The ongoing exploration and development of deeper offshore reservoirs has necessitated the development of higher strength materials able to handle more elevated burst and collapse pressures, temperatures, and partial pressures of hydrogen sulfide. However, within the industry specifications, API 5CRA/ISO 13680 and NACE MR0175/ISO 15156, there has been little advancement of higher strength tubular products used for casing, tubing, coupling stock, and accessories. For sour service, API 5CRA/ISO 13680 currently limits these products to grades 110 & 125.
Alloy 625, also known as Inconel 625, is a superalloy renowned for its exceptional corrosion resistance and high strength in extreme environments. Its unique chemical composition, primarily composed of nickel, chromium, and molybdenum, makes it invaluable in industries such as oil & gas, marine, chemical processing, and aerospace.
Alloy 625 is available in two grades: Grade 1 and Grade 2, with similar basic properties, but differing heat-treatment processes tailoring them for distinct applications. In this article, we’ll delve into Alloy 625 Grade 2, how it differs from Grade 1, and its critical applications, focusing especially on catalyst tubes for hydrogen dissociators and other demanding industrial uses.
Alloy 625 Grade 1 is solution-annealed, providing excellent oxidation and corrosion resistance across a range of environments. It’s widely used in applications requiring flexibility, strength, and corrosion resistance at elevated temperatures up to 1100F.
Conversely, Alloy 625 Grade 2 undergoes a higher temperature solution anneal heat treatment which enhances creep and stress rupture resistance, making it suitable for high-pressure and high-stress applications where durability is critical. The key differences between the two grades are as follows:
Condition | Tensile Strength | Yield Strength | Elongation |
minimum, ksi | minimum, ksi | minimum, % | |
Grade 1 | 120 | 60 | 30 |
Grade 2 | 100 | 40 | 30 |
Alloy 625 Grade 2 tubes find their place in several industries, often where extreme temperatures, pressures, and corrosive environments are present. Some of the most important applications include:
The manufacturing process for Alloy 625 Grade 2 tubes involves several critical steps, including melting and casting, forging or extrusion, piercing and tube forming, heat treatment, and surface finishing. The heat treatment process in Grade 2 is particularly important, as it makes the alloy more suitable for demanding high-temperature applications such as catalyst tubes in hydrogen dissociators. CRA utilizes a cold-pilger manufacturing process in the production of Alloy 625 grades 1 and 2. The main benefit of cold-pilgering is the resulting cold-worked strength, otherwise lost with annealing.
Alloy 625 Grade 2 is a high-performance material widely used in industries that demand high temperature strength, corrosion resistance, and durability. Its ability to withstand extreme temperatures, resist hydrogen embrittlement, and perform reliably in corrosive environments makes it the preferred choice for applications such as catalyst tubes in hydrogen dissociators, power generation, and chemical processing. By combining these properties, Alloy 625 Grade 2 continues to play a critical role in advancing technologies in high-demand industries.
CRA’s mill specializes in delivering manufacturing solutions for non-standard situations that demand quick turnaround times, customized sizes, specifications, lengths, and production runs. Whether it’s for chemical processing, the Department of Defense, or the oil and gas sector, our distinctive approach to producing Alloy 625 pipe tailored to your precise requirements is aimed at supporting all industries with critical applications.
*While every effort has been made to ensure the accuracy of the above review, assessment, conclusions, and report, the appropriateness of their application and their interpretation remain the sole responsibility of the user.
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