CN108453384B - Method for reducing softening degree of laser welding joint of manganese steel in high strength-elongation product - Google Patents
Method for reducing softening degree of laser welding joint of manganese steel in high strength-elongation product Download PDFInfo
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- CN108453384B CN108453384B CN201810257705.XA CN201810257705A CN108453384B CN 108453384 B CN108453384 B CN 108453384B CN 201810257705 A CN201810257705 A CN 201810257705A CN 108453384 B CN108453384 B CN 108453384B
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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
- B23K26/20—Bonding
- B23K26/21—Bonding by 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
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/36—Removing material
- B23K26/40—Removing material taking account of the properties of the material involved
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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
- B23K26/60—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
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/70—Auxiliary operations or equipment
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Abstract
The invention belongs to the technical field of welding and postweld heat treatment, and particularly relates to a method for reducing the softening degree of a laser welding joint of high-strength-elongation medium manganese steel, which comprises the following chemical components in percentage by weight: 0.05-0.45 wt.% of C, 4.50-8.00 wt.% of Mn, 0.01-2.50 wt.% of Si, Al: 0-3.00 wt%, P is less than or equal to 0.02 wt%, S is less than or equal to 0.02 wt%, Nb is 0-0.02 wt%, V is 0-0.30 wt%, Ti is 0-0.30 wt%, and the balance is Fe and inevitable impurity elements; the method comprises the following steps: the welding process comprises the following steps: b. carrying out laser welding after butting the high-strength plastic-product medium manganese steel, adopting a single-side welding and double-side forming process, welding the laser welding power at 2-4 kW and the welding speed at 1.2-4.8/min, and adopting a deep fusion welding mode to weld; c. and cooling the back surface of the welding steel in the welding process. According to the invention, the high-strength-product medium manganese steel plate for the automobile is adopted to carry out a laser welding test, the laser power and the welding speed are higher, the technological parameters are reasonably adjusted, the width of a heat affected zone is reduced, and the softening degree of the heat affected zone of a welding joint is effectively reduced.
Description
Technical Field
The invention belongs to the technical field of welding and postweld heat treatment, and particularly relates to a method for reducing the softening degree of a laser welding joint of manganese steel in a high strength-elongation product.
Background
In recent years, the automobile industry develops rapidly, the problems of environmental pollution, energy consumption and the like are caused, and the purpose of light weight of automobiles can be met by adopting advanced high-strength plastic product steel in the automobile industry, so that the energy-saving and emission-reducing effects are achieved. The medium manganese steel has wide application prospect as the high-strength-ductility steel which has the most potential and can be used in large quantity in the future. Welding is a key technology for the large-scale application of high-strength high-elongation steel in the automobile industry. The welding methods adopted in the automobile industry at present mainly comprise resistance spot welding, laser welding, tungsten electrode argon arc welding and other technologies.
Compared with resistance spot welding and tungsten electrode argon arc welding, one of the advantages of laser welding is that the weight of the tailor-welded blank can be reduced, the welding speed is greatly increased, and standardized mass production is facilitated. By adopting laser welding, on one hand, a smaller heat affected zone can be obtained under the same heat input condition, and a welding seam with attractive appearance and higher quality can also be obtained; on the other hand, the laser welding can form a tailor-welded blank with a larger plate width. At present, the heat affected zone and the weld zone of a joint are easy to have large texture difference and larger performance difference in the laser welding process of an automobile steel plate, and different areas of the joint have hardening and softening phenomena. At present, automobile steel plates, particularly high-strength dual-phase steel, have softening phenomena of different degrees at joints in the laser welding process, and similar situations occur in the laser welding process of medium manganese steel, and for the situations, domestic and foreign researches mainly focus on adjustment through a traditional heat treatment method. However, in the prior art, a technical scheme for improving the softening problem of the manganese steel joint in the high strength-elongation product with high efficiency and strong applicability is obtained by adjusting the welding process, and has not been reported so far.
