High-heat-input small-V-shaped-groove efficient butt welding method for thick-specification ultrahigh-strength steel

Abstract

The invention discloses a large heat input small V-shaped groove efficient butt welding method for thick ultra-high strength steel, which comprises the following steps: taking ultra-high strength steel as a welding base material, processing the ultra-high strength steel into a V-shaped groove, preheating the V-shaped groove by flame, and performing multi-layer single-pass welding. A welding joint manufactured by using the technical scheme of the invention is not fused, each layer of welding seam of the ultra-high strength steel thick plate is uniformly fused, the formability is more excellent, and the welding joint has more excellent mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the field of welding technology and relates to a butt welding method for ultra-high strength steel, and in particular to a high-efficiency butt welding method for thick ultra-high strength steel with large heat input and small V-shaped groove. Background Art

[0002] With the rapid development of engineering fields such as large-scale engineering machinery and equipment, ship equipment, mining equipment, petrochemicals, metallurgy, and electricity, the requirements for the engineering application performance of steel are getting higher and higher. In order to meet the application needs of related engineering industries, the mechanical properties of steel materials have been greatly improved, reaching the ultra-high strength steel level of more than 1000MPa. Moreover, for key components, in addition to requiring high strength of steel, it is also required to have a large thickness, that is, the thickness of the steel plate is more than 40mm. However, with the increase in strength and thickness of steel, it is becoming increasingly difficult to weld it, and the matching welding technology has also lagged behind.

[0003] Ultra-high-strength steel welding has a high tendency to cold cracks, and the existing welding technology generally uses complex grooves or small heat input. For example, patent CN105522262B (patent name "Welding method of low-alloy ultra-high-strength steel with yield strength 1100MPa") discloses a method for welding ultra-high-strength steel with a thickness of 4-30mm. For thicknesses above 10mm, a double-sided symmetrical X-shaped groove is used, the groove angle is 40 to 60°, and the welding heat input is controlled at 9 to 15kJ / cm. However, the X-shaped groove machining is relatively complicated and is not conducive to on-site welding; small heat input has low welding efficiency for thick steel plates (such as thickness above 30mm), which is not conducive to engineering applications. The welding method disclosed in patent CN116100130A (patent name "A welding method for ultra-high strength steel plates with a yield strength of 1400MPa") is only for welding ultra-high strength steel with a thickness of 4 to 20mm. Although the welding steel plate has a V-shaped groove, the groove angle is 50° and the welding heat input is 4 to 12kJ / cm.

[0004] In summary, the existing technology for welding ultra-high strength steel above 1100MPa mainly relies on low heat input, and the welding efficiency is low; the X-shaped groove, machining process and welding process are relatively complicated. Moreover, the efficient welding technology for ultra-high strength steel with a yield strength of 1400MPa and a thickness of more than 40mm has not yet been reported. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and propose a butt welding method for ultra-high strength steel to optimize the weldability of ultra-high strength steel welded joints, that is, an efficient butt welding method with large heat input and small V-shaped groove suitable for ultra-high strength steel with a thickness of 40 to 50 mm.

[0006] The technical purpose of the present invention is achieved through the following technical solutions.

[0007] A high heat input small V-groove high efficiency butt welding method for thick gauge ultra-high strength steel is carried out according to the following steps:

[0008] Step 1, processing the ultra-high strength steel plate used as the welding base material into a V-shaped groove;

[0009] In step 1, the mass percentage of the welding base material composition is C 0.20-0.35%, Si 0.35-0.5%, Mn0.5-1.0%, Ni 0.5-0.7%, Mo 0.1-0.25%, Cr 0.1-0.3%, V 0.02-0.035%, and the rest is Fe and unavoidable impurity elements; the yield strength is 1420-1510MPa.

[0010] In step 1, the thickness of the ultra-high strength steel plate is 40-50 mm, the groove angle is 40°, the groove height in the thickness direction is 2 mm, and the groove gap in the horizontal direction is 1 mm.

[0011] In step 1, the groove surface is grinded using a grinder.

[0012] Step 2, fix the two ends of the ultra-high strength steel plate by spot welding and use flame to preheat the steel plate to a preheating temperature of 25-120°C;

[0013] In step 2, the preheating temperature is 50-120 degrees Celsius.

[0014] In step 2, flame preheating is performed within 50 mm on the left and right sides of the groove edge.

