What Is ASTM B564?
ASTM B564 is the standard specification for nickel alloy forgings, covering products such as flanges, fittings, valves and other forged components made from a range of nickel and nickel-cobalt alloys. The corresponding ASME SB 564 specification applies the same requirements for pressure-vessel and piping applications. Each alloy is classified by its chemical composition, and a chemical analysis of each heat is required to verify that the composition meets the limits of the specified grade. Forgings supplied to ASTM B564 are typically produced by hammering or pressing hot metal into the required shape, followed by heat treatment appropriate to the alloy.
What Is ASTM B564 UNS N06625 Material?
ASTM B564 UNS N06625 specifies forgings made from Inconel 625, a high-strength nickel-chromium-based superalloy known for exceptional resistance to corrosion, oxidation and high temperatures. The alloy combines nickel, chromium, molybdenum and niobium to deliver good performance from cryogenic temperatures up to about 982 °C (1800 °F), and it resists pitting, crevice corrosion and chloride stress-corrosion cracking. These properties make B564 N06625 forgings a standard choice for demanding marine, chemical and aerospace service.
Chemical Composition Requirements
The composition limits of Inconel 625 forgings per ASTM B564 are nickel 58.0% minimum, chromium 20.0-23.0%, molybdenum 8.0-10.0%, iron 5.0% maximum, niobium plus tantalum 3.15-4.15%, cobalt 1.0% maximum, carbon 0.10% maximum, manganese 0.50% maximum and silicon 0.50% maximum. The molybdenum and niobium contents provide solid-solution strengthening and give the alloy its outstanding resistance to localized corrosion in chloride-bearing environments.
Mechanical Properties and Typical Values
Forgings produced to ASTM B564 are required to meet the mechanical requirements of the specification for the relevant product. For Inconel 625 flanges, the minimum tensile strength is 827 MPa (120 ksi), the minimum 0.2% offset yield strength is 414 MPa (60 ksi), and minimum elongation is 30% in a 50 mm gauge length, with hardness typically not exceeding 220 HB. The modulus of elasticity is about 207 GPa, the melting range is approximately 1290-1350 °C, and density is about 8.44 g/cm3. Actual measured values from production heats often exceed these minimums, which is normal for this alloy.
Flange Types and Pressure Ratings
Inconel 625 flanges are manufactured in a wide range of types and facing styles. Under ANSI B16.5, they are available from Class 150 to Class 2500 in sizes from 1/2 inch to 24 inches, with custom sizes up to 60 inches for high-pressure refinery, chemical and offshore systems. Under ANSI B16.47 Series A and B, Class 75-900 flanges cover 26-60 inch large-diameter piping for critical pressure service. For European and international projects, BS 4504 / EN 1092-1 flanges from PN 2.5 to PN 40 cover DN 15 to DN 2000, and DIN flanges from PN 6 to PN 100 cover DN 15 to DN 2000. The correct rating must be selected from the standard based on operating pressure and temperature.
Inconel 625 vs Inconel 725
Inconel 625 offers excellent weldability and corrosion resistance and is ideal for high-temperature, corrosion-critical environments. Inconel 725, while similar in base composition, is age-hardened to develop significantly higher strength and is used in applications such as high-strength fasteners and downhole equipment where superior mechanical properties are required. The choice between the two depends on whether the design is governed by corrosion resistance and fabricability or by mechanical strength.
FAQ
Q: What does ASTM B564 cover?
A: It covers nickel alloy forgings including flanges, fittings, valves and other forged components, with ASME SB564 as the equivalent pressure-vessel specification.
Q: What is UNS N06625?
A: UNS N06625 is the unified numbering system designation for Inconel 625, a nickel-chromium-molybdenum-niobium superalloy.
Q: Which industries use ASTM B564 N06625 flanges?
A: The flanges serve high-pressure, high-temperature and corrosive systems in refineries, chemical plants, offshore platforms, marine equipment and power generation.
Q: What tests are required on B564 forgings?
A: Requirements typically include chemical analysis of each heat, tensile testing, hardness testing and dimensional verification, with additional examination where specified by the purchaser.
Q: Can B564 N06625 flanges be used for seawater service?
A: Yes, Inconel 625 is widely used in marine and subsea applications because of its strong resistance to pitting, crevice corrosion and chloride stress-corrosion cracking.
