Steel alloy: Properties, Types, Advantages, Disadvantages, Application

Steel is a metallic substance that is composed of iron and a small percentage of carbon, typically less than one percent. The inclusion of carbon in steel serves to enhance its mechanical properties, particularly its strength and ability to resist fractures. Steel alloy is widely recognized for its exceptional strength and durability, rendering it a highly versatile material. The formation of this material involves the combination of iron with various alloying elements such as manganese, chromium, or nickel. It is widely recognized as one of the most commonly utilized materials within the construction industry.

Steel alloy
Steel alloy

What is Steel alloy?

Steel alloy is an iron-based substance with one or more purposefully added components, most commonly carbon. Steel’s physical and mechanical qualities, like hardness, strength, toughness, high-temperature performance, corrosion resistance, and wear resistance, can all be enhanced by the addition of alloying elements.

Steel alloy is an alloy composed of multiple metallic elements, which are blended together with the aim of enhancing their inherent characteristics. The range of alloying metal quantities can vary between 1% and 50%. The combination of these constituents yields a substance that exhibits the aforementioned properties including enhanced mechanical strength, increased resistance to corrosion, improved resistance to wear, and increased tolerance to high temperatures compared to the individual constituents.

Steel Alloy
Steel Alloy [Image source: sciencealert]

Various elements are commonly employed in the process of alloying, including carbon, aluminum, chromium, nickel, manganese, molybdenum, silicon, tungsten, vanadium, and titanium. Alloy steels can be classified into two distinct categories, namely low alloy steel and heavy alloy steel. The distinction between low alloy and high alloy steel is commonly acknowledged to be determined by the inclusion of a 5% alloying component.

Properties of alloys

Steel alloy exhibits enhanced strength and toughness in comparison to conventional carbon steels as a result of the incorporation of additional elements such as nickel or manganese. As a result of their heightened hardness levels, these materials exhibit superior wear resistance compared to conventional carbon steels. Moreover, their resistance to corrosion and oxidation is attributed to the elevated chromium levels they possess. Consequently, they are frequently employed in the fabrication of robust elements for industrial machinery or automobiles.

  • Steel alloys are formed by the incorporation of carbon steel with various alloying elements, including but not limited to manganese, chromium, nickel, vanadium, molybdenum, or titanium.
  • The steel produced exhibits superior strength and hardness compared to carbon steel, rendering it suitable for various applications demanding elevated levels of robustness and durability.
  • Heat treatment can be employed on alloy steels in order to enhance their mechanical properties. The process of heat treatment encompasses the application of elevated temperatures to steel followed by a rapid cooling process. This procedure has the potential to enhance the tensile strength and hardness properties of the steel material.
  • Steel alloys find frequent utilization in various sectors such as the construction, automotive, and aerospace industries.
  • Steel alloys commonly incorporate various alloying elements such as manganese, chromium, nickel, vanadium, molybdenum, and titanium.

Steel alloy composition

Carbon steels, low-Steel alloys, and high-Steel alloys are the three primary types of steel based on their chemical composition. Several common alloying elements include manganese, nickel, chromium, molybdenum, vanadium, silicon, and boron. Trace pollutants from the steelmaking process are present in all steels. These include phosphorus and sulfur, which are extracted from the rock and fuel in the blast furnace, and manganese, silicon, and aluminum, which are removed during the ladle’s deoxidation process. Copper and other metals, known as residuals, are introduced into the steelmaking kiln via scrap. These components typically account for less than 1% of steel as a whole, making them neither alloys nor alloy precursors.

Alloy elements in steel

  • Manganese: This is the most widely employed alloying element in the production of steel. It improves hardenability and tensile strength while reducing brittleness and sulfur’s effects.
  • Nickel: Nickel improves corrosion resistance, hardness, and strength. Steel’s low-temperature properties are also improved by this.
  • Chromium: Chromium improves a material’s hardness, toughness, and resistance to wear and corrosion. The chromium carbides it produces also contribute to the steel’s increased hardness and strength.
  • Molybdenum: The addition of molybdenum enhances hardenability, high-temperature strength, and slide resistance. Moreover, it enhances the outcomes of additional alloying constituents.
  • Vanadium: Vanadium enhances the strength, hardness, and wear resistance of a material. Vanadium carbides are produced as a byproduct, increasing the hardness and strength of steel.

Steel commonly incorporates various alloying elements such as silicon, boron, aluminum, cobalt, copper, cerium, niobium, titanium, tungsten, tin, zinc, lead, and zirconium.

