CS210644B2 - Method of three-electride arc welding from metal being in inert gas and equipment for making the same - Google Patents

Abstract

1327733 Welding by fusion MITSUBISHI JUKOGYO KK 14 Feb 1972 [24 Feb 1971] 6783/72 Heading B3R In flat position, open-square, butt MIG welding of thick plates 10, each of a plurality of weld metal layers is effected by three wire electrodes 5A-5C which are moved together relative to the plates 10, the electrodes 5A, 5C leading and acting in a clip transfer mode to effect fillet welding at the weld groove sides, and the electrode 5B following and acting in a spray-transfer mode to fill in between the fillet weld beads. The electrodes 5A-5C are arranged at the corners of a scalene or isosceles triangle, and may be of the same or different sizes, e.g. the electrodes 5A, 5C may be of small diameter (e.g. 1 mm.) and the electrode 5B of larger diameter. The electrodes 5A-5C are fed by devices 14C-14C from reels 8A-8C through contact tubes 4A-4C housed in a shielding gas cup 2 and located by an insulating spacer (3). The contact tubes 4A, 4C are angled outwardly (e.g. 45 degrees) at the ends, and the contact tube 4B is straight. Cooling water tubes (7A-7C) are disposed in contact with the contact tubes. Welding transformers 6A-6C feed current to the electrodes. Pre- and post-heating may be dispensed with, the electrodes (15A), (15C) effecting pre-heating for the bead laid by the electrode (15B) and the electrode (15B) effecting post-heating for beads laid by the electrodes (15A), (15C). The workpiece weld preparation edges need only be flame-cut.

Description

BACKGROUND OF THE INVENTION The present invention relates to a three-electrode arc welding process of metal in an inert gas of I-shaped grooves in a plane position. The invention further relates to an apparatus for carrying out the method mentioned above.

Butt-welding of thick plates, for example in the manufacture of pressure vessels, etc. for chemical production machines, propulsion machines and atomic force plants, has so far been carried out in most cases with a burnt welding arc. More recently, efforts have been made to use either Etruscan welding or arc welding of metal · in inert gas to improve weld efficiency and quality. The first method, since it requires a large heat input for welding, requires refining or refining the formed weld at elevated temperatures. The second method is also disadvantageous in that there are defects in the products, in particular in the contact surfaces, in particular in arc welding of metal in an inert gas. In order to overcome such difficulties, a single-layer, two-pass process has been proposed in which welding wires are used in a tandem position for welding in a " narrow " groove ¹ with a lower heat input than previously used for small-size electrodes. Nevertheless, this known method has welding deficiencies as shown in FIG. 1 when welding thick plates. According to this method, the weld fillet on the groove walls is preferably made by bending the welding wires 5 held in tandem in such a way that one of the wires passes earlier and is followed by another. For perfect welding with a single-layer two-pass process, the welding wire guide must be kept in a precisely determined position by precise control. Otherwise, acute weld heels between the weld beads 11, irregularly rounded welds, unevenly joined portions, and / or other defects result. FIG. 2 shows the cover cup 2, the touch tube 4, the inert gas 9, the base metal 10 whose parts are to be welded, and the welding arcs 12.

An altered method has also been proposed in which a single welding wire of conventional size and strong current is used in a single-layer, single-pass process. Here again, as shown in FIG. 2, a crack 11b may develop in the center of the weld bead, or an undercut may be formed in the groove wall, which in turn easily causes a stably bonded portion 11a, which is a significant defect. When using a V-groove to prevent undercuts and cracks, the increased width of the groove results in a corresponding increase in consumption uI

210844 of the material to be welded and the stress in the weld.

Submerged arc welding has also been widely used for the following main reasons. In contrast to arc welding of metal in an inert gas, in which an unshielded arc is used, the welding is carried out under the flux in a conventional groove and is therefore used for a wide range of groove contours. The overlapping portions of the weld beads 15 can be deposited with less precision than in arc welding of metal in an inert gas, but there are few defects such as undercutting and inadequate merging. Test welds were created with relatively high efficiency by automatic welding.

Considerations on measures to achieve high efficiency and high quality in butt welding of thick slabs have led to the following conclusions.

Multi-layer welding gives high-quality welds without any subsequent final processing compared to welds produced by single-layer welding, such as under-slag electrical welding using a large heat input.

