CS205016B2 - Method of welding the cylindrical objects of the circular diameter and device for performing the same - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to a method of welding circular cylindrical objects by circumferential welding and to an apparatus for performing the method.

Due to their unusual weight and dimensions, nuclear reactor core vessels present complex welding problems that are not encountered in other manufacturing operations. Core vessels in pressurized-water nuclear reactors carry the reactor interior and core components and are supported by an upper flange at the inner edge of the uppermost part of the reactor pressure vessel. Generally, the reactor core consists of four individual components, an upper annular flange, an upper cylindrical vessel, a lower cylindrical vessel, and a lower support plate that are welded together. The assembly comprising the upper flange and the upper and lower cylindrical vessels forms a cylindrical piece, one end of which is closed by the lower support plate. The approximate height of the whole system is about 9 meters and the inside diameter is about 3.5 meters. The thickness of the lower and upper cylindrical parts is slightly over 5 cm. Although the bottom support plate occupies just over 50 cm of the overall height of the system, it contributes 27 t to a total weight of approximately 73 t by its weight.

The two circumferential weld joints that connect the lower support plate to the lower cylindrical portion and the lower and upper cylindrical portion are very important and must be of high quality so that the cylindrical vessels retain their exact dimensions during welding. For example, the design requires that the longitudinal contraction between two cylindrical pieces or the like be within 0.102 cm, and the parallel flange parallel to the support plate must be within 0.05 cm within the longitudinal contraction; the shrinkage at the diameter of each perimeter weld must be constant over the entire circumference of the 360 ° C welding zone to minimize deformations and ensure that the x and y axes between the upper flange and the support plate lie within a tolerance of 0.05 cm.

As a result of these strict requirements, the welds are carried out in such a way that the cylinders are in a vertical position and the welding is carried out in a horizontal plane. If the welding tolerances were normal and the weight distribution between the components was more favorable, it would be possible to use conventional welding practices, consisting in the horizontal rotation of the rollers under the welding torch. However, due to the stated dimensions, it is obvious that such a conventional technique would very likely result in a misalignment of the individual components after the welding has been completed. Such deforma205016

However, they are not permissible in the construction of a nuclear reactor.

To meet these requirements, welding has so far been carried out by welding the vessel sections upright and one section resting on the other. In this process, welding is carried out manually at various points along the weld joint, on the one hand to produce a quality weld, the quality of which is determined by X-ray, and on the other hand to prevent shrinkage and deformation. However, it is usually very difficult to produce welds that meet both quality and size requirements, since it is very difficult to distribute heat simultaneously and evenly around each welding spot. Numerous repairs are normally necessary, and the time and cost involved are excessively high. Local repairs of faulty welds result in further unbearable deformations.

The purpose of the invention is to enable the production of high-quality welded joints in large cylindrical vessels or similar structural units in a very precise, predictable and controlled manner so that deformation of the welded parts is minimized.

The object of the invention is a method of welding circular cylindrical objects by circumferential welding, wherein substantially identical welds are simultaneously produced along the weld joint in a plurality of individual beam-symmetrical welding positions. SUMMARY OF THE INVENTION The principle of the invention is that the welding is regulated in the sense of supplying the same amount of heat to the welds in each of the welding positions, and maintaining the same ratio of heat input to filler metal along the weld gap in each welding position at any given time during welding positions relative to the weld joint.

The invention also relates to an apparatus for carrying out the method, comprising a table rotatable about a vertical axis and carrying a cylindrical object whose axis coincides with the axis of rotation of the rotary table and a set of welding kits whose electrodes are adjustable to weld in the walls of the cylindrical object; According to the invention, the welding kits are mounted on a vertical central column that extends through the rotary table within the cylindrical object and are positioned adjacent the walls of the cylindrical object and spaced symmetrically radially.

The method of the invention, performed in the apparatus of the invention, reduces the deformation due to shrinkage by providing the same ratio of heat input to the filler metal volume currently applied to the weld at each of the individual welding positions. Parameters such as arc voltage, wire feed, welding current and rotational speed of the table are kept constant to ensure that this ratio is identical at each welding point at any time. The invention makes it possible to produce high-quality weld joints of large cylindrical containers or the like in a very precise controlled and reproducible manner.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of exemplary welding positions that may be utilized in accordance with the present invention; FIG. 2A is a front elevational view of the welding apparatus; FIG. 2B is a front elevational view of the welding apparatus of FIG. Fig. 2A, Fig. 3 is a top plan view of the center column operator station of Fig. 2A; Fig. 4 is a side elevational view of the center column operator station of Fig. 2A; Fig. 5 is a side view of the tracking system associated _with each welding arm; Fig. 7 is a partial cross-sectional front view of the monitoring system; Fig. 8 is a partial cross-sectional plan view of the welding carriage guide and mechanical stop; Fig. 9 is a plan view of the safety mechanism against falling of the welding cart; 11 shows an anological view of the safety mechanism, but in the locked position, FIG. 12 shows one Fig. 14 is a circuit diagram for maintaining the position of the welding electrode relative to the weld gap, Fig. 15 is a circuit diagram for controlling the vertical and horizontal movement of the welding arm, Fig. 16 17 is a diagram of the delay circuits in the programming circuit of FIG. 16; and FIG. 18 is a schematic diagram of the position servomechanism used to heat the filler metal.

When welding large cylindrical objects, such as the core reactor vessel, the individual welding positions 10 i (Fig. 1) are positioned radially opposite each other and symmetrically about an axis 12 intersecting the vertical axis 14 of the vessel 16.

Giant. 2A and 2B show top and bottom _y device for implementing the method according to the invention having two outer columns and a removable inner central column for storing welding sets against each other by 180 ° C, both inside and outside welded vessel. The apparatus comprises a rotary table 18 on which the container 16 is concentrically vertically mounted, coaxial with the rotary table 18. Below the center of the rotary table 18 a fixed support sleeve 20 is received, in which the conical guide pin 22 of the center column 24 fits exactly. vertical position. The turntable 18 for this use is sized to withstand concentric loads of approximately 2050 t, i.e. a point load of 180 t under static conditions and a dynamic load of 180 t under concentric stress. The diameter of the turntable 18 is about 5 m.

The upper surface of the turntable 18 is smoothly machined and has a series of holes for fastening the clamps 26 (FIG. 2B) that keep the container 16 concentric with respect to the center of the turntable 18.

