Copper-based corrosion-resistant flux-cored welding wire and surface strengthening method for DH36 steel welded joints

Abstract

The present invention discloses a copper-based, corrosion-resistant flux-cored welding wire, comprising a flux core and a wire sheath. The flux core is composed of the following components by mass percentage: 10-15% Ni powder; 0.1-0.5% Si powder; 10-15% Cr powder; 0-5% Ti powder; 2-3% Nb powder; 2% W powder; and the remainder Cu powder, the sum of the mass percentages of the above components being 100%. A method for surface strengthening a DH36 steel welded joint using the flux-cored welding wire is also provided. By utilizing the flux-cored welding wire and designing a multi-layer, multi-pass welding cladding process based on arc cladding technology, combined with secondary air-run cladding heating, a cladding layer is prepared on the surface of the DH36 steel welded joint, improving the original welding process. The improved cladding layer is tightly bonded to the joint steel substrate, free of cracks and pores, forming a dense protective layer that prevents further corrosion and thus increases the corrosion resistance of the joint.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface modification of metal materials, and in particular relates to a copper-based corrosion-resistant flux-cored welding wire. The present invention also relates to a method for surface strengthening a DH36 steel welded joint by using the welding wire based on arc cladding technology. Background Art

[0002] As offshore oil projects move towards deepwater, large-scale marine steel structures are increasing in number. The welding of thick steel structures has become a research focus. DH36 steel is a low-alloy, high-strength marine steel. Based on low-carbon steel, it incorporates various alloying elements, such as niobium, manganese, nickel, and titanium, to improve the steel's low-temperature impact toughness and strength. Its advantages include high fatigue strength, low carbon equivalent, excellent weldability, and good formability. It has become the mainstream material of choice for welding thick steel structures and is widely used in modern ships and marine engineering. However, on steel structures made primarily of DH36 steel, rust often forms on the welds of the hull due to continuous seawater immersion and infusion. Over time, this can cause corrosion at the welds and damage the welded structure. Since welded structures are often critical load-bearing structures, weld corrosion can ultimately lead to the failure of the entire equipment. If weld corrosion is not discovered promptly and appropriate repair measures are not taken, it can easily lead to structural and equipment failure, and even explosions and leaks, posing a significant threat to the safety of people and property. Addressing the corrosion problem of marine steel weld joints is urgent.

[0003] Flux-cored welding wire, as a welding material, offers flexibility, allowing for different effects to be achieved by adding different elements to the flux core. However, there is currently no corrosion-resistant welding wire that is perfectly compatible with DH36 marine steel. Therefore, improvements are urgently needed in welding materials and surface treatment methods for marine steel welding to enhance its corrosion resistance and, therefore, extend the service life of the vessel. Summary of the Invention

[0004] The purpose of the present invention is to provide a copper-based corrosion-resistant flux-cored welding wire that can effectively combine with the weld joint of marine steel DH36 to form a dense protective layer, thereby preventing further development of corrosion in a seawater environment, solving the problem of low corrosion resistance of the weld joint of marine steel DH36, and thus greatly improving the service life of marine steel DH36 in marine engineering.

[0005] Another object of the present invention is to provide a method for surface strengthening of DH36 steel welded joints using the welding wire based on arc cladding technology.

[0006] The technical solution adopted by the present invention is that the copper-based corrosion-resistant flux-cored welding wire includes a flux core and a welding wire sheath, and the flux core is composed of the following components by mass percentage: Ni powder: 10-15%; Si powder: 0.1-0.5%; Cr powder: 10-15%; Ti powder: 0-5%; Nb powder: 2-3%; W powder: 2%; the rest is Cu powder, and the sum of the mass percentages of the above components is 100%.

[0007] The present invention is also characterized in that:

[0008] The outer sheath of the welding wire is a T2 pure copper strip, and the filling rate of the flux core powder in the flux cored welding wire is 22wt.%-28wt.%.

[0009] The diameter of the flux-cored wire is 1.6 mm.

