ASTM B677 UNS N08904 Solution Treated Nickel Alloy Seamless Tube for Corrosion Resistance

ASTM B677 seamless pipe and tube is designed for general corrosive service applications where conventional austenitic stainless steels may not provide adequate resistance to acids, chlorides, pitting, crevice corrosion, or stress-corrosion cracking. The product is manufactured through seamless cold-working or hot-finishing processes and is supplied in the solution-treated condition.

Important Procurement Note: The specific ASTM B677 edition must be clearly stated on purchase orders. UNS N08904 was included in earlier ASTM B677 editions but was subsequently transferred to ASTM A269 and ASTM A312/A312M. Current ASTM B677-26 covers UNS N08034, N08354, and N08935. Therefore, UNS N08904 or N08925 should not be ordered simply as "current ASTM B677" without identifying the required edition or corresponding current product specification.

• High alloy content for aggressive corrosion environments: UNS N08904 contains 23.0-28.0% Ni, 19.0-23.0% Cr, 4.0-5.0% Mo, and 1.0-2.0% Cu. UNS N08925 raises molybdenum to 6.0-7.0% and contains 24.0-26.0% Ni, providing substantially higher alloy content than standard 300-series stainless steels.
• Controlled low-carbon chemistry: UNS N08904 and UNS N08925 are limited to 0.020% maximum carbon, important for maintaining corrosion resistance after solution treatment and reducing susceptibility to chromium-depleted regions.
• Higher strength in solution-annealed condition: Historical ASTM B677 requirements specify minimum tensile strength of 490 MPa for UNS N08904 and 600 MPa for UNS N08925.
• Solution-treated delivery condition: ASTM B677-23 recommends 1100-1150°C for UNS N08925 and N08926 followed by water quenching or rapid cooling.
• 100% pipe/tube integrity testing: Each finished pipe or tube undergoes either hydrostatic testing or nondestructive electric testing according to ASTM B829.

We address the frequent procurement problem of specifying valid UNS grades against incorrect ASTM B677 editions. For each order, we verify material designation, ASTM standard number, standard year, product form, heat number, dimensions, heat-treatment condition, and inspection requirements before production, reducing certification errors.

For high-Ni/high-Mo corrosion-resistant tubing, proper heat treatment is crucial. We maintain production control through heat-number traceability, ladle/product chemical analysis, documented final solution treatment, positive material identification when specified, and EN 10204 3.1 inspection certificates.

We clearly define testing requirements, including whether testing applies to lot samples or every finished tube. Purchase specifications can define eddy-current or ultrasonic examination, dimensional tolerances, surface conditions, end preparation, and purchaser-witness inspection before production begins.

A specific application for UNS N08904 or higher-alloy UNS N08925 seamless tubing is the tube bundle of a sulfuric-acid process heat exchanger. The high nickel, chromium, molybdenum, and copper contents provide greater resistance to acid attack and localized corrosion than conventional 304 or 316-series stainless steel in suitable process conditions.