KR100940678B1 - Welding Method for Excellent Properties of Welded Joints - Google Patents
Welding Method for Excellent Properties of Welded Joints Download PDFInfo
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- KR100940678B1 KR100940678B1 KR1020070081136A KR20070081136A KR100940678B1 KR 100940678 B1 KR100940678 B1 KR 100940678B1 KR 1020070081136 A KR1020070081136 A KR 1020070081136A KR 20070081136 A KR20070081136 A KR 20070081136A KR 100940678 B1 KR100940678 B1 KR 100940678B1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/23—Arc welding or cutting taking account of the properties of the materials to be welded
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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
- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
- B23K20/10—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating making use of vibrations, e.g. ultrasonic 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
- B23K9/00—Arc welding or cutting
- B23K9/02—Seam welding; Backing means; Inserts
- B23K9/0216—Seam profiling, e.g. weaving, multilayer
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/02—Seam welding; Backing means; Inserts
- B23K9/025—Seam welding; Backing means; Inserts for rectilinear seams
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Abstract
두 개의 강재를 용융 용접하는 경우 적용될 수 있는 용접이음부의 특성이 우수한 용접방법이 제공된다.Provided is a welding method having excellent characteristics of a welded joint that can be applied when welding two steels.
이 용접방법은 두 개의 강재를 용융용접하는 용접방법에 있어서, 용접하고자 하는 용접이음부에서 용접봉과 같은 속도로 용융지에 0.5㎛ 이상의 초음파 진동을 전파하는 것이다.The welding method is a welding method for welding two steels by propagating an ultrasonic vibration of 0.5 µm or more to the molten paper at the same speed as the electrode at the welding joint to be welded.
본 발명에 따르면, 용융 용접시 용융지에 초음파 진동을 전파함에 따라 용접금속의 결정립이 미세화되어 용접이음부 특성을 개선된 용접방법을 제공할 수 있는 효과가 있다.According to the present invention, as the ultrasonic vibration propagates to the molten pool during melt welding, the crystal grains of the weld metal may be miniaturized, thereby providing a welding method having improved weld seam characteristics.
초음파 진동, GTAW 용접, 용접금속, 충격인성, 결정립 미세화 Ultrasonic Vibration, GTAW Welding, Welding Metal, Impact Toughness, Grain Refinement
Description
본 발명은 두 개의 강재를 용융 용접하는 경우, 우수한 특성을 갖는 용접이음부를 형성하는 용접방법에 관한 것으로, 보다 상세하게는 용융 용접시 용융지에 초음파 진동을 전파함에 따라 용접이음부의 특성을 개선할 수 있는 용접방법에 관한 것이다.The present invention relates to a welding method for forming a welded joint having excellent properties when melt welding two steels, and more particularly, to improve the properties of the welded joint by propagating ultrasonic vibrations to the molten pool during melt welding. It relates to a welding method that can be done.
일반적으로 두 개의 강재를 용융 용접하여 용접이음부를 형성하는 경우, 강재는 용접열원에 의하여 급열 및 급냉을 겪게 되며 이때, 금속조직학적으로 그 부위는 결정립이 조대화되거나 취약한 조직으로 상변태가 발생하여 결국 모재 대비 품질 특성이 필연적으로 열화된다. In general, when two welded steels are welded to form a welded joint, the steel is subjected to rapid heat and quenching by a welding heat source. As a result, quality characteristics inevitably deteriorate compared to the base metal.
특히, 용융 이후 응고되는 용접이음부의 용접금속의 경우 응고 결정립들이 전체적으로 특정방향으로 성장하여 최종적으로 원주(columnar) 형태의 조대한 결정립이 형성되므로 충격 인성 등의 품질이 급격히 저하된다. 따라서, 용접금속의 결정립 조대화 현상을 극복하여 용접이음부 특성을 향상시키기 위한 방안이 요구되고 있다.In particular, in the case of the weld metal of the welded joint which is solidified after melting, the solidification grains grow in a specific direction as a whole, and finally coarse grains are formed in the columnar shape, and thus the quality of impact toughness is rapidly deteriorated. Therefore, there is a need for a method for improving weld seam characteristics by overcoming grain coarsening of weld metal.
