Views:0 Author:Site Editor Publish Time: 2021-05-31 Origin:Site
The difference between submerged arc welding and high frequency welding
1. Submerged arc welding
Submerged arc welding is a method in which the arc burns under the flux layer for welding. The welding arc burns between the welding wire and the weldment. The heat of the arc melts the base metal and flux at the end of the welding wire and near the arc. The welding wire is continuously fed in and advances along a certain trajectory. After the arc is removed, the molten pool metal solidifies A weld is formed, and the molten flux is solidified into a slag shell covering the surface of the weld. The slag protects the weld pool and weld metal, preventing the arc and the weld pool from being invaded by outside air. In addition, the slag participates in the metallurgical reaction of the molten pool, the alloy elements such as Cr and Mn in the welding wire may be burnt, and the Si, S, P, etc. of the flux enter the weld metal.
The actions of arc starting, wire feeding, wire moving and arc extinguishing of submerged arc welding are usually completed by machinery, so it is called automatic submerged arc welding. Submerged arc welding has the following advantages: ① High degree of mechanization, low requirements on the skill level of the welder; ② Large welding current, which can reduce the groove of the weldment, and high welding efficiency; ③ The flux can separate the contact between the molten metal and the air, and the protection effect Good, high weld quality; ④ It is covered with arc radiation, and the working conditions are better. The disadvantage is that it can only be welded in the flat welding position, which requires higher welding equipment and tooling.
There are generally two types of welding equipment for submerged arc welding. One is the constant-speed wire-feeding submerged arc welding machine, the wire-feeding speed is unchanged at the set speed, and the relative stability of the arc is maintained by the self-regulating effect of the arc. The other is a variable-speed wire-feeding submerged arc welding machine, which uses the arc voltage as a feedback signal and changes the wire-feeding speed through a control system to keep the arc relatively stable. In addition, in order to ensure that the welding process is in the most suitable position and the welding process is stable and reliable, submerged arc welding also requires more complicated auxiliary equipment to cooperate with the welding machine. Commonly used auxiliary equipment include: welding parts displacement equipment, welding operation machine (Ie welding machine head displacement equipment), welding fixture and welding seam forming equipment, etc.
Due to the large current and large penetration depth of submerged arc welding, the groove form and size requirements are: the thickness of the plate is less than 12mm without grooves, the thickness between 12 and 20mm can be single-sided welding, and the reverse side is cleaned for welding. Beveling is required at 20mm, but the blunt edge is required to be 5-6mm. The welding current is selected according to the diameter of the welding wire, the thickness of the weldment, and the type of flux. Due to the large welding current of submerged arc welding, burn through is prone to occur during the first layer welding. The following welding processes are often used: electrode arc welding bottom welding, permanent backing plate submerged arc welding, lock bottom butt joint submerged arc welding, flux pad Submerged arc welding.
2. High frequency welding
A welding method in which the workpiece is heated with high-frequency current and then pressure is applied to form a joint. Utilizing the principle of high-frequency current flowing concentratedly along the conductor surface and along the path with the smallest inductive reactance, the current is concentrated to heat the surface of the workpiece to be welded, and when it reaches the thermoplastic state or the partial melting state, the workpiece is pressurized to extrude the molten metal and metal Oxide forms a welded joint. The common frequency range of high frequency welding is 60～500 kHz. There are two types of high-frequency welding: high-frequency resistance welding and high-frequency induction welding.
ERW principle of high frequency welding
①High-frequency resistance welding: use rollers or contacts as electrodes to introduce high-frequency current into the workpiece, which is suitable for continuous longitudinal butt welding and spiral lap welding of pipes, and welding of boiler fin tubes and heat exchanger spiral fins. The outer diameter of the weldable pipe is 1200 mm, the wall thickness is 16 mm, the thickness of the I-beam web can be welded to 9.5 mm, and the productivity is very high.
②High-frequency induction welding: Heat the workpiece with induction coils, and can weld small-diameter tubes with an outer diameter of 9 mm and thin-walled tubes with a wall thickness of 1 mm. It is often used for longitudinal seam welding of small and medium diameter steel pipes and brass pipes, and can also be used for circumferential seam welding, but the power loss is greater than that of high-frequency resistance welding. The main parameters that affect the quality of high-frequency welding are the frequency and power of the high-frequency power supply, the forming angle of the workpiece, the squeezing force, the distance between the electrode (or induction coil) and the squeeze roller, and the welding speed. The main equipment includes high-frequency power supply, workpiece forming equipment and extrusion machinery. High-frequency welding has stable quality, high productivity and low cost. It is suitable for high-efficiency automatic production lines and is an advanced method for producing seamed pipes.
Submerged arc welding has high quality welds and can be applied to load-bearing and pressure-bearing projects; such as high-rise three-dimensional structure columns, large gymnasium plants, oil and gas pipelines, and mechanical processing.
The mechanical properties of high-frequency welding seams are worse than that of raw materials, and they are often used in low-pressure fluid pipelines, non-load-bearing grid structure columns, etc.