High-strength acid-resistant steel submerged arc welding wire for submarine pipeline and application thereof

Abstract

This invention relates to the field of welding materials technology, and in particular to a high-strength acid-resistant steel submerged arc welding wire for subsea pipelines and its application; the submerged arc welding wire comprises the following components by mass percentage: C: 0.02-0.04%, Mn: 0.2-0.4%, Cr: 0.1-0.3%, Mo: 0.1-0.3%, Ni: 0.5-1.0%, Cu: 0.1-0.3%, Sr: 0.004-0.008%, Ti: 0.1-0.2%, Ce: 0.02-0.03%, B: 0.006-0.01%, S≤0.003%, P≤0.005%; the remainder being Fe and unavoidable impurities. The submerged arc welding wire of the present invention has a tensile strength of over 640 MPa, a yield strength of over 550 MPa, and a yield ratio of ≤0.88. At the same time, the submerged arc welding wire has stable low-temperature impact toughness, with an impact energy of ≥130 J at -40℃ and ≥90 J at -50℃.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, and in particular to a high-strength acid-resistant steel submerged arc welding wire for subsea pipelines and its application. Background Technology

[0002] In recent years, with the continuous increase in energy demand and the ongoing depletion of high-quality oil and gas resources, oil and gas development has increasingly extended from land to sea. Oil and gas containing large amounts of wastewater, associated gas, H2S, and other corrosive media are transported through pipelines, leading to increasingly severe pipeline corrosion. To address these issues, since the 1990s, domestic steel companies such as Baosteel, Panzhihua Iron and Steel, and Wuhan Iron and Steel have successively developed acid-resistant pipeline steel plates such as X56MS, X60MS, and X65MS. Currently, acid-resistant steel plates are being used extensively, and the industry is developing towards high-strength, acid-corrosion-resistant pipeline steels such as X70MS. The use of acid-resistant steel is gradually becoming a development trend in pipeline transportation materials.

[0003] Traditional welding consumables for pipeline steel are primarily ferritic-pearlitic in structure, with welding wires mainly being H08C and H08D, primarily based on Mn-Mo-Ti-B and Mn-Ni systems. These cannot meet the corrosion resistance requirements of X52MS, X60MS, X65MS, and X70MS steels against acid corrosion. Currently, the development of welding consumables for acid-resistant pipeline steel is severely lagging. While there is a limited supply of welding consumables for X52MS, X60MS, and X65MS, no welding materials for X70MS acid-resistant steel plates have been reported. The main challenge in developing welding consumables for X70MS acid-resistant steel plates lies in the fact that subsea pipelines not only face the harsh conditions of high pressure, undulating terrain, ocean currents, crustal movement, and low temperatures, requiring welding consumables to meet high strength and high / low temperature impact toughness requirements, but also, with the increasing variety of pipeline service conditions and transported media, higher requirements are being placed on corrosion resistance against acid corrosion.

[0004] Therefore, it is necessary to design a high-strength acid-resistant steel submerged arc welding wire for submerged pipelines to overcome the above problems. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a high-strength, acid-resistant steel submerged arc welding wire for submerged pipelines. This wire comprises the following components by mass percentage: C: 0.02–0.04%, Mn: 0.2–0.4%, Cr: 0.1–0.3%, Mo: 0.1–0.3%, Ni: 0.5–1.0%, Cu: 0.1–0.3%, Sr: 0.004–0.008%, Ti: 0.1–0.2%, Ce: 0.02–0.03%, B: 0.006–0.01%, S≤0.003%, P≤0.005%; the remainder being Fe and unavoidable impurities.

[0006] Furthermore, the submerged arc welding wire also includes the following components by mass percentage: N < 10 ppm, H < 1 ppm, O < 10 ppm.

[0007] Where 1ppm = 10 -6 (The same applies below.)

