L485M is a pipeline steel designation defined in the API 5L standard (American Petroleum Institute standard), belonging to high-strength microalloyed steel. The "M" indicates that it undergoes a controlled rolling or controlled cooling process (Thermo-Mechanical Controlled Process, TMCP), resulting in superior low-temperature toughness and weldability. Key characteristics include:
1. Chemical Composition: Carbon content ≤0.12%, manganese content ≤1.60%, with the addition of microalloying elements such as niobium and vanadium to improve strength (refer to API 5L, 46th edition).
2. Mechanical Properties: Minimum yield strength 485 MPa, tensile strength 535-760 MPa, elongation ≥18% (according to ISO 3183 standard).
3. Applicable Environment: Commonly used in low-temperature environments below -20℃, such as Arctic oil and gas pipeline projects.
Chemical Composition of L485M Steel
Carbon (C): ≤0.12%
Manganese (Mn): 1.60-1.80%
Niobium (Nb): 0.06-0.08%
Titanium (Ti): 0.026-0.032%
Molybdenum (Mo): 0.12-0.16%
Chromium (Cr): 0.16-0.20%
Nickel (Ni): 0.11-0.18%
Sulfur (S): ≤0.005%
Phosphorus (P): ≤0.02%
Mechanical Properties of L485M Steel
Yield Strength (ReL): 485-605 MPa (Actual production can reach 517-593 MPa);
Tensile Strength (Rm): ≥570 MPa (Actual 641-695 MPa);
Elongation (A50): ≥22% (Some can reach 34%) (Above);
Low-temperature impact energy: ≥270 J (transverse) at -60℃, drop hammer tear test (DWTT) shear area ≥88% at -15℃;
Yield ratio: ≤0.88 (ensuring plasticity reserve).
The core differences between L485 and L485M:
Users typically refer to L485 steel pipes as being produced using conventional hot-rolling processes of the same grade.
The key differences are as follows:
1. Process differences: L485M uses the TMCP process to refine the grain size, resulting in superior impact toughness compared to ordinary L485 (impact energy at -40℃ ≥60J, while L485 is ≥40J).
2. Carbon equivalent: L485M has a carbon equivalent (Ceq) ≤0.43%, resulting in a lower risk of cold cracking during welding (calculation formula: Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15).
3. Application scenarios: L485 is mostly used for ambient temperature pipelines, while L485M is suitable for high-pressure, low-temperature, or corrosive environments.
