ISO 15787
Technical product documentation — Heat-treated ferrous parts — Presentation and indications
Rules for presenting heat-treated ferrous parts on technical drawings — how to indicate the heat-treatment condition, hardness with tolerance, hardening depth (CHD, SHD, NHD) and the extent of locally hardened zones.
What ISO 15787 specifies
ISO 15787 standardises the heat-treatment note on a drawing so that a heat treater in any country reads it the same way. It prescribes the wording of the condition (using ISO 4885 vocabulary), the hardness indication with scale and tolerance written as a minimum plus a positive tolerance (for example 58 +4 HRC or 700 +150 HV 10), and the hardening-depth indications CHD (case hardening depth, limit 550 HV 1 unless stated), SHD (surface hardening depth for induction and flame hardening, limit 80 % of the minimum surface hardness) and NHD (nitriding hardness depth, limit core hardness plus 50 HV 0.5), each given as a minimum with a plus tolerance, such as CHD 0.8 +0.4. Locally treated zones are shown with a wide dash-dot line along the contour with dimensions for the hardened length and transition zone, and zones that must stay soft are marked.
ISO 15787 types and classes
Every designation the document defines, with the thickness it requires and the tests it imposes.
| Designation | Meaning | Requirement / test |
|---|---|---|
CHD | Case hardening depth for carburized or carbonitrided parts: depth to 550 HV 1 unless another limit is stated; measured per ISO 2639 / ISO 18203; written e.g. "CHD 0.8 +0.4". | Vickers traverse per ISO 18203 / ISO 2639 |
SHD | Surface hardening depth for induction- or flame-hardened parts: depth to 80 % of the specified minimum surface hardness (in HV); written e.g. "SHD 1.5 +1.0". | Vickers traverse per ISO 18203 |
NHD | Nitriding hardness depth: depth to core hardness plus 50 HV 0.5; written e.g. "NHD 0.3 +0.2". | Vickers traverse per ISO 18203 |
Tests and the drawing call-out
Tests the document imposes
- Hardness per ISO 6508-1 (Rockwell), ISO 6507-1 (Vickers) or ISO 6506-1 (Brinell) at the indicated location
- Hardening depth per ISO 18203 (CHD / SHD / NHD) or ISO 2639 (CHD)
- Metallographic check of the hardened-zone extent against the drawing indication when specified
How to cite it
Drawing call-out
INDUCTION HARDENED AND TEMPERED, 58 +4 HRC, SHD 1.5 +1.0, ZONE PER WIDE DASH-DOT LINE (ISO 15787)Angle brackets mark the choices the drawing must make; every finish page shows a completed example.
Heat treatments specified to ISO 15787
| Treatment | Role | Cost |
|---|---|---|
Gas nitriding diffuses nitrogen into finished ferrous parts below the transformation temperature, producing a hard compound layer and diffusion zone without quenching. | Related | $$$$ |
Ferritic nitrocarburizing diffuses nitrogen and carbon into ferrous surfaces below the transformation temperature. | Related | $$$ |
Plasma nitriding uses a glow discharge to clean, heat, and diffuse nitrogen into ferrous surfaces. | Related | $$$$ |
ISO 15787 — frequently asked
Why "58 +4 HRC" instead of "58–62 HRC"?
ISO 15787 writes hardness as a minimum with a plus tolerance to make the acceptance direction explicit and to avoid confusion with dimensional ranges; 58 +4 HRC means 58 to 62 HRC. The same convention applies to depths: CHD 0.8 +0.4 means 0.8 to 1.2 mm.
What is the difference between CHD, SHD and NHD?
All three are depth-to-a-hardness definitions, but the limit hardness differs: CHD uses a fixed 550 HV 1 because carburized cases all exceed that level; SHD uses 80 % of the minimum surface hardness because induction-hardened medium-carbon steels vary in surface hardness; NHD uses core plus 50 HV 0.5 because nitrided cases are shallow and grade gently into the core.
How do I show a locally hardened area?
Draw a wide dash-dot line parallel to the contour over the hardened length, dimension it, and add the heat-treatment note by leader or in the table; optionally dimension the permitted transition zone and mark areas that must remain soft. Without the line the heat treater assumes all-over treatment.
How does ISO 15787 compare with American practice?
US drawings use free-text notes ("CASE HARDEN 0.030–0.045 IN EFF, 58–62 HRC") with SAE J423 definitions; ISO 15787 gives a fixed grammar and depth symbols. Multinational drawings often carry both — the ISO indication with a J423 equivalent in the notes — so the 550 HV1 versus 50 HRC difference is not missed.
ISO 15787 is copyrighted by International Organization for Standardization. This page explains the document so a drawing can be read; it does not reproduce the standard. Purchase the current edition from the publisher. Official source ↗