A submerged arc welding wire for non-copper-plated x52 pipeline steel

Abstract

The present application relates to the technical field of submerged arc welding wire, in particular to a submerged arc welding wire without copper plating for X52 pipeline steel. The conventional submerged arc welding wire for X52 pipeline steel cannot take into account the mechanical properties and hydrogen embrittlement resistance of the obtained weld metal under the condition of large heat input welding. In view of the above technical problems, the present application provides a submerged arc welding wire without copper plating for X52 pipeline steel, which does not contain metal elements Al, Cr, Ce and Y in the chemical composition, and the chemical composition of the submerged arc welding wire further comprises, in addition to the basic elements C, Mn, Si, Cu, Mo and Fe, appropriate amounts of Ni, V, Ti, Nb and B elements, so that the obtained submerged arc welding wire not only has good mechanical properties, but also has excellent hydrogen resistance for the welded joint formed by welding X52 pipeline steel under the condition of large heat input welding.

Description

Technical Field

[0001] This invention relates to the field of submerged arc welding wire technology, specifically to a copper-free X52 pipeline steel submerged arc welding wire. Background Technology

[0002] Hydrogen pipelines are a key component of hydrogen energy infrastructure construction, and their safety and economy depend heavily on the performance of pipeline steel and its welded joints.

[0003] Currently, X52 grade low-alloy high-strength pipeline steel is widely used in long-distance natural gas pipelines due to its good comprehensive performance, and its application in medium- and low-pressure hydrogen pipelines is being gradually explored. Because hydrogen has damage mechanisms such as hydrogen-induced cracking (HIC) and stress-induced hydrogen cracking (SCC) on steel, the microstructure, mechanical properties, residual stress state, and resistance to hydrogen embrittlement in the welded joint area of ​​hydrogen pipelines have become key research areas in engineering applications.

[0004] Currently, submerged arc welding is the primary welding method for X52 pipeline steel, especially in the manufacturing of straight seam welded pipes, where high heat input welding is often employed to improve welding efficiency and penetration depth, meeting the demands of continuous industrial production. However, high heat input welding tends to result in coarse weld joint microstructure and a wide heat-affected zone, thus significantly impacting the joint's microstructure, alloy element distribution, and metallurgical reactions. The selection of welding wire and flux combinations is crucial in this process, directly affecting the overall performance of the weld joint. Existing welding wires are mainly carbon-manganese type wires containing Mn and Si, typically paired with neutral or weakly basic fluxes to balance good process adaptability and strength matching. However, under high heat input welding conditions, their improvement in microstructure refinement and resistance to hydrogen embrittlement remains significantly limited. Existing welding wires and fluxes are mostly designed for conventional pipeline steel, lacking design concepts for microcrack propagation and microstructure control in hydrogen environments. Current technologies cannot effectively improve stability and safety in hydrogen environments while ensuring mechanical properties such as tensile strength and impact toughness.

[0005] Furthermore, submerged arc welding wires often undergo copper plating to improve arc stability, conductivity, and oxidation resistance. However, the copper plating process itself is complex and carries a significant environmental burden, increasing manufacturing costs and emission risks. The copper layer can easily form inclusions in the weld, affecting the purity of the joint metal and reducing its operational safety in a hydrogen environment. Summary of the Invention

[0006] The existing technology has the problem that conventional submerged arc welding wire for X52 pipeline steel cannot simultaneously achieve the mechanical properties and hydrogen resistance of the weld metal under high heat input welding conditions. To address the above technical problems, this invention provides a copper-free submerged arc welding wire for X52 pipeline steel, whose chemical composition does not contain the metallic elements Al, Cr, Ce, and Y. The chemical composition of the submerged arc welding wire, by mass percentage, includes the following components:

[0007] C: 0.03-0.06%; Mn: 0.4-1.0%; Si: 0.10-0.50%; Cu: 0.2-0.25%; P≤0.010%;

[0008] S ≤ 0.005%; Ni: 0.50-1.5%; Mo: 0.10-0.50%; V ≤ 0.03% and not 0; Ti: 0.05-0.15%; Nb ≤ 0.15% and not 0; B: 0.001-0.008%; balance Fe and unavoidable impurities.

[0009] Preferably, the chemical composition of the copper-free X52 pipeline steel submerged arc welding wire provided by the present invention must also ensure that V ≥ 0.016%.