[0008] Further, the submerged arc welding wire comprises the following components by mass percentage: C: 0.03%, Mn: 0.3%, Cr: 0.15%, Mo: 0.25%, Ni: 0.7%, Cu: 0.3%, Sr: 0.0055%, Ti: 0.12%, Ce: 0.025%, B: 0.007%, S: 0.002%, P: 0.004%, N: 7ppm, H: 0.3ppm, O: 5ppm; the remainder being Fe and unavoidable impurities.

[0009] Further, the submerged arc welding wire comprises the following components by mass percentage: C: 0.025%, Mn: 0.2%, Cr: 0.2%, Mo: 0.1%, Ni: 0.6%, Cu: 0.25%, Sr: 0.0060%, Ti: 0.15%, Ce: 0.03%, B: 0.01%, S: 0.003%, P: 0.004%, N: 9ppm, H: 0.8ppm, O: 9ppm; the remainder being Fe and unavoidable impurities.

[0010] Further, the submerged arc welding wire comprises the following components by mass percentage: C: 0.03%, Mn: 0.2%, Cr: 0.25%, Mo: 0.25%, Ni: 0.9%, Cu: 0.25%, Sr: 0.0050%, Ti: 0.18%, Ce: 0.03%, B: 0.008%, S: 0.003%, P: 0.003%, N: 8ppm, H: 0.5ppm, O: 8ppm; the remainder being Fe and unavoidable impurities.

[0011] Furthermore, the diameter of the submerged arc welding wire is 2.4mm to 6.4mm, and the diameter deviation is controlled within -0.1mm to 0mm.

[0012] Furthermore, the out-of-roundness of the submerged arc welding wire is ≤0.03mm.

[0013] On the other hand, the present invention also provides the application of the high-strength acid-resistant steel submerged arc welding wire for submerged pipelines as described above, wherein the submerged arc welding wire is used in conjunction with a fluorine-alkali sintered flux for welding, and the flux alkalinity is controlled at 1.6-2.2.

[0014] Furthermore, the fluorine-alkali sintering flux is at least one of SJ101G flux, SJ102G flux, and SJ105G flux, and the flux is dehumidified at 350-400°C for at least 2 hours before use.

[0015] In the high-strength acid-resistant steel submerged arc welding wire for submerged pipelines of the present invention, the main roles of each component in the design of the submerged arc welding wire are as follows:

[0016] Carbon (C) primarily plays a significant role in improving the strength of welding wire. Generally, the higher the C content, the worse the material's resistance to stress corrosion cracking (HIC). In particular, when the C content is greater than 0.04%, the deterioration of the material's HIC resistance becomes more pronounced. At the same time, it also causes the segregation of manganese and phosphorus elements, forming banded structures, which greatly increases the probability of crack initiation and propagation. Therefore, adopting a low-carbon design and controlling the C content between 0.02% and 0.04% can both ensure the strength of the weld and effectively reduce stress corrosion cracking.

[0017] Mn is mainly added to the weld to strengthen it through solid solution, improve its hardenability, and enhance its strength and hardness. As an austenite expansion zone element, appropriate Mn content promotes pearlite formation. Increasing the Mn / C ratio can effectively improve the material's resistance to HIC. At the same time, the Mn / C ratio must be kept between 5 and 20, as this range yields a better microstructure. Therefore, a low-Mn design, controlling Mn content to 0.2-0.4%, can effectively reduce the formation of MnS, improve resistance to sulfur attack, and reduce the material's susceptibility to HIC.

[0018] Cr and Mo elements are mainly used to compensate for the insufficient strength of weld metal caused by low carbon and low manganese design. At the same time, the addition of Cr and Mo elements, together with Cu elements, can improve the weather resistance index of weld metal, thereby improving corrosion resistance.

[0019] Ni primarily enhances the low-temperature impact toughness of welds.

[0020] The Cu element is controlled at 0.1-0.3%. On the one hand, it can improve the weather resistance index of the material, thereby improving its corrosion resistance. On the other hand, Cu can also effectively inhibit the diffusion and penetration of hydrogen into the weld metal.