Types of alloy steel

Steel alloy can be divided into the following categories as discussed below:

Low alloy steel

  • Low-alloy steels are defined as steels in which the proportion of alloying elements constitutes less than 8% of the overall composition of the metal.
  • The inclusion of these alloying elements serves to enhance the mechanical properties of the steel.
  • As an illustration, the incorporation of molybdenum enhances the mechanical strength of the material, while the addition of nickel contributes to its toughness. Furthermore, the inclusion of chromium imparts the metal with elevated strength at high temperatures, improved resistance against corrosion, and increased hardness.
  • Low-Steel alloy finds extensive application in the manufacturing and construction sectors. This steel is commonly utilized in various applications such as military vehicles, construction equipment, ships, pipelines, pressure vessels, structural steel, and oil drilling platforms.

High Strength Low Alloy (HSLA) Steel

  • High-strength low alloy (HSLA) steel, also known as micro-alloyed steel, exhibits a combination of superior strength and commendable resistance to atmospheric corrosion.
  • HSLA steel encompasses six primary categories, namely weathering steel, acicular ferrite steels, pearlite-reduced steels, dual-phase steels, control-rolled steels, and micro-alloyed ferrite-pearlite steels.
  • In general, the enhancement of corrosion resistance is commonly achieved through the incorporation of copper, chromium, phosphorus, and silicon, whereas the augmentation of strength is typically accomplished by the addition of vanadium, niobium, titanium, and copper.
  • The formidable mechanical properties exhibited by high-strength low-alloy (HSLA) steels can pose challenges during the forming process. Zirconium or calcium may be incorporated under specific circumstances to enhance their formability.
  • HSLA materials are extensively employed within the automotive sector. Hot-rolled high-strength low-alloy (HSLA) steel finds application in various automotive components such as suspension systems, chassis, wheels, and seat mechanisms.
  • Cold-rolled high-strength low-alloy (HSLA) steels have the potential to serve as suitable materials for applications involving reinforcements and seat brackets.

High alloy steel

  • High-alloy steel is characterized by its higher alloy content, which exceeds 8% of the overall composition of the steel.
  • The production of high-alloy steel incurs significant costs and presents inherent difficulties in its manipulation. Nevertheless, these grades exhibit exceptional suitability for a range of industries such as automotive applications, structural components, chemical processing, and power generation equipment, owing to their remarkable attributes of hardness, corrosion resistance, and toughness.

Stainless steel

  • Stainless steel is an iron-based alloy that exhibits exceptional resistance to both rusting and corrosion.
  • To attain additional desired characteristics, the composition may encompass elements such as carbon, various non-metals, and metals, alongside the essential minimum chromium content of 11%.
  • The majority of the stainless steel family is comprised of austenitic, ferritic, martensitic, duplex, and precipitation-hardening steels.
  • Austenitic steels, commonly recognized for their exceptional resistance to corrosion, are often composed of nickel and chromium in concentrations of up to 35% and 26% respectively.

Microalloyed steel

  • Microalloyed steel typically contains trace amounts of alloying elements, including niobium, vanadium, titanium, molybdenum, zirconium, boron, and rare-earth metals, which are present in the range of 0.05 to 0.15%.
  • These materials are utilized for the purpose of enhancing precipitation hardening or manipulating the particle microstructure.
  • Microalloyed steels produced through controlled rolling are highly attractive for various engineering applications due to their favorable combination of moderate strength, toughness, excellent fatigue strength, and ease of weldability.

Advanced High-Strength Steel (AHSS)

  • Advanced high-strength steel (AHSS), a specific category of steel, is predominantly employed in the form of sheets for the construction of automotive structures.
  • The steel varieties within this classification initially exhibited multiphase microstructures, wherein ferrite served as the predominant phase. Nevertheless, recent grades have predominantly consisted of martensitic or austenitic compositions.
  • Advanced high-strength steels represent novel iterations of steel grades that ensure compliance with crucial safety and performance standards for steel parts and components, all the while maintaining cost-effective production and ease of manufacturing.

Maraging steel

  • Maraging steel is classified as a distinct steel alloy characterized by its relatively low carbon content. Compared to the majority of steel, this particular ultra-high-strength steel exhibits enhanced toughness and favorable ductility.
  • Maraging steel distinguishes itself from other steel alloys by its hardening mechanism, which involves the precipitation of intermetallic compounds rather than relying on carbon content.
  • Maraging steel exhibits a unique combination of elevated strength and hardness, while also demonstrating a notable degree of ductility. This advantageous mechanical behavior can be attributed to the absence of carbon and the utilization of intermetallic precipitation mechanisms.
  • The principal types of precipitates observed are Ni3Mo, Ni3Ti, Ni3Al, and Fe2Mo, which are also present in significant proportions. Maraging steels find primary applications in the aerospace industry, as well as in the production of tools and weaponry.