[0010] Another technical solution adopted by the present invention is a method for surface strengthening of DH36 steel welded joints using the above-mentioned copper-based flux-cored corrosion-resistant welding wire, which is specifically carried out in the following steps:

[0011] Step 1: Weigh the following metal powders by mass percentage: Ni powder: 10-15%; Si powder: 0.1-0.5%; Cr powder: 10-15%; Ti powder: 0-5%; Nb powder: 2-3%; W powder: 2%; the rest is Cu powder, and the sum of the mass percentages of the above components is 100%;

[0012] Step 2: The metal powder weighed in step 1 is mixed evenly to form a flux core, and a pure copper strip is used as the welding wire sheath. The flux-cored welding wire is made by a wire drawing machine, and the prepared flux-cored welding wire is stored in a constant temperature box for use;

[0013] Step 3: Use an angle grinder to clean the surface of the DH36 steel weld joint to remove surface oil and oxide scale, and then preheat the DH36 steel weld joint;

[0014] Step 4: Using the flux-cored wire prepared in step 2, a multi-layer and multi-pass welding cladding process is designed based on the MIG welding cladding method to prepare a cladding layer on the surface of the preheated DH36 steel weld joint;

[0015] Step 5: The cladding layer to be prepared is cooled to room temperature, and its surface is cleaned by mechanical grinding. Then, the cladding layer is heated by TIG welding along the weld bead of step 4 without feeding the welding wire;

[0016] Step 6: After cooling to room temperature again, use mechanical cleaning to polish the surface of the cladding layer to meet the use requirements of the workpiece.

[0017] In step 2, the flux-cored welding wire is prepared by mechanical drawing, and the outer sheath of the flux-cored welding wire is made of T2 pure copper strip with a specification of 7×0.2 mm.

[0018] The specification of DH36 steel in step 3 is 150*150*5mm, and the preheating temperature is 200-300°C.

[0019] The MIG welding parameters in step 4 are: welding voltage of 15-19 V, welding current of 150-170 A, shielding gas with a volume fraction of 99.99% pure Ar, shielding gas flow rate of 15 L / min, swing arc welding process, welding speed of the swing arc welding part of 0.20 m / min, swing arc amplitude of 10 mm, swing arc frequency of 1.2 Hz, and the swing arc dwell time of 0.1 s.

[0020] The TIG welding parameters in step 5 are: welding current 140-160 A, tungsten electrode extension length 4 mm, welding speed 0.40 m / min, nozzle height 8 mm, shielding gas with a volume fraction of 99.99% pure Ar, and a shielding gas flow rate of 15 L / min.

[0021] The beneficial effects of the present invention are as follows: the copper-based corrosion-resistant flux-cored welding wire provided by the present invention uses Cu element as the base material, and forms a Cu-Ni-Cr base with the main component to improve the performance of the copper alloy cladding layer. The improved cladding layer is well combined with the welded joint of the marine steel and the DH36 steel substrate, without defects such as cracks and pores, and there is no melted unmixed area at the bonding surface. A dense protective layer is formed on the welded joint in the environment of seawater corrosion, which prevents further development of corrosion and thereby increases the corrosion resistance of the joint; and the flux-cored welding wire containing the Cu-Ni-Cr base is beneficial to the DH36 steel base material and the cladding layer in the molten state. The mutual mixing can reduce the penetration cracks at the interface, and the proportion of the flux core components can be adjusted according to the composition and performance requirements of the base material, and it has strong adaptability to different working conditions; on the other hand, the strengthening method provided by the present invention is based on the arc cladding technology, and a multi-layer and multi-pass welding cladding process is designed. The unique cladding process makes the cladding layer and the DH36 steel joint more tightly combined, and the cladding layer is surface quenched in conjunction with the secondary air-walking cladding heating to increase its hardness and facilitate operation, saving the heat treatment process and avoiding the generation of cracks on the joint surface. Combined with the flux-cored welding wire of the present invention, it effectively prevents seawater from corroding the joint and increases the service life of the hull. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the DH36 steel welded joint and the surface cladding layer in the present invention.