Disclosure of Invention
The invention aims to improve the performance of a high-strength-elongation medium manganese steel laser welding joint with application potential in the future, and provides a method for reducing the softening degree of the laser welding joint of the high-strength-elongation medium manganese steel, which is particularly suitable for reducing the softening degree of the laser welding joint of the high-strength-elongation medium manganese steel with the Mn content of 4.50-8.00 wt.% by adjusting the process and improving the performance of the medium manganese steel joint.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a method for reducing the softening degree of a manganese steel laser welding joint in high strength-elongation product,
a. the high-strength-ductility medium manganese steel comprises the following chemical components in percentage by weight: 0.05-0.45 wt.% of C, 4.50-8.00 wt.% of Mn, 0.01-2.50 wt.% of Si, Al: 0-3.00 wt%, P is less than or equal to 0.02 wt%, S is less than or equal to 0.02 wt%, Nb is 0-0.02 wt%, V is 0-0.30 wt%, Ti is 0-0.30 wt%, and the balance is Fe and inevitable impurity elements;
the method comprises the following steps:
the welding process comprises the following steps:
b. the high-strength plastic-product medium manganese steel plates are butted and then subjected to laser welding, a single-side welding and double-side forming process is adopted, the laser welding power is 2-4 kW, the welding speed is 1.2-4.8 m/min, and a deep fusion welding mode is adopted for welding;
c. and in the welding process, cooling the back surface of the welded steel at a cooling speed of 500-45 ℃/s.
And in the step c, a steel plate with the thickness less than or equal to 3mm is placed on the back of the steel plate, and a plate made of red copper is placed on the back of the steel plate for cooling.
And in the step c, a cooling base made of red copper is arranged on the back surface of a steel plate with the thickness of 3-8 mm, and cooling water or liquid nitrogen is introduced into the base from a cooling liquid inlet to be cooled.
In the step b, an I-shaped groove is selected for groove processing of the high-strength-plastic-product medium manganese steel plate; the butt joint clearance is 0.1mm, before welding, the steel plate is polished and scrubbed by acetone, impurities such as oil stains and the like are removed, the steel plate is fixed in a butt joint mode through a proper clamp, and then the steel plate is welded through a fiber laser.
In the step b, during welding, the type of the shielding gas is pure argon, a front and back full protection mode is adopted, and the flow of the front shielding gas is 15L/min.
The high-strength-ductility medium manganese steel comprises the following chemical components in percentage by weight: 0.08-0.45 wt.% of C, 4.50-8.00 wt.% of Mn, 0.01-2.50 wt.% of Si, Al: 0-3.00 wt%, P is less than or equal to 0.02 wt%, S is less than or equal to 0.02 wt%, Nb is 0-0.02 wt%, V is 0-0.30 wt%, Ti is 0-0.30 wt%, and the balance is Fe and inevitable impurity elements.
The width of the heat affected zone of the steel plate with the thickness of 2-8 mm is 0.4-5 mm.
The method is used for reducing the softening degree of the laser welding joint of the high-strength-elongation medium manganese steel, and the method is used for the high-strength-elongation medium manganese steel as an automobile steel plate.
The method for reducing the softening degree of the laser welding joint of the high-strength plastic product medium manganese steel has the following mechanical properties: the tensile strength is 756-819 MPa, and the yield strength is 607-638 MPa.
The invention has the beneficial effects that:
the invention aims at the medium manganese steel, the base material structure of the steel is a ferrite structure and an austenite structure, and the medium manganese steel has higher Mn content than the common low alloy steel, so the hardenability of the steel is higher. The heating and cooling speed is higher in the laser welding heat cycle process, so that the welding is equivalent to a rapid heating and cooling process. The welded seam area is completely constructed into martensite after welding; the structure of the heat affected zone is complex and consists of martensite, ferrite and austenite. The laser power, the welding speed and the cooling speed are improved, and the influence on the structure of the welding line is small. The martensite structure in the heat affected zone is tempered during the slower cooling process, the formation of tempered martensite causes a reduction in hardness and a softening, and therefore increasing the welding speed helps to reduce the tempering degree of the martensite in the heat affected zone. Meanwhile, the improvement of the welding power has obvious influence on the widths of the heat affected zone and the welding seam zone, and the widths of the welding seam zone and the heat affected zone can be optimized to the maximum extent through process improvement, so that a softened area is narrowed, and the softening tendency is reduced.
In the welding process, the back surface of the welding test plate is cooled in a water, air or liquid nitrogen mode, and the cooling speed of a heat affected zone is increased as much as possible, so that the heat affected zone structure does not contain or contains a small amount of tempered martensite structure. According to the invention, the high-strength-plastic-product medium manganese steel is subjected to laser welding, and the width of a welding heat affected zone is effectively reduced by adopting higher power and higher welding speed, so that the tempered martensite structure content in the heat affected zone is reduced, the softening degree can be reduced, and the mechanical property of the high-strength-plastic-product medium manganese steel laser welding joint is improved.
