Welding method of seawater corrosion resistant steel 10CrMoAl

Abstract

This invention discloses a welding method for seawater corrosion resistant steel 10CrMoAl, comprising the following steps: S1, machining the welding end of the steel plate to be welded into an X-shaped bevel; S2, performing the root pass welding using gas shielded welding; S3, performing the fill and cover pass welding using a composite process of double-wire submerged arc welding + cold filler wire welding; the welding wire composition used in the double-wire submerged arc welding includes, by weight percentage: C≤0.10%, Cr: 0.8-1.2%, Mo: 0.20-0.35%, Ti: 0.01-0.03%, Nb: 0.01-0.03%, Si: 0.20-0.45%, Mn: 0.6-0.9%, P≤0.012%, S≤0.010%, with the balance being Fe and unavoidable impurities; the cold filler wire composition used in the cold filler wire welding is based on the above submerged arc welding wire composition with an additional 0.03-0.05% Al added. This invention aims to provide a welding technology solution for 10CrMoAl seawater corrosion resistant steel that features "high corrosion resistance, low cracking, low heat input, and high-efficiency welding," supporting its long-term safe application in marine engineering and solving the problem of low welding efficiency of 10CrMoAl steel in the past.

Description

Technical Field

[0001] This application relates to the field of steel welding technology, and in particular to a welding method for seawater corrosion resistant steel 10CrMoAl. Background Technology

[0002] With the rapid development of the global marine economy, the demand for high-performance seawater corrosion-resistant materials is becoming increasingly urgent in fields such as marine resource development, coastal nuclear / thermal power plant construction, large shipbuilding, and deep-sea equipment. Seawater, as a strong electrolyte environment, contains a large amount of Cl... - SO4 2- Corrosive ions such as Cr and Mo2O3 can easily cause pitting, crevice corrosion, and uniform corrosion in seawater, leading to structural failure. 10CrMoAl steel, a typical low-alloy steel resistant to seawater corrosion, contains alloying elements such as Cr (0.8%~1.2%), Mo (0.2%~0.35%), and Al (0.4%~0.8%). It forms a dense Cr2O3 oxide film, inhibiting the corrosion of Cl-. - The penetration and passivation effects of Al result in excellent corrosion resistance in marine environments, especially in environments containing Cl. - Its corrosion resistance in seawater is significantly superior to that of ordinary Q235 and Q345 steel. It has been widely used in key components such as offshore platform jackets, ship cargo holds / seawater pipelines, condenser tube bundle support structures in coastal power plants, and seawater desalination equipment frames.

[0003] Welding is an indispensable key process in the manufacturing and installation of 10CrMoAl steel structures, and its welding quality directly affects the structure's load-bearing capacity, corrosion resistance, and safety. Currently, welding of 10CrMoAl steel structures generally adopts Cr-Mo series welding materials and conventional processes. Among them, the Cr-Mo series welding materials mainly use Cr-Mo series low alloy steel welding rods such as E5515-B3 and E6015-B3 or gas shielded welding wires such as ER55-B3; the welding process generally adopts manual arc welding or CO2 gas shielded welding, and a preheating process is used before welding, with a preheating temperature of 100~150℃, or a post-weld heat treatment of 200~250℃*(2~4)h.

