ISO 2639:2002 is an ISO standard for defining and determining case-hardened depth in steel parts with carburized or carbonitrided hardened cases, using hardness-based evaluation across the case-to-core transition.
This document is listed by ISO as withdrawn, so purchase specs and drawings may instead cite its replacement or an updated regional adoption. If you need help matching a customer callout to the right method and test setup, contact our team.
ISO 2639:2002 — Steels — Determination and verification of the depth of carburized and hardened cases
ISO 2639 is used when a steel component has been case hardened (commonly by carburizing or carbonitriding) and the required deliverable is a quantified case-hardened depth based on a hardness criterion through a cross-section.
Because this standard is withdrawn, many programs treat it as a legacy reference. When it is still cited, edition control and the purchaser’s hardness-depth criterion are critical for consistent results.
Quick Definition
ISO 2639 defines “case-hardened depth” for carburized/carbonitrided steel parts and provides methods to determine and verify that depth using hardness measurements from the surface toward the core.
What This Standard Covers
ISO 2639 focuses on hardness-based determination of case-hardened depth in steel, including how results are compared with a specified depth requirement.
It is written for carburized and carbonitrided cases, and it includes applicability conditions tied to core hardness behavior at a stated distance from the surface (when those conditions are not met, the depth definition is set by special agreement).
Why This Standard Matters in Testing
Case depth is a key acceptance criterion for many heat-treated components because it connects heat-treatment process capability to functional performance (wear resistance, surface durability, and resistance to surface-initiated damage while maintaining a tougher core).
For labs and QA teams, the standard provides a structured way to report case depth in a repeatable manner, minimizing disputes caused by inconsistent hardness traverses, inconsistent measurement spacing, or mismatched hardness scales/test forces.
Common Materials, Product Types, or Applications Covered
ISO 2639 is commonly associated with steel parts that receive carburizing or carbonitriding followed by hardening to produce a hardened surface layer over a lower-hardness core.
Typical product examples: Gears, shafts, bearing-related components, drivetrain parts, and other wear-critical steel components where a specified case depth is part of the purchase requirement.
Common Test or Verification Workflow
Most ISO 2639 workflows are performed as a metallurgical hardness traverse on a prepared cross-section so the hardness gradient can be measured from the surface inward.
Common workflow steps: Section the part or coupon, mount and polish the cross-section, perform Vickers or Knoop hardness indents along a line normal to the surface, determine the depth where the hardness criterion is met, and document the case-depth result for acceptance or process control.
What to align before testing: The cited edition, the required definition/criterion for “case-hardened depth,” the hardness method (e.g., Vickers or Knoop), and any purchaser-defined rules for locations, replicates, and acceptance reporting.
Equipment Commonly Used for This Standard
ISO 2639 typically points to a microhardness-capable hardness testing workflow plus metallographic sample preparation, because case depth is determined from a hardness profile across the case.
Common equipment: Microhardness tester (Vickers and/or Knoop capability), metallographic sectioning saw, mounting system, grinding/polishing equipment, optical microscope or measurement optics integrated with the hardness system, and data capture/reporting software for hardness traverses.
Practical equipment caution: Thin or steep hardness gradients may require careful selection of test force and indentation spacing to avoid overlapping plastic zones and to keep measurements representative of the case layer.
If you are specifying a hardness-tester configuration for case-depth work (loads, indenter options, optics, automation, and reporting), you can request a detailed quote matched to your throughput and documentation needs.
How to Read This Designation or Revision
Standard number: ISO 2639.
Edition/year: ISO 2639:2002 is the commonly cited edition (Edition 3).
Status note: ISO identifies ISO 2639:2002 as withdrawn and indicates a newer ISO document is available for this topic area. If a drawing, control plan, or customer specification cites ISO 2639, confirm whether the legacy reference is required or whether the newer ISO replacement is acceptable.
Related Standards, Methods, or Frameworks
Hardness traverses for case-depth determination are commonly built on standardized hardness methods. ISO 2639 references widely used hardness-test methods (such as Vickers and Knoop) for executing the indent measurements that support the case-depth calculation.
When ISO 2639 is cited on legacy documentation, it is also common to see successor or replacement ISO standards referenced for broader surface-hardened layer thickness determination across multiple hardening processes.
Talk with us about ISO 2639 case-depth testing
If you need to set up or validate a case-depth measurement workflow for carburized or carbonitrided steel (including microhardness selection, optics, and reporting expectations), talk with our team about the quickest path to a compliant, repeatable lab process.