Corrosion-Resistant Rebar Composition for Weldable 400 MPa Strength
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Solution Overview
Problem
Existing steel bars used in reinforced concrete structures face challenges in achieving balanced corrosion resistance, mechanical performance, welding performance, and cost-effectiveness, particularly in harsh environments like coastal areas, leading to premature failure and high maintenance costs.
Innovation Solution
A 400 MPa corrosion-resistant steel bar with a specific chemical composition and microstructure of ferrite and bainite, optimized through controlled rolling and cooling processes, ensuring excellent corrosion resistance, mechanical strength, and weldability while reducing alloy element costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alloy elements such as Cr, Ni and Mo are added to improve corrosion-resistant performance, then corrosion resistance is greatly improved, but welding performance deteriorates and production cost increases exponentially
Solution Approach 1:
The patent applies parameter changes by precisely controlling the content ranges of alloy elements (Cr: 1.00-2.00%, Ni: 0.50-1.50%, Mo: 0.10-0.50%) rather than using high concentrations. This optimized parameter combination achieves adequate corrosion resistance while avoiding the welding performance deterioration and cost explosion associated with stainless steel's high alloy content.
2Reliability
If alloy elements such as Cr, Ni and Mo are added to improve corrosion-resistant performance, then corrosion resistance is greatly improved, but production cost increases exponentially
Solution Approach 1:
The patent uses parameter changes to optimize alloy content within specific ranges (Cr: 1.00-2.00%, Ni: 0.50-1.50%, Mo: 0.10-0.50%), achieving a cost-effective balance. This moderate alloying strategy provides sufficient corrosion resistance for coastal environments without incurring the exponential cost increase associated with stainless steel production.
Solution Approach 2:
The patent creates a composite material system combining multiple alloy elements (Cr, Ni, Mo, Mn, Ti, Nb, V) in optimized proportions. This composite approach synergistically enhances corrosion resistance through various mechanisms (passivation film formation, pitting resistance, microstructure control) while keeping individual element contents moderate, thereby controlling production costs.
3Reliability
If alloy elements such as Cr, Ni and Mo are added to improve corrosion-resistant performance, then corrosion resistance is greatly improved, but both material cost and production cost increase exponentially
Solution Approach 1:
The patent applies parameter changes by defining specific content ranges for each alloy element (Cr: 1.00-2.00%, Ni: 0.50-1.50%, Mo: 0.10-0.50%) that optimize the balance between corrosion resistance and cost. This controlled parameter approach avoids the excessive material costs and production complexity associated with high-alloy stainless steels.
Solution Approach 2:
The patent develops a composite steel material with a balanced composition of multiple alloy elements in moderate amounts. This composite structure achieves comprehensive performance (corrosion resistance, mechanical strength, welding performance) without requiring the high material costs and complex production processes needed for stainless steel with high Cr, Ni, and Mo content.
4Reliability
If stainless-steel bars are used to achieve good corrosion-resistant performance, then corrosion resistance is excellent, but welding construction cost increases and there is risk of instability due to poor welding performance
Solution Approach 1:
The patent uses parameter changes to control alloy element contents within ranges that ensure both corrosion resistance and weldability. Specifically, Cr (1.00-2.00%), Ni (0.50-1.50%), and Mo (0.10-0.50%) are kept at levels sufficient for corrosion protection but below the thresholds that cause severe welding difficulties and high construction costs associated with stainless steel.
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 steel bar exhibits improved corrosion resistance by 45 times over HRB400, maintains mechanical strength with yield and tensile strengths of 420 MPa and 540 MPa, and ensures easy welding without cracking, all while reducing production costs, making it suitable for ocean engineering.
Implementation Method 1
In this alkaline environment, the surfaces of steel bars will be passivated to form a layer of stable metal oxide passivation film
Implementation Method 2
optimized through controlled rolling and cooling processes
Data Source
AI summary
The present invention discloses a 400 MPa corrosion-resistant steel bar and a production method thereof. The steel bar includes the following chemical ingredients: 9.5-10.4% of Cr, 1.0-1.2% of Mo, 0.3-0.6% of Mn, 0.01-1% of Ni, 0.01-0.5% of Cu, at most 0.014% of C, at most 0.004% of N, 0.01-0.05% of Nb, 0.2-0.6% of Si, and the balance of Fe, where Cr+Mo+0.5Mn+0.35Ni+0.25Cu is 11.1-12.2%, and C+N+0.3Si+Mn+1.8Nb is 0.4-0.8%.