Butt Seam Welding Machines for SteelStrip and Nonferrous Metals

The engineering company ENCE GmbH offers butt seam welding machines for coiled strip of stainless, alloyed, mild, carbon steels, as well as aluminum, titanium and other nonferrous metals and special alloys for the process of cold rolling of coiled steel, the steel strip hot galvanizing line, lacquer or polymeric coating line, steel strip pickling line, coiled metal heat treatment line, and for forming lines and electric-weld pipe mills.

Butt seam welding machines are used at iron and steel enterprises in technological processes of continuous coiled metal when it is required to continuously feed the strip from the coils in the entry into the line or to butt the strip when cutting off a reject part of the treated strip.

Butt seam welding machines offered by the ENCE GmbH engineering company provide a number of advantages:

• Minimal waste
• High productivity with a minimal pause per welding operation
• Reduced power consumption
• High seam quality with a bead no more than 10% and preserving strength parameters of the main strip
• Fully automated operation cycle with a possibility of manual operation
• Employment of different methods to butt weld the strip:
  • Flash welding
  • Seam welding
  • Electric arc welding

As an example, ENCE GmbH engineering company suggests considering a butt seam welding machine for seam welding of a strip of mild and carbon steels.

The machine for seam welding comprises the following equipment:

• A. System of strip centering at the entry:
  • 1. Loop roller at the entry
  • 2. Strip bench support at the entry
  • 3. Four-point strip guides at the entry
  • 4. Strip end detection sensor

• B. Welding machine:
  • 1. S-shape frame with the main drive
    • a. System of heads with discs
    • b. Straightening rollers
    • c. Double cut shears
    • d. Automated system of scrap removal
    • e. Punch
    • f. Welding equipment
    • g. Current synchronization system
  • 2. Welding clamps at the entry
  • 3. Welding clamps at the exit
  • 4. Strip length regulation mechanism

• C. Centering system at the exit:
  • 1. 4-point strip guides at the exit
  • 2. Loop roller at the exit

• D. Controls
  • 1. Operator’s control board
  • 2. Main control desk
  • 3. Operating valves, pipes and wiring
  • 4. Independent hydraulic station

• E. Independent recovery block

• F. Closed loop cooling system

• G. Shears

• H. Lubricating system

• I. Special tools

• J. Butt seam welding machine automation system
  • 1. Manual control
  • 2. Automatic mode

The machine for seam welding is mounted on the main frame, and its sub-frames are directly fixed to the line foundation.

The system automatically centers the end of the entering strip in the welding machine. Together with the centering system at the exit, it provides highly precise centering of the new roll end.

The loop roller is located on the entry side of the welding machine and is designed to support and correctly center the strip. The roller is fixed by hinge joints and is actuated by the air cylinder. It is automatically raised when the end of a new strip is fed to the machine, the control signal is sent via the strip end detection sensor. The roller is installed on the support and has a non-marking coating.

The strip bench support provides an easier feed of the ends of the previous and new coils into the welding machine. A material that makes no marks on the strip surface is used to contact with the strip.

Strip guides at the entry are designed to center the end of a new coil in the welding machine. The unit comprises a four-plate guide: two plates on the operator’s side and two plates on the motor’s side. The plates are moved towards the strip by the common drive of the right-hand and left-hand rotation and by the hydraulic motor. The unit uses plates as the coiled strip doesn’t move when centered. The guide unit is triggered automatically using photocells to determine the strip edges when the end of the new coil is located in the welding machine.

Due to the precise four-point system for centering the new coil end no center shift occurs during the strip end welding.

Strip end sensor is used to detect the beginning and the end of strips. It sends a signal to the main control unit in the line to stop both ends in the cutting zone of the welding machine.

The frame is a heavy steel structure that is designed to support and guide the travelling carriage of the S-shape frame. The carriage of the S-shape frame — a big steel S-shape structure — is an integral part of the butt seam welding machine. S-shape frame serves as a support for the double cut shears, the conveyor to remove scrap, the punch, welding discs, straightening rollers, the wiring and welding transformer. The ball screw connected through the mechanic gearbox to the variable speed motor drives the S-shape fame. The mounting frame hosts, too, welding clamps and the strip centering unit.

Two welding heads with discs located over and under the strip. The welding heads are filled with non-conductive oil.

Current from the bar to the welding head is supplied by a flexible cable. The flexible cable prevents any torque on the welding head and is 15% more effective than a laminated cable.