[0015] Step 3, use the metal electrode gas shielded welding method to perform multi-layer single-pass welding: perform base welding, the welding pass is 1, and the welding heat input is 10-20kJ / cm; perform filling welding, the welding pass is 5-7, and the welding heat input is 28-40kJ / cm; perform cover welding, the welding pass is 1, and the welding heat input is 35-50kJ / cm; during the welding process, the welding interlayer temperature needs to be controlled at 120-200°C.

[0016] In step 3, the protective gas is 20% by volume of CO 2 A mixed gas with 80% Ar by volume, the welding wire extension length is 10-20mm, and the shielding gas flow rate is 20-25L / min.

[0017] In step 3, the test plate is welded in a multi-layer single-pass manner using a solid ER80-G welding wire, and the chemical composition of the welding wire is C 0.10-0.80%, Si 0.4-0.6%, Mn 1.0-1.5%, Ni 1.0-1.5%, Mo 0.3-0.5%, Cr0.1-0.3%, Cu 0.10-0.20%, and the rest is Fe in percentage by mass.

[0018] In step 3, the welding heat input of the base welding is 13-18 kJ / cm, the welding heat input of the filling welding is 30-40 kJ / cm, and the welding heat input of the cover welding is 38-46 kJ / cm. During the welding process, the welding interlayer temperature needs to be controlled at 150-200°C.

[0019] In the technical solution of the present invention, according to the material characteristics of ultra-high-strength steel, a welding method with large heat input and small V-groove is adopted, combined with the preheating temperature and interlayer control temperature, to ensure the formability and joint performance of the ultra-high-strength steel welded joint; while greatly improving the welding efficiency, the formability and joint performance of the ultra-high-strength steel welded joint are guaranteed. The tensile strength of the implemented joints is greater than 850MPa, the impact toughness of the weld at -40°C is greater than 50J, and the impact toughness of the heat-affected zone at -40°C is greater than 30J. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the groove structure of an embodiment of the present invention.

[0021] Figure 2 Schematic diagram of preheating before welding (1) according to an embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram of preheating before welding (2) according to an embodiment of the present invention.

[0023] Figure 4 These are photos of weld formation and microstructural characteristics of the weld joint of Example 1 of the present invention.

[0024] Figure 5 The following are photos of weld formation and microstructural characteristics of the weld joint of Example 2 of the present invention.

[0025] Figure 6 The following are photos of weld formation and microstructural characteristics of the weld joint of Example 3 of the present invention.

[0026] Figure 7 These are photos of weld formation and microstructural characteristics of the weld joint of Example 4 of the present invention.

[0027] Figure 8 This is a photo of the tensile fracture of a welded joint according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0029] Example 1

[0030] 1. The welding base material composition is: C 0.282%, Si 0.37%, Mn 0.82%, Ni 0.50%, Mo 0.25%, Cr 0.24%, V 0.043%, and the rest is Fe and unavoidable impurity elements; the yield strength is 1422MPa.

[0031] 2. The welding base material is ultra-high strength steel, and the thickness of the steel plate is 40 mm.

[0032] 3. Process the ultra-high-strength steel plate into a V-shaped groove with a groove angle of 40°, and grind the groove surface with a grinder, such as Figure 1 As shown, A is the thickness of the steel plate 40mm, D is the groove angle 40°, B is the height of the groove in the thickness direction 2mm, and C is the gap of the groove in the horizontal direction 1mm, and the same below.

[0033] 4. Fix the two ends of the test plate by spot welding, that is, fix them by spot welding at both ends of the weld along the length direction of the weld.

[0034] 5. Preheat the test plate by flame to reach the preheating temperature, the preheating temperature is 120℃. Figure 2 and 3 As shown, E is the flame preheating range, which is 50mm, that is, flame preheating is carried out within 50mm around the edge of the groove, the same below.

[0035] 6. Use the metal-electrode gas shielded welding method and use the ZX7-400 welding machine produced by Shanghai Songle Welding Equipment Co., Ltd. to perform multi-layer single-pass welding. The shielding gas is 20% (volume percentage) CO 2 +80% (volume percentage) Ar mixed gas, welding wire extension length 20mm, shielding gas flow rate is 25L / min.

[0036] 7. Use ER80-G solid welding wire to perform multi-layer single-pass welding on the test plate. The chemical composition of the welding wire is: C 0.081%, Si 0.54%, Mn 1.40%, Ni 1.40%, Mo 0.39%, Cr 0.17%, Cu 0.12%, and the rest is Fe.

