Gas shield welding method for Q500ME high-strength wind power steel

Abstract

The invention discloses a gas shielded welding method for Q500ME high-strength wind power steel, which is characterized in that a joint form is butt joint, a groove is formed by stacking a double-sided V shape, the angle is 60 degrees, and the truncated edge is 2mm; the brand of a gas shielded welding wire is KGM-Q70, and the diameter is 4 mm; pre-welding preheating of 100 DEG C and reasonable welding process parameters are adopted, the tensile strength of a welded joint is larger than or equal to 610 MPa, D = 3a 180 degrees, and the bending performance is intact; the low-temperature impact energy KV2 of a standard sample at-40 DEG C in a welding joint weld zone is greater than or equal to 31J, and the low-temperature impact energy KV2 of a standard sample at-40 DEG C in a heat affected zone is greater than or equal to 31J; and the highest hardness HV10 of a heat affected zone of a welding joint is less than 300. The problem of contradiction among high strength, high carbon equivalent and welding performance of Q500ME high-strength wind power steel is solved, and guiding significance is achieved for application of the steel plate.

Description

Technical Field

[0001] The invention belongs to the technical field of steel material welding, and in particular relates to a gas shielded welding method for Q500ME high-strength steel for wind power. Background Art

[0002] With the comprehensive promotion of large-scale development and high-quality development of wind power generation, the capacity of onshore wind turbines has increased to 8-10MW, requiring the tower to provide a higher bearing capacity. The steel used for wind power has been upgraded from Q355 to Q420, and the high strengthening of steel plates can reduce the weight of the tower by 12-14%. To this end, Q420-level high-strength wind power steel has entered the stage of mass production and application, and the annual steel consumption will account for 20-30%. 500MPa-level wind power steel Q500ME has also begun to be demonstrated and applied, but Q500ME has higher strength and theoretically worse welding performance. Therefore, it has become a key technical problem to reasonably solve the contradiction between high strength and easy welding of Q500ME wind power steel.

[0003] Chinese patent CN 109967840 B discloses "A gas shielded automatic welding process for Q420GJD steel for building structures". The welding material is CHW-SG / CF101GX; the flux is strictly baked before use; the X-shaped groove is selected according to the thickness of the parent material; the preheating temperature before welding is 80-110℃; a multi-layer multi-pass welding process is adopted, and the interlayer temperature is 150-180℃; the welding current is 610±10A, the welding voltage is 30-33V, the welding speed is 40±1cm / min, and the line energy is 27.5-32KJ / cm. It has been verified that the structural steel welding products produced by its gas shielded automatic welding process can fully obtain good comprehensive welding performance. The disadvantage is that it is suitable for Q420GJD, the strength grade is 420MPa, the quality grade is D, and the temperature is -20℃.

[0004] Chinese patent CN 110640277A discloses "A Q420 high-strength steel thick plate non-preheating double-wire gas shielded welding process", which can reduce the number of welds and improve welding efficiency without preheating and post-weld heat treatment while ensuring welding quality. The disadvantage is that the Q420 high-strength steel thick plate has a strength grade of 420MPa, a quality grade of C, and a temperature of 0°C.

[0005] Chinese patent CN110560843B discloses "A one-step forming welding process for Q420 high-strength steel thick plate gas-electric vertical welding", which uses a flux-cored wire with a diameter of 1.6 mm to weld the welding plate, realizing the application of the gas-electric vertical welding process on Q420 high-strength steel thick plate. The disadvantage is that the welding process is gas-electric vertical welding, with a large welding heat input and a strength grade of 420 MPa, which is completely different from the gas shielded welding involved in the present invention. Summary of the invention

[0006] The purpose of the present invention is to provide a Q500ME high-strength wind power steel gas shielded welding method. The welded joint obtained by the welding method of the present invention has excellent mechanical properties and impact properties, the tensile strength of the welded joint is ≥610MPa, and the D=3a180° bending performance is intact. The low-temperature impact energy KV2 of the standard sample at -40°C in the weld zone of the welded joint is ≥31J, and the low-temperature impact energy KV2 of the standard sample at -40°C in the heat-affected zone is ≥31J.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] The present invention provides a Q500ME high-strength wind power steel gas shielded welding method, and the specific steps are as follows:

[0009] Step 1, beveling:

[0010] A V-shaped groove is made on the double-butted base material, with a groove angle of 60° and a blunt edge of 2.0 mm;

[0011] Step 2, preprocessing:

[0012] Grind and clean the V-shaped groove and the steel plates within 25-30mm on both sides;

[0013] Step 3, Soldering:

[0014] First, a base weld is performed on the back, and gas shielded welding is used on the front. Multi-layer and multi-pass continuous welding is performed until the weld is filled. The welding current is 270-280A, the welding voltage is 28-30V, the welding speed is 40-43cm / min, the welding line energy is 10-12kJ / cm, and the interlayer temperature is controlled at <150℃.

