CN110640279B - Welding flux copper gasket method submerged-arc welding process for Q420 high-strength steel thick plate - Google Patents
Welding flux copper gasket method submerged-arc welding process for Q420 high-strength steel thick plate Download PDFInfo
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- CN110640279B CN110640279B CN201910944982.2A CN201910944982A CN110640279B CN 110640279 B CN110640279 B CN 110640279B CN 201910944982 A CN201910944982 A CN 201910944982A CN 110640279 B CN110640279 B CN 110640279B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/18—Submerged-arc welding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K33/00—Specially-profiled edge portions of workpieces for making soldering or welding connections; Filling the seams formed thereby
- B23K33/004—Filling of continuous seams
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/16—Arc welding or cutting making use of shielding gas
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/235—Preliminary treatment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2101/00—Articles made by soldering, welding or cutting
- B23K2101/18—Sheet panels
- B23K2101/185—Tailored blanks
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2103/00—Materials to be soldered, welded or cut
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Abstract
The invention provides a submerged arc welding process of a Q420 high-strength steel thick plate by a flux copper gasket method, which is characterized by comprising the following steps of: processing a Y-shaped welding groove at the welding position of the steel plate to be welded, which is a Q420 high-strength steel thick plate; welding a positioning welding line; respectively welding an arc striking plate and an arc extinguishing plate at two ends of the Y-shaped welding groove; welding stepped restrained welding lines at two ends of the welding groove; cleaning slag and impurities on the surface of the copper gasket, then spreading a back surface welding flux on the copper gasket, and closely attaching the copper gasket to the back surface of the welding groove after centering the center of the groove; selecting a proper welding material and proper electrode welding parameters for welding; and after welding, performing gouging cleaning on the incomplete penetration defects at the restrained welding seam positions of the arc starting end and the arc ending end, and performing repair welding on the gouging groove. The invention can effectively solve the problem that the mechanical property of the welding joint of the Q420 high-strength steel thick plate is seriously weakened under the high heat input welding process, and can realize the application of the welding flux copper liner method submerged arc welding high-efficiency welding process on the Q420 high-strength steel thick plate.
Description
Technical Field
The invention relates to a welding process of a high-strength steel thick plate, in particular to a submerged-arc welding process of a Q420 high-strength steel thick plate by a flux copper gasket method.
Background
With the improvement of technical indexes and service life requirements of buildings such as bridges, tunnels and the like, the bearing reinforced concrete structure is gradually replaced by a design structure of high-strength structural steel, and the steel adopted by the design is developed towards the direction of high strength and large thickness. Q420 is a low-alloy high-strength structural steel having a yield strength level of 420MPa or more, which has been applied to a steel box girder structure, a truss structure of a bridge building, a steel shell structure of a tunnel building, and the like.
In the welding of Q420 high-strength steel thick plates, the welding modes of manual shielded metal arc welding, semi-automatic carbon dioxide gas shielded welding and single wire submerged arc welding are adopted in the prior art, the welding heat input is low, the welding filling amount of a single-pass weld joint is limited, and a one-step forming welding process cannot be realized.
The welding flux copper backing method submerged arc welding, FCB submerged arc welding for short, is a single-side welding double-side forming submerged arc welding technology, welding is carried out by adopting double wires or three wires in the welding process, a copper backing and back welding flux are arranged on the back of a groove of a steel plate to be welded, the back welding seam can be formed forcibly and the back of the welding seam is protected, surface welding flux is spread on the surface of the groove of the steel plate to be welded, and welding electric arc and the surface welding seam are protected. The welding process has higher welding heat input and welding speed, and is usually configured at a splicing plate station of a plane subsection production line, so that the splicing plate welding efficiency can be improved.