[0023] In the figure: 1. Cladding layer, 2. DH36 steel weld joint. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to specific embodiments.

[0025] The copper-based corrosion-resistant flux-cored welding wire provided by the present invention comprises a flux core and a welding wire sheath, wherein the flux core is composed of the following components by mass percentage: Ni powder: 10-15%; Si powder: 0.1-0.5%; Cr powder: 10-15%; Ti powder: 0-5%; Nb powder: 2-3%; W powder: 2%; and the rest is Cu powder, and the sum of the mass percentages of the above components is 100%.

[0026] The functions of the main components in this flux-cored welding wire are:

[0027] 1) The Ni element can be infinitely soluble in copper and steel, which is beneficial to improving the bonding performance between copper and steel and improving the toughness of steel. Adding nickel to copper can strengthen the weld metal and improve its corrosion resistance, especially against seawater corrosion.

[0028] 2) The Si element can form a solid solution in the Cu-Ni-Si system, forming a second phase strengthening mechanism.

[0029] 3) Cr element can improve the corrosion resistance of the medium and prevent the cladding layer from cracking.

[0030] 4) Ti element can react with Ni to form metal compounds, thereby improving the strength of the weld.

[0031] In addition, the main base material of the flux-cored welding wire is Cu, which can form a Cu-Ni-Cr matrix with Ni and Cr in the composition, which can improve the melted unmixed area at the copper / steel interface, form a dense protective layer, and effectively prevent seawater corrosion.

[0032] The outer sheath of the welding wire is a T2 pure copper strip. The filling rate of the flux-cored welding wire's flux-cored powder is 22wt.%-28wt.%, and the diameter of the flux-cored welding wire is 1.6mm.

[0033] The present invention also provides a method for surface strengthening of DH36 steel welded joints using the copper-based flux-cored corrosion-resistant welding wire, which specifically comprises the following steps:

[0034] Step 1: Weigh the following metal powders by mass percentage: Ni powder: 10-15%; Si powder: 0.1-0.5%; Cr powder: 10-15%; Ti powder: 0-5%; Nb powder: 2-3%; W powder: 2%; the rest is Cu powder, and the sum of the mass percentages of the above components is 100%;

[0035] Step 2: The metal powder weighed in step 1 is mixed evenly to form a flux core, and a pure copper strip is used as the welding wire sheath. The flux-cored welding wire is made by a wire drawing machine, and the prepared flux-cored welding wire is stored in a constant temperature box for use;

[0036] The metal powders can be mixed evenly by mechanical stirring, and a 7×0.2mm T2 pure copper strip is used as the outer sheath of the flux-cored welding wire. The mixed metal powder is filled into the outer sheath of the welding wire, and the flux-cored welding wire is drawn to the required 1.6mm by mechanical drawing on a wire drawing machine and stored for later use.

[0037] Step 3: Use an angle grinder to clean the surface of the DH36 steel weld joint to remove surface oil, oxide scale and other impurities, and then preheat the DH36 steel weld joint;

[0038] Among them, DH36 steel can be selected with specifications of 150*150*5mm, and the preheating temperature is 200~300℃;

[0039] Step 4: Using the flux-cored wire prepared in step 2, a multi-layer and multi-pass welding cladding process is designed based on the MIG welding cladding method to prepare a cladding layer on the surface of the preheated DH36 steel weld joint;

[0040] Among them, the cladding layer prepared on the surface of the DH36 steel weld joint is an upper and lower layer, the thickness of each cladding layer is designed to be 1-3mm, each cladding layer includes multiple parallel overlapping welds, each weld bead is 10mm wide, and the cladding overlap coverage of adjacent welds is 55%-60%. The MIG welding parameters are set, and the specific parameters are: welding voltage is 15-19V, welding current is 150-170A, shielding gas is 99.99% pure Ar with a volume fraction of 15L / min, shielding gas flow rate is 15L / min, swing arc welding process is adopted, welding speed of the swing arc welding part is 0.20m / min, swing arc amplitude is 10mm, swing arc frequency is 1.2Hz, and swing arc dwell time is 0.1s. The set parameters are imported into the MIG welding robot in a program mode to prepare the welding of the cladding layer;