종래에는 이러한 문제의 해결 수단으로서 저입열 다층용접시공을 통하여 고온에서의 노출시간을 줄여 결정립성장을 억제하고자 하였으나, 이는 여러 번 용접을 해야 한다는 단점을 가지고 있어 생산성에 악영향을 미칠 수 있다. Conventionally, as a means of solving the problem, the low heat input multilayer welding construction has been intended to suppress grain growth by reducing the exposure time at high temperature, but this has the disadvantage of having to weld several times, which may adversely affect productivity.
또한, 최근에는 레이져 혹은 전자빔 등의 고밀도 열원의 적용을 통하여 국부적인 용접이음부 형성과 빠른 냉각속도에 의하여 용접금속의 결정립 조대화 현상을 최대한 억제하려는 노력이 있으나, 상기 고밀도 열원을 적용하기 위해서는 고가의 장비가 필요하므로 산업계에 쉽게 도입하기에는 한계가 있는 실정이다. In addition, in recent years, efforts have been made to suppress grain coarsening of weld metals as much as possible by applying a high density heat source such as a laser or an electron beam to form a local weld joint and a high cooling rate. Because of the need for equipment, there is a limit to easily introduced into the industry.
한편, 일본 공개특허공보 1998-258363호에서는 용접전극에 유도코일을 장착시킴으로써 용융지에 자장을 통하여 교반함을 기재하고 있으나, 이는 용접부 품질의 특성 향상이 목적이라기보다는 고속용접시 발생하는 언더컷, 슬래그 혼입 등의 용접결함 저감을 목적으로 하고 있으며, 또한 본 발명자는 실험을 통하여 유도 자기장에 의한 용융지 교반을 여러 차례 시도해 보았으나, 현실적으로나 이론적으로 용융지 교반이 어렵다는 결론을 도출하였다.On the other hand, Japanese Laid-Open Patent Publication No. 1998-258363 describes that stirring is carried out through a magnetic field in a molten paper by attaching an induction coil to a welding electrode. In order to reduce welding defects, etc., the present inventors have tried several times of melt stirring by induction magnetic field through experiments, but have concluded that the melt stirring is difficult in practice and in theory.
본 발명은 상기한 종래의 문제점을 개선하기 위한 것으로, 용융 용접시 용융지에 초음파 진동을 전파함에 따라 용접이음부의 특성을 개선할 수 있는 용접방법을 제공하는데, 그 목적이 있다.The present invention is to improve the above-mentioned conventional problems, to provide a welding method that can improve the characteristics of the welded joint by propagating ultrasonic vibration to the molten pool during melt welding, an object thereof.
상기 목적을 달성하기 위한 본 발명은,The present invention for achieving the above object,
두 개의 강재를 용융용접하는 용접방법에 있어서, 용접하고자 하는 용접이음부에서 용접봉과 같은 속도로 용융지에 0.5㎛ 이상의 초음파 진동을 전파하는 것을 특징으로 하는 용접이음부 특성이 우수한 용접방법에 관한 것이다.In the welding method for welding two steel materials, the welding method is excellent welding seam characterized in that propagating ultrasonic vibration of 0.5㎛ or more to the molten paper at the same speed as the electrode at the welding joint to be welded.
이하, 본 발명을 상세하게 설명한다.EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.
본 발명자들은 모재와 대비하여 필연적으로 열화현상이 발생하는 용접이음부 특성을 획기적으로 향상시킬 수 있는 방안을 연구하던 중 용융된 이후 응고되는 용접금속은 조대한 원형(columnar) 형태의 응고 결정립이 생성되며, 이로 인하여 저온인성, 가공성, 부식특성 등에 해로운 영향을 미치는 것을 발견하였다. The inventors of the present invention have been studying ways to significantly improve the properties of welded joints, which inevitably cause deterioration, compared to the base metal, while the welded metal solidified after melting is formed into coarse circular solidified grains. As a result, it has been found to adversely affect the low temperature toughness, processability, corrosion characteristics.
