Electric Resistance Welding
Theory Fundamentals of Resistance Welding
The method of resistance welding is based on the pre-heat the edges of welded parts of the product arc, rotating in a magnetic field, followed by mechanical compression of the (draft).
Resistance Welding Technology
In general, in this pipe welding technology method it comes down to the selection of the desired mode of welding, pipe compression efforts. This information is made into a table at end of article
Equipment for Resistance Welding
resistance welding application method has allowed to create agile small-sized welding equipment with a relatively low weight.
10:13 PM
Equipment for Resistance Welding
resistance welding application method has allowed to create agile small-sized welding equipment with a relatively low weight.
During installation of the type developed VNIIESO UDC-204 for mechanized welding butt water-gas supply pipe for installation of sanitary equipment at the construction site. Set includes a portable welding head, a portable pneumatic device and the power unit. Weight 8.5 kg of the welding head. The welding head consists of a clamping mechanism pipes, precipitation, and the drive system of the excitation magnetic field. In order to simplify the design of the welding head, reducing its size and providing welding in confined spaces clamping mechanism installed so that they, along with welded pipes for the heating of the entire process razo remain fixed relative to each other. Clamping of pipes is done by hand high-speed three-hinged clamps. Drive Air - Pneumatic diaphragm placed between two covers. The pressure is transmitted to the diaphragm and the plunger through a lever welding head - on the jaws with the trumpets. The excitation system of the magnetic field is made detachable in the radial direction and consists of four coils, creating a gap between the pipe radial magnetic field, providing the movement of the arc along the edges of welded pipes. Field coil does not have a separate power source and connected in series in the welding circuit. To set the gap between the pipes before welding is a rotary knife. Pneumatic hand-held device consists of a receiver, and electro-pneumatic valve controlling the compressed air from the compressor to the welding head. The unit includes a power supply of the arc-welding a standard DC-DC converter, power supply, compressed air - compressor, power equipment and a drum for cable and hose. The welding head is connected to a pneumatic device, wires and a hose length of about two meters. The length of the pneumatic device to the power supply unit - 75 pm For ease of installation conditions in the welding wire has a small cross section (25 mm2). The presence of relatively high voltage drop across the welding wires makes it necessary to use welding inverter 500 and the welding current at a nominal 260 a. The block provides the necessary hardware cycle of welding: Welding current switch, adjustable time delay of heating, the inclusion of sediment pressure after a predetermined time warming up to the draft of a shock. Work on the installation as follows: the ends of welded pipes are clamped in the welding head. Carbon rod is excited by an electric arc between the edges of the pipe and then automatically go through the following processes: melting of the edges of the rotating arc sediment off the welding current and removal of pressure precipitation. When working with the installation must comply with safety regulations and fire regulations established for welding with an open arc. During the welding process should not touch the pipes being welded. Tensions between the pipes in the heating process has the same magnitude as between the electrode and the workpiece in manual arc welding, ie, in the 26-28. Welding can be carried in any position at a distance of not less than 30 mm from the wall. Welded joints are of equal strength base metal. Grat is evenly distributed around the perimeter of the pipe, the quantity did not exceed 1-15 mm. When hydraulic tests on the density of the welded specimens withstand pressure of 300 kg/cm2. For welded tubes, resistance welding, all acceptable methods of quality control is used in resistance welding. The most widely used type of installation UDC-204 is, in welding the heating systems of buildings. Mounting and installation of heating systems for welding is performed, usually in advance. Billet risers are manufactured at the plant. Implementation install UDC-204 provides the following economic benefits:
Electric Resistance Welding
Theory Fundamentals of Resistance Welding
Resistance Welding Technology
Equipment for Resistance Welding
