Special high-strength steel MAG welding wire for deep sea and polar region major equipment as well as preparation method and application of special high-strength steel MAG welding wire

Abstract

The invention discloses a special high-strength steel MAG welding wire for deep sea and polar region major equipment and a preparation method and application thereof, and belongs to the technical field of welding materials and preparation thereof. The MAG welding wire for the special high-strength steel solves the problems that under the extreme condition, the impact toughness is low, the welding liquefaction crack sensitive index is high, a welding heat affected zone is embrittled, and high strength cannot be achieved at the same time. The high-strength steel welding wire comprises C, Si, Mn, P, Ti, Cr, Ni, Mo, O, N and the balance Fe and inevitable impurities. By controlling harmful elements such as S, P, O and the like and adding a proper amount of elements such as Ti, N and the like, under the combined action of alloy elements such as Cr, Ni, Mo and the like, the welding seam strength and toughness are guaranteed, under the extreme conditions, the high-strength low-temperature impact toughness can be shown while the high-strength low-temperature impact toughness is achieved, and the impact absorbing energy at the temperature of 50 DEG C below zero can reach 75 J or above.

Description

Technical Field

[0001] This invention belongs to the field of welding materials and their preparation technology, and in particular relates to a special high-strength steel MAG welding wire for heavy equipment in deep sea and polar regions, its preparation method and application. Background Technology

[0002] In extreme environments such as the deep sea and polar regions, the research and application of major equipment are crucial foundations for marine resource development, polar shipping route utilization, and related scientific research activities. Welding technology, as a core process in the manufacturing of large equipment, directly determines the structural integrity, service safety, and service life of the equipment. As a critical area in the structure, the performance of welded joints under harsh environments such as complex alternating loads, extreme low temperatures, and high-pressure corrosion is a decisive factor affecting the reliability of the entire equipment system. In the manufacturing process of large welded components, the selection of matching welding materials and the rationality of the welding process have a decisive impact on the microstructure and mechanical properties of the welded joints.

[0003] Currently, traditional high-strength structural steels widely used in heavy equipment in the deep sea and polar regions typically rely on increasing carbon content or adding large amounts of alloying elements to achieve strength enhancement. However, such methods often lead to a significant deterioration in weldability, specifically increased susceptibility to weld liquefaction cracking, intensified embrittlement of the heat-affected zone, and insufficient toughness reserve in the joint. This not only complicates the welding process but also necessitates multiple auxiliary measures such as preheating and post-heating, increasing manufacturing costs and the difficulty of quality control. As heavy equipment in the deep sea and polar regions continues to develop towards larger sizes and higher design parameters, the workload of welding continues to increase, while placing more stringent requirements on the strength and low-temperature toughness of steel. Against this backdrop, how to achieve high strength in steel while ensuring that the welded joint possesses excellent low-temperature toughness, crack resistance, and service reliability, and further simplify the on-site welding process, has become a core technological bottleneck that urgently needs to be overcome in the field of welding materials and processes. Summary of the Invention

[0004] This invention addresses the problems of low impact toughness, high sensitivity index to welding liquefaction cracks, embrittlement of the welding heat-affected zone, and inability to simultaneously achieve high strength in special high-strength steel MAG welding wires under extreme conditions. It also fills the gap in the availability of welding wires for special high-strength steel in the 700-1000 MPa range. This invention provides a special high-strength steel MAG welding wire for heavy equipment in deep-sea and polar regions, and its preparation method.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: One objective of this invention is to provide a special high-strength steel MAG welding wire for heavy equipment used in deep-sea and polar regions. The chemical composition of this welding wire, by weight percentage, includes: C: 0.02~0.11%, Si: 0.2~1.0%, Mn: 1.0~2.0%, S: ≤0.010%, P: ≤0.010%, Ti: 0.02~0.1%, Cr: 0.2~1.0%, Ni: 2.8~3.5%, Mo: 0.30~1.0%, O: ≤100ppm, N: ≤100 ppm, with the balance being Fe and unavoidable impurities.

[0006] Further specifying, the chemical composition of the MAG welding wire by weight percentage includes: C: 0.03~0.10%, Si: 0.2~0.8%, Mn: 1.30~1.80%, S: ≤0.010%, P: ≤0.010%, Ti: 0.02~0.08%, Cr: 0.2~0.60%, Ni: 3.0~3.4%, Mo: 0.30~0.8%, O: ≤80 ppm, N: ≤80 ppm, with the balance being Fe and unavoidable impurities.