[0015] Step 4, flaw detection

[0016] After standing for 24 hours after welding, the welded joints were inspected by X-ray, and the qualified level was NB / T47013.2-2015 Level II;

[0017] The chemical composition percentages of the Q500ME high-strength wind power steel are: C: 0.11-0.14%, Si: 0.20-0.35%, Mn: 1.45-1.70%, P≤0.015%, S≤0.005%, Nb: 0.030-0.045%, V: 0.030-0.045%, Ti: 0.011-0.020%, Cr: 0.15-0.30, %Als: 0.017-0.030%, carbon equivalent ≤0.47%, and the balance is Fe and unavoidable impurities.

[0018] Furthermore, the production process of the Q500ME high-strength wind power steel: (1) adopts C-Nb-V-Ti-Cr micro-alloying composition design; (2) adopts electromagnetic stirring and light reduction process to continuously cast into steel billets; (3) adopts thermomechanical rolling process to produce; the final structure of the steel plate is fine and uniform ferrite + pearlite structure + a small amount of bainite.

[0019] Furthermore, in step 1, the base material is thermomechanically rolled Q500ME high-strength steel for wind power, and the base plate combination is 14 to 40 mm thick butt-jointed.

[0020] Furthermore, in step 2, sandpaper is used for grinding and acetone is used for cleaning to remove rust and oil stains to ensure the quality of the welded joint.

[0021] Furthermore, in step 3, the preheating temperature before welding is 100° C., and no heat treatment is performed after welding.

[0022] Furthermore, in step 3, the gas shielded welding wire is brand KGM-Q70, with a diameter of 4 mm; the shielding gas is 100% CO2, the gas flow rate is 15-20 L / min, and the back root cleaning is performed by gas explosion and mechanical grinding.

[0023] Furthermore, the welded joint obtained by the welding method of the present invention has excellent mechanical properties and impact properties, satisfying: the tensile strength of the welded joint is ≥610MPa, D=3a 180° bending performance is intact; the low-temperature impact energy of the weld zone of the welded joint at -40°C standard sample KV2 is ≥31J, and the low-temperature impact energy of the heat-affected zone at -40°C standard sample KV2 is ≥31J.

[0024] Compared with the prior art, the beneficial technical effects of the present invention are:

[0025] (1) The gas shielded welding joint of the present invention has excellent low-temperature impact toughness, the tensile strength of the welded joint is ≥610MPa, and the D=3a 180° bending performance is intact. The low-temperature impact energy of the weld zone of the welded joint is KV2 ≥31J at -40℃ standard specimen, and the low-temperature impact energy of the heat-affected zone is KV2 ≥31J at -40℃ standard specimen.

[0026] (2) The maximum hardness HV10 of the heat-affected zone of the gas shielded welding joint of the present invention is less than 300, and has a lower crack tendency.

[0027] For a Q500ME high-strength steel for wind power, a welded joint with excellent performance was obtained by preheating at 100℃ before welding and using suitable welding wire through a reasonable gas shielded welding process, which solved the contradiction between high strength, high carbon equivalent and welding performance of thermomechanically rolled Q500ME high-strength steel for wind power, and has guiding significance for the application of thermomechanically rolled Q500ME high-strength steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below in conjunction with the accompanying drawings.

[0029] Figure 1 A schematic diagram of the groove of a gas shielded welding butt joint used in the present invention.

[0030] Figure 2 Macrostructure of welded joint in Example 1 of the present invention

[0031] Figure 3 400 times microstructure diagram of the weld area of ​​the weld joint of Example 1 of the present invention.

[0032] Figure 4 400 times microstructure diagram of the coarse grain zone in the heat affected zone of the weld joint in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The present invention is described in more detail below with reference to examples. These examples are merely descriptions of the best mode for carrying out the present invention and are not intended to limit the scope of the present invention in any way.

[0034] Chemical composition of each example

[0035] Example C Si Mn P S Nb V Ti Als 1 0.125 0.22 1.58 0.010 0.002 0.041 0.041 0.011 0.021 2 0.130 0.22 1.56 0.012 0.003 0.043 0.040 0.012 0.022 3 0.129 0.25 1.60 0.010 0.002 0.042 0.042 0.014 0.021

[0036] The Q500ME high-strength steel for wind power generation has a grain size of grade 11, a yield strength ≥500MPa, a tensile strength of 610-770MPa, an elongation after fracture A ≥17%, and a low-temperature impact energy KV2 ≥50J of a standard sample at -40°C.