[0021] Sr, as a trace element, plays an important role in acid-resistant steel. First, it can regulate the shape and distribution of oxides. The spherical SrO formed in the weld can replace the severely segregated banded MnS, thereby reducing the influence of sharp, elongated inclusions and uneven distribution on crack sensitivity and improving HIC resistance. Second, spherical SrO can form some inclusion points, which pin dislocation movement, prevent crack propagation, and reduce crack sensitivity. Finally, the uniformly dispersed spherical SrO helps to improve the impact toughness of the weld.

[0022] Ti and B, as trace alloying elements, mainly play the roles of grain refinement and dispersion strengthening. By forming stable compounds with elements such as C, O and N, they can control the cooling rate and disperse precipitation in the weld, thereby improving the weld toughness and strength. In particular, the Ti-B combined system can prevent crack propagation by forming fine, high-density dislocation pairs, thus significantly improving the weld's resistance to cracking (SSC).

[0023] Ce is added in the form of CeO during the smelting process of rare earth elements. Its main function is that Ce can act as an effective nucleation point and be dispersed in the weld during the welding metallurgy process, which promotes the refinement of ferrite and the formation of ultrafine needle-like ferrite. The formation of rare earth oxides also plays a role in purifying and dispersing the weld metal, preventing the banding and sharp cornering of inclusions, thereby improving the weld metal's resistance to H2S.

[0024] Sulfur (S) and phosphorus (P), as harmful impurities, severely deteriorate the impact properties of weld metal, reduce weld toughness, and increase the risk of joint cracking. In particular, the Mn segregation caused by Mn in the formed MnS inclusions significantly reduces the joint's resistance to H2S corrosion. P can also greatly increase cold cracking susceptibility and reduce resistance to H2S corrosion. Adopting a low-S and P design, controlling S below 0.003% and P below 0.005%, can effectively reduce the damage caused by these two harmful elements.

[0025] As harmful gaseous elements, nitrogen (N), hydrogen (H), and oxygen (O) significantly increase strength but decrease toughness during welding, causing weld embrittlement and easily forming nitrogen pores that reduce joint performance. High-pressure hydrogen clouds formed by hydrogen are a major driving force for crack initiation and propagation, increasing the risk of weld joint cracking. O can form oxides with almost all metals, and large oxide inclusions are also a major source of corrosion and degradation. Adopting a purification design plays a crucial role in improving joint microstructure uniformity and enhancing resistance to H2S corrosion.

[0026] The high-strength acid-resistant steel submerged arc welding wire for submerged pipelines provided by this invention meets the welding requirements of X70MS acid-resistant steel submerged pipelines. In addition to high strength and high toughness, this submerged arc welding wire also has excellent resistance to H2S corrosion. Through ultra-low C, S and P design, the segregation of carbide and sulfide inclusions in the weld is reduced. By reducing the N, H and O content in the submerged arc welding wire, the formation of non-metallic inclusions is further reduced. By controlling appropriate Sr and Cu, the shape of inclusions is improved. By adding Ce, Ti, B and some rare earth elements, the grains are refined, and dispersion strengthening is used to prevent crack propagation. This greatly improves the weld performance and resistance to H2S and SSC, and can fully meet the welding requirements of X70MS acid-resistant steel submerged pipelines.

[0027] This invention precisely controls the content of each element, and after smelting, it is rolled into wire rod. The wire rod is then processed into submerged arc welding wire using either copper plating or a copper-free process. During the preparation of the submerged arc welding wire, the final composition of the converter steelmaking process is controlled based on CO2 composite injection. This is achieved by adjusting the molten pool heating rate, increasing the contact area between bubbles and molten steel, and reducing the equilibrium CO partial pressure, thereby controlling and optimizing the phosphorus, nitrogen, and oxygen content of the molten steel at the converter's final stage.