The current runs through the silver-plated conductor. This structure provides a uniform current along the entire conductor surface. Each welding disс is actuated from the pneumatic motor which ensures the disc turning before the overlap welding starts and prevents possible problems during the welding process. The welding head is provided with internal water cooling.

The only part detachable when changing a welding disc is the nut that releases the flange and the welding disc (changing time is less than 60 seconds).

The welding disc diameter may vary due to recovery required during the normal operation. To adjust for the variable disc diameter, the lower welding disc is manually raised using the manual flywheel to the lower limit of the lower clamp’s upper part. The position of the lower welding disc is adjusted with the beam of the laser installed on the main frame of the butt seam welding machine before the welding apparatus. The upper welding disc is lowered on the strip using the pneumatic cylinder on the air proportional pressure valve.

The welding head is guided by a square shaft with non-conductive bearings and low friction bushings. This system supports continuous pressure which provides extremely low welding pressure. In conjunction with direct current welding and three phase power supply it provides high seam quality, high welding rate and welding strips with minimum thickness.

Straightening rollers located after the welding heads are actuated during a welding cycle. The height of the lower straightening roller is manually adjusted. The upper straightening roller is driven by the pneumatic cylinder. The rollers’ straightening force is adjusted with the air proportional pressure valve. Welding and straightening are carried out simultaneously which reduces the entire machine cycle. Furthermore, it provides uniform straightening as the relation of welding/straightening is uniform along the entire strip width.

Shears comprise 1 hydraulic cylinder and mechanical drive system for the upper section, and a pneumatic cylinder with a guide to raise the lower blades. When the upper blade driving system is operated the lower shears are fixed in the upper position. Upper and lower blades move towards each other during a cut. All blades are easily removed and replaced when the S-shape frame is idling. During a normal operation of the line the upper and lower blades do not contact with the strip. An additional manual lock prevents the upper shears from falling down during maintenance. The distance between the two lower blades of the shears is about 100 mm.

The two waste ends of the strip during cutting go onto the conveyor where they are transferred to the bin during each process of welding.

The punch is an integral part of the upper shears unit. The punch (a hydraulic cylinder and a wedge) may be switched on and off. The location of the punch is about 90 mm from the output side of welding.

A welding transformer with diode rectifiers is installed on the rear side of the S-shape frame. The transformer is protected from overheating and provided with an internal loop of water cooling. Direct current of welding is transformed from the beginning to the end of the welding operation. The use of a three-phase invertor provides a more balanced loading on input power supply. The invertor is water cooled and mounted on the butt seam welding machine but it does not move with the S-shape frame.

As welding is carried out with direct current magnetism occurs near the shears. It may result in attracting light metal chips to the shear blades after a continuous operation. To remove this problem, the conductive bars near the transformer joint are so designed that they may be switched over to invert the current direction. It prevents magnetizing near the shears and excludes the necessity to use special magnets under the conveyor to remove metal chips.

The system of current synchronization switches welding current on when the welding discs come into contact with the strip. The same system switches the current off when the disc withdraws from the strip, regardless the strip position in the butt seam welding machine. Due to this system there may be any difference of the strip width (between entry and output). Both ends of the coils are detected separately which provides detection of the exact moments to begin and finish welding. Photocells are used to detect the strip end.

Clamps at the entry hold the strip end and continuously feed it to the clamps at the exit. The pace length is adjusted with a servomechanism, a position pickup and a ball screw, one on the driver’s side and one on the operator’s side. These devices control the contacting overlap of two strips during welding / straightening. Adjustment is carried out automatically. Independent settings of the both sides (operator’s side and driver’s side) allow creating V-overlap.

The clamp is provided with the possibility to adjust the carriage stroke which is required to align the strip ends before welding. It allows aligning both strip ends when strips of equal width are welded.

Clamps at the exit have a similar construction as the clamps at the entry, however, with no indexing and carriage adjustment. The clamp at the exit can turn. Turning or tilting allows raising the strip end so that the clamps at the entry can reach the position of welding. When the clamp at the entry is in the position of welding the clamp at the exit is tilted to overlap the strip ends. This possibility ensures the correct strip overlap without destroying the edge during this operation.

The welding clamp at the exit is automatically adjusted before closing, depending on the strip thickness. The clamp moves to the position of cutting with a light-gage sheet, and withdraws from it with a thick-gauge plate. This increases the stroke reserve, or the distance from the strip end to cut to the clamp, which provides the functionality of welding light and thick-gage metals.

This system automatically centers the strip end at the exit in the butt seam welding machineе. It provides exact centering, just like the centering system at the entry.

