ERW Reel-Lay Steel Pipe Seam Layout for Buckling Resistance
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Solution Overview
Problem
ERW steel pipes used in reel-lay installation of submarine pipelines face issues with high yield ratio and low uniform elongation due to processing strains during pipe formation, leading to increased risk of local buckling and fracture when subjected to compressive and tensile strains during spooling.
Innovation Solution
The ERW steel pipes are joined in the longitudinal direction with girth welds, where the seam position of one pipe faces an area from the 2 o'clock to 4 o'clock or 8 o'clock to 10 o'clock cross-sectional positions of adjacent pipes, optimizing tensile characteristics to reduce axial strains and enhance buckling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ERW steel pipes are used to reduce production cost, then manufacturing cost is reduced, but the pipes exhibit high yield ratio and low uniform elongation due to processing strains
Solution Approach 1:
The patent applies parameter changes by controlling the chemical composition parameters (C: 0.05-0.15%, Si: 0.10-0.50%, Mn: 1.50-2.50%, Ti: 0.010-0.050%, Nb: 0.010-0.050%, V: 0.010-0.100%) and processing parameters (heating temperature 1050-1300°C, cumulative reduction ratio 50% or more, cooling speed 5-60°C/s) to achieve the desired balance between yield ratio and uniform elongation in ERW steel pipes
Solution Approach 2:
The patent creates a composite microstructure consisting of bainitic ferrite as the main phase and massive martensite as the second phase, where the two phases work together to provide both strength and ductility, resolving the contradiction between high yield ratio and low uniform elongation
2Strength
If processing strain is applied during pipe formation to strengthen the pipe, then strength is improved, but yield ratio increases and uniform elongation decreases
Solution Approach 1:
The patent optimizes the processing parameters including heating temperature (1050-1300°C), cumulative reduction ratio (50% or more), and cooling speed (5-60°C/s) to control the degree of processing strain, achieving sufficient strength while maintaining adequate uniform elongation
Solution Approach 2:
The patent creates local quality differences by forming a specific microstructure with bainitic ferrite and massive martensite phases distributed throughout the pipe wall, providing localized areas of high strength and ductility to balance the overall mechanical properties
3Strength
If high strength ERW steel pipes are used for reel-lay installation, then buckling resistance should be improved, but the high yield ratio makes the pipes susceptible to local buckling and fracture during spooling
Solution Approach 1:
The patent employs a composite microstructure with bainitic ferrite (providing ductility) and massive martensite (providing strength) to achieve a balance between buckling resistance and resistance to local buckling/fracture, resolving the contradiction through phased material design
Solution Approach 2:
The patent controls chemical composition parameters (particularly C, Si, Mn, Ti, Nb, V) and processing parameters (heating temperature, reduction ratio, cooling speed) to achieve the optimal yield ratio range (0.85-0.95) that provides sufficient buckling resistance while preventing local buckling and fracture during spooling operations
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
This configuration significantly reduces the risk of buckling and fracture by maintaining axial strains within a safe range, even when the high-Y/T low-uEl regions are at the inner or outer sides during spooling, resulting in a long steel pipe with high buckling resistance without requiring special facilities or heat treatments.
Implementation Method 1
the steel having a composition containing, on a mass percent basis, C: 0.03-0.10%, Si: 0.10-0.50%, Mn: 1.4-2.2%, P: 0.025% or less, S: 0.005% or less, Al: 0.005-0.10%, Nb: 0.02-0.10%, Ti: 0.001-0.030%, Mo: 0.05-0.50%, Cr: 0.05-0.50%, and Ni: 0.001-1.00%, with the balance being Fe and unavoidable impurities, is heated to a heating temperature of 1050-1300°C and then subjected to rough rolling to obtain a sheet bar
Implementation Method 2
The sheet bar is subjected to finishing rolling in which a cumulative reduction ratio is 50% or more in a temperature range of 930°C or less to obtain a hot-rolled steel sheet
Implementation Method 3
In the cooling step, cooling of the hot-rolled steel sheet is started immediately after the finishing rolling so that an average cooling speed is 5-60°C/s in a central portion in the thickness direction and that the temperature is reduced to a cooling stop temperature range of Bs point to 450°C
Implementation Method 4
In the coiling step, the hot-rolled steel sheet is wound in the shape of a coil, retained for 60 seconds or more and less than 600 seconds, and then cooled
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A long steel pipe for reel-lay installation formed of electric resistance welded (ERW) steel pipes and having high buckling resistance and a method for producing the long steel pipe for reel-lay installation are provided. The long steel pipe is formed by successively butt-joining longitudinal ends of the ERW steel pipes by girth welding so that girth welds are formed. The ERW steel pipes are successively butt-joined in the pipe longitudinal direction such that the 0 o'clock cross-sectional position or the 6 o'clock cross-sectional position of one of adjacent ERW steel pipes faces an area from the 2 o'clock cross-sectional position to the 4 o'clock cross-sectional position or an area from the 8 o'clock cross-sectional position to the 10 o'clock cross-sectional position of the other of the adjacent ERW steel pipes. Accordingly, even when the long steel pipe is spooled onto a reel for reel-lay installation such that the 0 o'clock cross-sectional position (seam) or the 6 o'clock cross-sectional position thereof, at which the long steel pipe has high-yield-ratio low-uniform-elongation tensile characteristics, is at the reel inner side (intrados) or the reel outer side (extrados), large axial strains that cause local buckling or fracture are not generated. Thus, a long steel pipe for reel-lay installation with high buckling resistance and a low risk of buckling or fracture and a method for producing the long steel pipe for reel-lay installation are provided.