A flux-cored wire for a 43 kg grade weathering steel and application thereof

Abstract

This invention provides a 43 kg grade flux-cored welding wire for weathering steel, comprising a carbon steel outer sheath and a flux core filled within the carbon steel outer sheath. The flux core comprises the following components by mass percentage: rutile 42-50%, zircon sand 0.5-1.5%, wollastonite 4-7%, sodium fluoride 1.5-3%, 45# atomized ferrosilicon 0-5%, ferrosilicon-manganese alloy 0-11%, metallic manganese 0-5.5%, high-carbon ferromanganese 0-8%, graphite 0-0.25%, nickel powder 4-6.6%, metallic chromium 1.6-2.7%, copper powder 1.6-2.2%, ferrotitanium 3.5-7%, ferroboron 4-9%, with the balance being iron powder; wherein, at least one of 45# atomized ferrosilicon and ferrosilicon-manganese alloy is contained, at least one of ferrosilicon-manganese alloy, metallic manganese, and high-carbon ferromanganese is contained, and at least one of high-carbon ferromanganese and graphite is contained. This flux-cored welding wire is suitable for CO2 gas shielded welding. Its deposited metal has a tensile strength of 430-550 MPa, a low-temperature impact absorption energy of over 47 J at -20℃, and a weather resistance index I of over 6.5.

Description

Technical Field

[0001] This invention belongs to the field of welding materials technology, specifically relating to a 43 kg class flux-cored welding wire for weathering steel and its application. Background Technology

[0002] Weathering steel, due to its resistance to atmospheric corrosion, is increasingly being used in bridges, automobiles, railway vehicles, and other industries. It offers advantages such as reduced weight, lower maintenance costs, and improved construction efficiency. Currently, ordinary steel bridges primarily rely on painting to address rust, but painting costs and subsequent maintenance are high. Therefore, weathering steel for bridges has seen widespread development both domestically and internationally, and the development of matching welding materials is becoming increasingly urgent.

[0003] Currently, the market offers a limited variety of flux-cored welding wires for weathering steel, with unstable mechanical properties and inconsistent weathering resistance. According to AWS D1.5, the corrosion resistance index (I) of the weld metal must not be lower than 6.0, yet there is very little research on the weathering resistance of flux-cored welding wires specifically designed for weathering steel with a tensile strength of 43 kg. Summary of the Invention

[0004] The purpose of this invention is to provide a flux-cored welding wire for 43 kg class weathering steel, which can at least solve some of the defects existing in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A 43 kg grade flux-cored welding wire for weathering steel includes a carbon steel outer sheath and a flux core filled within the carbon steel outer sheath. The flux core comprises the following components by mass percentage: rutile 42-50%, zircon sand 0.5-1.5%, wollastonite 4-7%, sodium fluoride 1.5-3%, 45# atomized ferrosilicon 0-5%, ferrosilicon-manganese alloy 0-11%, metallic manganese 0-5.5%, high-carbon ferromanganese 0-8%, graphite 0-0.25%, nickel powder 4-6.6%, metallic chromium 1.6-2.7%, copper powder 1.6-2.2%, ferrotitanium 3.5-7%, ferroboron 4-9%, with the balance being iron powder. The wire contains at least one of 45# atomized ferrosilicon and ferrosilicon-manganese alloy, at least one of ferrosilicon-manganese alloy, metallic manganese, and high-carbon ferromanganese, and at least one of high-carbon ferromanganese and graphite.

[0007] Furthermore, the flux core accounts for 13.8 to 14.2% of the total mass of the flux-cored welding wire.

[0008] Furthermore, the silicon-manganese alloy is a 63-22 silicon-manganese alloy, with a silicon mass fraction of 22-25% and a manganese mass fraction of 63-70%.

[0009] Furthermore, the ferroboron is W100B ferroboron, wherein the mass fraction of boron is 1%.

[0010] Furthermore, the iron powder used is 270 iron powder.

