A welding method for a ship-use normalized low-temperature container steel

Abstract

This application discloses a welding method for marine normalized cryogenic vessel steel, belonging to the field of welding technology. The method includes the following steps: machining the weld seam of the steel plate to be welded into a single-sided symmetrical V-groove; pre-treating the steel plate to be welded to remove oil and rust from both sides of the groove; and performing electric vertical welding on the groove. The welding wire used for electric vertical welding, by mass fraction, comprises: C: 0.10%, Si: 0.29%, Mn: 1.83%, P≤0.012%, S≤0.010%, Ni: 1.55%, Cr: 0.03%, Mo: 0.02%. Compared to using welding materials of the same grade as normalized cryogenic steel for marine engineering plates, the welding wire used in this application is relatively inexpensive, significantly reducing welding costs. After welding using this welding wire, the weld joint exhibits an impact toughness ≥60J (standard requirement ≥27J) at -75℃, and a tensile strength not less than the minimum requirement of the base material with the lowest tensile strength, ensuring that the welding quality meets the requirements.

Description

Technical Field

[0001] This application relates to the field of welding technology, and more particularly to a welding method for marine normalized cryogenic vessel steel. Background Technology

[0002] Driven by the "dual carbon" goals and the green transformation of the shipping industry, marine normalized cryogenic container steels (such as NV4-4L, 09MnNiDR, and 08Ni3DR) have broad application prospects. These steels are mainly used in LNG / liquid ammonia fuel tanks, cryogenic liquid cargo tanks, and key structural components of polar vessels. Their high reliability and safety reserves meet the global demand for clean energy and polar navigation.

[0003] With domestic steel companies achieving technological breakthroughs and domestic substitution, normalized low-temperature steel is rapidly expanding from the traditional petrochemical field to high-end shipbuilding and marine engineering equipment. It is expected to maintain a high level of prosperity in the next 5-10 years and become a key material with both strategic value and growth potential in the fields of high-end ship support and low-temperature energy storage and transportation.

[0004] In related technologies, when normalized low-temperature steel is applied to shipbuilding and marine engineering equipment, in order to ensure the impact toughness and tensile strength of the welded joint at low temperatures, it is usually welded with marine engineering plate welding materials of the same grade as the normalized low-temperature steel. Moreover, during the welding process, the filler volume of the weld groove is generally large, requiring multiple welding passes. This results in high welding costs (approximately 17% of shipbuilding costs) and long labor time (up to 40%), which seriously restricts the application of normalized low-temperature steel in shipbuilding and marine engineering equipment. Summary of the Invention

[0005] The purpose of this application is to provide a welding method for marine normalized cryogenic container steel, in order to solve the problem of high welding cost of marine normalized cryogenic steel in related technologies.

[0006] To solve the above-mentioned technical problems, this application adopts the following technical solution:

[0007] This application provides a welding method for marine normalized cryogenic vessel steel, comprising:

[0008] Step 1: Process the weld seam of the steel plate to be welded into a V-shaped bevel with one side symmetry;

[0009] Step 2: Pre-treat the steel plate to be welded to remove oil and rust stains from both sides of the bevel.

[0010] Step 3: Perform electric vertical welding on the bevel, wherein, by mass fraction, the composition of the welding wire used for the electric vertical welding includes: C: 0.10%, Si: 0.29%, Mn: 1.83%, P≤0.012%, S≤0.010%, Ni: 1.55%, Cr: 0.03%, Mo: 0.02%.

[0011] In this scheme, the weld is machined with a symmetrical V-groove on one side, eliminating the need for carbon arc gouging after the root pass. This avoids carburizing of the base material and weld after gouging, which can lead to hardened structures and reduced corrosion resistance. After the beveling is completed, the steel plate to be welded is pretreated to remove oil and rust from both sides of the beveling, ensuring the weld is uncontaminated before welding. After pretreatment, electric vertical welding is used, allowing for one-pass welding, significantly improving production efficiency and reducing time costs. The welding wire used for electric vertical welding, by mass fraction, comprises: C: 0.10%, Si: 0.29%, Mn: 1.83%, P≤0.012%, S≤0.010%, Ni: 1.55%, Cr: 0.03%, Mo: 0.02%. Compared to using welding materials of the same grade as normalized low-temperature steel for marine engineering plates, the welding wire cost in this scheme is relatively low, significantly reducing welding costs. After welding is completed, the welding process ensures that the welded joint has an impact toughness of ≥60J (standard requirement ≥27J) at a temperature of -75℃ and a tensile strength not less than the minimum value required by the standard for the base material with the lowest tensile strength. This welding process ensures that the welding quality meets the requirements.