The smaller the heat input to melt the groove walls in the amount of heat sufficient for perfect penetration, the better the quality of the resulting weld.

In terms of stress in the weld and edge treatment, a groove with parallel walls or an I-shaped groove is preferable to a V-shaped groove.

For welds with overlapping weld beads, a single-layer, three-pass welding process allows the easiest welding process and obtains the best welds. . Arc welding of metal in an inert gas does not require waste removal and allows multiple welding.

In view of the above, it is an object of the present invention to overcome the disadvantages of conventional arc welding of metal in inert gas, to provide a three-electrode welding method free of the disadvantages of conventional arc welding of metal in inert gas, and to provide a device for carrying out the method.

SUMMARY OF THE INVENTION The invention solves the problem by providing a three-electrode arc welding method of metal in an inert gas of I-shaped grooves in a planar position by placing the metal plate members to be welded at a distance to form a groove. The I-shaped first welding electrode, the second welding electrode and the third welding electrode are positioned adjacent to the I-shaped groove in such a position that the first electrode and the second electrode form the base of an isosceles triangle and the third electrode forms its apex. wherein the base of the isosceles triangle is perpendicular to the direction. welding and its peak is in the direction of welding,. a short-circuit arc is formed on the first electrode and on the second electrode, so that their arc welds in the desired position, a sputter arc is formed on the third electrode, and weld beads are deposited between the welding of the first and second electrodes, the first electrode and the second electrode a rounded weld, in which the weld beads leave spaces between the beads of the rounded weld, and then, these spaces are filled by sputter welding from the third electrode.

The invention further provides an apparatus for carrying out the method as defined above, characterized in that it has a welding cover in the cover. The torch has three welding wire contact tubes that extend through the insulating blanket at the apexes of an isosceles triangle, the second contact tube being straight while the first contact tube and the third contact tube are bent outwardly from the cover cup in opposite directions to each other, and each of the three contact tubes is electrically connected to one pole of the secondary winding of one of the three welding transformers, their other poles being connected together to the workpiece.

According to a preferred embodiment of the invention, copper tubes are provided in contact with the contact tubes for flow-water cooling of the contact tubes.

These measures of the invention achieve a new and higher technical effect in the following directions: Weld beads are formed independently of each other, but at the same time, and those formed by short-term welding of fine welding wires, do not require a large heat input so · Parts of base metal are poorly melted and heat-affected areas of base metals are delimited. For these features, the process according to the invention is advantageously used for standardized metals, for example high stress metals and for easily hardenable materials. In addition, weld beads and heat-bearing parent metal regions are formed under predetermined operating conditions, so that heat treatment for equalization or tempering can be performed by heating to an acceptable temperature. A further advantage of the welding method according to the invention is the possibility of welding hardenable materials without prior or subsequent heating. Yet another advantage of the invention in multi-layer welding of thick plates is that the parent metal composition to be welded can be subjected to final inspection as in conventional multilayer welding, and therefore the subsequent processing temperature can be equalized or stress relieved welding omitted or limited. Since the method according to the invention involves welding together

With 6 common I-shaped groove edges, edge preparation is not essential and the edges can also be cut by flame.

An embodiment of the invention is shown in the accompanying drawings, in which: FIGS. 1 and 2 show, in detail, how the welding is carried out in a conventional manner; FIG. 3 is a section along line III-III in FIG. Fig. 4 is a cross-sectional view of the weld shown in Fig. 3; Fig. 5 is a cross-section along the line V-V of Fig. 4; Fig. 6 is a longitudinal section through the weld according to the method; FIG. 6 and FIG. 8 show a hardness diagram of the weld as a function of the position coordinate measured perpendicular to the welding direction.

