Overview
Both 10CrMo5-5 and 13CrMo4-5 are low-alloy steels designed specifically for service at elevated temperatures. They belong to a family of steels known as creep-resistant steels. Their primary advantage over plain carbon steel is their improved strength and resistance to "creep" (slow, continuous deformation under constant stress at high temperatures) and oxidation.
The names are from the European standard EN 10216-2 (Seamless steel tubes for pressure purposes - Technical delivery conditions: Part 2: Non-alloy and alloy steel tubes with specified elevated temperature properties).
1. 10CrMo5-5
This is a chromium-molybdenum alloy steel with good weldability and high-temperature strength.
Material Number (Werkstoff Nr.): 1.7338
Similar Standards:
ASTM A335 P5 (Closely equivalent, though chemistries are not identical)
DIN 17175 (15Mo3 is a similar, lower-grade material)
Chemical Composition (Typical, from EN 10216-2)
| Element | Content (%) |
|---|---|
| Carbon (C) | ≤ 0.15 |
| Silicon (Si) | 0.10 - 0.35 |
| Manganese (Mn) | 0.40 - 0.80 |
| Phosphorus (P) | ≤ 0.025 |
| Sulfur (S) | ≤ 0.015 |
| Chromium (Cr) | 1.00 - 1.50 |
| Molybdenum (Mo) | 0.45 - 0.65 |
Key Characteristics & Applications
Temperature Service Range: Ideal for long-term service in the 500°C to 550°C (930°F to 1020°F) range.
Properties:
Good creep strength.
Good resistance to oxidation and scaling.
Good weldability with proper pre-heat and post-weld heat treatment (PWHT).
Common Applications:
High-temperature steam pipelines and headers in power plants.
Superheater and reheater tubes in boilers.
Heat exchangers and pressure vessels for the petrochemical industry.
2. 13CrMo4-5
This is one of the most common and versatile chromium-molybdenum steels for elevated temperature service. It has higher strength than 10CrMo5-5 due to its higher carbon and chromium content.
Material Number (Werkstoff Nr.): 1.7335
Similar Standards:
ASTM A335 P11 (A very close equivalent)
DIN 17175 (13CrMo44 is the same material)
Chemical Composition (Typical, from EN 10216-2)
| Element | Content (%) |
|---|---|
| Carbon (C) | 0.10 - 0.18 |
| Silicon (Si) | 0.10 - 0.35 |
| Manganese (Mn) | 0.40 - 0.80 |
| Phosphorus (P) | ≤ 0.025 |
| Sulfur (S) | ≤ 0.015 |
| Chromium (Cr) | 0.70 - 1.15 |
| Molybdenum (Mo) | 0.45 - 0.65 |
Key Characteristics & Applications
Temperature Service Range: Excellent for long-term service in the 500°C to 560°C (930°F to 1040°F) range. It can handle slightly higher temperatures than P5/10CrMo5-5.
Properties:
Higher tensile and creep strength than 10CrMo5-5.
Good toughness and ductility.
Good oxidation resistance.
Requires strict control of welding procedures (pre-heat and PWHT are mandatory).
Common Applications:
Superheater and reheater tubes.
High-pressure steam lines and headers.
Petrochemical plant piping for high-temperature processes.
Comparison Table: 10CrMo5-5 vs. 13CrMo4-5
| Feature | 10CrMo5-5 (1.7338 / ~P5) | 13CrMo4-5 (1.7335 / P11) |
|---|---|---|
| Key Difference | Lower Cr, Lower C | Higher Cr, Higher C |
| Carbon (C) | ≤ 0.15% | 0.10 - 0.18% |
| Chromium (Cr) | 1.00 - 1.50% | 0.70 - 1.15% |
| Molybdenum (Mo) | 0.45 - 0.65% | 0.45 - 0.65% |
| Strength | Good | Better |
| Weldability | Good | Good, but requires more care |
| Typical Use Temp | Up to ~550°C | Up to ~560°C |
Critical Manufacturing and Fabrication Notes for Boiler Pipes
Heat Treatment: These pipes are always supplied in the normalized and tempered condition. This heat treatment is essential for developing the required microstructure (tempered bainite or ferrite+pearlite) that provides high-temperature strength and toughness.
Welding: Welding is a critical process.
Pre-heating is mandatory to prevent hydrogen-induced cold cracking.
Post-Weld Heat Treatment (PWHT / Stress Relieving) is absolutely required to restore the microstructure in the Heat-Affected Zone (HAZ), reduce residual stresses, and prevent service failures.
Matching or compatible filler metals must be used (e.g., ER80S-B3, E8018-B3 for 13CrMo4-5/P11).
Non-Destructive Testing (NDT): As per pressure vessel codes, these pipes undergo rigorous testing, including ultrasonic testing, hydrostatic testing, and eddy current testing to ensure integrity.
Summary
10CrMo5-5 and 13CrMo4-5 are workhorse materials for high-temperature pressure applications in power generation and petrochemical industries.
13CrMo4-5 (P11) is stronger and used for more demanding applications than 10CrMo5-5 (~P5).
Their performance relies on a precise chemical balance and strict adherence to heat treatment and welding procedures during manufacturing and fabrication.
When selecting between them, engineers will consult design codes (like ASME B31.1) and consider the operating pressure, temperature, and required design life to choose the most economical and safe material.
