Impeder Core Recessed Area for Electric Resistance Welding
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Solution Overview
Problem
Conventional electric-resistance welded pipe manufacturing devices face issues with impeder core deterioration and mandrel rupture due to magnetic flux saturation and induction heating, leading to reduced welding efficiency and production hindrances.
Innovation Solution
The mandrel is equipped with an impeder core and a recessed area to reduce magnetic flux density, featuring a recessed area on the impeder core to increase separation distances from the induction coil and lower end, combined with a hollow impeder case for cooling and electromagnetic shielding to prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an impeder core is provided inside the open pipe to block induced current, then welding efficiency is improved, but magnetic flux saturation causes burnout and mandrel rupture
Solution Approach 1:
The impeder core is segmented into multiple sections along the axial direction, with air gaps between sections. This segmentation reduces magnetic flux saturation by preventing continuous magnetic flux paths, thereby reducing induction heating and preventing burnout while maintaining current blocking effectiveness for welding efficiency
Solution Approach 2:
An air gap is introduced as an intermediary between impeder core sections. This air gap acts as a magnetic flux barrier that reduces saturation and induction heating in the impeder core, protecting the mandrel from rupture while allowing the impeder to continue blocking harmful induced currents
2Ease of manufacture
If high-frequency current is applied to heat end portions for welding, then welding is achieved, but inner circumferential current causes induction heating of the mandrel
Solution Approach 1:
The impeder core is divided into multiple sections with air gaps, creating discontinuous magnetic flux paths that prevent the formation of continuous inner circumferential currents. This reduces induction heating of the mandrel while maintaining the ability to generate welding current at the end portions
Solution Approach 2:
The harmful inner circumferential current is extracted or blocked by the impeder core segments. The air gaps between segments prevent the current from forming a complete circuit around the mandrel, thereby eliminating the harmful induction heating effect while preserving the welding current path
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively suppresses impeder core deterioration and mandrel damage, ensuring stable and prolonged production of electric-resistance welded pipes by reducing magnetic flux saturation and induction heating.
Implementation Method 1
a primary current through this induction coil, thereby directly generating an induced current in the open pipe
Implementation Method 2
the open pipe is heated to a melting temperature by applying a high-frequency current to end face portions of the open pipe
Implementation Method 3
a generated magnetic flux causes the impeder to confront magnetic flux saturation or burnout
Implementation Method 4
a generated magnetic flux penetrates into the open pipe, resulting in a ferromagnetic field at the opening of the open pipe
Implementation Method 5
a hollow impeder case for cooling and electromagnetic shielding to prevent overheating
Data Source
Figure 1A~1B
Figure 2~3
Figure 4A~4B
AI summary
An object of the present invention is to properly control deterioration and damage of an impedance device for manufacturing an electric-resistance welded pipe due to induction heating, the resulting reduction in welding efficiency, prevention of mandrel breakage, and hindrance to production. The mandrel and impedance device of the present invention are a mandrel and impedance device for manufacturing an electric-resistance welded pipe, which are provided inside an open pipe in which end portions melted by an induced current are welded together. An impeder core made of a magnetic material and the mandrel for manufacturing the electric-resistance welded pipe, which is located inside the impeder core, serves as a support member of the impeder core, and is extended in a predetermined direction, are included. A recessed area is formed at a part of the impeder core within a predetermined size along an extending direction of the mandrel, and a size of the recessed area in a direction orthogonal to a running direction is 20 mm or more and 1/3 of a length of an outside dimension of the mandrel or less.