However, the FCB submerged arc welding is a welding technique with large heat input, and is generally applied to the welding of marine steel plates with the thickness of 10-35mm and the strength and toughness lower than DH36, and if the FCB submerged arc welding is applied to the welding of Q420 high-strength steel thick plates with the thickness of 40mm, the heat input is as high as 300kJ/cm (because the FCB submerged arc welding is a one-step forming welding process, the larger the welding plate thickness is, the larger the metal filling amount in the welding process is, and the higher the required welding heat input is), on one hand, the metal in the heat affected zone of the joint is heated seriously to form an embrittlement phenomenon, and on the other hand, the burning loss phenomenon of alloy elements caused by the serious heating of the weld metal can reduce the mechanical properties of the welded joint; compared with the material of the DH36 steel plate for the ship, the Q420 high-strength steel has larger carbon equivalent, larger welding crack sensitivity coefficient and higher probability of forming cracks in the welding process.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a flux copper gasket method submerged-arc welding process of a Q420 high-strength steel thick plate, which effectively solves the problems that the welding crack defect is easily caused and the mechanical property of a welding joint is weakened under the conditions of large heat input welding and high-speed welding.
The technical scheme of the invention is realized as follows:
a submerged arc welding process of a Q420 high-strength steel thick plate by a flux copper gasket method comprises the following steps:
step 1, processing a Y-shaped welding groove at a welding position of a steel plate to be welded, wherein the steel plate to be welded is a Q420 high-strength steel thick plate, and the corresponding parameters of the Y-shaped welding groove are as follows: the angle of the groove is 43-47 degrees, the truncated edge is 5-7mm, and the root gap is 0-1 mm; after the machining is finished, cleaning oxide layers and impurities on the Y-shaped welding bevel face and the periphery of the Y-shaped welding groove within the range of 20-30 mm;
step 2, welding a positioning welding line by adopting a semi-automatic CO2 gas shielded welding mode, wherein the thickness of the positioning welding line is 4-5mm, the length of the positioning welding line is 50-60mm, and the distance between the welding lines is 400-500 mm;
step 4, welding stepped restrained welding lines at two ends of the welding groove, wherein
The initial end of the welding line is restrained by the welding line and welded into two layers: the length of the first layer of welding line from the initial end of the steel plate to be welded is 150-170mm, and the length of the second layer of welding line from the initial end of the steel plate to be welded is 50-70 mm;
the welding seam terminal restrains the welding seam and welds five layers: the first layer of welding line distance is 350-360mm in length of the terminal of the steel plate to be welded, the second layer of welding line distance is 330-340mm in length of the terminal of the steel plate to be welded, the third layer of welding line distance is 310-320mm in length of the terminal of the steel plate to be welded, the fourth layer of welding line distance is 290-300mm in length of the terminal of the steel plate to be welded, and the fifth layer of welding line distance is 270-280mm in length of the terminal of the steel plate to be welded;
step 5, the FCB welding material adopts a welding wire, a surface flux and a back flux which meet the requirements of CCS classification 3Y 42; the L-pole welding wire is a solid welding wire with the diameter specification of 4.8mm, the T1-pole welding wire is a solid welding wire with the diameter specification of 4.8mm, and the T2-pole welding wire is a solid welding wire with the diameter specification of 6.4 mm;
step 6, adding the dried surface flux into a flux hopper in advance, and keeping the temperature of the flux hopper at 75-85 ℃;
step 7, cleaning slag and impurities on the surface of the copper gasket, and then spreading back face welding flux on the copper gasket, wherein the spreading thickness is 5-6 mm, and the width is 100-120 mm; after the spreading is finished, the copper gasket is centered in the center of the groove and then is attached to the back of the welding groove, and then the copper gasket is knocked within 100mm of the two sides of the groove on the surface of the steel plate to be welded so that the back welding flux can be closely attached to the back of the steel plate to be welded;
step 8, centering each electrode, welding the center of the groove, and adjusting the angle and the distance of a welding gun, wherein: the L pole is inclined forward by 13 degrees, and the distance from the contact tip to the workpiece is 35 mm; the T1 pole is inclined forward by 0 DEG, and the distance from the contact tip to the workpiece is 40 mm; t2 inclining backward by 3 degrees, the distance from the contact tip to the workpiece is 45 mm; the distance between the L pole and the T1 pole is 35mm, and the distance between the T1 pole and the T2 pole is 130 mm; then adjusting the welding head to the position of an arc striking plate, placing arc striking cotton at the end part of the welding wire, opening a surface flux hopper switch to place lower surface flux, and starting welding;
monitoring the welding process, carrying out fine adjustment on welding parameters in time according to the welding state, and carrying out arc quenching and stopping welding after a welding head is welded to an arc quenching plate;
step 9, after welding, moving the steel plate to be welded to a repairing station, performing gouging cleaning on the incomplete penetration defect of the restrained weld positions of the arc starting end and the arc ending end, polishing a gouging groove by adopting a mechanical polishing mode, and performing repair welding on the gouging groove by adopting a semi-automatic CO2 gas shielded welding overhead welding mode; and after the repair welding of the gouging groove is finished, mechanically polishing the surface of the repair welding seam in a mechanical polishing mode to ensure that the repair welding seam can be smoothly transited with the periphery.