[0041] Step 5: The cladding layer to be prepared is cooled to room temperature, and its surface is cleaned by mechanical grinding. Then, the cladding layer is heated by TIG welding along the weld bead of step 4 without feeding the welding wire;

[0042] The TIG welding parameters are as follows: welding current 140-160A, tungsten electrode extension length 4mm, welding speed 0.40m / min, nozzle height 8mm, shielding gas volume fraction 99.99% pure Ar, shielding gas flow rate 15L / min. A lower current input was used, and the cladding layer was subjected to a second air-run heat treatment to further contact and fuse the cladding layer and the joint to avoid cracks.

[0043] Step 6: After cooling to room temperature again, use mechanical cleaning to polish the surface of the cladding layer and polish the workpiece to the required smoothness to meet the use requirements of the workpiece.

[0044] Example 1

[0045] The copper-based corrosion-resistant flux-cored welding wire provided in this embodiment 1 includes a flux core and a welding wire sheath. The flux core is composed of the following components by mass percentage: Ni powder: 12%; Si powder: 0.5%; Cr powder: 11%; Ti powder: 0%; Nb powder: 2%; W powder: 2%; the rest is Cu powder, and the sum of the mass percentages of the above components is 100%. The welding wire sheath is T2 pure copper strip, the filling rate of the flux core powder in the flux-cored welding wire is 22wt.%, and the diameter of the flux-cored welding wire is 1.6mm.

[0046] The method for surface strengthening a DH36 steel weld joint using the copper-based flux-cored corrosion-resistant welding wire provided in Example 1 comprises the following steps:

[0047] Step 1: Weigh the following metal powders by mass percentage: Ni powder: 12%; Si powder: 0.5%; Cr powder: 11%; Ti powder: 0%; Nb powder: 2%; W powder: 2%; the rest is Cu powder, and the sum of the mass percentages of the above components is 100%;

[0048] Step 2: The metal powder weighed in step 1 is mixed evenly by mechanical stirring, and a 7×0.2 mm T2 pure copper strip is used as the outer sheath of the flux-cored welding wire. The mixed metal powder is filled into the outer sheath of the flux-cored welding wire. The filling rate of the flux-cored welding wire is 22 wt.%. The flux-cored welding wire is mechanically drawn to the required 1.6 mm and stored for later use.

[0049] Step 3: Use an angle grinder to clean the surface of the DH36 steel weld joint to remove impurities such as oil, oxide scale, etc. The specification of DH36 steel is 150*150*5mm, and then preheat the DH36 steel weld joint at a temperature of 200℃;

[0050] Step 4: Using the flux-cored welding wire prepared in step 2, a cladding layer is prepared on the surface of the preheated DH36 steel weld joint based on the MIG welding cladding method, wherein the number of prepared cladding layers is 2, the thickness of each cladding layer is 3 mm, each cladding layer includes multiple parallel overlapping welds, each weld is 10 mm wide, and the cladding overlap coverage of adjacent welds is 55%; the MIG welding parameters are: welding voltage is 15-19 V, welding current is 150-170 A, shielding gas is 99.99% pure Ar with a volume fraction, shielding gas flow rate is 15 L / min, swing arc welding process is adopted, the welding speed of the swing arc welding part is 0.20 m / min, the swing arc amplitude is 10 mm, the swing arc frequency is 1.2 Hz, and the swing arc dwell time is 0.1 s;

[0051] Step 5: After the cladding layer is cooled to room temperature, its surface is cleaned by mechanical grinding. Then, TIG welding is performed along the weld bead of step 4 to heat the cladding layer without feeding the welding wire. The TIG welding parameters are as follows: welding current 140-160A, tungsten electrode extension length 4mm, welding speed 0.40m / min, nozzle height 8mm, shielding gas with a volume fraction of 99.99% pure Ar, and a shielding gas flow rate of 15L / min.