[0037] Mechanical properties of steel plates in various examples

[0038]

[0039] In Examples 1 to 3, the welding material is KGM-Q70, with a diameter of 4 mm, which meets the requirements of GB / T 5293. The shielding gas is 100% CO2, with a gas flow rate of 15-20 L / min, and the back cleaning is performed by gas explosion and mechanical grinding.

[0040] The schematic diagram of the groove of the gas shielded welding butt joint used in Examples 1 to 3 is as follows: Figure 1 The macroscopic and microstructures of the welded joints are shown in Figure 2 to Figure 4 shown.

[0041] Example 1

[0042] The specific steps are as follows:

[0043] Step 1, beveling:

[0044] The base plate combination is 40+40mm two-plate butt joint, and a V-shaped groove is opened on the double-butted parent material of the base material, with a groove angle of 60° and a blunt edge of 2.0mm;

[0045] Step 2, preprocessing:

[0046] Use sandpaper to grind the V-shaped symmetrical groove and the steel plates within 25-30mm on both sides, and then clean them with acetone to remove rust and impurities to ensure the quality of the welded joint;

[0047] Step 3, Soldering:

[0048] The test plate was preheated to 100℃, and a back pass was first performed on the back. The back pass welding current was 270A, the voltage was 29.4V, the welding speed was 42cm / min, and the welding line energy was 9.64kJ / cm. The front side was welded by gas shielded welding, with multiple layers and multiple passes welded continuously until the weld was filled. The welding current was 270-280A, the welding voltage was 28-30V, the welding speed was 40-43cm / min, the welding line energy was 10-12kJ / cm, and the interlayer temperature was controlled at <150℃. A total of 21 passes were made on the 40mm thick test plate.

[0049] Step 4, flaw detection

[0050] After standing for 24 hours after welding, the welded joints were inspected by X-ray, and the qualified level was NB / T47013.2-2015 Level II.

[0051] The welded joints obtained by the above-mentioned gas shielded welding process have a tensile strength of 705MPa and 701MPa, both of which are broken at the base material outside the fusion line. The tensile strength of the entire weld is 723MPa, and the elongation after fracture is 23.0%. The average value of the impact energy of the standard sample at -40℃ in the weld zone (100\81\88) is 90J, and the average value of the impact energy of the standard sample at -40℃ in the heat affected zone (95 / 120 / 192) is 102J, which is much higher than the standard value of 31J. D=3a 180° bending performance is intact. The weld microstructure is proeutectoid ferrite, acicular ferrite and granular bainite, the microstructure of the coarse-grained heat affected zone is bainite, and the microstructure of the fine-grained heat affected zone is ferrite and granular bainite, with fine and uniform grains.

[0052] Vickers hardness tests were carried out on the upper surface, middle and weld toe of the weld joint. The test results are shown in Table 1. The maximum hardness HV10 of the heat affected zone is 275, which is much lower than 350, indicating that the weld joint has a low tendency to cold cracks.

[0053] Table 140mm steel plate welding joint hardness

[0054]

[0055] Embodiment 2:

[0056] The specific steps are the same as those in Example 1. The base plate assembly is a 30+30mm two-plate butt joint, and the test plate is welded 15 times in total.

[0057] The welded joints obtained by the above-mentioned gas shielded welding process have a tensile strength of 686MPa and 679MPa, both of which are broken at the base material outside the fusion line. The tensile strength of the entire weld is 701MPa, and the elongation after fracture is 23.0%. The average value of the impact energy of the standard sample at -40℃ in the weld zone (89\102\106) is 99J, and the average value of the impact energy of the standard sample at -40℃ in the heat affected zone (91 / 87 / 100) is 93J, which is much higher than 31J. D=3a180° bending performance is intact. The weld microstructure is proeutectoid ferrite, acicular ferrite and granular bainite, the microstructure of the coarse-grained heat affected zone is bainite, and the microstructure of the fine-grained heat affected zone is ferrite and granular bainite, with fine and uniform grains.

[0058] Vickers hardness tests were carried out on the upper surface, middle and weld toe of the weld joint. The test results are shown in Table 2. The maximum hardness HV10 of the heat-affected zone is 273, which is much lower than 350, indicating that the weld joint has a low tendency to cold cracks.

[0059] Table 230mm steel plate welding joint hardness

[0060]

[0061] Embodiment 3:

[0062] The specific steps are the same as those in Example 1. The base plate assembly is a 14+14mm two-plate butt joint, and the test plate is welded 5 times in total.

