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High-strength low-alloy steel (HSLA) is a type of alloy steel that provides better mechanical properties or greater resistance to corrosion than carbon steel. HSLA steels vary from other steels in that they are not made to meet a specific chemical composition but rather specific mechanical properties.
European standard steel grade names fall into two categories: [1] Steel specified by purpose of use and mechanical properties. Steel specified by chemical composition. The inclusion of a letter 'G' before the code indicates the steel is specified in the form of a casting.
The SAE steel grades system is a standard alloy numbering system (SAE J1086 – Numbering Metals and Alloys) for steel grades maintained by SAE International. In the 1930s and 1940s, the American Iron and Steel Institute (AISI) and SAE were both involved in efforts to standardize such a numbering system for steels.
AerMet alloy is an ultra-high strength type of martensitic [1] alloy steel. The main alloying elements are cobalt and nickel, but chromium, molybdenum and carbon are also added. Its exceptional properties are hardness, tensile strength, fracture toughness and ductility. [2] Aermet is weldable with no preheating needed. [3]
Inconel 792: Increased aluminum content for improved high temperature corrosion resistant properties, used especially in gas turbines; Inconel 907; Inconel 909; Inconel 925: Inconel 925 is a nonstabilized austenitic stainless steel with low carbon content. [74] Inconel 939: Gamma prime strengthened to increase weldability
These materials and others such as titanium, aluminium, magnesium and high strength steel alloys are widely used in aerospace and other applications where weight savings are worth the higher material cost. Note that strength and stiffness are distinct. Both are important in design of efficient and safe structures.
Duplex steels also have higher strength. For example, a Type 304 stainless steel has a 0.2% proof strength in the region of 280 MPa (41 ksi), a 22%Cr duplex stainless steel a minimum 0.2% proof strength of some 450 MPa (65 ksi) and a superduplex grade a minimum of 550 MPa (80 ksi). [6]
Mechanical properties are as follows: room temperature microhardness 760–1350 HV; bending strength 4.6–8 GPa, Young's modulus 160–180 GPa, indentation fracture toughness 1.5–2.7 MPa√m. [8] The morphology of cementite plays a critical role in the kinetics of phase transformations in steel.