[0010] Preferably, the chemical composition of the copper-free X52 pipeline steel submerged arc welding wire provided by the present invention must also ensure that Nb≥0.1%.

[0011] Preferably, the chemical composition of the submerged arc welding wire for X52 pipeline steel without copper plating provided by the present invention must also ensure that Mn ≥ 0.7%.

[0012] Preferably, in the chemical composition of the copper-free X52 pipeline steel submerged arc welding wire provided by the present invention, the mass percentage of B is 0.003-0.004%.

[0013] Preferably, the chemical composition of the copper-free X52 pipeline steel submerged arc welding wire provided by the present invention must also ensure that Ti ≤ 0.1%.

[0014] Preferably, the chemical composition of the copper-free X52 pipeline steel submerged arc welding wire provided by the present invention must also ensure that Ni ≥ 1%.

[0015] Preferably, the chemical composition of the submerged arc welding wire for X52 pipeline steel without copper plating provided by the present invention has a Ni mass percentage of 1.01-1.26%.

[0016] Preferably, the chemical composition of the submerged arc welding wire for X52 pipeline steel without copper plating provided by the present invention has a Mo mass percentage of 0.27-0.31%.

[0017] This invention provides a submerged arc welding wire for X52 pipeline steel without copper plating, with the following composition design concept:

[0018] (1) C is the main strengthening element in the weld metal microstructure. Excessive C content will affect the crack resistance and impact toughness of the weld metal. It is also a brittle element in the weld, which can easily cause the welding performance to deteriorate. This welding wire adopts a low carbon design and controls C at 0.03%-0.06%.

[0019] (2) Mn is a good deoxidizer and solid solution strengthening element, which can improve the strength and low-temperature impact toughness of the weld metal. However, with the increase of Mn content, the yield strength and tensile strength of the weld metal will increase. For X52 grade hydrogen pipeline steel, the addition of Mn content needs to be reasonably controlled. The Mn content of this welding wire needs to be controlled between 0.4% and 1.0%.

[0020] (3) Si mainly plays a role in deoxidation and strengthening in weld metal. Excessive content will affect the toughness of the weld, deteriorate weldability and increase weld brittleness. The Si content in this welding wire needs to be controlled between 0.10% and 0.50%.

[0021] (4) The lower the content of P and S as impurity elements, the better. Antibacterial corrosion welding wire requires the P and S elements to be controlled as low as possible. Therefore, the P content in the welding wire is controlled below 0.005% and the S content is controlled below 0.005%.

[0022] (5) Ni can lower the low-temperature brittle transition temperature of the weld metal while maintaining its good plasticity and toughness. The Ni content in this welding wire is best controlled between 0.5% and 1.5%.

[0023] (6) Mo promotes the formation of high dislocation density acicular ferrite AF, thereby improving the toughness of the weld metal. However, a high Mo content will weaken the plasticity and toughness of the weld. The Mo content of this welding wire needs to be controlled between 0.10-0.50%.

[0024] (7) Cu can promote the formation of a (FeCu)·S protective film on the steel surface. This protective film can prevent the hydrogen reaction from occurring, reduce the absorption of hydrogen atoms by the weld metal, and thus reduce the embrittlement effect of hydrogen atoms on X52 pipeline steel. The Cu content of this welding wire needs to be controlled between 0.10-0.30%.

[0025] (8) Ti can be used for high heat input welding in submerged arc welding. Ti has a good toughening effect and can form very fine dispersions in the weld, which can effectively prevent grain growth. The fine grains become the nucleation core of needle ferrite, which can further improve the toughness of the weld metal. The Ti content of this welding wire needs to be controlled between 0.05% and 0.15%.

[0026] (9) Nb helps to increase the content of acicular ferrite and fine granular bainitic ferrite in the weld, which can enhance the strength and toughness of the weld metal. After adding Nb, the nano-sized niobium carbides formed in the weld deposited metal can delay the generation of hydrogen-induced bubbles. The Nb content of this welding wire needs to be controlled below 0.15%.

[0027] (10) V can form nanoscale vanadium carbides, increase effective hydrogen traps, and reduce the hydrogen diffusion coefficient. The V content of this welding wire needs to be controlled below 0.03%.

