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Why the correct matching of high frequency welding machine is so important

In the welding process of solid-state high frequency welding machine, the ability to transfer all welding machine power to the working coil is determined by the matching of the impedance (load) of the coil and the ratio of the maximum output voltage of the transformer to the maximum output current.

If these values are not adjusted to be equal, the welder power cannot be completely output to the coil. If the match between the load and the frequency converter is reduced by 50%, a 400 kW welder may only deliver 200 kW to the coil. In this case, the unit’s production speed will be lower than the speed achieved when the welder load is fully matched. The specific performance is that the speed of the car can not go up.

As a part of the common resonance circuit, the coil determines the welding frequency. If the coil inductance required by the converter is not matched properly, a welder designed to work at 300 KHz may only run at 200 KHz, because 50% of the coils are not matched, which will seriously affect the quality of the welded pipe.

Why is the match at all power levels so important?

As we all know, in the process of high frequency welding, the production line is subject to various load changes, and the quality of weld seam changes with the load changes. What we need is continuous and stable output, which is a necessary condition for high quality welds.

In the actual production process, welding speed, welding frequency, welding power, opening angle size, impedance position, impedance working condition, magnetic flux size, thickness of steel strip, diameter of welded pipe, cooling water temperature, even Deburring and the habits of operators in different shifts, etc. all affect the load matching, so continuous maintenance of the best match is a prerequisite for ensuring the consistent quality of the welded pipe. Any of the above changes in the production process of the welded pipe will cause changes in the welder load, which is why the high frequency welder with automatic matching system is the best solution to ensure the quality of high quality welds. For manufacturers pursuing high-quality welded pipes, no matter how the external causes (loads) of the production line change, a high-frequency welding machine can intelligently enlarge the process window, and it is the most scientific and convenient way to digest these load changes through automatic matching. 

Can the voltage inverter welder perform load matching as accurately as the current inverter welder?

Most voltage inverter welders perform load matching by changing the contact points on the RF transformer. If you want to match the load, you need to continuously change the junction of the transformer. This is basically impossible to adjust when the welder is working continuously.

The current inverter type welding machine automatically maintains the load matching through the automatic matching system. Without the participation of the operator, the welding machine can always work in the optimal load matching state to ensure the stable welded pipe weld quality.

When the welder is working and the load is matched, the output power and the welding frequency can be accurately and reliably maintained, so that the welding load changes and the calibration is ensured to ensure consistent weld quality.


Why the welding frequency parameter is so important?

From the history of the development of high-frequency welding machines, frequencies around 400 kHz have proven to be the best frequencies for induction welding processes. The welding frequency determines the width and amount of extrusion of the steel strip. These parameters are all necessary to achieve good weld quality. High frequencies reduce the depth of current penetration, a phenomenon known as the “Skin Effect.” The skin effect concentrates heat on the edge of the weld near the surface, achieving high quality forge welding with minimal extrusion. Conversely, the low frequency causes more of the weld bead to be heated, and in severe cases, it will cause embrittlement. The reduction in the width of the steel strip used alone has saved the manufacturer’s raw material costs by several hundred thousand yuan. The welding frequency also interacts with the set parameters of the unit, such as forming, opening angles and other roll geometry. In addition, the high-frequency welding process is more sensitive to the setting of the above parameters in the low-frequency state, and if it is not good, it can cause more unqualified products and unstable welding quality.

Apart from the mechanical parameters of the unit, what else is related to the frequency?

The performance of impedance also depends on frequency. All impedance devices are limited to saturated flux density, which is called flux conductivity. If this limit is exceeded, the impedance will stop working. The magnetic flux in the impedance varies with the frequency conversion. For example, a working impedance can withstand twice the magnetic flux at 200 KHz than at 400 KHz. Reducing welding frequency may require additional impedance material (magnetic rod). When welding small diameter thick-walled pipe, the quality and magnetic flux of impedance material (magnetic rod) are particularly important because of the limitation of actual space conditions.


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Post time: Apr-18-2019

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