KR20150075705A - Method for resistance spot welding of galvanized steel sheet - Google Patents
Method for resistance spot welding of galvanized steel sheet Download PDFInfo
- Publication number
- KR20150075705A KR20150075705A KR1020130163922A KR20130163922A KR20150075705A KR 20150075705 A KR20150075705 A KR 20150075705A KR 1020130163922 A KR1020130163922 A KR 1020130163922A KR 20130163922 A KR20130163922 A KR 20130163922A KR 20150075705 A KR20150075705 A KR 20150075705A
- Authority
- KR
- South Korea
- Prior art keywords
- welding
- energization
- galvanized steel
- current
- resistance
- Prior art date
Links
Classifications
-
- 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
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/16—Resistance welding; Severing by resistance heating taking account of the properties of the material to be welded
- B23K11/163—Welding of coated materials
- B23K11/166—Welding of coated materials of galvanized or tinned materials
-
- 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
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/10—Spot welding; Stitch welding
- B23K11/11—Spot welding
-
- 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
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/24—Electric supply or control circuits therefor
- B23K11/241—Electric supplies
-
- 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
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/34—Preliminary treatment
Abstract
BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a spot welding method of a plated steel material, and more particularly, to a resistance spot welding method of a galvanized steel material for hot press forming.
Description
BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a spot welding method of a plated steel material, and more particularly, to a resistance spot welding method of a galvanized steel material for hot press forming.
Recently, there has been a growing demand for high-strength and lightweight manufacturing technology for automobile parts and the like due to the weight reduction of the vehicle body and the fuel saving trend due to high oil prices. Therefore, a method of joining a plurality of plates having different materials or different thicknesses and strengths from each other in view of manufacturing automobile parts and the like that meet the purpose and purpose is an area that needs continuous research.
Among them, Resistance Spot Welding (RSW) has been mainly used in the automobile industry as a technique for joining joints of a plurality of high-strength steel plates. Because of its ease of automation and suitable for mass production processes, It is most widely used in the automobile production process.
Resistance spot welding is a technique in which a large current is flowed under pressure to obtain heat due to the contact resistance and the intrinsic resistance of the metal on the contact surfaces of the metals so that the bonding is carried out by the applied pressure when the metal is heated or melted .
Specifically, when a large current of kA unit is applied while applying pressure to two electrodes located above and below a two-layer welding base material, the contact resistance generated at the contact surface between the electrode and the welding base material, Heat is generated due to the intrinsic resistance of the metal, and after the metal is heated and melted, the metal is cooled and solidified to be bonded.
The amount of heat input during the resistance spot welding process is proportional to the welding current (i), the electric resistance (R), and the welding time (t) by Joule's law (Q = i2Rt).
Particularly, the amount of heat input is proportional to the square of the welding current (i2), and is most greatly influenced by the intensity of the welding current. If the intensity of the welding current (i) is excessively high, a surface expulsion of molten metal occurs on the surface of the metal material being welded. If the welding phenomenon occurs as described above, the welded state of the welding part becomes poor, and the strength of the welded part greatly decreases.
On the other hand, as the heat input increases, the size of the nugget, the weld metal produced by melt coagulation, grows. The size of the nugget is also a factor directly affecting the strength determination of the weld.
Therefore, it is very important to appropriately form the size of the nugget that determines the strength of the joint within the range of the current that does not cause the above-mentioned twisting phenomenon when joining the material through resistance spot welding, The applicable current conditions in spot welding are determined.
Generally, the welding current is constantly energized and welded (ISO standard) for a period of time not exceeding 1 second in consideration of the productivity, and the welding current is increased to a condition where the welding current does not occur, This is because it is advantageous to increase the strength of the nugget to maximize the size of the nugget within the range in which no warping occurs. Thus, the minimum welding current intensity that satisfies the minimum size criterion of the nugget corresponding to the required strength is determined as the lower limit current, and the current that causes the deflection is determined as the upper limit current.
However, resistance point welding is performed within such a range that no flying phenomenon occurs, and there is a limitation in increasing the size of the nugget and a limitation in improving the strength of the welded joint.
On the other hand, the zinc-plated steel sheet is the most typical automobile material mainly used for automobile body panel, and it is also applied as a member for automobile by applying hot press forming (HPF) to such galvanized steel sheet.
The galvanized steel sheet can be classified into hot-dip galvanized steel sheet called 'GI steel sheet' and galvannealed steel sheet called 'GA steel sheet'. After passing through the plating bath, GI steel sheet in the manufacturing process is made of pure Zn And the GA steel sheet is formed by Fe-Zn-based intermetallic compound in the plating layer due to the alloying reaction of iron and zinc.
