Key Differences Between 12CrMo and 15CrMo Seamless Pipes (For Procurement/Export)

Grades with the "G" suffix (12CrMoG, 15CrMoG)) are specialized boiler pipes (GB5310); those without it are general-purpose alloy pipes (GB6479/GB9948).

I. Chemical Composition (Key Difference, %)

Grade | C | Cr | Mo

--- | --- | --- | ---

12CrMo | 0.08–0.15 | 0.40–0.70 | 0.40–0.55

15CrMo | 0.12–0.18 | 0.80–1.10 | 0.40–0.55

Key Points:

1. 15CrMo has higher carbon content and approximately double the chromium content.

2. Molybdenum (Mo) content is essentially the same for both.

II. Performance Differences

1. Heat/Oxidation Resistance and Hydrogen Corrosion Resistance

- 15CrMo: Higher Cr content → Superior high-temperature oxidation and hydrogen corrosion resistance.

Maximum long-term service wall temperature: ≤550°C

- 12CrMo: Lower Cr content → Reduced upper limit for heat resistance.

Maximum long-term service wall temperature: ≤510°C

2. Strength

15CrMo exhibits slightly higher tensile strength (at room temperature) and high-temperature creep rupture strength compared to 12CrMo..

3. Weldability

12CrMo has lower carbon content, reducing the risk of cold cracking during welding;

15CrMo has stricter preheat and post-heat requirements during welding. III. Equivalent International Grades (Common in Foreign Trade)

- 15CrMo ≈ A213 T12 / A335 P12 / 1 3CrMo45 (EN Standard) / STBA22 (JIS Standard)

- 12CrMo: No direct equivalent in US standards; approximates low-chromium Cr-Mo steel.

IV. Application Scenarios (Key Selection Criteria)

12CrMo (Low Chromium, Low Carbon)

- Moderate temperatures and pressures

- Piping, heat exchangers, and low-to-medium temperature lines for petroleum cracking

- Applications requiring extensive welding and simplified welding procedures

- Not suitable for long-term use above 510°C

15CrMo (Higher Chromium, Superior Heat Resistance)

- High-pressure boiler superheaters and headers (15CrMoG)

- High-temperature, high-pressure piping for petroleum hydrogenation and ammonia synthesis (GB6479 fertilizer equipment piping)

- Long-term operating temperatures: 480–550°C

- Applications requiring resistance to high-temperature oxidation and hydrogen-induced corrosion

V. Quick Selection Guide

- Medium temperature ≤510°C, extensive welding, cost-sensitive → 12CrMo

- Medium temperature 510–550°C, high temperature/pressure, hydrogen corrosion resistance → 15CrMo

❗The two grades are not interchangeable. Use the specific grade designated in the design drawings. Substituting in high-temperature applications risks creep failure.