[0011] Furthermore, the deposited metal of the aforementioned 43 kg class weathering steel flux-cored welding wire contains the following chemical composition by mass percentage: C ≤ 0.05%, Mn: 0.4~0.7%, Si ≤ 0.30%, S ≤ 0.015%, P ≤ 0.015%, Ni: 0.4~1.0%, Cr: 0.25~0.5%, Cu: 0.2~0.5%.

[0012] Specifically, the core comprises the following components by mass percentage: rutile 42%, zircon sand 1.5%, wollastonite 7%, sodium fluoride 1.5%, 45# atomized ferrosilicon 5%, metallic manganese 5.5%, graphite 0.25%, nickel powder 4%, metallic chromium 2.1%, copper powder 1.9%, ferrotitanium 7%, ferroboron 9%, with the balance being iron powder.

[0013] Specifically, the core comprises the following components by mass percentage: 45% rutile, 1% zircon sand, 4% wollastonite, 1.5% sodium fluoride, 45# atomized ferrosilicon, 8% high-carbon ferromanganese, 4.4% nickel powder, 1.6% metallic chromium, 1.6% copper powder, 5% ferrotitanium, 7% ferroboron, with the balance being iron powder.

[0014] Specifically, the core comprises the following components by mass percentage: 50% rutile, 0.5% zircon sand, 4% wollastonite, 3% sodium fluoride, 11% silicon manganese alloy, 5% high-carbon ferromanganese, 6.6% nickel powder, 2.7% metallic chromium, 2.2% copper powder, 3.5% ferrotitanium, 4% ferroboron, with the balance being iron powder.

[0015] The 43 kg class weathering steel flux-cored welding wire provided by this invention is used for CO2 gas shielded welding, connected to a DC reverse polarity power supply for welding operation, with a welding current of 220-250A and a welding voltage of 26-28V.

[0016] The design principle of the flux-cored welding wire for 43 kg-class weathering steel of the present invention is as follows:

[0017] Rutile: It adjusts the melting point and viscosity of slag, improves arc stability and weld formation. When its addition is less than 42%, the arc stability is poor, the slag production is insufficient, and the weld is not easy to remove slag. When the addition exceeds 50%, the gas in the molten pool is not easy to escape and porosity is generated. Therefore, in this invention, the addition of rutile is controlled to be 42-50%.

[0018] Zircon sand: An appropriate amount of zircon sand can improve the slag removal effect of the weld, making the weld surface clean and the edges neat. Generally, 0.5 to 1.5% is added.

[0019] Wollastonite: Wollastonite contains calcium oxide and silicon oxide. Silicon oxide can reduce the surface tension of molten iron in the molten pool, enhance the fluidity of molten iron, form slag, and improve the slag covering performance. Calcium oxide can increase the alkalinity of slag and improve impact toughness. When the amount of wollastonite added is less than 4%, the above effects are not obvious. However, when the amount of wollastonite added exceeds 7%, long slag is formed, the welding process is poor, and the slag is glassy, ​​which is not conducive to slag removal. Therefore, in this invention, the amount of wollastonite added is controlled to be 4-7%.

[0020] Sodium fluoride: a dehydrogenating agent and a thinner, reducing the diffusible hydrogen content in the weld. When its addition is less than 1.5%, its dehydrogenating ability is insufficient, and the weld is prone to porosity and pitting. It also has a certain arc stabilizing function. However, when the addition exceeds 3%, welding spatter and fumes increase, affecting the welding process performance.

[0021] Si: Si is an important deoxidizer. A certain amount of Si in the welding wire can reduce the oxygen content of the weld metal, improve the low-temperature impact toughness, and regulate the fluidity of molten iron. Si affects the weld strength. The tensile strength of the weld in this invention has certain requirements, and its content should be strictly controlled to ensure the achievement of the strength. If the Si content in the weld metal is too high, the strength will exceed the standard. At the same time, the Si content is related to the weather resistance index. If the Si content in the weld metal is too low, the weather resistance index of the weld will be low. In this invention, the Si content is added in the form of 45# atomized ferrosilicon or silicon-manganese alloy.

