Although high frequency tube mill machine manufacturer makes up the bulk of welded tubes produced globally, the method is still poorly misunderstood. However, a comprehensive grasp of the technique might result in improved product yield and quality. The process is quite forgiving, which is one of its main advantages.
operating principles
The enormous rotating transformer typically used in lower frequencies electrical resistance spot welding (ERW) is substituted by a “virtual transformer” made up of the working coil (primary winding) as well as the tube on its own in the induction welder (secondary winding). Similar to a traditional transformer’s core material, a ferromagnetic core is located within the tube.
A magnetism surrounds the coil while it conducts current, and a portion of this field intersects with the open box. As a result, the outside surface of both tubes develops an electric field that induces a voltage differential from across the strip’s ends. The electromagnetic and electric fields’ interplay at induction welder frequencies might cause unexpected current flows. Since the current is constrained to only a few tenths of an inch of both surfaces due to the “skin effect,” the voltage across strip borders tends to induce the flow of electricity circumferentially.
The generated current on the outer tube’s inner surface in the reverse direction all around the interior tube’s inner surface.
Due to the near closeness of the strip’s friction between two edges from the coils to the tip of the vee, these have a meagre inductance value, and then at high frequencies, inductor rather than resistive controls how current flows. The “proximity effect” is another name for this.
This illustrates that when an applied voltage is generated across the strip’s borders, there are primarily two pathways across which current may go. The secret to using a frequency welder effectively is to reduce the wasteful bloodsucking current flowing around the inner tube’s surface and to direct this same majority of both the present along the faying edges, where it performs practical work by burning them. This is achieved by lowering the vee’s input resistance relative towards the I.D. surface.
The impeder’s purpose
Because it increases the tube’s impedance, the first tool you have is an impeder. The simplest definition of an impeder is a bar containing ferromagnetic inserted within the tube at the weld. Such materials have had the effect of increasing a circuit’s surrounding capacitance. Although the interior of the tube has very little resistance, at a higher frequency, the primary determinant of current flow is the inductor (or, more particularly, inductive reactance). Impedance is defined as the product of reactance & resistance. This describes how impeders operate in the “traditional” manner.
arrangements for weld rolls
All that the induction heater warms are the strip edges. The actual welder occurs as a result of material flow brought on by pressure from the squeeze rollers. Among the most significant obstacles facing the mill designer is this part of the tube mill. In addition to offering an extremely high level of accuracy, the weld pressures unit (also known as the weld box) must also be sturdy enough to resist being driven through with unwelded tubing. This is the only area of the mill that experiences extreme temps & thermal stress, and induction welder geometry necessitates that the rolls & supports be just as compact as feasible.
Vee Length
Vee length is influenced by coil location and, to a lesser degree, coil length because heating occurs before when the strip reaches the coil.
While coil length is often governed by the welder’s ability to match materials, coil location is typically regulated by the diameter & size of the welder roll box.
Here, two things come into play:
- Because just a minimal quantity of metal is ignited, induction welding is highly efficient. Increasing its vee length gives heat more time to travel away from the margins, using more energy and resulting in a broader heat-impacted zone.
- Depending on the respective impedances of both circuits, the amount of current flowing between the vee and the inner layer of the tube will vary. A longer eve’s greater impedance causes it to conduct more of the current energy around the tube’s interior. This is crucial when welding tiny diameter tubes since impeders have less room, reducing their efficiency.
Angle of approach
The lower the capacitance of the faying edges, more closer they are to one another. This lowers the vee’s overall impedance about the parasitic current’s route around the inner tube’s outer surface. The smallest vee angle may be employed as a restriction. Any mechanical instability, including “breathing,” will result in a higher variation in vee length when the angle is decreased, raising the weld temperature.
Levels of inducement, the voltage from across the vee may be high enough to ionise the air between the edges, resulting in arcing. However, a mechanical limit remains roughly 2-3 points for carbon steel tubes or 5-8 degrees for steel & non-ferrous materials. A frequency band helps since it lowers the voltage, but it ultimately does not assist.
Coil diameter
A coil operates most efficiently from an electric perspective when its size and length are identical. In induction tube welding, more energy is absorbed by heat diffusion because a longer coil begins to heat both strip edges farther away from the weld spot. Therefore, short locks are preferred.
A coil’s impedance may increase if it is too short, making it impossible to match the welder. The amount of power the welder can supply to the coil at one time will be limited. The coil resistance is too low and should have turns increased, or the duration should be decreased if the welder runs into an over-maximum cap before reaching maximum voltage. The impedance is just too high when a voltage cap is reached first.
The coil should be extended, or twists should be deleted.
Because stainless steel doesn’t transmit heat well, there is a propensity for the strip’s edges to overheat and for a film of molten steel to accumulate on its surface. This may be lessened through a particular wavelength. However, the same result can be obtained by relocating the impeder near the mill’s entrance end or doing away with it entirely. There is a need for more electricity. However, the growth is less than
Because ferritic stainless steels have substantially higher magnetic permeability than austenitic stainless, as well as other non-ferrous alloys used with carbon steel, this lessens the requirement for the impeder. The Joyandsonstubemill, steel tube mill manufacturers in high frequency is the well known manufacturers in India.
