CN114211110A - Laser welding method for improving toughness of welding seam - Google Patents
Laser welding method for improving toughness of welding seam Download PDFInfo
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- CN114211110A CN114211110A CN202111655786.7A CN202111655786A CN114211110A CN 114211110 A CN114211110 A CN 114211110A CN 202111655786 A CN202111655786 A CN 202111655786A CN 114211110 A CN114211110 A CN 114211110A
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- 238000003466 welding Methods 0.000 title claims abstract description 218
- 238000000034 method Methods 0.000 title claims abstract description 51
- 239000007789 gas Substances 0.000 claims abstract description 92
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 81
- 239000010959 steel Substances 0.000 claims abstract description 81
- 230000001681 protective effect Effects 0.000 claims abstract description 28
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 26
- 230000001590 oxidative effect Effects 0.000 claims abstract description 20
- 239000011261 inert gas Substances 0.000 claims abstract description 18
- 239000001301 oxygen Substances 0.000 claims abstract description 13
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 13
- 238000007664 blowing Methods 0.000 claims description 24
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 14
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 12
- 229910052786 argon Inorganic materials 0.000 claims description 12
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 11
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 10
- 239000001569 carbon dioxide Substances 0.000 claims description 5
- 229910052734 helium Inorganic materials 0.000 claims description 5
- 239000001307 helium Substances 0.000 claims description 5
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 5
- 230000008569 process Effects 0.000 abstract description 18
- 238000004140 cleaning Methods 0.000 abstract description 9
- 239000002131 composite material Substances 0.000 abstract description 8
- 239000011572 manganese Substances 0.000 abstract description 6
- 229910052681 coesite Inorganic materials 0.000 abstract description 4
- 229910052906 cristobalite Inorganic materials 0.000 abstract description 4
- 229910052748 manganese Inorganic materials 0.000 abstract description 4
- 239000000377 silicon dioxide Substances 0.000 abstract description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 abstract description 4
- 229910052682 stishovite Inorganic materials 0.000 abstract description 4
- 229910052905 tridymite Inorganic materials 0.000 abstract description 4
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 abstract description 3
- -1 oxygen ions Chemical class 0.000 abstract description 3
- 230000009471 action Effects 0.000 abstract description 2
- 229910021645 metal ion Inorganic materials 0.000 abstract 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- 229910001563 bainite Inorganic materials 0.000 description 8
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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
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/12—Working by laser beam, e.g. welding, cutting or boring in a special atmosphere, e.g. in an enclosure
- B23K26/123—Working by laser beam, e.g. welding, cutting or boring in a special atmosphere, e.g. in an enclosure in an atmosphere of particular gases
-
- 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
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/20—Bonding
- B23K26/21—Bonding by welding
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Plasma & Fusion (AREA)
- Mechanical Engineering (AREA)
- Laser Beam Processing (AREA)
Abstract
The invention provides a laser welding method for improving the toughness of a high-steel-grade pipeline steel weld joint, belonging to the technical field of welding of high-steel-grade pipeline steel; the method comprises the following steps: cleaning before welding, and removing oil stains on the surface of the high-steel-grade pipeline steel plate; clamping, and fixing by using a welding clamp; selecting proper types and contents of the mixed gas of the protective gas; setting equipment parameters and programming welding of a welding robot; and laser welding, wherein the protective gas is a mixed gas of inert gas and oxidizing active gas. In the laser welding process, oxygen ions decomposed by the oxidative protective gas under the strong ionization action of laser react with metal ions in a laser molten pool to generate Ti2O3‑MnO‑Al2O3‑SiO2The composite inclusion, the poor manganese area produced around the inclusion induces the generation of a large amount of acicular ferrite in the laser welding seam, realizes the obdurability matching of the welding seam, reduces the welding cost and obviously improves the welding efficiency.
Description
Technical Field
The invention belongs to the technical field of laser welding, and particularly relates to a laser welding method for improving the toughness of a welding seam, in particular to a laser welding method for improving the toughness of a welding seam of high-grade pipeline steel by regulating and controlling shielding gas induced acicular ferrite.