Further, in the step 2, the step 3 and the step 4, the flux-cored wire used in the welding process meets the specified requirements of E81T1-K2CJ in AWS A5.29 standard.
Further, in the step 4, when the welding seam is restrained to be welded, arc striking is carried out in the formal slope of the steel plate to be welded, and arc is converged in the arc striking plate and the arc quenching plate.
Further, in step 7, when the copper gasket is centered on the center of the groove and then closely attached to the back surface of the welding groove, the air pressure of the pressure hose in the gasket device is set to be 0.10Mpa-0.12 Mpa.
Further, in step 8, during welding, the power supply characteristics of the L pole, the T1 pole and the T2 pole are all selected from alternating current characteristics, the welding speed is set to be 36cm/min, and the welding parameters of each electrode are set as follows:
l pole: the welding current 1430-;
t1 pole: welding current 1280-1320A, welding voltage 39-41V;
t2 pole: the welding current is 1280-1320A, and the welding voltage is 45-47V.
Furthermore, the thickness of the Q420 high-strength steel thick plate is 38-40 mm.
Compared with the prior art, the invention has the following advantages: the invention realizes the application of the FCB submerged arc welding process in the welding of Q420 high-strength steel thick plates by strictly controlling the parameters of the welding groove, strictly assembling and cleaning steel plates to be welded, constraining the welding seam at the beginning and the end of the welding seam by a step method, selecting proper welding wire and welding flux combination and matching proper welding process parameters to control the welding heat input quantity for welding. The invention can not only improve the welding efficiency of the jointed board of the Q420 high-strength steel thick plate and ensure that the mechanical property of the welding joint of the Q420 high-strength steel thick plate can meet the acceptance requirement of the standard specification, but also can effectively avoid the generation of welding defects, thereby enabling the high-efficiency and quality-guaranteed welding of the Q420 high-strength steel thick plate to be possible.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic view of a welding groove structure of a Q420 high-strength steel thick plate;
FIG. 2 is an assembly view of a thick Q420 high strength steel plate before welding;
FIG. 3 is a structural view of a restraint welding seam at the arc striking end of a Q420 high-strength steel thick plate;
FIG. 4 is a structural view of a restraint welding seam at the arc-ending end of a Q420 high-strength steel thick plate;
fig. 5 is a diagram of a welding electrode arrangement.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention discloses a flux copper gasket method submerged arc welding process of a Q420 high-strength steel thick plate, which is particularly applied to the flux copper gasket method submerged arc welding of the Q420 high-strength steel thick plate with the thickness of 38-40 mm, in particular to the Q420 high-strength steel thick plate with the thickness of 40mm, and specifically comprises the following steps:
step 1, processing a Y-shaped welding groove at a welding position of a steel plate to be welded, wherein the steel plate to be welded is a Q420 high-strength steel thick plate, the Y-shaped welding groove is shown in figure 1, and corresponding parameters of the Y-shaped welding groove are respectively as follows: the angle of the groove is 43-47 degrees, the truncated edge is 5-7mm, and the root gap is 0-1 mm; after the machining is finished, cleaning oxide layers and impurities on the Y-shaped welding bevel face and the periphery of the Y-shaped welding groove within the range of 20-30 mm;
in the embodiment of the invention, the oxide layer and impurities within the range of 20-30mm around the Y-shaped welding bevel and the Y-shaped welding bevel comprise rust, moisture, oil stain or other impurities, wherein the impurities of the oxide layer and the rust can be cleaned by adopting a mechanical polishing mode, and the impurities of the moisture and the oil stain can be removed by adopting flame baking. The cleaning of the oxide layer and impurities is beneficial to preventing the impurities near the Y-shaped welding groove from entering the welding line in the welding process, and further easily generating welding defects such as cracks, air holes, slag inclusion and the like.
