JP3224693B2 - Vertical narrow groove GMA welding method for stainless steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vertical narrow groove GMA welding method for stainless steel.

[0002]

2. Description of the Related Art The demand for stainless steel structures as liquefied natural gas transport ships and storage tanks is increasing and the size is increasing. When joining thick plates, the required amount of welding metal is small and the number of welding steps is small. Attempts have been made to apply the vertical narrow groove GMA welding method for reasons such as cost reduction, and it is common to swing the arc at the tip of the wire by oscillating the welding torch horizontally like a pendulum. It is a target. In this case, as shown in the side sectional view of FIG.
Since the stainless steel base material 1 has a low thermal conductivity, the welded portion is hardly cooled, the molten metal 22 drips down under the influence of gravity, and the molten metal 22 easily flows to the surface side of the welded metal 21. As a result of the action to be retained, the distance B between the tip of the wire 8 and the stainless steel base material 1 becomes longer, and the molten metal 22 that has flowed down hinders the heat of the arc from directly hitting the stainless steel base material 1. Cushion action occurs, penetration C is small, poor fusion occurs,
Particularly at the groove corner, the rate of occurrence of defective fusion is high, resulting in a disadvantage that good bead formation in a narrow groove is impaired and that high quality weld metal 21 is hardly formed.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been proposed in view of the above circumstances, and it is possible to reliably direct an arc to the vertical narrow corner and the wall surface of stainless steel, and to form a molten metal. A stainless steel stand that provides stable and sufficient penetration without disturbing, prevents dripping of the bead surface, and provides high quality and good welded joints with beautiful bead appearance and no welding defects. It is an object of the present invention to provide a method of narrowing and narrowing groove GMA welding.

[0004]

In order to achieve the object, according to the present invention, when a vertical narrow groove of stainless steel is subjected to GMA welding, a tip and a shield nozzle which bend the wire at an appropriate angle with respect to the axial direction at the tip are provided. The tip of the wire is repeatedly oscillated symmetrically in an arc in the opposite direction to the direction of the upward welding, and the oscillation speed is higher in the downward oscillation than in the upward oscillation, and the welding current and voltage are increased. Is characterized in that the gas shield welding is performed at a lower time during the downward oscillation than during the upward oscillation.

[0005]

In the vertical narrow groove GMA welding method for stainless steel according to the present invention, the wire is forcibly bent at an angle of 5 to 20 ° at the tip of the tip, and the tip of the wire is directed in the vertical narrow groove in the welding direction. The welding is performed while repeatedly oscillating in an arc shape in the direction opposite to the above, so that the molten metal does not function as an obstacle at the corner of the groove, and the poor fusion is eliminated. In other words, the molten metal is affected by the surface tension and gravity, but the arc shaped oscillating on the lower chord side can reliably direct the arc to the groove corner and the wall surface, and the heat of the arc is not disturbed by the molten metal. It can be supplied directly to the base material, and the heat input to the base material in this part increases, resulting in stable and sufficient penetration. In addition, since the moving distance traversing the narrow groove is longer in the case of an arc-shaped oscillate than in the case of a pendulum-shaped
As a result, it is difficult to form one pool within the narrow groove, and the amount of excess molten metal is reduced. As a result, a weld bead having a beautiful appearance with less dripping, which tends to occur when the amount of molten metal is large, is obtained. Further, if a flat shield nozzle and a double shield nozzle are used in combination, the gas shield effectively functions to prevent the occurrence of blow holes.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an embodiment of the present welding method, and FIG. 2 is an oscillating locus of the present welding method. FIG. 3 is an explanatory view showing an oscillating procedure of the main welding method, FIG. 4 is a side sectional view showing a penetration state of the main welding method, and FIG. 5 is a GMA applied to the main welding method.
It is a perspective view of a welding torch.