[0028] (11) B can improve the hardenability and toughness of weld metal. In this welding wire, the content of B is best controlled within the range of 0.001-0.008%.

[0029] The present invention has the following beneficial effects:

[0030] (1) The copper-free X52 pipeline steel submerged arc welding wire obtained by the present invention does not contain metallic elements Al, Cr, Ce and Y in its chemical composition. The chemical composition of the submerged arc welding wire, by mass percentage, includes basic elements such as C, Mn, Si, Cu, Mo and Fe, and also contains appropriate amounts of Ni, V, Ti, Nb and B elements. The obtained submerged arc welding wire does not require copper plating treatment and is suitable for high heat input welding of X52 hydrogen pipeline steel pipes. The welded joint has high impact toughness in an environment of -20℃.

[0031] (2) The present invention provides a submerged arc welding wire for X52 hydrogen pipeline steel. The submerged arc welding wire is equipped with alkaline flux SJ101MH. The welded joint has good resistance to HIC and good tensile properties under slow strain rate in hydrogen environment. It has good hydrogen resistance and meets the service requirements of X52 hydrogen pipeline. Detailed implementation method:

[0032] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0033] Example 1

[0034] A copper-free X52 pipeline steel submerged arc welding wire has the following elemental composition by mass percentage:

[0035] C: 0.041%; Mn: 0.72%; Si: 0.26%; Cu: 0.22%; P: 0.008%; S: 0.004%; Ni: 1.01%; Mo: 0.27%; V: 0.019%; Ti: 0.09%; Nb: 0.11%; B: 0.003%; balance Fe and unavoidable impurities.

[0036] Example 2

[0037] A copper-free X52 pipeline steel submerged arc welding wire has the following elemental composition by mass percentage:

[0038] C: 0.056%; Mn: 0.83%; Si: 0.28%; Cu: 0.25%; P: 0.008%; S: 0.005%; Ni: 1.26%; Mo: 0.31%; V: 0.021%; Ti: 0.09%; Nb: 0.10%; B: 0.003%; balance Fe and unavoidable impurities.

[0039] Example 3

[0040] A copper-free X52 pipeline steel submerged arc welding wire has the following elemental composition by mass percentage:

[0041] C: 0.045%; Mn: 0.77%; Si: 0.23%; Cu: 0.21%; P: 0.006%; S: 0.004%; Ni: 1.09%; Mo: 0.28%; V: 0.016%; Ti: 0.08%; Nb: 0.10%; B: 0.004%; balance Fe and unavoidable impurities.

[0042] Example 4

[0043] A copper-free X52 pipeline steel submerged arc welding wire has the following elemental composition by mass percentage:

[0044] C: 0.03%; Mn: 0.4%; Si: 0.1%; Cu: 0.2%; P: 0.006%; S: 0.004%; Ni: 0.5%; Mo: 0.1%; V: 0.016%; Ti: 0.05%; Nb: 0.10%; B: 0.001%; ​​balance Fe and unavoidable impurities.

[0045] Example 5

[0046] A copper-free X52 pipeline steel submerged arc welding wire has the following elemental composition by mass percentage:

[0047] C: 0.06%; Mn: 1%; Si: 0.5%; Cu: 0.25%; P: 0.006%; S: 0.004%; Ni: 1.5%; Mo: 0.5%; V: 0.03%; Ti: 0.15%; Nb: 0.15%; B: 0.008%; balance Fe and unavoidable impurities.

[0048] Comparative Example 1 is the same as Example 1, except that Al element is added to the chemical composition of the submerged arc welding wire of Comparative Example 1, and the mass percentage of Al element is 0.055%.

[0049] Comparative Example 2 is the same as Example 1, except that the submerged arc welding wire of Comparative Example 2 also contains Cr element, with a mass percentage content of 0.1%.

[0050] Comparative Example 3 is the same as Example 1, except that the submerged arc welding wire of Comparative Example 3 also contains Ce element, and the mass percentage of Ce element is 0.05%.

[0051] Comparative Example 4 is the same as Example 1, except that the chemical composition of the submerged arc welding wire in Comparative Example 4 also includes element Y, with a mass percentage content of 0.2% for element Y.

[0052] Comparative Example 5 is the same as Example 1, except that V element was not added to the chemical composition of the submerged arc welding wire in Comparative Example 5.

