RU1760702C - Method of argon arc welding by an unmelting electrode - Google Patents

Abstract

FIELD: any branch of industry. SUBSTANCE: in process of argon arc welding by unmelting electrode additional stream 6 of protecting gas is carried into inner space 7 of a ring connection with the stream speed changing along cross section of the space. Gas stream speed of the areas, that are close to the welding seam, 2 -3 times exceeds speeds of the gas streams in the middle part of the space. EFFECT: method ensures good saving effect.

Description

 The invention relates to methods for arc welding with a non-consumable electrode in protective gases and can be used in all sectors of the national economy.

 As you know, when welding butt joints of critical structures from stainless steels, non-ferrous, titanium and other easily oxidizable alloys, good protection is required on the back of the weld. There are a number of techniques for this purpose.

 There is a method of arc welding, when a lining with a groove is placed on the back of the seam, into which protective gas is supplied, and thus the seam is protected.

 The disadvantage of this method is the possibility of creating excess pressure in the trough and squeezing a liquid bath with the formation of a meniscus or splashing it.

 There is a known method of arc welding, in which protective gas is supplied into the internal cavity of the joint, creating a chamber in the joint zone and protecting the seam.

 The disadvantage of this method is similar to the previous one.

 A known method of arc welding of ring joints, in which the back side of the seam is blown with an additional stream of protective gas and provide protection.

 This method is taken as a prototype as the closest in technical essence.

 The disadvantages of the method include the need for synchronous movement of the device for blowing with a welding torch and the supply of such a flow of protective gas, which, regardless of the distance to the surface of the bath, would ensure its protection. In addition, an increased flow rate can cause the bath to extrude or splash out, and a lower flow rate can result in poor weld protection.

 The aim of the invention is to improve the quality of the welded joint.

 This goal is achieved by the fact that in the method of argon-arc welding of non-consumable electrode of ring joints, in which an additional flow of protective gas is supplied to the internal cavity of the connection, the additional flow of protective gas is supplied with a varying speed over the cavity cross section, while the gas flow rate in the areas adjacent to the weld , more than 2-3 times the speed of the gas stream in the middle part of the cavity, its height h is (0.2-0.3) of the diameter of the stream, and the length l = (5-7) h. When welding joints of small diameter, an additional stream of protective gas is supplied in at least two sections of the inner cavity of the joint along its length.

 When conducting a patent search on this application, technical solutions were discovered, the implementation of which provides protection for the reverse side of the weld.

 However, these solutions do not allow the guaranteed protection of the weld without force acting on the molten metal and without unproductive consumption of protective gas.

 The proposed method of argon-arc welding with a non-consumable electrode due to the organization of an additional protective gas flow with a varying speed over the cross section of the joint cavity allows you to create the necessary protection for the root of the weld without unproductive increase in the consumption of protective gas, since the main gas flow enters the areas adjacent to the weld and is practically absent in the middle part of the cavity.

 The proposed dimensions of the gas flow and the ratio of velocities make it possible to exclude the force pressure on the molten weld metal, and also eliminate the “sagging” of the flow due to the mid-pressure created by it. This creates the conditions for uniform formation of the seam from the side of the connection root.

 In FIG. 1-3 show schemes for the protection of the seam on the reverse side.

When the arc 1 is burned from a non-consumable electrode 2, the ring connection 3 is melted to form a bath 4. To protect the bath 4, argon 5 is supplied from the side of the arc 1 and an additional protective gas stream 6 to the internal cavity 7 of compound 3 (Fig. 1). In this case, the additional stream 6 is supplied with a varying speed V _n over the cross section of the cavity 7, which consists of the velocity V _{per of the} peripheral gas stream 6 in the areas adjacent to the bath 4 and the speed V _{vn of the} internal gas stream located in the center of the cavity 7 (Fig. 1). The speed V _{per is} greater than the speed V _{vn by} 2–3 times.

The ratio between the flow rates V _per / V _ext = 2-3 is due to the provision of good protection of the reverse side of the seam.

