Welding process for improving corrosion resistance of high-strength weathering steel welded joint

Abstract

The invention discloses a welding process for improving the corrosion resistance of a high-strength weathering steel welding joint. Comprising the following steps that S1, a Q690qENH high-strength weather-resistant steel plate serves as a base material, the corrosion voltage Ecorr is larger than or equal to-0.620 V, and the corrosion current density icorr is smaller than or equal to 8.987 * 10 <-6 > (A.cm <-2 >); s2, welding equipment, welding materials and protective gas; s3, groove machining is carried out; s4, welding: a, backing welding; b, back gouging; c, filling welding; d, cosmetic welding; and S5, post-welding treatment is conducted, after the component is air-cooled to the room temperature, the component enters the corrosion and rusting stage, and welding work is completed. The problems that the high-strength weathering steel is difficult to weld, poor in welding quality and poor in corrosion resistance after welding are solved, the welding construction quality of the high-strength weathering steel is improved, the welding construction difficulty is reduced, and the performance of a welded joint is guaranteed; and the welding construction technical method of the high-strength weathering steel is widened, and a new material choice is provided for bridge construction and bridge design.

Description

Technical Field

[0001] The invention relates to welding, in particular to a welding process for improving the corrosion resistance of high-strength weathering steel welded joints. Background Art

[0002] High-strength weathering steel has the advantages of high strength, good toughness and strong corrosion resistance. It is widely used in engineering fields such as metallurgical construction, engineering machinery, mining equipment, bridge construction, offshore construction, and vehicles and ships. In order to improve the performance, various alloy elements such as Cr, Mo, Cu, Ni, etc. are added to the material. While improving the mechanical properties and corrosion resistance of the material, it seriously affects the weldability of the material, resulting in poor welding quality, easy formation of pores, slag inclusions, weld nodules, cracks, easy corrosion and other defects. Q690qENH weathering steel is a high-strength weathering steel that has received widespread attention in recent years. Various corrosion-resistant alloy elements such as Cu and Ni are added to its components, so that it forms a dense α-FeO ​​(OH) rust layer in the early stage of rust, so that it protects the base metal from further corrosion. After the welding connection process, the welded joint undergoes thermal cycling to form an uneven organizational composition, which is easy to destroy the element distribution and the organizational structure of the grain, making the welded joint the most susceptible to corrosion in the entire structure. Summary of the invention

[0003] The present invention aims to solve the above-mentioned technical problems, thereby providing a welding process for improving the corrosion resistance of high-strength weathering steel welded joints, solving the problems of poor weldability, low welding quality, poor mechanical properties and corrosion resistance of welded joints of high-strength weathering steel in traditional construction processes, improving the corrosion resistance and welding quality of steel welded joints, and increasing the service life of steel structures.

[0004] The present invention solves the technical problem and adopts the following technical solution: A welding process for improving the corrosion resistance of high-strength weathering steel welded joints, comprising the following steps: S1, the base material is Q690qENH high-strength weathering steel plate, the corrosion voltage is E corr ≥-0.620V, corrosion current density i corr ≤8.987·10 -6 (A·cm -2 ); S2. Welding equipment, welding materials and protective gas GMAW welding is used, the welding material is low alloy steel weathering welding wire with a weathering index of 12.34, and the volume fraction of the shielding gas is 80% Ar + 20% CO2; S3, groove processing The groove is single-sided V-shaped, and the single-sided groove angle is 30°; S4. Welding a. Base welding Apply a base weld on the back of the base material, with a welding current of 170A-175A, a welding voltage of 19V-20V, and a welding speed of 0.4m / min; b. Root cleaning Clean the root of the base weld on the front side of the parent material; c. Filling welding Apply a filler weld on the front of the base material, with a welding current of 228A-235V, a welding voltage of 20V-23V, and a welding speed of 0.4m / min; d. Cover welding A cap weld is applied on the filling weld, with a welding current of 275A to 285A, a welding voltage of 29V to 31V, and a welding speed of 0.4m / min; S5. Post-weld treatment After the components are air-cooled to room temperature, they enter the corrosion and rust stage, and the welding work is completed.