Background
As oil and gas surveys are conducted towards the two poles and deep sea, the service environment requires pipeline steel to have higher strength and toughness. Welding is the most common connection method used in pipeline steel laying. In the traditional arc welding (arc welding technologies such as Shielded Metal Arc Welding (SMAW), Gas Metal Arc Welding (GMAW), Submerged Arc Welding (SAW) and the like), because of the limitation of energy density and penetration capacity of arc welding, when welding medium and thick plates, extremely large heat input is often needed or multi-pass welding is often needed, the operation cost is high, the welding efficiency is low, and when multi-pass welding is carried out, the welding seam can experience remelting and reheating effects, so that the tissue distribution of the welding seam is very uneven, and the mechanical properties, especially the low-temperature toughness, of the welding seam are greatly reduced. In addition, the accumulated heat input during the multi-pass welding of arc welding can expand a heat affected zone, coarsen crystal grains of a welding joint, further reduce the mechanical property of the welding joint, particularly obviously reduce the low-temperature impact toughness of the joint relative to a base metal (less than or equal to 10 percent of the impact energy of the base metal), and greatly reduce the safety and the reliability of the pipeline steel. In recent years, with the rapid development of lasers, a high-power laser can realize single-pass penetration of a medium plate, has the advantages of high welding speed, large depth-to-width ratio, small thermal deformation, narrow heat affected zone, high automation degree and the like, and has wide application prospect. The weld serves as an important component of the welded joint, the type of structure of which determines the properties of the weld. It is known that acicular ferrite has positive effects in deflecting the crack propagation direction, hindering crack propagation, improving toughness, etc. due to its characteristics of interlocking structure and grain refinement.
During the laser welding process, inert gas (argon or helium) is mainly applied to prevent the oxidation and burning loss of metal elements in a welding pool, so that the mechanical property of a welding joint is ensured. Meanwhile, at present, the microstructure in the laser welding seam of the high-grade pipeline steel mainly comprises bainite and martensite with poor toughness, and an acicular ferrite welding seam structure with high volume fraction can be generated in the laser welding seam very rarely.
Disclosure of Invention
In view of this, the present invention provides a laser welding method for improving the toughness of a weld, which achieves the toughness of the weld, reduces the welding cost, and significantly improves the welding efficiency.
The invention provides a laser welding method for improving the toughness of a welding seam, which comprises the following steps:
carrying out laser welding on high-grade pipeline steel in the presence of protective gas to induce a welding seam to generate acicular ferrite;
the shielding gas includes:
inert gas and oxidizing reactive gas.
Preferably, the shielding gas further comprises: the air is compressed.
Preferably, the flow rate of the compressed air is 0-40L/min.
Preferably, the compressed air is blown coaxially.
Preferably, the inert gas includes:
argon and/or helium.
Preferably, the oxidizing active gas includes:
carbon dioxide and/or oxygen.
Preferably, the flow rate of the protective gas is 0-45L/min.
Preferably, the blowing method of the oxidizing gas is side blowing.
Preferably, the blowing angle of the side blowing is 0-75 degrees.
Preferably, the volume content of the inert gas in the protective gas is less than or equal to 100 percent.
The invention creatively introduces the mixed gas of inert gas and oxidizing gas in the laser welding process, and the oxidizing gas (CO) is generated under the strong ionization and irradiation of laser2) Oxygen ion by ionizationThe seed reacts with the metal element in the molten pool to generate a great amount of Ti with the size of about 1 μm2O3-MnO-Al2O3-SiO2Composite inclusions; the composite inclusion can absorb manganese ions around 124nm around the composite inclusion to enter the composite inclusion, so that a manganese-poor area is formed in a local area around the inclusion; the manganese-poor area increases the nucleation driving force of the acicular ferrite, so that the laser welding seam of the high-grade pipeline steel generates the acicular ferrite with the volume fraction as high as 92 percent. Active gas is added in the welding process, the density of impurities in weld metal is improved by 4 times compared with pure inert gas, and the impact energy is improved by more than 8 times; this is mainly due to the fact that the laser is more focused than the arc energy and ionizes the oxidizing gas more thoroughly. In addition, the problem of argon holes existing in the process of welding a thick plate by a laser can be well solved by introducing the oxidizing gas, so that the welding quality of a welding line is greatly improved, and the reliability of a welding joint is improved. The invention can realize the generation of effective inclusions in the laser welding seam area of the high-grade pipeline steel so as to successfully induce the formation of acicular ferrite, and has the advantages of simple operation, high operation efficiency, good quality of welding joints and reduced welding and production cost compared with the welding mode adopting arc welding.
