ISO 4986:2020

Overview

ISO 4986:2020 - "Steel and iron castings - Magnetic particle testing" specifies a standardized method for magnetic particle testing (MPT) of ferro‑magnetic steel and iron castings and provides acceptance criteria based on severity levels. It applies to all ferro‑magnetic castings regardless of moulding method and defines ferro‑magnetic as magnetic induction > 1 T at a magnetic field strength of 2.4 kA/m. The standard covers which areas of a casting are to be tested and the percentage of castings to inspect.

Key topics and technical requirements

• Scope and applicability: Applies only to designated areas and specified sampling rates for castings; independent of moulding process.
• Acceptance criteria: Uses severity levels tied to the nature, area and dimensions of discontinuities. Distinguishes:
  • Non‑linear indications (SM) - length < 3× width; clusters defined when ≥3 indications are within 2 mm.
  • Linear (LM) and aligned (AM) indications - length ≥ 3× width; aligned indications treated as a single linear indication when spacing is less than the longest indication.
• Operating mode: Default magnetization in two perpendicular directions (per ISO 9934‑1); one‑direction testing allowed if stress direction is known.
• Operator qualification: Personnel must be qualified per ISO 9712 (or equivalent) - qualification level agreed between purchaser and manufacturer.
• Surface preparation: Surfaces must be clean and may be shot‑ or sand‑blasted, ground, or machined to reveal small indications; painting for contrast is permitted. Annex A gives recommended surface finishes.
• Viewing conditions: Tests performed unaided or up to 3× magnification under viewing conditions specified in ISO 3059.
• Reporting and demagnetization: Includes requirements for post‑test cleaning, demagnetization (residual field limits), and test report contents (Annex D model report).

Practical applications and users

• Who uses ISO 4986:
  • Foundries and casting manufacturers
  • NDT technicians and inspectors
  • Quality assurance and inspection engineers
  • Procurement and purchaser organizations specifying acceptance criteria
• Typical uses:
  • Routine acceptance testing of steel and iron castings
  • Specification of inspection sampling, test method (wet, dry, fluorescent), and severity levels in purchase orders
  • Providing consistent criteria for acceptance/rejection and for dispute resolution using tabulated severity limits and reference figures

Related standards

• ISO 9934‑1 - Magnetic particle testing - General principles
• ISO 9712 - Qualification and certification of NDT personnel
• ISO 3059 - Viewing conditions for penetrant and magnetic particle testing
• ISO 4990 - Steel castings - General technical delivery requirements

ISO 4986:2020 is a practical, industry‑focused MPT standard that helps suppliers and purchasers agree clear testing methods, operator qualifications, acceptance criteria (SM, LM, AM), and reporting for ferro‑magnetic steel and iron castings.