Hot-Working Crack Prediction Using Decarburization Layer Properties
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Solution Overview
Problem
Existing methods for predicting hot working conditions in steel forging are inadequate in accurately predicting surface cracks, leading to reduced yield and increased costs due to defect removal processes.
Innovation Solution
A prediction method that includes acquiring hot working properties in the two-phase ferrite + austenite region of the decarburization layer, performing plastic deformation analysis to derive a fracture threshold, and simulating actual hot working to determine a working condition threshold, thereby suppressing cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional fracture prediction methods using bulk material properties are used, then the prediction process is simple, but the prediction accuracy for surface cracks is insufficient
Solution Approach 1:
The invention applies local quality by specifically measuring hot working properties in the decarburization layer (surface region) rather than using bulk material properties. The tensile test pieces are designed with the decarburization layer positioned at the tensile stress concentration region, enabling localized property assessment that directly correlates with surface crack susceptibility.
Solution Approach 2:
The invention segments the material into distinct regions (decarburization layer vs. base material) and performs separate property assessments. By creating test pieces where the decarburization layer is positioned to experience specific stress states, the method isolates and evaluates the hot working properties of the surface layer independently from the bulk material.
2Reliability
If defect removal processes are performed to repair cracks, then crack defects are eliminated, but yield is reduced and costs increase
Solution Approach 1:
The invention performs preliminary action by predicting the hot working condition threshold before actual forging operations. By conducting tensile tests to determine hot working properties and calculating the threshold in advance, the method enables prevention of cracks during the actual hot working process, eliminating the need for subsequent defect removal operations.
3Reliability
If hot working properties are not accurately determined, then the prediction method is simple, but cracks occur during hot working
Solution Approach 1:
The invention applies parameter changes by measuring hot working properties at elevated temperatures (e.g., 900°C) rather than room temperature. The tensile tests are conducted at the actual hot working temperature to capture the temperature-dependent mechanical properties, and these temperature-specific properties are then used to calculate the hot working condition threshold.
Data Source
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AI summary
The object of the present invention is to provide a prediction method capable of highly accurately predicting a hot working condition under which cracks occur and suppressing the occurrence of cracks in actual hot working. Provided is a prediction method for a hot working condition for predicting a hot working condition of a material subjected to hot working having a decarburization layer on a surface layer, comprising: a hot working property acquisition process of acquiring a hot working property at a part of a two-phase region of ferrite + austenite in the decarburization layer formed on the surface layer of the material subjected to hot working; a first analysis process of performing a plastic deformation analysis by simulation using the acquired hot working property as an input value and deriving a fracture threshold; a second analysis process of performing a plastic working analysis by simulation simulating actual hot working and deriving a fracture parameter corresponding to an amount of deformation of a material subjected to hot working; and a working condition derivation process of deriving a working condition threshold at a time of performing hot working in an actual machine based on the fracture threshold and the fracture parameter.