Drawings
FIG. 1 is a flow chart of laser welding according to an embodiment of the present invention;
FIG. 2 is a metallographic structure diagram of X100 pipeline steel in an example of the present invention;
FIG. 3 is a metallographic structure diagram of a laser welded joint obtained in example 1 of the present invention;
FIG. 4 is a metallographic structure diagram of a laser welded joint obtained in example 2 of the present invention;
FIG. 5 is a metallographic structure diagram of a laser welded joint obtained in example 3 of the present invention;
FIG. 6 is a composition distribution diagram of inclusions in a laser weld obtained in example 3 of the present invention;
FIG. 7 is a metallographic structure diagram of a laser welded joint obtained in comparative example 1 of the present invention;
FIG. 8 is a composition distribution diagram of inclusions in a laser weld obtained in comparative example 1 of the present invention;
FIG. 9 is a statistical chart of the impact work at-40 ℃ of the weld joints obtained in examples 1 to 3 and comparative example 1 (the dotted line is the impact work of the base metal at-40 ℃);
FIG. 10 is a stress-strain statistical graph of the weld joints obtained in examples 1-3 and comparative example 1 (wherein the dotted line is the strength requirement of the national standard for X100 pipeline steel:. gtoreq.760 MPa).
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all 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 invention provides a laser welding method for improving the toughness of a welding seam, which comprises the following steps:
and in the presence of protective gas, carrying out laser welding on the high-grade pipeline steel to induce a welding seam to generate acicular ferrite.
In an embodiment of the present invention, a process flow diagram of the laser welding method is shown in fig. 1.
In the present invention, the shielding gas includes:
inert gas and oxidizing reactive gas.
In the present invention, the inert gas is preferably selected from argon and/or helium.
In the present invention, the oxidizing active gas is preferably selected from carbon dioxide and/or oxygen.
In the present invention, the shielding gas is preferably two, three or four combinations of argon, helium, carbon dioxide and oxygen, and the shielding gas must contain an inert gas.
In the present invention, the volume content of the inert gas in the shielding gas is preferably less than or equal to 100%, more preferably 10% to 90%, more preferably 20% to 80%, more preferably 30% to 70%, more preferably 40% to 60%, and most preferably 50% to 60%.
In the present invention, when the oxidizing active gas is carbon dioxide, the volume content of the oxidizing active gas in the protective gas is preferably 15 to 100%, more preferably 20 to 90%, more preferably 30 to 80%, more preferably 40 to 70%, and most preferably 50 to 60%.
In the present invention, when the oxidizing active gas is oxygen, the volume content in the protective gas is preferably 20% or less, more preferably 1% to 20%, more preferably 5% to 15%, and most preferably 10% to 15%.
In the invention, when the protective gas comprises inert gas and oxidizing active gas, the blowing mode in the laser welding process is preferably side blowing; the gas flow rate is preferably 0 to 45L/min, more preferably 5 to 40L/min, more preferably 10 to 35L/min, more preferably 15 to 30L/min, and most preferably 20 to 25L/min.
In the invention, when side-blown protective gas is carried out in the laser welding process, the blowing angle is preferably 0-75 degrees, more preferably 5-70 degrees, more preferably 10-60 degrees, more preferably 20-50 degrees, and most preferably 30-40 degrees; the preferable horizontal distance between the blowing position of the protective gas and the laser spot is 2-25 mm, more preferably 5-20 mm, and most preferably 10-15 mm.
In the present invention, the shielding gas preferably further comprises: the air is compressed.
In the invention, the volume content of nitrogen in the compressed air is preferably 75-85%, more preferably 78-82%, and most preferably 79%; the volume content of oxygen in the compressed air is preferably 15-25%, more preferably 18-22%, and most preferably 19%.
In the invention, when the protective gas comprises compressed air, the blowing mode in the laser welding process is preferably coaxial blowing; the gas flow is preferably 0 to 40L/min, more preferably 5 to 35L/min, more preferably 10 to 30L/min, more preferably 15 to 25L/min, and most preferably 20L/min.
In the present invention, the protective gas preferably includes: inert gases and oxidizing reactive gases, and compressed air.
In the present invention, it is preferable that an inert gas and an oxidizing active gas, and compressed air are blown simultaneously during the laser welding; the blowing mode of the inert gas and the oxidation active gas is side blowing; the compressed air is blown coaxially to protect the laser lens from splash contamination.
In the invention, the high-grade pipeline steel comprises the following components:
0.035-0.045 wt% of C;
0.2 to 0.3 wt% of Si;
1.5-2.5 wt% Mn;
0.0025 to 0.0030 wt% of Al;
0.01 to 0.02 wt% of Ti;
0.2 to 0.3 wt% of Ni;
0.2 to 0.3 wt% of Cr;
0.15 to 0.25 wt% Cu;
0.15 to 0.25 wt% of Mo;
0.06-0.07 wt% of Nb;
the balance being Fe.
