Welding use of welding machines:

1. Butt welding process

According to the working principle of welding machines, welding processes can be divided into two types: resistance welding and flash welding:
Resistance welding is the process of heating the end joints of steel bars to a plastic state, cutting off the power supply, and then heating them to achieve a plastic connection. This welding process is prone to oxidation and slag inclusion at the joint, and requires the cross-section of the steel bar to be smooth and flat. At the same time, it consumes a lot of electricity during welding and requires a high welding machine power, so it is rarely used.
Flash welding refers to the process of spraying molten metal particles from the joint of the steel bar end during welding, presenting sparks (i.e. flashes). At the same time as molten metal is sprayed out, oxides and slag inclusions are also carried out, making the quality of the welded joint good. Therefore, it is widely used, especially for the docking of low carbon steel and low alloy steel, which is more suitable.

2. Usage

When using a butt welding machine, the following precautions should be taken:
Adjust the distance between the two jaws. When turning the adjustment screw to position the control lever at the left limit, the distance between the jaws should be the difference between the total extension length of the two welded parts and the amount of compression. When the control lever is at the right limit, the distance between the jaws should be the total extension length of the two welded parts plus 2-3mm, at the original position before welding.
Adjust the short-circuit limit switch to automatically cut off the power supply when the welding is completed (reaching the predetermined extrusion amount).
Adjust the jaws according to the shape of the weldment, so that the two jaws are at the same level, and then clamp the weldment.
To prevent instantaneous overheating of the welded part, the adjustment level should be gradually increased during the trial welding, and an appropriate secondary voltage should be selected. When flash welding, it is advisable to use a higher secondary voltage.
To avoid overheating of components during welding, it is necessary to open the cooling water valve and allow water to flow before welding can be carried out. For the convenience of inspection, there is a funnel on the left front of the welding machine, which can directly observe the water flow situation, so as to check whether there is cooling water flowing inside the welding machine.

3. Key operating points of steel bar butt welding machine

Welding machine operators must undergo professional training, be familiar with the structure, performance, and operating procedures of welding machines, and master knowledge of process parameter selection, quality inspection standards, and so on.
Before operation, check whether the various mechanisms of the welding machine are sensitive and reliable, whether the electrical system is safe, whether the cooling water pump system has water leakage, and whether the lubrication parts are well lubricated.
Welding of steel bars exceeding the specified diameter is strictly prohibited. The main reinforcement must be welded first and then cold drawn. To ensure welding quality, cleaning, rust removal, and correction work should be carried out within a range of approximately 150mm from the end.
When operating, operators must wear colored protective goggles and hats to prevent arc light from irritating the eyes and molten metal from burning the skin.
Welding machines should be parked in clean, dry, and ventilated areas. Welding machines used on site should be equipped with rain proof, moisture-proof, and sun proof sheds, and equipped with fire-fighting equipment. Flammable materials should not be stacked within the welding range.
The welding machine should be equipped with a dedicated wiring switch and installed in the switch box. The capacity of the fuse should be 1.5 times the capacity of the machine. The grounding of the welding machine casing must be good.
After visual inspection after welding, the steel bar joints should be appropriately roughened, with no cracks or obvious burns on the surface. The crankshaft of the joint axis shall not exceed 6 °, and shall not exceed 1/10 of the diameter of the steel reinforcement, and shall not exceed 2mm.
After homework, the site should be cleaned up, the spark should be eliminated, and in winter, compressed air should be used to blow out the water stored in the cooling pipeline and cut off the power supply.