In general, GI steel has excellent formability and corrosion resistance, and GA steel has better weldability and paintability than GI steel.
However, there is a problem in that the strength of the welded joint, particularly the cross tensile strength, is insufficient when the ISO standard resistance point welding is applied to weld the hot press-formed galvanized steel sheet, In the case of performing welding under the condition of a current range exceeding the current range where the strength is increased to improve the strength, cracks are generated on the surface of the welded portion, thereby deteriorating the appearance of the welded portion and deteriorating the corrosion characteristics.
Therefore, there is a demand for a welding method capable of improving the cross-tensile strength of the galvanized steel sheet subjected to the hot-press-formed galvanized steel sheet even when the galvanized steel sheet is subjected to resistance spot welding at a current range exceeding the current range causing the rolling phenomenon.
One aspect of the present invention is to provide a welding method capable of improving the strength of a galvanized steel sheet without causing surface cracks at welds even in a current range exceeding a current range causing a drag phenomenon.
One aspect of the present invention is a method of manufacturing a galvanized steel sheet, comprising the steps of: i) pressing an electrode onto a galvanized steel to contact the electrode with the galvanized steel; Ii) performing preliminary energization after the electrode contacts the galvanized steel; Iii) cooling the galvanized steel after completion of the pre-energization; Iv) performing the main energization after the completion of the cooling; And v) applying a pressing force to the electrode after completion of the main energization,
Wherein the preliminary energization is performed at a welding current of 5.0 to 6.0 kA and a welding (energization) time of 200 to 800 ms.
When the resistance spot welding of the galvanized steel is performed by the welding method according to the present invention, it is possible to secure the nugget to a sufficient size, so that even if the welding is performed in a current range in which the welding phenomenon occurs, It is possible to obtain a welded portion without surface cracks.
The inventors of the present invention have made intensive studies on the welding method capable of improving the cross tensile strength without welding the surface of the weld portion even when the galvanized steel is welded by the resistance spot welding even when the current range causing the drag phenomenon occurs. It has been found that the strength of the final welded portion can be improved by energizing a larger current in the subsequent main energization as the resistance of the formed welded portion is lowered, thereby completing the present invention.
Hereinafter, a resistance spot welding method of a galvanized steel according to one aspect of the present invention will be described in detail with reference to the drawings.
2 is a graph showing a resistance spot welding method of a galvanized steel according to the present invention.
As shown in Fig. 2, the zinc-plated steel material resistance spot welding method of the present invention comprises the steps of: i) pressing an electrode onto a galvanized steel material to bring the electrode into contact with the galvanized steel material; Ii) performing preliminary energization after the electrode contacts the galvanized steel; Iii) cooling the galvanized steel after completion of the pre-energization; Iv) performing the main energization after the completion of the cooling; And v) applying a pressing force to the electrode after completion of the main energization.
In the following, each of the above sequential steps will be described in more detail.
First, a step of pressing the electrode onto the galvanized steel prepared for welding is carried out (Squeeze). At this time, it is preferable that the pressing is performed in a state in which the electrode is in contact with the galvanized steel.
Next, preliminary energization is preferably performed by applying an electric current to the electrode for pressing the zinc-plated steel material.
The preliminary energization is intended to cause melting and discharge of the plated layer of the galvanized steel material to occur earlier than the steel material. In the present invention, it is preferable that the preliminary energization is carried out under optimum conditions to reduce the resistance of the welded part through preliminary energization. It is possible to energize a large current when energized.
More specifically, the preliminary energization is preferably performed at a welding current of 5.0 to 6.0 kA and a welding (energization) time of 200 to 800 ms.
If the welding current is less than 5.0 kA at the time of pre-energization, it is difficult to sufficiently reduce the resistance of the welding portion. On the other hand, if the welding current exceeds 6.0 kA, spatter occurs and the quality of the weld portion deteriorates. If the welding time is shorter than 200 ms, it is difficult to sufficiently reduce the resistance of the welding portion. On the other hand, if the welding time exceeds 800 ms, the productivity is deteriorated due to the preliminary energization for a long time.
When the preliminary energization is carried out under the above-described conditions, it is preferable that the energizing cycle is performed within 12 to 48 cycles.