In the invention, the mass content of C is preferably 0.038-0.042%, and more preferably 0.041%; the mass content of Si is preferably 0.23-0.27%, and more preferably 0.25%; the mass content of Mn is preferably 1.8-2.2%, and more preferably 1.87%; the mass content of the Al is preferably 0.0026-0.0029%, and more preferably 0.0027-0.0028%; the mass content of Ti is preferably 0.012-0.018%, more preferably 0.014-0.016%; the mass content of the Ni is preferably 0.23-0.27%, and more preferably 0.25%; the mass content of Cr is preferably 0.23-0.27%, and more preferably 0.25%; the mass content of Cu is preferably 0.18-0.22%, and more preferably 0.2%; the mass content of Mo is preferably 0.18-0.22%, and more preferably 0.2%; the mass content of Nb is preferably 0.061-0.064%, and more preferably 0.062-0.063%.
In the invention, the high-grade pipeline steel is preferably a plate; the thickness of the plate is preferably 5-50 mm, more preferably 10-40 mm, and most preferably 20-30 mm.
In the invention, the surface of the high-grade pipeline steel is preferably cleaned before the laser welding; the washing reagent preferably comprises acetone or absolute ethanol.
In the invention, before the laser welding, the high-grade pipeline steel is preferably placed on a welding workbench and fixed by a welding fixture.
In the invention, in the laser welding process, the laser parameter setting and the robot welding programming are preferably carried out, and the robot laser welding program is compiled and the target point is taught according to the welding path, the welding sequence and the welding direction.
In the invention, in the laser welding process, single-pass laser welding can be carried out according to the thickness of the high-grade pipeline steel, and front and back alternate welding can also be carried out, wherein the alternate welding is preferably 1-6-pass laser welding, more preferably 2-5-pass laser welding, and most preferably 3-4-pass laser welding.
In the invention, when welding high-grade pipeline steel in the laser welding process, a groove is preferably not formed, the welding is performed in a horizontal butt joint mode, and a laser tailor welding mode is adopted for welding.
In the present invention, the laser in the laser welding process is preferably selected from a fiber laser, CO2One of a laser and a semiconductor laser; the laser welding mode is preferably one selected from the group consisting of continuous laser welding, pulsed laser welding and oscillatory laser welding; the welding mode is preferably one selected from overhead welding, flat welding, vertical up welding, vertical down welding, inner welding, outer welding and ring welding.
In the invention, the included angle between the laser direction and the vertical axis direction of the high-grade steel pipeline steel in the laser welding process is preferably 0-15 degrees, more preferably 5-10 degrees, and most preferably 6-8 degrees.
In the present invention, the parameters in the laser welding process are set as follows: the laser power is preferably 300W-20 kW, more preferably 1-15 kW, more preferably 5-10 kW, and most preferably 6-8 kW; the welding speed is preferably 10-40 m/min, more preferably 50-30 m/min, more preferably 1-20 m/min, more preferably 5-15 m/min, more preferably 8-12 m/min, and most preferably 10 m/min; the defocusing amount is preferably-20-10 mm, more preferably-15-5 mm, and most preferably-10-1 mm; the diameter of the light spot is preferably 0.1-6 mm, more preferably 0.3-4 mm, more preferably 0.6-2 mm, and most preferably 0.8-1 mm.
In the invention, the metallographic structure of the welding seam is mainly acicular ferrite, the volume fraction of the acicular ferrite structure in the metallographic structure is more than or equal to 80%, and the rest is a mixed structure of granular bainite, lath bainite, martensite and martensite in any proportion.
The invention provides a laser welding method for improving the toughness of a high-grade pipeline steel weld joint by regulating and controlling protective gas to induce acicular ferrite2O3-MnO-Al2O3-SiO2Composite inclusions; the lean manganese zone generated around the inclusion induces the generation of a large amount of acicular ferrite in the laser welding seam, thereby realizing the obdurability matching of the welding seam, reducing the welding cost and obviously improving the welding efficiency.
Example 1
A laser welding method for enhancing the strength and toughness of a high-steel-grade pipeline steel weld joint comprises the following steps:
cleaning before welding, namely cleaning the surface of a high-steel-grade pipeline steel workpiece with oil stains by using organic liquid;
step (2), clamping, namely placing the high-steel-grade pipeline steel workpiece processed in the step (1) on a welding workbench and fixing the high-steel-grade pipeline steel workpiece by using a welding fixture;
selecting proper types and contents of the protective gas mixed gas;
step (4), setting laser parameters and programming robot welding, compiling a robot laser welding program according to a welding path, a welding sequence and a welding direction, and teaching a target point;
and (5) performing laser welding on the high-grade pipeline steel, inducing the welding seam to generate Acicular ferrite (Acicular ferrite), and performing a pendulum impact test and a tensile test on the welding seam.
