13MnNiMoR is a high-strength, high-toughness low-alloy heat-resistant steel with excellent hydrogen resistance and weldability, specifically designed for manufacturing large welded pressure vessels operating under high-temperature, high-pressure, and hydrogen-containing environments.
The grade designation has a clear technical meaning:
- "13" indicates an average carbon content of approximately 0.13% (by weight), balancing strength with good toughness and weldability;
- "Mn" stands for manganese, which provides solid-solution strengthening and improves hardenability;
- "Ni" denotes nickel, which effectively enhances low-temperature toughness and microstructural stability;
- "Mo" refers to molybdenum, a key alloying element that significantly improves elevated-temperature strength and resistance to hydrogen attack, while also helping to suppress temper embrittlement;
- "R" is the first letter of the Chinese pinyin "Rong" (meaning "vessel"), indicating its use in pressure equipment.
Therefore, 13MnNiMoR refers to a specialized pressure vessel steel with ~0.13% carbon and alloyed with manganese, nickel, and molybdenum.
This steel plate is widely used in critical equipment within the petrochemical, coal chemical, hydrotreating, and hydrocracking plants, such as hydroprocessing reactors, hot high-pressure separators, heat exchangers, and large spherical tanks. Its typical service temperature ranges from -20°C to 450°C, making it especially suitable for pressure-bearing components subjected to prolonged exposure to high temperature, high pressure, and hydrogen media. Key characteristics of 13MnNiMoR include: yield strength ≥360 MPa, tensile strength 510–660 MPa, and excellent overall mechanical properties; enhanced resistance to hydrogen-induced cracking (HIC) and hydrogen corrosion due to the synergistic effect of nickel and molybdenum; good microstructural stability and creep strength at elevated temperatures; and favorable weldability, with proper preheating and post-weld heat treatment (e.g., stress relief annealing) ensuring joint integrity and reliability.
Currently, 13MnNiMoR is manufactured and inspected in accordance with the Chinese national standard GB/T 713-2014 Steel Plates for Boilers and Pressure Vessels. Published and implemented in 2014, this standard replaced the previous GB 713-2008 edition and introduced stricter requirements on chemical composition, mechanical properties, impact toughness, ultrasonic testing, and thickness-direction properties. It is one of the core standards widely adopted in China’s boiler and pressure vessel industry. As a representative of high-end domestic hydrogen-resistant steels, 13MnNiMoR has been successfully applied in numerous major energy and chemical projects, achieving localization of critical materials and strongly supporting the independent development of China’s advanced equipment manufacturing.
Ultrasonic Testing (UT)
A key non-destructive testing technique that uses high-frequency sound waves to detect internal flaws in steel plates. The probe emits sound waves, which reflect when encountering defects such as cracks or inclusions. The receiver captures the echoes, enabling precise determination of defect location and size. With high sensitivity, strong penetration, and fast inspection speed, UT effectively ensures internal quality, widely used in the production of heavy plates, pressure vessel plates, and other high-end products to guarantee safety and reliability.
Magnetic Particle Testing (MT)
A common surface inspection method that magnetizes the workpiece, causing leakage magnetic fields at surface or near-surface defects like cracks or inclusions, which attract magnetic particles to form visible indications. Simple to operate and highly sensitive, MT is suitable for rapid inspection of surface and near-surface flaws in ferromagnetic materials, widely used for online or offline inspection of plate edges, ends, and welds, ensuring product quality and safety.
Penetrant Testing (PT)
A non-destructive method for detecting surface-breaking flaws. A penetrant liquid is applied to the cleaned steel surface, allowing it to seep into defects such as cracks or pores. After removing excess penetrant, a developer is applied, causing the trapped penetrant to bleed out and form visible indications. Simple and cost-effective, PT is suitable for inspecting surface defects in various non-porous materials, commonly used for welds, castings, and complex components, effectively ensuring surface quality of steel plates.