조대한 응고 결정립의 생성 원인은 아래에서 상세히 설명한다.The cause of the formation of coarse coagulation grains is described in detail below.
용융금속의 응고시, 액상과 고상의 계면부분에서 고상의 셀상(cellular) 혹은 수지상정(dendritic)의 성장방향은 열전달이 이루어지는 반대방향과 등온선 (Thermal contour)의 수직방향으로 거시적으로 이루어지며, 결정학적으로는 <100> 방향을 따라서 우선 성장하게 된다. 따라서, 외부에 필드(field)를 가하지 않는 이상, 고상의 성장은 전체적으로 동일방향으로 일관되게 이루어지므로 최종적으로 생성되는 응고 결정립은 조대화될 수 밖에 없는 것이다.In the solidification of molten metal, the growth direction of the solid or dendritic phase at the interface between the liquid and solid phases is made macroscopically in the opposite direction to the heat transfer and in the vertical direction of the thermal contour. Academicly, they grow first along the <100> direction. Therefore, unless a field is applied to the outside, solid phase growth is consistently performed in the same direction as a whole, and thus the final coagulation grains are inevitably coarsened.
따라서, 이러한 응고 결정립의 조대화 현상을 억제하기 위해서는 응고가 개시되는 동안 고액 계면에 일정하게 분포되어 있는 등온선을 불균일하게 분포토록 만들어 고상성장 방향을 랜덤하게 만들거나, 혹은 생성되는 수지상정의 고상을 연속적으로 잘게 부셔준다면 미세한 결정립의 용접금속을 기대할 수 있을 것으로 판단하는데 이르렀다. Therefore, in order to suppress the coarsening phenomenon of the coagulation grains, the isotherm uniformly distributed at the solid-liquid interface during coagulation is unevenly distributed to randomize the solid phase growth direction, or to continuously generate the solid phase of the resulting dendrite. If it is crushed finely, it can be expected that a fine grain of weld metal can be expected.
이에 본 발명자는 상기 목적을 달성하기 위한 수단으로서, 용융금속의 액상내 난류(Turbulent flow)를 유도하는 것을 생각하였으며, 액상 내 난류의 유도를 위하여 가하는 외부 필드(field)로서, 초음파 진동을 인가함에 따라 용접금속의 결정립이 미세화되어 용접이음부 특성을 개선할 수 있다는 것을 새롭게 규명하고, 그 결과에 기초하여 본 발명을 완성하게 되었다.Accordingly, the inventors of the present invention considered to induce turbulent flow in the liquid phase of molten metal as a means for achieving the above object, and to apply ultrasonic vibration as an external field applied to induce turbulence in the liquid phase. Accordingly, it has been newly found that the crystal grains of the weld metal can be refined to improve weld seam characteristics, and the present invention has been completed based on the results.
이하, 본 발명의 용접금속의 결정립을 미세화하여 용접이음부 특성을 향상시키기 위한 용접방법에 대하여 상세히 설명한다.Hereinafter, a welding method for improving the weld seam characteristics by miniaturizing the crystal grains of the weld metal of the present invention will be described in detail.
