Grain-Oriented Electrical Steel Sheet Nitriding Control
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Solution Overview
Problem
Manufacturing ultra-thin grain-oriented electrical steel sheets with high magnetic characteristics is challenging due to difficulties in maintaining the Goss orientation and controlling precipitate loss during the rolling process, leading to increased iron loss and reduced magnetic flux density.
Innovation Solution
A method involving hot-rolling, cold-rolling, primary recrystallization annealing, and secondary recrystallization annealing, with a controlled nitriding gas flow and alloy composition, including chromium, nickel, tin, antimony, phosphorus, and silicon, to optimize crystal grain size and nitriding distribution, thereby improving magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the product sheet thickness is reduced to manufacture ultra-thin material, then the size of power generation equipment is reduced, but the degree of directness in Goss orientation is lost and magnetic characteristics deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the nitriding gas flow rate (0.5-5 L/min) and duration during primary recrystallization annealing, as well as controlling the crystal grain size ratio (Ds/DL ≤ 0.1). These parameter optimizations enable the formation of appropriate precipitates that maintain Goss orientation even in ultra-thin sheets (0.15-0.30 mm), thereby preserving magnetic characteristics while reducing equipment size.
2Loss of energy
If the thickness of product sheet is reduced, then eddy current loss is reduced, but it becomes difficult to maintain Goss orientation due to rapid loss of precipitates during secondary recrystallization
Solution Approach 1:
The patent applies preliminary action by performing primary recrystallization annealing with controlled nitriding gas treatment before secondary recrystallization. This preliminary treatment forms a stable distribution of fine crystal grains and precipitates that serve as a foundation for maintaining Goss orientation during subsequent secondary recrystallization, preventing rapid precipitate loss even in ultra-thin sheets.
Solution Approach 2:
The patent optimizes parameters including nitriding gas flow rate (0.5-5 L/min), primary recrystallization temperature (800-950°C), and crystal grain size control (Ds/DL ≤ 0.1). These parameter changes create optimal conditions for precipitate stability during secondary recrystallization, maintaining Goss orientation while reducing eddy current loss through thinner sheet production.
3Stability of the object's composition
If nitrogen gas fraction is increased during secondary recrystallization annealing to prevent precipitate loss, then precipitates are protected, but nitrogen outlets and surface defects are induced
Solution Approach 1:
The patent applies preliminary action by performing primary recrystallization annealing with controlled nitriding gas treatment before secondary recrystallization. This preliminary treatment forms a stable distribution of fine crystal grains and precipitates that serve as a foundation for maintaining Goss orientation during subsequent secondary recrystallization, preventing rapid precipitate loss even in ultra-thin sheets.
4Productivity
If hot-rolling thickness is reduced to achieve high cold rolling ratio for ultra-thin product, then productivity deteriorates due to maintenance of hot-rolling temperature and shape control
Solution Approach 1:
The patent optimizes parameters including nitriding gas flow rate (0.5-5 L/min), primary recrystallization temperature (800-950°C), and crystal grain size control (Ds/DL ≤ 0.1). These parameter changes create optimal conditions for precipitate stability during secondary recrystallization, maintaining Goss orientation while reducing eddy current loss through thinner sheet production.
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 method effectively controls the ratio of small to large crystal grains, enhancing magnetic characteristics and reducing iron loss, while maintaining a stable nitriding process to achieve high magnetic flux density and low iron loss in ultra-thin steel sheets.
Implementation Method 1
a method involving hot-rolling, cold-rolling, primary recrystallization annealing, and secondary recrystallization annealing, with a controlled nitriding gas flow
Implementation Method 2
a step for hot-rolling a slab to produce a hot-rolled sheet; a step for subjecting the cold-rolled sheet to primary recrystallization annealing
Implementation Method 3
primary recrystallization annealing, and secondary recrystallization annealing, with a controlled nitriding gas flow
Data Source
AI summary
A method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention comprises: a step for hot-rolling a slab to produce a hot-rolled sheet; a step for cold-rolling the hot-rolled sheet to produce a cold-rolled sheet; a step for subjecting the cold-rolled sheet to primary recrystallization annealing; and a step for subjecting the primary recrystallization annealing-completed cold-rolled sheet to secondary recrystallization annealing, wherein the primary recrystallization annealing step includes a preceding step and a subsequent step, and the amount (A) of nitriding gas introduced in the preceding step with respect to the total amount (B) of nitriding gas introduced in the primary recrystallization annealing step satisfies expression 1 below.0.05≤[A]/[B]≤[t] [Expression 1](In expression 1, the amount of nitriding gas introduced is in units of Nm3/hr, and [t] represents the thickness (mm) of a cold-rolled sheet.)