Removing oil stains on the surface of a high-steel-grade pipeline steel plate by adopting absolute ethyl alcohol; step (2) assembling two high-grade steel pipeline steel plates on a welding fixture, wherein the two high-grade steel pipeline steel plates are arranged between the two high-grade steel pipeline steel platesThe gap between the two grooves is 0mm, and no groove is formed; the protective gas in the step (3) is 80% Ar + 20% CO2(volume percentage) of mixed gas, the gas flow is 30L/min, side-blown protective gas is adopted, the blowing angle is 15 degrees, and the horizontal distance between the blowing position and the laser facula is about 15 mm; meanwhile, compressed air is selected, wherein the volume content of oxygen is 21%, the volume content of nitrogen is 79%, the compressed air is blown coaxially, the gas flow is 30L/min, and the laser lens is protected from being polluted by splashing; and (4) and (5) performing laser tailor-welding on the two high-steel-grade pipeline steel plates by using an CWX-3KW optical fiber laser, wherein the welding power is 3000W, the welding speed is 30cm/min, the defocusing amount is 0mm, and the diameter of a light spot is 0.30 mm.
In example 1, the thickness of both high-grade pipeline steel plates is 6mm, the model is X100, the strength grade is 700MPa, the structure of the high-grade pipeline steel plate is granular bainite, as shown in figure 2, and the components of the high-grade pipeline steel are shown in Table 1.
After welding, cutting a 20 multiplied by 5 multiplied by 6mm metallographic specimen of the welding specimen by a numerical control wire cutting machine, and observing the metallographic specimen by an Olympus-X53 metallographic microscope after inlaying, grinding, polishing and corroding to obtain a metallographic structure of the laser welding seam shown in the figure 3; the structure of the acicular ferrite of the off-white elongated strip is clearly seen in fig. 3.
After welding, the welding sample is processed into an impact sample with the size of 55 multiplied by 10 multiplied by 4mm, a V groove is processed at the welding seam by a broach, a low-temperature impact experiment is carried out on the sample under the condition of minus 40 ℃, the detection result (the statistical result of the impact power of different shielding gases) is shown in figure 9, and the impact power of the welding seam at minus 40 ℃ is along with the CO in the shielding gas2The increase in the content showed an upward trend, 20% CO2The work of impact was 14J.
After welding, the welded sample is processed into a tensile sample, a tensile test is carried out on a universal drawing machine (according to the standard GB/T228.1-2010), the tensile speed is 3mm/min, and the detection result (tensile statistical result) is shown in FIG. 10, which shows that the test result is along with CO in the shielding gas2The content is increased, and the strength of the welding seam is 20 percent CO2The maximum value of 775MPa is achieved, and the requirement that the strength of the pipeline steel is more than or equal to 760MPa is met.
Example 2
A laser welding method for enhancing the strength and toughness of a high-steel-grade pipeline steel weld joint comprises the following steps:
cleaning before welding, namely cleaning the surface of a high-steel-grade pipeline steel workpiece with oil stains by using organic liquid;
step (2), clamping, namely placing the high-steel-grade pipeline steel workpiece processed in the step (1) on a welding workbench and fixing the high-steel-grade pipeline steel workpiece by using a welding fixture;
selecting proper types and contents of the protective gas mixed gas;
step (4), setting laser parameters and programming robot welding, compiling a robot laser welding program according to a welding path, a welding sequence and a welding direction, and teaching a target point;
and (5) performing laser welding on the high-grade pipeline steel, inducing the welding seam to generate Acicular ferrite (Acicular ferrite), and performing a pendulum impact test and a tensile test on the welding seam.
Removing oil stains on the surface of a high-steel-grade pipeline steel plate by adopting absolute ethyl alcohol; assembling two high-steel-grade pipeline steel plates on a welding fixture, wherein the gap between the two plates is 0mm, and no groove is formed; step (3) selects 40% Ar + 60% CO2The gas flow of the mixed gas (volume percentage content) is 30L/min, side-blown protective gas is adopted, the blowing angle is 15 degrees, and the horizontal distance between the blowing position and the laser facula is about 15 mm; meanwhile, compressed air is selected, wherein the volume content of oxygen is 21%, the price-raising content of nitrogen is 79%, coaxial blowing is carried out, the gas flow is 30L/min, and the laser lens is protected from being polluted by splashing; and (4) and (5) performing laser tailor-welding on the two high-steel-grade pipeline steel plates by using an CWX-3KW optical fiber laser, wherein the welding power is 3000W, the welding speed is 30cm/min, the defocusing amount is 0mm, and the diameter of a light spot is 0.30 mm.
