When the used ERW tube mills is used to make welded pipes, the judgement of the qualified quality of the welded pipe depends on the control of the squeeze roller, so the control of the squeeze roller is very important. There are many ways to control the squeeze roller, and "two on one side" is one of the squeeze roller methods.

In the "two on one side" three-roller extrusion method, the top roller is equivalent to a short-circuit or current bypass device set on the extrusion weld. The current short circuit or current bypass may have different top roller diameters for different designs and welded pipe diameters.

The diameter of the top roller is different, and the position of the short-circuit point is also different. The larger the diameter of the top roller, the farther away from the squeeze point and the advancement of the short-circuit point, that is, the more the closing point of the steel strip is advanced, the more the current is bypassed. In the early days, the most typical phenomenon is that the top roll heats up violently and has a very short service life. The grooves of the roll are cracked, and a lot of water is needed for cooling during use.

The smaller the top roller, the closer the short-circuit bypass point is to the welding extrusion point, and overlap with the pre-healing point of the steel strip edge, the smaller the bypass effect on the current, but due to the structure and heating limit the size reduction, The used ERW tube mills actually has the same diameter of the top roll as the diameter of the side vertical roll. The influence of the top roller on the welding efficiency is usually not less than 10%, and the loss can reach 25% when it is high, and the measured average value is 15% to 18%. And the smaller the pipe diameter, the thicker the wall thickness, the greater the efficiency loss of using this structure.

With a 10% loss, the production of 76X3.5mm steel pipes, the same production time and welding power, the annual loss is about 500,000, and the loss of one 50 unit investment a year.

The steel strip caused by the top roller is short-circuited in advance and bypasses the high-frequency current at the edge of the steel strip, causing excessive heating of the top roller, forming transverse cracks, causing irregular indentations on the surface of the steel pipe, and reducing the life of the squeeze roller. (As shown below)

The steel strip caused by the top roll is short-circuited in advance and bypasses the side current of the steel strip, which causes the top roll to overheat. A large amount of water spray is needed to cool down during production. However, the high-frequency current heating cannot reduce the temperature of the roll only by cooling the surface. At the same time, the roll is repeatedly heated-quenched-heated-quenched, and the roll performance is more difficult to guarantee. (The following figure)

Another potential hazard brought by the "two on one side" three-roller extrusion method is the stricter requirements for processing accuracy, which has been ignored or ignored by everyone in the past.

(1) If the center line of the upper roller moves back by d1, it will cause the top roller to be squeezed microscopically after the welding side is squeezed, and the streamline bends or rows into the shoulders, or the left and right metallography can be seen on the metallography. Asymmetry. Normal testing methods such as flaw detection, longitudinal flattening, impact, hydraulic pressure, etc. can not find the problem. The only thing is that weld cracks will occur during horizontal flattening.

(2) If the top roller moves forward by d2, as mentioned above, it will cause the weld seam to close earlier and then squeeze sideways, which will result in high energy usage and low welding efficiency.

Asymmetric metallographic structure

The above is the method to adjust the squeeze roll of the used ERW tube mills "on one side and two". If you need it, you can pay attention to the method in the next issue. At the same time, if you need used welded pipe equipments, please contact us. You only need to inform us of your pipe-making needs, and our company will provide you with used welded pipe equipments that really suits your needs.