Composite Pipe Lining for Sodium Hydroxide Corrosion Resistance
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Solution Overview
Problem
Current pipelines used in water supply plants, particularly those exposed to sodium hydroxide, face corrosion issues when made from carbon steel and are costly and difficult to manufacture when made from 304 and 316L stainless steel.
Innovation Solution
A pipe design featuring a corrosion-resistant layer with specific chemical element compositions, including Fe, C, Si, Mn, Ni, Cr, Mo, N, and Ti, applied to a carbon steel base layer, enhancing both corrosion resistance and mechanical properties while reducing material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon steel pipes are used, then manufacturing cost is low, but corrosion resistance to sodium hydroxide is poor
Solution Approach 1:
The patent applies composite material principle by combining carbon steel base layer with a corrosion-resistant layer containing specific alloying elements (Cr: 16-19%, Mo: 2-3.5%, Ni: 8-14%, Ti: 0.01-0.2%, N: 0.02-0.2%). This composite structure provides both the mechanical strength of carbon steel and the corrosion resistance of the alloyed surface layer, effectively resisting sodium hydroxide corrosion while maintaining cost-effectiveness.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the corrosion-resistant layer, including the inequality Cr+2.8×Mo+16×N+2×Ti≥22.0%. By optimizing these compositional parameters, the material achieves enhanced corrosion resistance to sodium hydroxide while maintaining manufacturing feasibility and cost efficiency.
2Reliability
If 304 and 316L stainless steel are used, then corrosion resistance to sodium hydroxide is improved, but manufacturing cost increases and mechanical strength decreases
Solution Approach 1:
The patent applies local quality principle by creating a corrosion-resistant layer only on the surface of the carbon steel base, rather than using entirely expensive stainless steel. The surface layer contains high concentrations of Cr (16-19%), Mo (2-3.5%), and other alloying elements to provide localized corrosion resistance, while the bulk carbon steel structure maintains high mechanical strength and low cost.
Solution Approach 2:
The patent combines carbon steel base material with an alloyed corrosion-resistant surface layer, creating a composite structure that achieves both high strength and corrosion resistance. This composite approach avoids the need for expensive 304/316L stainless steel while maintaining protective performance against sodium hydroxide.
3Object-affected harmful factors
If 304 and 316L stainless steel are used, then corrosion resistance is improved, but material cost and processing difficulty increase
Solution Approach 1:
The patent applies local quality by providing corrosion protection only where needed - on the inner surface exposed to sodium hydroxide - rather than throughout the entire pipe structure. The carbon steel base material remains unchanged in the bulk, maintaining its excellent weldability and machinability, while the surface layer provides localized corrosion resistance.
Solution Approach 2:
The patent uses a relatively thin corrosion-resistant layer (surface treatment) rather than expensive bulk stainless steel. This surface layer provides the necessary corrosion protection, while the majority of the pipe structure uses economical carbon steel that is easy to manufacture and process.
Data Source
AI summary
The present invention discloses a pipe, wherein the pipe has a corrosion-resistant layer and a base layer in the thickness direction, the corrosion-resistant layer being at least disposed on the inner wall of the pipe, and the corrosion-resistant layer further comprises, in addition to Fe and inevitable impurities, the following chemical elements in percentage by weight: 0<C≤0.05%; Si: 0.3-0.6%; Mn: 0.5-2.0%; Ni: 8.00-14.00%; Cr: 16.00-19.00%; Mo: 2.00-3.50%; N: 0.02-0.20%; and Ti: 0.01-0.2%, and Cr, Mo, N, and Ti satisfy the following inequation: Cr+2.8×Mo+16×N+2×Ti≥22.0%. Correspondingly, the present invention further discloses a method for manufacturing the above pipe comprising the steps of: (1) preparing a corrosion-resistant layer slab and a base layer slab; (2) assembling the corrosion-resistant layer slab and the base layer slab to obtain a composite slab; (3) heating and rolling: heating the composite slab at a temperature of 1150-1230° C., wherein a total rolling reduction rate is not lower than 90%, and a finish rolling temperature is not lower than 900° C.; (4) coiling: after water cooling, coiling at a temperature of 650-700° C. to obtain a hot-rolled coil; (5) subjecting the hot-rolled coil to a surface treatment; and (6) making a pipe.