[0028] By employing the above technical solutions, this invention has the following advantages compared to existing technologies:

[0029] 1) The high-strength acid-resistant steel submerged arc welding wire for submerged pipelines provided by this invention has a tensile strength of over 640MPa, a yield strength of over 550MPa, and a yield ratio of ≤0.88; at the same time, the submerged arc welding wire has stable low-temperature impact toughness, with an impact energy of ≥130J at -40℃ and ≥90J at -50℃.

[0030] 2) The high-strength acid-resistant steel submerged arc welding wire for submerged pipelines provided by this invention, in addition to having high strength and high toughness, also has excellent resistance to H2S corrosion; the sulfide stress corrosion resistance (SSC) test meets the requirement that the thickness direction crack is ≤0.1mm when the threshold stress is exceeded; in the hydrogen induced cracking (HIC) test, CLR≤0.5%, CTR≤0.5%, and CSR≤0.5%;

[0031] 3) The high-strength acid-resistant steel submerged arc welding wire for submerged pipelines provided by this invention has a diffusible hydrogen content as low as 3ml / 100g, which can effectively reduce hydrogen-induced cracking and improve crack resistance.

[0032] 4) The high-strength acid-resistant steel submerged arc welding wire for submerged pipelines provided by this invention can perform high heat input welding, with heat input reaching more than 50KJ / cm, while still obtaining excellent mechanical properties, which can effectively improve welding speed and welding construction efficiency. Detailed Implementation

[0033] 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.

[0034] This invention provides a high-strength acid-resistant steel submerged arc welding wire for submerged pipelines. The submerged arc welding wire comprises the following components by mass percentage: C: 0.02-0.04%, Mn: 0.2-0.4%, Cr: 0.1-0.3%, Mo: 0.1-0.3%, Ni: 0.5-1.0%, Cu: 0.1-0.3%, Sr: 0.004-0.008%, Ti: 0.1-0.2%, Ce: 0.02-0.03%, B: 0.006-0.01%, S≤0.003%, P≤0.005%; the remainder being Fe and unavoidable impurities.

[0035] In an optimized implementation, the submerged arc welding wire further includes the following components by mass percentage: N < 10 ppm, H < 1 ppm, O < 10 ppm.

[0036] The following detailed examples illustrate this point:

[0037] Example 1

[0038] This embodiment provides a high-strength acid-resistant steel submerged arc welding wire for submerged pipelines. The submerged arc welding wire comprises the following components by mass percentage: C: 0.02%, Mn: 0.4%, Cr: 0.10%, Mo: 0.20%, Ni: 0.5%, Cu: 0.20%, Sr: 0.0045%, Ti: 0.10%, Ce: 0.02%, B: 0.009%, S: 0.003%, P: 0.005%, N: 9 × 10⁻⁶. -4 %, H: 0.8×10 -4 %, O: 9×10 -4 %; the remainder is Fe and unavoidable impurities.

[0039] Example 2

[0040] This embodiment provides a high-strength acid-resistant steel submerged arc welding wire for submerged pipelines. The submerged arc welding wire comprises the following components by mass percentage: C: 0.025%, Mn: 0.2%, Cr: 0.20%, Mo: 0.1%, Ni: 0.6%, Cu: 0.25%, Sr: 0.0060%, Ti: 0.15%, Ce: 0.03%, B: 0.01%, S: 0.003%, P: 0.004%, N: 9×10⁻⁶. -4 %, H: 0.8×10 -4 %, O: 9×10 -4 %; the remainder is Fe and unavoidable impurities.

[0041] Example 3

[0042] This embodiment provides a high-strength acid-resistant steel submerged arc welding wire for submerged pipelines. The submerged arc welding wire comprises the following components by mass percentage: C: 0.03%, Mn: 0.3%, Cr: 0.15%, Mo: 0.25%, Ni: 0.7%, Cu: 0.3%, Sr: 0.0055%, Ti: 0.12%, Ce: 0.025%, B: 0.007%, S: 0.002%, P: 0.004%, N: 7 × 10⁻⁶. -4 %, H: 0.3×10 -4 %, O: 5×10 -4 %; the remainder is Fe and unavoidable impurities.

