ASTM B446-23 PDF

Overview

ASTM B446-23 is the standard specification for rod and bar products made from nickel-chromium-molybdenum alloys with additional elements such as niobium, silicon, or tungsten. These high-performance alloys, designated as UNS N06625, UNS N06219, and UNS N06650, are supplied as hot-worked or cold-worked rod and bar. This specification covers both dimensional tolerances and chemical composition, as well as mechanical properties and permissible finishes for a wide range of industrial and engineering applications where corrosion resistance and high strength are required.

Key Topics

• Material Grades:
  • UNS N06625: Available in three grades:
    • Grade 1 (Annealed): For service up to 1100 °F (593 °C).
    • Grade 2 (Solution Annealed): For service above 1100 °F when resistance to creep and rupture is required.
    • Grade 3 (Solution Annealed and Cold Worked): Employed where higher strength is necessary.
  • UNS N06219 and UNS N06650: These alloys are provided in solution annealed condition only.
• Product Forms:
  • Hot-worked rod and bar
  • Cold-worked rod and bar
• Chemical Composition:
  • Strict limits on elements including carbon, manganese, silicon, phosphorus, sulfur, chromium, niobium (columbium), tantalum, cobalt, molybdenum, iron, aluminum, titanium, copper, nickel, tungsten, and nitrogen.
• Mechanical Properties:
  • Defined tensile strength, yield strength, and elongation requirements, depending on grade and processing.
• Dimensional Tolerances:
  • Specified tolerances for diameter, thickness, width, straightness, and length.
• Heat Treatment:
  • Precise heat treatment procedures based on grade and intended application.
• Product Marking and Certification:
  • Detailed requirements for marking, documentation, and certification for traceability and quality assurance.

Applications

Rod and bar products specified in ASTM B446-23 are widely used in industries that demand superior resistance to corrosion, oxidation, and high-temperature environments, including:

• Chemical Processing: Components for reactors, heat exchangers, and piping requiring resistance to aggressive media.
• Oil and Gas: Parts for deep-sea and sour gas extraction environments, including downhole equipment and valves.
• Power Generation: Used in turbine components and high-stress areas exposed to heat and corrosive gases.
• Aerospace: Engine parts and structural components that must retain strength and integrity at high temperatures.
• Marine Engineering: Shafts and fasteners exposed to saltwater, where both mechanical strength and corrosion resistance are critical.

These applications benefit from the alloys' excellent mechanical and thermal properties, ensuring safety, longevity, and reliable performance.

Related Standards

Several other ASTM standards are referenced within ASTM B446-23 for testing and additional requirements:

• ASTM B443: Specification for plate, sheet, and strip of nickel-chromium-molybdenum alloys.
• ASTM B880: General requirements for chemical check analysis limits for nickel, nickel alloys, and cobalt alloys.
• ASTM B899: Terminology relating to non-ferrous metals and alloys.
• ASTM E8/E8M: Test methods for tension testing of metallic materials.
• ASTM E29: Practice for using significant digits in test data.
• ASTM E1473: Test methods for chemical analysis of nickel, cobalt, and high-temperature alloys.

These related standards provide additional guidance on analysis, terminology, and mechanical testing, ensuring comprehensive control of product quality and consistency.

Keywords: ASTM B446, nickel-chromium-molybdenum alloy, UNS N06625, UNS N06219, UNS N06650, rod and bar specification, corrosion-resistant alloys, high-temperature alloys, industrial standards, ASTM standards