The thickness of the two high-grade pipeline steel plates in the embodiment 2 is 6mm, the model is X100, the strength grade is 700MPa, the structure of the high-grade pipeline steel plate is granular bainite, as shown in figure 2, and the components of the high-grade pipeline steel are shown in Table 1.
After welding, cutting a 20 multiplied by 5 multiplied by 6mm metallographic specimen of the welding specimen by using a numerical control wire cutting machine, and observing the metallographic specimen by using an Olympus-X53 metallographic microscope after inlaying, grinding, polishing and corroding to obtain a metallographic structure of the laser welding seam shown in the figure 4; the structure of the acicular ferrite of the off-white elongated strip is clearly seen in fig. 4.
After welding, the welded sample was processed into an impact specimen having a size of 55X 10X 4mm, a V groove was formed in the weld by a broach, and a low-temperature impact test of the sample was carried out at-40 ℃ (the same as in example 1), and the test results are shown in FIG. 9, where the impact energy of the weld was measured by CO in a shielding gas at-40 ℃2The increase in the content showed an upward trend, 60% CO2The impact work was 27J.
After the welding, the welded sample was processed into a tensile sample, and a tensile test was carried out on a universal tensile machine (the same test method as in example 1) at a tensile speed of 3mm/min, and the test results are shown in FIG. 10, which shows that CO contained in the shielding gas was included in the test results2The content is increased, and the strength of a welding seam is 60 percent CO2The maximum pressure is 800MPa under the condition, and the requirement that the strength of the pipeline steel is more than or equal to 760MPa is met.
Example 3
A laser welding method for enhancing the strength and toughness of a high-steel-grade pipeline steel weld joint comprises the following steps:
cleaning before welding, namely cleaning the surface of a high-steel-grade pipeline steel workpiece with oil stains by using organic liquid;
step (2), clamping, namely placing the high-steel-grade pipeline steel workpiece processed in the step (1) on a welding workbench and fixing the high-steel-grade pipeline steel workpiece by using a welding fixture;
selecting proper types and contents of the protective gas mixed gas;
step (4), setting laser parameters and programming robot welding, compiling a robot laser welding program according to a welding path, a welding sequence and a welding direction, and teaching a target point;
and (5) performing laser welding on the high-grade pipeline steel, inducing the welding seam to generate Acicular ferrite (Acicular ferrite), and performing a pendulum impact test and a tensile test on the welding seam.
Removing oil stains on the surface of a high-steel-grade pipeline steel plate by adopting absolute ethyl alcohol; assembling two high-steel-grade pipeline steel plates on a welding fixture, wherein the gap between the two plates is 0mm, and no groove is formed; selecting 100% CO in step (3)2The gas flow of the protective gas is 30L/min, the protective gas is blown laterally, the blowing angle is 15 degrees, and the horizontal distance between the blowing position and the laser facula is about 15 mm; meanwhile, compressed air is selected, wherein the volume content of oxygen is 21%, the volume content of nitrogen is 79%, the compressed air is blown coaxially, the gas flow is 30L/min, and the laser lens is protected from being polluted by splashing; and (4) and (5) performing laser tailor-welding on the two high-steel-grade pipeline steel plates by using an CWX-3KW optical fiber laser, wherein the welding power is 3000W, the welding speed is 30cm/min, the defocusing amount is 0mm, and the diameter of a light spot is 0.30 mm.
In example 3, the thickness of both high-grade pipeline steel plates is 6mm, the model is X100, the strength grade is 700MPa, the structure of the high-grade pipeline steel plate is granular bainite, as shown in figure 2, and the components of the high-grade pipeline steel are shown in Table 1.
After welding, cutting a 20 multiplied by 5 multiplied by 6mm metallographic specimen of the welding specimen by a numerical control wire cutting machine, and observing the metallographic specimen by an Olympus-X53 metallographic microscope after inlaying, grinding, polishing and corroding to obtain a metallographic structure of the laser welding seam shown in the figure 5; the structure of the acicular ferrite of the off-white elongated strip is clearly seen in fig. 5.
After welding, the welded sample was processed into an impact specimen having a size of 55X 10X 4mm, a V groove was formed in the weld by a broach, and a low-temperature impact test was performed on the specimen at-40 ℃ (the test method was the same as in example 1), and the test results are shown in FIG. 9, where the impact energy of the weld was measured by CO in a shielding gas at-40 ℃2The increase in the content showed an upward trend, 100% CO2The impact energy is 28.7J, reaching 72 percent of the base material.
