Steel Plate HIC Resistance via Bubble Control
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Solution Overview
Problem
Existing methods for improving hydrogen-induced cracking (HIC) resistance in steel plates and pipes do not adequately address the issue of uncompressed bubbles in the steel material, leading to insufficient suppression of HIC, as they fail to consider the size and presence of bubbles.
Innovation Solution
Control the chemical composition of steel plates within specific ranges for Ca, S, and O, and manage internal defects to ensure the area ratio of defective regions is minimal, thereby enhancing HIC resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of Ar gas blown into molten steel is controlled to reduce uncompressed bubbles, then HIC resistance is improved, but existing methods fail to adequately control the size and presence of remaining bubbles
Solution Approach 1:
The invention changes the parameters for controlling Ar gas bubbles by specifying not only the amount of Ar gas (5-15 L/t) but also the pore diameter (30-60 μm) and back pressure (1.4-1.8 kgf/cm²) of the porous brick, thereby achieving precise control over bubble size and distribution in the final steel product
Solution Approach 2:
The invention introduces feedback by establishing a relationship between the porous brick parameters and the resulting bubble characteristics in steel, allowing optimization of the degassing process based on the desired final bubble state in the steel product
2Reliability
If existing methods control Ar gas content in steel material, then some HIC resistance is improved, but they do not consider bubble size leading to insufficient HIC suppression
Solution Approach 1:
The invention transitions from merely controlling Ar gas content to controlling multiple parameters including pore diameter (30-60 μm) and back pressure (1.4-1.8 kgf/cm²) of the porous brick, which directly influence the size and distribution of bubbles in the steel product
Solution Approach 2:
The invention performs preliminary action by controlling the bubble formation process during steelmaking through specific porous brick parameters, ensuring that bubbles in the final steel product are within acceptable size limits before the steel is processed further
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 approach effectively improves HIC resistance by controlling the chemical composition and internal defects, reducing the likelihood of crack formation and hydrogen accumulation, resulting in steel plates and pipes with superior resistance to hydrogen-induced cracking.
Implementation Method 1
Ar-gas uncompressed bubbles in the steel material which would form accumulation and segregation zones
Implementation Method 2
hydrogen penetrates into a steel plate from its surface layer part due to a corrosion reaction with the hydrogen sulfide
Data Source
Figure 1~2
AI summary
Disclosed is a steel plate containing: C: 0.02 to 0.15% by mass, Si: 0.02 to 0.50% by mass, Mn: 0.6 to 2.0% by mass, P: more than 0% by mass and 0.030% by mass or less, S: more than 0% by mass and 0.003% by mass or less, Al: 0.010 to 0.080% by mass, Ca: 0.0003 to 0.0060% by mass, N: 0.001 to 0.01% by mass, O: more than 0% by mass and 0.0045% by mass or less, with the balance being iron and inevitable impurities, wherein a Ca content, a S content and an O content satisfy the following formulae (1) and (2): 3.0≤Ca/S Ca−1.25×S/O≤1.80 where [Ca], [S] and [O] are contents (% by mass) of Ca, S and O respectively, and wherein an area ratio of a part that has a defect echo height of 20% or more is 0.05% or less.