[0007] The second objective of this invention is to provide a method for preparing the above-mentioned special high-strength steel MAG welding wire for heavy equipment in deep sea and polar regions. This preparation method includes the following steps: S1: The welding wire raw material is successively smelted, electroslag remelted, forged and high-speed hot rolled to obtain wire rod; S2: The wire rod is unloaded, peeled, sanded, and then drawn using a roller die. It is then ultrasonically cleaned, dried, and given a surface anti-rust treatment. Finally, it is wound into a densely packed layer on a spool to obtain the finished welding wire.

[0008] Further specified, the diameter of the wire rod in S1 is Ф5.5 mm.

[0009] Further specifying, the drawing speed of S2 is 200~300 m / min.

[0010] Further specified, the diameter of the welding wire in S2 is Ф1.2 mm.

[0011] Furthermore, the diameter tolerance of the welding wire for S2 is ±0.04 mm.

[0012] Further specifying, the S2 roller drawing process involves 14 consecutive drawing passes.

[0013] Further specifying, the S3 surface rust prevention treatment is copper plating or surface coating with rust-preventive oil.

[0014] The third objective of this invention is to provide a welding process for MAG welding of special high-strength steel for heavy equipment in deep sea and polar regions. The process uses the aforementioned welding wire, and the welding process parameters are as follows: welding current 275 A, welding voltage 30 V, shielding gas is a mixture of 80 vol% Ar and 20 vol% CO2, gas flow rate is 20 L / min, welding speed is 330 cm / min, and interpass temperature is 135~165℃.

[0015] The fourth objective of this invention is to provide a weld metal obtained by the above welding process, wherein the weld metal has a tensile strength ≥850 MPa, a yield strength ≥800 MPa, and an impact energy ≥75 J at -50℃.

[0016] The present invention has the following beneficial effects: (1) The high-strength steel welding wire of the present invention effectively reduces the possibility of liquefaction cracking defects caused by thermal cycling during welding by controlling harmful elements such as S, P, and O. By adding appropriate amounts of elements such as Ti and N, relatively small TiN compounds are formed in the weld, which effectively refines the grains and promotes the nucleation of acicular ferrite. Under the combined action of alloying elements such as Cr, Ni, and Mo, the strength and toughness of the weld are guaranteed. Excessive Ti and N elements will lead to excessively large TiN particles, weaken the dispersion strengthening effect, and cause a decrease in plasticity and toughness due to stress concentration.

[0017] (2) The high-strength steel welding wire of the present invention has high strength and good low-temperature impact toughness under extreme conditions. The impact absorption energy at -50℃ can reach more than 75 J, which ensures the service safety of major equipment in the deep sea and polar regions. Attached Figure Description Figure 1 Here is a macroscopic image of the weld cross-section obtained after welding in Example 4: Figure 2 These are macroscopic images of the specimens after the bending test of the deposited metal in Examples 1-4. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification. Many specific details are set forth in the following description to provide a thorough understanding of the present invention; however, the present invention may also be implemented in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0019] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0021] Example 1 The chemical composition of the welding wire in this embodiment, by weight percentage, includes: C: 0.078%, Si: 0.56%, Mn: 1.67%, S: 0.0038%, P: 0.0044%, Ti: 0.061%, Cr: 0.39%, Ni: 3.12%, Mo: 0.38%, O: 23 ppm, N: 31 ppm, with the balance being Fe and unavoidable impurities.

[0022] The above-mentioned welding wire is prepared as follows: A wire rod with a diameter of Ф5.5 mm is obtained through processes such as smelting, electroslag remelting, forging, and high-speed hot rolling. After unwinding, peeling, and belt grinding, the wire rod is subjected to 14 continuous drawing passes at a speed of 200~300 m / min using a roller die and mold to reduce its diameter, resulting in a welding wire with a diameter of Ф1.2 mm and a diameter tolerance of ±0.04 mm. The welding wire is then prepared online using ultrasonic welding: it is cleaned, dried, coated with anti-rust oil, and wound in close-packed layers by a spool to obtain a finished welding wire with a diameter of 1.2 mm.