With a ratio of V _per / V _vn <2, the flow is unstable, its turbulent motion is possible, which impairs protection. When V _per / V _ext > 3 near the surface of the bath 4, a vacuum may occur due to high-speed flow around it, which can lead to its "suction" inside the cavity (Fig. 1).

The height h of the peripheral gas stream is (0.2-0.3) of the diameter d _{zp of the} protective gas stream 6 supplied to the cavity 7, and its length l _zp = (5-7) h. If h <0.2d _zp , flow disruption is possible, and when h> 0.3d _zp , excessive gas flow is _possible .

A similar explanation is valid for _lnn <5h and _lnn > 7h.

 In FIG. 2 shows a multi-stage protection circuit for the reverse side of the seam. This scheme is most rational for ring connections 3 of small diameter (<25 mm). In this case, organizing the gas stream 6 sequentially along the length of the inner cavity 7, namely, creating sections 8 and 9, they achieve the best displacement from the air cavity and thereby improve the protection of the seam.

 In FIG. 3 shows a diagram for large diameters (> 25 mm). In this case, the flow 6 is organized directly near the annular connection 3 using the device 10. Such a scheme provides good protection of the seam with significant savings of protective gas.

 These flow rate profiles 6 are created using blowing devices 11 in which porous material with different densities along the cross section of the pipe cavity 7 is used, as a result of which it exhibits different resistance to flow 6.

The high speed V _{lane of the} stream 6 near the welding zone contributes to an increase in the pressure of the stream 6 on a part of the weld pool 4 if it enters the internal cavity 7 of the pipe being welded. In this case, the liquid metal of the bath 5 flows in the direction from the pipe and the formation of excessive reinforcement inside the pipe does not occur. Thus, a minimum and uniform reinforcement of the weld inside the pipe is achieved with a smooth transition between the pipes to be welded, which has a positive effect in the operation of critical pipelines.

The presence in the central part of the cavity 7 of the pipe of a low-speed flow 6 with a speed of V _int allows the “back-up” of the high-speed flow with a speed of V _per to the walls of the pipe due to the higher static pressure in the flow with a speed of V _int and thereby ensures quality protection of the weld from the inside of the pipe .

 An example implementation of the method.

 The method was carried out in automatic argon-arc welding of pipe joints of stainless steels as applied to the installation of gas pipelines in "clean rooms" (for the production of electronic engineering products). Welding was carried out on an automatic machine such as ODA. TIR-300DM1 was used as a power source, and ER-240 was used as control equipment. Pipes were welded from steel 12X18H10T of the following sizes: O 6x1; About 8x1; About 25x2; About 32x2. To facilitate the protection of the reverse side of the seam, specially designed devices were used. Welding was carried out in the modes indicated in the table.

The speed V _ext was 3 m / h, and the speed V _per - 9 m / h. The flow height for pipes ⌀ 6-8 mm was 2 mm, and for pipes ⌀ 25-32 mm - 4-5 mm. The flow length was 10 and 25 mm, respectively.

 The method allowed to provide protection of the seam inside the cavity of the "silver" color in all cases without force on the bath.

 (56) 1. USSR Copyright Certificate N 29844, cl. B 23 K 9/16, 1969.

 2. Copyright certificate of the USSR N 29844, cl. B 23 K 9/16, 1969.

 3. Copyright certificate of the USSR N 29844, cl. B 23 K 9/16, 1969.

Claims (2)

 1. METHOD FOR ARGON-ARC WELDING NON-MALTABLE ELECTRODE of ring joints, in which an additional protective gas stream is fed into the internal cavity of the connection, characterized in that, in order to improve the quality of the welded joint, an additional protective gas stream is supplied with a varying velocity along the cavity cross section, at the same time gas in areas adjacent to the seam, more than 2 to 3 times the speed of the gas stream in the middle part of the cavity, the height is from 0.2 to 0.3 of the diameter of the stream, and the length is from 5 to 7 heights.  2. The method according to p. 1, characterized in that when welding ring joints with a diameter of less than 25 mm, an additional gas stream is supplied in at least two sections of the inner cavity of the joint along its length.

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