[0052] Step 6: After cooling to room temperature again, use mechanical cleaning to polish the surface of the cladding layer to meet the use requirements of the workpiece.

[0053] The surface strengthening method of DH36 steel welded joint using the copper-based flux-cored corrosion-resistant welding wire provided in Example 1 was used to prepare the copper-based cladding layer. The mechanical properties of the cladding layer were tested and the average hardness of the cladding layer was 190.1HV. 0.1 , while the hardness of pure copper is 55HV 0.1 The hardness of the cladding layer is significantly improved compared with that of pure copper; in the friction and wear performance test, the friction coefficient of S214 commercial solid welding wire is 0.7051, and the friction coefficient of the cladding layer is 0.5823, with better wear resistance; in its electrochemical performance indicators, the higher the OCP value of the electrode to be tested, the lower its tendency to corrosion. After electrochemical performance testing, the OCP value of the DH36 welded joint is stable at -0.656, and the OCP value of the cladding layer is stable at -0.2328.

[0054] Example 2

[0055] The copper-based corrosion-resistant flux-cored welding wire provided in this embodiment 2 includes a flux core and a welding wire sheath. The flux core is composed of the following components in mass percentage: Ni powder: 15%; Si powder: 0.5%; Cr powder: 10%; Ti powder: 0%; Nb powder: 3%; W powder: 2%; the rest is Cu powder, and the sum of the mass percentages of the above components is 100%. The welding wire sheath is T2 pure copper strip, the filling rate of the flux core powder in the flux-cored welding wire is 26wt.%, and the diameter of the flux-cored welding wire is 1.6mm.

[0056] The method for surface strengthening a DH36 steel weld joint using the copper-based flux-cored corrosion-resistant welding wire provided in Example 2 comprises the following steps:

[0057] Step 1: Weigh the following metal powders by mass percentage: Ni powder: 15%; Si powder: 0.5%; Cr powder: 10%; Ti powder: 0%; Nb powder: 3%; W powder: 2%; the rest is Cu powder, and the sum of the mass percentages of the above components is 100%;

[0058] Step 2: The metal powder weighed in step 1 is mixed evenly by mechanical stirring, and a 7×0.2 mm T2 pure copper strip is used as the outer sheath of the flux-cored welding wire. The mixed metal powder is filled into the outer sheath of the flux-cored welding wire. The filling rate of the flux-cored welding wire is 26 wt.%. The flux-cored welding wire is mechanically drawn to the required 1.6 mm and stored for later use.

[0059] Step 3: Use an angle grinder to clean the surface of the DH36 steel weld joint to remove impurities such as oil, oxide scale, etc. The specification of DH36 steel is 150*150*5mm, and then preheat the DH36 steel weld joint at a temperature of 300℃;

[0060] Step 4: Using the flux-cored welding wire prepared in step 2, a cladding layer is prepared on the surface of the preheated DH36 steel weld joint based on the MIG welding cladding method, wherein the number of prepared cladding layers is 2 layers, the thickness of each cladding layer is 2 mm, each cladding layer includes multiple parallel overlapping welds, each weld is 10 mm wide, and the cladding overlap coverage of adjacent welds is 55%; the MIG welding parameters are: welding voltage is 15-19 V, welding current is 150-170 A, shielding gas is 99.99% pure Ar with a volume fraction, shielding gas flow rate is 15 L / min, swing arc welding process is adopted, the welding speed of the swing arc welding part is 0.20 m / min, the swing arc amplitude is 10 mm, the swing arc frequency is 1.2 Hz, and the swing arc dwell time is 0.1 s;

[0061] Step 5: After the cladding layer is cooled to room temperature, its surface is cleaned by mechanical grinding. Then, TIG welding is performed along the weld bead of step 4 to heat the cladding layer without feeding the welding wire. The TIG welding parameters are as follows: welding current 140-160A, tungsten electrode extension length 4mm, welding speed 0.40m / min, nozzle height 8mm, shielding gas with a volume fraction of 99.99% pure Ar, and a shielding gas flow rate of 15L / min.