[0037] 8. First, perform base welding on the test plate, with one welding pass and a welding heat input of 13.7 kJ / cm.

[0038] 9. After the base welding is completed, the test plate is filled with welding, with 5 passes and a welding heat input of 28.7 kJ / cm.

[0039] 10. After the filling welding is completed, the test plate is covered with welding, with one welding pass and a welding heat input of 38.1 kJ / cm.

[0040] 11. During the welding process, the temperature between welding layers needs to be controlled at 120℃.

[0041] Example 2

[0042] 1. The welding base material composition is: C 0.341%, Si 0.48%, Mn 0.77%, Ni 0.58%, Mo 0.20%, Cr 0.25%, V 0.025%, and the rest is Fe and unavoidable impurity elements.

[0043] 2. The welding base material is ultra-high strength steel, and the thickness of the steel plate is 50 mm.

[0044] 3. Process the ultra-high-strength steel plate into a V-shaped groove with a groove angle of 40°, and grind the groove surface with a grinder.

[0045] 4. Fix the two ends of the test plate by spot welding.

[0046] 5. Preheat the test panel by flame, the preheating temperature is 25℃.

[0047] 6. Use the metal-electrode gas shielded welding method and use the ZX7-400 welding machine produced by Shanghai Songle Welding Equipment Co., Ltd. to perform multi-layer single-pass welding. The shielding gas is 20% CO 2 +80% Ar mixed gas, welding wire extension length 20mm, shielding gas flow rate 25L / min.

[0048] 7. Use ER80-G solid welding wire to perform multi-layer single-pass welding on the test plate. The chemical composition of the welding wire is: C 0.088%, Si 0.55%, Mn 1.44%, Ni 1.41%, Mo 0.38%, Cr 0.18%, Cu 0.13%, and the rest is Fe.

[0049] 8. First, perform base welding on the test plate, with one welding pass and a welding heat input of 17.3 kJ / cm.

[0050] 9. After the base welding is completed, the test plate is filled with welding, with 6 passes and a welding heat input of 31.2 kJ / cm.

[0051] 10. After the filling welding is completed, the test plate is covered with welding, with one welding pass and a welding heat input of 45.4 kJ / cm.

[0052] 11. During the welding process, the temperature between welding layers needs to be controlled at 150℃.

[0053] Example 3

[0054] 1. The welding base material composition is: C 0.205%, Si 0.37%, Mn 0.56%, Ni 0.55%, Mo 0.18%, Cr 0.19%, V 0.028%, and the rest is Fe and unavoidable impurity elements.

[0055] 2. The welding base material is ultra-high strength steel, and the thickness of the steel plate is 45 mm.

[0056] 3. Process the ultra-high-strength steel plate into a V-shaped groove with a groove angle of 40°, and grind the groove surface with a grinder.

[0057] 4. Fix the two ends of the test plate by spot welding.

[0058] 5. Preheat the test panel by flame, the preheating temperature is 50℃.

[0059] 6. Use the metal-electrode gas shielded welding method and use the ZX7-400 welding machine produced by Shanghai Songle Welding Equipment Co., Ltd. to perform multi-layer single-pass welding. The shielding gas is 20% CO 2 +80% Ar mixed gas, welding wire extension length 20mm, shielding gas flow rate 25L / min.

[0060] 7. Use ER80-G solid welding wire to perform multi-layer single-pass welding on the test plate. The chemical composition of the welding wire is: C 0.083%, Si 0.57%, Mn 1.51%, Ni 1.49%, Mo 0.40%, Cr 0.17%, Cu 0.15%, and the rest is Fe.

[0061] 8. First, perform base welding on the test plate, with one welding pass and a welding heat input of 18.2 kJ / cm.

[0062] 9. After the base welding is completed, the test plate is filled with welding, with 5 passes and a welding heat input of 31.8 kJ / cm.

[0063] 10. After the filling welding is completed, the test plate is covered with welding, with one welding pass and a welding heat input of 38.3 kJ / cm.

[0064] 11. During the welding process, the temperature between welding layers needs to be controlled at 200℃.

[0065] Example 4

[0066] 1. The welding base material composition is: C 0.244%, Si 0.42%, Mn 0.59%, Ni 0.66%, Mo 0.18%, Cr 0.25%, V 0.028%, and the rest is Fe and unavoidable impurity elements.

