HFI tube

In the production process of high-frequency induction (HFI) welded pipes, hot-rolled steel coils are fed into high-capacity energy storage devices to achieve continuous welding.

High frequency welding is a steel pipe welding process in which the heat source used to melt the joint surface is obtained through high-frequency (HF) alternating current (AC) resistance heating.

High frequency induction (HFI) resistance pressure welding technology for longitudinal welding. The annular strip passes through the rolling mill frame, where it is shaped into an open tube that passes through a high-frequency inductor composed of single winding or multi winding metal coils. As a result, high-frequency loop current is induced into the pipeline, which is preferably closed at the edge of the strip where the welding point converges. The temperature required for welding is generated by resistance heating in narrow areas along the edge of the strip.

The edges of the heated strip are compressed together by pressure rollers, forming a uniform longitudinal weld without any filler metal. The flash generated on the inner and outer surfaces during the welding process is scraped to the level of the pipeline surface with a special tool.

Afterwards, the HFI weld is immediately subjected to multi-step induction annealing treatment to ensure that the properties of the weld area match those of the substrate. Then, straighten the continuous pipe column, roll the size, and finally cut it into a certain length with a flying saw.

The edges of the coil are milled using hard alloy cutting tools to ensure high-quality welding. Then, a set of cage rollers and fin channels are used to form a coil through cold forming method, and high-frequency current is connected through induction or alternating conduction method.

The process first cuts the required size of strip on the longitudinal cutting line, and then feeds it into a pipe mill to form a pipeline pipe. Once the pipeline is formed, it will be welded together at the edges using a high-frequency welding machine.

During the welding process, due to the generation of a large amount of heat, welding beads will form at the edges inside and outside the pipeline. Then cut these beads to allow unrestricted flow of fluid/gas inside the pipeline.

Afterwards, according to the customer's requirements, the pipeline is cut into the required length and transferred to the precision machining section for further processing and testing, such as straightening, end chamfering/surface treatment, hydrostatic testing, non-destructive testing, threading, galvanizing, etc.

HFI welding

The pipeline is longitudinally welded using high-frequency induction (HFI) resistance pressure welding. The annular strip passes through the rolling mill, where it forms an open tube that passes through a high-frequency inductor composed of single winding or multi winding metal coils. This induces a high-frequency loop current in the tube, which preferentially closes at the edge of the strip and converges at the welding point. The temperature required for welding is generated by heating the narrow area at the edge of the strip with resistance.

The edges of the heated strip are pressed together by a pressure roller to form a uniform longitudinal weld without any filler material. Use specialized tools to scrape the burrs generated during the welding process of the inner and outer surfaces to the level of the pipeline surface.

Afterwards, the HFI weld is immediately subjected to multi-stage induction annealing treatment to ensure that the performance of the weld area matches that of the substrate. Then, use a flying saw to straighten and roll the continuous pipe to the desired size, and finally cut it to the desired length.