After the welding, the welded sample was processed into a tensile sample, and a tensile test was carried out on a universal tensile machine (the test method was the same as in example 1), the tensile rate was 3mm/min, and the test results are shown in FIG. 10, which shows that CO contained in the shielding gas was involved in the test2The content is increased, and the strength of the welding seam is 100 percent CO2The maximum pressure of the steel reaches 795MPa, and the requirement that the strength of the pipeline steel is more than or equal to 760MPa is met.
Comparative example 1
A laser welding method for enhancing the strength and toughness of a high-steel-grade pipeline steel weld joint comprises the following steps:
cleaning before welding, namely cleaning the surface of a high-steel-grade pipeline steel workpiece with oil stains by using organic liquid;
step (2), clamping, namely placing the high-steel-grade pipeline steel workpiece processed in the step (1) on a welding workbench and fixing the high-steel-grade pipeline steel workpiece by using a welding fixture;
selecting proper types and contents of the protective gas mixed gas;
step (4), setting laser parameters and programming robot welding, compiling a robot laser welding program according to a welding path, a welding sequence and a welding direction, and teaching a target point;
and (5) performing laser welding on the high-grade pipeline steel, inducing the welding seam to generate Acicular ferrite (Acicular ferrite), and performing a pendulum impact test and a tensile test on the welding seam.
Removing oil stains on the surface of a high-steel-grade pipeline steel plate by adopting absolute ethyl alcohol; assembling two high-steel-grade pipeline steel plates on a welding fixture, wherein the gap between the two plates is 0mm, and no groove is formed; selecting 100% Ar (volume percentage) protective gas, wherein the gas flow is 30L/min, adopting side-blown protective gas, the blowing angle is 15 degrees, and the horizontal distance between the blowing position and the laser facula is about 15 mm; meanwhile, compressed air is selected, wherein the volume content of oxygen is 21%, the price-raising content of nitrogen is 79%, coaxial blowing is carried out, the gas flow is 30L/min, and the laser lens is protected from being polluted by splashing; and (4) and (5) performing laser tailor-welding on the two high-steel-grade pipeline steel plates by using an CWX-3KW optical fiber laser, wherein the welding power is 3000W, the welding speed is 30cm/min, the defocusing amount is 0mm, and the diameter of a light spot is 0.30 mm.
The two high-grade pipeline steel plates in the comparative example 1 have the thickness of 6mm, the model is X100, the strength grade is 700MPa, the structure of the high-grade pipeline steel plate is granular bainite, as shown in figure 2, and the components of the high-grade pipeline steel are shown in Table 1.
After welding, cutting a 20 multiplied by 5 multiplied by 6mm metallographic specimen of the welding specimen by using a numerical control wire cutting machine, and observing the metallographic specimen by using an Olympus-X53 metallographic microscope after inlaying, grinding, polishing and corroding to obtain a metallographic structure of the laser welding seam shown in the figure 7; the granular bainite structure is clearly seen in fig. 7.
After welding, the welded sample was processed into an impact specimen having a size of 55X 10X 4mm, a V groove was formed in the weld by a broach, and a low-temperature impact test of the sample was carried out at-40 ℃ (the same as in example 1), and the test results are shown in FIG. 9, where the impact energy of the weld was measured by CO in a shielding gas at-40 ℃2The reduction in the content showed a significant tendency to decrease, with a 100% Ar work of 5J.
After welding, the welded sample is processed into a tensile sample, a tensile test is carried out on a universal drawing machine (the method is the same as the detection method in the embodiment 1), the tensile speed is 3mm/min, the detection result is shown in figure 10, and the figure shows that the strength of the welding line is 792MPa under the condition of 100% Ar, and the requirement that the strength of the pipeline steel is more than or equal to 760MPa is met.
In the laser welding process of comparative example 1, under the strong ionization and irradiation of laser, a large amount of Al of about 2 μm in size is generated in the 100% Ar weld2O3-Ti2O3Composite inclusions, as shown in fig. 8; and no needle-like ferrite is generated, so that the weld joint is subjected to brittle fracture at the temperature of minus 40 ℃, and the low-temperature toughness of the weld joint is greatly reduced.