[0004] Due to the influence of the composition and microstructure of 10CrMoAl steel and the welding thermal cycle, the existing welding process has the following shortcomings: 1) Poor compatibility of welding materials: The corrosion resistance of 10CrMoAl steel relies on the surface Cr2O3 oxide film and the auxiliary passivation effect of Al (Al can promote the formation of a dense oxide film and inhibit Cl). - (Penetration), existing welding processes and welding material designs are not coordinated and matched to the "Al passivation film protection mechanism" of 10CrMoAl steel, resulting in poor Cl resistance of the weld. -1) Insufficient corrosion resistance, leading to a risk of deterioration in the seawater corrosion resistance of welded joints. 2) Inadequate process parameter control: Existing welding processes do not optimize heat input for the alloy characteristics of 10CrMoAl steel. Excessive heat input can lead to the formation of coarse overheated structures in the coarse-grained zone of the heat-affected zone, significantly reducing its impact toughness and making it a "weak link" in the joint, thus reducing the overall safety and reliability of the component. 3) High sensitivity to welding cracks: The high alloy characteristics of 10CrMoAl steel, with a high carbon equivalent (CEV≈0.46%~0.55%) and the presence of elements such as Al, Cr, and Mo, make it prone to forming martensitic structures in the HAZ during welding, resulting in high sensitivity to cold cracks. Existing welding processes use preheating or post-weld heat treatment to control the generation of welding cold cracks. If the preheating / post-heating regime is not properly controlled, cracks are very likely to occur during welding, and the preheating / post-heating process increases the welding process cost and worsens the welding construction conditions. 4) Low welding efficiency: Shielded metal arc welding and gas shielded welding are the mainstream welding methods for 10CrMoAl steel, but their welding efficiency is limited by process characteristics and material requirements, resulting in long welding cycles and low efficiency. Summary of the Invention

[0005] The purpose of this application is to address the aforementioned pain points and shortcomings by proposing a welding method based on "composition synergistic design - low crack sensitivity - precise heat input control". Through synergistic design of weld metal composition and precise control of welding process parameters, the weld metal and 1CrMoAl steel achieve a synergistic match in strength, toughness, and corrosion resistance. By employing a combination of ER50-6 gas shielded welding for the root pass and double-wire submerged arc welding + cold filler wire, and through a process route of "crack-resistant root pass + high-efficiency filler wire", the comprehensive performance of 10CrMoAl steel welding, characterized by "low crack and high efficiency", is improved, providing key technical support for the application of 10CrMoAl steel in harsh marine environments.

[0006] To achieve the above objectives, the application adopts the following technical solution:

[0007] A welding method for seawater corrosion resistant steel 10CrMoAl includes the following steps:

[0008] S1. Process the weldable area of ​​the steel plate to be welded into an X-shaped bevel;

[0009] S2. CO2 gas shielded welding is used for the root pass of the weld.

[0010] S3. A composite process of double-wire submerged arc welding + cold filler wire is used for filling and cover welding;

[0011] The welding wire used in the dual-wire submerged arc welding comprises, by weight percentage: C≤0.10%, Cr: 0.8-1.2%, Mo: 0.20-0.35%, Ti: 0.01-0.03%, Nb: 0.01-0.03%, Si: 0.20-0.45%, Mn: 0.6-0.9%, P≤0.012%, S≤0.010%, with the balance being Fe and unavoidable impurities;

[0012] The cold filler wire components comprise, by weight percentage: C ≤ 0.10%, Cr: 0.8-1.2%, Mo: 0.20-0.35%, Si: 0.20-0.45%, Mn: 0.6-0.9%, P ≤ 0.012%, S ≤ 0.010%, Al: 0.03-0.05%, with the balance being Fe and unavoidable impurities.

[0013] Furthermore, the angle of the X-shaped bevel is 70°±5°.

[0014] Furthermore, in step S1, after processing the end of the steel plate to be welded into an X-shaped bevel, the step also includes pre-treatment of the X-shaped bevel, which includes grinding and cleaning the X-shaped bevel and its two sides until the metal luster is exposed.

[0015] Furthermore, in S2, the welding wire used for the root pass is ER50-6.

[0016] Furthermore, the diameter of the submerged arc welding main wire is Ф3.2mm.

[0017] Furthermore, the process parameters for the dual-wire submerged arc welding include: the main wire welding current is 650A-850A, the arc voltage is 30-32V, the rear wire welding current is 500-600A, the arc voltage is 40-41V, the welding speed is 145-165 cm / min, and the welding heat input is ≤19kJ / cm.

[0018] Furthermore, the Cr, Mo, and Al elemental composition in the weld metal of the weld joint is as follows by weight percentage: Cr: 0.8-1.2%, Mo: 0.20-0.35%, Al: 0.18-0.25%.