First, a GMA welding torch applied to the present welding method will be described with reference to FIG. 5. A tip rotating shaft 5 is installed vertically inside a flat shield nozzle 4 provided at the tip of a GMA welding torch main body 3. , Tip 6 of coaxial 5
Is screwed, and a wire lead-out hole 7 bent at 5 to 20 ° with respect to the axial direction is formed in the chip 6, and a wire 8 is led out from the tip thereof. In addition, the tip rotating shaft 5
Is connected to a motor 11 through a pair of gears 9 and 10 disposed at the base of the body 3 through the GMA welding torch body 3, and the motor 11 is a stepper capable of detecting an oscillating position and controlling a speed. A motor is provided.
Further, inside the shield nozzle 4, a plurality of shield gas supply pipes 12 are provided and connected to the shield gas inlet 13, and a plurality of water supply pipes 14 and drain pipes 15 are provided so that the cooling water inlet 16, the cooling water The shield nozzle 4 is connected to an outlet 17, and a detachable double shield nozzle 18 is fitted to the base end of the shield nozzle 4 to enhance the gas shielding effect.

[0008] Referring to FIGS. 1 to 4, a description will be given of a method of performing a vertical narrow groove GMA welding of stainless steel using such a GMA welding torch. First, in FIG. The shield nozzle 4 is vertically inserted into the vertical narrow groove 2 to generate an arc between the wire 8 bent and projected from the tip of the tip 6 and the stainless steel base material 1, and the shield nozzle Welding is performed while ejecting a shield gas from the nozzle 4 and moving the shield nozzle 4 in the welding advancing direction 19 to form a weld metal 21. At this time, the tip rotating shaft 5 is rotated by the rotation of the motor 11 shown in FIG. 5 through the gear pairs 9 and 10, and the tip of the wire 8 protruding from the tip 6 is formed into an arc shape in the direction opposite to the welding traveling direction 19. It is oscillated repetitively symmetrically like the oscillation trajectory 20. As shown in FIG. 2, the oscillating trajectory 20 repeatedly turns at the groove corner 2a and moves upward along the welding traveling direction 19.

By the oscillating operation of the oscillating locus 20, the tip of the wire 8 changes to the position 8 'as shown in FIG. 3, and when the turning angle of the tip 6 is 180 °, the amplitude becomes maximum, and the tip 6 turns more. As the angle decreases, the amplitude decreases in proportion to the amplitude of the wire 8. Thus, the wire lead-out hole 7 bent by 5 to 20 ° with respect to the axial direction of the chip 6
The tip of the wire 8 derived from the above is repeatedly oscillated symmetrically in an arc shape in a direction opposite to the welding advancing direction 19 by the rotation of the tip 6, so that the tip of the wire 8 with respect to the groove corner 2 a of the vertical narrow groove 2 is formed. As a result, as shown in FIG. 4, the molten metal 22 flows below the arc point, and the heat of the arc can be supplied directly to the stainless steel base material 1 as shown in FIG. Is obtained. Further, in the arc-shaped oscillate based on the oscillating trajectory 20, the oscillating speed is increased at the time of the downward oscillating downward 20a indicated by the dotted line in FIG. This makes it possible to further increase and stabilize the penetration of the groove corner 2a and the groove wall surface 2b (FIG. 3), and to prevent the bead surface from dripping due to the influence of gravity. By making the welding current and voltage lower at the time of the downward oscillating 20a than at the time of the upward oscillating 20b, the amount of penetration can be increased, and when the oscillating locus 20 is reversed, it is temporarily stopped. If a current higher than the base current is supplied during this stop time, a more preferable welded portion can be obtained.

Next, as a specific example of the present welding method, an austenitic stainless steel (SUS30) having a thickness of 50 mm will be described.
4) For I type narrow groove with groove width of 18mm, wire diameter 1.2
mm flux cored wire, outlet hole diameter 1.5 mm, outlet hole angle 15 °, welding conditions 100 to 180 A, welding voltage 20 to 24 V, shielding gas CO ₂ , welding speed 5 to 10 cm / min, descending Speed 450-550DE
Welding was performed at G / sec, an ascending speed of 400 to 500 DEG / sec, and an oscillating end stop time of 0.5 to 1.0 sec, and a stable penetration of 1-2 mm on each side in the groove wall surface direction and the plate thickness direction was obtained.