[0043] Example 4

[0044] This embodiment provides a high-strength acid-resistant steel submerged arc welding wire for subsea pipelines. The submerged arc welding wire comprises the following components by mass percentage: C: 0.03%, Mn: 0.2%, Cr: 0.25%, Mo: 0.25%, Ni: 0.9%, Cu: 0.25%, Sr: 0.0050%, Ti: 0.18%, Ce: 0.03%, B: 0.008%, S: 0.003%, P: 0.003%, N: 8×10⁻⁶. -4 %, H: 0.5×10 -4 %, O: 8×10 -4 %; the remainder is Fe and unavoidable impurities.

[0045] Example 5

[0046] This embodiment provides a high-strength acid-resistant steel submerged arc welding wire for submerged pipelines. The submerged arc welding wire comprises the following components by mass percentage: C: 0.04%, Mn: 0.4%, Cr: 0.3%, Mo: 0.25%, Ni: 1.0%, Cu: 0.3%, Sr: 0.0075%, Ti: 0.19%, Ce: 0.025%, B: 0.007%, S: 0.002%, P: 0.004%, N: 8×10⁻⁶. -4 %, H: 0.5×10 -4 %, O: 8×10 -4 %; the remainder is Fe and unavoidable impurities.

[0047] The high-strength acid-resistant steel submerged arc welding wire for submerged pipelines provided in Examples 1-5 has a diameter of 2.4mm to 6.4mm, a diameter deviation controlled within -0.1 to 0mm, and an out-of-roundness ≤0.03mm.

[0048] Preferably, the submerged arc welding wire is used to weld pipeline steel with a commonly used fluorine-alkali sintered flux, preferably at least one of SJ101G, SJ102G, and SJ105G fluxes. The flux alkalinity is controlled between 1.6 and 2.2. Before use, the flux is dehumidified at 350 to 400°C for 2 hours.

[0049] The submerged arc welding wire products prepared using Examples 1-5 were subjected to fusion metal deposition tests, sulfide stress corrosion tests, and hydrogen-induced cracking tests. The results are shown in the table below:

[0050] Table 1 Mechanical properties of the deposited metal

[0051]

[0052] As can be seen from Table 1, the high-strength acid-resistant steel submerged arc welding wire for submerged pipelines of the present invention has excellent strength and low-temperature impact toughness. The tensile strength can reach more than 640 MPa, the yield strength is more than 550 MPa, and the yield ratio is ≤0.88. At the same time, the submerged arc welding wire has stable low-temperature impact toughness, with an impact energy of ≥130 J at -40℃ and ≥90 J at -50℃, which can fully meet the welding requirements of X70MS acid-resistant steel submerged pipelines.

[0053] Table 2. Experimental performance against hydrogen-induced cracking (HIC)

[0054] CLR (%) CTR (%) CSR (%) Macro Metallography Example 1 0 0 0 No bulges or cracks Example 2 0 0 0 No bulges or cracks Example 3 0 0 0 No bulges or cracks Example 4 0 0 0 No bulges or cracks Example 5 0 0 0 No bulges or cracks

[0055] Table 3. Test performance of resistance to sulfide stress corrosion cracking (SSC)

[0056] 80σs %100σs %140σs Example 1 In good condition, without cracks In good condition, without cracks In good condition, without cracks Example 2 In good condition, without cracks In good condition, without cracks In good condition, without cracks Example 3 In good condition, without cracks In good condition, without cracks In good condition, without cracks Example 4 In good condition, without cracks In good condition, without cracks In good condition, without cracks Example 5 In good condition, without cracks In good condition, without cracks In good condition, without cracks

[0057] As can be seen from Table 2, the high-strength acid-resistant steel submerged arc welding wire for submerged pipelines of the present invention, in addition to having high strength and high toughness, also has excellent resistance to H2S corrosion; the sulfide stress corrosion (SSC) test meets the requirement that there are no cracks in the thickness direction when the threshold stress is exceeded; in the hydrogen-induced cracking (HIC) test, CLR, CTR, and CSR are all 0.