During installation of the type developed VNIIESO UDC-204 for mechanized welding butt water-gas supply pipe for installation of sanitary equipment at the construction site. Set includes a portable welding head, a portable pneumatic device and the power unit. Weight 8.5 kg of the welding head. The welding head consists of a clamping mechanism pipes, precipitation, and the drive system of the excitation magnetic field. In order to simplify the design of the welding head, reducing its size and providing welding in confined spaces clamping mechanism installed so that they, along with welded pipes for the heating of the entire process razo remain fixed relative to each other. Clamping of pipes is done by hand high-speed three-hinged clamps. Drive Air - Pneumatic diaphragm placed between two covers. The pressure is transmitted to the diaphragm and the plunger through a lever welding head - on the jaws with the trumpets. The excitation system of the magnetic field is made detachable in the radial direction and consists of four coils, creating a gap between the pipe radial magnetic field, providing the movement of the arc along the edges of welded pipes. Field coil does not have a separate power source and connected in series in the welding circuit. To set the gap between the pipes before welding is a rotary knife. Pneumatic hand-held device consists of a receiver, and electro-pneumatic valve controlling the compressed air from the compressor to the welding head. The unit includes a power supply of the arc-welding a standard DC-DC converter, power supply, compressed air - compressor, power equipment and a drum for cable and hose. The welding head is connected to a pneumatic device, wires and a hose length of about two meters. The length of the pneumatic device to the power supply unit - 75 pm For ease of installation conditions in the welding wire has a small cross section (25 mm2). The presence of relatively high voltage drop across the welding wires makes it necessary to use welding inverter 500 and the welding current at a nominal 260 a. The block provides the necessary hardware cycle of welding: Welding current switch, adjustable time delay of heating, the inclusion of sediment pressure after a predetermined time warming up to the draft of a shock. Work on the installation as follows: the ends of welded pipes are clamped in the welding head. Carbon rod is excited by an electric arc between the edges of the pipe and then automatically go through the following processes: melting of the edges of the rotating arc sediment off the welding current and removal of pressure precipitation. When working with the installation must comply with safety regulations and fire regulations established for welding with an open arc. During the welding process should not touch the pipes being welded. Tensions between the pipes in the heating process has the same magnitude as between the electrode and the workpiece in manual arc welding, ie, in the 26-28. Welding can be carried in any position at a distance of not less than 30 mm from the wall. Welded joints are of equal strength base metal. Grat is evenly distributed around the perimeter of the pipe, the quantity did not exceed 1-15 mm. When hydraulic tests on the density of the welded specimens withstand pressure of 300 kg/cm2. For welded tubes, resistance welding, all acceptable methods of quality control is used in resistance welding. The most widely used type of installation UDC-204 is, in welding the heating systems of buildings. Mounting and installation of heating systems for welding is performed, usually in advance. Billet risers are manufactured at the plant. Implementation install UDC-204 provides the following economic benefits:
- Excludes costs for oxygen, acetylene, electrodes, etc., the installation of pipe welds only by heating the ends of themselves and their squeezing after heating;
- increased productivity and quality of assembly and welding operations;
- reduced requirements for the qualification of welders, welder instead of V-VI of the discharge, performing manual arc welding, installation services performed by the operator level III;
- reduction of harmful substances released during welding galvanized pipe, due to the short duration of the process and the small area heating.
- The installation can be welded pipes with diameter 21.3 mm and 26.8 mm with wall thickness up to 3.2 mi. In the transition from one pipe size to another is a change of jaws and changing the heating time.
- Rated welding current of 260 a. The amount of current during welding of pipes of all sizes remain constant.
- Type of welding current - constant.
- Duty cycle - 2.5%.
- The voltage on the arc - in the 25-26.
- Air-pneumatic actuator.
- Air force, 1,800 kg at a pressure of compressed air - 5.5 kg/cm2.
- Welding time - up to 3 seconds.
- Plant capacity - 30 welds / hr.
- Unit weight: welding head - 8.5 kg; perenosnoo receiver - 8.0 kg; aggregate supply - 1000kg.
- Dimensions: welding head - 195x185x550, a portable receiver - 252 X236 X 360; aggregate supply - 1470H900H1490.
