Super Duplex 1.4410 Angle Profiles for High-Chloride Paper Mill Environments
Paper manufacturing involves two distinct process zones: the felting zone, where pulp loses water and the wet sheet forms, and the drying zone, where the sheet is dried, smoothed, and wound onto a reel. The drying zone operates in a high-chloride environment, and the small structural corner profiles used in paper roll winding machines in this zone are exposed continuously to the chemically aggressive conditions of the process. A customer in the pulp and paper industry required angle profiles 25×25×3 mm in a material capable of resisting this environment reliably throughout the machine’s service life. Standard austenitic grades were insufficient for the chloride levels present, and super duplex 1.4410 (2507) was specified for its exceptional resistance to pitting, crevice corrosion, and stress corrosion cracking in high-chloride media. Montanstahl produced the sections by laser welding with precisely controlled parameters to maintain both the corrosion performance and the geometric straightness of a very small cross-section.
Why Super Duplex 1.4410 and Not Standard 316L for This Application
The pulp and paper industry uses chlorine-based bleaching agents and process chemicals that create high-chloride conditions across the drying section of the machine. In this environment, standard austenitic grades including 316L are susceptible to pitting corrosion, crevice corrosion, and stress corrosion cracking at operating temperatures, particularly at small section thicknesses where the ratio of surface area to material volume accelerates attack. Super duplex 1.4410 (S32750 / 2507) contains higher levels of chromium, molybdenum, and nitrogen than both standard austenitic and duplex grades, giving it a Pitting Resistance Equivalent Number (PREN) above 40. This places it in a corrosion resistance class that remains stable in the process environments present in paper mill drying zones, where standard grades would require frequent replacement. The dual-phase austenitic-ferritic microstructure also delivers approximately twice the yield strength of 316L, which is relevant for small sections that must carry mechanical loads without deforming. A detailed comparison of duplex and super duplex grades and their applications is available on the Montanstahl blog.
Two Technical Challenges: Weld Zone Integrity and Bar Twist on a 25×25×3 mm Section
Laser welding super duplex stainless steel presents a specific challenge that does not apply to austenitic grades in the same way: heat input during welding alters the austenite-ferrite phase balance in the heat-affected zone, and if not controlled precisely, this phase imbalance reduces the corrosion resistance of the weld zone below the level of the parent material. For a section that is specified in super duplex precisely because of its corrosion resistance, any degradation at the weld line defeats the purpose of the material choice. The second challenge was geometric: at 25×25×3 mm, the section is extremely small (comparable in size to a one-euro coin in cross-section), and the thermal stresses from welding can introduce random twist along the bar length that cannot be corrected mechanically without risking deformation of the section itself. Montanstahl solved both problems by precisely calibrating the laser power and welding speed, reducing heat input to the level where phase balance is maintained while delivering a consistent weld that holds the bar straight across its full length.
Application Context
This project sits within Montanstahl’s Pulp & Paper segment, where laser welded stainless steel angle profiles in duplex and super duplex grades are specified for machine components, structural elements, and wear parts operating in high-chloride process environments. The paper and pulp industry is one of the primary sectors for super duplex 1.4410 because of the combination of chloride exposure, acidic process chemicals, and the long machine service intervals that make corrosion-resistant material selection a direct cost-reduction measure. Montanstahl produces custom laser welded angle profiles in 1.4410 and other duplex grades at any dimension from very small sections up to 1,000 mm height, supplied to pulp and paper machinery manufacturers worldwide.