Austenitic Steel Hot Workability via Composition Index
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Solution Overview
Problem
High manganese steel materials with high austenite stability suffer from increased crack sensitivity at high temperatures due to the presence of elements like aluminum and phosphorus, affecting their hot workability and surface quality.
Innovation Solution
A non-magnetic steel material composition with manganese (15-27 wt%), carbon (0.1-1.1 wt%), silicon (0.05-0.5 wt%), phosphorus (0.03 wt% or less), sulfur (0.01 wt% or less), aluminum (0.05 wt% or less), chromium (5 wt% or less), boron (0.01 wt% or less), and nitrogen (0.1 wt% or less), with a microstructure of 95% or greater austenite and an average grain size of 10 μm or greater, is developed, along with a manufacturing method involving reheating and hot rolling to achieve low hot crack sensitivity and high surface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large amounts of manganese and carbon are added to stabilize austenite, then non-magnetic characteristics are improved, but crack sensitivity at high temperatures increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ranges of multiple alloying elements (Mn: 15-27%, C: 0.1-1.1%, Si: 0.05-0.50%, P: ≤0.03%, S: ≤0.01%, Al: ≤0.050%, Cr: ≤5%, B: ≤0.01%, N: ≤0.1%) and using a composition index formula to quantify the balance between austenite stability and crack sensitivity. This systematic parameter control resolves the contradiction by finding the optimal composition window that maintains non-magnetic properties while minimizing hot cracking.
Solution Approach 2:
The patent creates a composite alloy system combining multiple elements (Mn, C, Si, P, S, Al, Cr, B, N) in specific proportions to achieve synergistic effects. The combination of austenite-stabilizing elements (Mn, C) with other alloying elements creates a complex composite material that simultaneously provides non-magnetic characteristics and improved hot workability through controlled microstructure.
2Ease of manufacture
If elements like aluminum or phosphorus remain in manufacturing processes, then manufacturing is easier, but internal grain boundary oxidation increases and hot ductility decreases
Solution Approach 1:
The patent uses parameter changes by setting specific upper limits for Al (≤0.050%) and P (≤0.03%) content, and incorporating a composition index formula that accounts for these elements' impact on hot ductility. This quantitative control allows the patent to maintain ease of manufacture while preventing excessive grain boundary oxidation and preserving hot working properties.
3Ease of manufacture
If high crack sensitivity is present, then material can be processed more easily, but surface quality of steel materials deteriorates
Solution Approach 1:
The patent applies parameter changes by controlling the composition index to be within a specific range (3.4 or less) through precise adjustment of alloying element contents. This composition control simultaneously achieves adequate processability and high surface quality by preventing crack formation during processing while maintaining manufacturability.
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 solution results in a non-magnetic steel material with uniform austenite, good non-magnetic characteristics, and high surface quality due to reduced crack sensitivity, ensuring high hot workability and improved product quality.
Implementation Method 1
reheating the slab to a temperature within a range of 1050° C. to 1250° C.
Implementation Method 2
cooling the hot-rolled steel material
Data Source
AI summary
Provided according to one embodiment of the present invention are a non-magnetic steel material and a method for manufacturing the same. The steel material comprises 15-27 wt % of manganese, 0.1-1.1 wt % of carbon, 0.05-0.50 wt % of silicon, 0.03 wt % or less (0% exclusive) of phosphorus, 0.01 wt % or less (0% exclusive) of sulfur, 0.050 wt % or less (0% exclusive) of aluminum, 5 wt % or less (0% inclusive) of chromium, 0.01 wt % or less (0% inclusive) of boron, 0.1 wt % or less (0% exclusive) of nitrogen, and a balance amount of Fe and inevitable impurities, has an index of sensitivity of 3.4 or less, the index of sensitivity being represented by the following relational expression (1): [Relational expression 1]−0.451+34.131*P+111.152*Al−799.483*B+0.526*Cr≤3.4 (wherein [P], [Al], [B] and [Cr] each mean a wt % of corresponding elements), and contains a microstructure with austenite at an area fraction of 95% or greater therein.