Electric Resistance Welding
Theory Fundamentals of Resistance Welding
Resistance Welding Technology
Equipment for Resistance Welding
10:10 PM
Resistance Welding Technology
In general, in this pipe welding technology method it comes down to the selection of the desired mode of welding, pipe compression efforts. This information is made into a table at end of article
Tubes designed for welding, the ends must be perpendicular to the axis of the tube, without burrs. For resistance welding ends with suitable blanks obtained after cutting lathes, machining truboreznyh, saw a pendulum, followed by removing the burr drill with a diameter equal to the inner diameter of the pipe. Stripping of blank surfaces from dirt and rust is not required. The process of developing resistance welding technology is practically reduced to the choice of rational parameters of heat and precipitation, to ensure the achievement of equal strength of welded joints with the base metal, and the absence of defects in the welded joint. The required quality of welded joints is obtained by squeezing heated uniformly over the cross section edge products. The uniformity of heating is achieved by selecting the optimum welding conditions. Satisfactory formation of the joint can be obtained for different values of welding current and the duration of heating. Each diameter of the pipe corresponds to a range of welding currents within which ensured the formation of a satisfactory joint. The essential quality of welding has vliyanie.na current density in the product. At a current density of less than 0.5 A/mm2 high quality welds can be achieved in case of mechanical precipitation only when accumulated at the ends of the welded metal parts of the product has already begun to flow, ie, after the appearance of flowing liquid metal layer. At the same time to ensure the stability of the welding process is necessary to maintain the clearance between the workpiece, which can only be achieved by using tracking systems. At a current density of more than 0.5 A/mm2 mechanical sediment can be carried out in the presence of liquid products at the ends of a metal film without the appearance of flowing layer. This allows the heating of pipe ends at fixed relative to each other parts of the welded products, reduces the amount of planted metal, ie, reduces the magnitude of the internal and external burrs. Due to the fact that the heating is carried out at the fixed parts of the product, it becomes possible to simplify the design of the equipment by eliminating the complex tracking systems. If the power supply is not limited to, seek the upper limit of the welding current. Given a pre-rational power supply is the most efficient use of its power. On the uniformity of heating of the ends of the perimeter of the product significantly affects the rate of displacement of the arc. found that in the final stage of heating may be a local increase in the gap, the so-called digging. In the metal, where the digging occurred, a zone of low strength weld, or even lack of adhesion compounds. Cause of tearing is, apparently, the appearance of liquid metal drops, the speed of movement is much smaller than the velocity of the arc. Due to the speed difference between having a delay in the movement of the arc, leading to local melting of the ends and release of molten metal from the joint. One way of wresting control is a periodic change in the direction of rotation of the arc (reverse), which makes it possible for some time to disperse the liquid metal on the edges, not allowing him to collect in one place. However, reversal, especially in high-power modes, is malopodhodyaschim and could be hard to remedy. It was established experimentally that the combination of current density in the product of more than 0.5 A/mm2 arc moving with velocities of the order of 100-150 m / sec can eliminate digging, and to provide uniform heating of the edges. Based on this value is determined by the radial induction in the gap and magnetizing force excitation coils. Defining the parameters of the excitation coils (the number of turns, wire cross-section and current) are made on the basis of structural considerations and the way power coils (whether or arc by successive inclusion in the welding circuit). The magnitude of the specific efforts of precipitation during welding technology slightly higher compared to the contact welding, and is 8-10 kg/mm2 for mild steel. The optimal value of the installation of the gap between the welded parts of the products practically does not depend on the size of the welded products. For example, for pipes up to 100mm - the optimum size of this gap is 2 mm, and for pipe diameters from 100 mm to 300 mm -2,5-3. Deviations from the optimal size of the gap as to decrease (to 1.5 mm for pipe diameters up to 100 mm and 2 mm for pipe diameters 100 - 300 mm) and upward (up to 2.5 mm for pipe diameters up to 100 mm to 3.5 mm for pipe diameters of 100-300 mm) can lead to a breach of the stability of motion of the arc. Summary of welding modes, providing a satisfactory quality of welded joints in the fixed parts of the product in the process of heating, for pipe diameter 17-114mm of steel St20 STZ-listed in the table.
