Flux-cored wire with low diffusible hydrogen content in deposited metal

Abstract

The invention belongs to the technical field of welding, and particularly relates to a flux-cored wire with low diffusible hydrogen content in deposited metal, the flux-cored wire comprises an outer skin and a flux core, and the outer skin is prepared from a low-carbon steel strip; the flux core comprises, by mass, 2%-4% of zinc bromide powder, 18%-23% of calcium fluoride powder, 2.5%-4.5% of magnesium oxide powder, 6%-8% of nanometer titania powder, 2%-3.5% of RESiFe-41Ce rare earth ferrosilicon alloy powder, 6%-8% of nickel powder, 5%-8% of ferrotitanium powder, 6%-10% of calcium carbonate powder, 4%-8% of low-carbon ferromanganese powder and the balance reduced iron powder. The mass of the flux core accounts for 28-35% of the total mass of the flux-cored wire; the diameter of the flux-cored wire ranges from 1.5 mm to 6.0 mm. During welding, zinc bromide is added into the welding wire, so that the dehydrogenation efficiency of a molten pool is effectively improved, the diffusible hydrogen content in deposited metal is reduced, and the impact absorption energy of a welding seam is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of welding materials, and specifically relates to a flux-cored wire with a low diffusible hydrogen content in the deposited metal. Background Art

[0002] In high-end manufacturing fields such as pressure vessels, ships, bridges, and aircraft, extremely strict requirements are imposed on welding quality. Such equipment often needs to serve for a long time under harsh working conditions. Controlling the diffusible hydrogen content in the deposited metal at a low level (generally required to be below 1.5 ml / 100g) is a key factor to ensure the safe operation of the equipment.

[0003] In order to reduce the diffusible hydrogen content in the deposited metal, the traditional technique usually involves adding calcium fluoride to the flux powder of the flux-cored wire. During the welding process, calcium fluoride ionizes to produce fluoride ions, and these fluoride ions can chemically react with hydrogen ions in the deposited metal to form hydrogen fluoride. Since the boiling point of hydrogen fluoride is about 19.5°C, in the high-temperature welding environment, hydrogen fluoride is extremely likely to volatilize from the molten pool under the drive of thermodynamics, thereby effectively reducing the diffusible hydrogen content in the deposited metal (the diffusible hydrogen content measured by the glycerol method in Appendix B of GB / T 3965 is 3.0 - 5.0 ml / 100g), and further improving the mechanical properties of the welded joint, especially significantly enhancing the impact energy absorption value and strengthening the impact resistance of the welded part.

[0004] However, the above-mentioned flux-cored wire still has obvious limitations in controlling the diffusible hydrogen content in the deposited metal. Although the flux powder contains a sufficient amount of fluoride ions, which can theoretically combine with hydrogen ions fully, in the actual welding process, the welding arc is a moving heat source, resulting in an extremely short existence time of the molten pool (liquid state). During the short liquid existence period, the reaction between fluoride ions and hydrogen ions is difficult to proceed fully. Before the reaction is complete, the molten pool quickly solidifies into a solid weld, causing the dehydrogenation process to be unable to be completed thoroughly. This makes the diffusible hydrogen content in the deposited metal still not significantly reduced (the diffusible hydrogen content measured by the glycerol method in Appendix B of GB / T 3965 is above 3.0 ml / 100g), affecting the performance of workpieces with special requirements for impact performance and reducing the reliability of engineering structures. Summary of the Invention

[0005] The present invention provides a flux-cored wire with a low diffusible hydrogen content in the deposited metal, and solves the following technical problem: how to effectively improve the combination rate of fluoride ions and hydrogen ions in the molten pool during welding, so that more hydrogen ions can escape from the molten pool in the form of hydrogen fluoride within the short existence time of the molten pool, thereby effectively reducing the diffusible hydrogen content in the deposited metal.

[0006] The present invention adopts the following technical scheme: a flux-cored wire with a low diffusible hydrogen content in the deposited metal, comprising an outer skin and a flux core, wherein the outer skin is prepared from a low-carbon steel strip; The composition and mass fraction of the flux-cored are as follows: zinc bromide powder 2%-4%, calcium fluoride powder 18%-23%, magnesium oxide powder 2.5%-4.5%, nano titanium dioxide powder 6%-8%, rare earth ferrosilicon alloy powder 2%-3.5%, nickel powder 6%-8%, ferrotitanium powder 5%-8%, calcium carbonate powder 6%-10%, low-carbon ferromanganese powder 4%-8%, and the balance is reduced iron powder.

[0007] Preferably, the grade of the rare earth ferrosilicon alloy powder is RESiFe-41Ce, and its technical requirements comply with the relevant provisions of GB / T 4137-2015.

