Graphite Electrodes for Direct Joule Heating of Steel Strips
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Solution Overview
Problem
Existing Joule effect heating technologies for steel strips, wires, and pressed or drawn wires face inefficiencies due to indirect heating methods, such as high energy costs and long dead times, and direct heating methods suffer from sparks, deformations, and mechanical property reductions due to metal-on-metal contact.
Innovation Solution
A device using non-ferrous material electrodes, preferably graphite, for direct contact and current transmission in a continuous Joule effect heating process, allowing for high directivity and selectivity of energy with reduced material deformation and surface damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metal rollers are used as electrodes for direct heating, then heating efficiency is improved, but material surface damage and deformation occur due to metal-on-metal contact
Solution Approach 1:
The patent introduces a non-ferrous material layer (such as copper or aluminum) as an intermediary between the metal roller and the steel material being heated. This intermediate layer prevents direct metal-to-steel contact, eliminating sparks and surface damage while maintaining effective electrical contact for Joule heating. The non-ferrous material acts as a mediator that transfers current without causing harmful mechanical or thermal effects on the steel surface.
Solution Approach 2:
The electrode roller is constructed as a composite structure combining ferrous and non-ferrous materials. The core provides structural strength and electrical conductivity, while the outer non-ferrous coating (copper, aluminum, or their alloys) provides a non-sparking contact surface. This composite design integrates the advantages of both material types: mechanical robustness and surface protection.
2Reliability
If contact pressure is increased to ensure electric continuity, then current transmission is improved, but material deformation increases due to mechanical stress
Solution Approach 1:
The patent changes the material parameter of the contact surface from ferrous to non-ferrous material, which fundamentally alters the friction and deformation characteristics. The non-ferrous material has lower hardness and different mechanical properties compared to steel, allowing for adequate contact pressure to ensure electrical continuity while minimizing plastic deformation and surface indentation of the steel workpiece.
3Stability of the object's composition
If indirect heating by convection or radiation is used, then uniform heat distribution is achieved, but energy efficiency decreases and dead time increases
Solution Approach 1:
The patent applies local quality by concentrating heating energy directly at the contact points between the roller and the steel material. Instead of heating the entire oven environment uniformly, the Joule effect generates heat locally where current passes through the material, achieving efficient energy transfer. The uniformity of heating is controlled by the distribution and pressure of multiple contact points along the roller surface.
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
The use of non-ferrous electrodes, particularly graphite, enables efficient and uniform heating with reduced material deformation and surface damage, improving energy efficiency and reducing heating and cooling dead times.
Implementation Method 1
the passage of an electric current inside the element to be processed through the thermal treatment (direct heating)
Implementation Method 2
at least an electrode of non-ferrous material is provided at a contact station
Data Source
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AI summary
A device (1) for transmission of electric current in a continuous Joule effect heating process to a steel strip, wire, pressed or drawn wire (2), comprising at least a support structure (12) for the continuous Joule effect heating process of a steel strip, wire, pressed or drawn wire (2), and a plurality of electrodes (3) having their entire body made of graphite and being mounted inside said support structure (12) on a contact element (11), said electrodes (3) being in physical and electrical contact with said steel strip, wire, pressed or drawn wire (2), and being arranged in a row of lower electrodes (3) and a row of upper electrodes (3), in respect of said steel strip, wire, pressed or drawn wire (2), and said rows are staggered and capable of achieving a serpentine passage of said steel strip, wire, pressed or drawn wire (2) between said electrodes (3).