JPH0740051A - Welding method and apparatus for steel structure - Google Patents

Abstract

PURPOSE:To provide the method and equipment for welding a steel structure capable of performing welding on-line with satisfactory preheating efficiency at little consumption of electric power. CONSTITUTION:The welding equipment of the steel structure is constituted of an induction heating coil 5 of the specified length having almost the same cross-sectional shape as a groove 4 of a weld zone and a welding equipment main body 2 to be arranged at the rear side in the welding direction of the induction heating coil 5, preheating is carried out by the induction heating coil 5 which is inserted and arranged into the groove 4 of the weld zone and then, welding is performed continuously in the preheated range by the welding equipment main body 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding method of a steel structure used for corner joint welding of a box column in construction, and a welding apparatus used for carrying out the method.

[0002]

2. Description of the Related Art In recent years, with the increase in the size of structures, the steel materials used have become thicker and stronger. However, as the steel material becomes thicker and stronger, cold cracking occurs due to diffusible hydrogen in the weld metal.Therefore, in order to prevent cold cracking, diffusible hydrogen in the weld metal should be avoided. In addition to selecting a small amount of welding method and welding material, it is necessary to perform preheating or postheating that facilitates escape of hydrogen that has entered the weld. The preheating temperature is the amount of diffusible hydrogen,
It depends on the composition of the steel material, the plate thickness, the degree of restraint of the welded part, etc. Generally, up to 490 MPa steel is carried out without preheating, but it is 580
MPa steel is preheated to about 120 ° C, and 780 MPa steel is preheated to about 150 ° C. Gas burner heating and electric resistance heating are used for preheating steel materials, but induction heating is also proposed in Japanese Utility Model Publication No. 4-15422.

By the way, in the corner joint welding of a building box column which is a large-sized thick plate structure, as shown in FIG. 6, after two steel materials 20A and 20B are temporarily assembled in a box shape,
Formed by upper steel 20A and both steels 20B 2
A plurality of electric resistance heating devices 22 are installed so as to cover the groove 21 of the welded portion of the book, while the electric resistance heating devices 22 are installed on the steel materials 20B on both sides, or the steel materials 20A on the lower side and the steel materials on both sides are installed. A plurality of electric resistance heating devices 22 are installed so as to cover the two grooves 21 formed by 20B and 20B, and the upper and right and left three surfaces or the upper and lower two surfaces are simultaneously heated. Is going by.

[0004]

However, in the above-mentioned conventional welding method, the groove 2 is formed by the electric resistance heating device 22.
Since the No. 1 is indirectly preheated, the preheating efficiency is poor, the preheating takes too long, and the preheating is performed by welding and offline, resulting in poor work efficiency. In addition, a large amount of power is consumed for preheating, which causes a rise in manufacturing cost.

Therefore, it is possible to use the induction heating described in Japanese Utility Model Publication No. 4-15422, but in a large structure of a thick plate such as a box pillar for construction, the heating facility becomes large. There is an inconvenience that it is not practical.

The present invention has been made to solve the above problems. A first object of the present invention is to provide a steel structure capable of simultaneously improving the efficiency of welding work, improving the welding quality and reducing the power cost. It is to provide a welding method. Also,
A second object of the present invention is to provide a welding method for a steel structure, which can improve welding quality in particular. Further, a third object of the present invention is to provide a simple and inexpensive welding apparatus for a steel structure capable of reliably carrying out the above welding method.

[0007]

In order to achieve the above-mentioned first object, the method for welding a steel structure according to the first aspect of the present invention uses the induction heating coil inserted into the groove of the welded portion to perform the welding. After preheating the groove of the part, welding is continued in the preheated area.

In order to achieve the second object,
A welding method for a steel structure according to a second aspect of the present invention is that the welding in the above welding method is performed by AC gas shielded arc welding using an electrode wire having a diameter of 2.4 mm or more.

Further, in order to achieve the above third object,
A welding apparatus for a steel structure according to a third aspect of the present invention is an induction heating coil having a constant length, which is inserted and arranged in a groove of a welded portion and has a cross-sectional shape substantially the same as that of the groove, and the induction heating coil. The welding device main body is arranged on the rear side in the welding direction.

[0010]

According to the method for welding a steel structure according to the first aspect of the present invention, a magnetic path passing through both sides and the bottom of the groove is formed in the base metal, and an eddy current formed around the magnetic path. It is possible to directly preheat the groove to the bottom where the first layer bead is formed by the Joule heat due to. In addition, by performing welding in the preheated range subsequent to preheating, preheating and welding can be performed online.

According to the method for welding a steel structure according to the second aspect of the invention, the gas shielded arc welding is performed by generating an arc between the electrode wire and the base material in a shield gas atmosphere. Since the electrode wire has a diameter of 2.4 mm or more, which has a small surface area per unit volume and is hard to be oxidized, the amount of diffusible hydrogen in the weld metal can be reduced. In addition, the welding current can be increased in combination with the use of alternating current to increase the amount of welding per unit time, and thus the preheating temperature can be significantly lowered.