[0019] The beneficial effects of this application are:

[0020] 1) As the "outer barrier" of the welded joint, the quality of the capping weld directly affects the corrosion resistance and service life of the structure. This application proposes a combined process of double wire and cold filler wire. By controlling the Cr and Mo content in the composition of the double wire submerged arc welding wire and the Al content in the composition of the cold wire, and in conjunction with the welding process and groove design, the Cr and Mo content in the weld metal is made comparable to the Cr and Mo content in the base metal 10CrMoAl corrosion-resistant steel. The weld metal and the base metal form a homologous passivation film. The cold wire is not heated by the electric arc, but melted by the residual heat of the molten pool. The Al element is directly transferred to the molten pool, which promotes the formation of Al2O3 passivation film, enhances the continuity of the Al2O3 film on the joint surface, and achieves the seawater corrosion resistance of the capping weld metal comparable to that of the base metal 10CrMoAl steel.

[0021] 2) As a seawater corrosion resistant steel, the core welding requirements for 10CrMoAl steel are "high corrosion resistance, low crack sensitivity, and matching mechanical properties". This application uses a combination of ER50-6 welding wire, CO2 gas shielded welding for the root pass, and double-wire submerged arc welding + cold filler wire to systematically meet these requirements. According to the results of GB / T32260.2-2015 "Crack Test of Oblique Y-groove Welding", using ER50-6 welding wire and CO2 gas shielded welding without preheating, 10CrMoAl steel exhibits zero cold cracking and delayed cracking rates under harsh constraint conditions (such as tack welding, butt weld root passes, etc.), significantly reducing welding crack sensitivity and meeting the safe welding requirements for thick plates under high constraint conditions. During filler and cap welds, the composite process of double-wire submerged arc welding + cold filler wire is used. The cold wire melts into the molten pool, generating a stirring effect that promotes hydrogen gas escape, further reducing the risk of delayed cracking.

[0022] 3) The heat-affected zone of 10CrMoAl steel is sensitive to heat input. Excessive heat input can easily generate coarse ferrite bands, reducing toughness. This application adopts a composite process of double-wire submerged arc welding and cold filler wire welding. During welding, the cold wire does not pass through current and melts only by the heat of the molten pool, avoiding additional arc heating and reducing the overall heat input. The line energy can be reduced to 12-19 kJ / cm, thereby effectively reducing the degree of grain coarsening in the heat-affected zone. At the same time, when the cold wire melts into the molten pool, it can also form a "stirring effect", promoting the flow of the molten pool and further refining the weld grains, thereby improving the impact performance of the weld and the heat-affected zone.

[0023] 4) This application uses a composite process of double-wire submerged arc welding and cold filler wire welding for filling and cover welding, which can achieve a weld deposition rate of 8~15 kg / h. Compared with single-wire submerged arc welding, the welding speed is increased by 30%~50%. At the same time, it can reduce the time for interlayer slag removal and positioning, improve deposition efficiency, and shorten the welding cycle. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. In the description of this application, the experimental methods, unless otherwise specified, are conventional methods; the reagents and materials, unless otherwise specified, are all commercially available.

[0025] The following disclosure provides many different implementations or examples for carrying out this application. To simplify the disclosure of this application, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0026] Example 1

[0027] A welding method for butt welding of 10CrMoAl steel with a thickness of 10mm includes the following steps:

[0028] S1. Process the end of the steel plate to be welded into a symmetrical 75° X-shaped bevel. Before welding, grind and clean the surface oil and rust within 50mm on both sides of the X-shaped bevel until the metal luster is exposed.

[0029] S2. CO2 gas shielded welding is used for the root pass welding. The welding wire used is ER50-6, and the width of the root pass weld is 3-4mm.

[0030] S3. A composite process of double-wire submerged arc welding and cold filler wire welding is used for filling and cover welding;

[0031] The welding wire used in the dual-wire submerged arc welding has a diameter of Ф3.2mm and its composition by weight percentage is: C: 0.07%, Cr: 1.10%, Mo: 0.24%, Ti: 0.015%, Nb: 0.011%, Si: 0.38%, Mn: 0.67%, P: 0.011%, S: 0.002%, with the balance being Fe and unavoidable impurities;

[0032] The submerged arc welding used in the dual-wire submerged arc welding is SJ101 flux. The welding current of the first wire is 650A and the arc voltage is 32. The welding current of the subsequent wire is 500A and the arc voltage is 40V. The welding speed is 145cm / min and the heat input is 16.3kJ / cm.