A separate foot bearing 28 is mounted on the lower side of the turntable 18. The circumferential circular track on the lower side of the turntable 18 is also ground and carries auxiliary bearings 30 and wear plates 32 which also serve as a track for electrically grounded gliders 34. As already mentioned, the lower bearing carrier is provided with a tapered sleeve 20 for receiving the guide pin 22 of the center column 24. A portion of the sleeve 20 projects below the ground level to a depth such that the center column 24 has sufficient stability. To facilitate the removal of the center column 24, a hydraulic jack 36 with a lifting capacity of 90 t is located in the lower part below the sleeve 20. The hydraulic jack 36 is actuated externally and serves to eject the guide pin 22 from the sleeve 23 when the center column 24 is to be extended.

Under the rotary table 18 is a system of grounded gliders 34, which are spring loaded, have a current rating of 2000 A, complement the ground electrical circuit, and protect the bearings against welding current.

The rotary table 18 is rotated by a precision spur gear 38 that extends around the periphery of the rotary table 18 and provides a smooth, adjustable rotational speed that can be continuously adjusted, for example within the range of 0.0053 to 0.058 rpm + 2 ° /O. The gear 38 is driven by a motor 40 which is mounted next to the turntable 18. Power is transmitted from the motor 43 to the gear 38 via a transmission 42 (FIG. 2B).

The middle column 24 is located inside the welded vessel 16 and secured at the lower end by a guide pin 22 that passes through the central hole in the turntable 18 to the sleeve 23. The upper end of the middle column 24 is stabilized by an auxiliary platform 44 supported outside the perimeter of the turntable 18. The upper end of the center column 24 is provided with a conical extension 46 and a collar that is coaxial with the opening 96 in the auxiliary platform 44.

The tapered extension 46 at the upper end of the center column 24 may also serve to accommodate the structural extension used to weld very long vessels for large nuclear reactors. The use of a removable attachment facilitates handling of the center column 24 without the need for a substantially longer fixed column for welding large units.

A bridge 48 is mounted on the center column 24, which is vertically movable and provided with two welding arms 50 and a support platform 52. The two welding arms 53 are the same and are provided with adequate offset such that the welding electrodes 54 are disposed on the horizontal extensions of each welding arm. 50, lie on a common diameter and aligned with the welding electrodes 56 on the outer columns 88.

The lifting platform 52 and the bridge 47 and the carriage 58 are lifted by an alternating brake electric motor coupled with a reduction gear, the two sprockets 60 coupled to the engine being wrapped by a chain 62. The chain 62 is secured to the carriage 58 at one end and the counterweights 64 which are located inside the cylindrical tube 66 in the central column 24.

The carriage 58 is of box construction to minimize the deformation caused by the torsion. Roller assemblies 68 are mounted on carriage 58 and engaging extensions 70 are provided on center column 24 to ensure proper alignment of carriage 58 and welding arms 50.

Each welding arm 50 is formed by a box structure 72 (FIG. 3), which is driven by a rack mounted to the side of the welding arm 50. The travel path of the welding arm 50 is approximately 90 centimeters. The toothed rod of the welding arm 50 is driven through the pinion by an alternating brake electric motor, which is coupled to the pinion via a reduction gear. The drive mechanism is adapted to be reversed. In order to ensure the correct positioning is provided, a locking device is provided which consists of a gear engaging with the gear on the welding arm 50.

A set of vertically stacked apertures 74, approximately 10 cm apart, is provided on the center column 24 (FIG. 4). These holes 74 fit a solenoid actuated pin 76 (FIG. 8J), which forms a mechanical stop against the trolley 58 in the event of a chain or drive failure. The control circuits are arranged so that the trolley 58 moves until the pin 78 west of. An additional electrical connection, which will be described below, prevents the welding device from functioning until the pin 76 fits into one of the apertures 74.

As shown in FIGS. 9, 10 and 11, a fall safety mechanism 78 is provided, which is a spring loaded mechanism located on each carriage 58 and actuated by a drop in chain tension 62. When this occurs, the latch 80 engages the rack rack 82. welded vertically to the center column 24. FIG. 10 and 11 show a side view of the safety mechanism 78 in the released and locked position, and FIG. 9 shows a plan view of the safety mechanism 78 in the released position.

The power and control cables 84 (Figs. 2A, 2B) are connected to the top of the center column 24 and extend down to the carriage 58. In addition to the Nor205016 control cables and welding leads, each carriage 58 has air outlets and a flexible duct fan ensure the flow of fresh air without creating drafts that could adversely affect the shielding gas in the welding zone. In addition, an intercomputer device is provided at each operator station 86 (FIG. 2A) and at another location (not shown) at some distance to provide operator coordination during operation of the device.

On both sides of the turntable. 18, the outer column 88 is disposed. The two columns 88 are substantially structurally the same as the center column 24, except that each has a single welding arm 50. These arms 50 lie diametrically opposite each other on the same straight line as the welding electrodes 54 of the middle column. 24,

The support platforms 52, 53 on the center column 24 and on the outer columns 88 have horizontal extensions 90 that protrude to the weld joint 92 so that the operator can observe the welding from close proximity.

A rectangular auxiliary platform 44 connects d and vertical beams 94 that lie outside the circumference of the turntable 18. This auxiliary platform 44 also provides operator access to the trolleys 58, 59 and serves to accommodate power and control electrical wires that feed the center column 24 and the outer columns 88 The aperture 9S at the front end of the auxiliary platform 44 serves for the passage of the crane rope and center mast extension 24 when the working platform 44 is in the horizontal position. The removable sections of the auxiliary platform 44 allow the operator to easily and safely access the trolley 58 on the center column 24. The auxiliary platform 44 is connected to the auger 98 and the sliding bar 188 so that the platform 44 can easily be lifted to the various levels necessary for welding the vessels 16 different vertical dimensions. The auxiliary platform 44 is also pivotable about one of its abutments so as to be able to swivel away from the center column 24 when storing and removing the center column 24 and the container 16, which is done by a winch driven by an electric motor.

The welding kit 102 is connected to the end of each welding arm 50 by an adapter 108, wherein each welding kit 102 is identical to the others so that all the kits are interchangeable. Attached to the adapter 106 is a slider 104 (FIGS. 2A and 4) having a travel path of 15 cm and allowing a fine vertical adjustment of the welding assembly 102. The slider 104 is actuated by a worm motor 108. When the tracking circuit control is in the automatic operation position, the inner welding electrodes 54 and the outer welding electrodes 56 are vertically adjusted relative to the weld gap 92 by means of this vertical slide 104, as will be described in conjunction with the tracking system.

