What are the common faults and prevention methods of butt welding machine

Update:22 Jul 2022

Butt welders are also known as current welders or resis […]

Butt welders are also known as current welders or resistance butt welders. Using the resistance between the contact surfaces of the two workpieces, a low voltage and a large current are instantaneously passed through, so that the contact surfaces of the two butted metals are instantly heated to melt and fuse
When the welding machine is butt welding, since the end of the metal is burned in the heating, the cleaning requirements of the face are not high, but the cleaning requirements of the contact surface of the fixture and the weldment are the same as those of the resistance butt welding, so the equipment has some minor faults due to external factors. .
Common faults and preventive measures:
1. Dislocation: The reason may be that the welded parts are not aligned or inclined, the welded parts are overheated, and the discharge length is too large. The welding rigidity is not large enough. The main preventive measures are to improve the rigidity of the equipment, reduce the length of the extension and appropriate restrictions on the upsetting. The dislocation of the allowable error is generally less than 0.1mm or 0.5mm in thickness. at the same time
2. Cracks: The reason may be that under the quenching tendency of high carbon steel and low carbon steel, it can be preheated and prevented by thermal and timely annealing measures.
3. No penetration: The reason may be that the interface temperature at the top is too low, the upsetting is too small, the forging pressure and forging speed are low, and the metal inclusions are too much to cause the impermeability. Yes, use the appropriate butt welding process parameters.
4. White spot: The special defect on the weld shows a radial gray diurnal shift on the cross section. This defect is very thin and is not easy to grind in gold. It can be found in the electron microscope analysis that the white color is more sensitive to cold bending, but it is not easy to be ground. The effect of tensile strength is very small and can be eliminated with quick, comprehensive measures.
The welding machine can also be combined with other automation equipment to realize the full automation of the flash butt welding machine.
1. Butt welding process According to the working principle of the butt welding machine, the butt welding process can be divided into two types: resistance butt welding and flash butt welding:
Resistance Butt Welding Resistance butt welding is to heat the end of the reinforced joint to a plastic state and then cut off the power, and then heat it to the plastic connection. This welding process is easy in the joint part of oxidation and slag, and requires the steel part to be smooth and smooth. At the same time, welding consumes a lot of power and requires welding power, so it is rarely used.
Flash Butt Welding Butt welding means that during the welding process, from the reinforced end of the molten metal particles, sparks (i.e. flashes) are displayed. When the molten metal is sprayed, oxides and slag can also be released, so that the quality of welded joints can be widely used, especially for low carbon steel and low alloy steel butt joint, more suitable.
2. How to use The following items should be paid attention to when using the butt welding machine:
Adjust the distance between the two jaws. The jaw spacing should be the difference between the total length of the two welds and the amount of extrusion when the lever is at the left limit. When the joystick is in the correct position, the distance between the jaws should be the total length of the two welds plus 2~3mm, the original position before welding.
Adjust the short-circuit limit switch to automatically turn off the power at the end of the welding (reach the specified amount of extrusion).
Press the weld shape, adjust the jaws so that the two jaws are at the same level, and then clamp the weldment.
In order to prevent the weldment from overheating instantaneously, please try to increase the adjustment of the welding times and select the appropriate secondary voltage. In flash butt welding, it is appropriate to use a higher secondary voltage.
In order to avoid overheating of components during welding, the cooling water valve must be opened before welding. In order to facilitate inspection, a funnel is provided in front of the left side of the welding machine, so that the flow conditions can be directly observed, so that there is no cooling water flow in the welding machine.
3. Operation points of steel butt welding machine
Welder operators must receive professional training, be familiar with welding machine construction, performance, operating procedures, master the selection of process parameters, quality inspection and other specifications.
Before running, check whether the welding machine is sensitive and reliable, whether the electrical system is safe, whether the water pump system is not leaking, and whether the lubricating parts are suitable for oiling.
Welding shall not exceed the specified diameter of steel bars, and the main reinforcement butt welding must be cold drawn first. In order to ensure the welding quality, cleaning, rust prevention and correction work are carried out within the range of about 150mm of the end point.
Operators must wear tinted protective glasses and hats when working to prevent arc light from irritating the eyes and melting metal to burn the skin.