Giant. Figures 3, 4 and 5 show an apparatus for: three-arc arc welding of metal in an inert gas by the method of the invention. In the cover 2 of the welding torch 1 are arranged three contact tubes 4A, 4B, 40 _f which extend through the insulating plate 3 forming the spacer at the apexes of the isosceles triangle (Fig. 4). The second contact tube 4B is straight, while the first contact tube 4A and the third contact tube 40 are bent so that their welding wires are directed towards the walls of the groove to be welded. The contact tubes 4A, 4B, 4C are formed independently and adapted to the welding wires 5A, 5B, SO, which may or may not have the same diameters. The welding wires 5A, 5B, 50 are supplied with power from three independent transformers 6A, 6B, 60. In order to prevent overheating during welding, the contact tubes 4A, 4B, 40 are optionally cooled, for example by co-arranged copper tubes 7A, 7B, 70. in which water circulates. Welding wires 5A 5B, 50 and portions of the welded basic stored storage coils 8A, 8B, 80 by the feed mechanisms 14A, 14B, 14C. In the inert gas 9 supplied to the cover cup 2, welding arcs 12A, 12B, 12C are formed between the ends of the welding wires 5A, 5B, 50 and portions of the welded parent metal 10 or weld beads 11A, 10, 110 being just welded. Thus, the ends of the welding wires 5A, 5B, 50 are melted together with the contact edges of the two weld metal portions 10 and the previous weld bead 11A, 11B, 110 with the just welded layer and form new further weld beads.

According to the invention, the direction in which welding is to be carried out is chosen such that in the triangle defined by the centers A, V, C of the contact tubes 4A, 4B, 40 (FIG. 4), welding 16 may be perpendicular from peak V to base AC. The welding head 17 comprising the welding torch 1, the welding wire feeding mechanisms 14A, 14B, 140, etc. and a group of welding wire storage coils 8A, 8B, 80 on the one hand and both base metal portions 10 on the other hand to be welded are fixed separately on fixed, movable or movable bases (not shown), and welding is carried out by moving these bases or carts against each other at the speeds best suited to the corresponding welding needs.

Typically, butt welding uses metal arc welding machines in an inert gas of the kind called short-arc, where the transformers 6A, 6C, the feed mechanisms 14A, 14C of the welding wires 5A, 50 have the same functions. On the other hand, the welding transformer 6B and the welding wire feeding mechanism 14B form the so-called accessory for the atomized spray.

As noted above, the welding wires 5A, 5B, 5C extend through the apexes of an isosceles triangle. Although the essence of the invention is that the space between the fillet weld of the two previous welding wires 5A, 5C is filled with the weld produced by the next welding wire 5B, it is possible to use a stepped triangle without departing from the scope of the invention. Here, the welding wires 5A, 50 are fine that their diameter is about 1 mm, while the welding wire 5B is of conventional diameter and therefore thicker than the welding wires 5A, 50. Of course, thin wire welding 5A, 50 is followed by thick welding wire 5B. When welding thick plates by three-electrode arc welding of metal in an inert gas of the I-shaped groove according to the invention, the welding wires 5A, 50 are bent at their ends by the bent ends of the contact tubes 4A, 40 (Figs. 6 and 7) at an angle. that grips 45 ° with their original axis. In this way, round welding is performed to form the weld beads 15A, 15B at the corners defined by the groove walls and the weld beads 10A, 11B, 110 of the layer being welded. At the same time, the welding wire 5B passes through the contact tube 4B and the space between the rounded weld beads 15A, 150 is welded together. In this way, one layer is formed by three wire passes through which the bead 15A, 15B, 15C is formed in the shape groove

I. This process is known as single-layer three-pass welding.

In the welding process according to the invention, the weld beads 15A, 15B, 15C are formed independently of each other, although they are formed simultaneously. In particular, the weld beads 15A, 15C, which are formed by short-arc welding of fine welding wires 5A, 50, do not require a large heat input. Accordingly, the welded portions of the parent metal 10 are poorly melted and the heat-affected areas 18A, 180 of the parent metal 10 are limited. For these features, the method is preferably used for standardized metals, for example high stress metals and for easily hardenable materials. The weld bead 15B must not adversely affect the welded portions of the parent metal 10 even when a strong electric current is used to achieve increased welding performance, since the welding heat is conducted to the welded portions of the parent metal 10 by the weld beads 15A, 15C. In addition, the weld beads 15A, 15C in the region 18A, 18C of the base metal 10 on which the heat required to form these weld beads ISA, 15C are applied is generated under predetermined operating conditions so that heat treatment for alignment or tempering can be performed by heating to an acceptable temperature.

A further advantage of the method according to the invention is the possibility of welding hardenable materials without prior or subsequent heating. This is accomplished in that the weld beads 15A, 15C are formed by welding without preheating and are immediately followed by the weld beads 15B, thereby obtaining the effect of refining and subsequent heating, which again prevents the formation of haze cracks. The weld bead 15B is itself protected from the formation of cracks caused by turbidity as it is preheated by the weld bead 15A, 15C. Therefore, when using the process according to the invention, it is possible to weld hardenable materials without prior and subsequent heating, with a greater effect than is achieved by these processes.