The tracking system (FIGS. 2A, 3, 4, 5, 6, and 7), which maintains the vertical alignment of the welding electrodes 54, 56 with respect to the weld gap 92, consists of a spring loaded tracking arm 110 that protrudes sideways from the base plate 107 and At the outer end of the follower arm 110, a ball 112 is provided in the holder that runs directly in the weld joint 92. The follower arm 110 is supported on the base plate 107 by a collar 114 that allows vertical movement of the follower arm 110 as it moves. The vertical movement of the tracking arm 110 is sensed by microswitches 16 located on both sides thereof, which translate the vertical movement into an electrical output signal that characterizes the direction of this movement. This output signal serves to control the worm motor 108 and thereby to reposition the welding electrodes 54, 56 against the weld gap 92. Preferably, the ball 112 in the holder is positioned on the tracking arm 110 as close as possible to the welding head without interfering with operator visual inspection of the welding. According to the invention, a delay circuit may be used with a small time delay that corresponds to the time required by the weld gap 92 to travel the distance between the welding electrode 54, 56 and the ball 112 in the holder on the follower arm 110; after this delay time, the worm motor 108 is only actuated to return the welding head to the desired position. This creates a closed control loop that constantly corrects the position of the welding head relative to the weld.

A welding head oscillator 118, such as an Auto Are Model 4S10C oscillator manufactured by Auto Arc-Weld Manufacturing Co. of Cleveland, Ohio, is attached to the vertical slide 104. In this case, the oscillator 118 that is best seen from the otors. 4, provides a controlled stroke of up to 7.6 cm with an adjustable delay at both ends that allows the welding electrode to stop at the ends of the oscillations for a predetermined time.

To the oscillator 118 is connected a control head 120 for regulating the arc voltage, e.g. HWH-3, a product of Union Carbide Corporation, New York, Linda Division. In this case, the control head 120 is used with Linda's Welding Borer type JW-27. The arc voltage control head 102 comprises a reversing stepper motor, a spindle, a recirculation jack and a precision slide. The stepper motor rotates the spindle shaft to raise and lower the recirculating jack. The movable part of the slide is connected directly to the recirculating jack so that it is raised and lowered by the jack carrying the welding electrode. The adapter carrying the welding electrode is fixed by bolts directly to the movable part of the slide. The differential amplifier associated with the head 120 senses, as explained below, the voltage between the welding electrode and the workpiece and compares this voltage to a predetermined voltage that indicates the desired arc length between the electrode and the weld. When the actual voltage has a different value, the stepper motor starts and moves the electrode to the correct distance from the weld. This maintains a constant arc length throughout the welding process.

The welding electrode 54, 56 forms an integral part of each welding assembly 192. Its body carries a gas lens that provides a stable shielding gas stream with a dispersion up to 2.54 cm so that the welding area is clearly visible. The electrode and the power cable are cooled by water which passes through the internal water channels which are connected to the auxiliary platform 44 on the center column 24.

The hot welding wire feeder 122 (FIGS. 3 and 4) is located in the immediate vicinity of each welding electrode and forms a source of preheated filler material that is wound on the spool 124. The feeder 122 thus consists of a welding wire spool 124 which is is driven by the drive 126 and is in contact tube 128 to weld gap 92 on vessel 16 to a location immediately behind the welding electrode 54 in the direction of movement of vessel 16. An AC source is connected between vessel 16 and contact tube 128 so that welding wire 130 passes alternating current, resistively heats it and only the heated wire enters the weld joint 92.

As will be apparent from the following description, the welding wire feed is modified according to the invention so that the amount of weld metal in the weld gap can be controlled according to the energy supplied to the welding electrode.

In addition, the intensity of the alternating current passing through the welding wire 130 is controlled as a function of the speed at which the wire 130 is deposited in the weld gap 92.

The deposition rate of the welding wire in a single welding process varies according to the invention in a programmed manner. To achieve this, the energy supplied to the welding electrode varies. In addition, the power of the welding wire feeder 126 can be varied in an analogous manner to control the deposition of filler material in the weld joint. The welding wire feeder drive 126 drives the tachometer, whose electrical output signal indicates the rate of material deposition in the weld gap 92. The output of the tachometer signal is fed back to the welding wire feed control device to provide the desired filler deposition rate. The welding wire feed programming circuits simultaneously control the welding wire feed rate and the amount of heating current.

A support platform 52 is attached to the trolley 58 on the center column 24, and platforms 53 are attached to the trolleys 59 of both outer columns 88. The angular support structure reinforced with rods and tensioners supports the lattice of both platforms 52 and 53 on which the operator stands. The additional sections on both surfaces 52, 536, 52 and 53 and the tensioning cables allow adaptation to different sizes of the welded vessel 16, while the attachment sections (not shown) are used to secure the additional sections. These additional sections are generally illustrated by the horizontal extensions 99 in Fig. 3.

The piping system delivers air, cooling water, gas to the electrode, welding gas, and purge gas to suitable locations by means of unmistakable, quick-release fittings that are closed at both ends. The size and material of the piping are chosen so that only a slight pressure drop occurs in the conveyed medium and that the piping does not leak through the medium. For example, the gas pipeline can be used as nylon material and polyethylene for the water and air pipelines. All of the systems shown in the drawings are suitable for the use of a welding kit for welding a tungsten electrode in an inert gas shielding atmosphere, however, it is understood that other welding methods that give accurate and reproducible welds may be used according to the invention.

Each welding arm 50 is provided with a control panel 132, all of which are identical and interchangeable with other panels associated with the other welding kits 102. On each panel 132, position controls are optimally positioned for individual welding operations, as shown in Figure 12. functions that are not normally required during the actual welding operation are provided with a second control panel 134 located at each operator station 86.