The strip guide at the exit is designed to center the end of a new coil in the butt seam welding machine. The unit comprises a four-plate guide: two plates on the operator’s side and two plates on the motor’s side. The plates are moved towards the strip by the common drive of the right-hand and left-hand rotation and by the hydraulic motor. The unit uses plates as the strip in the coil doesn’t move when centered. The guide unit is triggered automatically using photocells to determine the strip edges when the end of the new coil stopped in the butt seam welding machine.

Due to the precise four-point system for centering the new coil end no center shift occurs during the strip end welding.

The roller of loop-mill rolling is located on the exit side of the welding machine and is designed to correctly center the end of the welded coil through making it slack. The unit is fixed by hinge joints and is actuated by the cylinder. It is automatically raised when the previous coil is in the correct position. The roller is mounted on the support and has a non-marking coating.

The main operator’s control board is integrated in the welding apparatus. The station accommodates all devices required to control the welding machine. It also provides space for external devices to control the entire line. The line controls are integrated into the butt seam welding machine and connected to terminal boxes of the welding apparatus. The board comprises control buttons and indicators that entirely comply with the man-machine interface.

The second operator’s control board to manually control the equipment is located in the punch area.

The control desk is an alone standing control cabinet that is placed near the butt seam welding machine and comprises the electric equipment, or, if required, adjacent to the welding machine, on the driver’s side.

The desk comprises:

• Input/output devices
• Thyristor contactor and convertor
• Required safeguards and automatic circuit breakers
• Required reducing transformers
• Required lighting and jacks

The butt seam welding machine and the welding process are controlled via a controller. An industrial laptop computer with required software is provided, too.

All valves with hydraulic and pneumatic control are integrated into the machine. These devices are connected by the system of piping and wiring and are pre-tested.

Hydraulic pressureе is regulated by an independent hydraulic station.

This equipment is designed for recovery (cutting and subsequent profile creation) of the welding disc. It is an independent system comprising a spindle with an alternative current motor and a cutter for the disc. Welding discs are clamped by the hydraulic unit. The recovery takes about 2 minutes. The equipment may be installed near the welding machine or in the maintenance zone.

A closed loop of water cooling is provided to prevent external contacts between water and the welding machine. The cooling fluid is a freon-free water solution. The loop serves to cool both welding discs through the welding heads and the welding transformer. Control units are included in the control desk of the welding machine.

The shears are mounted on a separate base at the exit side of the butt seam welding machine. The shears are used to cut the beginning and the end of the strip to produce a straight edge and relieve the stress, as well as to remove cuttings when transferring from narrow to wide strips. The blades are designed so that they may be used with different widths of the strip, up to 280 mm. Besides, the blades may cut tangential semicircles. Cuttings automatically go onto a waste tray under the unit. The conveyor transfers them to the waste bin.

All lubrication points are connected by pipes to the front panel of the butt seam welding machine and are designed for shot or oil pump lubrication.

The following tools are provided:

• Nut driver to remove shear blades
• Cutter holder to recover welding discs independently
• Cutter to recover welding discs
• Laptop computer with necessary software ready installed.

The welding machine may be operated in the automatic or manual mode.

All functions, including welding machine settings, are manually set by the operator (by pressing a button or through the touch screen). These include all production sequences and strip positioning.

All functions of a production sequence are automatically set through the welding machine PLC (except for the carriage settings of the clamp at the entry). All welding parameters are set manually (information come to the welding machine PLC from the mane control desk of the line). This information includes the strip thickness and alloy.

Beside butt seam welding machines for steel and nonferrous metal strip ENCE GmbH engineering company supplies customers a wide range of equipment and component parts for flat rolling, hot galvanizing lines and strip polymer coating:

• Reversers
• Coilers
• Uncoilers
• Cutting lines for steel strip (including slitting and shearing lines of small capacity)
• Dividing shears
• Rolling tables
• Automated systems for detecting surface defects
• Strip stenciling units
• Coil stenciling units
• Electromagnetic grips (electrohydraulic and mechanic grippers for coils)
• Coil weighing and packing units
• Intrashop rail transport (trolley cars)

Component parts:

• Gearboxes,
• Bearing assemblies,
• Rolls made of cast iron and special steels (working and backing rolls),
• Zinc cleanup systems for rollers
• Toothed gearing
• Non-contacting systems for real-time measuring of complex profiles
• Inline pickler analyzers
• Non-contacting thickness gauges (X-ray and isotope)