Further, according to the welding apparatus for a steel structure according to the third aspect of the present invention, after the preheating by the induction heating coil, the main body of the welding apparatus performs the online preheating in the preheated range and subsequently performs the welding. Therefore, it can be used for implementing the first and second inventions.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing an entire welding apparatus according to the present invention, FIG. 2 (1) is a perspective view showing an induction heating apparatus in the welding apparatus, (2) is a front sectional view of (1), and FIG. Three
(1), (2) and (3) are different groove shape diagrams.

The welding apparatus according to the present invention is an induction heating apparatus 1
And a welding device main body 2, and an induction heating device 1 is provided on the front side in the welding direction indicated by the arrow with respect to the groove 4 of the weld formed by the steel material 3A and the steel material 3B, and a welding device is provided on the rear side. The main bodies 2 are arranged and used. Usually, the groove 4 is used for welding a corner joint of a building box column as shown in FIG.
The V-shape of (1), the U-shape of (2) in the figure, and the R-shape of (3) in the figure are considered.

The induction heating device 1 comprises an induction heating coil 5, a matching transformer 6 and a high frequency oscillator (not shown). Needless to say, a low frequency oscillator or the like may be used instead of the high frequency oscillator.

The induction heating coil 5 has a fixed length of, for example, about 150 mm to 200 mm, which is inserted into the groove 4, and has a rigid coil portion 5A, and the groove 4 side of the groove insertion portion 5a of the rigid coil portion 5A. And an iron core 5B fixed to the opposite side, and the base end of the rigid coil portion 5A is connected to the matching transformer 6.

The groove insertion portion 5a of the rigid coil portion 5A has substantially the same sectional shape as the groove 4, and the surface of the groove insertion portion 5a facing the groove surface 4a of the groove 4 is made of an insulating material. 7 is provided. An iron core fixing portion 5b is formed on the opposite side of the groove inserting portion 5a from the groove 4 side, and a ridge portion 5c extending along the axial direction is formed on the iron core fixing portion 5b.

Further, the iron core 5B is constructed by stacking a large number of substantially rectangular electromagnetic steel plates 8 (for example, silicon steel plates) having a recess 8a formed in the central portion of one long side in the lateral direction. The concave portion 8a is fixedly mounted on the iron core fixing portion 5b in a state of being engaged with the ridge portion 5c of the rigid coil portion 5A.
The direction of easy magnetization of the electromagnetic steel plate 8 in the iron core 5B is perpendicular to the insertion direction of the induction heating coil 5 with respect to the groove 4 (vertical direction in FIG. 2).

Induction heating coil 5 constructed as described above
Is used by being inserted into the groove 4 so that a minute gap (for example, about 1 mm) is maintained between the insulating material 7 and the groove surface 4a of the groove 4.

Further, the welding apparatus main body 2 is for conventionally known gas shielded arc welding, and one or a plurality of welding torches 9 composed of an electrode tip, an electrode wire and a shield gas nozzle (not shown) are arranged in the welding direction. Prepared at regular intervals. In the embodiment, the electrode wire has a diameter of 2.4 mm.
The above is used to energize alternating current.

With the above construction, the following preheating and welding are continuously performed on the entire length of the welded portion. That is, the induction heating coil 5 is applied by applying an induction current to the rigid body coil portion 5A via the matching transformer 6 by the high frequency oscillator.
Induction heating is performed by directly preheating a certain range of the groove 4, and then the preheating device 1 and the welding device main body 2 are moved integrally or separately in the welding direction. The welding torch 9 subsequently performs gas shielded arc welding online on the preheated area.

In order to achieve effective preheating, a large number of electromagnetic steel plates 8 are laterally overlapped to form the iron core 5 of the induction heating coil 5.
By forming B and making the direction of easy magnetization perpendicular to the direction of insertion into the groove 4, the magnetic path P with less divergence of magnetic flux is formed. It goes without saying that preheating is possible even without.

Next, a method for welding a steel structure according to the present invention will be described.

This welding method is embodied in a welding operation by the above welding apparatus. First, the groove 4 of the welded portion is preheated by the induction heating coil 5 inserted and arranged in the groove 4 of the welded portion. After that, the gas shielded arc welding is successively performed on the preheated area.

Since the induction heating coil 5 is inserted and arranged in the groove 4, both side portions 4b of the groove 4 are passed through the iron core 5B in the base material (steel materials 3A, 3B) by the electromagnetic induction of alternating current.
A magnetic path P passing through the bottom portion 4c and the bottom portion 4c is formed, and the groove 4 is reliably preheated to the bottom portion 4c where the first layer bead is formed by Joule heat due to the eddy current formed around the magnetic passage P.
Since the magnetic path P with less divergence of the magnetic flux is obtained due to the easy magnetization direction of the iron core 5B, the above preheating becomes more reliable. Further, since the gas shield arc welding is continuously performed on the preheated area, the welding can be performed online with the preheating.

