Seamless Stainless Steel TP310MoLN Pipe
Enriched with 2% Molybdenum and 0.12% Nitrogen, our 310MoLN pipes offer superior structural stability and resistance to pitting and crevice corrosion compared to standard 310S or 316L grades. These pipes are indispensable for high-pressure urea synthesis, nitric acid production, and aggressive chemical processing. Through advanced cold-drawing and specialized solution annealing, GZH ensures every pipe achieves a high-purity surface finish and precise dimensional accuracy for critical industrial operations.
"Our TP310MoLN pipes exhibit excellent resistance in the Huey Test (ASTM A262 Practice C), ensuring long-term integrity in nitric acid services."
Seamless TP310MoLN Stainless Steel Pipe (UNS S31050): Specifications, Properties, and Applications
Introduction to TP310MoLN Stainless Steel
TP310MoLN (UNS S31050) is a high-purity fully austenitic stainless steel developed for extremely demanding environments such as urea synthesis plants and aggressive chemical processing systems. The alloy is commonly referred to as 25Cr–22Ni–2Mo stainless steel, reflecting its high chromium, nickel, and molybdenum composition.
ASeamless TP310MoLN Pipe is manufactured from a single solid billet using hot extrusion and precision cold drawing processes. This seamless structure eliminates weld seams that could become corrosion initiation sites, ensuring superior reliability in high-pressure carbamate services and chloride-rich environments.
Because of its exceptional corrosion resistance and structural stability, TP310MoLN has become the preferred stainless steel material for modern urea production plants worldwide.
Why Choose TP310MoLN Stainless Steel Pipes
TP310MoLN is an advanced nitrogen-enhanced modification of the traditional 310 series stainless steels. Its optimized chemical composition significantly improves corrosion resistance and mechanical strength.
Key Advantages
Excellent Resistance to Carbamate Corrosion
The alloy is specifically engineered to resist ammonium carbamate solutions used in high-pressure urea synthesis loops.
Improved Pitting and Crevice Corrosion Resistance
The addition of molybdenum and nitrogen increases the alloy’s Pitting Resistance Equivalent Number (PREN), providing superior resistance in chloride-containing environments.
Enhanced Mechanical Strength
Nitrogen strengthening increases both yield strength and tensile strength, enabling optimized wall thickness designs in high-pressure piping systems.
Stable Fully Austenitic Structure
The alloy maintains a fully austenitic microstructure, preventing the formation of brittle sigma phases that could compromise mechanical properties.
Seamless Manufacturing Reliability
Seamless pipes eliminate weld-related corrosion risks such as weld decay and preferential corrosion paths, which is critical for high-purity chemical systems.
Chemical Composition of TP310MoLN (UNS S31050)
The composition is carefully controlled to ensure a ferrite-free and fully austenitic structure suitable for urea-grade service.
| Cr | Ni | Mo | N | P | S | Mn | Si | C |
| 24.00 - 26.00 | 20.00 - 22.00 | 2.50 - 3.50 | 0.20 - 0.30 | ≤ 0.03 | ≤0.03 | ≤ 0.02 | ≤ 0.50 | ≤ 0.02 |
Table 2: Typical Mechanical Properties of Stainless Steel TP310MoLN
Stainless Steel TP310MoLN is specifically designed to maintain its strength and shape in high-stress, corrosive environments.
| Property | Value (Annealed) |
| Tensile Strength | ≥ 690 MPa |
| Yield Strength | ≥ 310 MPa |
| Elongation | ≥ 35% |
| Hardness | ≤ 217 HBW |
| Brinell Hardness | ≤217 HB |
Table 3: Typical Physical Properties of Stainless Steel TP310MoLN
These physical properties highlight the material's ability to perform reliably under a wide range of conditions.
| Property | Value |
| Density | 8.0 g/cm³ |
| Melting Point | 1390 - 1440 °C approx. |
| Thermal Expansion | 16.5 µm/m·°C (20-100°C) |
| Thermal Conductivity | 16.0 W/m·K (20°C) |
| Modulus of Elasticity | 193 GPa |
| Electrical Resistivity | 0.74 x 10⁻⁶ Ω·m (20°C) |
These mechanical properties enable reliable performance in high-pressure chemical reactors and piping systems.
Manufacturing Process and Quality Control
AllSeamless TP310MoLN pipes are manufactured and tested according to international standards including:
- ASTM A312 – Seamless Stainless Steel Pipe
- ASTM A213 – Stainless Steel Tubing for Heat Exchangers
- EN 10216-5 – Seamless Stainless Steel Tubes for Pressure Purposes
Urea Grade Quality Testing
To ensure performance in urea synthesis environments, pipes undergo rigorous testing procedures.
Huey Test (ASTM A262 Practice C)
Used to verify resistance to intergranular corrosion in nitric acid environments.
Microstructural Examination
Ensures the material maintains a fully austenitic structure without ferrite or sigma phases.
Non-Destructive Testing (NDT)
- Ultrasonic Testing (UT)
- Eddy Current Testing (ET)
Full Material Traceability
All pipes are supplied with EN 10204 3.1 or 3.2 Material Test Certificates (MTC) including complete chemical and mechanical test results.
Industrial Applications of TP310MoLN Pipes
Due to its excellent resistance to carbamate corrosion and high mechanical strength, TP310MoLN pipes are widely used in several critical industries.
Urea and Fertilizer Production
Primary applications include:
- High-pressure urea synthesis piping
- Strippers and condensers
- Carbamate scrubbers
- Urea reactors
Chemical Processing Industry
Used for equipment handling aggressive chemical environments including:
- Nitric acid processing
- Organic acid production
- Corrosive chemical reactors
Marine and Offshore Systems
TP310MoLN is suitable for:
- Seawater handling systems
- Desalination plants
- Offshore chemical processing equipment
Pulp and Paper Industry
The alloy is used in:
- Bleaching plant systems
- Chemical recovery equipment
- Corrosion-resistant piping networks
Importance of the Huey Test for TP310MoLN
For stainless steels used in urea synthesis plants, standard corrosion tests are insufficient to verify performance. The Huey Test (ASTM A262 Practice C) is widely accepted as the industry benchmark for evaluating intergranular corrosion resistance.
Huey Test Procedure
The test involves exposing stainless steel samples to boiling 65% nitric acid (HNO₃) for five consecutive 48-hour cycles, totaling 240 hours. After each cycle, weight loss is measured to determine the corrosion rate.
Why the Huey Test Is Critical
Detection of Sensitization
The test determines whether chromium carbide precipitation has occurred at grain boundaries, which could lead to intergranular corrosion in service.
Verification of Urea Grade Materials
To qualify for urea plant applications, TP310MoLN typically must demonstrate an average corrosion rate of ≤ 0.15 mm/year (or ≤ 3.3 μm per 48 hours).
Microstructural Integrity
After testing, samples are examined metallographically to confirm that no grain boundary attack, pitting, or tunneling corrosion has occurred.
Our Huey Test Quality Commitment
Every batch of TP310MoLN seamless pipes is supplied with comprehensive testing certification, including:
- Verified corrosion rate results according to ASTM A262 Practice C
- Compliance with strict end-user specifications such as Stamicarbon or Saipem urea plant standards
- Confirmation of microstructural stability and absence of sigma phases
This ensures that the material meets the highest performance standards required in modern urea production facilities.
