GB/T 6394-2002 — Metal Average Grain Size Rating Chart (English)

GB/T 6394-2002 — Metal Average Grain Size Rating Chart

Metallographic Structure Standard Atlas — Metal Average Grain Size Determination Chart GB/T 6394-2002

---

Series I — Non-Twinned Grains (Light Etching) ×100

Grain size grades ranging from 00 to 8, showing non-twinned austenite grains under light etching at 100× magnification.

Grade 00 – Grade 2

Grade 2½ – Grade 5

Grade 5½ – Grade 8

---

Series II — Twinned Grains (Light Etching) ×100

Grain size grades 3 through 8, showing twinned austenite grains under light etching at 100× magnification.

Grades 3 – 8

---

Series IV — Austenite Grains in Steel (Carburizing Method) ×100

Austenite grain size determination using the carburizing method at 100× magnification.

Grade 1 – Grade 6

Grade 7 – Grade 8

---

Download Original PDF

Click the link below to view or download the original Chinese version of this grain size rating chart:

📥 Download Original PDF — GB/T 6394-2002 Grain Size Rating Chart

---

Note: This chart follows the Chinese National Standard GB/T 6394-2002 (equivalent to ASTM E112 grain size methodology). Grain size number (G) relates to the average grain area — higher numbers indicate finer grains.