KR20140013176A - Laser welding method for different kind steel - Google Patents
Laser welding method for different kind steel Download PDFInfo
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- KR20140013176A KR20140013176A KR1020120079011A KR20120079011A KR20140013176A KR 20140013176 A KR20140013176 A KR 20140013176A KR 1020120079011 A KR1020120079011 A KR 1020120079011A KR 20120079011 A KR20120079011 A KR 20120079011A KR 20140013176 A KR20140013176 A KR 20140013176A
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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
- B23K26/211—Bonding by welding with interposition of special material to facilitate connection of the parts
-
- 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
- B23K26/24—Seam welding
- B23K26/26—Seam welding of rectilinear seams
-
- 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
- B23K26/32—Bonding taking account of the properties of the material involved
-
- 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
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
- B23K35/0255—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in welding
- B23K35/0261—Rods, electrodes, wires
-
- 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
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/24—Selection of soldering or welding materials proper
- B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550 degrees C
- B23K35/3053—Fe as the principal constituent
-
- 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
- B23K2103/02—Iron or ferrous alloys
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Mechanical Engineering (AREA)
- Plasma & Fusion (AREA)
- Laser Beam Processing (AREA)
Abstract
The present invention relates to a laser welding method of dissimilar steels. The present invention is a method for welding ferritic steels and austenitic steels as an embodiment, the laser of the dissimilar steels welding the ferritic steels and austenitic steels by irradiating a laser beam while feeding the STS 310 welding wire Provide a welding method.
According to the present invention, it is possible to produce a product in which the crack of the weld portion does not occur during molding by improving the formability of the weld portion during laser welding of dissimilar steels having different strengths.
Description
The present invention relates to a laser welding method of dissimilar steels.
In recent years, the automobile industry has been greatly demanded to reduce exhaust gases such as carbon dioxide due to environmental regulations, to improve fuel efficiency by reducing weight, and to improve collision stability. In particular, in order to reduce the weight of the vehicle body, it is essential to reduce the thickness of the material and at the same time to apply the steel having improved strength and ductility. However, unlike mild steel, high strength steel has a problem in that weldability is degraded due to a large amount of alloying elements during welding. As a result, a welding method that is less affected by the strength of the material and minimizes thermal deformation is required. As a welding method for this, deep penetration by a keyhole mode and a laser welding method having a narrow HAZ width are recently noted. I am getting it.
On the other hand, Taylor Welded Blank (TWB) by laser welding is widely used in automobile companies and parts manufacturing companies to reduce the weight of the car body, and the blank is usually cut to fit the shape of the part in consideration of weldability and formability. It is then manufactured by employing two types of high density laser welding, a simple butt-linear welding method and a more complex nonlinear method. In addition, due to the characteristics of the TWB parts are mainly produced by laser welding on a material having a base material strength and thickness difference.
In this regard, the application of laser welding of mild and high strength steels with different thicknesses is increasing in recent years, and in order to secure sound welds, it is necessary to consider specific factors in addition to basic welding variables such as laser power, welding speed, condenser, and focus position. This is because of the effect of tissue formation on the weld characteristics.
In the case of ordinary dissimilar thicknesses of ferritic carbon steels, the weld metal has little metallurgical effect even if the materials such as strength are different due to the characteristics of laser welding. However, high-strength TWIP (Twinning Induced Plasticity) steels have no transformation even after welding. Therefore, it is necessary to pay attention to laser welding of austenitic steels and ferritic carbon steels in phase transformation because of their metallurgical characteristics. In particular, in the case of heterogeneous laser welding between austenitic steels and ferritic carbon steels, there is a problem that hard and fragile martensite is easily formed in the weld metal, thereby degrading the formability of the welded portion.
The present invention relates to a laser welding method for dissimilar steels which can prevent the formation of martensite in the weld metal during laser welding of dissimilar steels and thereby improve the formability.
One embodiment of the present invention is a method for welding ferritic steel and austenitic steel, the laser of the dissimilar steel welding the ferritic steel and austenitic steel by irradiating a laser beam while feeding the STS 310 welding wire Provide a welding method.
