Clad Steel Plate Composition for High Strength and Weldability
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Solution Overview
Problem
Current clad steel plates for natural gas pipelines lack the necessary high strength and toughness to withstand high-pressure operations and corrosive environments, particularly in cold climates, while maintaining weldability and corrosion resistance.
Innovation Solution
A clad steel plate composition with specific alloy elements (C, Si, Mn, P, S, Ni, Cr, Cu, Mo, V, Nb, Ti, Al, Ca, and N) and a production method involving quenching and tempering to achieve a martensite structure and fine grain size, optimizing hardenability and weldability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-strength alloy elements are added to increase steel strength to API X80 grade, then strength is improved, but weldability and toughness in the heat-affected zone deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters (C: 0.20-0.40%, Si: 0.10-0.50%, Mn: 1.30-1.70%, P: 0.015% or less, S: 0.005% or less, Ni: 0.10-0.60%, Cr: 0.10-0.45%, Cu: 0.05-0.40%, Mo: 0.05-0.40%, V: 0.02-0.06%, Nb: 0.03-0.10%, Ti: 0.005-0.025%, Al: 0.020-0.050%, Ca: 0.0010-0.0040%, N: 0.0030-0.0100%) and heat treatment parameters (austenite grain size number 5-11, quenching temperature 900-1100°C, tempering temperature 550-650°C) to achieve API X80 grade strength while maintaining weldability and HAZ toughness. This resolves the contradiction by finding the optimal parameter range that satisfies both strength and weldability requirements simultaneously.
Solution Approach 2:
The patent creates a composite microstructure consisting of martensite as the primary phase with fine-grained morphology. This composite structure at the microscale provides both the high strength required for API X80 grade and the toughness needed for good weldability performance in the heat-affected zone.
2Strength
If quenching and tempering heat treatment is applied to achieve high strength and fine grain structure, then strength and toughness are improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by controlling the austenite grain size before quenching (achieving grain size number 5-11) through composition design and rolling process optimization. This preliminary control of microstructure ensures that the subsequent quenching and tempering operations produce the desired martensitic structure with fine grains, simplifying the overall manufacturing process by pre-establishing favorable conditions for the heat treatment.
Solution Approach 2:
The patent optimizes the heat treatment parameters (quenching temperature 900-1100°C, tempering temperature 550-650°C) to achieve the desired microstructure and mechanical properties with a single pass of quenching and tempering, reducing the number of processing steps while maintaining high strength and toughness.
3Quantity of substance
If alloy composition is optimized for high strength, then material efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific ranges for each alloying element (e.g., C: 0.20-0.40%, Si: 0.10-0.50%, Mn: 1.30-1.70%, Ni: 0.10-0.60%, Cr: 0.10-0.45%, Mo: 0.05-0.40%) that balance strength requirements with manufacturability. These parameter ranges are optimized to achieve API X80 grade strength while allowing sufficient manufacturing tolerance for industrial production, resolving the contradiction between material efficiency and manufacturing precision.
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 clad steel plate with high strength equal to or higher than API X80 grade, excellent low-temperature toughness, and improved weldability, reducing material usage and enhancing operational efficiency in harsh environments.
Implementation Method 1
improving a material strength by solid solution strengthening and precipitation strengthening
Implementation Method 2
improving a material strength by solid solution strengthening and precipitation strengthening
Implementation Method 3
improving hardenability of steel by properly adding alloy elements
Implementation Method 4
a high-strength and high-toughness steel plate which has a desired structure and a desired grain size can be produced by the processing of a non-recrystallized region with controlled rolling and the adjustment of a cooling rate
Implementation Method 5
properly setting heat treatment conditions for quenching/tempering (hereinafter, refining) after rolling
Implementation Method 6
the processing of a non-recrystallized region with controlled rolling
Data Source
AI summary
A base metal for a clad steel plate has a composition which contains 0.05 to 0.10% of C, 0.10 to 0.30% of Si, 1.30 to 1.70% of Mn, 0.015% or less of P, 0.005% or less of S, 0.10 to 0.60% of Ni, 0.10 to 0.45% of Cr, 0.05 to 0.40% of Cu, 0.05 to 0.40% of Mo, 0.02 to 0.06% of V, 0.03 to 0.10% of Nb, 0.005 to 0.025% of Ti, 0.020 to 0.050% of A1, 0.0010 to 0.0040% of Ca and 0.0030 to 0.0100% of N with the remainder including Fe and inevitable impurities and in which the content of Ni, Cr, Cu and Mo satisfies the equation 0.70%≤Ni+Cr+Cu+Mo≤1.30%.