도 1은 본 발명의 일 실시예에 따른 롤 형식의 초음파 진동 단자를 이용하여 초음파 진동을 전파하는 용융용접 공정을 보여주는 모식도이다. 상기 도 1에 나타낸 바와 같이, 본 발명의 용융대상 강재(11)의 용융용접시 용접봉(12)과 같은 속도로 용융지(13)에 0.5㎛ 이상의 초음파 진동을 전파하는 것이다. 상기 초음파 진동 진폭이 0.5㎛ 미만일 경우에는 초음파가 금속 내부를 통해 용융지에 전달되는 에너지가 미약하여 용접시 용융지의 난류가 발생되지 않아 용접금속의 결정립 미세화를 얻기 어려울 수 있다.1 is a schematic diagram showing a melt welding process of propagating ultrasonic vibrations using a roll type ultrasonic vibration terminal according to an embodiment of the present invention. As shown in FIG. 1, ultrasonic vibration of 0.5 μm or more is propagated to the
이때, 상기 용융지(13)에 초음파 진동을 전파하기 위하여 초음파 진동 단자가 이용될 수 있고, 초음파 진동을 전파할 수 있는 단자라면 어느 것이든 적용될 수 있으며, 일 실시예로서 롤 형식의 초음파 진동 단자(14)가 적용될 수 있다. In this case, an ultrasonic vibration terminal may be used to propagate the ultrasonic vibration to the
또한, 상기 초음파 진동단자는 상기 용융지로부터 60mm 이하의 거리를 유지하며 이동하는 것으로서, 진동단자와 용융지와의 거리가 60mm를 초과하는 경우에는In addition, the ultrasonic vibration terminal is to move while maintaining a distance of 60mm or less from the molten paper, when the distance between the vibration terminal and the molten paper exceeds 60mm
초음파 진동이 금속내부를 통해 전파하는 과정 중 에너지가 점차 소멸되어 결국은 용융지에서의 난류를 시키기에 부족할 수 있다.During the propagation of ultrasonic vibrations through the metal, the energy gradually dissipates and may eventually be insufficient for turbulence in the melt.
본 발명에 따르면, 용융 용접시 용융지에 초음파 진동을 전파함에 따라 용접금속의 결정립이 미세화되어 용접이음부 특성을 개선된 용접방법을 제공할 수 있는 효과가 있다.According to the present invention, as the ultrasonic vibration propagates to the molten pool during melt welding, the crystal grains of the weld metal may be miniaturized, thereby providing a welding method having improved weld seam characteristics.
(실시예)(Example)
발명예(1~15) 및 비교예(16~20)의 대상 강재는 STS409L 냉연재이며, 두께는 1.5mm이다. 이러한 강재를 GTAW (Gas Tungsten Arc Welding) 방법을 사용하여 용접하였으며, 용접조건은 전류 120A, 전압 25V, 용접속도 320mm/min을 적용하였다. The steel materials of the invention examples (1-15) and the comparative examples (16-20) are STS409L cold-rolled materials, and thickness is 1.5 mm. These steels were welded using GTAW (Gas Tungsten Arc Welding) method, and the welding conditions were applied to current 120A, voltage 25V, and welding speed 320mm / min.
용접과 동시에 초음파 진동을 용융지에 인가하기 위하여 롤타입의 초음파 진동 단자를 사용하여 용접토치 후행의 강재표면에 부착 후 용접선 수직방향으로 20~40kHz 주파수로 진동을 부과하였다. 초음파 진동을 위한 출력은 800~2.2kW를 사용하였으며, 주파수와 출력의 여러 가지 조합으로부터 진폭을 0.5~4.0㎛로 변화를 주며 실험을 실시하였다.In order to apply ultrasonic vibration to the molten paper at the same time as welding, vibration was applied at the frequency of 20 ~ 40kHz in the vertical direction of the welding line after attaching to the steel surface following the welding torch using the roll type ultrasonic vibration terminal. 800 ~ 2.2kW was used as the output for ultrasonic vibration, and the experiment was conducted with varying amplitude from 0.5 to 4.0㎛ from various combinations of frequency and power.
실험 후 용접금속의 결정립들을 비교 관찰하였으며, 충격인성시험을 실시한 후, 그 결과를 표 1에 나타내었다. After the experiment, the grains of the weld metal were compared and observed. After the impact toughness test, the results are shown in Table 1.
상기 표 1에 나타난 바와 같이, 본 발명의 조건을 만족하도록 초음파 진동을 부가한 발명예(1~15)의 경우, 진폭의 크기와 관계없이 용접금속 결정립 크기가 약 120~200㎛로서 미세화됨을 알 수 있다. As shown in Table 1, in the case of the invention examples (1 to 15) to which the ultrasonic vibration was added to satisfy the conditions of the present invention, it can be seen that the weld metal grain size is reduced to about 120 to 200 μm regardless of the amplitude of the amplitude. Can be.