According to Table 1 of the embodiment of the present invention, when the pre-energization is carried out under the conditions according to the present invention, the resistance of the welded portion can be effectively reduced, whereas when the welding current is low (less than 5.0 kA) If it is too high (more than 6.0 kA), it is advantageous to reduce the resistance of the welded part, but it can be confirmed that there is a problem that the quality of the welded part is deteriorated due to the occurrence of the ripple phenomenon.
When the preliminary energization according to the present invention is completed, it is preferable that the molten plated layer is cooled for a predetermined time by blocking the applied current.
The cooling after the preliminary energization is for applying a sufficient current while minimizing the generation of the subsequent spatter upon energization.
In this case, it is desirable to perform the cooling at 10 to 200 ms in consideration of the process time and the performance of the welding machine. If the cooling time is less than 10 ms, sufficient cooling can not be performed, There is a problem. If the cooling time exceeds 200 ms, the cooling effect is saturated and the process cost is increased.
When cooling is carried out under the above-mentioned conditions, it is preferable that the energizing cycle is performed within 1 to 10 cycles.
When the cooling is completed, it is preferable to conduct the energization step by energizing a current higher than the current applied during the preliminary energization.
According to the present invention, since the resistance of the welded portion is reduced to the minimum through the pre-energization, it is possible to obtain a welded portion having no surface defect and excellent strength even when the subsequent current is large.
More specifically, it is preferable that the current magnitude of the pre-energization current is at least 1 time and at most 8 kA. At this time, the welding time is not particularly limited, and it is preferable that the welding is carried out to such an extent that nugget having excellent strength can be obtained even if the welding phenomenon occurs, without causing the welding portion to break.
After completing the welding step according to the above description, it is preferable to perform a step of cutting off the energized current and applying a pressing force to the electrode to hold it for a predetermined time.
As described above, it is possible to obtain a welded portion having a good surface quality and excellent strength by applying a pressing force.
It is preferable that the diameter of the nugget (the direction perpendicular to the base material thickness) of the welded portion formed by the present invention is 4 times or more the thickness of the zinc-plated steel material (single base material).
In the conventional resistance spot welding method, the upper limit current is limited by the properties of the base material, so that it is difficult to ensure the diameter of the nugget of the welded portion formed within the range that does not cause the fly phenomenon to be four times or more the thickness of the base material .
However, according to the present invention, it is possible to secure the size of the welded nugget 4 times or more of the thickness of the base material without occurrence of the flying phenomenon. This means that the strength of the weld can be increased to such an extent that it is difficult to realize by conventional methods. Therefore, in order to maximally improve the strength of the welded portion, it is preferable that the diameter of the formed welded nugget is formed to be four times or more the thickness of the base material, according to the resistance spot welding method disclosed in one aspect of the present invention.
The zinc-plated steel material referred to in the present invention is a steel material for hot press forming (HPF). The zinc-plated steel material is manufactured by hot press forming and then subjected to resistance spot welding according to the present invention Whereby it is possible to suppress the occurrence of defects such as breakage in the welded portion.
Hereinafter, the present invention will be described more specifically by way of examples. It should be noted, however, that the following examples are intended to illustrate the invention in more detail and not to limit the scope of the invention. The scope of the present invention is determined by the matters set forth in the claims and the matters reasonably inferred therefrom.
( Example )
The present inventors conducted preliminary energization under the respective conditions shown in Table 1 after pressurization (3.5 kN) using two layers of zinc plated steel to find the welding conditions capable of minimizing the resistance of the weld portion during preliminary energization, Are shown together in Table 1 below.
Here, a galvanized steel sheet plated with a plating amount of about 65 g / m 2 on one side was used.
↓ welding current
Occurrence
(The unit of the measured resistance value is < RTI ID = 0.0 >
As shown in Table 1, when the current is 4.5 kA at the time of preliminary energization, not only a long welding time is required in order to sufficiently reduce the resistance of the welding portion, but a decrease in the resistance of the welding portion is small even though the welding time is long. In addition, when the current is 6.5 kA, there is a problem that the effect of reducing the resistance of the weld portion is large, but the surface quality deteriorates due to occurrence of the fly phenomenon.
However, when the current was 5.0 or 5.5kA during pre-energization, the resistance of the welded part was excellent in all cases, and no flicker occurred.
However, in the case of the current of 6.0 kA, some spalling occurred, but this did not affect the physical properties of the welded part, and the effect of decreasing the resistance of the welded part was also excellent.
11: upper electrode
12: Lower electrode
13: upper welding base material
14: Lower welding base material
15: Nugget
Claims (5)
Wherein the preliminary energization is performed at a welding current of 5.0 to 6.0 kA and a welding (energization) time of 200 to 800 ms.