According to the present invention, it is possible to produce a product in which the crack of the weld portion does not occur during molding by improving the formability of the weld portion during laser welding of dissimilar steels having different strengths.
1 is a schematic diagram showing the principle of laser welding.
2 is a result of measuring the hardness after laser welding the austenitic steel and the ferritic steel without using a welding wire.
3 is a state diagram showing the microstructure of the weld metal of TWIP steel and carbon steel in consideration of the Schaeffler diagram.
Figure 4 is a graph showing the relationship between the use of the weld wire and the martensite formation amount and workability in the weld metal according to its type.
5 is a result of observing the cross-sectional structure after welding the TWIP steel and 340Y steel without the butt gap.
6 is a result of observing the change in the appearance and the cross-sectional structure of the weld metal according to the feeding speed of the welding wire.
7 is a result of observing changes in the weld metal appearance and cross-sectional structure according to the butt gap.
8 is a result of observing the appearance of the weld and the presence of cracks after performing the Ericsson test on the weld in four cases according to the second embodiment of the present invention.
Hereinafter, the present invention will be described.
In general, automotive welded blank (TWB) products for automobiles are subjected to high-density laser welding in linear and non-linear manner after cutting the blanks according to the part shape in consideration of weldability and formability in order to apply to a vehicle body. The principle of laser welding that can be preferably applied to the present invention is as shown in FIG. The keyhole (keyhole) is generated by the laser
When forming TWB parts, the weldability of welds is closely related to weld defects. In order to improve the quality of welds, there should be no defects such as cracks or pores, and the ductility and toughness of welds should be excellent.
2 is a result of measuring the hardness after laser welding the austenitic steel and the ferritic steel without using a welding wire. In the case of manufacturing a TWB product having different types of steels by welding austenitic steels and ferritic steels, the conventional laser welding method is welding by applying only a laser beam, as shown in FIG. It is understood that a high hardness structure such as martensite is formed in the weld joint), and the weld metal has a very high hardness of about 600 Hv. As such, when a structure such as martensite is formed in the weld metal and the hardness thereof is increased, moldability of the weld portion may be deteriorated, and thus, processing of the product may not be easy.
In order to solve this problem, the present invention is a method of welding ferritic steel and austenitic steel as an embodiment, the ferrite-based steel and austenitic steel by irradiating a laser beam while feeding the STS 310-based welding wire It provides a laser welding method of different steels for welding. As described above, in the present invention, unlike the conventional laser welding method in which only the ray point beam is irradiated without the welding wire, laser welding is performed while feeding the STS 310 series welding wire so that martensite or the like is not formed in the weld metal. It is possible to prevent cracking during processing of the weld metal. On the other hand, the STS 310-based welding wire can be used as long as it has an alloy composition commonly known in the art, for example, by weight, C: 0.05 ~ 0.15%, Mn: 1.5 ~ 2.0%, Si: It may have an alloy composition such as 0.2 to 0.6%, Cr: 24 to 27%, and Ni: 18 to 22%.
The ferritic steels that can be applied to the present invention can be used as long as the ferritic steel is not particularly limited to the kind, for example, ferrite structure such as solid solution hardening steel, precipitation hardening steel including 340Y steel Carbon steel and the like can be used. Austenitic steels may also be used as austenite single phase or steel having austenite as its main structure, regardless of its type, for example, TWIP steel or austenitic stainless steel. The 340Y steel is a steel having a yield strength of 340 to 440 MPa, a tensile strength of 410 MPa or more and an elongation of 18% or more. The composition is weight%, C: 0.08 to 0.1%, Mn: 0.8 to 1.0%, and Si: 0.2. -0.3% and other alloying elements. Further, TWIP steels typically have a composition comprising C: 0.5-0.8%, Mn: 13-20%, Al: 1.0-2.0%, and other alloying elements.
