RU2434725C1 - Method and device for contact butt welding with preheating of compact-section ring-shaped articles - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to device for contact butt welding with preheating of compact-section ring-shaped articles to be used at special-purpose butt-welding machines. Linear size of the billets outer semi-circle line is measured to calculate allowance for shortening, removal of overmeasure, flash-off and shrinkage allowances. Required part circumference and measured semi-circle size are entered into control system. Control system is used to compute initial jaws spacing and final distance between jaws with required allowance for shortening. First butt is welded. Actual shortening is compared with preset one. In case they differ, new initial jaws spacing for second butt is computed. Second butt is welded by first butt cycle.

EFFECT: higher precision of diameter and ambit.

1 dwg

Description

The present invention relates to welding production, and in particular to methods of flash butt welding with preheating of products of an annular closed profile of compact cross section, performed on specialized butt welding machines.

The use of welding billets in the form of rolled half rings to obtain closed products, such as wheel rims, bandages, etc., from various profiles of aluminum, magnesium and titanium alloys has great economic benefit, as it eliminates the costly operations of machining the billets. However, flash butt welding used in such cases by continuous flash welding requires strict execution and reproducibility of welding modes to obtain the accuracy of the welded parts in diameter, perimeter, ovality, flatness, etc.

Marriage in the manufacture of such products, especially large diameters, is practically unacceptable, since it leads to significant costs in cases where defective products cannot be fixed by rolling or cutting. The quality of the welds largely depends on the correct installation of the workpieces with the optimum departure of their ends from the jaws of the machine and the corresponding choice of the initial distance between the jaws, determined by the linear parameters of the welding mode:

Δ out = Δpr + Δop + Δos + Δk,

where Δ prip - lost wax stock;

- Δopl - allowance for reflow;

- Δos - allowance for draft;

- Δк - the final distance between the jaws after precipitation.

To facilitate the excitation of reflow and reduce the upsetting force when welding products of compact cross section, preheating is applied by passing a current from the welding transformer through the compressed ends of the parts. The stability of the resulting quality of the joints and the reproducibility of the welding modes largely depend on the accuracy of heating the ends of the workpieces.

Known welding machine K-393 and the method of welding bandages with a diameter of more than 1200 mm performed thereon (see, for example, N. S. Kabanov “Welding on Contact Machines” M .: Higher School, 1979, p. 99) using an additional band of brace covering the entire circumference of the weld ring, which allows you to weld finishing profiles with high geometric accuracy (0.5-1 mm) around the perimeter and ovality.

However, such machines and technology are suitable for mass production of the same type of parts, and when changing the nomenclature of parts, a complex restructuring of the machine with the change of an additional bandage is required.

The closest to the proposed invention in terms of technical nature and the achieved result is a method for controlling the process of flash butt welding by reflow (see SU 1606282 A1, IPC V23K 11/04, 11/15/90), in which the program for moving the movable clamp is set and its position is monitored the movement and after the occurrence of the fusion current and compare the instant of occurrence of the fusion current with the moments of passage of the movable clamp distances equal to the minimum and maximum allowable values of the gap between the ends of the strips.

The disadvantage of this method is that it only allows you to control the size of the gap between the ends and reject joints, but does not allow you to adjust the welding mode during reflow, depending on the size of the gap or other settings affecting the quality. In addition, during contact heating of the compressed ends of the compact section products, they are crushed and the change in the length of the ends of the ends from the jaws, which should also be controlled before reflowing, is associated with this.

The technical result of the invention is to improve the quality of the weld, increase the productivity of the machine and simplify its maintenance, increase the accuracy of tuning the optimal parameters of the welding mode and limit the influence of the subjective factor when setting up welding machines, obtaining finished products with increased accuracy in diameter and perimeter in a minimum tolerance field .

