Ultra-thin Steel Sheet Composition for Annealing Buckling Control
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Solution Overview
Problem
Conventional steel sheet production methods face challenges in achieving a balance between strength, workability, anti-aging properties, and weld zone integrity, particularly in very thin steel sheets, where heat buckling and high alloying costs are concerns, and existing compositions compromise on productivity and food hygiene.
Innovation Solution
A very thin steel sheet composition with controlled C, N, Ti, Nb, and Al levels, forming specific nitrides and carbides to optimize recrystallization temperature, enhance high-temperature strength, and improve weld zone strength, while maintaining low recrystallization temperature for efficient annealing and reducing heat buckling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ti, Nb, B and other carbonitride-forming elements are added to improve workability and suppress stretcher strain, then anti-aging property is improved, but recrystallization temperature increases causing heat buckling in thin materials
Solution Approach 1:
The patent applies parameter changes by precisely controlling the content ranges of Ti (0.003-0.010%), Nb (0.003-0.010%), and B (0.0005-0.003%), along with their ratios (Ti/Nb ≥ 0.1, Ti+Nb ≤ 0.020%, (Ti+Nb)/B ≥ 0.5). These controlled parameter changes optimize the balance between anti-aging properties and recrystallization temperature, preventing heat buckling while maintaining material performance.
2Productivity
If C and N content are reduced to improve workability and reduce alloying cost, then productivity and cost are improved, but strength and weld zone integrity deteriorate
Solution Approach 1:
The patent uses Ti, Nb, and B as intermediary elements that form carbonitrides to strengthen the matrix and precipitates to reinforce the structure. These intermediaries enable the use of lower C (0.003-0.010%) and N (0.003-0.010%) content while maintaining strength and weld zone integrity, as the carbonitride precipitates compensate for the reduced carbon and nitrogen available for strengthening.
Solution Approach 2:
The patent creates a composite microstructure consisting of a ferritic matrix strengthened by dispersed carbonitride precipitates of Ti, Nb, and B. This composite approach allows reduced C and N content in the base matrix while achieving required strength through the precipitate reinforcement, thereby improving productivity and reducing alloying costs.
3Productivity
If annealing temperature is lowered to improve productivity and reduce heat buckling, then production efficiency is improved, but strength and anti-aging property deteriorate
Solution Approach 1:
The patent applies preliminary action by forming fine carbonitride precipitates of Ti, Nb, and B during controlled cooling after annealing. This preliminary precipitation hardening occurs before final service use, enabling the steel to achieve required strength and anti-aging properties without requiring high annealing temperatures, thus improving productivity while maintaining performance.
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 solution provides a steel sheet with enhanced strength, ductility, and weldability, enabling high-efficiency production with reduced heat buckling and alloying costs, while ensuring food hygiene and productivity.
Implementation Method 1
hold down recrystallization temperature and maintain enhanced high-temperature strength... as the recrystallization temperature of the invention steel is lower than that of conventional steels, low-temperature annealing is possible
Implementation Method 2
with the conventionally utilized Ti- and Nb-added ultra-low carbon steel as a base, the present invention develops further thereon... by further increasing N content and adding abundant Al, precipitates carbides and nitrides in desirable condition
Implementation Method 3
solid solution N present during cold rolling increases accumulation of cold-rolling strain to promote recrystallization during annealing
Implementation Method 4
container manufacturing processes frequently use welding to form the container itself or a handle or the like thereof
Data Source
AI summary
The present invention provides a very thin steel sheet and production method thereof that, in a very thin steel sheet of 0.4 mm or less thickness, enable production at low addition of special elements, simultaneous achievement of both good workability and anti-aging property, and stable passing of even wide coil in a continuous annealing process, which very thin steel sheet and production method are characterized in that it contains, in mass%, C: 0.0004 to 0.0108%, N: 0.0032 to 0.0749%, Si: 0.0001 to 1.99%, Mn: 0.006 to 1.99%, S: 0.0001 to 0.089%, P: 0.001 to 0.069%, and Al: 0.070 to 1.99%; and further one or both of Ti and Nb at Ti: 0.0005 to 0.0804% and Nb: 0.0051 to 0.0894%, within the range of Ti + Nb: 0.0101 to 0.1394%; further satisfies the relationships of N - C ≥ 0.0020%, C + N ≥ 0.0054%, Al / N > 10, (Ti + Nb) / Al ≤ 0.8, (Ti / 48 + Nb / 93) x 12 / C ≥ 0.5, and 0.31 < (Ti / 48 + Nb / 93) / (C / 12 + N / 14) ≤ 2.0; has a balance of iron and unavoidable impurities; and has a thickness of 0.4 mm or less.