The principle of high frequency welding, what is high frequency welding?

High-frequency welding refers to a welding method that uses high-frequency electric current to flow through the resistive heat generated by the contact surface of the workpiece, and applies pressure (or no pressure) to make the metal of the workpiece form a connection. High-frequency welding is not the same as resistance welding. In high-frequency welding, the welding current is only in parallel contact with the surface of the workpiece; The current in resistance welding flows perpendicular to the welding interface.

Generally, the frequency of high-frequency welding is 300 450kHz: resistance welding uses 50kHz power frequency electricity.

High-frequency welding can be divided into contact high-frequency welding and induction high-frequency welding according to the way high-frequency current generates heat in the workpiece. In contact high-frequency welding, a high-frequency electric current is transmitted to the workpiece through mechanical contact with the workpiece. In inductive high-frequency welding, a high-frequency current is generated in the workpiece through the coupling effect of the external induction coil of the workpiece.

High-frequency welding is a highly specialized welding method, which should be equipped with special equipment according to the product. High productivity, welding speed up to 30m min. It is mainly used for the welding of longitudinal seams or spiral seams when manufacturing pipes.

Principle: The principle of high-frequency welding - with the help of the skin effect of high-frequency current, the high-frequency electrical energy can be concentrated on the surface of the weldment, and the proximity effect can be used to control the position and range of the high-frequency current flow route. When a high-frequency current is required to be concentrated in a certain part of the weldment, this requirement can be achieved as long as the conductor and the weldment form a current loop and the conductor is close to this part of the weldment, so that they form adjacent conductors to each other. High-frequency welding is based on the specific form and special requirements of the weldment structure, mainly using the skin effect and proximity effect, so that the surface metal of the weldment to be welded can be quickly heated to achieve welding.

The contents of the two major effects of high-frequency current in high-frequency welding are:

Skin effect - when the conductor is connected with alternating current, the current distribution on the conductor section is uneven, the current density gradually increases from the center of the conductor to the surface, and most of the current only flows along the surface of the conductor. The lower the resistivity, the greater the permeability and the higher the frequency of the current, the more significant the skin effect.

Proximity effect – A special physical phenomenon in which a high-frequency current flows in opposite directions to each other or in a reciprocating conductor when a high-frequency current flows in the opposite direction of two conductors.

High frequency welding typically uses currents in the frequency range of 300 450kHz, sometimes as low as 10kHz.

High-frequency weldingHigh-frequency welding was invented and applied to production in the early 50s, it is a kind of welding method that uses resistance heat heating generated by high-frequency current flowing through the connecting surface of the workpiece, and realizes the interconnection between the workpiece metals with (or without application) of the top forging force. It is similar to ordinary resistance welding, but there are many important differences.

The basic working principle of electric welding is to melt the electrode by the high energy generated by the short circuit of the circuit. Of course, this explanation is colloquial.

I mainly want to explain the effects of electric welding on the human body through the above principles:

1。If you don't use an electric welding cap to see the welding welding directly, then it will cause a slight burn to the eyes, which is what the welder often says "hitting the eyes", because it emits high-intensity light at the moment of short circuit, which is equivalent to us looking directly at the sun with our eyes.

2。For the body, there must be an electromagnetic field after the circuit is formed, and it must not be a good thing to work in the electromagnetic field for a long time, so I won't talk about it; Another point is that the gas volatilized by the flux of the electrode during welding is toxic, which is why the poison allowance of welders is higher than that of ordinary workers.

3。The damage of electric welding to the human body is not only measured by the word radiation

High Frequency Heating Machine Principle:

According to Faraday's principle of electromagnetic induction and the law of cold times, the mains power is converted into AC power of different frequencies by using a high-frequency host and supplied to the induction coil, which will generate an alternating magnetic field around the induction coil. At this time, if the magnetically permeable object is placed in the alternating magnetic field established by the induction coil, it will produce a hysteresis effect and thus generate heat, and the magnitude of this efficiency is related to the magnitude of the permeability of the object. In addition, if the object is a conductor, due to the cutting of alternating magnetic field lines, it will generate induced currents (eddy currents) at different depths, and due to the different impedance characteristics of the objects, eddy currents flow on the object, and the heat generated (Joule heating effect) is also different.

Therefore, the basic principle of induction heating is to use the electromagnetic induction phenomenon to generate eddy current on the workpiece to achieve the purpose of heating.

Advantages of high-frequency heating machine:

Instantaneous non-contact heating, the most advanced solid-state semiconductor technology design principle, built-in microcomputer processing system, stable power output, good continuity.

The energy efficiency conversion is high, which is more than 2 times that of the traditional heating method, which greatly saves the operating cost.

The output power can be digitally adjusted and analogized.

It can realize multi-stage heating, control the heating time, and accurately control the temperature by connecting an external infrared thermometer.

Safe and reliable, all output signals are safely isolated from the power supply system, complete signal interface, can be used with automation.

Built-in self-diagnosis and fault alarm function, convenient for timely repair.

Simple operation, safe, energy saving and environmental protection.

High-frequency heating machine application industry: all kinds of fine metal object heating, hot forging, smelting, welding, heat treatment, etc.

Communication industry: welding of heat dissipation copper plates, antennas, cable connectors, RF radio frequency lines, shaft core terminals, etc.

