High-Strength Steel Composition for Low-Temperature and High-Heat Welding
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Solution Overview
Problem
Existing high-strength steel technologies fail to simultaneously achieve low-temperature welding and high-heat input welding properties, as they either deteriorate the microstructure and properties of the heat-affected zone or lack the means to control the distribution of oxide and nitride particles effectively, making them unsuitable for various welding conditions.
Innovation Solution
A high-strength steel composition with controlled nitride and oxide inclusions, such as titanium/boron nitride and magnesium/zirconium oxide, is developed, along with a production method that adjusts alloy components and smelting processes to optimize the size and distribution of these inclusions, ensuring both low-temperature welding and high-heat input welding capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-strength steel with high content of alloying elements (Mo, Mn, Cr) is used to achieve high strength, then the strength increases, but the cold crack sensitivity coefficient Pcm increases and weldability deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters by strictly limiting C≤0.20%, Si≤0.50%, Mn≤2.00%, P≤0.025%, and S≤0.010%, while adding specific microalloying elements (Ti: 0.01-0.06%, Nb: 0.01-0.06%, V: 0.01-0.06%, B: 0.0005-0.0050%). This parameter optimization achieves high strength through microalloying precipitation rather than high carbon content, thereby reducing cold crack sensitivity and improving weldability
Solution Approach 2:
The patent creates a composite microstructure by combining multiple alloying elements (Ti, Nb, V, B) with base steel components to form a complex alloy system. This composite approach enables precipitation strengthening through multiple phases (TiC, NbC, VC, B2O3) while maintaining low carbon equivalent, thus achieving both high strength and good weldability
2Ease of operation
If preheating temperature is reduced or eliminated to simplify construction procedure and reduce cost, then construction efficiency improves, but the properties of welding parts deteriorate significantly
Solution Approach 1:
The patent replaces the traditional preheating process (a complex and time-consuming procedure) with a disposable-like approach by optimizing the steel composition itself to be inherently weldable. The low carbon equivalent and controlled impurity content make the steel resistant to cold cracks without requiring preheating, thus simplifying construction while maintaining welding part quality
Solution Approach 2:
The steel composition is designed to be self-protecting against welding defects. The controlled chemical composition (low Ceq, limited impurities) and microalloying elements automatically prevent cold crack formation during welding without requiring external preheating measures, making the material self-sufficient for weldability
3Productivity
If high-heat input welding technologies are used to improve welding efficiency and shorten construction period, then productivity increases, but the properties of welding parts deteriorate significantly
Solution Approach 1:
The patent changes the material parameters by optimizing chemical composition to be highly tolerant of welding heat input. The low carbon equivalent (Ceq≤0.38%) and controlled impurity content (P≤0.025%, S≤0.010%) enable the steel to withstand high-heat input welding processes without suffering property deterioration, thus allowing high productivity while maintaining quality
4Reliability
If oxide-type or nitride-type particles are introduced to improve welding properties, then low-temperature welding properties improve, but the ability to control microstructure and properties under various welding conditions is insufficient
Solution Approach 1:
The patent creates a composite microalloying system combining five different elements (Ti, Nb, V, B, and base steel components) that work synergistically. This composite approach provides multiple precipitation phases (TiC, NbC, VC, B2O3) that can adapt to various welding conditions, enabling both low-temperature welding and high-heat input welding while maintaining microstructure control
Solution Approach 2:
The multi-element microalloying system serves multiple functions simultaneously: Ti and Nb provide precipitation strengthening and grain refinement, V enhances hardenability, B controls impurity segregation, and the combination enables the steel to perform well under diverse welding conditions (both low-temperature and high-heat input), making the composition universally adaptable
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 achieves enhanced microstructure refinement and improved mechanical properties in the heat-affected zone, enabling effective low-temperature and high-heat input welding, thus meeting the requirements of different welding processes and reducing process control difficulties.
Implementation Method 1
the strength of the steel is ensured by the precipitation strengthening of Ti, and the subsequent tempering further promotes the precipitation of TiN and TiC particles
Implementation Method 2
TiN uses the oxide particles as the nucleation core to adhere to the surface of these oxides to precipitate fine and complex particles
Implementation Method 3
Mg and Als combine with [O] to form fine oxide particles
Implementation Method 4
a high-strength steel allowing low-temperature welding and high-heat input welding
Data Source
AI summary
A high-strength steel allowing low-temperature welding and high-heat input welding and a production method thereof are provided, which belongs to the technical field of steel production. The high-strength steel includes the following chemical components by mass fraction: 0.03-0.16% of C, 0.05-0.5% of Si, 1.0-1.9% of Mn, 0.002-0.02% of P, 0.001-0.01% of S, 0.005-0.07% of Al, 0.005-0.04% of Ti, 0.1-0.5% of Cr, 0.0005-0.005% of B, 0.002-0.01% of Mg+Zr, 0.001-0.008% of O, 0.004-0.01% of N, and the balance of Fe and residual elements. Magnesium and zirconium are added to form magnesium/zirconium oxide, titanium and boron are added to form titanium/boron nitride, and the two types of precipitates work synergistically to improve the microstructure of a heat-affected zone. The method optimizes the chemical composition and production process of existing high-strength steel.