See also:
Electric Resistance Welding
Theory Fundamentals of Resistance Welding
Resistance Welding Technology
Equipment for Resistance Welding
Tubes designed for welding, the ends must be perpendicular to the axis of the tube, without burrs. For resistance welding ends with suitable blanks obtained after cutting lathes, machining truboreznyh, saw a pendulum, followed by removing the burr drill with a diameter equal to the inner diameter of the pipe. Stripping of blank surfaces from dirt and rust is not required. The process of developing resistance welding technology is practically reduced to the choice of rational parameters of heat and precipitation, to ensure the achievement of equal strength of welded joints with the base metal, and the absence of defects in the welded joint. The required quality of welded joints is obtained by squeezing heated uniformly over the cross section edge products. The uniformity of heating is achieved by selecting the optimum welding conditions. Satisfactory formation of the joint can be obtained for different values of welding current and the duration of heating. Each diameter of the pipe corresponds to a range of welding currents within which ensured the formation of a satisfactory joint. The essential quality of welding has vliyanie.na current density in the product. At a current density of less than 0.5 A/mm2 high quality welds can be achieved in case of mechanical precipitation only when accumulated at the ends of the welded metal parts of the product has already begun to flow, ie, after the appearance of flowing liquid metal layer. At the same time to ensure the stability of the welding process is necessary to maintain the clearance between the workpiece, which can only be achieved by using tracking systems. At a current density of more than 0.5 A/mm2 mechanical sediment can be carried out in the presence of liquid products at the ends of a metal film without the appearance of flowing layer. This allows the heating of pipe ends at fixed relative to each other parts of the welded products, reduces the amount of planted metal, ie, reduces the magnitude of the internal and external burrs. Due to the fact that the heating is carried out at the fixed parts of the product, it becomes possible to simplify the design of the equipment by eliminating the complex tracking systems. If the power supply is not limited to, seek the upper limit of the welding current. Given a pre-rational power supply is the most efficient use of its power. On the uniformity of heating of the ends of the perimeter of the product significantly affects the rate of displacement of the arc. found that in the final stage of heating may be a local increase in the gap, the so-called digging. In the metal, where the digging occurred, a zone of low strength weld, or even lack of adhesion compounds. Cause of tearing is, apparently, the appearance of liquid metal drops, the speed of movement is much smaller than the velocity of the arc. Due to the speed difference between having a delay in the movement of the arc, leading to local melting of the ends and release of molten metal from the joint. One way of wresting control is a periodic change in the direction of rotation of the arc (reverse), which makes it possible for some time to disperse the liquid metal on the edges, not allowing him to collect in one place. However, reversal, especially in high-power modes, is malopodhodyaschim and could be hard to remedy. It was established experimentally that the combination of current density in the product of more than 0.5 A/mm2 arc moving with velocities of the order of 100-150 m / sec can eliminate digging, and to provide uniform heating of the edges. Based on this value is determined by the radial induction in the gap and magnetizing force excitation coils. Defining the parameters of the excitation coils (the number of turns, wire cross-section and current) are made on the basis of structural considerations and the way power coils (whether or arc by successive inclusion in the welding circuit). The magnitude of the specific efforts of precipitation during welding technology slightly higher compared to the contact welding, and is 8-10 kg/mm2 for mild steel. The optimal value of the installation of the gap between the welded parts of the products practically does not depend on the size of the welded products. For example, for pipes up to 100mm - the optimum size of this gap is 2 mm, and for pipe diameters from 100 mm to 300 mm -2,5-3. Deviations from the optimal size of the gap as to decrease (to 1.5 mm for pipe diameters up to 100 mm and 2 mm for pipe diameters 100 - 300 mm) and upward (up to 2.5 mm for pipe diameters up to 100 mm to 3.5 mm for pipe diameters of 100-300 mm) can lead to a breach of the stability of motion of the arc. Summary of welding modes, providing a satisfactory quality of welded joints in the fixed parts of the product in the process of heating, for pipe diameter 17-114mm of steel St20 STZ-listed in the table.