Tool steel

  • Tool steel is a highly appropriate type of steel that is particularly well-suited for the production of various tools and tooling, including cutting tools, dies, hand tools, knives, and other similar items.
  • Tool steels are utilized in various processes, such as cutting, pressing, extruding, and coining, to manipulate metals and other components. The utilization of tool steels holds significant importance in tooling applications. One notable example is the indispensability of tool steels in injection molds due to their exceptional resistance to abrasion. This characteristic plays a pivotal role in ensuring the durability of molds, enabling them to withstand numerous molding operations throughout their lifespan, often reaching hundreds of thousands.
  • Tool steels consist of carbide-forming metals such as chromium, molybdenum, tungsten, and vanadium, which are present in varying proportions. These iron-based alloys possess relatively elevated carbon contents, which contribute to their enhanced strength and carbide formation capabilities. In order to enhance the strength at high temperatures, substitutional solutes such as nickel and cobalt are incorporated.

Advantages of alloy steel

One of the major advantages of utilizing alloy steel is its exceptional resistance to corrosion and wear. Steel alloy is composed of chromium and nickel, which enhances its resistance to environmental factors, making it more durable compared to standard carbon steel. This implies that it can be utilized in outdoor settings without any concerns about rust or other forms of damage resulting from exposure to moisture or air. Moreover, alloy steel exhibits greater strength compared to carbon steel, thereby resulting in structures that are inherently more stable and durable than their carbon steel counterparts.

Some of the major advantages of alloy steel are:

  • Increased strength: One of the key benefits associated with alloy steel is its superior strength in comparison to carbon steel. Carbon steel is a variant of steel that is primarily composed of carbon as its principal alloying constituent. Alloy steel incorporates supplementary elements, such as manganese, silicon, or nickel, in order to enhance the material’s strength. Steel alloy is deemed highly suitable for applications that require substantial power, such as those found in the construction and manufacturing sectors.
  • Increased durability: Steel alloy exhibits superior durability compared to carbon steel. The incorporation of additional constituents within the alloy protects the material against potential harm, such as degradation due to abrasion or chemical reactions. The associated durability of alloy steel renders it a favorable option for industries that prioritize long-lasting performance, such as automotive or aerospace engineering.
  • Resistance to heat: An additional benefit associated with alloy steel is its increased capacity to resist heat. The incorporation of additional constituents in the alloy helps to reduce the rate of thermal conductivity exhibited by the material upon exposure to elevated temperatures. Steel alloy is a favorable option for applications that require high heat resistance, such as those found in power plants or chemical plants.
  • Resistance to corrosion: In comparison to carbon steel, alloy steel exhibits enhanced corrosion resistance. The incorporation of supplementary constituents within the alloy serves to protect the material against potential deterioration resulting from contact with water or various chemical substances. Steel alloy is a favorable option for applications that require corrosion resistance, such as those found in marine engineering or food processing.
  • Effective cost: Despite being more expensive than carbon steel, alloy steel remains less costly than stainless steel. Stainless steel is a composite material composed of iron, chromium, and nickel, which renders it more costly compared to carbon and alloy steels as a result of the incorporation of chromium and nickel. Nevertheless, it is important to note that stainless steel exhibits distinct variations in terms of strength and durability when compared to Steel alloy.

Disadvantages of alloy steel

Despite being more expensive than carbon steel, alloy steel remains less costly than stainless steel. Stainless steel is a composite material composed of iron, chromium, and nickel, which renders it more costly compared to carbon and alloy steels as a result of the incorporation of chromium and nickel. Nevertheless, it is important to note that stainless steel exhibits distinct variations in terms of strength and durability when compared to Steel alloy.