[0053] Comparative Example 6 is the same as Example 1, except that element B was not added to the chemical composition of the submerged arc welding wire in Comparative Example 6.

[0054] Comparative Example 7 is the same as Example 1, except that Nb element was not added to the chemical composition of the submerged arc welding wire in Comparative Example 7.

[0055] Comparative Example 8 is the same as Example 1, except that Ni element is not added to the chemical composition of the submerged arc welding wire in Comparative Example 8.

[0056] Comparative Example 9 is the same as Example 1, except that Ti element was not added to the chemical composition of the submerged arc welding wire in Comparative Example 9.

[0057] Comparative Example 10 is the same as Example 1, except that the mass percentage of Mn in the chemical composition of the submerged arc welding wire of Comparative Example 10 is 1.3%.

[0058] Comparative Example 11 is the same as Example 1, except that the mass percentage of Si element in the chemical composition of the submerged arc welding wire of Comparative Example 11 is 0.7%.

[0059] Comparative Example 12 is the same as Example 1, except that the mass percentage of Mo in the submerged arc welding wire of Comparative Example 12 is 0.05%.

[0060] Comparative Example 13 is the same as Example 1, except that the mass percentage of Mo in the submerged arc welding wire of Comparative Example 13 is 0.5%.

[0061] Comparative Example 14 is the same as Example 1, except that the mass percentage of Nb in the chemical composition of the submerged arc welding wire of Comparative Example 14 is 0.07%.

[0062] Comparative Example 15 is the same as Example 1, except that the mass percentage of Nb in the chemical composition of the submerged arc welding wire of Comparative Example 15 is 0.2%.

[0063] Comparative Example 16 is the same as Example 1, except that the mass percentage of Ti element in the chemical composition of the submerged arc welding wire of Comparative Example 16 is 0.2%.

[0064] Comparative Example 17 is the same as Example 1, except that the mass percentage content of Ti element in the chemical composition of the submerged arc welding wire of Comparative Example 17 is 0.02%.

[0065] According to the above embodiments 1-5 and comparative examples 1-17 of the present invention, the chemical composition formula of the submerged arc welding wire and the conventional welding material production process are respectively processed. The raw welding material is obtained by sequentially going through hot iron desulfurization and dephosphorization, converter smelting, steel ladle refining, continuous casting, high wire rod, and wire rod rolling. The raw welding material is then sequentially subjected to mechanical peeling, drawing, and finally layer winding to obtain a submerged arc welding wire with a diameter of Φ=4.0mm and no copper plating on the surface.

[0066] Under the same welding process conditions, the submerged arc welding wires obtained in the embodiments and comparative examples of the present invention were combined with the alkaline sintered flux SJ101MH to perform 3-wire submerged arc welding with high heat input on straight seam pipes with a diameter of Φ=610mm. The alkaline sintered flux SJ101MH was composed of 25% SiO2, 21% CaF2, 22% CaO, 21% MgO, and 11% MnO by mass percentage. The 3-wire submerged arc welding with high heat input adopted the internal and external welding processes. The internal welding process was the same as the external welding process. The current of wire 1 was 1050A and the voltage was 35V; the current of wire 2 was 820A and the voltage was 40V; the current of wire 3 was 720A and the voltage was 41V; and the welding speed was 1.5m / min.

[0067] Comparative Example 18 is the same as Example 1, except that the flux used in Comparative Example 18 is alkaline flux SJ101G.

[0068] Performance testing

[0069] (1) Relevant performance tests were conducted on the welded joints formed by submerged arc welding of straight seam pipes in the embodiments and comparative examples of the present invention. Hardness test, tensile test, impact test and bending test were conducted according to the following standards. Hardness test: GB / T 231.1-2018 "Metallic materials Brinell hardness test - Part 1: Test method", tensile test: GB / T 228.1 "Metallic materials tensile test - Part 1: Room temperature test method", impact test: GB / T 229 "Metallic materials Charpy pendulum impact test method", bending test: GB / T 232 "Metallic materials bending test method". The specific test results are shown in Table 1 and Table 1 (continued).

[0070] Table 1

[0071]

[0072] Continued from Table 1

[0073]

[0074] As can be seen from Table 1 and Table 1 (continued), the submerged arc welding wire for X52 hydrogen pipeline steel of the present invention has excellent tensile properties and impact toughness, with a tensile strength of over 530 MPa and a yield strength of over 430 MPa. At the same time, the submerged arc welding wire has excellent impact toughness, with an impact energy of ≥150 J at -20℃. Compared with comparative examples 1-17, the strength and toughness are well matched, which can fully meet the welding requirements of X52 hydrogen pipeline.