[0062] Step 6: After cooling to room temperature again, use mechanical cleaning to polish the surface of the cladding layer to meet the use requirements of the workpiece.

[0063] The surface strengthening method of DH36 steel welded joint using the copper-based flux-cored corrosion-resistant welding wire provided in Example 2 was used to prepare the copper-based cladding layer. The mechanical properties of the cladding layer were tested and the average hardness of the cladding layer was 272.1HV. 0.1 ,After the electrochemical performance test, the OCP value of the cladding layer was stabilized at -0.2025.

[0064] Example 3

[0065] The copper-based corrosion-resistant flux-cored welding wire provided in this embodiment 3 includes a flux core and a welding wire sheath. The flux core is composed of the following components in mass percentage: Ni powder: 15%; Si powder: 0.35%; Cr powder: 15%; Ti powder: 3.5%; Nb powder: 2.5%; W powder: 2%; the rest is Cu powder, and the sum of the mass percentages of the above components is 100%. The welding wire sheath is T2 pure copper strip, the filling rate of the flux core powder in the flux-cored welding wire is 28wt.%, and the diameter of the flux-cored welding wire is 1.6mm.

[0066] The method for surface strengthening a DH36 steel weld joint using the copper-based flux-cored corrosion-resistant welding wire provided in Example 3 comprises the following steps:

[0067] Step 1: Weigh the following metal powders by mass percentage: Ni powder: 15%; Si powder: 0.35%; Cr powder: 15%; Ti powder: 3.5%; Nb powder: 2.5%; W powder: 2%; the remainder is Cu powder, and the sum of the mass percentages of the above components is 100%;

[0068] Step 2: The metal powder weighed in step 1 is mixed evenly by mechanical stirring, and a 7×0.2 mm T2 pure copper strip is used as the outer sheath of the flux-cored welding wire. The mixed metal powder is filled into the outer sheath of the welding wire. The filling rate of the flux-cored welding wire is 28 wt.%. The flux-cored welding wire is mechanically drawn to the required 1.6 mm and stored for later use.

[0069] Step 3: Use an angle grinder to clean the surface of the DH36 steel weld joint to remove impurities such as oil, oxide scale, etc. The specification of DH36 steel is 150*150*5mm, and then preheat the DH36 steel weld joint at a temperature of 300℃;

[0070] Step 4: Using the flux-cored welding wire prepared in step 2, a cladding layer is prepared on the surface of the preheated DH36 steel weld joint based on the MIG welding cladding method, wherein the number of prepared cladding layers is 2, the thickness of each cladding layer is 1 mm, each cladding layer includes multiple parallel overlapping welds, each weld is 10 mm wide, and the cladding overlap coverage of adjacent welds is 60%; the MIG welding parameters are: welding voltage is 15-19 V, welding current is 150-170 A, shielding gas is 99.99% pure Ar with a volume fraction, shielding gas flow rate is 15 L / min, swing arc welding process is adopted, the welding speed of the swing arc welding part is 0.20 m / min, the swing arc amplitude is 10 mm, the swing arc frequency is 1.2 Hz, and the swing arc dwell time is 0.1 s;

[0071] Step 5: After the cladding layer is cooled to room temperature, its surface is cleaned by mechanical grinding. Then, TIG welding is performed along the weld bead of step 4 to heat the cladding layer without feeding the welding wire. The TIG welding parameters are as follows: welding current 140-160A, tungsten electrode extension length 4mm, welding speed 0.40m / min, nozzle height 8mm, shielding gas with a volume fraction of 99.99% pure Ar, and a shielding gas flow rate of 15L / min.

[0072] Step 6: After cooling to room temperature again, use mechanical cleaning to polish the surface of the cladding layer to meet the use requirements of the workpiece.