[0005] Compared with the prior art, the present invention using the above technical solution has the following beneficial effects: 1) It solves the problems of difficult welding, poor welding quality and poor corrosion resistance of high-strength weathering steel, greatly improves the quality of high-strength weathering steel welding construction, reduces the difficulty of welding construction, ensures the performance of welded joints, and improves the safety of steel structures; 2) It has broadened the technical methods for high-strength weathering steel welding construction, changed the dilemma of no high-strength steel materials available in the traditional bridge construction process, and provided new material options for bridge construction and bridge design; 3) The low-alloy high-strength weather-resistant welding wire used is universal and easy to obtain, which improves the economic efficiency of this method; 4) It avoids the use of anti-corrosion coatings and multiple repairs, thus improving the safety and economy of the bridge.

[0006] Further, the optimization scheme of the present invention is: In the step S1, the mechanical properties of the base material are ReL≥690 MPa and the tensile strength Rm≥800 MPa.

[0007] In step S2, the protective gas flow rate is 25 L / min.

[0008] In step S2, the diameter of the welding material is 1.2 mm.

[0009] In step S3, the blunt edge of the groove is 3 mm, and the butt clearance is 1.2 mm.

[0010] In the step S4-d, the swing distance during welding is 2 mm on each side, the swing frequency is 1 Hz / s, and there is no dwell time. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of the parent material docking according to an embodiment of the present invention; Figure 2 This is a microscopic morphology and organization diagram of the weld area of ​​an embodiment of the present invention; Figure 3 A microscopic morphology and organization diagram of the heat affected zone of an embodiment of the present invention; Figure 4 This is a microscopic morphology and organization diagram of the base material of an embodiment of the present invention; Figure 5 is the Tafel polarization curve; Figure 6 This is the Tafel polarization curve of the rusted sample. DETAILED DESCRIPTION

[0012] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0013] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0014] See also Figure 1 This embodiment provides a welding process for improving the corrosion resistance of high-strength weathering steel welded joints, which is performed in the following steps: S1, the base material is Q690qENH high-strength weathering steel plate, its thickness is 10 mm, the corrosion voltage of the base material is E corr ≥-0.620V, corrosion current density i corr ≤8.987·10 -6 (A·cm -2 ), the mechanical properties of the parent material are ReL≥690Mpa and tensile strength Rm≥800Mpa.

[0015] S2. Welding equipment, welding materials and protective gas GMAW welding is adopted, and the welding material is low-alloy steel weather-resistant welding wire with a weather resistance index of 12.34. The volume fraction of the shielding gas during welding is 80% Ar+20% CO2, and the shielding gas flow rate is 25L / min.

[0016] S3, groove processing The weld joint is processed into a single-sided V-shaped groove with a single-sided groove angle of 30° and a blunt edge of 3mm. The inner and outer surfaces of the groove within 20mm are polished clean to reveal the metallic luster, without rust and oil stains, and the butt clearance is 1.2mm.

[0017] S4. Welding a. Base welding Apply a base weld on the back of the two base materials, with a welding current of 170A-175A, a welding voltage of 19V-20V, and a welding speed of 0.4m / min; b. Root cleaning Clean the root of the base weld on the front of the parent material and use sandpaper to grind the other side of the base weld to clean the oxides and uneven parts left by the base weld to ensure that no defects such as slag inclusions and pores are generated in the subsequent welding process; c. Filling welding Apply a filling weld on the front of the parent material, with a welding current of 228A~235V, a welding voltage of 20V~23V, a welding speed of 0.4m / min, and clean the weld surface after welding; d. Cover welding A cap weld is applied on the filling weld, the welding current is 275A-285A, the welding voltage is 29V-31V, the welding speed is 0.4m / min, the swing distance during welding is 2mm on each side, the swing frequency is 1Hz / s, and there is no dwell time; S5. Post-weld treatment After the components are air-cooled to room temperature, they enter the corrosion and rust stage, and the welding work is completed.

