following components by mass percentage: SiO 2: 19%, TiO 2: 9%, CaO: 18%, MnO: 15%, CaF 2: 22%, Y: 0.6%.

[0055] The preparation method of the sintered flux provided in this comparative example is basically the same as that of Example 3.

[0056] Comparative Example 3

[0057] The sintered flux provided in this comparative example is composed of the following components by mass percentage: SiO 2: 19%, TiO 2: 9%, CaO: 18%, MnO: 15%, CaF 2: 22%, Al-Mg alloy: 16.4%.

[0058] The preparation method of the sintered flux provided in this comparative example is basically the same as that of Example 3.

[0059] Experimental Example 1

[0060] The fluxes prepared in each embodiment and each comparative example were tested for slag removal performance, and the results are shown in Table 1.

[0061] The slag removal performance test is carried out using the falling ball method. A steel ball with a mass of 100 g is dropped from 1 m above the steel plate into the weld in a free-fall state with an initial velocity of 0. The flux slag shell that falls each time is collected and measured, and the slag shell that does not fall off is cleaned and weighed. Each group is repeated 3 times.

[0062] Table 1 Slag removal rate test of each flux

[0063]

[0064] As can be seen from Table 1, in each embodiment, the slag removal efficiency after welding is greatly improved. Comparative Example 1 has a lower slag removal efficiency because no yttrium powder and aluminum-magnesium alloy are added. Comparative Example 2 adds yttrium powder but no aluminum-magnesium alloy, and the slag removal performance is slightly worse than that of Comparative Example 3.

[0065] Experimental Example 2

[0066] The fluxes described in the embodiment and comparative example were dried in a drying oven at 350°C for 2 hours before welding. Then, the dried sintered flux was combined with submerged arc welding wire H08MnA to weld Q390 carbon steel. The mechanical properties of the welds obtained after welding are shown in Table 2 below.

[0067] The -40°C low-temperature longitudinal impact toughness test was carried out using a pendulum metal impact testing machine, and the tensile strength, yield strength and elongation tests were carried out using a tensile testing machine. Each weld was tested three times.

[0068] Table 2 Welding mechanical properties test

[0069]

[0070] As can be seen in Table 2, the mechanical properties of each example are relatively good, significantly improved compared to Comparative Example 1. This is because Examples 1-3 incorporate aluminum-magnesium alloy and yttrium powder. The aluminum-magnesium alloy has a low melting point and reacts with impurities in the weld to deoxidize, producing Al2O3 and MgO. MgO is an excellent slag-forming material that improves the impact toughness of the weld metal, while Al2O3 is a stable amphoteric oxide that improves the oxidation resistance of the weld surface. The addition of the aluminum-magnesium alloy not only purifies the weld but also generates an appropriate amount of slag-forming agents, Al2O3 and MgO. Yttrium, a rare earth element, not only enhances the weld metal's resistance to thermal cracking and corrosion stability, but also improves its mechanical properties, particularly its low-temperature impact toughness.

[0071] Experimental Example 3

[0072] The welds obtained after welding using the fluxes described in the examples and comparative examples were immersed in a simulated seawater solution. The simulated seawater was formulated based on ASTM D1141−98 (2013) and had a measured pH of 8.1. The degradation of the mechanical properties of the welds in the seawater corrosive environment was investigated.

[0073] The welds obtained in the embodiment and the comparative example were immersed in a simulated seawater solution for 7 days, 15 days, and 30 days, respectively, and then subjected to a -40°C low-temperature longitudinal impact toughness test and tensile strength, yield strength, and elongation tests. The obtained mechanical property data are shown in Table 3 below.

[0074] Table 3 Mechanical properties test of welds after seawater immersion

[0075]

[0076] Table 3 shows that the welds in the experimental examples maintained good mechanical properties after being immersed in seawater solution, while the mechanical properties of the comparative examples were poor, failing to resist seawater erosion. This is due to the addition of yttrium and aluminum-magnesium alloy in the experimental examples. Adding trace amounts of rare earth elements to aluminum-magnesium alloys can improve the alloy's structure, refine the grain size, and remove harmful impurities. This improves the strength and processability of aluminum-magnesium alloys, as well as their toughness and corrosion resistance.

[0077] The microstructure of the weld obtained after welding the flux obtained in Example 3 and Comparative Example 1 is as follows: Figure 3 and Figure 2 shown.

[0078] from Figure 2 and Figure 3 It can be seen that the weld structure after welding shows the presence of interlaced acicular ferrite within the grains, with inclusions as the nucleation core, which can effectively improve the low-temperature impact toughness of the weld.

[0079] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A composite flux, characterized in that: It is composed of the following components in mass percentage: SiO2 16%~19%, TiO2 7%~9%, CaO 18%~20%, MnO 15%~18%, CaF2 22%~25%, Y 0.4%~0.6% and Al-Mg alloy 13%~17%.

2. The composite flux according to claim 1, characterized in that The slag removal rate of the composite flux weld is ≥94%.

3. The composite flux according to claim 1, characterized in that: The impact toughness of the weld using the composite flux in a simulated seawater extreme environment at -40°C for 30 days is ≥98J; The tensile strength of the weld using the composite flux in a simulated seawater extreme environment for 30 days is ≥645 MPa; The yield strength of the weld using the composite flux in a simulated seawater extreme environment for 30 days is ≥533 MPa; The elongation of the weld using the composite flux in a simulated seawater extreme environment for 30 days is ≥29%.

4. A method for preparing the composite flux according to claim 1 to 3, characterized in that: The steps include: S1. Weigh SiO2, TiO2, CaO, MnO, CaF2, Y, and Al-Mg alloy according to the mass ratio and put them into a mixer. Add sodium water glass and mix at 15-20 r / min for 15-20 minutes. S2, the wet mixed material is granulated into balls by a disc, and the balls are put into a dryer for drying; S3, passing the dried flux particles through a 10-60 mesh sieve to obtain a semi-finished flux; S4. Put the semi-finished flux into a muffle furnace for sintering to obtain a finished flux.

5. The method for preparing a composite flux according to claim 4, wherein: In step S2, the pelletized material is dried at 200-250° C. for 30-60 minutes.

6. The method for preparing a composite flux according to claim 4, wherein: In step S4, the semi-finished flux is sintered at 700-800° C. for 2-3 hours.

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