Motor Core Heat Treatment for Grain Growth and Strain Relief
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Solution Overview
Problem
Existing motor core production methods face challenges in achieving simultaneous strain relief and grain growth in laminates, with low annealing temperatures limiting grain growth and increasing material procurement costs.
Innovation Solution
A motor core production method involving a two-stage heat treatment process: first heating at 500° C. to 800° C. in a low oxidizing or reducing gas atmosphere, followed by soaking at 1,000° C. to 1,200° C. in a vacuum, using a C/C composite jig to prevent deformation, and employing convection heat transfer and vacuum heating to efficiently grow crystal grains while preventing oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If strain relief annealing is performed at low temperature, then processing strain is reduced, but crystal grain growth is limited and material procurement cost increases
Solution Approach 1:
The heat treatment process is divided into three distinct stages: first heating (500-800°C in atmospheric gas), second heating (1000-1200°C in vacuum), and annealing. This segmentation allows strain relief and grain growth to occur at different temperature stages, resolving the contradiction between achieving strain relief at low temperature and grain growth requiring high temperature.
Solution Approach 2:
The first heating step at 500-800°C in atmospheric gas is performed as a preliminary action before the second heating step. This preliminary heating prepares the laminate for the subsequent high-temperature vacuum treatment, enabling effective strain relief to occur before grain growth, thus resolving the temporal conflict between these two processes.
2Temperature
If annealing temperature is increased to promote grain growth, then crystal grain size increases, but oxidation of the laminate occurs
Solution Approach 1:
The patent uses vacuum environment (100 Pa or less) during the second heating step at 1000-1200°C, which prevents oxidation of the laminate while allowing high-temperature grain growth. This inert environment resolution allows the laminate to be heated to grain growth temperatures without oxidation damage.
3Temperature
If high temperature heat treatment is applied, then grain growth is achieved, but laminate shape changes due to reduced rigidity
Solution Approach 1:
A jig made of C/C composite material is introduced as an intermediary support during the high-temperature heat treatment. This jig maintains the laminate's shape and prevents deformation caused by reduced rigidity at 1000-1200°C, while allowing the grain growth process to occur effectively.
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 method enables effective strain relief and grain growth in motor cores, increasing the average crystal grain size from less than 100 μm to 300 μm, enhancing magnetic properties while maintaining the laminate's shape and reducing material costs.
Implementation Method 1
the laminate is heated in two stages, that is, convection heat transfer heating by using an atmospheric gas and subsequent vacuum heating
Implementation Method 2
soaking the laminate at 1,000° C. to 1,200° C. in a vacuum of 100 Pa or less after the first heating step
Implementation Method 3
an attempt is made to reduce processing strain by annealing a laminate of electromagnetic steel sheets
Implementation Method 4
it is considered effective to grow crystal grains of the electromagnetic steel sheet such that the gain size is 100 μm or more
Data Source
AI summary
The present invention relates to a motor core production method including: a preparation step of preparing a laminate of electromagnetic steel sheets each processed into a predetermined shape; a first heating step of heating the laminate at an atmospheric temperature of 500° C. to 800° C. in an atmospheric gas comprising at least one kind selected from the group consisting of a low oxidizing gas and a reducing gas, and having a dew point of −20° C. or lower; and a second heating step of soaking the laminate at 1,000° C. to 1,200° C. in a vacuum of 100 Pa or less after the first heating step, and a heat treatment device for performing the production method.