An acidic flux-cored wire for welding of X80 pipeline steel

Abstract

This invention provides an acidic flux-cored welding wire for welding X80 pipeline steel, comprising a flux core and an outer sheath. The outer sheath is a low-carbon steel strip. The flux core, by weight percentage, comprises 24.0-27.0% rutile, 2.0-4.0% high-potassium feldspar, 3.0-6.0% quartz powder, 4.0-7.0% ferrosilicon powder, 2-3% composite fluoride, 1.0-4.0% potassium-sodium arc stabilizer, 9.0-13.0% nickel powder, 2.0-5.0% electrolytic manganese, 34.0-40.0% iron powder, 1.0-3.0% rare earth ferrosilicon, 1.0-2.0% aluminum powder, and 1.0-2.0% magnesium powder. The composite fluoride includes sodium fluoride, potassium fluoride, and rare earth fluorides, and the potassium-sodium arc stabilizer includes potassium titanate and sodium potassium titanate. This welding wire uses trace amounts of rare earth elements to toughen the weld, resulting in excellent low-temperature toughness and crack resistance, and enabling the weld's CTOD performance to meet standard requirements.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, and in particular to an acidic flux-cored welding wire for welding X80 pipeline steel. Background Technology

[0002] With the establishment of the national pipeline network, energy-related oil and gas pipelines will be laid out in a five-horizontal and five-vertical pattern. The main pipeline lines will mostly use X80 grade pipeline steel. The main pipeline welding will basically use a fully automatic welding method with double welding torches and solid welding wire. However, some mountainous areas and special working conditions require the use of flux-cored welding wire. The mechanical properties of X80 pipeline steel welds must meet the CTOD performance index. Summary of the Invention

[0003] In view of this, the present invention aims to provide an acidic flux-cored welding wire for welding X80 pipeline steel to solve the above problems.

[0004] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0005] An acidic flux-cored welding wire for welding X80 pipeline steel includes a flux core and an outer sheath. The outer sheath is a low-carbon steel strip. The flux core comprises, by weight percentage: 24.0-27.0% rutile, 2.0-4.0% high-potassium feldspar, 3.0-6.0% quartz powder, 4.0-7.0% ferrosilicon alloy powder, 2-3% composite fluoride, 1.0-4.0% potassium-sodium arc stabilizer, 9.0-13.0% nickel powder, 2.0-5.0% electrolytic manganese, 34.0-40.0% iron powder, 1.0-3.0% rare earth ferrosilicon, 1.0-2.0% aluminum powder, and 1.0-2.0% magnesium powder. The composite fluoride includes sodium fluoride, potassium fluoride, and rare earth fluorides. The potassium-sodium arc stabilizer includes potassium titanate and sodium potassium titanate.

[0006] Furthermore, the complex fluoride comprises, by weight percentage, 26-30% sodium fluoride, 13-18% potassium fluoride, and 54-61% rare earth fluorides.

[0007] Furthermore, rare earth fluorides are fluorides of rare earth elements lanthanum or cerium.

[0008] Furthermore, the potassium-sodium arc stabilizer comprises 46-53% potassium titanate and 47-54% sodium potassium titanate by weight percentage.

[0009] Furthermore, the flux core accounts for 16-18% of the total weight of the welding wire.

[0010] Furthermore, the chemical composition of the low-carbon steel strip, by weight percentage, is: C≤0.03%, Mn≤0.50%, Si≤0.20%, S≤0.030%, P≤0.030%, with the balance being Fe and unavoidable impurities.

[0011] Furthermore, the diameter of the welding wire is 1.16–1.21 mm.

[0012] Furthermore, the chemical composition of the deposited metal of the welding wire, by weight percentage, is: C≤0.15%, S≤0.03%, Mn: 0.50%~1.75%, Si≤0.8%, P≤0.03%, Cr≤0.15%, Ni: 1.0%~2.0%, Mo≤0.35%, V≤0.05%, with the balance being Fe and unavoidable impurities.

[0013] The addition of rutile primarily functions as a slag-forming agent, while also providing excellent arc stabilization. In this invention, the rutile used contains ≥95% TiO2. Rutile serves as the source of TiO2, and rutile-type titanium dioxide has a melting point of 1850℃, making it a typical short slag material, which enables the welding wire to achieve excellent all-position welding performance.

[0014] The addition of high-potassium feldspar mainly serves to appropriately increase the viscosity of the slag, improve the solidification rate of the welding slag, enhance the processability of vertical welding, and ensure weld formation; at the same time, the potassium element can stabilize the electric arc.

[0015] The addition of quartz powder, whose main component is SiO2, mainly functions as a slag-forming agent. It can appropriately increase the total amount of welding slag, making it evenly covered, while ensuring the formation of the weld.

[0016] The addition of silicon-manganese alloy mainly serves to improve weld strength. At the same time, manganese and silicon can play a joint deoxidizing role during the arc reaction, ensuring the purity of the weld structure.

