high frequency weldingFinned tubeIt is a process of using the skin effect and proximity effect of high-frequency current to heat the outer surface of the steel strip and steel pipe while winding the steel pipe, until they reach a plastic state or melt, and completing the welding under a certain pressure of winding the steel strip. This high-frequency welding is actually a solid-state welding. Compared with methods such as inlay, brazing (or integral hot-dip galvanizing), it is more advanced in terms of product quality (high welding rate of fins, up to 95%), productivity, and automation. By using high-frequency current and welding while winding, the base tube and fins are basically integrated, and the welding rate is an important indicator for evaluating the quality of finned tubes.
（1）high frequency weldingFinned tubeAnnotation method for fin structure

Firstly, using CPG as the abbreviation for CHIPIAN GUAN, the structural characteristics, materials, and processing methods of finned tubes can be represented by the following series of numbers or symbols:
CPG ( φDb×δ/ Df / P / T –X /Y –A )
Among them: CPG ： Finned tube; φ Db × δ: outer diameter and thickness of the base pipe; Df : Outer diameter of fins, mm ; P : Fin pitch, mm ;
T : Fin thickness, mm ; X： Base pipe material; Y : Fin material; Among them: Fe : Iron; Al : aluminium Cu : Copper
A : Processing method: I ： High frequency welding (default if not marked); Other pending. As indicated in the diagram below.

For example, CPG (φ 32 × 3.5/64/8/1- Fe/Fe) indicates that the base tube outer diameter of the finned tube is 32mm, the wall thickness is 3.5mm, and the outer diameter of the fin is 64mm (i.e. the fin height is 16mm),
The pitch of the fins is 8mm, the thickness of the fins is 1mm, and both the base tube and fins are made of carbon steel, which is a high-frequency welded pipe.
In addition, sometimes it is necessary to separately label the structural parameters of the fins themselves, and the labeling method is as follows:
CP( Db / Df / P / T –Y )
The meanings represented by each symbol are the same as those of finned tubes. For example:
For example, CP (32/62/8/1- Fe) indicates that the outer diameter of the base tube of the fin is 32mm, and the outer diameter of the fin is 62mm (with a fin height of 15mm),
The fin pitch is 8mm, the fin thickness is 1mm, and the material is carbon steel.

High frequency welded finned tubeSuitable for high temperature and high pressure applications, the base pipe is made of stainless steel or ND steel for corrosion protection. In a working environment where the cooling temperature is above the dew point and there is no condensation, ordinary carbon steel can also be used as the base pipe
High frequency welded finned tubeThe thickness of the fins is usually above 0.8. Due to the limitations of the processing technology, the height of the fins should be smaller than the radius of the base tube. If it is necessary to make high fins, they can be made into serrated fins. It is widely used in preheating and recycling industries such as power, metallurgy, cement, and petrochemicals