[0022] Mn: Mn is a deoxidizer that reduces the oxygen content of the weld metal and increases its strength and crack resistance. The tensile strength of the weld in this invention has certain requirements, and its content should be strictly controlled to ensure the achievement of the required strength. However, the beneficial effect of Mn on impact toughness will also weaken as the Mn content decreases, and the impact toughness may even fail to meet the standard requirements. Therefore, the Mn content should be controlled within a suitable range to control both strength and ensure low-temperature impact toughness. When the Mn content in the weld metal is low, it will lead to insufficient deoxidation, and the weld metal strength and low-temperature impact toughness will not meet the requirements. When the Mn content in the weld metal is too high, it will lead to excessively high weld strength. In this invention, the Mn content is added in the form of a combination of silicon-manganese alloy or high-carbon ferromanganese and metallic manganese.

[0023] In this invention, the silicon-manganese alloy used is 63-22 silicon-manganese alloy, wherein the mass fraction of silicon is 22-25% and the mass fraction of manganese is 63-70%.

[0024] C: C has a significant impact on strength and performance, and its content should be controlled. High C content in weld metal leads to excessive strength; low C content in weld metal results in unstable low-temperature impact toughness. In this invention, C is added in the form of graphite or high-carbon ferromanganese. Graphite has a low transition rate, while high-carbon ferromanganese has a high C transition rate, but both can achieve the required C content for the weld through content control.

[0025] Copper powder: Cu can improve the corrosion resistance of weathering steel. During the corrosion process, Cu enrichment occurs on the surface of weathering steel, forming a tight CuO interlayer between the corrosion layer and the Cu enrichment layer. This interlayer can slow down or prevent the corrosive medium from continuing to penetrate inward. Adding an appropriate amount of Cu to the weld can improve the weathering index of the weld. The effect of Cu content on the weathering index of the weld is not linear; there is a range. Too high or too low Cu content will cause the weathering index to fail to meet the standard. Therefore, the Cu content should be controlled within a suitable range to balance the effects of Cu on impact toughness and weathering index. In this invention, when the Cu addition is less than 1.6%, the above effect is not obvious, and the weathering index I is low. When the Cu addition exceeds 2.2%, the weathering index of the weld will also decrease. Therefore, this invention controls the copper powder content to be 1.6% to 2.2%.

[0026] Nickel powder: The strength requirement of this welding material is within a certain range. The C and Mn content in the weld should be controlled to ensure that the strength does not exceed the standard. However, low levels of the above two elements will lead to the precipitation of coarse proeutectoid ferrite, which will have an adverse effect on impact toughness. Therefore, the addition of Ni can improve the impact toughness of the weld and also improve the strength to a certain extent. From the perspective of weather resistance index, the weather resistance index and Ni content are not linearly related. There is a range. If the Ni content is too high or too low, the weather resistance index will not meet the standard. In this invention, when the amount of nickel powder added is less than 4%, the impact toughness and weather resistance index I of the weld are low. When the nickel powder content exceeds 6.6%, it will cause resource waste and increase the cost of welding wire.

[0027] Metallic chromium: Cr is a common alloying element in weathering steel. Cr can form a dense oxide film on the steel surface, increase the electrode potential, produce a passivation effect, and improve the corrosion resistance of the steel. The effect is particularly obvious when it is added to the steel at the same time as Cu. When the amount of Cr added is too low, the weathering index I is too low. When the amount of Cr added is too high, it will increase the weld strength and exceed the standard range requirements. Therefore, in this invention, the amount of Cr added is controlled to be 1.6 to 2.7%.

[0028] Titanium iron: As a deoxidizer, it can transfer a small amount of Ti element into the weld. Adding too much will result in excessively high strength; adding too little will result in poor deoxidation effect and be detrimental to weld toughness. In this invention, the amount of titanium iron added is controlled to be 3.5-7%.