[0018] Sample preparation and performance testing after welding: Electrochemical corrosion samples of 10mm×10mm×2mm are cut from the weld zone (WM), heat affected zone (HAZ), and base metal zone (BM) by wire cutting. After connecting the metal wires and sealing the samples, the test surface is polished. Test the Tafel polarization curve. The test results are as follows: Figure 5 After polishing and immersion in 3.5% NaCl solution for 720 hours, the Tafel polarization curve test of the rusted sample was carried out. The test results are shown in Figure 6 shown.

[0019] This welding process forms a dense α-FeO(OH) rust layer on Q690qENH high-strength weathering steel at the initial stage of corrosion, so that the base metal is no longer corroded under the protection of the dense α-FeO(OH) repair layer. The welded joint is divided into three parts: weld area (Figure), heat-affected zone, and parent metal. After testing, the welded joint forms a first rust layer in a 3.5% NaCl simulated marine environment and then tests the Tafel corrosion potential. The corrosion potential of the weld area sample and the heat-affected zone sample are consistent with the corrosion potential of the parent metal sample. This shows that the welded joint formed under this welding process has the same anti-corrosion performance as the parent metal, and both have the ability to form a dense first rust layer to prevent the base metal from continuing to corrode.

[0020] The present invention provides a new welding process with strong weldability, good welding forming quality, excellent mechanical properties of welded joints and excellent corrosion resistance, which avoids quality problems such as undercut, pores, weld nodules and weld slag in welded joints, ensures that welded joints will not become weak points in the mechanical properties of the overall structure and the first corrosion points in the corrosion resistance, and provides a good connection method for the actual engineering application of Q690qENH high-strength weathering steel.

[0021] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A welding process for improving the corrosion resistance of high-strength weathering steel welded joints, comprising the following steps: S1, the base material is Q690qENH high-strength weathering steel plate, the corrosion voltage is E corr ≥-0.620V, corrosion current density i corr ≤8.987·10 -6 (A·cm -2 ); S2. Welding equipment, welding materials and protective gas GMAW welding is used, the welding material is low alloy steel weathering welding wire with a weathering index of 12.34, and the volume fraction of the shielding gas is 80% Ar + 20% CO2; S3, groove processing The groove is single-sided V-shaped, and the single-sided groove angle is 30°; S4. Welding a. Base welding Apply a base weld on the back of the base material, with a welding current of 170A-175A, a welding voltage of 19V-20V, and a welding speed of 0.4m / min; b. Root cleaning Clean the root of the base weld on the front side of the parent material; c. Filling welding Apply a filler weld on the front of the base material, with a welding current of 228A-235V, a welding voltage of 20V-23V, and a welding speed of 0.4m / min; d. Cover welding A cap weld is applied on the filling weld, with a welding current of 275A to 285A, a welding voltage of 29V to 31V, and a welding speed of 0.4m / min; S5. Post-weld treatment After the components are air-cooled to room temperature, they enter the corrosion and rust stage, and the welding work is completed.

2. The welding process for improving the corrosion resistance of high-strength weathering steel welded joints according to claim 1 is characterized in that: In the step S1, the mechanical properties of the base material are ReL≥690 MPa and the tensile strength Rm≥800 MPa.

3. The welding process for improving the corrosion resistance of high-strength weathering steel welded joints according to claim 1 is characterized in that: In step S2, the protective gas flow rate is 25 L / min.

4. The welding process for improving the corrosion resistance of high-strength weathering steel welded joints according to claim 1 is characterized in that: In step S2, the diameter of the welding material is 1.2 mm.

5. The welding process for improving the corrosion resistance of high-strength weathering steel welded joints according to claim 1 is characterized in that: In step S3, the blunt edge of the groove is 3 mm, and the butt clearance is 1.2 mm.

6. The welding process for improving the corrosion resistance of high-strength weathering steel welded joints according to claim 1 is characterized in that: In the step S2-d, the swing distance during welding is 2 mm on each side, the swing frequency is 1 Hz / s, and there is no dwell time.

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