[0012] Optionally, the thickness H of the steel plate to be welded is 50 mm.

[0013] Optionally, the bevel angle α is 28°-32°.

[0014] Optionally, the initial spacing L of the steel plates to be welded is 4mm-5mm, and the blunt edge size h of the bevel is 2mm-2.5mm.

[0015] Optionally, step two includes: using a grinder to remove oil and rust stains from both sides of the weld.

[0016] Optionally, in step three, the diameter of the welding wire used for the electric vertical welding is 1.6 mm.

[0017] Optionally, step three includes: forming the material in one pass using high heat input electrical vertical welding.

[0018] Optionally, in step three, the welding current is 380A-420A, the arc voltage is 40V-44V, and the welding speed is 32mm / min-34mm / min.

[0019] Compared with existing technologies, the beneficial effects achieved by this application are as follows: After welding, the welded joint exhibits an impact toughness ≥60J (standard requirement ≥27J) at -75℃, and its tensile strength is not less than the minimum requirement of the base material with the lowest tensile strength, ensuring that the welding quality meets the requirements. While ensuring welding quality, the welding wire used in this application is several times cheaper than the welding materials for marine engineering plates of the same grade as normalized low-temperature steel, significantly reducing welding costs. Secondly, the V-groove filler material used in this application has a lower filler content, further reducing welding costs. Furthermore, this application employs gas-electric vertical welding, allowing for one-pass welding, greatly improving production efficiency and reducing time costs. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments or related technologies of this disclosure, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the bevel structure of some embodiments provided in this application, wherein H is the thickness of the steel plate to be welded; α is the angle of the bevel; L is the initial spacing of the steel plates to be welded; and h is the blunt edge dimension of the bevel. Detailed Implementation

[0022] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure / application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its application or use.

[0023] This application discloses a welding method for marine normalized cryogenic vessel steel, which includes the following steps:

[0024] Step 1: Process the weld seam of the steel plate to be welded into a V-shaped bevel with one side symmetry.

[0025] refer to Figure 1 The weld of the steel plate to be welded in this application is a single-sided symmetrical V-shaped groove, which eliminates the need for carbon arc gouging after the root pass, thus avoiding carburization of the base material and weld after gouging, which would lead to hardened structure and reduced corrosion resistance.

[0026] In this application, the bevel angle α is 28°-32°, the initial spacing L of the steel plates to be welded is 4mm-5mm, and the blunt edge dimension h of the bevel is 2mm-2.5mm. In some specific embodiments, the bevel angle can be 28°, 29°, 30°, 31°, and 32°, etc.; the initial spacing of the steel plates to be welded can be 4mm, 4.5mm, and 5mm, etc.; and the blunt edge dimension of the bevel can be 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, and 2.5mm, etc. The V-groove weld filler material used in this application is relatively low, further reducing welding costs.

[0027] Step two: Pre-treat the steel plate to be welded to remove oil and rust stains from both sides of the bevel.

[0028] After the beveling is completed, the steel plate to be welded is pretreated to remove oil and rust from both sides of the beveling, ensuring that the weld is free of contamination before welding. In some embodiments, a grinder can be used to remove oil and rust from both sides of the weld.

[0029] Step 3: Perform electric vertical welding on the bevel. The welding wire used for electric vertical welding, by mass fraction, comprises: C: 0.10%, Si: 0.29%, Mn: 1.83%, P≤0.012%, S≤0.010%, Ni: 1.55%, Cr: 0.03%, Mo: 0.02%.