The setting of the angle, the truncated edge and the root gap of the groove has an important influence on the formation of the weld joint, and if the angle of the groove is too small, the penetration capability of a welding arc to the root of the groove is limited, so that a back weld joint is easy to form a non-penetration welding defect; if the groove angle is too large, the groove cross-sectional area is too large, and the phenomenon of insufficient filling amount of welding materials occurs, so that the surface of the welding seam is sunken. If the root gap is too small, the burn-through phenomenon is easily caused, and even the copper gasket on the back side is damaged; if the root gap is too large, the welding arc acting force is difficult to melt through the root of the groove, and the incomplete penetration welding defect is easy to form.
Step 2, as shown in FIG. 2, welding a positioning welding line by adopting a semi-automatic CO2 gas shielded welding mode, wherein the thickness of the positioning welding line is 4-5mm, the length of the positioning welding line is 50-60mm, and the welding line interval is 400-500 mm;
when the positioning welding seam is welded, the yield strength of the Q420 steel is more than or equal to 420Mpa, and according to the welding material matching principle, the welding material needs to meet the strength requirement of the steel plate. Meanwhile, the welding wire has better crack resistance, so that cracks are avoided, and practice shows that when the adopted flux-cored welding wire meets the specified requirements of E81T1-K2CJ in AWS A5.29 standard, the requirement of a welding material matching principle can be met, and the welding wire is ensured to have better crack resistance.
Specifically, in the step 2, the adopted welding wire is a flux-cored welding wire of Tiantai TWE-81K2, and the diameter specification is 1.2 mm. Of course, the welding material adopted by the invention is not limited to flux-cored wire of Tantai TWE-81K2, and can be specifically selected according to the requirement as long as the welding material meets the specified requirement of E81T1-K2CJ in AWS A5.29 standard.
In the embodiment of the invention, the excessively high positioning welding seam is easy to influence the back forming of the welding seam, the length and the interval of the positioning welding seam mainly influence the restraint effect of the assembly of the steel plates to be welded, and if the length of the positioning welding seam is excessively short and the interval of the positioning welding seam is excessively long, the positioning welding seam cannot provide enough restraint effect, so that the welding seam is cracked; if the length of the positioning welding line is too long and the distance between the positioning welding lines is too short, the assembly positioning welding quantity of the steel plates to be welded is increased, and the assembly efficiency of the steel plates to be welded is affected. In the FCB welding, the steel plates after being assembled and positioned and welded are conveyed to a welding station through a roller way, and the conveying process is not easy to cause positioning welding cracking relative to a lifting conveying mode. And FCB welding process steel sheet back adopts the magnet to adsorb fixedly, can provide certain effect of restraint. The above factors are comprehensively considered in the embodiment and practice shows that when the height of the positioning welding line is 4-5mm, the length of the positioning welding line is 50-60mm, and the distance between the welding lines is 400-500mm, the effect is optimal, enough restraining force can be provided, and the positioning welding line is not easy to crack.
in the embodiment of the invention, the size of the welding plate is 40mm in thickness, 2000mm in length and 2000mm in width, the length of the arc striking plate and the arc extinguishing plate can be 300mm and the width can be 250mm, the arc striking plate and the arc extinguishing plate are Q420 high-strength steel thick plates, the thickness and the groove size of the arc striking plate and the arc extinguishing plate are the same as those of the steel plate to be welded in the embodiment of the invention, the stability of the formal welding seam welding process can be effectively ensured, and the welding defect at the beginning end and the end of the formal welding seam is avoided.
The yield strength of the Q420 steel is more than or equal to 420Mpa, and the welding material needs to meet the strength requirement of the steel plate according to the welding material matching principle. Meanwhile, the welding wire has better crack resistance and avoids forming cracks, and practice shows that when the adopted flux-cored welding wire meets the specified requirements of E81T1-K2CJ in AWS A5.29 standard, the requirement of a welding material matching principle can be met. Specifically, in the embodiment of the invention, the adopted welding wire is a flux-cored welding wire of Tiantai TWE-81K2, and the diameter specification is 1.2 mm. Similarly, the welding material used in the invention is not limited to flux-cored welding wire of Tantai TWE-81K2, and can be specifically selected according to requirements as long as the welding material meets the specified requirements of E81T1-K2CJ in AWS A5.29 standard.