[0063] The welded joints obtained by the above-mentioned gas shielded welding process have a tensile strength of 684MPa and 676MPa, both of which are broken at the base material outside the fusion line. The tensile strength of the entire weld is 695MPa, and the elongation after fracture is 24.0%. The average value of the impact energy of the standard sample at -40℃ in the weld zone (78\76\85) is 80J, and the average value of the impact energy of the standard sample at -40℃ in the heat affected zone (74 / 82 / 91) is 82J, which is much higher than 31J. D=3a 180° bending performance is intact. The weld microstructure is proeutectoid ferrite, acicular ferrite and granular bainite, the microstructure of the coarse-grained heat affected zone is bainite, and the microstructure of the fine-grained heat affected zone is ferrite and granular bainite, with fine and uniform grains.

[0064] Vickers hardness tests were carried out on the upper surface, middle and weld toe of the weld joint. The test results are shown in Table 2. The maximum hardness HV10 of the heat-affected zone is 275, which is much lower than 350, indicating that the weld joint has a low tendency to cold cracks.

[0065] Table 220mm steel plate welding joint hardness

[0066]

[0067]

[0068] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A Q500ME high-strength wind power steel gas shielded welding method, characterized in that: The specific steps are as follows: Step 1, beveling: A V-shaped groove is made on the double-butted base material, with a groove angle of 60° and a blunt edge of 2.0 mm; Step 2, preprocessing: Grind and clean the V-shaped groove and the steel plates within 25-30mm on both sides; Step 3, Soldering: First, a base weld is made on the back, and the front side adopts the gas shielded welding method, and multiple layers and multiple passes are welded continuously until the weld is filled. The welding current is 270-280A, the welding voltage is 28-30V, the welding speed is 40-43cm / min, the welding line energy is 10-12kJ / cm, and the interlayer temperature is controlled at <150℃; Step 4, flaw detection After standing for 24 hours after welding, the welded joints were inspected by X-ray, and the qualified level was NB / T47013.2-2015 Level II; The chemical composition percentages of the Q500ME high-strength wind power steel are: C: 0.11-0.14%, Si: 0.20-0.35%, Mn: 1.45-1.70%, P≤0.015%, S≤0.005%, Nb: 0.030-0.045%, V: 0.030-0.045%, Ti: 0.011-0.020%, Cr: 0.15-0.30, %Als: 0.017-0.030%, carbon equivalent ≤0.47%, and the balance is Fe and unavoidable impurities.

2. The Q500ME high-strength wind power steel gas shielded welding method according to claim 1 is characterized in that: The production process of the Q500ME high-strength wind power steel is as follows: (1) C-Nb-V-Ti-Cr micro-alloying composition design is adopted; (2) electromagnetic stirring and light reduction process are adopted to continuously cast the steel billet; (3) thermomechanical rolling process is adopted to produce; the final structure of the steel plate is ferrite with fine and uniform grains + pearlite structure + a small amount of bainite.

3. The Q500ME high-strength wind power steel gas shielded welding method according to claim 1 is characterized in that: In the step 1, the base material is thermomechanically rolled Q500ME high-strength steel for wind power, and the base plate assembly is butt-jointed with equal thickness of 14 to 40 mm.

4. The Q500ME high-strength wind power steel gas shielded welding method according to claim 1 is characterized in that: In step 2, sandpaper is used for grinding, and acetone is used for cleaning to remove rust and oil stains to ensure the quality of the welding joint.

5. The Q500ME high-strength steel for wind power generation gas shielded welding method according to claim 1 is characterized in that: In step 3, the preheating temperature before welding is 100° C., and no heat treatment is performed after welding.

6. The Q500ME high-strength steel for wind power generation gas shielded welding method according to claim 1 is characterized in that: In step 3, the gas shielded welding wire is KGM-Q70 with a diameter of 4 mm; the shielding gas is 100% CO2 with a gas flow rate of 15-20 L / min, and the back root cleaning is performed by gas explosion and mechanical grinding.

7. The Q500ME high-strength steel for wind power generation gas shielded welding method according to claim 1 is characterized in that: The welded joint obtained by the welding method has excellent mechanical properties and impact properties, and meets the following requirements: the tensile strength of the welded joint is ≥610MPa, D=3a 180° bending performance is intact; the low-temperature impact energy KV2 of the standard specimen at -40°C in the weld zone of the welded joint is ≥31J, and the low-temperature impact energy KV2 of the standard specimen at -40°C in the heat-affected zone is ≥31J.

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