Fundamentally, steel is an alloy composed mainly of iron (Fe) and carbon (C). This may seem simple, but the remarkable aspect lies in the very narrow range of carbon content - typically ranging from 0.02% to 2.11%.The importance of steel stems from its exceptional combination of strength, durability, and workability, making it a fundamental material for construction, infrastructure, tools, vehicles, and countless consumer goods.

HSS stands for High-Speed Steel. It is a class of high-performance tool steels known for its high hardness, excellent wear resistance, and, most importantly, its ability to retain that hardness at elevated temperatures.

There is no universal "better" option. The choice between carbon steel and stainless steel is fundamentally a trade-off between "Strength & Cost" and "Corrosion Resistance & Low Maintenance." The optimal material depends entirely on the application's specific requirements and constraints.

HSS: Usually refers to high-speed steel, which is a type of tool steel used for manufacturing cutting tools.
AHSS: Generally refers to advanced high-strength steel, which is a type of structural steel and is mainly used in the manufacturing of car bodies.

Complete Analysis of Low-Temperature Performance of Stainless Steels: Austenitic vs. Ferritic vs. Martensitic
Core Conclusion
The primary rule for selecting stainless steels for low-temperature service is: The microstructure must be Face-Centered Cubic (FCC).
Austenitic Stainless Steels have an FCC structure and are the undisputed champions for cryogenic applications due to their exceptional toughness.
Ferritic and Martensitic Stainless Steels have a Body-Centered Cubic (BCC) structure, which undergoes a Ductile-to-Brittle Transition (DBTT), making them unsuitable and dangerous for pressurized low-temperature equipment.

The 304 series is the most classic and widely used austenitic stainless steel, often referred to as "18-8 stainless" (18% Chromium, 8% Nickel). 304L and 304H are derived variants, with the key difference lying in their carbon content and control.