TABLE 1 chemical composition of high grade steel pipeline steel in the examples
| Composition (I) | C | Si | Mn | Al | Ti | Ni | Cr | Cu | Mo | Nb | Fe |
| Mass percent | 0.041 | 0.25 | 1.87 | 0.0027 | 0.014 | 0.25 | 0.25 | 0.20 | 0.20 | 0.063 | Bal. |
In the laser welding process of the invention, under the action of strong ionization and irradiation of laser, oxidizing gas (CO) in mixed gas2) Oxygen ions generated by ionization react with metal elements in the molten pool to generate Ti with a large amount of about 1 μm2O3-MnO-Al2O3-SiO2Composite inclusions, as shown in fig. 6; acicular ferrite with the volume fraction as high as 92 percent is generated in the induced laser welding line of the poor manganese area generated around the inclusion, the obdurability matching of the welding line is realized, and the method has the advantages of simple operation, high operation efficiency, good quality of the welding joint and reduction of welding and production cost. The laser has the advantages of high energy density, high welding speed, small heat input, small deformation, high welding efficiency and the like, so that the laser is narrower than an arc welding heat affected zone, and the structure is refined. According to the invention, the laser welding is carried out on the high-steel-grade pipeline steel by using the mixed shielding gas, so that the low-temperature toughness of the laser welding seam is improved by more than 8 times, and the method has certain engineering significance.
While the invention has been described and illustrated with reference to specific embodiments thereof, such description and illustration are not intended to limit the invention. It will be clearly understood by those skilled in the art that various changes in form and details may be made therein without departing from the true spirit and scope of the invention as defined by the appended claims, to adapt a particular situation, material, composition of matter, substance, method or process to the objective, spirit and scope of this application. All such modifications are intended to be within the scope of the claims appended hereto. Although the methods disclosed herein have been described with reference to particular operations performed in a particular order, it should be understood that these operations may be combined, sub-divided, or reordered to form equivalent methods without departing from the teachings of the present disclosure. Accordingly, unless specifically indicated herein, the order and grouping of the operations is not a limitation of the present application.
Claims (10)
1. A laser welding method for improving the toughness of a weld, comprising:
carrying out laser welding on high-grade pipeline steel in the presence of protective gas to induce a welding seam to generate acicular ferrite;
the shielding gas includes:
inert gas and oxidizing reactive gas.
2. The method of claim 1, wherein the shielding gas further comprises:
the air is compressed.
3. The method according to claim 2, wherein the flow rate of the compressed air is 0 to 40L/min.
4. The method of claim 2, wherein the compressed air is blown coaxially.
5. The method of claim 1, wherein the inert gas comprises:
argon and/or helium.
6. The method of claim 1, wherein the oxidizing active gas comprises:
carbon dioxide and/or oxygen.
7. The method according to claim 1, wherein the flow rate of the shielding gas is 0 to 45L/min.
8. The method of claim 1, wherein the blowing of the shielding gas is side blowing.
9. The method according to claim 8, wherein the blow angle of the side blow is 0-75 °.
10. The method according to claim 1, wherein the inert gas is present in the protective gas in an amount of 100% by volume or less.
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| WO2023123735A1 (en) * | 2021-12-30 | 2023-07-06 | 苏州大学 | Laser welding method for improving strength and toughness of weld joint |
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| JP4492028B2 (en) * | 2001-11-02 | 2010-06-30 | Ｊｆｅスチール株式会社 | Laser beam welded joint and method for manufacturing laser beam welded joint |
| JP2011206777A (en) * | 2010-03-29 | 2011-10-20 | Jfe Steel Corp | Laser welded joint and laser welding method of steel material excellent in toughness of weld metal part |
| CN104588882B (en) * | 2014-12-09 | 2017-01-11 | 上海航天精密机械研究所 | laser welding machine with inert gas protection system |
| CN110539076B (en) * | 2019-09-19 | 2022-03-22 | 玛斯特轻量化科技(天津)有限公司 | Protective gas for laser welding and laser welding method using same |
| CN114211110A (en) * | 2021-12-30 | 2022-03-22 | 苏州大学 | Laser welding method for improving toughness of welding seam |
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| BE731507A (en) * | 1968-04-27 | 1969-09-15 | ||
| JP2002316283A (en) * | 2001-02-16 | 2002-10-29 | Kawasaki Steel Corp | Method of manufacturing extra-low-carbon steel welded joint having excellent welded joint toughness |
| CN106238915A (en) * | 2016-08-25 | 2016-12-21 | 苏州大学 | A kind of laser assembly solder method of titanium microalloying carbon manganese steel |
| CN109530920A (en) * | 2018-11-30 | 2019-03-29 | 东北大学 | A kind of Hi-grade steel pipe line steel laser-MAG compound welding method |
| CN110202241A (en) * | 2019-07-02 | 2019-09-06 | 苏州大学 | A kind of Hi-grade steel pipeline steel tube welding procedure and welding point |
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