[0017] During welding, composite fluorides can reduce the diffusible hydrogen content in the weld metal by combining with hydrogen, effectively improving the mechanical properties of the weld metal. The addition of rare earth elements in composite fluorides can refine the grains, ensuring the mechanical properties of the weld metal. Sodium and potassium elements in composite fluorides can stabilize the electric arc and improve welding process performance.

[0018] The addition of potassium-sodium arc stabilizers mainly improves slag viscosity, stabilizes the arc, optimizes weld formation, and improves weld slag removal performance.

[0019] Nickel powder, as a major austenitizing element, can improve corrosion resistance, increase strength, and refine grain size.

[0020] Electrolytic manganese, as a post-treatment deoxidizer and alloying element, is an austenite-forming element that can improve the tensile strength and toughness of weld metal and refine grain size. Manganese also enhances the overall strength of the weld matrix during solid solution treatment, exhibiting solid solution strengthening properties.

[0021] Iron powder serves as a supplementary component to ensure the correct ratio of the flux core powder, while also acting as a transition element into the weld.

[0022] Rare earth ferrosilicon, as a rare earth element additive, can improve the mechanical properties of welded metal, significantly improve crack resistance, and refine grain size.

[0023] Aluminum powder is a strong deoxidizer that can improve the droplet transfer process.

[0024] Magnesium powder is a strong deoxidizer that can improve the droplet transition process.

[0025] Compared with existing technologies, the acidic flux-cored welding wire for welding X80 pipeline steel described in this invention has the following advantages:

[0026] Compared to traditional flux-cored welding wires, the acidic flux-cored welding wire described in this invention for welding X80 pipeline steel offers a more stable welding process and can be used with fully automated welding equipment to achieve efficient welding of pipeline steel ring welds. Due to the addition of fluorides, the diffusible hydrogen content in the weld is extremely low, which can appropriately improve weld performance. The use of trace rare earth elements for weld toughening treatment results in excellent low-temperature toughness and crack resistance, ensuring that the weld's CTOD performance meets standard requirements. Furthermore, this flux-cored welding wire formulation uses common low-carbon steel strip as the main raw material, eliminating the need for other types of steel strips with high alloy element content, making production easy and resulting in a high-efficiency, easy-to-use welding material. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0028] 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.

[0029] The outer sheaths used in the following examples are from the same batch of steel strips and have the same composition. The measured values ​​of the steel strip composition are shown in Table 1.

[0030] Table 1. Steel Strip Composition Table

[0031] 0.025 0.006 0.31 0.08 0.009

[0032] The properties of the deposited metal of the flux-cored welding wire meet the requirements of the national standard GB / T 36233-2018. The specific mechanical properties of the deposited metal are shown in Table 2 below.

[0033] Table 2 Mechanical properties of deposited metal

[0034]

[0035] The mechanical performance requirements for CTOD of the mating joint are shown in Table 3 below (protective gas mixture).

[0036] Table 3. CTOD Mechanical Properties of Butt Joints

[0037] -10 ≥0.254

[0038] Example 1

[0039] An acidic flux-cored welding wire for welding X80 pipeline steel, with a wire diameter of 1.17 mm, comprises a flux core and an outer sheath. The flux core, by weight percentage, comprises 25.4% rutile, 3.1% high-potassium feldspar, 4.2% quartz powder, 5.0% silicon-manganese alloy, 2.4% composite fluoride, 1.5% potassium-sodium arc stabilizer, 12% nickel powder, 3.8% electrolytic manganese, 37.8% iron powder, 1.8% rare earth ferrosilicon, 1.5% aluminum powder, and 1.5% magnesium powder.

[0040] The complex fluoride comprises, by weight percentage, 29% sodium fluoride, 15% potassium fluoride, and 56% rare earth fluorides. The rare earth fluorides are fluorides of the rare earth element lanthanum.

[0041] The potassium-sodium arc stabilizer consists of potassium titanate and sodium potassium titanate in a 1:1 mass ratio.

[0042] The flux core accounts for 16% of the total weight of the welding wire.

[0043] Example 2

[0044] An acidic flux-cored welding wire for welding X80 pipeline steel, with a wire diameter of 1.18 mm, comprises a flux core and an outer sheath. The flux core, by weight percentage, comprises 26% rutile, 2.5% high-potassium feldspar, 5% quartz powder, 5.5% silicon-manganese alloy, 2.8% composite fluoride, 2% potassium-sodium arc stabilizer, 11% nickel powder, 2.6% electrolytic manganese, 37.1% iron powder, 2.5% rare earth ferrosilicon, 1.8% aluminum powder, and 1.2% magnesium powder.

[0045] The complex fluoride comprises, by weight percentage, 29% sodium fluoride, 14% potassium fluoride, and 57% rare earth fluorides. The rare earth fluorides are fluorides of the rare earth element cerium.

[0046] The potassium-sodium arc stabilizer comprises 49% potassium titanate and 51% sodium potassium titanate by weight percentage.

[0047] The flux core accounts for 17% of the total weight of the welding wire.