  • Metal alloys may be more fragile: One of the principal drawbacks associated with alloy steel relates to its tendency to exhibit increased brittleness compared to pure metals. This phenomenon arises due to the introduction of additional constituents into the steel, thereby altering its microstructural composition and rendering it more prone to fracturing when subjected to external forces. Furthermore, it is commonly observed that alloys exhibit lower ductility compared to pure metals, resulting in their limited ability to undergo rapid wire drawing or shaping processes.
  • Alloys could have lower corrosion resistance: One additional drawback associated with alloy steel pertains to its potentially reduced corrosion resistance when compared to that of pure metals. This phenomenon occurs due to the presence of additional elements within the alloy, which can facilitate the initiation and progression of rust or various forms of corrosion. In addition, it is worth noting that alloys generally exhibit lower resistance to elevated temperatures compared to their pure metal counterparts, thereby potentially limiting their suitability for high-temperature applications.
  • Alloys may cost a bit more: The cost of production is another issue when working with alloy steel. Alloy steel products can be much more expensive than their pure metal counterparts since alloying elements are typically rarer and more expensive than base metal. Alloy steel is more expensive because it requires a more sophisticated and time-consuming manufacturing process than pure metals.
  • Alloys may have numerous properties: An additional drawback of alloy steel pertains to the inherent divergence in properties between alloys and pure metals. This phenomenon occurs due to the introduction of additional components into the steel, thereby altering its inherent physical and chemical characteristics. As an example, certain alloys exhibit enhanced hardness or strength in comparison to their constituent pure metals, whereas others display reduced hardness or strength. Moreover, alloys can exhibit distinct variations in terms of their melting points, boiling points, and densities when compared to those of pure metals.
  • Welding alloys can be challenging: The fact that alloys can be challenging to weld is the last drawback of employing alloy steel. This is so that a poor weld joint can be produced, which can come from the alloy’s constituents separating due to welding heat. Furthermore, alloys are frequently less thermally conductive than pure metals, which means that heat from welding might accumulate in specific locations and harm the material.

Application of Steel alloy

A wide range of products can be produced using alloy steels with diverse compositions. The aforementioned products encompass alloy steel pipes and tubes, alloy steel plates, sheets, and coils, alloy steel bars, rods, and wires, alloy steel forged fittings, alloy steel buttweld fittings, alloy steel flanges, fasteners, and additional components. Steel alloy find extensive applications across diverse industries, including but not limited to automobiles, mining, machinery and equipment, railways, road construction, buildings, appliances, and off-shore applications. Some of the major applications are well discussed below:

  • Building bridges: Bridges employ a specific category of steel known as weathering steel, which possesses unique properties suitable for their intended purpose. The inclusion of nickel, copper, and chromium as alloying elements in these materials contributes to their greater durability to corrosion. Weathering steels are also utilized in architectural applications as cladding material to enhance the visual appeal of buildings. Weathering steels exhibit a high degree of cost-effectiveness over an extended period of time.
  • Building Structures: Steel alloy is commonly employed in the fabrication of structural frameworks for various infrastructural projects such as arenas, skyscrapers, airports, and bridges.
  • Flat products: Steel alloys are commonly employed in the production of flat products, specifically plates, and strips. Plates exhibit a diverse array of grades and sizes within their available range. Fabricated sections are commonly employed in building construction through the process of welding plates together.
  • Coil Products: In addition to undergoing hot or cold rolling processes, Steel alloy sheets can be subjected to galvanization through immersion in heated water. The construction elements, such as side rails, light steel frames, roof purlins, and lintels, are manufactured using hot-dipped galvanized coils.
  • Automotive: Steel alloy is a commonly used material for the construction of various automotive components such as axles, gears, and crankshafts.
  • Alloy steel flanges: Flanges are another crucial component that is produced from alloy steels. Used in piping made of stainless steel. These flanges are customizable to meet your needs. Weld neck flanges are one type that can withstand extreme conditions such as high pressure, high temperature, or sub-zero temperatures since they have the same thickness and bevel as the pipe. Lap joint flanges are slip-on flanges that can be used with Steel alloy pipelines but do necessitate routine inspection and maintenance.

References

  • https://www.amardeepsteel.com/blog/SpecificBlog/alloy-steel/properties-and-uses-of-alloy-steel.html
  • https://testbook.com/mechanical-engineering/alloy-steel-definition-composition-types-and-uses
  • https://blog.thepipingmart.com/metals/alloy-steel-vs-non-alloy-steel-whats-the-difference/
  • https://blog.thepipingmart.com/metals/alloy-steel-advantages-and-disadvantages/
  • https://blog.thepipingmart.com/metals/alloy-steel-properties-and-uses/
  • https://www.iqsdirectory.com/articles/metal-alloys.html
  • https://byjusexamprep.com/alloy-steel-i
  • https://www.industrialmetalsupply.com/blog/what-is-alloy-steel
  • https://www.xometry.com/resources/materials/alloy-steel/#:~:text=Alloy%20steel%20is%20a%20type,tungsten%2C%20silicon%2C%20and%20vanadium.

About Author

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Jyoti Bashyal

Jyoti Bashyal, a graduate of the Central Department of Chemistry, is an avid explorer of the molecular realm. Fueled by her fascination with chemical reactions and natural compounds, she navigates her field's complexities with precision and passion. Outside the lab, Jyoti is dedicated to making science accessible to all. She aspires to deepen audiences' understanding of the wonders of various scientific subjects and their impact on the world by sharing them with a wide range of readers through her writing.

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