In addition, the austenitic steel and the ferritic steel may have a different thickness, and in the present invention, even if the thickness of the steel is different, a weld metal having excellent formability may be manufactured, and thus various and complicated shapes Applicable to the
3 is a state diagram showing the microstructure of the weld metal of TWIP steel and carbon steel in consideration of the Schaeffler diagram. As shown in Figure 3, the weld metal obtained by welding the TWIP steel and carbon steel (340Y steel) without a welding wire is martensite is formed when considering dilution. However, when welding wire is used, the welding metal structure is austenitic + martensite, especially when welding using STS 308 welding wire (18% Cr-8% Ni), and STS 310 welding wire (25%). When welding is carried out using Cr-20% Ni), it can be seen that austenite is formed in the weld metal.
Figure 4 is a graph showing the relationship between the use of the weld wire and the martensite formation amount and workability in the weld metal according to its type. As shown in FIG. 4, the weld metal obtained by welding the austenitic steel and the ferritic steel is different depending on the use of the welding wire and the amount of martensite formed depending on the type of the welding wire. As mentioned above, martensite present in the weld metal has a great impact on formability. In the present invention, by welding using the STS 310 series welding wire can reduce the amount of martensite formed in the weld metal to improve the formability.
In the present invention, the formability of the weld metal can be improved by performing laser welding using the welding wire as described above, but it is advantageous to control the feeding speed of the welding wire for a more preferable effect. It is preferable that the feeding speed of the welding wire is 2 to 4mpm (m / min). When the feeding speed of the welding wire is less than 2mpm, it is difficult to uniformly melt the welding wire due to the slow feeding speed, so that dilution is almost performed in the welding metal. It may not be supported, thereby deteriorating the moldability. On the other hand, if the feed rate is more than 4mpm melt amount of the wire is increased, the bead is increased more than necessary, the efficiency may be lowered in terms of productivity. Therefore, it is preferable that the feeding speed of the welding wire has a range of 2 to 4 mpm. The supply speed is more preferably in the range of 2.5 ~ 4mpm, more preferably in the range of 2.5 ~ 4.5mpm.
In addition, in the welding method of the present invention, the butt gap is preferably in the range of 0.05 to 0.15 mm for the steel to be welded as well as the feeding speed control of the welding wire. 5 is a result of observing the cross-sectional structure after welding the TWIP steel and 340Y steel without the butt gap. As shown in FIG. 5, when there is no butt gap, that is, when the butt gap is 0 mm, defects do not occur in the weld bead, but the shape of the weld bead may be deteriorated. It is presumed to be caused by some deformation during the solidification process. In order to solve this problem, it is preferable that the butt gap has a range of 0.05 mm or more. However, if the gap is too large, it is preferable to maintain the proper gap because the diameter of the conventional laser beam is very small, such as 0.25 ~ 0.35mm, for this purpose it is preferable that the butt gap has a range of 0.15mm. If it exceeds 0.15 mm, pores may occur in the weld bead. Therefore, the butt gap preferably has a range of 0.05 to 0.15 mm, more preferably 0.07 to 0.13 mm, and even more preferably 0.09 to 0.11 mm.
Hereinafter, the present invention will be described in more detail with reference to Examples.
(Example 1)
By weight, after preparing a ferritic steel having an alloy composition such as C: 0.003%, Mn: 0.15%, Si: 0.002%, etc., bead-on-plate while feeding the STS 310 welding wire with a diameter of 0.9 mm After the welding was performed, the appearance and the cross-sectional structure of the welded portion were observed and the results are shown in FIG. 6. At this time, CO 2 laser welding was used as a welding method, the output amount was 6kW, the welding speed was 4mpm, the butt gap was 0.1mm, and the feeding speed of the welding wire was 0.3-3mpm. On the other hand, in the austenitic steels, the weld metal has an austenitic structure, so in order to more clearly measure the difference according to the feeding speed, the austenitic steels were welded by ferrite-based single welding rather than welding between austenitic and ferritic steels. .