[0073] The surface strengthening method of DH36 steel welded joint using the copper-based flux-cored corrosion-resistant welding wire provided in Example 3 was used to prepare the copper-based cladding layer. The mechanical properties of the cladding layer were tested and the average hardness of the cladding layer was 294.8HV. 0.1 The friction coefficient of the cladding layer is 0.4920; after electrochemical performance testing, the OCP value of the cladding layer is stable at -0.1944.

[0074] Example 4

[0075] The copper-based corrosion-resistant flux-cored welding wire provided in this embodiment 4 includes a flux core and a welding wire sheath. The flux core is composed of the following components in mass percentage: Ni powder: 10%; Si powder: 0.1%; Cr powder: 13%; Ti powder: 5%; Nb powder: 3%; W powder: 2%; the rest is Cu powder, and the sum of the mass percentages of the above components is 100%. The welding wire sheath is T2 pure copper strip, the filling rate of the flux core powder in the flux-cored welding wire is 24wt.%, and the diameter of the flux-cored welding wire is 1.6mm.

[0076] The method for surface strengthening a DH36 steel weld joint using the copper-based flux-cored corrosion-resistant welding wire provided in Example 4 comprises the following steps:

[0077] Step 1: Weigh the following metal powders by mass percentage: Ni powder: 10%; Si powder: 0.1%; Cr powder: 13%; Ti powder: 5%; Nb powder: 3%; W powder: 2%; the remainder is Cu powder, and the sum of the mass percentages of the above components is 100%;

[0078] Step 2: The metal powder weighed in step 1 is mixed evenly by mechanical stirring, and a 7×0.2 mm T2 pure copper strip is used as the outer sheath of the flux-cored welding wire. The mixed metal powder is filled into the outer sheath of the welding wire. The filling rate of the flux-cored welding wire is 24 wt.%. The flux-cored welding wire is mechanically drawn to the required 1.6 mm and stored for later use.

[0079] Step 3: Use an angle grinder to clean the surface of the DH36 steel weld joint to remove impurities such as oil, oxide scale, etc. The specification of DH36 steel is 150*150*5mm, and then preheat the DH36 steel weld joint at a temperature of 250℃;

[0080] Step 4: Using the flux-cored welding wire prepared in step 2, a cladding layer is prepared on the surface of the preheated DH36 steel weld joint based on the MIG welding cladding method, wherein the number of prepared cladding layers is 2 layers, the thickness of each cladding layer is 2 mm, each cladding layer includes multiple parallel overlapping welds, each weld bead is 10 mm wide, and the cladding overlap coverage of adjacent welds is 57%; the MIG welding parameters are: welding voltage is 15-19 V, welding current is 150-170 A, shielding gas is 99.99% pure Ar with a volume fraction, shielding gas flow rate is 15 L / min, swing arc welding process is adopted, the welding speed of the swing arc welding part is 0.20 m / min, the swing arc amplitude is 10 mm, the swing arc frequency is 1.2 Hz, and the swing arc dwell time is 0.1 s;

[0081] Step 5: After the cladding layer is cooled to room temperature, its surface is cleaned by mechanical grinding. Then, TIG welding is performed along the weld bead of step 4 to heat the cladding layer without feeding the welding wire. The TIG welding parameters are as follows: welding current 140-160A, tungsten electrode extension length 4mm, welding speed 0.40m / min, nozzle height 8mm, shielding gas with a volume fraction of 99.99% pure Ar, and a shielding gas flow rate of 15L / min.

[0082] Step 6: After cooling to room temperature again, use mechanical cleaning to polish the surface of the cladding layer to meet the use requirements of the workpiece.

[0083] The surface strengthening method of DH36 steel welded joint using the copper-based flux-cored corrosion-resistant welding wire provided in Example 4 was used to prepare the copper-based cladding layer. The mechanical properties of the cladding layer were tested and the average hardness of the cladding layer was 202.3HV. 0.1 The friction coefficient of the cladding layer is 0.5929; after electrochemical performance testing, the OCP value of the cladding layer is stable at -0.2897.