The interchangeable control panels 132 have an actuator 136 to move the welding arm 50 inwards, an actuator 138 to move the welding arm 50 outwards, an actuator 140 to move the bridge 48 up, an actuator 142 to move the bridge 48 down, a 144 head to adjust the welding head for welding gap adjustment, controller 148 for coarse and fine current adjustment for welding wire heating, controller 150 for setting DC welding current, controller 152 for adjusting oscillator 118, controller 154 for adjusting welding wire feed, controller 156 for adjusting purge gas, controller 158 for automatic adjustment of welding head voltage, controller 166 for automatic welding wire feed, controller 162 for adjusting welding current to the welding head, controller 162 for rotating the turntable 18, controller 166 for starting and stopping welding, and safety switch 16 8 to stop the entire system completely. In addition, a composite control switch 173 is provided to prevent the operation of the operator station 88 on the center column 24 unless a command is sent to both stations 86. Further, a switch key 172 is provided on the control panel 132 to interrupt the logic circuits of the composite control switches. allows the movement of the station with is 203016

12 other operation. In addition to the controls on the control panel 132, direct indicator numbers 174 are provided, namely arc voltage indicator 176, welding wire feed rate indicator 178 and welding current indicator 180. The controls located on the second control panel 134 include controls for adjusting the dwells at the right and left ends of the oscillator oscillator, controls for oscillator speed 118, for oscillation width, control for normal welding wire feed rate, arc voltage sensitivity control, additional gas flow after stop, pumped water controller and rotary table rotation control 118.

The circuits forming part of the device according to the invention serve to initially increase the depth of the weld layer with time during a given welding process until a fixed, predetermined depth is reached. It should be borne in mind that the two welding heads produce identical welds at any point in time at 180 ° positions. When the welding head has traveled 180 °, it can be ordered that the depth of the weld be reduced at the same speed as start welding until the same weld depth is reached along the entire perimeter of the joint. As a result, each welding process preferably provides a degree of overlap.

FIG. 13 shows an example of an electronic circuit for adjusting the DC welding current required for successive welding. The main components of this circuit are an integrator-forming amplifier 200, a voltage level inverter-forming amplifier 202, and an amplifier 204 that functions as a sum amplifier. All amplifiers are powered from a 30 V DC source. Three weld level controls, “start” (206), “welding” (208) and “final” (210) are used as voltage dividers, allowing the desired program to change the layer depth . These controls are provided on the operator panel and are normally adjusted before welding starts.

Before the arc is formed, the output voltage of the amplifier 200 is approximately 10 Vdc, due to the breakdown voltage of the Zener diode 212 and the voltage drop across the diode 214. The output signal of the amplifier 200 is applied to the high side of potentiometers 206 and 210; the voltage from the slider of the potentiometers 208 is applied through the normally closed contacts of relay 216 and through a resistor 218 to the inverting input of amplifier 204. The output signal of amplifier 200 is also passed through the resistor 220 to the inverting input of amplifier 202. via adjusting potentiometer 222 and resistor 224 to inverter 202, is algebraically summed by setting potentiometers 222 with an output signal of amplifier 200 that is 1010 V, so that the output of amplifier 202 is 0 V.

The output voltage of the amplifier 204 is maintained through a normally closed feedback relay 226 of 150 ohms through a normally closed contact of the relay 228 at a level of less than -1 Vdc. This voltage is disconnected from the circuit output by normally open relay contacts

228

Ignition of the DC welding arc produces a signal that energizes relay 228 to release the clamp circuit of amplifier 204 and allow the amplifier 204 to operate as a unit gain inverter while closing the path between amplifier 204 output and circuit output. As a result, the inverse of the voltage selected on the runner of the potentiometers 206 for the initial current appears at the output of the amplifier 204, from where it is routed to the control circuit for supplying DC power.

At the same time, the relay 228 switches the input signal of the amplifier 200 from a fixed positive value from a resistor 23Q that kept its output voltage at -10 Vdc to a negative signal through a potentiometer 232 for current increase and a switch 234 with 0 to 10 and 0 ranges. up to 100 s, from potentiometer 236.

This change in the polarity of the input signal of the amplifier 200 will trigger an onset of integration from -10 V DC at the speed set by the above circuit elements.

When the amplifier 200 begins to integrate from -10 V to 0, the negative input of the amplifier 202 decreases, thereby predominating the input positive signal, resulting in the output signal of the amplifier 202 changing from 0 to -10 V DC at the same time that with output s ^! The amplifier signal 200 changes from –10 V DC to 0.

The output signal of amplifier 202 is applied to the high side of the welding current control potentiometers 208 and the selected voltage level is applied via resistor 238 to amplifier 204 where it is added with the signal from amplifier 200 and resistor 218. The resulting output signal represents a positive variation from the "initial" current. setting to “welding” current setting during the rise time.

When the operator wants to switch to the welding stop phase, he switches switch 168 (FIG. 12) to the stop position to energize relay 216. Relay 218 switches from the start current potentiometer 206 to the resultant welding current potentiometer 210 and input the amplifier 200 signal from the negative signal from the uplink circuit to the positive signal from the downlink circuit. This change in polarity causes the amplifier 200 to begin to integrate from 0 to -10 Vdc. This change has an effect on the amplifier 202 that is opposite to the rise, i.e. its output signal changes from -10 V DC to 0. The end result is a linear change in the output signal of the amplifier 204 that is fed to the welding head, and this from the level set by the welding current potentiometer 208 to the level given by the final welding current potentiometer 210. As already mentioned, the welding metal supply and preheating are programmed according to the welding current.

205916

The tracking circuit, which responds to the position of the tracking arm 210 and corrects and adjusts the position of the welding head relative to the weld gap, also forms part of the DC control circuits, the main components of which are four power diodes 240 and relays 242, 244. 240 forms a two-wire rectifier that rectifies 115 V AC voltage from line 246 to a DC voltage for the motor that corrects head alignment. The excitation voltage is applied directly to the motor while the voltage to the armature is passed through a 10 ohm limiting resistor 248 with a 10 W load and through a reverse relay circuit 250.

When the microswitches 116 actuated by the vertical movement of the tracking arm 110 select the direction of movement, the respective relay 242 is energized when moving upwards and 244 by the moving downwards, which supplies the correct polarity voltage for that direction of movement. When the movement stops, the resistor 248 bridges the armature as a dynamic brake to shorten the free run of the motor. Thus, the movement of the tracking arm causes a deviation signal that drives the motor in the correct direction to minimize the deviation and thereby correct the position of the welding head.

