Metal that is resistant to oxidation is known as stainless steel. Stainless steel is an alloy formed by the combination of several metal elements with a specific composition. The combination of these metals produces a new metal with properties or characteristics superior to the previous metal elements. The following is a comprehensive discussion of stainless steel characteristics, grade and applications.
6 Stainless Steel Characteristics
High chromium levels percent
Stainless steel contains at least 10.5% chromium. This chromium element’s content is the primary protector of symptoms caused by environmental conditions.
Resistance to corrosion
While other metals require galvanizing to be corrosion resistant, stainless steel is naturally corrosion resistant regardless of the manufacturing method. The presence of a high chromium element contributes to stainless steel’s corrosion resistance. Stainless steel is resistant to the effects of oxygen due to the presence of a stable oxide layer on its surface. This oxide layer is self-healing and it remains intact even if the object’s surface is cut or damaged.
Low maintenance and long-lasting
Stainless steel equipment does not necessitate complicated maintenance. Rust-resistant characteristics of Stainless steel make it more durable and less prone to oxidation damage.
High hardness and strength
In comparison to mild steel, stainless steel has a higher tensile strength. The tensile strength of duplex stainless steels is greater than that of austenitic stainless steels. The martensite (431) and precipitation hardening grades have the highest tensile strength (17-4 PH). These grades can be twice as strong as the most commonly used stainless steel, types 304 and 316.
Cryogenics resistance (resistance to low temperatures)
At subzero temperatures, cryogenic resistance is measured by ductility or toughness. The tensile strength of austenitic stainless steels is significantly higher at low temperatures than at room temperature.
Because toughness decreases significantly at low temperatures, martensitic, ferritic, and precipitation-hardening steels should not be used at subzero temperatures. The decrease occurred in some cases at temperatures close to room temperature.
Appealing appearance
Stainless steel has a gleaming silver color, making stainless steel items more appealing. Because stainless steel has an appealing appearance, it is frequently used for equipment in a variety of fields of human life.
Stainless Steel Grade and Applications
Stainless steel is classified into several main groups or classes based on the type and percentage of the material used. The grade and applications of stainless steel are as follows:
Martensitic stainless steel
An alloy of iron and chrome. It is high in carbon and low in chromium, with 1% chromium and 35% carbon. Classes 410 and 416 include it. Martensitic stainless steel has magnetic properties, moderate corrosion resistance, and poor weldability.
Martensitic stainless steel is commonly used for the following applications:
- Scalpel
- Cutlery
- Surgical/operating equipment
- Zippers
- Arrows
- Springs
Ferritic stainless steels
Iron-chrome alloy with low carbon content. The chromium content ranges between 10.5 and 18%. Ferritic stainless steels have good corrosion resistance but poor manufacturing properties. Modification of alloys such as 434 and 444 can improve manufacturing properties. The inability of stainless steel to be hardened by heat treatment is one of its distinguishing features. It is always used in annealed conditions. It is magnetic and can withstand welding in thin sections.
Ferritic stainless steels are commonly used in the following applications:
- Vehicle exhaust
- Cooking ware
- Architectural trim
- Household equipment
Austenitic stainless steel
An iron-chrome-nickel and iron-chrome-nickel-manganese alloy with a chromium content of 18% and a nickel content of 8%. The properties of stainless steel can be altered by adding other elements such as Molybdenum, Titanium, and Copper. This modification increases corrosion resistance.
At low temperatures, most steels become brittle, but the presence of nickel in austenitic stainless steels makes them suitable for low-temperature or cryogenic applications. This type of stainless steel is generally nonmagnetic and cannot be hardened through heat treatment. This is the most malleable type of stainless steel.
Austenitic stainless steel is commonly used for the following applications:
- Kitchen sink
- Architecture, such as roofs, gutters, doors, windows
- Food processing equipment
- Ovens
- Chemical tank
Duplex stainless steel
Duplex stainless steel is high in chromium and low in nickel. This results in the microstructure of duplex stainless steels containing austenitic and ferritic elements. Duplex stainless steels are austenitic and ferritic. The properties of this duplex stainless steel are corrosion pressure resistant, but not to the level of ferritic grades. Meanwhile, in terms of toughness, duplex grades outperform ferritic grades but fall short of austenitic grades. Duplex grades are lightweight and have high tensile strength.
Duplex stainless steel is used in the following applications:
- Heat exchangers
- Marine applications
- Food preservation industry
- Oil and gas off-shore installations
- Chemical and petrochemical industry
Precipitation-hardening stainless steel
As a hardener, titanium, boron, or beryllium are added to the iron-chrome-nickel alloy. The tensile strength of this grade of stainless steel increases dramatically with heat treatment. The most common precipitation-hardening stainless steel grade is 630, also known as 17-4 PH because it contains 17% chromium, 4% nickel, 4% copper, and 0.3% niobium.
Precipitation-hardening stainless steel is commonly used for the following applications:
- Pulp and paper industry equipment
- Space application
- Turbine vanes
- Mechanical components