Step 4, welding stepped restrained welding lines at two ends of the welding groove, wherein
As shown in fig. 3, the weld start ends constrain the weld to weld two layers: the length of the first layer of welding line from the initial end of the steel plate to be welded is 150-170mm, and the length of the second layer of welding line from the initial end of the steel plate to be welded is 50-70 mm;
as shown in fig. 4, the weld terminals constrain the weld to weld five layers: the first layer of welding line distance is 350-360mm in length of the terminal of the steel plate to be welded, the second layer of welding line distance is 330-340mm in length of the terminal of the steel plate to be welded, the third layer of welding line distance is 310-320mm in length of the terminal of the steel plate to be welded, the fourth layer of welding line distance is 290-300mm in length of the terminal of the steel plate to be welded, and the fifth layer of welding line distance is 270-280mm in length of the terminal of the steel plate to be welded;
in the embodiment of the invention, the adopted flux-cored wire meets the specified requirements of E81T1-K2CJ in AWS A5.29 standard so as to improve the crack resistance of the positioning welding seam. Specifically, in the step 4, the adopted welding wire is a flux-cored welding wire of Tiantai TWE-81K2, and the diameter specification is 1.2 mm. Similarly, the welding material used in the step is not limited to flux-cored welding wire of Tantai TWE-81K2, and can be specifically selected according to requirements as long as the welding material meets the requirements specified in AWS A5.29 standard E81T1-K2 CJ.
Step 5, the FCB welding material adopts a welding wire, a surface flux and a back flux which meet the requirements of CCS classification 3Y 42; the L-pole welding wire is a solid welding wire with the diameter specification of 4.8mm, the T1-pole welding wire is a solid welding wire with the diameter specification of 4.8mm, and the T2-pole welding wire is a solid welding wire with the diameter specification of 6.4 mm;
specifically, in the step 5, a solid welding wire with the grade of Shen steel US-36LS and the diameter specification of 4.8mm is used as an L-pole welding wire, a solid welding wire with the grade of Shen steel US-36T and the diameter specification of 4.8mm is used as a T1 pole welding wire, and a solid welding wire with the grade of Shen steel US-36T and the diameter specification of 6.4mm is used as a T2 pole welding wire; and the flux with the trademark of Shen steel PF-I55E is selected as the surface flux, and the flux with the trademark of Shen steel PF-I50R is selected as the back flux. The welding wires with the brands of Shen steel US-36LS and US-36T, US-36T are matched with a surface welding flux PF-I55E and a back welding flux PF-I50R, the requirement of CCS classification society 3Y42 grade can be met, and the welding material combination has already obtained the approval of CCS classification society 3Y42 grade.
The CCS specification stipulates and approves 33 grades of welding materials, such as 1, 2, 3, 1Y, 2Y, 3Y, 4Y, 2Y40, 3Y40, 4Y40, 5Y40, 3Y42 … … and the like, 3Y42 is one grade, the yield strength of deposited metal of the welding materials is more than or equal to 420MPa, the tensile strength 530 and 680MPa, the elongation is more than or equal to 20 percent, and the average impact energy of an impact test at the temperature of minus 20 ℃ is more than or equal to 47J.
Step 6, adding the dried surface flux into a flux hopper in advance, and keeping the temperature of the flux hopper at 75-85 ℃;
in the embodiment of the invention, the drying of the surface flux must be ensured, and if the surface flux is moistened before the surface flux is added, the surface flux is baked at 250-350 ℃ for 1 hour and then added into a flux hopper.
The flux hopper is maintained at a temperature of 75 c to 85 c and also to keep the surface flux dry in order to avoid moisture in the air from entering the surface flux.
Step 7, cleaning slag and impurities on the surface of the copper gasket, and then spreading back face welding flux on the copper gasket, wherein the spreading thickness is 5-6 mm, and the width is 100-120 mm; after the spreading is finished, the copper gasket is centered in the center of the groove and then is attached to the back of the welding groove, and then the copper gasket is knocked within 100mm of the two sides of the groove on the surface of the steel plate to be welded so that the back welding flux can be closely attached to the back of the steel plate to be welded;
in the embodiment of the invention, the copper liner needs to be kept dry, and if the surface of the copper liner is wet, a torch is adopted to bake the copper liner to remove water.