| The diameter of the pipe, mm | Wall thickness, mm | Welding current, A | Magnetizing force of the coil, and in- | The voltage on the arc, in | Duration of heating, s | Effort precipitation, kg |
| 17 | 2 | 200 | 1200 | 25-26 | 1.0 | 900 |
| 26.8 | 2.8 | 260 | 1400 | 25-26 | 1.8 | 1800 |
| 32 | 3.5 | 350 | 2400 | 25-26 | 2.0 | 2500 |
| 43.5 | 3.5 | 400 | 3000 | 26-27 | 2.3 | 3600 |
| 57 | 3 | 550 | 3600 | 26-27 | 4.2 | 4600 |
| 89 | 4 | 750 | 4500 | 27-29 | 5.5 | 8500 |
| 114 | 5 | 950 | 6000 | 28-30 | 9.0 | 15000 |
Electric Resistance Welding
Theory Fundamentals of Resistance Welding
Resistance Welding Technology
Equipment for Resistance Welding
10:03 PM
Theory Fundamentals of Resistance Welding
The method of resistance welding is based on the pre-heat the edges of welded parts of the product arc, rotating in a magnetic field, followed by mechanical compression of the (draft).
Scheme of resistance welding is shown in the example of pipe welding (Fig. 1). The two pipes to be welded (1-1 '), and coils of electromagnets (2-2') are arranged coaxially. Pipes connected to the welding power source (one of the welded pipe is the cathode, the other - the anode). Electromagnet coils generate magnetic fluxes directed along the tube axis towards each other. As a result, the gap between the tubes, the magnetic field has a radial component. The interaction of the arc current I and the radial component of the magnetic field strength Bp created Fg, resulting in an arc motion. This force, whose direction is perpendicular to the direction of current in the arc and the direction of the magnetic field causes the arc to move along the surface at the ends, reaching several tens of meters per second. Repeated traversal arc butt weld pipe formation occurs almost simultaneously along the entire perimeter. In the observation of the rotating arc is a continuous ring of glowing plasma. Upon reaching the welding temperature at the ends is compression (settlement) of pipes, just as is done in resistance welding. When moving in a magnetic field, the arc is influenced by various forces acting on the arc column and the active spots. These forces can be divided into the driving forces and resistance forces. The driving forces are due to the interaction of arc current with the radial component of the magnetic field. Doug can be regarded approximately as the current-carrying conductor placed in a magnetic field. On it the force Fg, defined by Ampere's law Fg = B1Il, where B1 is the component of the magnetic field perpendicular to the polar current; I - current in a conductor; L - the length of the conductor. In the case of axial and radial arc of the magnetic field strength at each moment of Fg Time is tangential to the circumference of the pipe and tends to move at the ends of the arc tube. to resistance forces include aerodynamic drag force F1, the friction flow of gases entrained arc F2 on the walls of the gap, which is a narrow slit, and the force F3, opposing the movement of the active spots of the arc.
Force of aerodynamic resistance depends on the velocity of the arc and the magnetic field. The friction force depends on the gas flow velocity of the arc, as well as the size and geometry of the gap. Force opposing movement of the active spots of the arc depends on the electrode material, shape, condition and temperature of their surfaces. for rotating arc is characterized by three stages of the arc during the whole period of heating the ends of articles (Figure 2). One of the distinguishing features of each of these stages is the nature of the change speed of the arc. Stage I - acceleration and rotation of the arc with increasing speed, at the end of the period of the velocity reaches its maximum value. Applied to the driving force behind the arc than at this stage aimed to meet her resistance force Fg> Fl + F2 + F3. At the beginning of this period, F1 and F2 are small, because small velocity of the arc. The greatest strength of the resistance is the force Fs, which is high in the initial period due to unfavorable conditions for moving spots on the pipe ends. During the period the force F3 is significantly reduced (ends of the tubes are heated, fused microroughnesses, ionized gases arc gap). The main resistance forces are forces of aerodynamic drag and friction. The difference between the driving force Fg and the resistance forces (F1 + F2 + F3) determines the acceleration of the arc in the initial period. After the initiation of an arc is displaced to the inner surface of the pipe due to the fact that