ASTM A456/A456M-24

Overview

ASTM A456/A456M-24 is the standard specification issued by ASTM International for the magnetic particle examination of large forged steel crankshafts. This document sets forth acceptance criteria and examination procedures for crankshafts with main bearing journals or crankpins of 4 inches (100 mm) diameter or larger. It ensures consistency and rigor in nondestructive testing (NDT) methods used for detecting surface and near-surface discontinuities, such as cracks, inclusions, and other defects that could impact the structural integrity and reliability of crankshaft forgings in demanding applications.

The standard covers three classes of forgings, each with varying levels of acceptance severity, and defines inspection areas as major or minor critical. It outlines the classification and treatment of detected indications, as well as requirements for product marking and inspection documentation.

Keywords: ASTM A456/A456M, magnetic particle examination, large crankshaft forgings, nondestructive testing, acceptance criteria, forged steel crankshafts, major critical areas, minor critical areas.

Key Topics

• Scope and Applicability

  • Applies to forged steel crankshafts with main bearing journals or crankpins 4 in. [100 mm] or larger
  • Not intended for continuous grain flow crankshafts (see ASTM A983/A983M and A986/A986M)

• Classification

  • Three classes of crankshaft forgings (Class 1, 2, and 3) defined by increasingly stringent acceptance criteria

• Inspection and Test Procedures

  • Magnetic particle testing performed in accordance with referenced ASTM practices (e.g., A966/A966M, A275/A275M)
  • Distinction between major critical areas (primary load-bearing surfaces) and minor critical areas

• Indication Classification

  • Surface indications such as open cracks, flakes, pipes, and nonmetallic inclusions
  • Differentiation between open (visible or dye-penetrant detected), pinpoint, and non-open indications

• Defect Remediation

  • Procedures for dimpling (material removal) and depressing (flattening or relieving) to treat detected indications
  • Limitation on the size and location of allowable repairs to ensure bearing surface integrity

• Product Marking and Traceability

  • Requirements for marking and documenting crankshafts validated through the specified inspection process

Applications

Compliance with ASTM A456/A456M-24 is vital to manufacturers, quality assurance teams, and purchasers of large forged steel crankshafts used in:

• Industrial Engines: Large engines in marine, power generation, and heavy-duty transportation sectors require crankshafts verified to be free from critical surface and subsurface defects.
• Automotive and Truck Manufacturing: High-performance and commercial engine components must meet strict safety and durability requirements through comprehensive nondestructive examination.
• Railway and Locomotive Applications: Crankshafts in locomotive engines are subject to significant cyclic loads, making magnetic particle inspection essential for reliability.
• Aerospace and Defense: Forgings for aircraft engines or military vehicles are examined to help ensure operational safety under demanding conditions.

By following this standard, stakeholders can reliably assess the structural soundness of crankshaft forgings, reduce failure risks, and maintain regulatory and safety compliance across industries.

Related Standards

For comprehensive quality and safety in crankshaft forging and inspection, several related ASTM standards are referenced and commonly used alongside ASTM A456/A456M:

• ASTM A275/A275M: Practice for Magnetic Particle Examination of Steel Forgings
• ASTM A668/A668M: Specification for Steel Forgings, Carbon and Alloy, for General Industrial Use
• ASTM A788/A788M: Specification for Steel Forgings, General Requirements
• ASTM A966/A966M: Practice for Magnetic Particle Examination of Steel Forgings Using Alternating Current
• ASTM A983/A983M: Specification for Continuous Grain Flow Forged Crankshafts
• ASTM A986/A986M: Specification for Magnetic Particle Examination of Continuous Grain Flow Crankshaft Forgings
• ASTM E1316: Terminology for Nondestructive Examinations
• ASTM E1417/E1417M: Practice for Liquid Penetrant Testing

Selecting and applying the relevant combination of these standards enables organizations to implement a robust quality control process for critical crankshaft forgings.