[0075] (2) The welded joints formed by submerged arc welding of straight seam pipes in the embodiments and comparative examples of the present invention were tested for HIC resistance according to GB / T 8650 "Evaluation Method for Hydrogen-Induced Cracking Resistance of Pipeline Steel and Pressure Vessel Steel". The test results are shown in Table 2. The test results show that the CLR, CTR, and CSR test results of the welded joints in the HIC resistance test are all 0. The specific test results are shown in Table 2 and Table 2 (continued).

[0076] Table 2

[0077] Test Items CLR (%) CTR (%) CSR (%) Macro Metallography Example 1 0 0 0 No cracks Example 2 0 0 0 No cracks Example 3 0 0 0 No cracks Example 4 0 0 0 No cracks Example 5 0 0 0 No cracks Comparative Example 1 0 0 0 No cracks Comparative Example 2 0 0 0 No cracks Comparative Example 3 0 0 0 No cracks Comparative Example 4 0 0 0 No cracks

[0078] Continued from Table 2

[0079] Test Items CLR (%) CTR (%) CSR (%) Macro Metallography Comparative Example 5 1.2 0.8 0.1 Cracks Comparative Example 6 0 0 0 No cracks Comparative Example 7 1.6 0.9 0.4 Cracks Comparative Example 8 1.8 0.9 0.5 Cracks Comparative Example 9 0.9 0.3 0.1 Cracks Comparative Example 10 0 0 0 No cracks Comparative Example 11 1.3 0.7 0.2 Cracks Comparative Example 12 0 0 0 No cracks Comparative Example 13 0 0 0 No cracks Comparative Example 14 0 0 0 No cracks Comparative Example 15 0 0 0 No cracks Comparative Example 16 0 0 0 No cracks Comparative Example 17 0 0 0 No cracks Comparative Example 18 0 0 0 No cracks

[0080] As can be seen from Table 2 and Table 2 (continued), the X52 submerged arc welding wire for hydrogen pipeline steel of the present invention, in Examples 1-5, not only has excellent strength and toughness, but also excellent hydrogen resistance. In the hydrogen-induced cracking (HIC) test, CLR, CTR, and CSR are all 0, and no cracks are generated in the macroscopic metallographic structure. In contrast, some macroscopic metallographic structures in Comparative Examples 1-17 show cracks.

[0081] (3) Slow tensile tests were conducted on the welded joints formed by submerged arc welding of straight seam pipes after three wires in the embodiments and comparative examples of the present invention, respectively, according to GB / T 34542-2018 "Test Methods for Compatibility of Metallic Materials with Hydrogen Environment". The tests were performed at a pressure of 10 MPa and a strain rate of 1 × 10⁻⁶. -5 Table 3 shows the results of testing the loss rates of strength, elongation, and reduction of area of ​​the welded joint in a hydrogen environment relative to a nitrogen environment under the specified conditions of 10 MPa and 1 × 10⁻⁵ / s. Slow tensile tests were conducted on the welded joints formed by 3-wire submerged arc welding of straight seam pipes (Φ = 610 mm) in both the embodiment and the comparative example of this invention, according to GB / T 34542-2018 "Test Methods for Compatibility of Metallic Materials with Hydrogen Environment". The tests measured the loss rates of strength, elongation, and reduction of area of ​​the welded joint in a hydrogen environment relative to a nitrogen environment under a pressure of 10 MPa and a strain rate of 1 × 10⁻⁵ / s.

[0082] The formula for calculating the strength loss rate is: (Tensile strength of the welded joint in a nitrogen environment - Tensile strength of the welded joint in a hydrogen environment) / Tensile strength of the welded joint in a nitrogen environment × 100%.

[0083] The formula for calculating the elongation loss rate is: (elongation of the welded joint in a nitrogen environment - elongation of the welded joint in a hydrogen environment) / elongation of the welded joint in a nitrogen environment × 100%.

[0084] The formula for calculating the reduction of area loss rate is: (reduction of area of ​​welded joint in nitrogen environment - reduction of area of ​​welded joint in hydrogen environment) / reduction of area of ​​welded joint in nitrogen environment × 100%.