Wherein, when the copper liner is centered at the center of the groove and then closely attached to the back of the welding groove, the air pressure of the pressure hose in the liner device is set to be 0.10MPa-0.12 MPa. The liner device refers to a copper liner and an equipment device for driving the copper liner to move up and down, left and right.
In the embodiment of the invention, if the air pressure is too low, the copper gasket cannot be tightly attached to the back surface of the steel plate, and the welding molten metal easily flows out from the back surface of the steel plate to form a burn-through phenomenon; the copper gasket has overlarge jacking pressure on the steel plate due to overlarge air pressure, so that the steel plate is easy to deform; therefore, it is preferable to set the air pressure to 0.10MPa to 0.12 MPa.
Step 8, as shown in fig. 5, centering each electrode on the center of the welding groove, and adjusting the angle and distance of the welding gun, wherein: the L pole is inclined forward by 13 degrees, and the distance from the contact tip to the workpiece is 35 mm; the T1 pole is inclined forward by 0 DEG, and the distance from the contact tip to the workpiece is 40 mm; t2 inclining backward by 3 degrees, the distance from the contact tip to the workpiece is 45 mm; the distance between the L pole and the T1 pole is 35mm, and the distance between the T1 pole and the T2 pole is 130 mm; then adjusting the welding head to the position of an arc striking plate, placing arc striking cotton at the end part of the welding wire, opening a surface flux hopper switch to place lower surface flux, and starting welding;
in the embodiment of the invention, during welding, the power supply characteristics of the L pole, the T1 pole and the T2 pole are all selected from alternating current characteristics, the welding speed is set to be 36cm/min, and the welding parameters of each electrode are set as follows:
l pole: the welding current 1430-;
t1 pole: welding current 1280-1320A, welding voltage 39-41V;
t2 pole: the welding current is 1280-1320A, and the welding voltage is 45-47V.
Monitoring the welding process, carrying out fine adjustment on welding parameters in time according to the welding state, and carrying out arc quenching and stopping welding after a welding head is welded to an arc quenching plate;
in the embodiment of the invention, the L-pole inclination angle mainly influences the back surface forming effect, and the T2-pole inclination angle mainly influences the surface forming effect. The distance from the contact tip to the workpiece needs to be matched with welding current and welding voltage, and welding stability is affected by overlarge or undersize parameters of the contact tip. The distance between the L pole and the T1 pole is 35mm as the best, the interference is formed between two electrodes when the distance is too small, the welding slag inclusion defect is easily formed when the distance is too large, the distance between the T1 pole and the T2 pole is 130mm as the best, the T2 pole easily remelts the welding seam formed by the L pole and the T1 pole to generate back surface depression when the distance is too small, and the welding slag inclusion defect is also formed when the distance is too large.
In the welding process, the L pole adopts larger current and smaller voltage, so that larger fusion depth can be obtained, and the forming effect of the back of the welding seam is ensured. The T2 pole adopts smaller current and larger voltage, and can improve the forming effect of the weld surface. The T1 utmost point mainly plays the filling effect, and welding voltage is located between the L utmost point and the T2 utmost point, can adjust and melt wide, ensures that the root and facial melt wide can the mild transition, avoids forming not fusion, welding defects such as pressing from both sides the sediment. Since the FCB welding is a one-step forming welding process, the welding current, the welding voltage, and the welding speed of each electrode must be matched with the height of the welding groove, otherwise the overall weld forming effect is affected.
Step 9, after welding, moving the steel plate to be welded to a repairing station, carrying out air gouging cleaning on the incomplete penetration defects of the restrained weld positions of the arc starting end and the arc ending end, and polishing the air gouging groove by adopting a mechanical polishing mode; then, performing repair welding on the gouging groove in a semi-automatic CO2 gas shielded welding overhead welding mode; after the repair welding of the gouging groove is finished, mechanically polishing the surface of the repair welding seam in a mechanical polishing mode to ensure that the repair welding seam can be smoothly transited with the periphery;
and 10, cutting off arc striking plates and arc extinguishing plates at two ends of the Q420 high-strength steel thick plate.