[0067] 2. The welding base material is ultra-high strength steel, and the thickness of the steel plate is 50 mm.

[0068] 3. Process the ultra-high-strength steel plate into a V-shaped groove with a groove angle of 40°, and grind the groove surface with a grinder.

[0069] 4. Fix the two ends of the test plate by spot welding.

[0070] 5. Preheat the test panel by flame, the preheating temperature is 100℃.

[0071] 6. Use the metal-electrode gas shielded welding method and use the ZX7-400 welding machine produced by Shanghai Songle Welding Equipment Co., Ltd. to perform multi-layer single-pass welding. The shielding gas is 20% CO 2 +80% Ar mixed gas, welding wire extension length 20mm, shielding gas flow rate 25L / min.

[0072] 7. Use ER80-G solid welding wire to perform multi-layer single-pass welding on the test plate. The chemical composition of the welding wire is: C 0.087%, Si 0.61%, Mn 1.53%, Ni 1.43%, Mo 0.41%, Cr 0.18%, Cu 0.13%, and the rest is Fe.

[0073] 8. First, perform base welding on the test plate, with one welding pass and a welding heat input of 14.9 kJ / cm.

[0074] 9. After the base welding is completed, the test plate is filled with welding, with 6 passes and a welding heat input of 39.6 kJ / cm.

[0075] 10. After the filling welding is completed, the test plate is covered with welding, with one welding pass and a welding heat input of 46.8 kJ / cm.

[0076] 11. During the welding process, the temperature between welding layers needs to be controlled at 150℃.

[0077] After welding is completed and the welded joint metal is naturally cooled to room temperature 20-25 degrees Celsius, the tensile properties of the joint are tested according to GB / T2651-2008 "Welded Joint Tensile Test Method", and the tensile test is carried out on a 100t MTS universal testing machine. In addition, the impact properties of the weld and heat-affected zone are tested according to GB / T2650-2008 "Welded Joint Impact Test Method", and the impact test is carried out on a ZBC2752-ED pendulum impact testing machine. The mechanical properties of the ultra-high strength steel welded joint are tested, and the results are shown in the following table.

[0078] Tensile and impact (HAZ) mechanical properties of ultra-high strength steel butt joints with large heat input and small V-groove

[0079]

[0080] Comparative Example

[0081] 1. The welding base material composition is: C 0.281%, Si 0.472%, Mn 0.74%, Ni 0.496%, Mo 0.37%, Cr 0.244%, V 0.04%, Ti 0.011%, Cu 0.021%, Al 0.037%, and the rest is Fe.

[0082] 2. The welding base material is ultra-high strength steel.

[0083] 3. Make a V-shaped groove on the ultra-high-strength steel plate and grind the groove surface with a grinder.

[0084] 4. Weld and fix both ends of the test plate.

[0085] 5. Use the metal-electrode gas shielded welding method and use the ZX7-400 welding machine produced by Shanghai Songle Welding Equipment Co., Ltd. to perform multi-layer single-pass welding. The shielding gas is 20% CO 2 +80% Ar mixed gas, welding wire extension length 20mm, shielding gas flow rate 25L / min.

[0086] 6. Use ER80-G solid welding wire to perform multi-layer single-pass welding on the test plate. The chemical composition of the welding wire is: C 0.081%, Si 0.54%, Mn 1.40%, Ni 1.40%, Mo 0.39%, Cr 0.17%, Cu 0.12%, and the rest is Fe.

[0087] 7. First, perform base welding on the test plate, with one welding pass and a welding heat input of 13.7 kJ / cm.

[0088] 9. After the base welding is completed, the test plate is filled with welding, with 5 passes and a welding heat input of 28.7 kJ / cm.

[0089] 10. After the filling welding is completed, the test plate is covered with welding, with one welding pass and a welding heat input of 38.1 kJ / cm.

[0090] 11. During the welding process, the temperature between welding layers needs to be controlled at 120℃.