Thus, according to the vertical narrow groove GMA welding direction, the arc-shaped oscillate at the tip of the wire 8 is repeatedly and symmetrically repeated in a direction opposite to the welding advancing direction 19 in the vertical rising welding. Further, even in the case of the arc shape, by increasing the oscillating speed for the downward oscillating 20a and decreasing the oscillating speed for the upward oscillating 20b, a stable and satisfactory penetration C can be obtained without being disturbed by the molten metal 22. In addition, dripping of the bead surface can be prevented. The cross-section of the bead has a groove corner 2a and a wall 2b.
And the central part of the groove has a slightly shallower omega shape compared to that, and a beautiful bead appearance on the surface can be obtained. Further, since the wire 8 can be accurately guided to the tip end of the tip 6 via the tip rotating shaft 5, the wire 8 can be surely directed particularly to the groove corner 2a and the wall surface 2b where fusion is likely to occur. It is possible to adjust the target position of the arc and the stop time at both ends of the groove in real time. It is important to completely shield the arc atmosphere from the atmosphere in the case of a thick plate with a deep narrow groove from the viewpoint of preventing welding defects such as blow holes. However, in this welding method, the arc can be inserted into the vertical narrow groove 2. By using the flat shield nozzle 4 and the double shield nozzle 18 together, the effect of the gas shield in the lamination from the groove bottom to the finishing layer on the groove surface can be improved, and the occurrence of blow holes can be prevented. In addition, this welding method makes it possible to perform high-quality vertical narrow groove GMA welding of a thick stainless steel plate having a thickness of 50 mm or more, and greatly improves welding efficiency.

[0012]

In summary, according to the present invention, when GMA welding a vertical narrow groove of stainless steel, a tip and a shield nozzle for bending a wire at an appropriate angle with respect to the axial direction at the tip are inserted into the narrow groove. The tip of the wire is repeatedly oscillated symmetrically in an arc in the direction opposite to the direction of the upward welding, so that the oscillation speed is higher in the downward oscillation than in the upward oscillation, and the welding current and voltage are downward. By performing gas shield welding at lower oscillation than during upward oscillation, the arc can be reliably directed to the upright narrow corners and wall surfaces of stainless steel, and stable without being disturbed by molten metal In addition, sufficient penetration can be obtained, dripping of the bead surface can be prevented, and a high quality and good welded joint having a beautiful bead appearance and no welding defects can be obtained. Since obtaining a vertical position narrow gap GMA welding method stainless steel, the present invention is extremely useful industrially.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of an upright narrow groove GMA welding method for stainless steel according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an oscillating locus of the present welding method.

FIG. 3 is an explanatory diagram showing an oscillating procedure of the present welding method.

FIG. 4 is a side sectional view showing a penetration state of the present welding method.

FIG. 5 is a perspective view of a GMA welding torch applied to the present welding method.

FIG. 6 is a side sectional view showing a penetration state of a conventional welding method.

[Explanation of symbols]

 Reference Signs List 1 stainless steel base material 2 vertical narrow groove 2a groove corner 2b groove wall 3 GMA welding torch body 4 shield nozzle 5 tip rotating shaft 6 tip 7 wire lead-out hole 8 wire 9, 10 gear 11 motor 12 shield gas Supply pipe 13 Shield gas inlet 14 Water supply pipe 15 Drain pipe 16 Cooling water inlet 17 Cooling water outlet 18 Double shield nozzle 19 Welding direction 20 Oscillate trajectory 20a Downward oscillate 20b Upward oscillate 21 Weld metal 22 Molten metal

──────────────────────────────────────────────────続 き Continuing from the front page (72) Masaru Matsumoto 1-1, Akunouracho, Nagasaki-shi Mitsubishi Heavy Industries, Ltd. Inside Nagasaki Shipyard (72) Inventor Minoru Takeda 1-1-1, Akunouracho, Nagasaki-shi Mitsubishi Heavy Industries, Ltd. In Nagasaki Shipyard (56) References JP-A-7-136765 (JP, A) JP-A-7-290243 (JP, A) JP-A-50-147450 (JP, A) JP-A-51-37849 (JP, A) A) JP-A-5-8045 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 9/12 B23K 9/022 B23K 9/095 B23K 9/173

Claims (1)

(57) [Claims] 1. In GMA welding of a vertical narrow groove of stainless steel, a tip and a shield nozzle for bending the wire at an appropriate angle with respect to the axial direction at the tip are inserted into the narrow groove, and the tip of the wire is moved upward. Oscillates symmetrically in an arc in the opposite direction to the direction in which the welding progresses, making the oscillation speed faster during downward oscillation than during upward oscillation, and increasing the welding current and voltage during upward oscillation during downward oscillation. A vertical narrow groove GMA welding method for stainless steel, wherein gas shield welding is performed at a lower temperature.