An example of a circuit for controlling the vertical and horizontal movement of the welding arm 50 is shown in FIG. 15. For the following description to be clear, it is assumed that the operator control station A on the center column 24 is the main and the second station B is secondary. As already explained, the circuits for both stations are identical and a simultaneous command must be sent from both operator control stations on the center column 24 before vertical movement begins. Of course, any of the four control stations can serve as the main station and any other stations as secondary.

A 115 V AC power supply is provided to control the vertical and horizontal movement of the welding arm on the columns. When the associated enable button 170 is pressed, 115 V is applied to the terminal. 252 and back to terminal 254 at station A. This terminal 254 is connected to one side of all switching blocks 256 for horizontal and vertical movement. In this case, it is assumed that the upward direction has been selected so that 115 V is applied to terminals 258 and 260.

The clamp 260 is attached to one end of the solenoid 78, which serves to eject the locking pin 76 that fits into the aperture 74 in the center column 24 and holds the welding arms 50 in the selected vertical position. The other end of the solenoid 78 is connected through a normally closed gear limit switch 262 of the gear interlock, which serves to secure the welding arms in the selected position, and via a normally closed contact of relay 264 to the second pole of the AC 115V. the solenoid 78 energizes and the locking pin is pulled out of the aperture 74 and encounters a switch 270 whose contacts switch.

The terminal 258 is connected to the up and down joints of the vertical motor contactor located on the center column 24. The upward joints consist of a normally open contact set on the lift coil, which is connected to a 115 V power supply. down is formed by a normally closed set of contacts that is connected to one side of the lift coil. The other side of the pickup coil is coupled to terminal 266 via a normally coupled terminal 266 via a normally closed up limit switch 268 and via a normally open limit switch 270 of the locking pin 7S that is not closed because pin 76 has been removed from the respective hole 74 to This circuit energizes a vertical motor lift coil that applies a 440 V three-phase voltage to the motor for upward movement. At this point, the side of the lift coil that is connected to the 115 V voltage on the vertical motion drive is maintained at that voltage through the normally open contacts so that when one or both of the associated enable and up movement buttons are released, the upward movement continues until the other side of the lifting coil is idle. This occurs when the locking pin 76 engages the next hole 74 or when the end of the travel is reached and the switch 268 indicating the lift limits is switched.

In accordance with FIG. 16, a positional servomechanism circuit is provided to program the hot welding wire feed, including, for example, an operational amplifier 300 operating as an integrator, an amplifier 332 operating as a cathode follower, and a relay 304, 306 for switching. In the static state, the output of the amplifier 300 is maintained at 0V due to a DC input voltage of -15V through the resistor 308 and normally closed contacts of the relay 304, which attempts to bring this output signal to a positive value, thereby preventing the diode 310 forward. Since the output of amplifier 300 is routed upstream of the welding wire voltage setting potentiometer 312, which indicates the level at the input of amplifier 302, the output of amplifier 302 is equal to 0.

IN.

After welding begins, as the welding wire approaches the workpiece, the relay 304 energizes and connects to the amplifier input. 330 a rise time potentiometer 314 and a potentiometer 316 that sets the input of the amplifier 300 to integrate into a voltage of approximately -10 V DC. This 10V DC voltage is applied through the wire heating voltage setting potentiometer 312, the set voltage is set by the slider of this potentiometer 312, and applied to amplifier 302. The output of amplifier 302 is exactly the same as its input, but at a substantially lower im205016. The output of the amplifier 302 is then fed to the input of a servo positioner (not shown). During welding, the setting of the potentiometer 312, which adjusts the voltage for heating the welding wire, can be changed, thereby changing the output signal of the amplifier 302, which changes the position of the control transformer header in the power supply circuit.

If the procedure is to be stopped, the end delay timer 318 will operate (FIG. 17j and energize relay 306. This relay will switch the amplifier input 300 from the uplink circuit to the downlink circuit, which includes the down potentiometer 320 and the down pot calibration potentiometer 322. This signal causes the amplifier 300 to begin to integrate from approximately -10 V DC to 0, causing an analogous change in the output of the amplifier 302, which reduces the drive signal to the position servomotor.

An AC-powered positioning servo regulator that can be used to supply programmed electrical current to preheat the welding material is shown in Figure 18 and includes as an essential component an operational amplifier 324, an O-type controller 326 having an adjustable gain from X = 1 to X = 100, voltage divider 328, double-sided DC bridge 330, consisting of two ignition circuits 332 and four thyristors 334, and a DC motor 362 with tachometer dynamo 360 that drives the control transformer 338, a potentiometer 340 for welding wire feed and positional recognition potentiometer 342.

For simplicity, it is assumed that the control transformer 388 and the position recognition potentiometer 342 are synchronized with respect to the angle of rotation, and both are set to the lower end counterclockwise so that the output of the position recognition potentiometer 342 is 0. If despite the control signal resistor 344, the output signal of the amplifier 324 is zero so that no signal to drive motor 362 is generated.

As soon as the welding program begins and a negative supply signal arrives at the amplifier 324 through the resistor 344, the signal is amplified to the extent given by the gain of the amplifier 324 and appears at its output as a positive signal. This signal is applied to the polarity sensing diode 346 and through the resistor 348 to the ignition circuit 330, which connects the thyristors 352, 354 to the positive anode voltage and creates a positive DC component on the armature side 356 of the position servomotor. This DC component causes the motor 362 and the tachometric dynamo 360 to rotate in the direction of arrow C and move the control transformer 388, the poten-COmeter 340 for the welding wire feed, and the position recognition potentiometer 342 towards their clockwise ends. . As the increasing positive voltage from the position potentiometer 342 approaches the amplitude level of the negative control signal, their algebraic sum approaches zero. When this deflection signal amplified by amplifier 342 is reduced to inul, the motor 362 does not receive the excitation signal and stops at that position.

When the negative control signal coming through the resistor 344 is reduced by manually rotating the voltage adjusting knob 148 to heat the welding wire that is located on the panel of FIG. 12, or automatically decreases when the welding stops, the positive voltage from the runner of the position recognition potentiometer 342 will prevail, which is amplified and inverted to the amplifier 324 from where it passes through the polarity-sensing diode 358 to the ignition circuit 360. thyristors 362, 364 and generate a negative DC voltage at the side servo armature pin and tachometer dynamo pin 356 that moves the control transformer 338, the wire feed potentiometer 340, and the position recognition potentiometer 342 back to the end corresponding to the counterclockwise movement. until the deviation is zero again.

