ISO 9649:2023

Overview

ISO 9649:2023 - Metallic materials - Wire - Reverse torsion test defines a standardized method to determine the ability of metallic wire (diameter 0.3 mm to 10.0 mm inclusive) to undergo plastic deformation under alternating torsion. The reverse torsion test is used primarily to detect surface defects and to assess wire ductility and overall quality. This third edition (2023) updates the 2016 version and clarifies test reporting and certain procedural details.

Keywords: ISO 9649:2023, reverse torsion test, metallic wire testing, wire ductility, surface defect detection, wire quality control.

Key topics and technical requirements

• Scope: Applies to round wires with nominal diameters from 0.3 mm to 10.0 mm for detecting surface defects and assessing ductility.
• Test principle: Twist the specimen a specified number of full turns (360° per turn) in one direction, then the specified number in the opposite direction.
• Test piece preparation:
  • Wire must be as straight as possible; straightening is allowed provided the surface is not damaged and no twisting is introduced.
  • Wires with local kinks or sharp curvature must not be used.
• Free length between grips (L): Specified as a function of nominal diameter (d):
  • 0.3 ≤ d < 1.0 mm: L = 200·d
  • 1.0 ≤ d < 5.0 mm: L = 100·d
  • 5.0 ≤ d ≤ 10.0 mm: L = 50·d
  • Shorter lengths may be agreed by supplier and purchaser (see standard).
• Equipment requirements:
  • Rigid, abrasion‑resistant grips aligned on the same axis; one grip rotates, the other remains fixed (except for torque measurement).
  • Machine must allow axial length change during deformation and permit application of a tensile stress (up to 2% of nominal tensile strength when used to keep specimen straight).
  • Adjustable rotation speed and turn-count recording; protective shield to contain fragments if wire fails.
• Test conditions: Ambient 10 °C–35 °C (or controlled 23 ± 5 °C where required).
• Operating parameters:
  • Rotation speed ≤ 1 turn/s (≤ 0.5 turn/s for d ≥ 5 mm).
  • Number of turns in each direction (N1, N2) are specified in the relevant product or sector standards.
• Acceptance and validity: Visual examination for surface defects, cracks, configuration and failure. If failure occurs within 2·d of the grip before reaching required N, the test is invalid and must be repeated.
• Reporting: The standard specifies required test report items (reference to ISO 9649, material ID, diameter, preparation, test conditions, N1/N2, and visual results).

Applications and users

• Practical uses: incoming quality control, production testing, material qualification, failure analysis and R&D for wire products.
• Typical users: wire manufacturers, spring and fastener producers, quality assurance laboratories, material testing labs, and end‑users requiring wire ductility and surface integrity verification.
• Industries: automotive, aerospace, construction, electronics, springs and fasteners, and any sector relying on high‑quality metallic wire.

Related standards

• ISO 8458-3 referenced as an example application (steel wire for mechanical springs).
• ISO/TC 164 (Mechanical testing of metals) provides the technical committee context.

This concise summary helps procurement, QA teams, and test laboratories implement ISO 9649:2023 for consistent reverse torsion testing and reliable detection of surface defects and ductility characteristics in metallic wire.