[0058] Those skilled in the art will understand that the present invention can be implemented in many other specific forms without departing from the spirit and scope of the invention. Although embodiments of the invention have been described, it should be understood that the invention is not limited to these embodiments, and those skilled in the art can make changes and modifications within the spirit and scope of the invention as defined in the appended claims.

Claims

1. A high-strength acid-resistant steel submerged arc welding wire for submerged pipelines, characterized in that, The submerged arc welding wire comprises the following components by mass percentage: C: 0.02–0.04%, Mn: 0.2–0.4%, Cr: 0.1–0.3%, Mo: 0.1–0.3%, Ni: 0.5–1.0%, Cu: 0.1–0.3%, Sr: 0.004–0.008%, Ti: 0.1–0.2%, Ce: 0.02–0.03%, B: 0.006–0.01%, S≤0.003%, P≤0.005%; the remainder being Fe and unavoidable impurities.

2. The high-strength acid-resistant steel submerged arc welding wire for submerged pipelines according to claim 1, characterized in that, The submerged arc welding wire also includes the following components by mass percentage: N < 10 ppm, H < 1 ppm, O < 10 ppm.

3. The high-strength acid-resistant steel submerged arc welding wire for submerged pipelines according to claim 2, characterized in that, The submerged arc welding wire comprises the following components by mass percentage: C: 0.03%, Mn: 0.3%, Cr: 0.15%, Mo: 0.25%, Ni: 0.7%, Cu: 0.3%, Sr: 0.0055%, Ti: 0.12%, Ce: 0.025%, B: 0.007%, S: 0.002%, P: 0.004%, N: 7ppm, H: 0.3ppm, O: 5ppm; the remainder being Fe and unavoidable impurities.

4. The high-strength acid-resistant steel submerged arc welding wire for submerged pipelines according to claim 2, characterized in that, The submerged arc welding wire comprises the following components by mass percentage: C: 0.025%, Mn: 0.2%, Cr: 0.2%, Mo: 0.1%, Ni: 0.6%, Cu: 0.25%, Sr: 0.0060%, Ti: 0.15%, Ce: 0.03%, B: 0.01%, S: 0.003%, P: 0.004%, N: 9ppm, H: 0.8ppm, O: 9ppm; The remainder consists of Fe and unavoidable impurities.

5. The high-strength acid-resistant steel submerged arc welding wire for submerged pipelines according to claim 2, characterized in that, The submerged arc welding wire comprises the following components by mass percentage: C: 0.03%, Mn: 0.2%, Cr: 0.25%, Mo: 0.25%, Ni: 0.9%, Cu: 0.25%, Sr: 0.0050%, Ti: 0.18%, Ce: 0.03%, B: 0.008%, S: 0.003%, P: 0.003%, N: 8ppm, H: 0.5ppm, O: 8ppm; The remainder consists of Fe and unavoidable impurities.

6. The high-strength acid-resistant steel submerged arc welding wire for submerged pipelines according to claim 1, characterized in that, The diameter of the submerged arc welding wire is 2.4mm to 6.4mm, and the diameter deviation is controlled within -0.1mm to 0mm.

7. The high-strength acid-resistant steel submerged arc welding wire for submerged pipelines according to claim 1, characterized in that, The out-of-roundness of the submerged arc welding wire is ≤0.03mm.

8. The application of the high-strength acid-resistant steel submerged arc welding wire for submerged pipelines as described in any one of claims 1 to 7, characterized in that, The submerged arc welding wire is used in conjunction with a fluorine-alkali sintered flux for welding, and the flux alkalinity is controlled between 1.6 and 2.

2.

9. The application of the high-strength acid-resistant steel submerged arc welding wire for submerged pipelines according to claim 8, characterized in that, The fluorine-alkali sintering flux is at least one of SJ101G flux, SJ102G flux, and SJ105G flux. Before use, the flux should be dehumidified at 350-400℃ for at least 2 hours.

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