The tachometric dynamo 360, which is directly coupled to the armature shaft 362 of the motor, transmits a signal of opposite polarity to that supplied by the amplifier 324. This signal is routed via a setting potentiometer 364 which is set to an optimum positional response and allows slight oscillation in the zero position. The main function of potentiometer 366 is to set the optimal width of the zero zone.

When the positional servomechanism automatically stops, a normally negative signal at resistor 344 passes through zero and continues to a value of approximately -j-0.5 Vdc. This prevents the zero voltage from appearing above the minimum level, so that the control transformer 338 rotates counterclockwise and strikes the rubber stop where it is disengaged by the sliding clutch until the arc goes out.

Two setting potentiometers are connected in series with the position recognition potentiometer 342. The potentiometer 368 allows the maximum desired setting of the control transformer 338 clockwise when the maximum control signal is at the resistor 344. The potentiometer 378 allows counterclockwise adjustment at a minimum signal at resistor 344.

The amplifier 372, which acts as a follower, converts the output voltage from potentiometer 340 to a low impedance level and conducts it back to the circuit chassis.

The welding wire feed servo mechanism and its logic circuits may include, for example, the following main components: two timers 374 (start delay) and 318 (stop delay), which are solid state circuitry, and an operational amplifier 376 that operates as integral and proportional a control preamplifier, an ignition circuit 378, and a two-way thyristor bridge 380. The relays used in this circuit are the following: relay 382 for automatic operation, relay 306 for drop, relay 386 indicating that the wire feed motor is switched, relay 381 to move up; and a relay 388 for moving down and in. A -24 Vdc voltage is applied through the closed ‘wire feed switch to the relay coils 384, 388, 386 at the appropriate time, allowing wire feed.

As soon as a DC arc is formed on the welded surface, a 24 V DC voltage is applied to terminal 374 via terminal 393 (FIG. 17). This causes the timer 374 to delay the start for a given time selected by the delay start button 394 on the control panel, the delay range being given by the switch 392, for example 0 to 10 or 0 to 100 s. its normally open contacts 396, which automatically wakes up the oscillator. When the switch 398 indicating the wire feed method is in the automatic position, -24-24 V DC is applied through timer 374 and switch 398 energizes relay 382. Relay 382 applies + 24 V DC via normally closed contacts 400 to coil of relay 388 which applies this voltage -j-24 V to coil of relays 384 and 386. The selection of relays 384, 388 and 386 completes the output signal from thyristor bridge 380 (Fig. 16i), which is applied to armature 362 of motor thus prepared for feeding the welding wire. At this point, the displacement circuit is operable. A second function of relay 382 is to close the circuit 402 that actuates the welding contactor in the AC power source. Finally, relay 382 applies a positive control signal from potentiometer 404 for shifting down through the now closed contacts of relay 386 and through resistor 436 to the sum terminal of amplifier 376.

The amplifier 376 receives the control signal, inverts it, and begins to integrate about 10 V DC into the output signal, a value provided. Zener diode 408. When the output of the amplifier 378 becomes negative, the polarity detecting diode 410 conducts this signal to the control winding of the ignition circuit 378, which ignites the thyristors 412 and 414 in the rectifier bridge 383. The output signal from this bridge 380 is passed through the resistor 416, which serves to limit high current surges, to the motor armature for the welding wire feed. A tachometric generator 30 is connected to the motor armature 362 and begins to generate voltage at the potentiometer 418. Potentiometer 418 divides this voltage and sends the desired voltage across resistor 423 to amplifier 376. This voltage has the opposite polarity to the control signal supplied through resistor 406. Once motor 362 reaches the speed at which the tachometer dynamo signal 363 on resistor 420 is equal to the signal at of resistance 406, the algebraic product is zero, so that amplifier 376 stops integrating. The capacitor 422 maintains the output signal at the level required to run the motor at that speed.

If motor speed 362 exceeded a setpoint, an inverted differential signal at the output of amplifier 378 would cause integration to continue to positive values, ignition circuit 378 would ignite thyristors at a smaller phase angle, and motor speed 362 would decrease by setpoint.

^; Examination of amplifier 376 as an integral and proportional servo regulator shows that when the motor runs slower than desired, the actuator is predominant ^. gnal, resulting in a more negative output, ignition of thyristors at a greater phase angle, and increased speed. Conversely, when the engine runs faster than necessary, the tachometric dynamo signal predominates, resulting in less negative output and reduced speed. As a result, the motor operates at a steady state at the desired speed, there are no amplitude errors of the control and feedback signals, and the circuit can be referred to as a zero-order proportional steady-state servo regulator, type 1.

There is automatic speed control in the device, starting at a voltage of 10 V from a 15 V DC power supply to power the applicable amplifiers, and this voltage is applied to the end of the five-threaded logger that controls the maximum speed. The slider of this potentiometer is connected to the main panel and to the end of the wire speed potentiometer, which is connected to a control transformer in an AC voltage source. The other end of this potentiometer returns to the main panel on the minimum speed potentiometer slider. The second potentiometer for minimum speed control is connected to + or - 15 V DC.

The circuit described is a potentiometer for controlling the speed of the wire feed, at both ends of which there are dampers. The control signal is taken from the potentiometer 343 and applied to the amplifier 372, which functions as a follower. ‘The output of amplifier 372 is routed to the chassis where the hot wire circuits are located.

When the contactor is energized and the wire slowly moves toward the workpiece at a given feed rate, the current sensing circuit 424 (Fig. 16) energizes relay 304 as soon as it touches, causing the position actuator to move up and switch Speed Control to potentiometer controlling speed supply of wire. Since that ^dkamž: to slowdown until the speed of the wire feed subordinated potentiometer for adjusting the voltage · hot wire potentiometers dials the "minimum" and "maximum" is used to balance the ratio of power and speed 'wire.

When the "stop" switch is actuated, the relay 306 wakes the relay servo motor to descent, and the stop delay timer 318 starts counting the time for the time determined by setting potentiometer 426 and switch 428, which ranges from 0 to 10 and 0. up to 100 s (Fig. 17). At the end of the Stop Delay time, normally closed contacts 49D open and disconnect the oscillator, while normally closed contacts cut-24 V DC to the relay coils 388 and 386, disconnecting the wire feed motor from the thyristor bridge 380 and connecting a dynamic braking resistor 430 (FIG. 16) to armature 368, thereby shortening the overrun.

