High frequency welding mainly uses the skin effect and proximity effect of high frequency current to make the current highly concentrated on the side to be welded, so that it can be heated to the welding temperature (1130-1350°C) within one hundredth of a second , And then pressure welding under the action of the squeeze roller.
This welding method has a series of advantages: the heat-affected zone of the weld is small and the heating speed is fast, so the welding speed and the quality of the weld can be greatly improved, and the strip steel without pickling, shot blasting and trimming can be used as the blank. Welding alloy steel, high alloy steel and non-ferrous metal pipes, greatly reducing unit power consumption. A set of welding equipment can produce various metal welded pipes. For different metals, just change the welding power and welding speed accordingly.
High-frequency welding methods can be divided into conduction feeding (contact welding) and induction feeding (induction welding) according to the different ways of feeding the welded parts.
When using conductive feed welding, the high frequency current is transmitted to the tube blank 1 by means of two contact heads (electrodes) 2 and 3. The welding current flows along both sides of the groove of the tube blank and forms a loop through the meeting point on both sides of the groove near the squeeze roller 5. The direction of the current on the grooves on both sides of the billet is opposite. Therefore, the proximity effect causes the current to concentrate on the surface of the groove. The higher the current frequency, the more the current is concentrated on the surface. The resistor 4 improves the concentration of the groove heating because it increases the inductive reactance of the current flowing around the billet.
When using this welding method, the contact head can be set at different distances (30-200 mm) from the meeting point. When the tube blank moves, the contact head can slide above or below the edge to be welded. The solution that the contact head is placed on the edge to be welded from above is the most widely used, because this solution can make the structure of the welding device simple and reliable.
In high-frequency welding, the principle of electromagnetic induction is used to make the welding workpiece cut the magnetic field lines in the magnetic field of the foot, and induce current on the surface. According to the skin effect of alternating current, the surface of the welding workpiece is rapidly heated in the form of eddy current. The advantages are:
1. Small heat loss, fast heating and high thermal efficiency;
2. The equipment is compact and easy to use;
3. The production process is cleaner than flame welding, no high temperature, and good working conditions;
4. After parameter setting, the welding is consistent, reducing human operation errors;
5. Fast welding speed;
6. Small heat affected area;
7. There is no need to remove the dirt on the surface of the welded parts, etc.;
8. It can weld a variety of metals.
Tips: ASTM A53 Gr.B is the grade in ERW high frequency welded pipe, divided into A and B grades. ASTM is only a set of specifications. ASTM steel pipe A53 A corresponds to the Chinese standard GB8163 raw material is 10# steel, and A53 B corresponds to the Chinese standard GB8163 raw material 20#.
For example: ASTM (standard) A53 (grade) gr is grade (abbreviation of grade) b (grade B)
ASTM A53 Grade B is the material under the American steel pipe standard, API 5L Gr.B is also the American standard material, A53 GR.B ERW refers to the electric resistance welded steel pipe of A53 GR.B; API 5L GR.B Welded refers to the material Welded steel pipe of API 5L GR.B.