[0023] The welding wire prepared in this embodiment was used to weld joint test plates of 850 MPa grade high-strength steel. The base metal type was type 1.3 in GB / T 25774.1-2023 "Inspection of Welding Materials - Part 1: Preparation of Specimens for Mechanical Properties of Deposited Metals of Steel, Nickel and Nickel Alloys", i.e., a single-sided bevel of 10°, a root gap of 16 mm, and a butt plate size of 300×316×20 mm. The tensile properties, impact properties, and bending tests of the weld deposited metal were performed according to the following standards: GB / T2652-2022 "Destructive Testing of Welds in Metallic Materials - Longitudinal Tensile Test of Weld Metal in Fusion Welded Joints", GB / T 2650-2022 "Destructive Testing of Welds in Metallic Materials - Impact Test", and GB / T 2653-2008 "Bending Test Method for Welded Joints".

[0024] The welding parameters in this embodiment are as follows: welding current 275 A (DC reverse polarity), welding voltage 30 V, shielding gas volume ratio 20% CO2 + 80% Ar, gas flow rate 20 L / min, welding speed 330 cm / min, preheating temperature 100℃, and interpass temperature 135~165℃.

[0025] The cross-section of the weld after welding in this embodiment is as follows: Figure 1 As shown.

[0026] Example 2 The difference from Example 1 is that the chemical composition of the welding wire by weight percentage includes: C: 0.069%, Si: 0.56%, Mn: 1.66%, S: 0.0042%, P: 0.0056%, Ti: 0.057%, Cr: 0.37%, Ni: 3.26%, Mo: 0.52%, O: 30 ppm, N: 34 ppm, with the balance being Fe and unavoidable impurities. The remaining operating steps and parameter settings are the same as in Example 1.

[0027] Example 3 The difference from Example 1 is that the chemical composition of the welding wire by weight percentage includes: C 0.083%, Si 0.65%, Mn: 1.73%, S: 0.0046%, P: 0.0047%, Ti: 0.066%, Cr: 0.46%, Ni: 3.23%, Mo: 0.38%, O: 28 ppm, N: 36 ppm, with the balance being Fe and unavoidable impurities. The remaining operating steps and parameter settings are the same as in Example 1.

[0028] Example 4 The difference from Example 1 is that the chemical composition of the welding wire by weight percentage includes: C: 0.072%, Si: 0.57%, Mn: 1.67%, S: 0.0051%, P: 0.0055%, Ti: 0.067%, Cr: 0.27%, Ni: 3.18%, Mo: 0.57%, O: 30 ppm, N: 33 ppm, with the balance being Fe and unavoidable impurities. The remaining operating steps and parameter settings are the same as in Example 1.

[0029] The cross-section of the weld after welding in this embodiment is as follows: Figure 1 As shown.

[0030] Comparative Example 1 The difference from Example 1 is that the chemical composition of the welding wire by weight percentage includes: C: 0.072%, Si: 0.56%, Mn: 1.54%, S: 0.006%, P: 0.008%, Ni: 0.82%, Mo: 0.35%, with the balance being Fe and impurities. The remaining operating steps and parameter settings are the same as in Example 1.

[0031] Comparative Example 2 The difference from Example 1 is that the chemical composition of the welding wire by weight percentage includes: C: 0.078%, Si: 0.56%, Mn: 1.65%, S: 0.006%, P: 0.007%, Ni: 1.36%, Mo: 0.45%, with the balance being Fe and unavoidable impurities. The remaining operating steps and parameter settings are the same as in Example 1.

[0032] Comparative Example 3 The difference from Example 1 is that the chemical composition of the welding wire by weight percentage includes: C: 0.092%, Si: 0.78%, Mn: 1.77%, S: 0.003%, P: 0.006%, Cr: 0.46%, Ni: 2.46%, Mo: 0.58%, with the balance being Fe and unavoidable impurities. The remaining operating steps and parameter settings are the same as in Example 1.

[0033] Comparative Example 4 The difference from Example 1 is that the chemical composition of the welding wire by weight percentage includes: C: 0.094%, Si: 0.82%, Mn: 1.81%, S: 0.003%, P: 0.006%, Cr: 0.50%, Ni: 2.73%, Mo: 0.68%, with the balance being Fe and unavoidable impurities. The remaining operating steps and parameter settings are the same as in Example 1.

