What is Included in the Welding of Spiral Finned Tube?

Spiral finned tube welding is generally used high frequency welding, so what knowledge does it include? Jetvision share something with you.

1. Welding principle

High frequency current is used as a heat source to heat the contact surface and the area to be welded, and at the same time, the top forging force is applied on the outside of the finned tube, so as to realize the solid-phase welding of the contact surface.

2. Preparation before welding

(1) The surface of the pipe material should not have obvious pits, sandblasting to remove oil, rust and other dirt.

(2) The preparation of the top forging wheel to ensure that its clamping of the steel strip in the circumferential direction is the right amount of tension, and is uniform, the inner parts can be flexible rotation.

(3) The welding between the electrode body and the contact should be firm and reliable, with smooth cooling and no leakage.

3. Welding parameters

Mainly including the tensile strength of welded joints, welding rate, etc., the indicators of these parameters must meet the national standards, such as Q/SH.MM.25-2000.

4.Welding inspection

Appearance inspection: Appearance inspection is carried out after welding, and the result of the inspection should meet the standard requirements.

Welding rate inspection: peel off 2 to 3 circles of finned tube, check every 120 degrees, and divide the actual weld width by the nominal thickness of steel strip to get the welding rate.

Metallographic inspection: from the joining surface, for the incomplete normalized organization and the original normalized organization, check for inclusions, unfused and cracks and other macro-defects.

5. Connotation of high frequency welding

High frequency welding is a technology of welding, there are two kinds of induction welding and contact resistance welding.

It has three types of welding systems for:

Solid phase plasticity pressure welding - the intersection area of the edge of the billet is heated to 1300℃- 1350℃plastic state, and then under the pressure of the extrusion rollers will be extruded under the pressure of the oxide film out of the weld, and at the same time, through the high temperature so that the two edges are welded together, and its extruded strength is required to be greater than 40 The extruded strength is more than 40-50MPa.

Semi-melting welding - the billet edge of the intersection area heated to a semi-molten state, through the extrusion roller extrusion, will be sandwiched between the oxide of the liquid film extrusion weld, and at the same time to complete the weld, the extrusion strength is generally 20-30MPa.

Melting welding - the edge of the billet junction area heated to a molten state, the welding temperature of 1400℃or more, at this time the molten metal partially gasification, and then through the extrusion roller extrusion, in the whole liquid lap area occurs periodically spark spatter, the extrusion strength is close to the semi-molten welding.

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