there is a significant gap in the magnetic field gradient. As the heated ends of the magnetic field gradient is reduced and the arc is part of the gap. Settling time, maximum speed, ie, the duration of stage I depends on the induction in the gap and the magnitude of welding current. Stage II - the steady motion of the arc with the maximum speed is the most time-consuming. Its duration is characterized by the time required for the appearance at the ends of the film of liquid metal. At this stage, the driving force is balanced by the forces of resistance. Fg = F1 + F2 + F3. During the second stage of induction in the gap is reduced, which reduces the driving force. However, the rate of displacement of the arc remains nearly constant, since a simultaneous decrease in the friction force F3. In Fig. 3 and 4 shows the variation curves of maximum speed, depending on the arc welding current and the radial induction in the gap, taken when welding pipes with a diameter of 27 mm. From these curves it is clear that at this stage, the main parameter determining the rate of displacement of the arc, is the magnitude of the radial induction in the gap. Stage III - the rotation of the arc of a variable rate, observed during heating above the melting point edge. Almost the entire surface of the ends of welded products covered with a film of liquid metal. Applied to the driving force behind the arc is less than the resistance: FgSila Fg continues to fall, as due to the increase of the gap decreases the induction of it. Force of aerodynamic resistance and friction flow entrained gases are also reduced. The power of active resistance to movement of sunspots varies unstable, its mean value increases. This is due to the formation of bridges of molten metal ejected in the form of sparks, which leads to fluctuations in the velocity of the arc. Connections made by resistance welding have the same structure as that obtained by other methods, with application of pressure, for example, butt welding fusion. However, there are a number of structural features considered by the example of steel pipe welding St20. Most of the compounds of the seam is observed bright streak decarburized. All joints in the form and the presence of light strips can be divided into three groups:
See also:
Electric Resistance Welding
Theory Fundamentals of Resistance Welding
Resistance Welding Technology
Equipment for Resistance Welding
Scheme of resistance welding is shown in the example of pipe welding (Fig. 1). The two pipes to be welded (1-1 '), and coils of electromagnets (2-2') are arranged coaxially. Pipes connected to the welding power source (one of the welded pipe is the cathode, the other - the anode). Electromagnet coils generate magnetic fluxes directed along the tube axis towards each other. As a result, the gap between the tubes, the magnetic field has a radial component. The interaction of the arc current I and the radial component of the magnetic field strength Bp created Fg, resulting in an arc motion. This force, whose direction is perpendicular to the direction of current in the arc and the direction of the magnetic field causes the arc to move along the surface at the ends, reaching several tens of meters per second. Repeated traversal arc butt weld pipe formation occurs almost simultaneously along the entire perimeter. In the observation of the rotating arc is a continuous ring of glowing plasma. Upon reaching the welding temperature at the ends is compression (settlement) of pipes, just as is done in resistance welding. When moving in a magnetic field, the arc is influenced by various forces acting on the arc column and the active spots. These forces can be divided into the driving forces and resistance forces. The driving forces are due to the interaction of arc current with the radial component of the magnetic field. Doug can be regarded approximately as the current-carrying conductor placed in a magnetic field. On it the force Fg, defined by Ampere's law Fg = B1Il, where B1 is the component of the magnetic field perpendicular to the polar current; I - current in a conductor; L - the length of the conductor. In the case of axial and radial arc of the magnetic field strength at each moment of Fg Time is tangential to the circumference of the pipe and tends to move at the ends of the arc tube. to resistance forces include aerodynamic drag force F1, the friction flow of gases entrained arc F2 on the walls of the gap, which is a narrow slit, and the force F3, opposing the movement of the active spots of the arc.
