Mold Steel Composition for Softening Resistance and Thermal Conductivity
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Solution Overview
Problem
Existing steels for molds lack high softening resistance and thermal conductivity, leading to issues such as low initial hardness, excessive wear, and prolonged cooling times in high-temperature applications like die-casting and hot stamping.
Innovation Solution
A steel composition with specific ranges of C, Si, Mn, Cr, Mo+W, V, and N, optimized to produce a high amount of fine (Mo, W) carbides and controlled Cr carbides, resulting in improved hardness, softening resistance, and thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional steel compositions are used for molds, then the mold can be manufactured with standard materials, but the softening resistance and thermal conductivity are insufficient leading to excessive wear and prolonged cooling times
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the steel, specifically setting C: 0.28-0.65%, Si: 0.01-0.30%, Mn: 1.5-3.0%, Cr: 0.5-1.4%, Mo+W/2: 1.9-4.0%, V: 0.2-1.0%, and N: 0.01-0.10%. This optimized composition parameters achieve both high softening resistance and high thermal conductivity (30 W/(m·K) or more), resolving the contradiction between reliability and productivity
Solution Approach 2:
The patent creates a composite microstructure consisting of fine (Mo, W) carbides dispersed in a martensitic matrix with controlled retained austenite. This composite material structure combines the wear resistance of fine carbides with the thermal conductivity and toughness of the martensitic matrix, achieving both high softening resistance and efficient heat dissipation
2Strength
If high carbon content steel is used to increase hardness, then initial hardness improves, but thermal conductivity decreases and softening resistance deteriorates
Solution Approach 1:
The patent optimizes the carbon content parameter to a specific range (0.28-0.65%) rather than using high carbon content, and combines it with controlled amounts of alloying elements (Mn: 1.5-3.0%, Cr: 0.5-1.4%, Mo+W/2: 1.9-4.0%, V: 0.2-1.0%). This parameter optimization achieves initial hardness above 52 HRC while maintaining softening resistance through the formation of fine dispersed carbides
Solution Approach 2:
The patent creates local quality differences by forming fine (Mo, W) carbides uniformly dispersed in the matrix. These fine carbides provide localized hardening and wear resistance without compromising the overall thermal conductivity and softening resistance of the steel, achieving initial hardness above 52 HRC with maintained reliability
3Reliability
If high alloy content is added to improve softening resistance, then softening resistance improves, but manufacturing cost increases and thermal conductivity may deteriorate
Solution Approach 1:
The patent optimizes the alloy content parameters within specific ranges: Si: 0.01-0.30% (low to maintain thermal conductivity), Mn: 1.5-3.0% (moderate for hardenability), Cr: 0.5-1.4% (controlled for carbide formation), Mo+W/2: 1.9-4.0% (optimized for fine carbide precipitation), V: 0.2-1.0% (controlled for fine carbide formation). This parameter optimization achieves high softening resistance while controlling manufacturing cost and maintaining thermal conductivity above 30 W/(m·K)
Solution Approach 2:
The patent uses moderate amounts of Cr (0.5-1.4%) combined with Mo and W to form fine (Mo, W) carbides locally dispersed in the matrix. This local carbide formation provides high softening resistance without requiring excessive overall alloy content, thus controlling manufacturing cost while achieving the desired performance
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 composition achieves initial hardness above 52 HRC, reduced hardness change, and thermal conductivity above 30 W/(m·K), enhancing wear resistance and reducing cycle times in mold applications.
Implementation Method 1
a (Mo, W) carbide having a diameter of 0.2 μm or less is in an amount of 1.2 mass % or more
Implementation Method 2
the mold undergoes a thermal cycle during use
Implementation Method 3
for the steel for mold in a state after quenching and tempering
Data Source
AI summary
The present invention relates to a steel for mold, containing: 0.28 mass %≤C≤0.65 mass %, 0.01 mass %≤Si≤0.30 mass %, 1.5 mass %≤Mn≤3.0 mass %, 0.5 mass %≤Cr≤1.4 mass %, 1.9 mass %≤Mo+W/2≤4.0 mass %, 0.2 mass %≤V≤1.0 mass %, and 0.01≤N≤0.10 mass %, with the balance being Fe and inevitable impurities, in which, in a state after quenching and tempering, the steel has: a (Mo, W) carbide having a diameter of 0.2 μm or less being in an amount of 1.2 mass % or more, a ratio (mass ratio) of the amount of the (Mo, W) carbide to an amount of a Cr carbide being 11 or more, and a hardness change of 15 HRC or less.