[0091] Figure 4—7 are the weld formation and microstructure characteristic photos of the weld joints of Examples 1-4, where six points basically located on the same line from the weld to the base material are selected for microstructure characterization, where FZ is the weld zone, CGHAZ corresponds to the coarse-grained heat-affected zone, FGHAZ corresponds to the fine-grained heat-affected zone, ICHAZ is the critical heat-affected zone, SCHAZ is the subcritical heat-affected zone, and BM is the base material. Figure 4 —7 It can be seen that compared with the comparative example, the welded joint prepared by the embodiment using the large heat input small V-groove welding method of the present invention has no unfused situation, and each layer of the weld of the ultra-high strength steel thick plate is evenly fused, showing a more excellent formability. The coarse grain heat affected zone (CGHAZ), fine grain heat affected zone (FGHAZ), critical heat affected zone (ICHAZ), and subcritical heat affected zone (SCHAZ) are mainly martensite or bainite. The heat affected zone after welding still has a very high strength. The fracture position during stretching after welding is not in the welding heat affected zone, but in the weld. As shown in the attached figure Figure 8 By using the welding materials and welding process described in the present invention, the weld (FZ) structure is mainly composed of acicular ferrite or bainite, so it has high strength and good toughness, that is, the strength is greater than 850MPa and the impact toughness at -40℃ is greater than 50J.

[0092] By adjusting the process parameters according to the content of the present invention, butt welding of ultra-high-strength steel thick plates can be achieved, and after testing, the performance is basically consistent with that of the present invention. The above is an exemplary description of the present invention. It should be noted that any simple deformation, modification or equivalent replacement that can be made by other technicians in this field without spending creative labor falls within the protection scope of the present invention without departing from the core of the present invention.

Claims

1. A high-efficiency butt welding method with large heat input and small V-groove for thick-gauge ultra-high-strength steel, It is characterized in that Follow the steps below: Step 1, processing the ultra-high strength steel plate as the welding base material into a V-shaped groove; the mass percentage of the welding base material composition is C 0.20-0.35%, Si 0.35-0.5%, Mn 0.5-1.0%, Ni 0.5-0.7%, Mo 0.1-0.25%, Cr 0.1-0.3%, V 0.02-0.035%, and the rest is Fe and unavoidable impurity elements; the yield strength is 1420-1510MPa; Step 2, fix the two ends of the ultra-high strength steel plate by spot welding and use flame to preheat the steel plate to a preheating temperature of 25-120°C; Step 3, use the metal electrode gas shielded welding method to perform multi-layer single-pass welding: perform base welding, the welding pass is 1, and the welding heat input is 10-20kJ / cm; perform filling welding, the welding pass is 5-7, and the welding heat input is 28-40kJ / cm; perform cover welding, the welding pass is 1, and the welding heat input is 35-50kJ / cm; during the welding process, the welding interlayer temperature needs to be controlled at 120-200°C.

2. A high heat input small V-groove high efficiency butt welding method for thick gauge ultra-high strength steel according to claim 1, It is characterized in that In step 1, the thickness of the ultra-high strength steel plate is 40-50 mm, the groove angle is 40°, the groove height in the thickness direction is 2 mm, and the groove gap in the horizontal direction is 1 mm.

3. A high heat input small V-groove high efficiency butt welding method for thick ultra-high strength steel according to claim 1, It is characterized in that In step 2, the preheating temperature is 50-120 degrees Celsius.

4. A high heat input small V-groove high efficiency butt welding method for thick gauge ultra-high strength steel according to claim 1, It is characterized in that In step 2, flame preheating is performed within 50 mm on the left and right sides of the groove edge.

5. A high heat input small V-groove high efficiency butt welding method for thick gauge ultra-high strength steel according to claim 1, It is characterized in that In step 3, the protective gas is 20% by volume of CO 2 A mixed gas with 80% Ar by volume, the welding wire extension length is 10-20mm, and the shielding gas flow rate is 20-25L / min.

6. A high heat input small V-groove high efficiency butt welding method for thick gauge ultra-high strength steel according to claim 1, It is characterized in that In step 3, the test plate is welded in a multi-layer single-pass manner using a solid ER80-G welding wire, and the chemical composition of the welding wire is C 0.10-0.80%, Si 0.4-0.6%, Mn 1.0-1.5%, Ni 1.0-1.5%, Mo0.3-0.5%, Cr 0.1-0.3%, Cu 0.10-0.20%, and the rest is Fe in percentage by mass.

7. A high heat input small V-groove high efficiency butt welding method for thick gauge ultra-high strength steel according to claim 1, It is characterized in that In step 3, the welding heat input of the base welding is 13-18 kJ / cm, the welding heat input of the filling welding is 30-40 kJ / cm, and the welding heat input of the cover welding is 38-46 kJ / cm. During the welding process, the welding interlayer temperature needs to be controlled at 150-200°C.

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