On the control panel of each operator station there is a two-position toggle switch 156 (Fig. 12) which, when actuated, simultaneously energizes the gas and water solenoids ordered by the control station for the respective weld position and the weld position exactly opposite it. .

To enable the sequential operation of the individual controls on the control panel, the purge gas switch must first be in the closed position. This electrical interconnection prevents damage to the entire system, which could occur without gas flow. The switch 164 '(FIG. 12), which indicates the start and stop positions, is a two-position toggle switch located at the bottom center of each panel.

On the bridge 48 mounted on the center column 24 are located two RF power units and on each of the outer columns 88 one unit. Each of these units includes a relay sensing circuit that signals arc burning. The RF energy begins to pass when the welding switch 166 located in the middle of the control panel is energized. This switch 166 can only be switched after excitation of the gas and rotation control elements. The high-frequency oscillations extend until the arc is formed, where the arc is permanently between the welding electrode and the weld joint and is maintained by the DC. welding current.

The DC welding current controller 162 (FIG. 12) is located at the bottom right of the Interchangeable Control Panel and in the stationary panel assigned to each welding assembly. Three current settings, “Initial”, “Welding” and “Resulting”, are set before starting welding on the stationary control panel. The ascending and descending speed controls are calibrated in seconds, while the ascending speed is the number of seconds during which the linear changeover from the initial! current to the welding current. There is a toggle switch on the chassis in the stationary control panel that sets the range of rise and fall timers to either 0 to 10 s or 0 to 100 s. The descent can be initiated manually by switching the start welding switch 166 to the stop position. . To prematurely turn off the arc, press the security button 168, which is the large button at the bottom right of the interchangeable panel.

As noted, arc voltage control heads 120 are provided on each oscillator on the welding head assembly to control the distance between the electrode and the weld joint. The DC digital voltmeter 176 (FIG. 12) shows the actual arc voltage or a preset reference voltage to regulate the arc voltage depending on the position of the toggle switch 146, which is centrally on the interchangeable operator control panel. The arc voltage sensitivity switch, located on the stationary control panel, sets the control head delay timer, which delays the start of the voltage control effect after the start of the arc and keeps the control head in a fixed position for this time. This time must be determined experimentally to suit the working conditions and to meet all requirements. In the exemplary embodiment of the invention, the maximum time is 10 s.

The dial 176 sets the reference voltage to control the arc voltage when the voltmeter switch is in the reference position, the voltage being set according to the voltmeter reading. When the switch is set to arc position, the voltmeter shows the actual arc voltage during a certain welding cycle time. Obviously, both voltages will be the same when the switch for automatic operation and disconnection of the control head on the stationary control panel is set to automatic and when the control is operating correctly. Control does not take place when the switch is set to the off position. The movement of the head can be controlled by a switch for moving the head out and in.

The circuits in the arc voltage regulator form a module that is installed in the operator panel. This module contains a stable, high gain differential amplifier that amplifies the deviation signal generated by the difference ‘between the predetermined reference voltage and the arc welding voltage. Even small deviation voltages, for example 0.01 V, cause an alternating pulse to be sent to the stepper motor of the control head 120 to correct the deviation by adjusting the arc length. Each pulse causes the control head to move the welding electrode by 0.00318 cm, in a direction that depends on the sign of the deviation signal. The offset correction is performed in a stepper motor at a rate of about 60 pulses per second in the selected embodiment.

The tracking system is controlled by a three-position toggle switch that has the 'automatic', 'off' and 'manual' positions. In the manual control position, the switch is wired to allow pre-adjustment of the welding head. In the automatic position, the microswitches keep the welding head in a constant position relative to the gap.

The oscillator control circuits are divided between the interchangeable control panel and sfacio205016 our control panel. The oscillator width, right weld, left weld, manual control, cutoff, and automatic switches are located on the stationary panel, while the switch 152 that limits the oscillator movement to one side of the fixed position is located on the interchangeable control panel. In the automatic position on the stationary control panel, the circuits are adjusted such that the oscillations begin at the end of the welding wire feed-off delay time.

The hot wire feed controllers include AC servo motors connected to an AC supply voltage and controlled by the bidirectional thyristor system 334 described with reference to FIG. 18. The servo controls 154 are located on the interchangeable operator control panel below the wire feed rate control. In order for the wire feed system to function, the switch for automatic wire feed and for turning off the wire feed must be in the automatic position. When this switch is in the off position, the wire can only be fed when the switch is moved up or down. The feed rate is given by the wire feed switch on the interchangeable control panel; When the switch is in the automatic position, the wire start delay controller starts counting from the moment the arc is formed. At the end of this predetermined time, the wire begins to feed at the feed rate. When the welding wire touches the molten metal, the alternating voltage of the preheating wire starts to rise from the minimum to a predetermined value for a time that is set on the rise time controller 148. At the same time as the DC current begins to decrease, the AC voltage begins to decrease to a minimum for the time set by the time delay controller. At the same time, the timer starts to count the wire stop delay.

The vertical movement of the carriages 58, 59 is triggered by the buttons 149 and 142 at the top of the interchangeable panel of FIG. 12. The carriage 58 is to be moved on the center column 24 and there are two operators and the switch 172 is in the associated position. an associated enable button 170 lying adjacent to the switch key on the control panel while the second operator selects the direction of movement before the movement can begin. If there is only one operator on the center column 24, the enable switch 172 in the unattended station must be turned off. As soon as the movement in one direction begins, the operator holds the corresponding knob in the depressed position until the movement is to stop. When the operator releases the pushbutton, the movement continues until the spring loaded pin 78 (FIG. 8) engages in the next hole 74 on the pole 24. Fine adjustment of the vertical slide 104 (FIG. 4) must then be used to align the welding head with the joint.

The vertical movement on the outer columns 88 is carried out simply by pressing the respective button. The associated enable buttons are unnecessary as the movement on each outer column 83 is independent. It goes without saying that the vertical movement on the outer columns can be coordinated in the same way as it was. described for middle column 24.

The horizontal movement of the welding arms 50 on the center column 24 is performed in the same manner as the vertical movement, except that the buttons 13S and 138 are pressed (FIG. 12). The horizontal movement on the outer columns 88 is performed in the same manner.

