How to Choose the Base Steel for PTFE-Lined Tower Sections?

The selection of the base steel for PTFE-lined tower sections requires comprehensive consideration of three main factors: media characteristics, operating conditions, and structural requirements. For conventional corrosive environments, Q235B or Q345R carbon steel is an economical and practical choice, but the integrity of the lining must be ensured to prevent the base material from contacting the media. For highly corrosive conditions, 316L stainless steel should be used as the base material, with a pitting resistance equivalent (PREN) greater than 35 to resist chloride ion penetration. High-pressure tower sections (design pressure > 2.5 MPa) are preferably made of 16MnDR low-alloy steel, with normalizing treatment to refine the grain and improve toughness. For low-temperature applications (< -20℃), austenitic stainless steel or nickel-based low-temperature steel must be used to prevent cold brittle fracture.

In addition to meeting strength calculation requirements, the steel thickness design should include an additional 2-3 mm corrosion allowance. For vibration applications, a wall thickness of not less than 12 mm is recommended to suppress resonance. Weldability is a key consideration. For carbon steel, the carbon equivalent must be controlled (CE≤0.43%), and for stainless steel, ultra-low carbon (C≤0.03%) grades should be selected to avoid intergranular corrosion. Strict surface treatment of the substrate is required, including sandblasting to Sa2.5 grade (roughness 50-75μm) to enhance lining adhesion, and grinding of edges to a rounded transition with R≥5mm. Special structural parts such as flange necks require radiographic testing (RTⅡ grade), and butt welds require 99.99% penetrant testing (PT). Economic evaluation should consider the entire life cycle; although the initial cost of a stainless steel substrate is higher, it can reduce maintenance costs and unexpected downtime losses.