Drawings
FIG. 1 is a schematic view of laser welding of high product of strength and elongation medium manganese steel according to the present invention;
FIG. 2 is a structural morphology diagram of No.2 high product of strength and elongation medium manganese steel laser welded seam area in example 1 of the present invention, the seam area is a martensite structure;
FIG. 3 is a structural morphology diagram of a heat affected zone of No.2 high-strength-ductility medium manganese steel laser welded joint in example 1 of the present invention, wherein the heat affected zone is a mixed structure of martensite, ferrite and austenite;
FIG. 4 shows the hardness of the joint before and after adjustment of the process parameters according to example 1 of the present invention;
FIG. 5 shows the width of the heat-affected zone before and after the adjustment of the process parameters in example 1 of the present invention.
Reference numerals
1 laser beam 2 steel plate 3 protective gas nozzle
4 welding direction 5 bottom cooling medium inlet 6 bottom cooling medium outlet
7 laser beam 8 bottom cooling box
Detailed Description
The technical solution of the present invention is described in detail with reference to the specific examples.
Example 1
The fiber laser is adopted to weld the high-strength-plastic-product medium manganese steel, and the chemical components of the high-strength-plastic-product medium manganese steel used in the embodiment comprise, by weight, 0.08-0.12 wt.% of C, 4.50-6.00 wt.% of Mn, 0.01-2.50 wt.% of Si, Al: 0-3.00 wt%, P is less than or equal to 0.02 wt%, S is less than or equal to 0.02 wt%, Nb is 0-0.02 wt%, V is 0-0.30 wt%, Ti is 0-0.30 wt%, and the balance is Fe and inevitable impurity elements.
Machining a steel plate, wherein the machining size of the manganese steel in the high product of strength and elongation is 150mm multiplied by 75mm multiplied by 2mm, the groove is I-shaped, an IPG-YLS2000 type optical fiber laser is adopted to weld the manganese steel in the high product of strength and elongation, and the welding parameters are as shown:
(1) the laser welding power is 1-2 kW, the welding speed is 1.2 m-4.8/min, and a deep fusion welding mode is adopted for welding. The type of the protective gas is pure argon, a front and back full protection mode is adopted, the flow of the front protective gas is 15L/min, and the back protection mode is different according to the plate thickness.
(2) And in the welding process of the 2mm thin plate, the copper plate made of red copper is adopted as a cooling base for cooling the back of the steel plate.
After laser welding is finished, a sample is sampled, and each tissue and hardness of a joint of the sample are tested, and the result shows that when 1000W laser power is adopted for welding, the heat affected zone of the joint is softened to a certain degree, so that the softening degree of the heat affected zone of the joint can be obviously reduced by improving the welding power and the welding speed, and air holes in a welding line can be effectively avoided.
The welded test piece was subjected to structure observation and basic performance test as shown in the table:
example 2
And welding the other high-strength plastic medium manganese steel by using the fiber laser, wherein the high-strength plastic medium manganese steel used in the embodiment comprises the following chemical components in percentage by weight of 0.15-0.45 wt% of C, 6.00-8.00 wt% of Mn, 0.01-2.50 wt% of Si, Al: 0-3.00 wt%, P is less than or equal to 0.02 wt%, S is less than or equal to 0.02 wt%, Nb is 0-0.02 wt%, V is 0-0.30 wt%, Ti is 0-0.30 wt%, and the balance is Fe and inevitable impurity elements.
Machining a steel plate, wherein the machining size of the manganese steel in the high product of strength and elongation is 150mm multiplied by 75mm multiplied by 3mm, the groove is I-shaped, welding the manganese steel in the high product of strength and elongation by adopting an IPG-YLS2000 optical fiber laser, and the welding parameters are as shown:
(1) the laser welding power is 2-4 kW, the welding speed is 1.2 m-4.8/min, and a deep fusion welding mode is adopted for welding. The type of the protective gas is pure argon, a front and back full protection mode is adopted, the flow of the front protective gas is 15L/min, and the back protection mode is different according to the plate thickness.
(2) In the welding process of the 3mm thin plate, the copper plate made of red copper is adopted as a cooling base on the back of the steel plate, and cooling water or liquid nitrogen is introduced into the base through a cooling liquid inlet to be cooled.