The technical result is ensured by the fact that when using the flash butt welding method with preheating of products of an annular closed profile with a compact section, including measuring the linear size along the outer circumference of the half rings, installing and clamping them in the jaws of a fixed and moving frame of the welding machine, closing the ends of the welded half rings and contact heating from the welding transformer, measuring the movement of the movable bed, monitoring the temperature of the preheating and welding current, times mating the ends after heating and switching to continuous reflow, and making precipitation at the end of reflow, before installing the half rings for welding, introduce the required circumference of the ring product and the measured linear dimension along the outer circumference of the half rings into the control system, while the control system calculates the initial distance between the jaws taking into account half of the lost wax allowance, allowances for flashing and draft of workpieces, the final distance between the jaws after upsetting, and gives a signal to move the slide of the working bed to the distance of the calculated initial distance, then set the half rings for welding with the placement of their ends between the jaws of the movable and fixed bed, clamp the jaws, compress the ends of the workpieces with a movable bed and turn on the welding transformer for heating, after reaching the ends of the required temperature according to the temperature sensor, turn off welding transformer, and the movable bed is withdrawn until a gap between the ends is formed, then the welding transformer and moving the movable bed forward are turned on e and begin to count the path of the movable bed at the moment of the appearance of the melting current, melt the ends of the half rings at a constant speed, and after reaching the required calculated shortening of the half rings, they switch to the melting at an increasing speed and at the end of the melting produce sludge, then after determining the actual shortening of the half rings by the control system, compare it with the given and in case of deviation of the actual shortening from the given, calculate a new value of the initial distance for the second joint, unclench the lips and take moving the bed to the calculated initial distance, feed the second joint of the half rings to the lips of the welding machine, install it in the lips in the middle of the original distance, clamp the lips and weld the second joint according to the first joint algorithm.

The machine on which the proposed method is carried out must be equipped with a high-precision sensor that records the actual position of the movable bed during its movement, a meter for the length of the half-rings, a temperature sensor for the ends of the half-rings, a welding current sensor and a control system that allows the bed to be stopped in predetermined positions according to the readings of the said sensor and perceiving the readings of a length meter of welded half rings and temperature and welding current sensors. Such control of the machine is implemented on microprocessor technology and provides the program algorithm of the machine mechanisms in the program, both when installing workpieces in the jaws of the machine, and while ensuring the melting of stock blanks, allowances for flashing and draft, while the entire control program package is stored in the memory of the control system welding modes with the selection of optimal values of allowances for flashing and draft, the final distance between the jaws after upsetting, depending on the cross section of the workpieces, which then smelting allowance is added taking into account the length of the workpieces. A linear displacement sensor associated with a movable and fixed bed records the actual position of the movable bed and sends the appropriate signals to the machine control system to stop the bed at predetermined points. The temperature sensor monitors the heating temperature and gives a signal to the control system to turn off the transformer and remove the bed. The heating current sensor detects the absence of current during the formation of a gap and its presence during reflow and sediment.

The inventive method of flash butt welding with preheating of products of an annular closed profile of compact cross section is illustrated in figure 1, which shows a diagram of the welding of the first joint of the half rings.

A flash butt welding machine for performing the proposed method of flash butt welding with preheating of products of an annular closed profile of compact section contains a fixed bed with clamping jaws 1 and a movable bed with clamping jaws 2, in which workpieces 3 and 4 are mounted and fixed in the form of half rings before welding.

The inventive method of flash butt welding with preheating products of an annular closed profile of compact cross section is as follows:

- before welding a batch of half rings into the control system, set the required size Lrebar shells with circumferential tolerances;

- before installing workpieces 3 and 4 under welding by a length sensor, measure their linear circumference Liz, which then enters the control system;

- having accepted the initial and measured data, the control system calculates the excess total allowance (Lout-Lreq) of workpieces 3 and 4 and taking into account the specified allowances for fusion Δpl and draft Δos determines the amount of smelted allowance Δpr1 at the first joint as

Δpr1 = ½ (Lmesh-Lreq) -Δpl-Δoc,

and then the value of the initial distance Δex1 (5) between the jaws for the first joint as

Δex1 = Δpr1 + Δopl + Δoc + Δk,

- after the removal of the movable clamp 4 by the value of the initial distance 5 (Fig. 1, a), installation operations for welding and clamping of workpieces 3 and 4 in clamps 1 and 2 (Fig. 1, b) are performed.

