1. What are the properties of 253MA?
253MA is a high-temperature austenitic stainless steel, often categorized as a super austenitic or heat-resistant grade, designed to perform exceptionally in elevated-temperature environments. One of its key properties is outstanding high-temperature oxidation and corrosion resistance: it forms a dense, adherent oxide scale composed of chromium, manganese, and silicon at temperatures up to 1150°C (2102°F), which effectively prevents further oxidation and makes it resistant to thermal cycling (repeated heating and cooling) as well as corrosion from industrial atmospheres like combustion gases and steam. It also exhibits good mechanical strength at elevated temperatures, maintaining useful tensile and creep strength across the range of 800°C to 1100°C (1472°F to 2102°F)-a performance that surpasses standard austenitic stainless steels such as 304 and 316 in high-heat scenarios. Additionally, 253MA has excellent thermal conductivity and thermal fatigue resistance; its thermal conductivity is higher than that of many nickel-based superalloys, reducing the buildup of thermal stress, and its austenitic structure enhances resistance to cracking caused by repeated heating and cooling cycles. It also offers good formability, allowing it to be processed through methods like rolling, bending, and deep drawing, along with reliable weldability-when using proper procedures (such as matching filler metals like ER 253MA), it retains joint integrity and high-temperature performance without significant embrittlement. Finally, due to its fully austenitic crystal structure, 253MA remains non-magnetic in both annealed and welded conditions, a trait that is valuable in applications where magnetic interference needs to be avoided.
2. What is the chemical composition of 253MA?
The chemical composition of 253MA is tightly regulated to optimize its high-temperature properties, and it complies with standards such as ASTM A240/A240M, EN 1.4835, and ASME SA-240. The typical composition (measured by weight percentage, wt%) includes carbon (C) in the range of 0.05–0.10 wt% (with a maximum of 0.10 wt%), which enhances high-temperature strength and aids in carbide formation. Chromium (Cr) is present at 20.0–22.0 wt% (maximum 22.0 wt%), serving as the primary element for oxidation resistance by forming a protective Cr₂O₃ scale. Nickel (Ni) makes up 10.0–12.0 wt% (maximum 12.0 wt%), stabilizing the austenitic structure and improving toughness. Manganese (Mn) is included at 1.5–2.5 wt% (maximum 2.5 wt%), helping to form protective oxide scales and boosting high-temperature strength. Silicon (Si) ranges from 1.4–2.0 wt% (maximum 2.0 wt%), enhancing oxidation resistance by forming SiO₂ and supporting the adhesion of the oxide scale. Nitrogen (N) is added at 0.14–0.20 wt% (maximum 0.20 wt%), strengthening the austenitic matrix and improving creep resistance. Cerium (Ce) is present in small amounts (0.03–0.08 wt%, maximum 0.10 wt%), refining the grain structure, improving scale adhesion, and reducing the oxidation rate. Phosphorus (P) and sulfur (S) are controlled to low levels, with maximum limits of 0.04 wt% and 0.03 wt% respectively, to minimize embrittlement and maintain weldability. Iron (Fe) acts as the base metal and constitutes the balance of the composition.
3. What is the tensile strength of 253MA?
The tensile strength of 253MA is dependent on its heat treatment condition, and it is typically supplied in the annealed state-this is the standard condition for its intended high-temperature applications. Standards like ASTM A240 and EN 10088-2 specify its tensile strength values. At room temperature, the ultimate tensile strength (UTS) of 253MA has a minimum requirement of 650 MPa (94,300 psi), with a typical range of 650–750 MPa (94,300–108,800 psi). For elevated temperatures, which are critical to its use case, the minimum UTS is approximately 300 MPa (43,500 psi) at 800°C (1472°F), around 120 MPa (17,400 psi) at 1000°C (1832°F), and roughly 60 MPa (8,700 psi) at 1100°C (2012°F). These values demonstrate the alloy's ability to retain load-bearing capacity in high-heat environments, a key requirement for applications such as furnace components and exhaust systems.
4. What is the yield strength of 253MA?
Similar to tensile strength, the yield strength of 253MA-measured as 0.2% proof stress, which is the stress at which 0.2% permanent deformation occurs-is specified for the annealed material and varies with temperature. At room temperature, the minimum yield strength requirement is 300 MPa (43,500 psi), with a typical range of 300–400 MPa (43,500–58,000 psi). For elevated temperatures, the minimum 0.2% proof stress is approximately 180 MPa (26,100 psi) at 800°C (1472°F), around 70 MPa (10,150 psi) at 1000°C (1832°F), and roughly 35 MPa (5,080 psi) at 1100°C (2012°F). These yield strength values ensure that 253MA can withstand operational stresses without undergoing permanent deformation, even when exposed to the high temperatures it is engineered to handle.