Wherein the cooling is performed at 10 to 200 ms and 1 to 10 cycles.
Wherein the main energization is carried out with a current magnitude of at least 1 times the current magnitude of the pre-energization, up to a maximum of 8 kA.
Wherein the nugget diameter of the weld formed after the pre-energization is at least four times the thickness of the galvanized steel.
Wherein said zinc plated steel is a plated steel for hot press forming (HPF).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1020130163922A KR20150075705A (en) | 2013-12-26 | 2013-12-26 | Method for resistance spot welding of galvanized steel sheet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1020130163922A KR20150075705A (en) | 2013-12-26 | 2013-12-26 | Method for resistance spot welding of galvanized steel sheet |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| KR20150075705A true KR20150075705A (en) | 2015-07-06 |
Family
ID=53788774
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| KR1020130163922A KR20150075705A (en) | 2013-12-26 | 2013-12-26 | Method for resistance spot welding of galvanized steel sheet |
Country Status (1)
| Country | Link |
|---|---|
| KR (1) | KR20150075705A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20200023812A (en) * | 2018-08-27 | 2020-03-06 | 현대자동차주식회사 | Welding method for zinc coated steel |
| CN113751848A (en) * | 2021-09-08 | 2021-12-07 | 福建南平南孚电池有限公司 | Battery collector electron resistance welding process |
-
2013
- 2013-12-26 KR KR1020130163922A patent/KR20150075705A/en not_active Application Discontinuation
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20200023812A (en) * | 2018-08-27 | 2020-03-06 | 현대자동차주식회사 | Welding method for zinc coated steel |
| CN113751848A (en) * | 2021-09-08 | 2021-12-07 | 福建南平南孚电池有限公司 | Battery collector electron resistance welding process |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR101744427B1 (en) | Spot welding method for high-strength steel sheet excellent in joint strength | |
| CN107350613B (en) | Resistance spot welding process for steel workpiece with coating layer | |
| CN109202245B (en) | Resistance spot welding method suitable for three-layer plate with aluminum-silicon coating as intermediate layer for hot forming steel | |
| KR102058305B1 (en) | Resistance spot welding method and manufacturing method of welding member | |
| JP6572986B2 (en) | Resistance spot welding method and resistance spot welding determination method | |
| CN102602072A (en) | Resistance spot welding manufacture and method of forming same | |
| KR101639847B1 (en) | Method for resistance spot welding of galvanized steel sheet | |
| CN101596642A (en) | Method for resistance welding and Welding Structure | |
| WO2023065797A1 (en) | Dissimilar metal joint and resistance welding method therefor | |
| KR20190089192A (en) | Resistance spot welding method | |
| CN108544062A (en) | A kind of automatic welding method for welding of aluminium alloy sheet | |
| CN108188582A (en) | A kind of compound welding with filler wire method of laser-electric arc for being used to prepare magnesium/steel dissimilar metal tailor welded | |
| KR20150075705A (en) | Method for resistance spot welding of galvanized steel sheet | |
| KR20180031033A (en) | Resistance spot welding method and method for manufacturing welding member | |
| KR102010069B1 (en) | Method for resistance spot welding of multy-layer steel sheet | |
| KR102142789B1 (en) | Resistance spot welding method for aluminium based plated steel | |
| KR101322068B1 (en) | Cald steel material and method for manufacturing the same | |
| JP6315161B1 (en) | Resistance spot welding method | |
| JPWO2020036198A1 (en) | Resistance spot welding member and manufacturing method thereof | |
| JP4469165B2 (en) | Dissimilar joints of steel and aluminum and their joining methods | |
| CN112570868B (en) | Method for improving corrosion resistance of resistance spot welding spot of 1800 MPa-grade hot forming steel | |
| CN112620906B (en) | Method for improving corrosion resistance of resistance spot welding spot of 1500 MPa-grade hot forming steel | |
| US20230121205A1 (en) | Resistance spot welding method and weld member production method | |
| KR101657781B1 (en) | METHOD FOR RESISTANCE SPOT WELDING FOR Zn PLATED STEEL SHEET | |
| CN110773856A (en) | Resistance spot welding method for high-strength steel workpiece and high-strength aluminum alloy workpiece |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A201 | Request for examination | ||
| E902 | Notification of reason for refusal | ||
| E902 | Notification of reason for refusal | ||
| E601 | Decision to refuse application |