[0008] The particle size of the nano titanium dioxide powder is 50nm-100nm.

[0009] The particle sizes of the zinc bromide powder, calcium fluoride powder, magnesium oxide powder, rare earth ferrosilicon alloy powder, nickel powder, ferrotitanium powder, calcium carbonate powder, low-carbon ferromanganese powder, and reduced iron powder are 100 mesh - 200 mesh.

[0010] The thickness of the low-carbon steel strip is 0.5mm - 1.5mm; Preferably, the low-carbon steel strip is a cold-rolled low-carbon steel strip, and its technical requirements comply with the relevant provisions of YB / T 5059-2013.

[0011] The mass of the flux-cored accounts for 28%-35% of the total mass of the flux-cored wire.

[0012] The diameter of the flux-cored wire is 1.5mm - 6.0mm.

[0013] Under the high-temperature conditions of welding in the present invention, zinc bromide ionizes into zinc ions and bromide ions, and calcium fluoride ionizes into calcium ions and fluoride ions. Among them, the zinc ions, bromide ions, and fluoride ions form an ionic system with the hydrogen ions in the molten pool. Fluoride ions and bromide ions act as basic centers, zinc ions are typical Lewis acid centers, and hydrogen ions are Bronsted acid centers. Zinc ions interact with fluoride ions to form stable ion pairs; at the same time, bromide ions also interact with hydrogen ions to form ion pairs. The formation of these two types of ion pairs greatly changes the existence state and distribution pattern of various ions in the molten pool. Bromide ions and fluoride ions will form a certain ionic atmosphere in the molten pool, and there is an electrostatic interaction between them, thereby enhancing the activity of fluoride ions (the electric field of bromide ions will exert a "pulling" effect on the electron cloud of fluoride ions, causing the electron cloud distribution of fluoride ions to change and the electron cloud to become more loose. This change in the electron cloud state means that the binding force of fluoride ions to outer electrons is weakened, making fluoride ions more likely to participate in chemical reactions, thereby enhancing the activity of fluoride ions), making it easier to react with hydrogen ions.

[0014] From the perspective of ionic radius, the radius of bromide ion is about 195 pm, while that of fluoride ion is about 133 pm. When bromide ions are incorporated into the system, due to their larger radius, they will occupy more space, directly leading to significant changes in the interaction and arrangement of ions in the molten pool, and then changing the chemical environment of the surrounding ions. According to the principle of chemical equilibrium shift, the change in the above ionic environment increases the collision frequency between fluoride ions and hydrogen ions, significantly increasing the probability of their effective collision, thus accelerating the reaction rate of forming hydrogen fluoride. From the perspective of ionic polarization, bromide ions have a relatively large radius and relatively large deformability. Its existence will have a certain polarization effect on fluoride ions, making the electron cloud of fluoride ions more loose and easier to combine with hydrogen ions.

[0015] Analyzing from the hardness and softness of acids and bases, fluoride ions belong to hard bases and hydrogen ions belong to hard acids. According to the hard and soft acid-base theory, the combination between hard acids and hard bases is more stable and easier to occur. Therefore, compared with the combination of fluoride ions and zinc ions, the tendency of fluoride ions to combine with hydrogen ions is stronger, and it is easier to form HF. Also, because the boiling point of HF is lower than that of HBr, in a high-temperature environment, the system will preferentially generate HF gas and make it escape from the system, ultimately achieving the effect of accelerating the dehydrogenation process.

[0016] On the other hand, the bromide ions generated by the decomposition of zinc bromide can further react with hydrogen ions to form hydrogen bromide, promoting the consumption of hydrogen atoms, shifting the dehydrogenation reaction equilibrium of the molten pool to the positive reaction direction, thereby improving the dehydrogenation efficiency of calcium fluoride and indirectly increasing the overall dehydrogenation rate.

[0017] When the addition amount of zinc bromide is relatively low (less than 2%), fewer ions are generated in the system, and the synergistic effect with other ions is limited. Although it increases the collision frequency between hydrogen ions and fluoride ions to a certain extent, the effect is not obvious, and the increase in dehydrogenation rate is small. At this time, the change degree of the ionic activity coefficient is also weak, and the reduction effect on the reaction activation energy is not significant.

[0018] As the addition amount of zinc bromide gradually increases (close to 3%), more ions enter the molten pool system, and the synergistic effect with other ions is significantly enhanced, greatly increasing the collision frequency between hydrogen ions and fluoride ions, and the dehydrogenation rate is significantly accelerated. At the same time, the change in the ionic activity coefficient is more obvious, further reducing the activation energy of the reaction of hydrogen ions and fluoride ions to combine, and promoting the dehydrogenation reaction powerfully from both kinetic and thermodynamic perspectives.