The gas shielded arc welding is carried out by generating an arc between the electrode wire and the base material (steel materials 3A, 3B) in a shield gas atmosphere supplied from a shield nozzle. When a wire having a diameter of 2.4 mm or more is used, as shown in FIG. 4, the surface area per unit volume of the wire is small and it is difficult to oxidize, so that the amount of diffusible hydrogen in the weld metal can be reduced. This results in a weld quality with less cold cracking.

Further, since the electrode wire having a diameter of 2.4 mm or more is used, the welding current can be increased in combination with the fact that the used current is an alternating current, which enables the welding per unit time in the high heat input welding. The amount can be increased to significantly lower the preheat temperature. For this reason, the preheating of the groove 4 is sufficiently performed by the above-mentioned induction heating, and the gas shield arc welding performed subsequent to the preheating can be ensured.
Not only 0MPa steel but also 780MPa steel can be fully supported. In addition, gas shielded arc welding has an advantage of less deterioration of joint performance because the cooling rate after welding is faster than that of submerged arc welding. Furthermore, since the preheating temperature can be significantly lowered, the heating capacity of the induction heating device 1 can be small, or the heating capacity can be increased to improve the preheating efficiency and increase the welding speed.

Submerged arc welding may be used instead of gas shield arc welding. In the case of submerged arc welding, as shown in FIG. 5, the flux supply tube 10 is inserted and arranged between the induction heating coil 5 and the electrode wire, and after passing through the induction heating coil 5, the flux 11 is supplied and dispersed to weld the welded portion. Should be covered.

[0030]

As described above, in the method for welding a steel structure according to the first aspect of the present invention, after the groove of the welded portion is preheated by the induction heating coil inserted and arranged in the groove of the welded portion, it is preheated. Since the welding is performed successively for the range, it is possible to reliably perform the welding online after the preheating. Therefore, it is possible to significantly improve the efficiency of welding work, improve the welding quality, and significantly reduce the amount of electric power as compared with the conventional case.

In the method for welding a steel structure according to the second aspect of the present invention, the welding in the above welding method is performed by AC gas shield arc welding using an electrode wire having a diameter of 2.4 mm or more. The amount of diffusible hydrogen can be reduced. In addition, the welding current can be increased in combination with the fact that the used current is an alternating current to increase the amount of welding per unit time. Therefore, not only the welding quality can be further improved, but also the preheating temperature can be low,
The heating capacity of the induction heating coil can be reduced, or the efficiency of welding work can be improved.

Further, the welding apparatus for steel structure according to the third aspect of the present invention comprises an induction heating coil having a constant length and having a cross-sectional shape substantially the same as that of the groove, which is inserted and arranged in the groove of the welded portion. Since the welding apparatus main body is arranged on the rear side of the induction heating coil in the welding direction, the above-mentioned welding method can be performed reliably, and the equipment is simpler and less expensive than the conventional equipment.

[Brief description of drawings]

FIG. 1 is a perspective view showing an entire welding apparatus according to the present invention.

FIG. 2 (1) is a perspective view showing an induction heating device in the welding device. (2) It is a front sectional view of (1).

FIG. 3 (1) is a groove shape diagram. (2) It is a groove shape figure. (3) It is a groove shape figure.

FIG. 4 is a diagram showing the amount of diffusible hydrogen in the weld metal with respect to the wire diameter used in gas shielded arc welding.

FIG. 5 is a conceptual diagram for explaining a welding method in the case of submerged arc welding using the welding device according to the present invention.

FIG. 6 is a perspective view showing one usage mode of a conventional preheating method. (2) It is a perspective view showing another usage mode of the conventional preheating method.

[Explanation of symbols]

 1 Induction heating device 2 Welding device main body 4 Weld groove 5 Induction heating coil

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Toru Iezawa 3-4-5 Toyosu, Koto-ku, Tokyo Tomoe Co., Ltd. (72) Inventor Kanaya Ken 3-4-5 Toyosu, Koto-ku, Tokyo Tomoe Co., Ltd. (72) Inventor Yukihiko Horii, 20-1 Shintomi, Futtsu, Chiba, Nippon Steel Research & Co., Ltd. (72) Inventor, Kunio Koyama 20-1, Shintomi, Futtsu, Chiba, Japan (72) Inventor Shosuke Ushijima, 2-7-16 Ginza, Tobata-ku, Kitakyushu, Fukuoka Prefecture

Claims (3)

[Claims] 1. A method for welding a steel structure, comprising preheating the groove of the welded portion by an induction heating coil inserted and arranged in the groove of the welded portion, and subsequently performing welding in the preheated area. . 2. The method for welding a steel structure according to claim 1, wherein the welding is performed by AC gas shield arc welding using an electrode wire having a diameter of 2.4 mm or more. 3. An induction heating coil inserted into the groove of the welded portion and having a cross-sectional shape substantially the same as that of the groove, and an induction heating coil disposed behind the induction heating coil in the welding direction. A welding device for a steel structure, comprising: a welding device main body.