SU1318365A1 - Method of high-frequency welding of bunches of ribbed tubes - Google Patents

Abstract

The invention relates to the field of welding, namely to the production of finned tubes by high-frequency welding, and can be used in power engineering for the manufacture of membrane heating surfaces from finned tubes. The aim of the invention is to improve the quality of welding and dimensional accuracy. To this end, the process of forming each welded joint of a pipe with an edge begins at the programmed portion of the incomplete weld. The amount of advance is chosen corresponding to the duration of the current increase in the welding circuit and end the welding process earlier relative to the length of the rib ahead. The process of formation of a welded joint is conducted with a twofold successive application of upsetting force. The first force is applied in front of the top of the angle of convergence of the strip with the pipe with a decrease in the angle of convergence against the previously selected one. The amount of re-precipitation is calculated from the conditions of forging the weld metal. 1 hp f-ly, 2 ill., 1 tab. § (L 00 00 00 Od ate

Description

The invention relates to welding, in particular to the production of finned tubes by high-frequency welding, and can be used in power engineering for the manufacture of membrane heating surfaces from finned tubes.

The purpose of the invention is to improve the quality of welding and the accuracy of geometric dimensions.

Fig. 1 shows a process program for expanding the length of the rib and the step between them (a) and current modulation in the welding circuit and the location of the seam on the product according to the proposed method of manufacturing ribbed lashes (b); figure 2 - scheme of the process of radiofrequency welding of finned tubes according to the proposed method.

In figure 1 and 2 marked: 1 - the length of the ribs; 1 - step length between the ribs; t is the travel time at the speed V of the edge specified

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length 1 through the welding circuit;

t, advancing the onset of current buildup in the welding circuit relative to the first, initial edge of the rib; t is the advance of switching off or reducing the current in the welding circuit relative to the last, final end of the rib;

(3) the preselected angle of convergence of the strip with the pipe; d is the angle of convergence of the strip with the pipe after application of the first upsetting force; Q, is the first upsetting effort; p2 reaction force in the support mechanism of effort; Q - re-upset force; Q - effort reaction from effort; A is the vertex of the convergence angle of the strip about the pipe; L is the distance from the top of the convergence angle A to the point of application of force; L is the temperature range of the effective application of re-settlement; B - welding current passage lines; B - lines of possible shunting of the welding current; L is the distance from the top of the angle of convergence to the point of primary release of molten metal with oxides.

When pipes are finned by high-frequency welding for a given system design: power source — welding circuit — product, an optimum amount of advance of current rise and fall relative to the initial and final edges of the rib ends during welding is ensured.

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the weld seam and the specified length of the welded ribs with the subsequent removal of the undercooked sections, and welding

5 in such a way that the workpieces being welded (pipe 1 and strip 2, figure 2) are continuously fed to the welding zone with the angle of the strip with the pipe at point A using the strip orientation mechanism 3. To heat the surfaces to be welded from the RF source 4, the welding current is applied to the pipe 1 through the contact 5, and through the active concentrator 6 and the contact 7

15 current is applied to strip 2. Calculate the moment of resistance of the cross section of strip 2 in the welding plane and, depending on the moment of resistance, choose the angle / e on the basis of

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20 research institutes listed in the table, established experimentally for the size of the bands used in power engineering.

According to the formula L W / j, where W (cm) is the moment of resistance of the strip section; - preliminary angle of convergence of the strip with the pipe, determine L (cm) - the distance from the top A of the angle of convergence of the rib to the pipe to the point where the precipitate Q is applied. The first mechanism 8 for creating the precipitation force is moved to the distance L from the top A and the points of direction of the reaction force Qj in the support mechanism 9.

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Depending on the welding speed, the angle oi, and the mode parameters, the zone L. is set. - the distance from the top of the angle d of the rib's descent from the pipe to the point 10 of the primary choice of the molten metal, i.e. zone where

The re-oxidation of the melted edges is insignificant and is within the range that ensures a high-quality weld, which is feasible provided that the heating time does not exceed 0.02 s.

In this case, the primary ejection point of the molten metal is within the zone L., and, the closer to the top A, the quality welded connection of the molten metal in the process of re-melting of the edges. But since the position of the primary ejection point of the melted metal is related to the dependence with the convergence angle and the elastic properties of the elements being welded, adjusting the angle c and stabilizing it by re-bending the strip when creating the force Q with the displacement of its application point relative to the vertex of the convergence angle A the process of welding with monotonous regularity of heating the edges of the primary melted metal emission together with oxides at a certain stable distribution from the top of the convergence angle and with the reduction the zone of re-melting of the edges to a size that excludes the formation of re-oxidation of the liquid phase of the weld metal with the formation of a hard to break down oxide film during the precipitation process. By reducing the angle of convergence d against a predetermined angle / s, a temperature jump in chrome heating is achieved due to their sharp approach, which at high current density leads to a rapid overheating of the edges in this zone with the formation of metal vapors, the pressure of which instantly increases and leads to the release of molten metal together with the oxides at point 10, located in the immediate vicinity of the point of application of the upsetting force Q.