Claims

1. Copper-based corrosion-resistant flux-cored welding wire, characterized in that: The invention comprises a flux core and a welding wire sheath, wherein the flux core is composed of the following components by mass percentage: Ni powder: 10-15%; Si powder: 0.1-0.5%; Cr powder: 10-15%; Ti powder: 0-5%; Nb powder: 2-3%; W powder: 2%; the rest is Cu powder, and the sum of the mass percentages of the above components is 100%. The outer sheath of the flux-cored welding wire is made of T2 pure copper strip with a specification of 7×0.2 mm, and the filling rate of the flux-cored welding wire is 22wt.%-28wt.%; The diameter of the flux-cored welding wire is 1.6 mm.

2. A method for surface strengthening of DH36 steel welded joints using the copper-based corrosion-resistant flux-cored welding wire according to claim 1, characterized in that: The following steps are involved: Step 1: Weigh the following metal powders by mass percentage: Ni powder: 10-15%; Si powder: 0.1-0.5%; Cr powder: 10-15%; Ti powder: 0-5%; Nb powder: 2-3%; W powder: 2%; The rest is Cu powder, and the sum of the mass percentages of the above components is 100%; Step 2: The metal powder weighed in step 1 is mixed evenly to form a flux core, and a pure copper strip is used as the welding wire sheath. The flux-cored welding wire is made by a wire drawing machine, and the prepared flux-cored welding wire is stored in a constant temperature box for use; Step 3: Use an angle grinder to clean the surface of the DH36 steel weld joint to remove surface oil and oxide scale, and then preheat the DH36 steel weld joint; Step 4: Using the flux-cored wire prepared in step 2, a multi-layer and multi-pass welding cladding process is designed based on the MIG welding cladding method to prepare a cladding layer on the surface of the preheated DH36 steel weld joint; Step 5: The cladding layer to be prepared is cooled to room temperature, and its surface is cleaned by mechanical grinding. Then, the cladding layer is heated by TIG welding along the weld bead of step 4 without feeding the welding wire; Step 6: After cooling to room temperature again, use mechanical cleaning to polish the surface of the cladding layer to meet the use requirements of the workpiece.

3. The method for surface strengthening of DH36 steel welded joints according to claim 2, characterized in that: In step 2, the flux-cored welding wire is prepared by mechanical drawing, and the outer sheath of the flux-cored welding wire is made of T2 pure copper strip with a specification of 7×0.2 mm.

4. The method for surface strengthening of DH36 steel welded joints according to claim 2, characterized in that: The specification of DH36 steel in step 3 is 150*150*5mm, and the preheating temperature is 200~300℃.

5. The method for surface strengthening of DH36 steel welded joints according to claim 2, characterized in that: The multi-layer and multi-pass welding cladding process in step 4 adopts 2 cladding layers, each cladding layer has a thickness of 1-3 mm, each cladding layer includes multiple parallel overlapping welds, each weld is 10 mm wide, and the cladding overlap coverage of adjacent welds is 55%-60%.

6. The method for surface strengthening of DH36 steel welded joints according to claim 5, characterized in that: The MIG welding parameters are as follows: welding voltage is 15~19V, welding current is 150~170A, shielding gas is 99.99% pure Ar by volume, shielding gas flow rate is 15L / min, swing arc welding process is adopted, welding speed of swing arc welding part is 0.20m / min, swing arc amplitude is 10mm, swing arc frequency is 1.2Hz, and swing arc dwell time is 0.1s.

7. The method for surface strengthening of DH36 steel welded joints according to claim 2, characterized in that: The TIG welding parameters in step 5 are: welding current 140-160 A, tungsten electrode extension length 4 mm, welding speed 0.40 m / min, nozzle height 8 mm, shielding gas with a volume fraction of 99.99% pure Ar, and a shielding gas flow rate of 15 L / min.

Images