A surfacing process for marine engineering structures

Abstract

This invention discloses a welding process for marine engineering structural components, comprising the following steps: 1) material preparation; 2) preheating treatment; 3) welding setup; 4) welding; 5) post-weld heat treatment; and 6) quality inspection. Through the above methods, this invention provides a welding process for marine engineering structural components. This process, by optimizing preheating temperature, interpass temperature, welding parameters, and post-weld heat treatment, achieves high-quality welding of high-strength steel, resulting in welded joints with uniform hardness, good mechanical properties, and excellent corrosion resistance. It is suitable for the manufacture and repair of marine engineering structural components.

Description

Technical Field

[0001] This invention relates to the field of welding and repair of marine engineering structural components, and in particular to a welding process for marine engineering structural components. Background Technology

[0002] As an important method for strengthening and repairing material surfaces, surfacing is widely used in the processing of thick-walled components in fields such as shipbuilding, heavy machinery, and pressure vessels. In the field of marine equipment, components not only need to withstand complex marine corrosion environments, but also need to have excellent mechanical properties. Therefore, the stability of the surfacing process and the quality of the joints are required to be extremely high.

[0003] In fields such as marine engineering and shipbuilding, nickel-based alloy solid welding wire is commonly used to weld high-strength steel used in the construction of offshore platforms to improve structural strength and corrosion resistance. However, welding of such dissimilar materials often faces problems such as heat-affected zone hardening, high crack sensitivity, and uneven mechanical properties of welded joints.

[0004] Traditional manual welding processes are inefficient, have poor quality stability, and are difficult to ensure the consistency of key parameters such as interpass temperature and heat input. This results in uneven hardness distribution and insufficient corrosion resistance in welded joints, making them prone to failure under complex working conditions. Summary of the Invention

[0005] The main technical problem solved by this invention is to provide a welding process for marine engineering structural components that can improve the mechanical properties and corrosion resistance of the welded joint.

[0006] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is to provide a welding process for marine engineering structural components, the specific steps of which include: 1) Material preparation: EQ47 high-strength steel plate is selected as the base material, and ERNiCrMo-3 welding wire is selected as the electrode welding wire; 2) Preheating treatment: The welding area on the EQ47 high-strength steel plate in step 1) is preheated by flame preheating. 3) Welding setup: Use DC reverse polarity, connect the ERNiCrMo~3 welding wire to the positive terminal of the power supply output, connect the EQ47 high-strength steel plate to the negative terminal of the power supply, the distance between the contact tip and the workpiece is 30~35mm, and the weld bead is a straight weld bead. 4) Welding: According to the welding settings in step 3), the welding area in step 2) is welded using automatic GMAW welding. The welding is divided into a base layer and multiple layers of weld overlay, and the number of multiple layers of weld overlay is 10. 5) Post-weld heat treatment: After the welding in step 3) is completed, post-weld heat treatment is performed at a temperature of 580℃±10℃ and a holding time of 4 hours. 6) Quality inspection: After the heat treatment in step 5) is completed, inspection shall be carried out to ensure the welding quality.

[0007] In a preferred embodiment of the present invention, the preheating temperature in step 2) is not lower than 117.2°C.

[0008] In a preferred embodiment of the present invention, step 3) involves interlayer cleaning by chiseling, grinding, and using a wire brush to remove welding slag and surface contaminants.

[0009] In a preferred embodiment of the present invention, in step 4), the automatic GMAW welding method uses 99.99% pure argon as the protective gas, the gas flow rate is 18~25L / min, the welding current is 240~260A, the voltage is 27~30V, the welding speed is 20~35cm / min, and the interpass temperature is controlled between 175.7~221.2℃.

[0010] In a preferred embodiment of the present invention, in step 4), the welding current for the underlayer is 250A, the voltage is 30V, and the welding speed is 32.94cm / min. The welding parameters for the first layer of the multilayer weld overlay are the same as those for the underlayer. The welding current for the second to tenth layers of the multilayer weld overlay is 250A, the voltage is 30V, and the welding speed is 19.76~20.74cm / min.

[0011] In a preferred embodiment of the present invention, step 5) post-weld heat treatment is carried out in a resistance furnace, and the heating rate does not exceed 100°C / h.

[0012] In a preferred embodiment of the present invention, hydrogen removal treatment is performed before the post-weld heat treatment in step 5). After the mother part is welded, the mother part is immediately transferred into a heat preservation furnace and kept at a temperature range of 250°C to 300°C for 2 to 4 hours.