Metal saw blade industry: saw blade sawtooth, tungsten steel drill bit, ultra-micro drill bit and other welding and heat treatment.

Auto parts industry: hot pressing of screws into plastics, welding of starting capacitors and automobile parts.

Solar industry: welding of solar junction boxes, solar busbars, etc.

Electronics industry: tin, aluminum, nickel, silver, copper and other welding of various components.

The working principle of high-frequency welding: the workpiece is put into the inductor (the coil is usually made of copper tubes), and when the inductor is passed through a certain frequency of alternating current, an alternating magnetic field is generated around it. The electromagnetic induction of the alternating magnetic field produces a strong magnetic beam that changes instantaneously, and when the heated object such as metal is placed in the induction coil, the magnetic beam will run through the entire heated substance, and a large eddy current will be generated in the opposite direction of the heated current inside the heated substance, and the temperature of the substance itself will rise rapidly due to Joule heating generated by the resistance in the heated substance.

The high-frequency welding machine is different from other welding machines, and its function and purpose are not just a single welding. The high-frequency welding machine is essentially a high-frequency machine, and the Danyang Zhongfa high-frequency welding machine can not only be used for the welding of various metal materials, but also for diathermy, smelting, heat treatment and other processes. Welding is just one of its many uses.

Here's how it works:

First of all, a set of unique electronic circuits in the high-frequency machine converts the low-frequency alternating current (50Hz) input from the power grid into high-frequency alternating current (generally above 20,000Hz);

After the high-frequency current is added to the inductance coil (i.e., the induction coil), it is converted into a high-frequency magnetic field by the principle of electromagnetic induction, and acts on the metal object in the magnetic field;

The eddy current effect is used to generate an induced current (i.e., eddy current) in a metal object that is proportional to the strength of the magnetic field; (This eddy current is affected by the skin effect, and the higher the frequency, the more concentrated it is on the surface of the metal object).

When eddy currents flow through a metal object, heat is generated using the principle of the thermal effect of electric currents with the help of the resistance value inherent in the metal.

This kind of heat is not like it. The high-frequency welding machine is different from other welding machines, and its function and purpose are not just a single welding. The high-frequency welding machine is essentially a high-frequency machine, and the Danyang Zhongfa high-frequency welding machine can not only be used for the welding of various metal materials, but also for diathermy, smelting, heat treatment and other processes.

Welding is just one of its many uses.

Here's how it works:

First of all, a set of unique electronic circuits in the high-frequency machine converts the low-frequency alternating current (50Hz) input from the power grid into high-frequency alternating current (generally above 20,000Hz);

After the high-frequency current is added to the inductance coil (i.e., the induction coil), it is converted into a high-frequency magnetic field by the principle of electromagnetic induction, and acts on the metal object in the magnetic field;

The eddy current effect is used to generate an induced current (i.e., eddy current) in a metal object that is proportional to the strength of the magnetic field; (This eddy current is affected by the skin effect, and the higher the frequency, the more concentrated it is on the surface of the metal object).

When eddy currents flow through a metal object, heat is generated using the principle of the thermal effect of electric currents with the help of the resistance value inherent in the metal.

This heat is not transferred from the outside as in other heating methods. It is generated directly inside the object.

Therefore, this heating method is fast and efficient. If desired, it can melt any metal object in an instant. Moreover, its heating rate and temperature are controllable.

The so-called high frequency is relative to the AC current frequency of 50Hz, which generally refers to the high-frequency current of 50kHz and 400kHz. When high-frequency electric current passes through a metal conductor, it produces two peculiar effects: the skin effect and the proximity effect, which are used by high-frequency welding to weld steel pipes.

So, what are these two effects?

The skin effect refers to the fact that when the AC current passes through the same conductor at a certain frequency, the density of the current is not uniformly distributed in all sections of the conductor, but it will mainly concentrate on the surface of the conductor, that is, the density of the current on the surface of the conductor is large, and the density inside the conductor is small, so we call it the "skin effect". The skin effect is usually measured by the penetration depth of the current, and the smaller the penetration depth value, the more significant the skin effect.

This depth of penetration is directly proportional to the square root of the resistivity of the conductor and inversely proportional to the square root of frequency and permeability. In layman's terms, the higher the frequency, the more the current is concentrated on the surface of the steel plate; The lower the frequency, the more dispersed the surface current. It must be noted that:

Although steel is a conductor, its magnetic permeability decreases as the temperature increases, that is, when the temperature of the steel plate increases, the permeability decreases and the skin effect decreases.

Proximity effect refers to the fact that when a high-frequency current flows in opposite directions in two adjacent conductors, the current will flow intensively to the edge of the two conductors that are close to each other, and even if the two conductors have a shorter side, the current does not flow along the shorter route, which we call the "proximity effect".

The proximity effect is essentially due to the action of inductive reactance, which plays a dominant role in high-frequency currents. The proximity effect increases as the frequency increases and the spacing of adjacent conductors gets closer, and if a core is added around the adjacent conductors, the high-frequency current will be more concentrated on the surface of the workpiece.

These two effects are the basis for achieving high-frequency metal welding. High-frequency welding is to use the skin effect to concentrate the energy of high-frequency current on the surface of the workpiece; Proximity effects are used to control the location and range of high-frequency current flow routes. The speed of the current is very fast, and it can heat, melt, and achieve docking by extrusion of the adjacent steel plate edges in a very short time.