Then:

- compress the ends of the workpieces 3 and 4 with a movable bed and turn on the welding transformer for heating (Fig. 1, c);

- after reaching the ends of the required temperature at the command of the temperature sensor, turn off the welding transformer, and move the movable bed until a gap 6 is formed between the ends of the workpieces 3 and 4 (Fig. 1, d);

- turn on the welding transformer, then move the movable bed forward at a constant speed, and when the fusion current appears at point 0, the counting of the allowances for smelting Δpr1 (7) (Fig. 1, e), the fusion Δpl (8) (Fig. 1, e ) and precipitate Δос (9) (Fig. 1, g) of workpieces 3 and 4;

wherein:

- after achieving the required shortening of the workpieces 3 and 4 in the melting section 7 include reflow with a constantly increasing speed in the plot 8;

- at the end of the reflow in section 8 by the position sensor of the movable bed include sediment and upset workpieces by a value of 9;

- at the end of the upsetting process, the actual final distance Δk.fact (10) (Fig. 1, h) is determined by the position sensor of the movable bed and the deviation of the actual shortening of the workpieces 3 and 4 from the given Δk (11) welded by the first joint 12 is calculated from it, as Δ = (Δk-Δk.fact);

- the control system compares the obtained actual size of the workpieces 3 and 4 with a given ring size (Liz ± Δ-Lreb), calculates the allowance for smelting Δpr2 to obtain the ring of the required size:

Δprip2 = ½ (Lizm-Lreq) ± Δ-Δpl-Δos

and determines the initial distance Δex2 when welding the second joint, taking into account the calculated lost wax allowance Δpr2, the allowances for the fusion Δpl and draft Δos, as well as the actual final distance Δk.Fac obtained at the first joint, as

Δex2 = Δprp2 + Δopl + Δos + Δk.fact

- to weld the second joint of the half rings, unclench jaws 1 and 2, after retracting the movable bed by the value of the calculated initial distance Δxx2, the second joint of the half rings to jaws 1 and 2 of the welding machine is fed, set it in the middle and clamped with jaws 1 and 2;

- after this, the joint is welded according to the algorithm of the first joint.

Thus, the proposed method and device for flash butt welding with preheating of products of an annular closed profile of compact section allows you to:

- to improve the quality of the weld due to the accuracy of setting the optimal parameters of the welding mode and limiting the influence of the subjective factor when setting up welding machines;

- increase the productivity of the machine by eliminating re-measurement of the workpieces after welding the first joint;

- solve the problem of obtaining finished products with increased accuracy in diameter and perimeter.

Its most effective use is on butt welding machines, which are designed for welding products of a closed profile of a wide range of different sections.

Claims (1)

The method of flash butt welding with preheating of products of an annular closed profile of compact cross section, in which the linear size is measured along the outer circumference of the welded workpieces in the form of half rings, an allowance for shortening the workpieces is set taking into account the removal of excess allowance, melting allowances and draft, and introduced into the control system the welding machine the required size of the circumference of the product of an annular closed profile and the measured linear size along the outer circumference of the semi-finished blanks c, using the said control system, the initial distance between the jaws of the movable and fixed beds of the welding machine and the final distance between the jaws after upsetting during welding of the first joint, taking into account half the specified allowance for shortening the workpieces, are calculated and the movable bed of the welding machine is moved by the value of the calculated initial distance between sponges, then set the half rings for welding with the placement of their ends between the sponges, clamp the jaws, compress the ends of the workpieces using a movable bed and carry out a welding cycle of the first joint, in accordance with which the welding transformer is turned on to heat the workpieces, after reaching the required temperature at the ends, the welding transformer is turned off by the command of the temperature sensor, the movable bed is taken to form a gap between the ends, then the welding transformer is turned on and the movable bed is moved forward, and at the moment of the appearance of the fusion current, the counting of the path of the movable bed begins, at the same time the ends of the half rings are melted at a constant speed, and after reaching After a specified removal by melting of excess stock of stocks, they switch to reflow at an increasing speed and at the end of reflowing they precipitate at the end of the welding cycle of the first joint, then, taking into account the end position of the movable bed, the actual workpiece shortening is determined using the mentioned control system, compared with the specified stock and a new one is calculated. the value of the initial distance between the jaws for welding the second joint, taking into account the deviation of the actual shortening from the set, unclench the jaws and retract zhnuyu a frame to a new value computed initial distance therebetween, the second joint half rings mounted in the jaws of the welding machine in the middle of said distance between them is clamped and sealed sponge second joint of the first joint of the cycle.