Factors that cause weld quality failures in used round tube forming machines include ①lap welding, ②cycle lap welding, ③opening, and ④bathholes. The following is an introduction to the cause of weld quality failure-open seam.

Seam refers to the phenomenon that the welds are not bonded together. The length of the seam is generally more than a few centimeters or even longer. The main reasons for the seam formed in the used round tube forming machines are as follows:

(1) The hole type is worn out. With the wear of the squeeze roller pass, the size of the pass (R) gradually increases. When using hot-rolled steel strip as the raw material for welded pipes, when the width of the steel strip has a negative deviation or slightly stretched steel, the welding seam will have quality problems. The lighter one will cause the trachoma tube and no internal welding ribs, and the heavy one is the open seam pipe. The production. Therefore, it is necessary to constantly check the internal burr of the welded pipe, increase the squeeze amount of the squeeze roller, or replace with a new pass in time.

(2) The bearing is damaged. When the bearing of the squeeze roller is only slightly damaged, the welding seam quality problems such as sand hole tube and lap welded pipe will occur. The seam becomes a full-open shape, accompanied by other quality accidents. At this time, we can also observe the squeeze roller with bearing damage, and the swing amplitude will become larger as the degree of bearing damage increases.

(3) Magnetic rod. The magnetic bar will form a magnetic field during the tube blank welding process, and the high-frequency current can be highly concentrated in the "ⅴ"-shaped area of ​​the weld seam, so that the weld seam can reach a high temperature point in a very short time. If there is no magnetic rod in the tube, it will have a great influence on the proximity effect and skin effect of the high-frequency current. The most obvious feature is that the welding seam is black and red, there is no splashing spark, and the welding seam is fully open. Sometimes even if it is welded, it is a false welding, and there will be a crackling sound when the pipe is sizing. If the magnet bar fails or the installation position is not appropriate, the welded pipe will burst, even if it does not crack, its strength is very low. At this time, the welding seam is generally yellow or light blue due to insufficient hot spot temperature.

(4) Material. Due to the chemical composition of the raw materials, although the welding process is relatively normal, the welding seam will still crack. Sometimes the pipe cracks during the sizing, accompanied by the sound of welding seam cracking. The color of the weld at this time is relatively blue, indicating that the temperature is still normal. Sometimes we can see that the crack of the weld deviates from the center of the weld. This is to glue the edges of the base material down to form irregular cracks. This phenomenon is purely embrittlement caused by the chemical composition of the raw material.

Due to the above 4 factors, the quality of the welding seam in the used round tube forming machines is caused by seam opening. When the welded pipe is made, it is necessary to check whether the used round tube forming machines has these problems.