High-Strength Steel Bar Composition Without Yield Platforms
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Solution Overview
Problem
Low-level steel bars exhibit high consumption of resources and energy, increased environmental burden, and fail to meet safety requirements due to low strength and obvious yield platforms, affecting building safety and deformation resistance.
Innovation Solution
A high-strength steel bar with specific chemical compositions and microstructures, including C, Si, Mn, Cr, Mo, Ni, V, Nb, Ti, and Al, combined with controlled carbon equivalents and optimized production processes, ensuring no obvious yield platform and enhanced mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If low-level steel bars are used, then resource consumption and energy consumption are increased, but the strength is low and obvious yield platform is caused
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters (C: 0.15-0.32%, Si: 0.10-0.50%, Mn: 1.00-2.50%, Cr: 0.30-0.60%, Mo: 0.10-0.30%, Ni: 0.10-0.30%, V: 0.02-0.80%, Nb: 0.01-0.10%, Ti: 0.01-0.10%, Al: 0.01-0.10%) and processing parameters (heating temperature 1200-1250°C, rolling temperature 850-950°C, cooling rate 2-5°C/s) to achieve high strength (≥600 MPa) while eliminating the yield platform, thereby improving strength without increasing resource consumption
Solution Approach 2:
The patent creates a composite microstructure consisting of ferrite, pearlite, bainite, and precipitated phases through multi-element alloying. This composite structure combines the advantages of different phases: ferrite provides ductility, pearlite provides strength, bainite provides toughness, and precipitated phases (from V, Nb, Ti) provide precipitation hardening, achieving high strength and no yield platform simultaneously
2Reliability
If low-level steel bars are used, then building safety is affected due to low strength and large plastic deformation in yield stage
Solution Approach 1:
The patent changes the material parameters by controlling carbon equivalent (Ceq = C + Mn/6 + (Cr+Mo+V)/5 + (Cu+Ni)/15 ≤ 0.56%) to ensure weldability and toughness, while maintaining high strength through optimized alloy composition and thermomechanical processing, achieving yield strength ≥600 MPa with yield ratio ≤0.78, thereby improving building safety
Solution Approach 2:
The patent utilizes phase transitions during thermomechanical processing: austenite formation during heating (1200-1250°C), austenite-to-ferrite transformation during cooling, and austenite-to-pearlite/bainite transformation at controlled rates (2-5°C/s). These phase transitions create a refined microstructure with high strength and improved safety performance
3Strength
If high-strength steel bars are produced with specific alloy composition, then yield strength increases to ≥600 MPa, but manufacturing complexity increases
Solution Approach 1:
The patent manages manufacturing complexity by establishing clear parameter ranges for alloy composition (C: 0.15-0.32%, Si: 0.10-0.50%, Mn: 1.00-2.50%, Cr: 0.30-0.60%, Mo: 0.10-0.30%, Ni: 0.10-0.30%, V: 0.02-0.80%, Nb: 0.01-0.10%, Ti: 0.01-0.10%, Al: 0.01-0.10%) and processing parameters (heating temperature 1200-1250°C, rolling temperature 850-950°C, cooling rate 2-5°C/s), making the complex manufacturing process controllable and repeatable
Solution Approach 2:
The patent merges multiple functions into the alloying system: Si and Mn provide solid solution strengthening and deoxidation; Cr, Mo, and Ni enhance hardenability and toughness; V, Nb, and Ti provide precipitation hardening; Al provides deoxidation and grain refinement. This merging of multiple strengthening mechanisms into a coordinated alloying and processing system achieves high yield strength (≥600 MPa) while managing manufacturing complexity through integrated process design
Data Source
AI summary
Disclosed are a high-strength steel bar and a production method therefor. The high-strength steel bar comprises, by mass percentage, the following chemical components: C: 0.15-0.32%, Si+Mn: 0.5-1.9%, Mn+Cr+Mo+Ni: 1.1-2.1%, V: 0.02-0.8%, at least one of Nb, Ti and Al: 0.01-0.3%, and the balance of Fe and inevitable impurities; wherein Mn=(2.5-3.5)Si, and a carbon equivalent satisfies Ceq=C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15≤0.56%.