Multiphase Steel Alloy Composition for Expanded Annealing Process Window
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Solution Overview
Problem
The existing alloy concepts for multiphase steels have a narrow process window, making it difficult to achieve uniform mechanical properties across varying sheet thicknesses and widths during continuous annealing, leading to inefficiencies and increased waste due to temperature and time sensitivity, especially in flexibly rolled strips with different thicknesses and widths.
Innovation Solution
A new alloy composition combining titanium, niobium, vanadium, and boron with molybdenum to expand the process window, allowing for more homogeneous mechanical-technological properties across different cross-sectional changes, enabling the production of steel strips with varying thicknesses and widths using the same process parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing alloy concepts are used for multiphase steels, then the steel can be produced with basic mechanical properties, but the process window is narrow making it difficult to achieve uniform properties across varying sheet thicknesses and widths
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the steel alloy. Specifically, it defines precise ranges for carbon (0.15-0.40%), silicon (0.10-0.65%), manganese (1.50-3.00%), and other alloying elements to expand the process window. This compositional parameter optimization enables uniform mechanical properties across varying sheet thicknesses and widths during continuous annealing, resolving the contradiction between manufacturing precision and process adaptability.
2Productivity
If the process window is expanded to accommodate varying sheet thicknesses and widths, then production efficiency increases, but maintaining consistent mechanical properties becomes more challenging
Solution Approach 1:
The patent uses parameter changes by establishing specific compositional ranges for multiple alloying elements that work synergistically to maintain consistent mechanical properties across a wider range of sheet dimensions. The controlled composition ensures uniform phase transformation behavior during annealing, enabling expanded productivity without sacrificing property consistency.
Solution Approach 2:
The patent applies composite materials principle by creating a multiphase steel structure consisting of ferrite, bainite, and martensite phases. This composite microstructure, achieved through controlled alloying and heat treatment, provides both the ductility needed for varying thicknesses and the strength consistency required across different sheet dimensions, thus resolving the contradiction between productivity and manufacturing precision.
3Reliability
If alloy composition is optimized for uniform properties, then manufacturing complexity increases, but process reliability improves
Solution Approach 1:
The patent applies parameter changes by defining specific, optimized ranges for multiple alloying elements rather than using simple compositions. This sophisticated parameter optimization enhances process reliability by ensuring consistent phase transformation behavior across varying sheet dimensions. While the composition appears complex, each element serves a specific function that collectively improves reliability.
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 expanded process window ensures more reliable and efficient continuous annealing of multiphase steel strips, allowing for the production of stress-optimized components with consistent mechanical properties across the strip length and width, even with varying thicknesses, and enables the production of steels in different strength classes.
Implementation Method 1
a new alloy concept for an ultra-high-strength multiphase steel with which the process window for the continuous annealing of hot or cold strip can be widened
Implementation Method 2
as a result of a delayed recrystallization or precipitation of micro-alloy elements an extreme grain fineness is established
Implementation Method 3
the phase transformation is temperature and time dependent. Thus, the less sensitive the steel is regarding the uniformity of the mechanical properties when temperature and time course change during the continuous annealing, the greater is the process window
Implementation Method 4
the process parameters such as throughput speed, annealing temperature and cooling rate, are adjusted corresponding to the mechanical-technological properties by way of the microstructure required therefore
Data Source
AI summary
In a process for producing a cold- or hot-rolled steel strip from an ultrahigh-strength multiphase steel having a particular composition the required multiphase microstructure is generated during continuous heat treatment. The cold- or hot-rolled steel strip is heated in the continuous heat treatment furnace to a temperature in the range from 700 to 950° C. and the heat-treated steel strip is subsequently cooled from the heat treatment temperature at a cooling rate of from 15 to 100° C./s to a first intermediate temperature of from 300 to 500° C. followed by cooling at a cooling rate of from 15 to 100° C./s to a second intermediate temperature of from 200 to 250° C.; the steel strip is subsequently cooled at a cooling rate of from 2 to 30° C./s in air to room temperature or the cooling at a cooling rate of from 15 to 100° C./s is maintained from the first intermediate temperature to room temperature.