After laser welding is finished, a sample is sampled, and each tissue and hardness of a joint of the sample are tested, and the result shows that when 2000W laser power is adopted for welding, a heat affected zone of the joint is softened to a certain degree, so that the softening degree of the heat affected zone of the joint can be obviously reduced by improving the welding power and the welding speed, and air holes in a welding line can be effectively avoided.
The welded test piece was subjected to structure observation and basic performance test as shown in the table:
from the test results, the hardness of the heat affected zone was significantly changed by the adjusted power parameters, so that the softening degree at low power in the heat affected zone was effectively improved.
Wherein, the cooling mode can adopt the mode of water, air or liquid nitrogen to cool the back of the welding test plate, the cooling speed range is 500 ℃/s-45 ℃/s, and the tempered martensite structure content in the welding line is less.
The invention mainly aims at effectively improving the hardness softening degree of the manganese steel laser welding joint in the high product of strength and elongation, and the softening degree of a heat affected zone can be effectively reduced by adopting the process. And by adopting the process, the width of the heat affected zone can be effectively reduced, and the performance of the heat affected zone can be improved to the greatest extent.
Claims (8)
1. A method for reducing the softening degree of a manganese steel laser welding joint in a high strength-elongation product is characterized by comprising the following steps:
the high-strength-ductility medium manganese steel comprises the following chemical components in percentage by weight: 0.05-0.45 wt.% of C, 4.50-8.00 wt.% of Mn, 0.01-2.50 wt.% of Si, Al: 0-3.00 wt%, P is less than or equal to 0.02 wt%, S is less than or equal to 0.02 wt%, Nb is 0-0.02 wt%, V is 0-0.30 wt%, Ti is 0-0.30 wt%, and the balance is Fe and inevitable impurity elements;
the welding process is to butt joint the high-strength plastic-product medium manganese steel plates and then carry out laser welding, a single-side welding and double-side forming process is adopted, the laser welding power is 2-4 kW, the welding speed is 4.8m/min, and a deep fusion welding mode is adopted for welding;
during the welding, the type of the shielding gas is pure argon, a front and back full protection mode is adopted, and the flow of the front shielding gas is 15L/min;
and in the welding process, cooling the back surface of the welded steel at a cooling speed of 500-45 ℃/s.
2. The method for reducing the softening degree of a high product of strength and elongation medium manganese steel laser welded joint according to claim 1, wherein:
and for the steel plate with the thickness less than or equal to 3mm, a red copper plate is placed on the back of the steel plate for cooling.
3. The method for reducing the softening degree of a high product of strength and elongation medium manganese steel laser welded joint according to claim 1, wherein:
for a steel plate with the thickness of 3-8 mm, a red copper cooling base is arranged on the back of the steel plate, and cooling water or liquid nitrogen is introduced from a cooling liquid inlet to the inside of the base for cooling.
4. The method for reducing the softening degree of a high product of strength and elongation medium manganese steel laser welded joint according to claim 1, wherein:
during welding, selecting an I-shaped groove for groove processing of the high-strength-plastic-product medium manganese steel plate; the butt joint clearance is 0.1mm, before welding, the steel plate is polished and scrubbed by acetone, greasy dirt and impurities are removed, a proper clamp is adopted to butt joint and fix the steel plate, and then a fiber laser is adopted to weld.
5. The method for reducing the softening degree of a high product of strength and elongation medium manganese steel laser welded joint according to claim 1, wherein:
the high-strength-ductility medium manganese steel comprises the following chemical components in percentage by weight: 0.08-0.45 wt.% of C, 4.50-8.00 wt.% of Mn, 0.01-2.50 wt.% of Si, Al: 0-3.00 wt%, P is less than or equal to 0.02 wt%, S is less than or equal to 0.02 wt%, Nb is 0-0.02 wt%, V is 0-0.30 wt%, Ti is 0-0.30 wt%, and the balance is Fe and inevitable impurity elements.
6. The method for reducing the softening degree of a high product of strength and elongation medium manganese steel laser welded joint according to claim 1, wherein:
the width of the heat affected zone of the steel plate with the thickness of 2-8 mm is 0.4-5 mm.
7. The method for reducing the softening degree of a high product of strength and elongation medium manganese steel laser welded joint according to claim 1, wherein:
the high-strength-ductility medium manganese steel in the method is used for automobile steel plates.
8. The method for reducing the softening degree of a high product of strength and elongation medium manganese steel laser welded joint according to claim 1, wherein:
the welding piece obtained by the method has the following mechanical properties: the tensile strength is 756-819 MPa, and the yield strength is 607-638 MPa.
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