[0034] Table 1. Performance test results of weld metals obtained in Examples 1-4 and Comparative Examples 1-4

[0035] As can be seen from the weld metal performance data of Comparative Examples 1-4 in Table 1, the impact toughness decreases significantly with the increase of tensile strength of the weld metal, and cracks appeared in the bending specimen of Comparative Example 4. The impact absorption energy of the weld metal at -50 ℃ in Comparative Examples 1-2 and the tensile strength of the weld metal in Comparative Examples 3-4 meet the impact energy (≥70 J) and tensile strength (≥850 MPa) requirements for welding wires used in heavy equipment in deep sea and polar regions, respectively. However, Comparative Examples 1-4 cannot simultaneously meet both mechanical properties. Compared with Comparative Examples 1-2, the impact absorption energy of the weld metal in Examples 1-4 at -50 ℃ can reach more than 75 J, while simultaneously meeting the performance requirements for welding wires used in heavy equipment in deep sea and polar regions. Examples 1-4, while ensuring tensile strength, also possess good impact toughness. The macroscopic morphology of the specimens after the bending test of the weld metal in Examples 1-4 is as follows. Figure 2As shown, no cracks were found, indicating that the MAG welding wire of the present invention solves the problems of low impact toughness, high sensitivity index of welding liquefaction cracks and embrittlement of welding heat-affected zone under extreme conditions. At the same time, it fills the gap in the matching welding wire for special high-strength steel in the 700~1000 MPa range.

[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A special high-strength steel MAG welding wire for heavy equipment used in deep-sea and polar regions, characterized in that, The chemical composition of this welding wire, by weight percentage, includes: C: 0.02~0.11%, Si: 0.2~1.0%, Mn: 1.0~2.0%, S: ≤0.010%, P: ≤0.010%, Ti: 0.02~0.1%, Cr: 0.2~1.0%, Ni: 2.8~3.5%, Mo: 0.30~1.0%, O: ≤100 ppm, N: ≤100 ppm, with the balance being Fe and unavoidable impurities.

2. The welding wire according to claim 1, characterized in that, The chemical composition of the welding wire by weight percentage includes: C: 0.03~0.10%, Si: 0.2~0.8%, Mn: 1.30~1.80%, S: ≤0.010%, P: ≤0.010%, Ti: 0.02~0.08%, Cr: 0.2~0.60%, Ni: 3.0~3.4%, Mo: 0.30~0.8%, O: ≤80 ppm, N: ≤80 ppm, with the balance being Fe and unavoidable impurities.

3. A method for preparing the welding wire according to claim 1 or 2, characterized in that, The preparation method includes the following steps: S1: The welding wire raw material is successively smelted, electroslag remelted, forged and high-speed hot rolled to obtain wire rod; S2: The wire rod is unloaded, peeled, sanded, and then drawn using a roller die. It is then ultrasonically cleaned, dried, and given a surface anti-rust treatment. Finally, it is wound into a densely packed layer on a spool to obtain the finished welding wire.

4. The preparation method according to claim 3, characterized in that, The diameter of the wire rod in S1 is Ф5.5 mm.

5. The preparation method according to claim 3, characterized in that, The drawing speed of S2 is 200~300 m / min.

6. The preparation method according to claim 3, characterized in that, The diameter of the welding wire in S2 is Ф1.2 mm.

7. The preparation method according to claim 3, characterized in that, The diameter tolerance of the welding wire for S2 is ±0.04 mm.

8. The preparation method according to claim 3, characterized in that, The S2 roller die drawing process involves 14 continuous drawing passes.

9. A welding process for MAG welding of special high-strength steel for heavy equipment in deep sea and polar regions, wherein the welding wire described in claim 1 or 2 is used, and the welding process parameters are as follows: welding current 275 A, welding voltage 30 V, shielding gas is a mixture of 80 vol% Ar and 20 vol% CO2, gas flow rate is 20 L / min, welding speed is 330 cm / min, and interpass temperature is 135~165℃.

10. The weld metal of the welding wire of claim 1 or 2 obtained by the welding process method of claim 9, characterized in that, The tensile strength of the welded metal is ≥850 MPa, the yield strength is ≥800 MPa, and the impact energy at -50℃ is ≥75 J.

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