Reinforcing Steel Microstructure Tuning for Strength and Seismic Ductility
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Solution Overview
Problem
Current steel bars used in structural applications lack sufficient high-strength and seismic resistance characteristics, which are essential for taller and larger architectural and civil engineering structures.
Innovation Solution
A method for manufacturing high-strength steel bars involves reheating a steel slab with specific alloy compositions and controlling the process through hot-rolling and tempcore cooling to achieve a composite structure of equiaxed ferrite and pearlite with a tempered martensite hardened layer, optimizing the content of elements like carbon, manganese, chromium, and molybdenum, and incorporating elements such as tungsten and calcium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional steel bar manufacturing processes are used, then production cost and process simplicity are maintained, but the steel bars lack sufficient high-strength and seismic resistance characteristics
Solution Approach 1:
The patent applies parameter changes by precisely controlling alloy composition parameters (C: 0.18-0.45%, Si: 0.05-0.30%, Mn: 0.40-3.00%, and other elements within specified ranges) and process parameters (reheating temperature, rolling temperature, cooling rate) to achieve high-strength steel bars with yield strength ≥500 MPa and yield ratio ≤0.80, resolving the contradiction between maintaining simple processes and achieving superior mechanical properties
Solution Approach 2:
The patent creates a composite microstructure consisting of equiaxed ferrite and pearlite phases through controlled cooling and tempering processes. This composite material structure at the micro-level provides both high strength and good ductility, enabling the steel bar to achieve yield strength ≥500 MPa while maintaining elongation ≥12%, thus resolving the strength versus process complexity contradiction
2Strength
If alloy composition is optimized for high strength, then yield strength increases, but manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific parameter ranges for alloy composition (C: 0.18-0.45%, Si: 0.05-0.30%, Mn: 0.40-3.00%, P: ≤0.04%, S: ≤0.04%, Cr: ≤1.0%, Cu: ≤0.50%, Ni: ≤0.25%, Mo: ≤0.50%, Al: ≤0.040%, V: ≤0.20%, N: ≤0.040%, Sb: ≤0.1%, Sn: ≤0.1%) and process parameters (reheating temperature, rolling temperature, cooling rate) that balance manufacturing feasibility with achieving yield strength ≥500 MPa and yield ratio ≤0.80, resolving the contradiction between high strength and manufacturing precision requirements
3Strength
If high-strength characteristics are achieved through alloying, then yield strength increases, but cost increases
Solution Approach 1:
The patent optimizes alloy composition parameters to achieve high strength with controlled element content, specifying ranges such as C: 0.18-0.45%, Mn: 0.40-3.00%, Cr: ≤1.0%, Mo: ≤0.50%, and other elements within limited ranges. This balanced composition achieves yield strength ≥500 MPa while controlling the quantity of expensive alloying elements, resolving the contradiction between high strength and material cost
Solution Approach 2:
The patent creates local quality differences through the composite microstructure of equiaxed ferrite and pearlite phases, where different regions provide different properties: ferrite provides ductility and toughness while pearlite provides strength. This local differentiation allows the steel to achieve high overall strength without requiring excessive alloying throughout the entire material, thus resolving the strength versus cost contradiction
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 method results in steel bars with a yield strength of at least 500 MPa and a yield ratio of 0.8 or lower, providing enhanced high-strength and seismic resistance characteristics.
Implementation Method 1
reheating a steel slab at a temperature ranging from 1000° C. to 1100° C.
Implementation Method 2
cooling the hot-rolled steel to a martensite transformation start temperature (Ms (° C.)) through a tempcore process
Implementation Method 3
cooling the hot-rolled steel to a martensite transformation start temperature (Ms (° C.))
Implementation Method 4
a step of subjecting the cooled steel to a recuperation process at a temperature of 500° C. to 700° C.
Data Source
AI summary
A method for manufacturing a high-strength steel bar can include the steps of: reheating a steel slab at a temperature ranging from 1000° C. to 1100° C., the steel slab including a certain amount of carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), chromium (Cr), copper (Cu), nickel (Ni), molybdenum (Mo), aluminum (Al), vanadium (V), nitrogen (N), antimony (Sb), tin (Sn), and iron (Fe) and other inevitable impurities, The method can further include finish hot-rolling the reheated steel slab at a temperature of 850° C. to 1000° C., and cooling the hot-rolled steel to a martensite transformation start temperature (Ms (° C.)) through a tempcore process.