Electrical Steel Laser Grooving With Minimal Heat-Affected Zones
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Solution Overview
Problem
Existing processes for manufacturing electrical steel with heat-resistant refined magnetic domains face limitations in retention temperature and production speed, and are not adaptable to various types of materials and working conditions, leading to suboptimal iron losses and vibrations.
Innovation Solution
A process involving pulsed laser treatment with specific parameters such as peak power density greater than 50 TW/cm², cumulative energy density between 10 J/cm² and 3500 J/cm², and laser pulse duration less than the heat diffusion characteristic time, allowing for the formation of clean grooves with minimal heat-affected zones and higher retention temperature, enabling efficient reduction of iron losses and vibrations across a range of working conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional laser treatment processes are used to refine magnetic domains, then domain refinement is achieved, but the retention temperature is limited and heat-affected zones are large
Solution Approach 1:
The invention changes the key parameters of laser treatment: using ultra-short pulsed laser with pulse duration of 10^-9 to 10^-12 seconds and peak power density of 10^10 to 10^12 W/cm². These parameter changes enable ablation mode operation that confines thermal effects, achieving high retention temperature (above 700°C) while minimizing heat-affected zones compared to conventional continuous or long-pulsed laser treatment
Solution Approach 2:
The invention employs periodic pulsed laser action instead of continuous laser beam. The ultra-short pulses (10^-9 to 10^-12 seconds) are delivered in periodic sequences with controlled repetition rates, allowing thermal diffusion to occur between pulses while maintaining cumulative ablation effect. This periodic action enables high retention temperature while limiting heat-affected zone expansion
2Loss of energy
If laser treatment parameters are optimized for domain refinement, then iron losses are reduced, but production speed decreases
Solution Approach 1:
The invention maintains continuous useful action by using high repetition rate pulsed laser sequences. Multiple ultra-short pulses are delivered in rapid succession (continuous wave train mode) to achieve the required ablation depth and domain refinement effect, eliminating the need for long idle times between treatment passes while maintaining low iron losses through optimized pulse parameters
Solution Approach 2:
The invention introduces dynamic control of laser parameters during treatment. The pulse duration (10^-9 to 10^-12 seconds), peak power density (10^10 to 10^12 W/cm²), and repetition rate are dynamically adjusted based on material type, desired refinement level, and production speed requirements, enabling optimization of both iron loss reduction and productivity for different operating conditions
3Adaptability or versatility
If a single laser process is used for all electrical steel types, then process simplicity is maintained, but adaptability to various materials and conditions is poor
Solution Approach 1:
The invention creates a universal laser treatment process that can handle multiple electrical steel types (grain-oriented, non-grain-oriented, amorphous, nanocrystalline) and various processing stages (before/after coating, before/after annealing). The ultra-short pulsed laser with adjustable parameters (10^-9 to 10^-12 seconds duration, 10^10 to 10^12 W/cm² power density) serves multiple functions: ablation, domain refinement, and surface modification, eliminating the need for different specialized processes for different materials
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 process achieves a higher retention temperature, enabling subsequent treatments and improved productivity, with enhanced iron loss reduction and vibration suppression for a variety of electrical steel applications, including fully processed and semi-processed materials.
Implementation Method 1
forming a plurality of grooves on at least one of the first and second surfaces with at least one pass of a pulsed laser... the laser pulse duration being equal to or less than a heat diffusion characteristic time of the electrical steel... peak power density being more than 50 TW/cm²
Data Source
Figure 1a~1c
Figure 1d
Figure 1e
AI summary
A process for manufacturing an electrical steel sheet, the process comprising : a- providing a sheet of laminated electrical steel having a first and a second surface, a rolling direction or at least one easy magnetization direction(s), and a characteristic time for heat diffusion; b- forming a plurality of grooves on at least one of the first and second surfaces with at least one pass of a pulsed laser, each pass being associated with a scanning direction, the laser having a laser pulse repetition frequency, a pulse duration and emitting a light at a laser wavelength with a peak power density and a cumulative energy density per pass, the process being characterised in that : i) the laser pulse duration is equal to or less than a heat diffusion characteristic time of the electrical steel; ii) the peak power density is more than 50 TW/cm2 or/ and the product between the peak power density and the pulse repetition frequency is more than 5000 TW/cm2/ms. iii) the cumulative energy density per laser pass is comprised between 10 J/cm2 and 3500 J/cm2.