[0019] When the addition amount of zinc bromide is too high (greater than 4%), too many ions will make the ionic environment of the slag system too complex. Although the ionic activity coefficient continues to change, it will cause fluoride ions to combine with other cations in the molten pool to form some compounds that are not conducive to the dehydrogenation reaction, thus affecting the further increase in the dehydrogenation rate.

[0020] In the present invention, zinc bromide is added to the flux cored powder, which synergistically acts with calcium fluoride, greatly improving the combination rate of hydrogen ions and fluoride ions in the welding molten pool. During the short residence time of the molten pool, the combination efficiency of fluoride ions and hydrogen ions is effectively improved, enabling them to quickly escape from the molten pool, significantly reducing the diffusible hydrogen content in the deposited metal (the diffusible hydrogen content measured by the flux cored wire of the present invention is 0.8 ml / 100 g, far less than the diffusible hydrogen content value of 3.0 ml / 100 g of conventional low-hydrogen type welding wires), and improving the impact absorption energy value of the welded joint. When using the flux cored wire of the present invention to weld Q345R steel, the impact absorption energy of its welded joint is above 80 J, which is 2.2 times that of the welded joint of the flux cored wire without the addition of zinc bromide, effectively ensuring the service performance of the workpiece. Detailed implementation mode

[0021] The principles and features of the present invention will be described below in conjunction with examples and comparative examples. The listed examples and comparative examples are only used to explain the present invention and do not limit the scope of the present invention.

[0022] Example 1:

[0023] A flux cored wire with low diffusible hydrogen content in the deposited metal, including an outer skin and a flux core. The outer skin is prepared from low-carbon steel strip; the components and mass fractions of the flux core are: zinc bromide powder 2%, calcium fluoride powder 18%, magnesium oxide powder 2.5%, nano-titanium dioxide powder 6%, rare earth ferrosilicon alloy powder 2%, nickel powder 6%, ferrotitanium powder 5%, calcium carbonate powder 6%, low-carbon ferromanganese powder 4%, and the balance is reduced iron powder.

[0024] The grade of the rare earth ferrosilicon alloy powder is RESiFe-41Ce, and its technical requirements comply with the relevant regulations of GB / T 4137-2015.

[0025] The particle size of the nano-titanium dioxide powder is 50 nm - 100 nm.

[0026] The particle sizes of the zinc bromide powder, calcium fluoride powder, magnesium oxide powder, rare earth ferrosilicon alloy powder, nickel powder, ferrotitanium powder, calcium carbonate powder, low-carbon ferromanganese powder, and reduced iron powder are 100 mesh - 200 mesh.

[0027] The thickness of the low-carbon steel strip is 0.5 mm; the low-carbon steel strip is cold-rolled low-carbon steel strip, and its technical requirements comply with the relevant regulations of YB / T 5059-2013.

[0028] The mass of the flux core accounts for 28% of the total mass of the flux cored wire.

[0029] The diameter of the flux cored wire is 1.5 mm.

[0030] Example 2:

[0031] A flux-cored wire with low diffusible hydrogen content in the deposited metal, comprising an outer skin and a flux core. The outer skin is made of low-carbon steel strip; the components and mass fractions of the flux core are as follows: zinc bromide powder 4%, calcium fluoride powder 23%, magnesium oxide powder 4.5%, nano-titanium dioxide powder 8%, rare earth ferrosilicon alloy powder 3.5%, nickel powder 8%, ferrotitanium powder 8%, calcium carbonate powder 10%, low-carbon ferromanganese powder 8%, and the balance is reduced iron powder.

[0032] The grade of the rare earth ferrosilicon alloy powder is RESiFe-41Ce, and its technical requirements comply with the relevant provisions of GB / T 4137-2015.

[0033] The particle size of the nano-titanium dioxide powder is 50nm - 100nm.

[0034] The particle sizes of the zinc bromide powder, calcium fluoride powder, magnesium oxide powder, rare earth ferrosilicon alloy powder, nickel powder, ferrotitanium powder, calcium carbonate powder, low-carbon ferromanganese powder, and reduced iron powder are 100 mesh - 200 mesh.

[0035] The thickness of the low-carbon steel strip is 1.5mm; the low-carbon steel strip is cold-rolled low-carbon steel strip, and its technical requirements comply with the relevant provisions of YB / T 5059-2013.

[0036] The mass of the flux core accounts for 35% of the total mass of the flux-cored wire.

[0037] The diameter of the flux-cored wire is 6.0mm.