Next, using the CCM (control computer), calculate

the re-precipitation value Qj from the condition of removal of the weld metal from the load transferred by the rib, taking into account the yield strength of the metal at a given temperature and plastic bending of the rib on the length, and applying an upsetting force Q, mechanism 11 along the axis of the support mechanism 12. This support achieves partial recrystallization of the metal suture with raising it

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physicomechanical properties and size adjustment of the finned tube. The offset of the point of application of upsetting force Q relative to the reaction force Q. eliminates the possibility of shunting welding current directly through the clamping elements, and shunting through the product in section L coincides with the direction of the working current and therefore for stability The process has no effect.

During the manufacture of finned tubes or pins, the location on the product of the points on which the welding current begins to rise before the welding mode is reached and the reduction in the welding current at the exit from the mode with the position on the product of the beginning of the application of the upsetting force Q on the element to be welded and the termination the effects of this effort are measured in a continuous process of manufacturing products, the linear dimensions between the indicated points with the conversion of the measurement results into the signal которыеe which are entered into the UVM to coordinate the lead subsequent technological process (straightening, machining and cutting of ribs) at specified pipe sections. This makes it possible to increase the processing accuracy of the products in the indicated operations and to automate the process of their manufacture with

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rmula of invention

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1. The method of high-frequency welding of pipe lashes with ribs, in which active concentration of current is used in the welding zone, the formation of a welded joint is carried out with a double-sided application of upsetting force, a programmer of the welds and is not penetrated, so that quality of welding and accuracy of geometrical dimensions; the process of formation of a welded joint of a pipe with an edge begins at the programmed portion of the incomplete weld; choose the magnitude of this advance, corresponding to The duration of the current increase in the welding circuit from the minimum to the maximum steady-state value and time of its passage, which ensures the heating of the welded parts to the welding temperature, finishes the welding process earlier than the edge with the lead, the value of which is set to no more than half of the current cycle in the circuit from maximum value, the first upsetting force is applied with a decrease in convergence angle Ъ relative to the initial one at a distance from the top of the convergence angle of the edge with pipe equal to

L w

where W is the moment of resistance of the rib cross section in the welding plane, {b is the pre-selected angle of convergence of the strip with the pipe, the re-draft is calculated from the condition of forging the weld metal and applied beyond the top of the angle of convergence of the rib with the pipe in the temperature range from solid state to a temperature not lower than 100 .. .200 C temperature of solidification of the liquid phase.

2. Method POP.1, which differs from the fact that the position of the points of application of the first upsetting force and the termination of this effect is coordinated with

About the location of the start points of welding current increase at the exit to the welding mode and the end of the welding current decrease at the exit from the mode, the linear dimensions between the specified points are measured in a continuous process from 5 to convert the measurement results into signals that are entered into the subsequent process control system .

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Editor N. Bobkova

Compiled by E. Vetrova Tehred V. Kadar

Order 2458/10 Circulation 975.Subscription

VNISH1I USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

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Proofreader V. But ha

Claims (2)

Claim 1. A method of high-frequency welding of pipe lashes with ribs, in which active concentration of current is used in the welding zone, the formation of a welded joint is carried out from a double edge, the pressure of which instantly increases and leads to the ejection of molten metal together with oxides at point 10 located at 45 proximity to the point of application of the draft force Q _n . Next, using UVM (control computer), the re-upsetting quantity Q _{3 is} calculated from the condition that the weld metal is removed from the load transmitted by the rib, taking into account the yield strength of the metal at a given temperature and the plastic bending of the rib along the length, and 55 are applied by upsetting Q, mechanism 11 along the reference axis mechanism 12. With this principle, partial recrystallization of the weld metal is achieved with an increase in its consistent sequential application of upsetting force, programming the length of the welds and un-welded sections, excellent The fact is that, in order to improve the quality of welding and the accuracy of geometric dimensions, the process of forming a welded joint of a pipe with a rib 50 start at the programmed section of lack of fusion, choosing the value of this lead corresponding to the duration of the current rise in the welding circuit from minimum to maximum steady-state value 'and its passage time, ensuring heating of the parts to be welded to the welding temperature, finish the welding process earlier relative to the length of the rib ahead of, the value of which is set to no more than half the cycle of current decline in the circuit from the maximum value, the first force of the precipitation is applied with a decrease in the angle of convergence Relative to the original at a distance from the top of the angle of convergence of the ribs with the pipe, equal to 10 L = W / J, where W is the moment of resistance of the rib section in the welding plane, ft, is the preselected angle of convergence of 15 strips with the pipe, the re-precipitation value is calculated from the condition of forging the weld metal and applied beyond the vertex of the angle of convergence of the rib with the pipe in the interval temperatures from a solid-liquid state to a temperature not lower than 100 ... 200 ° C of the solidification temperature of the liquid phase. 2. The method of Pop. 1, characterized in that the position of the points of application of the first draft force and the termination of this force is consistent with the location of the points of the beginning of the increase in welding current when entering the welding mode and the end of the decrease in welding current when leaving the mode , in a continuous manufacturing process, measure linear dimensions between these points with the conversion of the measurement results into signals that are input into the control system of the subsequent process. Figure 1 FIG. 2