[0030] In some embodiments, after pretreatment, high-heat-input electric vertical welding is used to form the weld in one pass. The welding current is 380A-420A, the arc voltage is 40V-44V, and the welding speed is 32mm / min-34mm / min. In some specific embodiments, the welding current can be 380A, 380A, 390A, 400A, 410A, and 420A, etc.; the arc voltage can be 40V, 41V, 42V, 43V, and 44V, etc.; and the welding speed can be 32mm / min, 33mm / min, and 34mm / min, etc. Electric vertical welding can greatly improve production efficiency, forming the weld in one pass and reducing time costs. Furthermore, compared to using welding materials of the same grade as normalized low-temperature steel for marine engineering plates, the welding wire of this application is relatively inexpensive, significantly reducing welding costs.

[0031] The welding method of the present invention will be described below with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0032] Example 1

[0033] In this embodiment, the steel plate to be welded is a 50mm thick NV4-4L steel plate. Its composition by mass fraction includes: C: 0.90%, Mn: 1.65%, Ni: 0.50%, Nb: 0.004%, Ti: 0.004%, Al: 0.016%, Cr: 0.020%, Cu: 0.006%, Si: 0.20%, P: 0.008%, S: 0.004%, with the balance being Fe and other unavoidable impurities. The mechanical properties of the above-mentioned NV4-4L steel plate are: tensile strength of 540MPa, yield strength of 410MPa, elongation of 30%, and impact energy Akv at -75℃ of 215J, 221J, and 213J, respectively.

[0034] The weld seam of the aforementioned NV4-4L steel plate is machined into a single-sided symmetrical V-shaped bevel. The bevel angle is 30°, the initial distance between the two NV4-4L steel plates is 4mm, and the blunt edge dimension of the bevel is 2mm.

[0035] Pre-treat the steel plate to be welded to remove oil and rust stains from both sides of the bevel.

[0036] The bevel was formed in one pass using high-heat-input electric vertical welding. The welding current was 400A, the arc voltage was 42A, and the welding speed was 33mm / min. The welding wire used for the electric vertical welding had a diameter of 16mm and its composition by mass fraction included: C: 0.10%, Si: 0.29%, Mn: 1.83%, P≤0.012%, S≤0.010%, Ni: 1.55%, Cr: 0.03%, Mo: 0.02%. This welding wire exhibits an impact energy of up to 80J at a low temperature of -75℃ and excellent low-temperature toughness.

[0037] Microstructure and mechanical properties analysis of the welded metal in this embodiment: The weld metal microstructure is pearlite + ferrite. Testing revealed no solidification cracks or reheat cracks. The mechanical properties of the welded metal are as follows.

[0038]

[0039] The results show that after welding using the welding method of this embodiment, the mechanical properties of the weld and its surrounding area fully meet the performance requirements of the ship plate inspection, and the mechanical properties of the welded joint after welding also meet the performance requirements of welding marine normalized low temperature container steel.

[0040] Example 2

[0041] In this embodiment, the steel plate to be welded is a 50mm thick NV4-4L steel plate. Its composition by mass fraction includes: C: 0.90%, Mn: 1.65%, Ni: 0.50%, Nb: 0.004%, Ti: 0.004%, Al: 0.016%, Cr: 0.020%, Cu: 0.006%, Si: 0.20%, P: 0.008%, S: 0.004%, with the balance being Fe and other unavoidable impurities. The mechanical properties of the above-mentioned NV4-4L steel plate are: tensile strength of 540MPa, yield strength of 410MPa, elongation of 30%, and impact energy Akv at -75℃ of 215J, 221J, and 213J, respectively.

[0042] The weld seam of the aforementioned NV4-4L steel plate is machined into a single-sided symmetrical V-shaped bevel. The bevel angle is 30°, the initial distance between the two NV4-4L steel plates is 4mm, and the blunt edge dimension of the bevel is 2mm.

[0043] Pre-treat the steel plate to be welded to remove oil and rust stains from both sides of the bevel.

[0044] The beveling was completed in one pass using high-heat-input electric vertical welding. The welding current was 380A, the arc voltage was 42A, and the welding speed was 33mm / min. The welding wire used for the electric vertical welding had a diameter of 16mm and its composition by mass fraction included: C: 0.10%, Si: 0.29%, Mn: 1.83%, P≤0.012%, S≤0.010%, Ni: 1.55%, Cr: 0.03%, Mo: 0.02%. This welding wire exhibits an impact energy of up to 80J at a low temperature of -75℃ and demonstrates excellent low-temperature toughness.

