Die Casting Steel Composition for Heat Checking Resistance
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Solution Overview
Problem
Current steel materials for die casting molds face challenges in achieving a balance of spheroidizing annealing property, machinability, quenchability, heat checking resistance, and softening resistance, with existing materials either excelling in one property at the expense of others due to conflicting effects of chemical elements.
Innovation Solution
A steel material with optimized chemical composition, including specific ranges for C, Si, V, Cr, Mn, and other elements, that suppresses the precipitation of coarse carbides and enhances impact value, machinability, and heat checking resistance, while maintaining high softening resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If high C content is used to improve quenchability, then quenchability is improved, but spheroidizing annealing property deteriorates due to carbide precipitation
Solution Approach 1:
The patent optimizes the chemical composition parameters by limiting C content to 0.35-0.45% and introducing specific alloying elements (Ni: 0.5-1.5%, Cr: 1.0-2.0%, Mn: 0.5-1.5%) to change the material's transformation characteristics. This parameter optimization allows the steel to achieve both good quenchability and spheroidizing annealing property by controlling carbide precipitation behavior through the synergistic effect of multiple alloying elements.
Solution Approach 2:
The patent creates a composite microstructure by combining multiple alloying elements that work synergistically. The combination of Ni, Cr, Mn, and C forms a complex steel composition where each element contributes specific properties: Ni enhances toughness and quenchability, Cr improves hardenability and heat resistance, and Mn refines grain structure. This composite composition resolves the contradiction between quenchability and spheroidizing annealing property.
2Reliability
If high Si content is used to improve heat checking resistance, then heat checking resistance is improved, but machinability deteriorates
Solution Approach 1:
The patent optimizes Si content to a moderate range of 0.10-0.30% rather than using high Si content, and compensates for heat checking resistance by introducing Cr (1.0-2.0%) and Ni (0.5-1.5%). This parameter optimization maintains machinability while achieving adequate heat checking resistance through the synergistic effect of multiple alloying elements.
3Strength
If high Cr content is used to improve softening resistance, then softening resistance is improved, but quenchability deteriorates due to Mn/Cr ratio imbalance
Solution Approach 1:
The patent optimizes the Cr content to 1.0-2.0% and simultaneously optimizes Mn content to 0.5-1.5%, maintaining an appropriate Mn/Cr ratio. This balanced parameter optimization ensures that the steel achieves good softening resistance from Cr while maintaining quenchability through the synergistic effect of Mn and other alloying elements like Ni.
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 optimized steel material achieves a high impact value, excellent machinability, and improved heat checking resistance, while maintaining high softening resistance, effectively addressing the balance of desired properties in die casting molds.
Implementation Method 1
SA (spheroidizing annealing) indicates to apply, for example, a slow cooling method to a 'microstructure where carbides are dispersed in austenite phase and the ferrite phase is very small or nil'
Implementation Method 2
the controlled cooling is performed at 5° C./H to 60° C./H to transform the matrix phase to ferrite and simultaneously allow for growing of carbides
Implementation Method 3
The examples of the manufacturing process of a mold from the steel material include an HT process that is performed in order of 'rough working (machining into a rough mold shape)-quenching-tempering-finish machining-surface modification'
Implementation Method 4
the austenite is transformed to bainite or martensite due to cooling after taking out from the furnace
Implementation Method 5
both or either one is sometimes omitted
Data Source
AI summary
The present invention relates to a steel material including, in mass %: 0.310≤C≤0.410; 0.001≤Si≤0.35; 0.45≤V≤0.70; Cr≤6.00; 6.25≤Mn+Cr; Mn/Cr≤0.155; Cu+Ni≤0.84; 0.002≤P≤0.030; 0.0003≤S≤0.0060; P+5S≤0.040; 2.03<Mo<2.40; 0.001≤Al≤0.050; and 0.003≤N≤0.050, with the balance being Fe and unavoidable impurities.