[0013] In a preferred embodiment of the present invention, the interlayer temperature is controlled by real-time monitoring with an infrared thermometer and adjusted before each layer is welded.

[0014] The beneficial effects of this invention are: This invention provides a welding process for marine engineering structural components. By optimizing the preheating temperature, interpass temperature, welding parameters, and post-weld heat treatment process, this process achieves high-quality welding of high-strength steel. The welded joint has uniform hardness, good mechanical properties, and excellent corrosion resistance, making it suitable for the manufacture and repair of marine engineering structural components. Detailed Implementation

[0015] The preferred embodiments of the present invention will now be described in detail so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0016] Example 1 A welding process for marine engineering structural components, comprising the following steps: 1) Material preparation: EQ47 high-strength steel plate with dimensions of 300mm×150mm×20mm is selected as the base material, and ERNiCrMo-3 welding wire with a diameter of Φ1.2mm is selected as the electrode welding wire. The EQ47 high-strength steel plate is widely used in marine engineering and shipbuilding. The EQ47 high-strength steel plate can provide structural strength, and the weld overlay made by the ERNiCrMo-3 welding wire can provide excellent resistance to seawater corrosion, pitting corrosion and crevice corrosion. The two complement each other.

[0017] 2) Preheating treatment: The 250mm×100mm welding area on the EQ47 high-strength steel plate in step 1) is preheated by flame preheating, and the preheating temperature is not lower than 120℃.

[0018] 3) Welding setup: DC reverse polarity is used. The ERNiCrMo~3 welding wire is connected to the positive terminal of the power supply output, and the EQ47 high-strength steel plate is connected to the negative terminal of the power supply. The distance between the contact tip and the workpiece is 33mm. The weld bead is a straight weld bead. Interlayer cleaning is performed by chiseling, grinding and using a wire brush to remove welding slag and surface contaminants.

[0019] 4) Welding: According to the welding settings in step 3), the welding area in step 2) is welded using automatic GMAW welding. The welding is divided into a base layer and multiple layers of weld overlay, and the number of multiple layers of weld overlay is 10.

[0020] Argon gas with a purity of 99.99% is used as the protective gas at a flow rate of 20 L / min. The welding current is 240-260 A, the voltage is 27-30 V, and the welding speed is 20-35 cm / min. The interpass temperature is controlled between 185-195 °C. The interpass temperature is monitored in real time by an infrared thermometer and adjusted before each layer is welded. The infrared thermometer monitors the temperature of the weld area in real time. This monitoring method has the advantages of being non-contact and having a fast response, and can accurately reflect the instantaneous temperature of the weld. Before each new weld layer is started, the operator or the automatic control system will fine-tune the temperature by adjusting the preheating device or the forced cooling device based on the feedback from the infrared thermometer. This method completely avoids problems such as deterioration of the weld microstructure, uneven mechanical properties, or decreased corrosion resistance caused by temperature runaway, and is the key to achieving high-performance and high-reproducibility surfacing welding.

[0021] The welding current for the root pass is 250A, the voltage is 30V, and the welding speed is 32.94cm / min. The welding parameters for the first layer of the multi-layer weld overlay are the same as those for the root pass. The welding current for the second to tenth layers of the multi-layer weld overlay is 250A, the voltage is 30V, and the welding speed is 20~20.5cm / min.

[0022] 5) Post-weld heat treatment: After the welding in step 3) is completed, post-weld heat treatment is performed at a temperature of 580℃ and a holding time of 4 hours. The post-weld heat treatment is carried out in an electric resistance furnace with a heating rate not exceeding 100℃ / h.

[0023] Before the post-weld heat treatment in step 5), hydrogen removal treatment is performed. After the mother part is welded, it is immediately transferred into a heat preservation furnace and heated to 280°C at a rate of ≤80°C / h, and kept at that temperature for 3 hours.

