Hot-Working Tool Material Toughness Variation Control
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Solution Overview
Problem
Hot work tools exhibit variations in Charpy impact value, leading to inconsistent toughness, which affects their lifetime and performance.
Innovation Solution
A hot work tool material with an annealed structure comprising ferrite grains, where less than 10% of ferrite grains have a maximum diameter over 100 µm and an aspect ratio over 3, is quenched and tempered to achieve a uniform martensitic structure, reducing variations in toughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional alloy tool steel (e.g., SKD61) is used for hot work tool material, then the tool has sufficient toughness to resist impact, but the toughness is inconsistent across different portions of the tool, affecting lifetime
Solution Approach 1:
The invention changes the chemical composition parameters of the steel material by strictly controlling carbon content (0.30-0.50%) and adding specific alloying elements (Cr: 3.00-6.00%, Mo: 0.50-3.50%, W: 0.50-3.00%, V: 0.10-1.50%) to achieve uniform martensitic structure after heat treatment, which resolves the toughness inconsistency issue
Solution Approach 2:
The invention performs preliminary heat treatment (annealing) before quenching to obtain a uniform austenitic structure with fine grain size, which ensures that the subsequent quenching produces uniform martensite throughout the tool, preventing local toughness variations that would reduce tool lifetime
2Strength
If the steel material is annealed to improve toughness, then the Charpy impact value increases, but the variation in Charpy impact value across different tool portions remains high
Solution Approach 1:
The invention changes the microstructural parameters by controlling the annealing process to achieve fine austenite grain size (10-20 μm) and uniform distribution of alloy carbides, which transforms the material properties to produce consistent toughness throughout the tool after quenching and tempering
Solution Approach 2:
The invention ensures uniform local quality throughout the material by controlling the homogeneous distribution of alloying elements and preventing local segregation during solidification and heat treatment, which eliminates the cause of toughness variation across different tool portions
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 approach effectively suppresses variations in toughness, ensuring consistent high toughness and extended tool lifetime by controlling the distribution and size of ferrite grains in the annealed structure before quenching and tempering.
Implementation Method 1
the term 'quenching' refers to an operation where a hot work tool material (or a hot work tool material that has been subjected to machining) is heated to an austenitic phase temperature range and then rapidly cooled to transform it into a martensitic structure
Implementation Method 2
The supplied material is machined into a shape of the hot work tool and then quenched and tempered to adjust its hardness for use
Data Source
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AI summary
Provided are a hot-working tool material having an annealed structure that is effective in suppressing variations in toughness when processed into a hot-working tool, a method for manufacturing a hot-working tool using the hot-working tool material, and a hot-working tool. The hot-working tool material has an annealed structure and is to be quenched and tempered before using, wherein: the hot-working tool material has a composition from which a martensite structure can be prepared by the quenching; and, in ferrite crystal grains in the annealed structure in a cross section of the hot-working tool material, the ratio by number of ferrite crystal grains having a largest diameter (L) of 100 µm or more is not more than 10.0% relative to the total ferrite crystal grains, and the ratio by number of ferrite crystal grains having an aspect ratio (L/T) [wherein (L) stands for a largest diameter, and (T) stands for the largest transverse width orthogonally crossing the same] of 3.0 or more is not more than 10.0% relative to the total ferrite crystal grains. Preferably, the ferrite crystal grains in the annealed structure in a cross section of the hot-working tool material have an average grain diameter, expressed in equivalent circle diameter, of not more than 25.0 µm. The method for manufacturing a hot-working tool, said method comprising quenching and tempering the hot-working tool material, and the hot-working tool thus obtained are also provided.