이에 따라, 저온 충격인성값은 평균 15J로서, 모두 상부 충격인성치(upper shelf energy)영역에 존재함을 알 수 있으며 산포의 폭도 좁아지는 것을 알 수 있다. Accordingly, the low temperature impact toughness value is 15J on average, and it can be seen that all of them exist in the upper shelf energy region and the width of the dispersion becomes narrower.
반면, 초음파 진동을 인가하지 않은 비교예(16~20)의 경우 결정립 크기는 약 400~500㎛ 범위에 있으며, -20℃에서의 저온 샤르피 충격인성값은 평균 8J이며 분포는 3J~17J로서 상당히 큰 폭의 산포가 존재함을 알 수 있다. On the other hand, in the case of Comparative Examples (16-20) without applying ultrasonic vibration, the grain size is in the range of about 400 ~ 500㎛, low temperature Charpy impact toughness value at -20 ℃ average 8J and distribution is 3J ~ 17J considerably It can be seen that there is a large spread.
이는 충격인성값이 상부 충격인성치(upper shelf energy)와 하부 충격인성치 (lower shelf energy)사이에 큰 폭에 걸쳐 존재함을 의미하며 따라서 이 온도 근처에서 DBTT (Ductile-Brittle Transition Temperature)가 존재한다는 것을 예측할 수 있다. This means that the impact toughness value is wide between the upper shelf energy and the lower shelf energy, so there is a DBTT (Ductile-Brittle Transition Temperature) near this temperature. Can be predicted.
또한, 도 2는 본 발명의 초음파 진동 부과 여부에 따른 전형적인 용접금속의 결정립 크기를 나타내었다. 상기 도 2에 나타난 바와 같이, 본 발명에 따라 초음파 진동 부과시 기존 초음파 진동을 부과하지 않는 용접방법에 비하여 상당한 결정립 미세화(460㎛→130㎛)가 구현됨을 잘 알 수 있다.In addition, Figure 2 shows the grain size of a typical weld metal depending on whether the ultrasonic vibration of the present invention. As shown in FIG. 2, it can be seen that substantial grain refinement (460 μm → 130 μm) is realized in comparison with a welding method that does not impose conventional ultrasonic vibrations when applying ultrasonic vibrations according to the present invention.
도 1은 본 발명의 일 실시예에 따른 롤 형식의 초음파 진동 단자를 이용하여 초음파 진동을 전파하는 용융용접 공정을 보여주는 모식도이다. 1 is a schematic diagram showing a melt welding process of propagating ultrasonic vibrations using a roll type ultrasonic vibration terminal according to an embodiment of the present invention.
도 2는 본 발명의 초음파 진동 부과 여부에 따른 전형적인 용접금속의 결정립 크기를 나타낸다.Figure 2 shows the grain size of a typical weld metal according to the application of the ultrasonic vibration of the present invention.
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| JPH1080765A (en) * | 1996-09-04 | 1998-03-31 | Mitsubishi Heavy Ind Ltd | Welding method, and its equipment |
| JPH10296461A (en) * | 1997-04-25 | 1998-11-10 | Kumakura:Kk | Ultrasonic vibration welding method |
| US6223974B1 (en) | 1999-10-13 | 2001-05-01 | Madhavji A. Unde | Trailing edge stress relief process (TESR) for welds |
| JP2001225166A (en) * | 2000-02-16 | 2001-08-21 | Daihatsu Motor Co Ltd | Welding method for consumable electrode type arc welding |
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| JPH1080765A (en) * | 1996-09-04 | 1998-03-31 | Mitsubishi Heavy Ind Ltd | Welding method, and its equipment |
| JPH10296461A (en) * | 1997-04-25 | 1998-11-10 | Kumakura:Kk | Ultrasonic vibration welding method |
| US6223974B1 (en) | 1999-10-13 | 2001-05-01 | Madhavji A. Unde | Trailing edge stress relief process (TESR) for welds |
| JP2001225166A (en) * | 2000-02-16 | 2001-08-21 | Daihatsu Motor Co Ltd | Welding method for consumable electrode type arc welding |
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