[0038] Example 3:

[0039] A flux-cored wire with low diffusible hydrogen content in the deposited metal, comprising an outer skin and a flux core. The outer skin is made of low-carbon steel strip; the components and mass fractions of the flux core are as follows: zinc bromide powder 3%, calcium fluoride powder 20%, magnesium oxide powder 3.5%, nano-titanium dioxide powder 7%, rare earth ferrosilicon alloy powder 2.8%, nickel powder 7%, ferrotitanium powder 6.5%, calcium carbonate powder 8%, low-carbon ferromanganese powder 6%, and the balance is reduced iron powder.

[0040] The grade of the rare earth ferrosilicon alloy powder is RESiFe-41Ce, and its technical requirements comply with the relevant provisions of GB / T 4137-2015.

[0041] The particle size of the nano-titanium dioxide powder is 50nm - 100nm.

[0042] The particle sizes of the zinc bromide powder, calcium fluoride powder, magnesium oxide powder, rare earth ferrosilicon alloy powder, nickel powder, ferrotitanium powder, calcium carbonate powder, low-carbon ferromanganese powder, and reduced iron powder are 100 mesh - 200 mesh.

[0043] The thickness of the low-carbon steel strip is 1.0mm; the low-carbon steel strip is cold-rolled low-carbon steel strip, and its technical requirements comply with the relevant provisions of YB / T 5059-2013.

[0044] The mass of the flux core accounts for 31% of the total mass of the flux-cored wire.

[0045] The diameter of the flux-cored wire is 3.2 mm.

[0046] Comparative Example 1: It is basically the same as Example 3, except that there is no zinc bromide powder in the flux core.

[0047] Comparative Example 2: It is basically the same as Example 3, except that the content of zinc bromide powder in the flux core is 1.8%.

[0048] Comparative Example 3: It is basically the same as Example 3, except that the content of zinc bromide powder in the flux core is 4.2%.

[0049] Comparative Example 4: It is basically the same as Example 3, except that the nano-titanium dioxide powder in the flux core is replaced with titanium dioxide powder with a mesh size of 100 - 200 meshes.

[0050] For the flux-cored wires obtained from Examples 1 - 3 and Comparative Examples 1 - 4, the diffusible hydrogen content was measured by the glycerol method in Appendix B of GB / T 3965. After 5 experiments for each case, the average value of 5 results was taken, and the results are shown in Table 1.

[0051]

[0052] For the flux-cored wires obtained from Examples 1 - 3 and Comparative Examples 1 - 4, Q345R steel (the technical requirements conform to the provisions of GB19189, normalized state, thickness of 15 mm) was welded, and an impact test was carried out after welding. After 5 experiments for each case, the average value of 5 results was taken, and the results are shown in Table 2.

[0053]

[0054] Inspired by the ideal embodiments of the present invention as described above, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims. All equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A flux-cored welding wire with low diffusible hydrogen content in the deposited metal, comprising an outer sheath and a flux core, characterized in that: The outer skin is made of low-carbon steel strip; the composition and mass fraction of the core are: zinc bromide powder 2%-4%, calcium fluoride powder 18%-23%, magnesium oxide powder 2.5%-4.5%, nano titanium dioxide powder 6%-8%, rare earth ferrosilicon alloy powder 2%-3.5%, nickel powder 6%-8%, ferrotitanium powder 5%-8%, calcium carbonate powder 6%-10%, low-carbon ferromanganese powder 4%-8%, and the balance is reduced iron powder.

2. The flux-cored welding wire with low diffusible hydrogen content in the deposited metal according to claim 1, characterized in that: The grade of the rare earth ferrosilicon alloy powder is RESiFe-41Ce.

3. The flux-cored welding wire with low diffusible hydrogen content in the deposited metal according to claim 1, characterized in that: The particle size of the nano titanium dioxide powder is 50nm-100nm.

4. The flux-cored welding wire with low diffusible hydrogen content in the deposited metal according to claim 1, characterized in that: The particle sizes of the zinc bromide powder, calcium fluoride powder, magnesium oxide powder, rare earth ferrosilicon alloy powder, nickel powder, ferrotitanium powder, calcium carbonate powder, low carbon ferromanganese powder and reduced iron powder are 100-200 meshes.

5. The flux-cored welding wire with low diffusible hydrogen content in the deposited metal according to claim 1, characterized in that: The thickness of the low carbon steel strip is 0.5 mm-1.5 mm.

6. The flux-cored welding wire with low diffusible hydrogen content in the deposited metal according to claim 1, characterized in that: The mass of the flux core accounts for 28%-35% of the total mass of the flux cored welding wire.

7. The flux-cored welding wire with low diffusible hydrogen content in the deposited metal according to claim 1, characterized in that: The diameter of the flux-cored welding wire is 1.5 mm-6.0 mm.

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