As can be seen in Figure 6, when the feeding speed of the welding wire is slow, such as 0.3mpm or 1.0mpm, the welding wire is not uniformly melted, so that the dilution of the weld metal is hardly achieved. However, when the feeding speed is 3.0mpm, it can be seen that a good bead shape and a weld metal are formed while the welding wire is uniformly melted.
(Example 2)
TWIP steel (thickness: 1.6 mm) having an alloy composition such as C: 0.7%, Mn: 18.0%, Al: 2.0%, etc., in weight% with ferritic steel (DDQ steel) (thickness: 1.0 mm) used in Example 1 ) And after laser welding the steel while feeding the STS 310 welding wire used in Example 1, the appearance and cross-sectional structure of the welded part were observed and the results are shown in FIG. 7. At this time, CO 2 laser welding was used as the welding method, the output amount was 6kW, the welding speed was 4mpm, the wire feeding speed was 3mpm, and the butt gap was changed in the range of 0 ~ 0.2mm.
As shown in FIG. 7, when the butt gap is 0 mm and a welding wire is not used, not only the hard structure such as martensite is formed in the weld metal, but also the bead shape is not good. Although welding was performed using the STS 310 welding wire, when the butt gap was 0 mm, it can be seen that the deformation of the bead shape occurred. In the case where the butt gap was 0.2 mm, a good weld could be secured without any shape change. However, when the appearance was examined, some pores were observed at the end of the bead. On the contrary, in the case where the butt gap satisfying the butt gap range proposed by the present invention is 0.1 mm, both the appearance of the welded part and the bead shape are good.
On the other hand, the Ericsson test was performed on the welds of the four cases welded as described above, the results are shown in FIG. As shown in FIG. 8, when the welding wire is not used, it can be seen that cracking has occurred in the welded part. However, when the STS 310 welding wire is used as the present invention suggests, cracking does not occur in the welded part. The phenomenon of cracking in the ferritic steels was observed. That is, according to the welding method proposed by this invention, the weld part with favorable moldability can be ensured. On the other hand, the Ericsson test means that the welded portion is processed into a convex form using an Ericsson device (punch).
1: laser beam
3: metal steam
5: molten metal
7: weld bead
Claims (4)
The ferritic steel and the austenitic steel is a laser welding method of dissimilar steel having different thicknesses.
The feeding speed of the welding wire is a laser welding method of different steels of 2 ~ 4mpm.
The ferritic steel and the austenitic steel is a laser welding method of a heterogeneous steel is welded by butt welding so that the butt gap has a range of 0.05 ~ 0.15mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1020120079011A KR20140013176A (en) | 2012-07-19 | 2012-07-19 | Laser welding method for different kind steel |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1020120079011A KR20140013176A (en) | 2012-07-19 | 2012-07-19 | Laser welding method for different kind steel |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2019132289A1 (en) * | 2017-12-26 | 2019-07-04 | 주식회사 포스코 | High-strength high manganese-plated steel plate welded structure having excellent spot weldability and method for manufacturing same |
| US10543565B2 (en) | 2015-09-21 | 2020-01-28 | Wisco Tailored Blanks Gmbh | Laser welding method for producing a semi-finished sheet metal product made of hardenable steel and comprising a coating based on aluminium or aluminium-silicon |
-
2012
- 2012-07-19 KR KR1020120079011A patent/KR20140013176A/en not_active Application Discontinuation
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10543565B2 (en) | 2015-09-21 | 2020-01-28 | Wisco Tailored Blanks Gmbh | Laser welding method for producing a semi-finished sheet metal product made of hardenable steel and comprising a coating based on aluminium or aluminium-silicon |
| WO2019132289A1 (en) * | 2017-12-26 | 2019-07-04 | 주식회사 포스코 | High-strength high manganese-plated steel plate welded structure having excellent spot weldability and method for manufacturing same |
| KR20190078436A (en) * | 2017-12-26 | 2019-07-04 | 주식회사 포스코 | High manganese coated steel welded structure with superior spot weldability and method for manufacturing same |
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