[0029] Ferroboron: A small amount of boron (B) is introduced into the weld, which, in combination with Ti, promotes the formation of acicular ferrite and improves toughness. Improper addition can lead to a sharp decrease in toughness, especially excessive addition which increases crack susceptibility. In this invention, the amount of ferroboron added is controlled to be 4–9%. Preferably, W100B ferroboron is used, wherein the mass fraction of boron is 1%.

[0030] In addition, the filling rate of the flux core in this invention should be controlled between 13.8% and 14.2%. When the filling rate of the flux core is less than 13.8%, the amount of slag is very small, and the slag covering the weld is thin, which makes it difficult to remove the slag. When the filling rate of the flux core is higher than 14.2%, the alloy content in the weld will be high and the weld strength will exceed the standard.

[0031] The beneficial effects of this invention are:

[0032] (1) The 43 kg grade weathering steel flux-cored welding wire provided by the present invention transfers appropriate amounts of Ni, Cr, Cu and Si elements to the weld metal through the flux core, so that the weld metal has excellent weather resistance and its weather resistance index I can be greater than 6.5.

[0033] (2) The 43 kg grade weathering steel flux-cored welding wire provided by the present invention controls the content of C, Mn, Si and other alloying elements in the weld metal by adjusting the flux composition, ensuring that the tensile strength of the weld metal is 430-550 MPa and the low-temperature impact absorption energy at -20℃ is greater than 47 J, and has stable mechanical properties.

[0034] (3) The 43 kg class weathering steel flux-cored welding wire provided by the present invention can be used for all-position welding, with excellent welding process performance and beautiful weld formation. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The 43 kg class weathering steel flux-cored welding wire in the embodiments consists of a carbon steel outer sheath and a flux core filled within the carbon steel outer sheath. The composition of the flux core in the corresponding embodiments is shown in Table 1. The flux core accounts for 14% of the total mass of the flux-cored welding wire. In each embodiment of the present invention, the silicon-manganese alloy used is 63-22 silicon-manganese alloy, the ferroboron is W100B ferroboron, and the iron powder has a loose bulk density of 2.70 g / cm³. 3 The 270 iron powder; the specific manufacturing process of the flux-cored welding wire is existing technology and will not be described in detail here.

[0037] Table 1: Composition of the drug cores in each example (mass percentage, %)

[0038]

[0039] The physicochemical properties of the deposited metal of the flux-cored welding wires prepared using the flux-cored powders of Examples 1-3 were tested. The bevel, dimensions, sampling methods, and locations of the test plates were all in accordance with the Chinese National Standard GB / T 10045 "Fluid-cored Welding Wires for Non-alloy Steels and Fine-grained Steels". CO2 gas shielded welding was used, with a DC reverse polarity power supply. The welding current was 220-250A, and the welding voltage was 26-28V. The chemical composition, weathering index I, and mechanical properties of the deposited metal of the welding wires prepared in each example are shown in Tables 2 and 3. The weathering index I was calculated using the following formula, and its chemical composition is the chemical content of the deposited metal:

[0040] I=26.01(%Cu)+3.88(%Ni)+1.20(%Cr)+1.48(%Si)+17.28(%P)-7.29(%Cu)×(%Ni)-9.10(%Ni)×(%P)-33.39(%Cu) 2 .

[0041] Table 2: Chemical composition (mass percentage %) and weather resistance index I of the deposited metal

[0042]

[0043] Table 3: Mechanical Properties of Deposited Metal

[0044]

[0045] In summary, the 43 kg-grade weathering steel flux-cored welding wire provided by this invention transfers appropriate amounts of Ni, Cr, Cu, and Si elements to the weld metal through the flux core, giving the weld metal excellent weather resistance, with a weather resistance index I greater than 6.5. Simultaneously, by adjusting the flux core composition, the content of C, Mn, Si, and other alloying elements in the weld metal is controlled, ensuring a tensile strength of 430–550 MPa and a low-temperature impact absorption energy of greater than 47 J at -20℃, exhibiting stable mechanical properties.