Yet another advantage of the invention in multi-layer welding of thick plates according to the invention is that the parent metal composition to be welded can be subjected to final inspection as in conventional multilayer welding and therefore subsequent heat treatment such as alignment or stress relief after welding can be omitted. or limited. Weld beads 15A, 15C can be simply formed by round welding. While conventional narrow-groove welding can cause insufficient melting and thus fusion of the bead beads, the method of the invention makes it possible to produce welds only by round welding and, moreover, the welding arcs 12A, 12C are very stable. By forming the weld bead 15B, the bottom defined by the weld bead 15A, 15C is filled by spray arc welding. In other words, welding is carried out on a flat surface where it is easier to weld than in the corners and where sufficient preheating is performed. Since the arc environment that is ionized is better than for previous weld beads 15A, 15C, a steady arc and ideal penetration contours for exchange on the molten bottom are achieved. These passages are repeated layer by layer in the same way and the welding torch 1 can be placed on the base of the front groove. This allows an automatic procedure with increased efficiency.

Since the method according to the invention allows welding of the parallel edges of the I-shaped grooves together, the preparation of the edges by machining is not essential, since the edges can also be cut by flame. The weld beads 15A, 15B, 15C are formed from molten regions 13A, 13B, 13C that are independent of each other and have a wide range of locations to the molten metal deposited therein. Therefore, the weld on the groove surface is fully satisfactory, although this surface is rough due to the flame cutting of the seam. The stress caused by the weld is minimal because the I-shaped groove is continuously welded by a triple of Weld Bead 15A, 15V, 1SC, each of which is formed predominantly simultaneously by a single-layer three-pass process.

The three-electrode arc welding process of metal in inert gas according to the present invention is explained in detail in the following example.

Example

Three-electrode arc welding of metal in an inert gas was performed according to the method of the invention. Welded pieces were made of steel НТ-80 with a thickness of 75 mm and a width of 16 m. Argon containing 20% by volume oxygen was used as an inert gas. The electrodes were arranged in an isosceles triangle according to FIG. 4, as explained above. The welding wire diameters, currents and voltages are given in Table 1:

Table 1

Electrode Wire diameter mm Current (A) Voltage (V) AND 1,2 280 28 В 1.6 360 26 C 1,2 280 28

The welding speed was 700 mm. min ^-1 .

Fig. 8 shows a diagram of the hardness of the weld as a function of the position coordinate measured perpendicular to the welding direction. HAT indicates the zone affected by heat at the transition between the weld material and the welded pieces.

Claims (3)

SUBJECT OF THE INVENTION Method 1: Γίθ1θ + ίΓθ (1ον61ιο arc welding of metal in inert gas of I-shaped grooves on a butt in a plane position, characterized in that the metal plate members to be welded are spaced apart to form an I-shaped groove the first welding electrode, the second welding electrode and the third welding electrode are positioned adjacent to the I-shaped groove in such a position that the first electrode and the second electrode form the base of the isosceles triangle and the third electrode forms its apex, the base of the isosceles triangle is perpendicular welding and its peak is in the welding direction, a short-circuit arc is formed on the first electrode and on the second electrode, so that their arcs weld in the desired position, a sputter arc is formed on the third electrode and weld beads are deposited between the first and second electrodes the I-shaped groove walls by the first electrode and a second rounded weld electrode, wherein the weld beads leave spaces between the round weld beads, and then fill the spaces with sputter welding from the third electrode. Device for carrying out the method according to claim 1, characterized in that three contact tubes (4A, 4B, 4C) for welding wires (5A, 5B, 5C), which overlap the insulating tubes, are arranged in the welding torch cover (2). a plate (3) at the apexes of the isosceles triangle, the second contact tube (4Bj being straight), while the first contact tube (4A) and the third contact tube (4C) are outwardly from the cover cup (2) in opposite directions, and wherein each of the three contact tubes (4A, 4B, 4C1) is electrically connected to one pole of the secondary winding of one of the three welding transformers (6A, 6B, 6Cj), the other poles of which are jointly connected to the workpiece (10). Device according to claim 2, characterized in that it is in contact with the contact tubes. (4A, 4B, 4C) copper tubes (7A, 7B, 7CJ) are provided for flow water cooling of the touch tubes (4A, 4B, 4C).