To ensure that the pre-welding steps are in the correct order and to avoid defects at the start of welding, the system includes logic circuits that require that the specific actions to be performed are performed in the correct sequence before the welding starts. head. The logic sequence requires that the following steps be performed in the order shown before welding begins:

1. The main power supply must be switched on.

2. It must be verified that the carriage locking pin, which adjusts the welding arms on the main mast, is inserted into the hole.

3. The gas supply is open.

4. The rotary table is set in motion.

5; High-frequency switch excitation is provided.

At this point, the system is in the ready position and the lamp 182 on the operator control panel (FIG. 12) lights up. The switch 172, which is operated by a key and which forms the associated enable switch at the opposite station, is then rotated to the on position. The system is now ready for single head welding. The switch 168 (FIG. 12) that triggers the welding is energized at this point and pulls the contactor in the direct current source, creating an arc. This will turn on the composite bulb on the opposite station.

The following sequence will start automatically once the previous steps have been performed in the correct sequence:

1. The wire feed delay circuit is energized.

2. Actuate the control head for automatic voltage control.

3. The DC current starts to increase,

4. The welding wire feed starts.

5. The limp movement starts.

8. Arc voltage control starts.

Depending on the operator's choice, the end of the welding process is triggered by switching the start and end welding switches 166 to the stop position, whereupon the following processes are carried out automatically:

1. The DC current drop begins.

2. The voltage drop for heating the wire starts.

3. The wire stop delay starts.

4. The AC power source is disconnected.

5. The oscillator is disconnected.

The operator can then press the safety button 168 to ensure that the arc is extinguished, that the rotation of the rotary table has stopped, that the gas supply is disconnected, and that the rest of the system is de-energized.

When welding starts with two welding heads, that is to say with two heads working simultaneously, both the operator stations perform verification of the position of the locking pin, the connection of the gas supply, the rotation of the rotary table and the excitation of the high frequency. When both stations are in the "ready" position, one of the two operators can start welding with its switch to start welding.

It is obvious that said logic system can be realized by series connection of the product gates. Each successive gate in series receives an input signal from the previous gate once the corresponding step has been performed. In this way, the correct sequence of operations is ensured, ensuring the reproducibility and perfection of each weld.

Claims (15)

CLAIMS 1. A method of welding circular cylindrical articles by circumferential welding, wherein substantially identical welds are simultaneously produced along the weld joint in a plurality of individual beam-symmetrical welding surfaces, characterized in that the welding is controlled in terms of supplying the same amount of heat to the welds in each of the welds. welding positions and maintaining the same ratio of heat input to filler metal volume along the weld gap in each of the welding positions. at any given time during the movement of the welding positions relative to the weld joint. Method according to claim 1, characterized in that the welding positions are moved at a constant speed with respect to the weld joint and at the beginning of the welding the depth of the weld layer in the weld joint increases at a constant speed until a predetermined depth is reached. until the beginning of the adjacent welding position is reached, whereupon the depth of the weld layer decreases at a constant speed to a point where a predetermined depth has been reached by the adjacent welding position to produce the same weld depth along the joint. Method according to claim 2, characterized in that the material constituting the weld layer is heated before being introduced into the weld joint and the amount of heat supplied to the material before welding is automatically controlled depending on the depth of the weld. 4. The method of claim 3, wherein the filler metal feed rate is automatically and programmatically controlled to adjust the filler metal feed rate to the welding spot and the amount of energy supplied to the welding electrode varies depending on the metal feed rate of the weld joint. clutches. 5. The method of claim 4, wherein the filler metal is resistively heated prior to introduction into the weld in a controlled manner by controlling the electrical current used to resistively heat the metal relative to the metal feed rate to the weld joint according to a predetermined dependency. 6. A method according to claim 5, wherein the filler metal is directly resistively heated OF THE INVENTION by conducting alternating current through the filler metal. 7. An apparatus for carrying out the method according to items 1 to 6, comprising a table rotatable about a vertical axis and supporting a cylindrical object whose axis coincides with the axis of rotation. a set of welding sets, the electrodes of which are adjustable to the weld gap in the walls of the cylindrical object, characterized in that the welding sets (102) are supported on a vertical central column (24) which passes through the turntable (18) inside the cylindrical object ( 16), and are disposed adjacent the walls of the cylindrical article (16) and spaced symmetrically radially. Device according to claim 7, characterized in that the central column (24) has at its lower end a conical guide pin (22) which fits into the stationary cavity of the support sleeve (20) located below the center of the rotary table (18). 20), a jack (36) is mounted under the guide pin (22) of the center column (24) to lift the center column (24). Device according to claim 7 or 8, characterized in that the welding sets (102) are supported by adjusting welding arms (50) which laterally project from the center column (24) and are operable by a pull or retract command, the welding sets ( 102) are assigned control panels (132) supported by the center column (24) and connected to the welding arms (50). 10. Apparatus according to claim 9, characterized in that it comprises drive motors (108) for adjusting the control panels (132) and the welding arms (50) in a vertical direction along the axis of the center column (24). The apparatus of claim 10 comprising oscillators (118) for vertically oscillating movement of the welding kits (102) on their horizontal welding path and interrupting the oscillating movement of the welding kits (102) at the oscillation ends for a predetermined period of time. Device according to one of Claims 9 to 11, characterized in that on each welding arm (50) a tracking system is provided for heating the weld joint (92), consisting of a support sleeve (114) with a tracking frame (110) provided with a tactile ball (112) and vertically movable according to changes in the vertical position of the weld joint (92), and microswitches (116) for sensing the vertical movement of the tracking arm (110) connected via a delay circuit to the drive motor (108) to adjust the welding arm (50) welding kits (102). Apparatus according to one of Claims 7 to 12, characterized in that in each welding assembly (102) a differential amplifier is connected in the control head (120) for the electrical power welding electrodes (54) to measure the gap voltage between the welding electrode ( 54) and a welding location and for comparing the voltage to a preset value and a stepper motor for adjusting the welding electrode (54). Device according to one of Claims 7 to 12, characterized in that each welding assembly (120) is provided with a device for automatically regulating the welding wire feeder (122) to vary the amount of welding wire (130) fed to the welding site. , according to a predetermined power-dependent program of the welding electrode (54). Apparatus according to Claim 14, characterized in that it comprises a contact tube (128) for supplying electrical power to the welding wire (130) before it is fed into the weld joint (92) and a controller for varying the heating current according to the welding wire feed rate. 130) into the weld joint (92).