[0045] Microstructure and mechanical properties analysis of the welded metal in this embodiment: The weld metal microstructure is pearlite + ferrite. Testing revealed no solidification cracks or reheat cracks. The mechanical properties of the welded metal are as follows.

[0046]

[0047] The results show that after welding using the welding method of this embodiment, the mechanical properties of the weld and its surrounding area fully meet the performance requirements of the ship plate inspection, and the mechanical properties of the welded joint after welding also meet the performance requirements of welding marine normalized low temperature container steel.

[0048] Example 3

[0049] In this embodiment, the steel plate to be welded is a 50mm thick NV4-4L steel plate. Its composition by mass fraction includes: C: 0.90%, Mn: 1.65%, Ni: 0.50%, Nb: 0.004%, Ti: 0.004%, Al: 0.016%, Cr: 0.020%, Cu: 0.006%, Si: 0.20%, P: 0.008%, S: 0.004%, with the balance being Fe and other unavoidable impurities. The mechanical properties of the above-mentioned NV4-4L steel plate are: tensile strength of 540MPa, yield strength of 410MPa, elongation of 30%, and impact energy Akv at -75℃ of 215J, 221J, and 213J, respectively.

[0050] The weld seam of the aforementioned NV4-4L steel plate is machined into a single-sided symmetrical V-shaped bevel. The bevel angle is 30°, the initial distance between the two NV4-4L steel plates is 4mm, and the blunt edge dimension of the bevel is 2mm.

[0051] Pre-treat the steel plate to be welded to remove oil and rust stains from both sides of the bevel.

[0052] The beveling was completed in one pass using high-heat-input electric vertical welding. The welding current was 420A, the arc voltage was 42A, and the welding speed was 33mm / min. The welding wire used for the electric vertical welding had a diameter of 16mm and its composition by mass fraction included: C: 0.10%, Si: 0.29%, Mn: 1.83%, P≤0.012%, S≤0.010%, Ni: 1.55%, Cr: 0.03%, Mo: 0.02%. This welding wire exhibits an impact energy of up to 80J at a low temperature of -75℃ and demonstrates excellent low-temperature toughness.

[0053]

[0054] Microstructure and mechanical properties analysis of the welded metal in this embodiment: The weld metal microstructure is pearlite + ferrite. Testing revealed no solidification cracks or reheat cracks. The mechanical properties of the welded metal are as follows.

[0055] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this disclosure / application, and these improvements and modifications should also be considered within the protection scope of this disclosure / application.

Claims

1. A welding method for marine normalized cryogenic vessel steel, characterized in that, include: Step 1: Process the weld seam of the steel plate to be welded into a V-shaped bevel with one side symmetry; Step 2: Pre-treat the steel plate to be welded to remove oil and rust stains from both sides of the bevel. Step 3: Perform electric vertical welding on the bevel, wherein, by mass fraction, the composition of the welding wire used for the electric vertical welding includes: C: 0.10%, Si: 0.29%, Mn: 1.83%, P≤0.012%, S≤0.010%, Ni: 1.55%, Cr: 0.03%, Mo: 0.02%.

2. The welding method for marine normalized cryogenic vessel steel according to claim 1, characterized in that, The thickness H of the steel plate to be welded is 50mm.

3. The welding method for marine normalized cryogenic vessel steel according to claim 2, characterized in that, The bevel angle α is 28°-32°.

4. The welding method for marine normalized cryogenic vessel steel according to claim 3, characterized in that, The initial spacing L of the steel plates to be welded is 4mm-5mm, and the blunt edge size h of the bevel is 2mm-2.5mm.

5. The welding method for marine normalized cryogenic vessel steel according to claim 1, characterized in that, Step two includes: using a grinder to remove oil and rust stains from both sides of the weld.

6. The welding method for marine normalized cryogenic vessel steel according to claim 1, characterized in that, In step three, the diameter of the welding wire used for the electric vertical welding is 1.6 mm.

7. The welding method for marine normalized cryogenic vessel steel according to claim 1, characterized in that, Step three includes: using high heat input electrical vertical welding to form a single shape.

8. The welding method for marine normalized cryogenic vessel steel according to claim 7, characterized in that, In step three, the welding current is 380A-420A, the arc voltage is 40V-44V, and the welding speed is 32mm / min-34mm / min.

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