[0085] The specific test results are shown in Table 3 and Table 3 (continued).

[0086] Table 3

[0087] Test Items Tensile strength loss rate elongation loss rate Reduction of area and loss rate Example 1 0.8％ 32.8％ 28.7％ Example 2 0.5％ 32.5％ 29.3％ Example 3 0.6％ 33.2％ 31.8％ Example 4 0.8％ 34.2％ 33.9％ Example 5 0.4％ 33.6％ 31.5％ Comparative Example 1 1.4％ 37.9％ 38.2％ Comparative Example 2 1.7％ 41.3％ 42.6％ Comparative Example 3 0.7％ 33.2％ 27.5％ Comparative Example 4 0.8％ 30.9％ 39.6％ Comparative Example 5 2.5％ 41.5％ 42.7％ Comparative Example 6 3.6％ 43.2％ 39.8％ Comparative Example 7 3.9％ 42.1％ 43.3％ Comparative Example 8 4.2％ 46.5％ 47.6％ Comparative Example 9 2.5％ 41.3％ 42.7％ Comparative Example 10 1.2％ 42.6％ 43.1％ Comparative Example 11 2.6％ 45.1％ 39.6％ Comparative Example 12 1.0％ 37.6％ 35.3％ Comparative Example 13 1.3％ 38.2％ 34.6％

[0088] Continued from Table 3

[0089] Test Items Tensile strength loss rate elongation loss rate Reduction of area and loss rate Comparative Example 14 1.4％ 39.3％ 39.8％ Comparative Example 15 0.8％ 35.6％ 38.4％ Comparative Example 16 1.4％ 34.7％ 33.2％ Comparative Example 17 0.9％ 35.6％ 36.2％ Comparative Example 18 1.7％ 43.8％ 41.6％

[0090] As can be seen from Table 3 and Table 3 (continued), the X52 submerged arc welding wire for hydrogen pipeline steel of the present invention, in Examples 1-5, under a pressure of 10 MPa and a strain rate of 1×10⁻⁵, achieves the desired results. -5Under / S conditions, the strength loss rate of the welded joint in a hydrogen environment compared to that in a nitrogen environment is ≤1.0%, and the reduction of area and elongation loss rates are both ≤35%. The test results of the comparative examples with rare earth elements are similar to those of Examples 1-5, while the strength loss rate, reduction of area and elongation loss rates of the welded joints in the other comparative examples are larger in a hydrogen environment compared to that in a nitrogen environment.

[0091] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A submerged arc welding wire for X52 pipeline steel without copper plating, characterized in that, Its chemical composition does not contain the metallic elements Al, Cr, Ce, and Y. The chemical composition of submerged arc welding wire, by mass percentage, includes the following components: C: 0.03-0.06%; Mn: 0.4-1.0%; Si: 0.10-0.50%; Cu: 0.2-0.25%; P≤0.005%; S≤0.005%; Ni: 0.50-1.5%; Mo: 0.10-0.50%; 0.016%≤V≤0.03%; Ti: 0.05-0.15%; 0.1%≤Nb≤0.15%; B: 0.001-0.008%; balance Fe and unavoidable impurities.

2. The submerged arc welding wire for X52 pipeline steel without copper plating according to claim 1, characterized in that, Mn≥0.7%.

3. The submerged arc welding wire for X52 pipeline steel without copper plating according to claim 1, characterized in that, The mass percentage of B is 0.003-0.004%.

4. The submerged arc welding wire for X52 pipeline steel without copper plating according to claim 1, characterized in that, Ti≤0.1%.

5. The submerged arc welding wire for X52 pipeline steel without copper plating according to claim 1, characterized in that, Ni ≥ 1%.

6. The submerged arc welding wire for X52 pipeline steel without copper plating according to claim 5, characterized in that, The mass percentage of Ni is 1.01-1.26%.

7. The submerged arc welding wire for X52 pipeline steel without copper plating according to claim 1, characterized in that, The mass percentage of Mo is 0.27-0.31%.

8. A method for submerged arc welding of copper-free X52 pipeline steel, characterized in that, The submerged arc welding wire obtained according to any one of claims 1-7 is used as the welding wire, and the alkaline flux SJ101MH is used as the matching flux.

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