Furthermore, in the step 4, when the welding seam is restrained to be welded, arc striking is needed in the formal notch of the Q420 high-strength steel thick plate, arc is converged in the arc striking plate and the arc quenching plate, and the phenomenon that the arc pit defect appearing at the arc-converging position is remained in the notch of the steel plate to be welded to influence the welding quality of the formal welding seam is avoided.
In the embodiment of the invention, after welding is finished for 24 hours, nondestructive testing and mechanical property testing are carried out on the welding joint, and the result is as follows: magnetic powder detection is carried out on the welding joint, the surface of the welding joint is free of defects, and the 2X requirement of GB/T26952 and 2011 is met; ultrasonic detection is carried out on the welding joint, the interior of the welding joint is free of defects, and the requirement of GB/T29712 and 2013 on level 2 is met. Wherein, the welded joint tensile strength testing result, the welded joint bending test testing result, and the welded joint impact toughness testing result are respectively as follows:
tensile strength detection result of welded joint
Test result of welding joint bending test
Test result of impact toughness of welded joint
In the above table, WM indicates the weld center position, FL indicates the weld line position, FL +2 indicates the heat affected zone position 2mm from the weld line, and FL +5 indicates the heat affected zone position 5mm from the weld line; FL +10 represents the heat affected zone position 10mm from the weld line; the face was 2mm from the surface of the sample, and the root was 2mm from the back of the sample.
From the above tables, it can be seen that the mechanical properties of the welded joint after the Q420 high-strength steel thick plate is subjected to submerged arc welding by the flux copper backing method meet the standard requirements of the welding process assessment test for steel, nickel and nickel alloy (GB/T19869.1-2005), and the welding process assessment is approved by project supervision engineers.
In conclusion, the invention realizes the application of the FCB submerged arc welding process in the welding of the Q420 high-strength steel thick plate by strictly controlling the welding groove parameters, strictly assembling and cleaning the steel plate to be welded, restraining the welding line by the step method at the beginning and the end of the welding line, selecting the proper welding wire and welding flux combination and matching the proper welding process parameters to control the welding heat input quantity for welding. The invention can not only improve the welding efficiency of the jointed board of the Q420 high-strength steel thick plate and ensure that the mechanical property of the welding joint of the Q420 high-strength steel thick plate can meet the acceptance requirement of the standard specification, but also can effectively avoid the generation of welding defects, thereby enabling the high-efficiency and quality-guaranteed welding of the Q420 high-strength steel thick plate to be possible.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (6)
1. A submerged arc welding process of a Q420 high-strength steel thick plate by a flux copper backing method is characterized by comprising the following steps of:
step 1, processing a Y-shaped welding groove at a welding position of a steel plate to be welded, wherein the steel plate to be welded is a Q420 high-strength steel thick plate, and the corresponding parameters of the Y-shaped welding groove are as follows: the angle of the groove is 43-47 degrees, the truncated edge is 5-7mm, and the root gap is 0-1 mm; after the machining is finished, cleaning oxide layers and impurities on the Y-shaped welding bevel face and the periphery of the Y-shaped welding groove within the range of 20-30 mm;
step 2, welding a positioning welding line by adopting a semi-automatic CO2 gas shielded welding mode, wherein the thickness of the positioning welding line is 4-5mm, the length of the positioning welding line is 50-60mm, and the distance between the welding lines is 400-500 mm;
step 3, respectively welding an arc striking plate and an arc quenching plate at two ends of the Y-shaped welding groove in a semi-automatic CO2 gas shielded welding mode; the material, thickness and groove size of the arc striking plate and the arc extinguishing plate are the same as those of the welding plate;
step 4, welding stepped restrained welding lines at two ends of the welding groove, wherein:
the initial end of the welding line is restrained by the welding line and welded into two layers: the length of the first layer of welding line from the initial end of the steel plate to be welded is 150-170mm, and the length of the second layer of welding line from the initial end of the steel plate to be welded is 50-70 mm;
