ISO 6931-2:2005

Overview

ISO 6931-2:2005 - "Stainless steels for springs - Part 2: Narrow strip" specifies requirements for cold-rolled stainless steel narrow strip intended for springs and spring parts. The standard applies to strip up to and including 3 mm thickness and in rolled widths less than 600 mm, made from stainless steels listed in the standard. It covers classification, designation, delivery conditions, chemical and mechanical requirements, surface and technological properties, and inspection/testing rules for spring-grade narrow strip.

Key topics and requirements

• Scope and classification
  • Applies to cold-rolled narrow strip for springs, classified by structure: austenitic, ferritic, martensitic, and precipitation‑hardening steels.
• Designation and traceability
  • Steel names and numbers follow ISO/TS 4949 and ISO/TS 15510 line numbers.
• Information purchaser must supply
  • Mandatory order data: quantity, product form (strip or cut length), dimensional standard (ISO 9445), thickness/width/length and tolerances, internal coil diameter, steel name/number, delivery condition, and type of inspection certificate (ISO 10474).
• Delivery forms and edges
  • Delivered as coils, spools, or cut lengths; edges typically slit but mill, machined, deburred, or special edges can be specified.
• Delivery conditions
  • Various temper/delivery conditions are defined (examples in the standard, e.g., cold-worked conditions such as “+C” with surface states like 2H). Purchaser must specify tensile strength or hardness ranges.
• Chemical and mechanical requirements
  • Chemical composition limits are specified (cast analysis and allowable deviations for product analysis). Tensile strength and hardness ranges are defined for spring-hard rolled strip; allowable coil-end variations are set.
• Technological and surface properties
  • Bending ability guidance, permitted surface finishes per ISO 16143-1, and allowance for oil films from cold rolling. Visible cracks are not permitted.
• Inspection and testing
  • Defines scope of inspection documents (ISO 10474), sampling and test methods, and options for additional tests (internal soundness, flatness, coil set).

Practical applications

• Use for production and procurement of spring strip used in clips, flat springs, contacts, vibration dampers and other spring parts exposed to corrosive environments or slightly elevated temperatures.
• Ensures consistent material performance, dimensional accuracy and traceability for high-duty spring components.

Who uses this standard

• Spring manufacturers and designers
• Stainless steel strip producers and processors
• Quality and inspection engineers
• Purchasing and specification writers in automotive, HVAC, electronics, medical devices and general engineering sectors

Related standards (referenced)

• ISO 9445 (dimensions/tolerances for rolled strip)
• ISO 10474 (inspection documents)
• ISO/TS 15510 (stainless steel chemical composition)
• ISO 16143-1 (surface definitions)

Keywords: ISO 6931-2, stainless steels for springs, narrow strip, cold-rolled strip, spring strip, stainless steel springs, ISO standard, mechanical properties, chemical composition, inspection.