[0033] The components of the cold filler wire are as follows by weight percentage: C: 0.64%, Cr: 1.10%, Mo: 0.24%, Ti: 0.015%, Nb: 0.011%, Si: 0.38%, Mn: 0.67%, P: 0.011%, Al: 0.034%, with the balance being Fe and unavoidable impurities.

[0034] Example 2

[0035] A welding method for butt welding of 20mm thick 10CrMoAl steel includes the following steps:

[0036] S1. Process the end of the steel plate to be welded into a symmetrical 65° X-shaped bevel. Before welding, grind and clean the surface oil and rust within 50mm on both sides of the X-shaped bevel until the metal luster is exposed.

[0037] S2. CO2 gas shielded welding is used for the root pass welding. The welding wire used is ER50-6, and the width of the root pass weld is 4-5mm.

[0038] S3. A composite process of double-wire submerged arc welding and cold filler wire welding is used for filling and cover welding;

[0039] The welding wire used in the dual-wire submerged arc welding has a diameter of Ф3.2mm and its composition by weight percentage is: C: 0.09%, Cr: 0.94%, Mo: 0.28%, Ti: 0.025%, Nb: 0.011%, Si: 0.42%, Mn: 0.75%, P: 0.010%, S: 0.005%, with the balance being Fe and unavoidable impurities;

[0040] The submerged arc welding used in the dual-wire submerged arc welding is SJ101 flux. The welding current of the first wire is 850A and the arc voltage is 32. The welding current of the subsequent wire is 600A and the arc voltage is 41V. The welding speed is 165cm / min and the heat input is 18.8kJ / cm.

[0041] The cold wire composition used in the cold filler wire welding is as follows by weight percentage: C: 0.088%, Cr: 0.94%, Mo: 0.32%, Si: 0.42%, Mn: 0.75%, P: 0.010%, S: 0.005%, Al: 0.046%, with the balance being Fe and unavoidable impurities.

[0042] Example 3

[0043] A welding method for butt welding of 10CrMoAl steel with a thickness of 16mm includes the following steps:

[0044] S1. Process the end of the steel plate to be welded into a symmetrical 70° X-shaped bevel. Before welding, grind and clean the surface oil and rust within 50mm on both sides of the X-shaped bevel until the metal luster is exposed.

[0045] S2. CO2 gas shielded welding is used for the root pass welding. The welding wire used is ER50-6, and the width of the root pass weld is 4-5mm.

[0046] S3. A composite process of double-wire submerged arc welding and cold filler wire welding is used for filling and cover welding;

[0047] The welding wire used in the dual-wire submerged arc welding has a diameter of Ф3.2mm and its composition by weight percentage is: C: 0.07%, Cr: 0.82%, Mo: 0.28%, Ti: 0.021%, Nb: 0.015%, Si: 0.22%, Mn: 0.87%, P: 0.010%, S: 0.008%, with the balance being Fe and unavoidable impurities;

[0048] The submerged arc welding used in the dual-wire submerged arc welding is SJ101 flux. The welding current of the first wire is 750A and the arc voltage is 32. The welding current of the subsequent wire is 550A and the arc voltage is 41V. The welding speed is 155cm / min and the heat input is 17.1kJ / cm.

[0049] The cold wire composition used in the cold filler wire welding is as follows by weight percentage: C: 0.074%, Cr: 0.82%, Mo: 0.28%, Si: 0.22%, Mn: 0.87%, P: 0.010%, S: 0.008%, Al: 0.04%, with the balance being Fe and unavoidable impurities.