[0048] Example 3

[0049] An acidic flux-cored welding wire for welding X80 pipeline steel, with a wire diameter of 1.17 mm, comprises a flux core and an outer sheath. The flux core, by weight percentage, comprises 24.9% rutile, 3.4% high-potassium feldspar, 4.5% quartz powder, 5.8% silicon-manganese alloy, 2.5% composite fluoride, 2.3% potassium-sodium arc stabilizer, 11.5% nickel powder, 3.5% electrolytic manganese, 36.4% iron powder, 2.2% rare earth ferrosilicon, 1.4% aluminum powder, and 1.6% magnesium powder.

[0050] The complex fluoride comprises, by weight percentage, 28% sodium fluoride, 16% potassium fluoride, and 56% rare earth fluorides. The rare earth fluorides are fluorides of the rare earth element lanthanum.

[0051] The potassium-sodium arc stabilizer comprises 52% potassium titanate and 48% sodium potassium titanate by weight percentage.

[0052] The flux core accounts for 16% of the total weight of the welding wire.

[0053] Table 4 Chemical composition of flux-cored wire deposited metal in Examples 1-3

[0054]

[0055]

[0056] Table 5 Mechanical properties of flux-cored wire deposited metals in Examples 1-3

[0057]

[0058] Table 6. CTOD Mechanical Properties of Flux-Cored Welded Wire Butt Joints in Examples 1-3

[0059] Example 1 -10 0.352 Example 2 -10 0.338 Example 3 -10 0.341

[0060] Comparative Example 1

[0061] The difference from Example 1 is that no complex fluoride was added. The CTOD performance data was lower and did not meet the requirements.

[0062] Comparative Example 2

[0063] The difference from Example 1 is that no rare earth fluorides were added to the fluoride. The CTOD performance data was lower and did not meet the requirements.

[0064] Comparative Example 3

[0065] The difference from Example 1 is that the fluoride contains 41% sodium fluoride, 31% potassium fluoride, and 28% rare earth fluoride (not within the specified range), resulting in lower CTOD performance data that does not meet the requirements.

[0066] Comparative Example 4

[0067] The difference from Example 1 is that the ratio of potassium titanate to sodium titanate in the potassium-sodium arc stabilizer is 40:60 (not within the specified range). The CTOD performance data meets the index requirements, but the data is relatively low, and the arc stability during the welding process is poor.

[0068] Table 7 Comparative Examples 1-3: CTOD Mechanical Properties of Butt Joints with Flux-Cored Welding Wires

[0069] Comparative Example 1 -10 0.128 Comparative Example 2 -10 0.184 Comparative Example 3 -10 0.159 Comparative Example 4 -10 0.316

[0070] The above description is only a partial comparative example and preferred embodiment of the present invention, and is not intended to limit the present invention. 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. An acidic flux-cored welding wire for welding X80 pipeline steel, characterized in that: It includes a core and an outer sheath. The outer sheath is a low-carbon steel strip. The core, by weight percentage, includes 24.0-27.0% rutile, 2.0-4.0% high-potassium feldspar, 3.0-6.0% quartz powder, 4.0-7.0% ferrosilicon powder, 2-3% composite fluoride, 1.0-4.0% potassium-sodium arc stabilizer, 9.0-13.0% nickel powder, 2.0-5.0% electrolytic manganese, 34.0-40.0% iron powder, 1.0-3.0% rare earth ferrosilicon, 1.0-2.0% aluminum powder, and 1.0-2.0% magnesium powder. The composite fluoride includes sodium fluoride, potassium fluoride, and rare earth fluorides. The potassium-sodium arc stabilizer includes potassium titanate and sodium potassium titanate. The complex fluoride contains, by weight percentage, 26-30% sodium fluoride, 13-18% potassium fluoride, and 54-61% rare earth fluorides.

2. The acidic flux-cored welding wire for welding X80 pipeline steel according to claim 1, characterized in that: Rare earth fluorides are fluorides of rare earth elements lanthanum or cerium.

3. The acidic flux-cored welding wire for welding X80 pipeline steel according to claim 1, characterized in that: The potassium-sodium arc stabilizer contains 46-53% potassium titanate and 47-54% sodium potassium titanate by weight percentage.

4. The acidic flux-cored welding wire for welding X80 pipeline steel according to claim 1, characterized in that: The flux core accounts for 16-18% of the total weight of the welding wire.

5. The acidic flux-cored welding wire for welding X80 pipeline steel according to claim 1, characterized in that: The chemical composition of low carbon steel strip, by weight percentage, is: C≤0.03%, Mn≤0.50%, Si≤0.20%, S≤0.030%, P≤0.030%, with the balance being Fe and unavoidable impurities.

6. The acidic flux-cored welding wire for welding X80 pipeline steel according to claim 1, characterized in that: The diameter of the welding wire is 1.16~1.21mm.

7. The acidic flux-cored welding wire for welding X80 pipeline steel according to claim 1, characterized in that: The chemical composition of the deposited metal of the welding wire, by weight percentage, is: C≤0.15%, S≤0.03%, Mn: 0.50%~1.75%, Si≤0.8%, P≤0.03%, Cr≤0.15%, Ni: 1.0%~2.0%, Mo≤0.35%, V≤0.05%, with the balance being Fe and unavoidable impurities.

Images