[0046] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A flux-cored welding wire for 43 kg grade weathering steel, comprising a carbon steel outer sheath and a flux core filled within the carbon steel outer sheath, characterized in that, The core comprises the following components by mass percentage: rutile 42-50%, zircon sand 0.5-1.5%, wollastonite 4-7%, sodium fluoride 1.5-3%, 45# atomizing ferrosilicon 0-5%, silicon-manganese alloy 0-11%, metallic manganese 0-5.5%, high-carbon ferromanganese 0-8%, graphite 0-0.25%, nickel powder 4-6.6%, metallic chromium 1.6-2.7%, copper powder 1.6-2.2%, ferrotitanium 3.5-7%, ferroboron 4-9%, with the balance being iron powder; The flux-cored wire contains at least one of the following: 45# atomized ferrosilicon and ferrosilicon-manganese alloy; at least one of ferrosilicon-manganese alloy, metallic manganese, and high-carbon ferromanganese; and at least one of high-carbon ferromanganese and graphite. The flux-cored wire weld metal contains the following chemical composition by mass percentage: C≤0.05%, Mn: 0.4~0.7%, Si≤0.30%, S≤0.015%, P≤0.015%, Ni: 0.4~1.0%, Cr: 0.25~0.5%, Cu: 0.2~0.5%.

2. The 43 kg class weathering steel flux-cored welding wire as described in claim 1, characterized in that, The flux core accounts for 13.8 to 14.2% of the total mass of the flux-cored welding wire.

3. The 43 kg class weathering steel flux-cored welding wire as described in claim 1, characterized in that, The silicon-manganese alloy used is 63-22 silicon-manganese alloy, with a silicon mass fraction of 22-25% and a manganese mass fraction of 63-70%.

4. The 43 kg class weathering steel flux-cored welding wire as described in claim 1, characterized in that, The ferroboron used is W100B ferroboron, in which the mass fraction of boron is 1%.

5. The 43 kg class weathering steel flux-cored welding wire as described in claim 1, characterized in that, The iron powder used is 270 iron powder.

6. The 43 kg class weathering steel flux-cored welding wire as described in claim 1, characterized in that, The core comprises the following components by mass percentage: rutile 42%, zircon sand 1.5%, wollastonite 7%, sodium fluoride 1.5%, 45# atomized ferrosilicon 5%, metallic manganese 5.5%, graphite 0.25%, nickel powder 4%, metallic chromium 2.1%, copper powder 1.9%, ferrotitanium 7%, ferroboron 9%, with the balance being iron powder.

7. The 43 kg class weathering steel flux-cored welding wire as described in claim 1, characterized in that, The core comprises the following components by mass percentage: 45% rutile, 1% zircon sand, 4% wollastonite, 1.5% sodium fluoride, 45# atomized ferrosilicon, 8% high-carbon ferromanganese, 4.4% nickel powder, 1.6% metallic chromium, 1.6% copper powder, 5% ferrotitanium, 7% ferroboron, with the balance being iron powder.

8. The 43 kg class weathering steel flux-cored welding wire as described in claim 1, characterized in that, The core comprises the following components by mass percentage: 50% rutile, 0.5% zircon sand, 4% wollastonite, 3% sodium fluoride, 11% silicon manganese alloy, 5% high-carbon ferromanganese, 6.6% nickel powder, 2.7% metallic chromium, 2.2% copper powder, 3.5% ferrotitanium, 4% ferroboron, with the balance being iron powder.

9. The application of the 43 kg class flux-cored welding wire for weathering steel as described in any one of claims 1 to 8, characterized in that, CO2 gas shielded welding is used, and the welding operation is carried out by connecting a DC reverse polarity power supply. The welding current is 220-250A and the welding voltage is 26-28V.

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