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 joint of the steel bar to a plastic state and then cut off the power supply, and then heat it again to achieve a plastic connection. This welding process is easy to produce oxidation and slag inclusions at the joints, and requires the cross-section of the steel bars to be smooth and smooth.
Flash Butt Welding Flash butt welding refers to the ejection of molten metal particles from the end joints of rebar during the welding process, presenting sparks (ie, flashes). When the molten metal is sprayed, it also brings out oxides and slag inclusions, so that the quality of the butt welded joint is good, so it is widely used, especially for the butt joint of low carbon steel and low alloy steel.
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. Rotate the adjusting screw so that the joystick is at the left limit, the gap between the jaws should be the difference between the total protruding length of the two weldments and the amount of extrusion. When the joystick is at the right limit, the distance between the jaws should be the total extension length of the two weldments plus 2~3mm, which is the original position before welding.
Adjust the short-circuit limit switch so that it can automatically cut off the power supply when the welding ends (reaches the predetermined extrusion amount).
According to the shape of the weldment, adjust the jaws so that the two jaws are at the same level, and then clamp the weldment.
In order to prevent the instantaneous overheating of the weldment, the adjustment stages should be increased successively during the trial welding, and the appropriate secondary voltage should be selected. In flash butt welding, a higher secondary voltage should be used.
In order to avoid overheating of parts during welding, the cooling water valve must be opened before welding can be performed. In order to facilitate inspection, there is a funnel in front of the left side of the welding machine, which can directly observe the water flow, so as to check whether there is cooling water flowing through the welding machine.
3. Operation points of steel butt welding machine
Butt welding machine operators must undergo professional training, be familiar with the structure, performance, and operating procedures of the butt welding machine, and master the knowledge of process parameter selection, quality inspection specifications, etc.
Before operation, check whether the various mechanisms of the welding machine are sensitive and reliable, whether the electrical system is safe, whether there is water leakage in the cooling water pump system, and whether each lubricating part is well oiled, etc.
Butt welding of steel bars exceeding the specified diameter is strictly prohibited. Butt welding of main steel bars must be welded first and then cold drawn. In order to ensure the welding quality, cleaning, rust removal and correction should be carried out within the range of about 150mm of the felt tip.
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.
The butt welding machine should be parked in a clean, dry and ventilated place. The butt welding machine used on site should be equipped with a shed that is rain-proof, moisture-proof and sun-proof, and equipped with fire-fighting equipment. No flammable materials should be stacked within the welding range.
The butt welding machine should be equipped with a special wiring switch and installed in the switch box, and the capacity of the fuse should be 1.5 times the capacity of the machine. The grounding of the welding machine shell must be good.
The post-weld appearance inspection shall show that the steel bar joints shall be properly upset, and the surface shall be free of cracks and obvious burns. The crankshaft of the joint axis shall not be greater than 6°, the offset shall not be greater than 1/10 of the diameter of the steel bar, and shall not be greater than 2mm.
After the operation, the site should be cleaned up, the fire should be eliminated, and the water in the cooling pipeline should be blown out with compressed air in winter, and the power supply should be cut off.