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Introduction
Ferritic stainless steels are widely used in a variety of industries and applications, due to their outstanding corrosion resistance, toughness, and formability. Research into the mechanical properties of ferritic stainless steels has increased over the past few decades, since higher strength levels have become important for structural applications that require weldability. 00Cr30Mo2, commonly known by its grade S13093, is a ferritic stainless steel developed specifically for the oil and gas industry. This steel grade contains 30-32% chromium, 2-3.5% molybdenum and lower amounts of nickel and nitrogen. The aim of this article is to provide an overview of the mechanical properties of S13093 and summarize the key results from its research.
Material Properties
The chemical composition of S13093 is shown in Table 1. This grade contains significantly lower amounts of alloying elements than austenitic stainless steels, due to its ferritic microstructure, and it has a higher chromium content compared to other ferritic grades like UNS S44100 or S44400. Its mechanical properties depend on the amount of chromium and molybdenum present in the steel. The minimum yield strength of this steel is 315 MPa, with an ultimate tensile strength of 565 MPa and elongation of >25%. Its impact strength is also good, with an impact energy of >40 J at –20°C, which gives it excellent toughness. The steel also displays a Charpy V-notch (CVN) impact strength of >50 J at –20°C, making it suitable for use in cold environments.
Table 1. Chemical composition of 00Cr30Mo2 (S13093).
C Si Mn P S Cr Mo Ni N 0.05 0.5 1-1.5 0.05 0.02 30-32 2-3.5 0.5 0.10
Heat Treatment
The mechanical properties of S13093 can be further improved by heat treatment. The most common heat treatment for this grade is to solution anneal at 1150-1250°C, followed by water quenching. It is also possible to do a double quench (first in oil and then in water) to obtain higher fatigue strength and fracture toughness. The steel can also be aged at 650-700°C after solution annealing, to increase its strength and toughness.
Weldability
S13093 demonstrates excellent weldability and resistance to corrosion cracking, making it a suitable choice for welding applications. The martensitic and ferritic microstructures obtained after welding provide superior toughness and strength compared to other stainless steels. The weldability of this grade is further enhanced when post-weld heat treatment is used, as it enhances the weld’s resistance to cracking.
Corrosion Resistance
S13093 exhibits excellent corrosion resistance to both acidic and crevice corrosion, making it suitable for use in harsh environments. The chromium content in this grade prevents the formation of rust, and its molybdenum content helps to protect it from oxidation. In addition, the nitrogen content helps to provide additional protection against crevice corrosion.
Conclusion
S13093 is a ferritic stainless steel that has been developed specifically for the oil and gas industry. Its chromium and molybdenum content give it excellent corrosion resistance, with good weldability and toughness. Its mechanical properties can be further enhanced by heat treatment, making it suitable for use in a variety of applications that require superior mechanical properties.