[0050] Performance testing

[0051] To better verify the welding effects of the above embodiments, the tensile properties, bending properties, impact properties, and corrosion resistance of the welded joints of the above embodiments were tested, and the chemical composition of the weld metal was detected by spectrometry. Tensile properties were tested according to GB / T2651-2008 "Tension Test Method for Welded Joints", bending properties were tested according to GB / T2653-2008 "Bending Test Method for Welded Joints", and impact properties were tested according to GB / T2650-2008 "Impact Test Method for Welded Joints". The corrosion resistance of the weld metal and base metal 10CrMoAl in the above embodiments was tested according to standard GB / T1-125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test". The salt spray corrosion test used neutral salt spray to simulate the salt spray environment of the ocean. The test equipment was a YWX / Q250 salt spray corrosion test chamber. Four parallel samples were used for each test condition. The test parameters were: 5% NaCl solution prepared with deionized water, pH 6.7-7.2, test temperature (35 ± 2)℃, and salt spray deposition rate of 2 mL / (cm²). 2 The test was conducted continuously for 168 hours (·h). After the test, the corrosion rate of the sample after 168 hours of corrosion was calculated by comparing the sample mass before and after corrosion.

[0052] Table 1. Mechanical property test results of welded joints in each embodiment.

[0053]

[0054] Table 2. Salt spray corrosion test results of weld metal and base metal in each embodiment (10CrMoAl).

[0055]

[0056] Table 3 Chemical composition of weld metal in each embodiment (Wt.%)

[0057]

[0058] The test data from Examples 1-3 clearly demonstrate that the combined process of using ER50-6 welding wire gas shielded welding for the root pass, followed by double-wire submerged arc welding and cold filler wire welding for the cover pass, is a systematic solution for welding 10CrMoAl seawater corrosion resistant steel, addressing its requirements for "high corrosion resistance, low crack sensitivity, and matching mechanical properties." This process, through the synergistic implementation of "root pass crack resistance → efficient filler deposition → cover pass composition optimization," solves the core pain points of traditional processes in 10CrMoAl steel welding.

[0059] The above provides a detailed description of a welding method for seawater corrosion resistant steel 10CrMoAl provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A welding method for seawater corrosion-resistant steel 10CrMoAl, characterized in that, Includes the following steps: S1. Process the weldable area of ​​the steel plate to be welded into an X-shaped bevel; S2. CO2 gas shielded welding is used for the root pass of the weld. S3. A composite process of double-wire submerged arc welding + cold filler wire is used for filling and cover welding; The welding wire used in the dual-wire submerged arc welding comprises, by weight percentage: C≤0.10%, Cr: 0.8-1.2%, Mo: 0.20-0.35%, Ti: 0.01-0.03%, Nb: 0.01-0.03%, Si: 0.20-0.45%, Mn: 0.6-0.9%, P≤0.012%, S≤0.010%, with the balance being Fe and unavoidable impurities; The components of the cold filler wire, by weight percentage, include: C≤0.10%, Cr: 0.8-1.2%, Mo: 0.20-0.35%, Si: 0.20-0.45%, Mn: 0.6-0.9%, P≤0.012%, S≤0.010%, Al: 0.03~0.05%, with the balance being Fe and unavoidable impurities.

2. The welding method for seawater corrosion resistant steel 10CrMoAl as described in claim 1, characterized in that: The angle of the X-shaped bevel is 70°±5°.

3. The welding method for seawater corrosion resistant steel 10CrMoAl as described in claim 1, characterized in that: The welding wire used for the root pass welding is ER50-6.

4. The welding method for seawater corrosion resistant steel 10CrMoAl as described in claim 1, characterized in that: The diameter of the submerged arc welding main wire is Ф3.2mm.

5. The welding method for seawater corrosion resistant steel 10CrMoAl as described in claim 1, characterized in that: The process parameters for the dual-wire submerged arc welding include: main wire welding current of 650A-850A, arc voltage of 30-32V, rear wire welding current of 500-600A, arc voltage of 40-41V, welding speed of 145-165 cm / min, and welding heat input ≤19kJ / cm.

6. The welding method for seawater corrosion resistant steel 10CrMoAl as described in claim 1, characterized in that: The Cr, Mo, and Al elemental composition of the weld metal at the weld joint, by weight percentage, is as follows: Cr: 0.8-1.2%, Mo: 0.20-0.35%, Al: 0.18-0.25%.

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