the welding seam terminal restrains the welding seam and welds five layers: the first layer of welding line distance is 350-360mm in length of the terminal of the steel plate to be welded, the second layer of welding line distance is 330-340mm in length of the terminal of the steel plate to be welded, the third layer of welding line distance is 310-320mm in length of the terminal of the steel plate to be welded, the fourth layer of welding line distance is 290-300mm in length of the terminal of the steel plate to be welded, and the fifth layer of welding line distance is 270-280mm in length of the terminal of the steel plate to be welded;
step 5, the FCB welding material adopts a welding wire, a surface flux and a back flux which meet the requirements of CCS classification 3Y 42; the L-pole welding wire is a solid welding wire with the diameter specification of 4.8mm, the T1-pole welding wire is a solid welding wire with the diameter specification of 4.8mm, and the T2-pole welding wire is a solid welding wire with the diameter specification of 6.4 mm;
step 6, adding the dried surface flux into a flux hopper in advance, and keeping the temperature of the flux hopper at 75-85 ℃;
step 7, cleaning slag and impurities on the surface of the copper gasket, and then spreading back face welding flux on the copper gasket, wherein the spreading thickness is 5-6 mm, and the width is 100-120 mm; after the spreading is finished, the copper gasket is centered in the center of the groove and then is attached to the back of the welding groove, and then the copper gasket is knocked within 100mm of the two sides of the groove on the surface of the steel plate to be welded so that the back welding flux can be closely attached to the back of the steel plate to be welded;
step 8, centering each electrode, welding the center of the groove, and adjusting the angle and the distance of a welding gun, wherein: the L pole is inclined forward by 13 degrees, and the distance from the contact tip to the workpiece is 35 mm; the T1 pole is inclined forward by 0 DEG, and the distance from the contact tip to the workpiece is 40 mm; t2 inclining backward by 3 degrees, the distance from the contact tip to the workpiece is 45 mm; the distance between the L pole and the T1 pole is 35mm, and the distance between the T1 pole and the T2 pole is 130 mm; then adjusting the welding head to the position of an arc striking plate, placing arc striking cotton at the end part of the welding wire, opening a surface flux hopper switch to place lower surface flux, and starting welding;
monitoring the welding process, carrying out fine adjustment on welding parameters in time according to the welding state, and carrying out arc quenching and stopping welding after a welding head is welded to an arc quenching plate;
step 9, after welding, moving the steel plate to be welded to a repairing station, performing gouging cleaning on the incomplete penetration defect of the restrained weld positions of the arc starting end and the arc ending end, polishing a gouging groove by adopting a mechanical polishing mode, and performing repair welding on the gouging groove by adopting a semi-automatic CO2 gas shielded welding overhead welding mode; and after the repair welding of the gouging groove is finished, mechanically polishing the surface of the repair welding seam in a mechanical polishing mode to ensure that the repair welding seam can be smoothly transited with the periphery.
2. The submerged arc welding process of the welding flux copper backing method for the Q420 high-strength steel thick plate as claimed in claim 1, wherein in the step 2, the step 3 and the step 4, when welding is carried out, the adopted flux-cored wire meets the regulation requirement of E81T1-K2CJ in AWS A5.29 standard.
3. The submerged arc welding process of the flux copper backing method for the Q420 high-strength steel thick plate according to the claim 1, characterized in that in the step 4, when the weld joint is restrained, the arc is initiated in the formal slope of the steel plate to be welded, and the arc is withdrawn in the arc initiating plate and the arc quenching plate.
4. The submerged arc welding process of the welding flux copper gasket method for the Q420 high strength steel thick plate according to the claim 1, wherein in the step 7, when the copper gasket is centered at the center of the groove and is tightly attached to the back surface of the welding groove, the air pressure of the pressure hose in the gasket device is set to be 0.10MPa-0.12 MPa.
5. The process of submerged arc welding of Q420 high strength steel thick plate by flux copper backing method according to claim 1, wherein in step 8, during welding, the power supply characteristics of L pole, T1 pole and T2 pole are all selected as AC characteristics, the welding speed is set as 36cm/min, and the welding parameters of each electrode are set as:
l pole: the welding current 1430-;
t1 pole: welding current 1280-1320A, welding voltage 39-41V;
t2 pole: the welding current is 1280-1320A, and the welding voltage is 45-47V.
6. The submerged arc welding process of the Q420 high-strength steel thick plate by the flux copper backing method according to claim 1, wherein the thickness of the Q420 high-strength steel thick plate is 38-40 mm.
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