Force of aerodynamic resistance depends on the velocity of the arc and the magnetic field. The friction force depends on the gas flow velocity of the arc, as well as the size and geometry of the gap. Force opposing movement of the active spots of the arc depends on the electrode material, shape, condition and temperature of their surfaces. for rotating arc is characterized by three stages of the arc during the whole period of heating the ends of articles (Figure 2). One of the distinguishing features of each of these stages is the nature of the change speed of the arc. Stage I - acceleration and rotation of the arc with increasing speed, at the end of the period of the velocity reaches its maximum value. Applied to the driving force behind the arc than at this stage aimed to meet her resistance force Fg> Fl + F2 + F3. At the beginning of this period, F1 and F2 are small, because small velocity of the arc. The greatest strength of the resistance is the force Fs, which is high in the initial period due to unfavorable conditions for moving spots on the pipe ends. During the period the force F3 is significantly reduced (ends of the tubes are heated, fused microroughnesses, ionized gases arc gap). The main resistance forces are forces of aerodynamic drag and friction. The difference between the driving force Fg and the resistance forces (F1 + F2 + F3) determines the acceleration of the arc in the initial period. After the initiation of an arc is displaced to the inner surface of the pipe due to the fact that there is a significant gap in the magnetic field gradient. As the heated ends of the magnetic field gradient is reduced and the arc is part of the gap. Settling time, maximum speed, ie, the duration of stage I depends on the induction in the gap and the magnitude of welding current. Stage II - the steady motion of the arc with the maximum speed is the most time-consuming. Its duration is characterized by the time required for the appearance at the ends of the film of liquid metal. At this stage, the driving force is balanced by the forces of resistance. Fg = F1 + F2 + F3. During the second stage of induction in the gap is reduced, which reduces the driving force. However, the rate of displacement of the arc remains nearly constant, since a simultaneous decrease in the friction force F3. In Fig. 3 and 4 shows the variation curves of maximum speed, depending on the arc welding current and the radial induction in the gap, taken when welding pipes with a diameter of 27 mm. From these curves it is clear that at this stage, the main parameter determining the rate of displacement of the arc, is the magnitude of the radial induction in the gap. Stage III - the rotation of the arc of a variable rate, observed during heating above the melting point edge. Almost the entire surface of the ends of welded products covered with a film of liquid metal. Applied to the driving force behind the arc is less than the resistance: FgSila Fg continues to fall, as due to the increase of the gap decreases the induction of it. Force of aerodynamic resistance and friction flow entrained gases are also reduced. The power of active resistance to movement of sunspots varies unstable, its mean value increases. This is due to the formation of bridges of molten metal ejected in the form of sparks, which leads to fluctuations in the velocity of the arc. Connections made by resistance welding have the same structure as that obtained by other methods, with application of pressure, for example, butt welding fusion. However, there are a number of structural features considered by the example of steel pipe welding St20. Most of the compounds of the seam is observed bright streak decarburized. All joints in the form and the presence of light strips can be divided into three groups:
- joints without light strip;
- joints with white stripe, with blurred boundaries;
- joints with white stripe, which has sharply defined borders.
See also:
Electric Resistance Welding
Theory Fundamentals of Resistance Welding
Resistance Welding Technology
Equipment for Resistance Welding
2:20 AM
Welding of Titanium Articles
Several articles on the welding of titanium
Heat Treatment of Welded Joints of Titanium Alloys
In short, the heat treatment.
Annealing of Titanium Welded Joints
on weld annealing
Hardening Heat Treatment of Titanium Welded Joints
hardening heat treatment of welded joints of titanium and alloys.
Special Modes of Hardening Heat Treatment of Welded Structures
welded structures made of thermally hardened titanium alloys presents numerous technical difficulties.
Effect of Welding on the Structure and Properties of Different Zones of the Welded Joint
introductory article on the subject of welding
Structure and Properties of Heat Affected Zone
how to change the structure heat affected zone (HAZ)
Structure and Properties of Welded Joints
weld structure when welding titanium
Properties and Structure of Welded Joints of Industrial Titanium Alloys
presented data on the effect of heat treatment and prolonged heating of the operational structure and properties of welded joints.
Welding of Titanium
Heat Treatment of Welded Joints of Titanium Alloys
In short, the heat treatment.
Annealing of Titanium Welded Joints
on weld annealing
Hardening Heat Treatment of Titanium Welded Joints
hardening heat treatment of welded joints of titanium and alloys.
Special Modes of Hardening Heat Treatment of Welded Structures
welded structures made of thermally hardened titanium alloys presents numerous technical difficulties.
Effect of Welding on the Structure and Properties of Different Zones of the Welded Joint
introductory article on the subject of welding
Structure and Properties of Heat Affected Zone
how to change the structure heat affected zone (HAZ)
Structure and Properties of Welded Joints
weld structure when welding titanium
Properties and Structure of Welded Joints of Industrial Titanium Alloys
presented data on the effect of heat treatment and prolonged heating of the operational structure and properties of welded joints.
Welding of Titanium