SU1637973A1 - Method for flash butt welding of hollow members with article - Google Patents

Abstract

This invention relates to flash butt welding technology and can be used for welding hollow or tubular parts with monolithic ones. The purpose of the invention is the expansion of technological capabilities by increasing the range of welded products and improving the quality of welding. The method of fusion welding of hollow elements with a product includes preheating the product with an electrode, melting the end of the welded element and the welded area of the product with an arc of low pressure and subsequent draft. The electrode is tubular, and a hollow element is placed inside it. The preheating and melting of the product and the end of the hollow element are pulsed with a constant current. After preheating, the end face of the hollow element and product is reflowed with an alternating current arc. In this case, phase control of the arc in each half-period is carried out. The method allows to expand the ratio of the thicknesses of the parts to be welded and the areas of their ends, and the quality of welding due to more uniform heating, as well as to weld parts from dissimilar materials. 4 il.

Description

The invention relates to flash butt welding and can be used for welding hollow or tubular parts with monolithic parts in various industries.

The purpose of the invention is the expansion of technological capabilities by increasing the range of welded products and improving the quality of welding.

Figure 1 presents the scheme of butt welding by melting; figure 2 - the dependence of the amplitude values of the welding current lo during the time t in the first stage; in fig. 3 - the same, in the second stage; 4 is the same at the stage of phase adjustment of the welding current.

The method is carried out as follows.

Butt flash welding is carried out in an inert gas medium, for example, argon at a pressure of 6-8 mm Hg. Weldable hollow (tubular) element 1, product 2 and electrode 3 are connected to a specialized source of welding current 4 through diode 5 and thyristors b and 7 connected to phase regulator 8.

Initially, a glowing discharge is excited in the welding zone, ensuring the existence in the gap between the end face of the hollow element 1, an additional electrode 3 and the wall of the plasma product 2, which stabilizes the excitation and burning of the welding arc. Then, the end of the element and the wall of the product are preheated in two stages. First, DC arc pulses are hot between product 2 and additional electrode 3 — cathode cleaning and heating of the product wall is performed (Fig. 2). Then the contactor 9 breaks the circuit between the diode 5 and the additional electrode 3 and DC arc pulses between the end of the hollow element and the wall of the product with phase current regulation (Fig. 3) are applied, which results in cathodic cleaning and heating of the end of the hollow element. After the differential heating of the ends of the parts to be welded is performed, they are melted by an alternating current arc with phase regulation (Fig.4), performed by means of phase regulator 8 and thyristors 6 and 7. At the time of appearance of a hollow element on the surfaces being welded to the layer of liquid metal . Screens 10–13 are available to protect the external surfaces of the parts from the effects of an electric arc.

This process is explained as follows.

To ensure the same thermal state of the welded hollow and monolithic parts, i.e. the occurrence of a layer of molten metal at the ends of the parts before the draft, immediately prior to reflow, differentiated their heating, which is carried out by a direct current arc in two stages.

In view of the fact that the heated mass of the wall is significantly greater than the mass of the end of the hollow element, in the first stage, the wall of the product is heated by pulses of a direct current arc burning between the product and the electrode, and the minus should be on the product, while performing cathode cleaning surface of the product.

The criterion for heating the wall of the product and transition to the second stage of heating is the beginning of the melting of the wall of the product, which, for example, for the AMgb material, corresponds to the melting point of Tpl 630 ° C,

In the second stage, the end of the hollow element is preheated to the temperature at which it begins to melt due to the burning of a pulsed direct current arc between the end of the hollow element and the wall of the product, and the minus should be on the element to conduct cathode cleaning of the end of the hollow element. the thermal state obtained in the 1st heating stage is maintained.

After the end of the second stage of heating between the end of the hollow element and

the wall of the product is ignited by an arc of low pressure alternating current and simultaneously melt the wall of the product and the end of the hollow element with subsequent sedimentation.

In order to obtain a uniform thin layer of molten metal, both on the end of the hollow element and on the wall of the product, the combustion mode 0 of the arc of each half-period is corrected due to phase adjustment.

Phase adjustment is carried out by a control circuit by varying the switching angle of the thyristor switches on the positive and negative half cycles of the AC arc.

In the arc column, more heat is generated at the anode than at the cathode; therefore, for uniform heating to the melting temperature 0 of a thin-walled element and a more massive product, the current in each half-period of the arc is controlled. When the anode is a welded element, i.e. plus a welding source on the element, heating element 5 is reduced, reducing the amount of current by increasing the switching angle of the thyristors. In the half-period, when the minus of the welding source on the element being welded, the thyristors switching angle is reduced. 0 PRI me R 1. When welding a pipe with a diameter of 216 mm and a wall thickness of 1.5 mm from AMGB material from AMGB aluminum alloy 8 mm thick, use the following welding mode. 5 Argon pressure in

chamber, mm Hg. 6-8

The heating current of the wall of the product (stage I), A200

Duration of heating, s0.8

0 Number of heating pulses of the first stage before the occurrence of a layer of molten metal8 Heating of the end of the pipe-5 pipe (2-stage), А100 Duration of heating, with 0.8 Number of heating pulses of the second stage before the appearance of the layer of molten metal at the end

pipeline5

Current of the product wall melting and the end of the pipeline with an alternating current arc, А340

5 Duration of the flashing current, c0.2 Draft value, mm1-1.5 Example 2. When welding pipelines with a diameter of 16 mm and a wall thickness of 1 mm from stainless steel to the product

AMg-B aluminum alloy 8 mm thick welding mode is as follows.

Argon pressure, mm Hg 6-8 Glow Current, A0,2

Heating current between the electrode and the wall of the product, A130

Heating current between steel piping and product wall, A60 Cycle duration, s 0.8 Number of heating cycles 8 Welding current between steel piping and product wall, A 220 Melting duration, s 0.2 Draft size, mm1-1.5 Quality of joints in both cases, good, missing pairs, untested areas.

The method allows to expand the ratio of the thickness of the parts to be welded and the ratio of areas and the ratio of the areas of their ends 3-20 times, to improve the quality of welding due to the achievement of uniform heating of the welded surfaces, as well as to weld products from dissimilar metals and alloys, for example, parts from AMgb and from 12x18H10T.

Claims (1)

Invention Formula The method of butt fusion welding of hollow elements with the product, including preheating the product with an electrode, flashing the end of the welded hollow element and the welded area of the product with an arc of low pressure and subsequent draft, characterized in that expansion of technological capabilities by increasing the range of products to be welded and improving the quality of welding, the electrode is tubular, inside the electrode, aligned with it the welded hollow element, and the preheating of the product and the end of the hollow element are conducted by a direct current arc in two stages: initially by impulses of an arc burning between the product and the electrode, before starting the surface of the product, then pulses of the arc burning between the product and the hollow element to be welded, before the butt end of the welded element begins to melt, after the preheating, the end of the hollow element and the product are alternated by alternating current arc arc and each half period. 1 FIG. g FIG. five