[0024] Since the base material is the aforementioned EQ47 high-strength steel plate, its weld heat-affected zone is prone to forming a hardened structure sensitive to hydrogen embrittlement under rapid cooling. At the same time, the weld metal is a nickel-based alloy, which also has a tendency for hydrogen embrittlement. If diffusible hydrogen introduced by the arc atmosphere or moisture on the surface of the welding wire remains in the joint, it is very easy to cause hydrogen-induced delayed cracking under the combined action of residual stress, which seriously threatens the long-term safety of marine structural components. Therefore, this invention performs hydrogen removal treatment at 250°C~300°C for 2 to 4 hours immediately after welding. The purpose is to allow diffusible hydrogen sufficient time to escape from the joint, thereby fundamentally eliminating the risk of hydrogen-induced cracking before the subsequent 580°C post-weld heat treatment.

[0025] 6) Quality inspection: After the heat treatment in step 5) is completed, inspection shall be carried out to ensure the welding quality.

[0026] In Example 2, during the welding process, the interpass temperature was strictly controlled within a narrow range of 185~195℃ by using an additional circulating air cooling device, while all other steps and parameters remained unchanged from Example 1.

[0027] In the comparative example, no hydrogen removal process was performed during the welding process, and all other steps and parameters remained unchanged from Example 1.

[0028] Performance Parameter Comparison Table As can be seen from the performance parameter comparison table, Example 1 can obtain a welded joint with excellent comprehensive performance. Example 2 proves that by further precisely controlling the interpass temperature, the microstructure can be optimized on the basis of being qualified. The comparative example strongly proves that hydrogen removal treatment is a necessary step to prevent hydrogen-induced cracking in high-strength steel nickel-based weld overlay and to ensure the long-term safety and reliability of the joint. The stability and reproducibility of the entire process under automation are far superior to traditional manual welding.

[0029] Compared with existing technologies, the present invention provides a welding process for marine engineering structural components. This process achieves high-quality welding of high-strength steel by optimizing preheating temperature, interpass temperature, welding parameters and post-weld heat treatment. The welded joint has uniform hardness, good mechanical properties and excellent corrosion resistance, and is suitable for the manufacturing and repair of marine engineering structural components.

[0030] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A welding process for marine engineering structural components, characterized in that, The specific steps include: 1) Material preparation: EQ47 high-strength steel plate is selected as the base material, and ERNiCrMo-3 welding wire is selected as the electrode welding wire; 2) Preheating treatment: The welding area on the EQ47 high-strength steel plate in step 1) is preheated by flame preheating, and the preheating temperature is not lower than 117.2℃; 3) Welding setup: Use DC reverse polarity, connect the ERNiCrMo~3 welding wire to the positive terminal of the power supply output, connect the EQ47 high-strength steel plate to the negative terminal of the power supply, the distance between the contact tip and the workpiece is 30~35mm, and the weld bead is a straight weld bead. 4) Welding: According to the welding settings in step 3), the welding area in step 2) is welded using automatic GMAW welding. The welding is divided into a base layer and multiple layers of weld overlay, and the number of multiple layers of weld overlay is 10. The automatic GMAW welding method uses 99.99% pure argon as the protective gas, with a gas flow rate of 18-25 L / min, a welding current of 240-260 A, a voltage of 27-30 V, a welding speed of 20-35 cm / min, and an interpass temperature controlled between 175.7-221.2℃. The welding current for the root pass is 250A, the voltage is 30V, and the welding speed is 32.94cm / min. The welding parameters for the first layer of the multi-layer weld overlay are the same as those for the root pass. The welding current for the second to tenth layers of the multi-layer weld overlay is 250A, the voltage is 30V, and the welding speed is 19.76 to 20.74cm / min. 5) Post-weld heat treatment: After the welding in step 3) is completed, post-weld heat treatment is performed at a temperature of 580℃±10℃ and a holding time of 4 hours. Hydrogen removal treatment is performed before post-weld heat treatment. After the base material is welded, the base material is immediately transferred into a holding furnace and held at a temperature range of 250°C to 300°C for 2 to 4 hours. 6) Quality inspection: After the heat treatment in step 5) is completed, inspection shall be carried out to ensure the welding quality.

2. The welding process for marine engineering structural components according to claim 1, characterized in that, In step 3), interlayer cleaning is performed by chiseling, grinding, and using a wire brush to remove welding slag and surface contaminants.

3. The welding process for marine engineering structural components according to claim 1, characterized in that, Step 5) Post-weld heat treatment is carried out in a resistance furnace, with a heating rate not exceeding 100℃ / h.

4. The welding process for marine engineering structural components according to claim 2, characterized in that, The interlayer temperature is controlled by real-time monitoring with an infrared thermometer and adjusted before each layer is welded.

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