Alloy steel is a steel type containing more than one alloying element. Whenever you add each element often introduces new characteristics or improves certain material properties. Generally, all basic steel has iron content and a small percentage of carbon. Chromium is a common alloying element that manufacturers add to other elements to enhance corrosion-resistance properties.
Other common elements suitable with alloy steel are vanadium, nickel, manganese, molybdenum, titanium, and tungsten. The specific elements added to the alloy steel often determine its properties. For instance, manganese improves ductility, wear resistance, and alloy steel’s hardenability. On the other hand, chromium enhances alloy steel’s toughness, hardness, and resistance to wear.
Here are the categories under which alloy steel types are classified:
These alloy steels usually contain a high amount (more than 5% of the total composition) of one or more alloying elements for excellent toughness, hardness, and strength. Common alloying elements for this alloy steel category include manganese, chromium, vanadium, nickel, and molybdenum. Stainless steel is a perfect example of high-alloy steel, containing a minimum of 12% chromium, depending on its grade.
Low-alloy steels contain a lower portion of one or more alloying elements (maximum of 5% of the total composition), offering improved toughness, strength, hardness, or other qualities. Typical examples of alloying elements in this category include tungsten, molybdenum, copper, chromium, manganese, boron, and nickel. Further, typical applications for low-alloy steels include mining and construction equipment due to their high requirement for good strength-to-weight ratios properties.
These steels are famous for their superior toughness and strength. Manufacturers find a use for these steels in applications that require high-strength properties, including military and aerospace applications.
Tool steels are commonly known as highly alloyed steel suitable for tool and die applications in particular. Tool steels can resist wear and hardness even when exposed to high temperatures.
Alloy steels offer certain benefits over stainless steel, making it a material worth considering for various applications. Here are some of these advantages:
Stainless steel is an alloyed steel with a minimum of 10.5% chromium. The chromium element offers stainless steel greater corrosion resistance, making it compatible with extensive applications ranging from medical equipment to cookware. In addition, it is a common choice for consumers and businesses due to its unique features. However, it would help to note that stainless steel has different grades with varying sets of qualities.
Although there are thousands of stainless steel grades, they can be successfully grouped into the following categories:
The austenitic steels usually contain 8-20% nickel and 17-25% chromium at minimal (the basic stainless 304 contains 18% chromium and 8% nickel). These steel grades are usually non-magnetic, and manufacturers use them in food processing equipment and chemical plants due to their high resistance to rust, stain, and corrosion after exposure to water.
Austenitic grades offer excellent corrosion resistance, toughness, ductility, weldability, and high formability. This group’s good examples of stainless steel include 253, 304/304L, and 316/316L.
This category of stainless steel contains between 14 -18% chromium and balanced levels of carbon within the 0.2 and 2% range. You can temper and harden martensitic stainless steel like carbon steel. Likewise, they offer reduced ductility and low weldability. Typical examples are 431, 420C, and 431 stainless steel grades.
The ferritic group contains a portion of chromium, typically between 11- 27% and less or no nickel. This group’s steel is less corrosion-resistant than austenitic stainless steel due to its high amount of chromium. They share certain qualities with iron and show improved mechanical properties at high temperatures, and you can strengthen these steels through annealing.
However, ferritic stainless steels lack toughness which reduces their structural applications. They are only available in coil and sheet. Stainless steel 430 and 409 are apt examples.
Duplex stainless steels have chromium between 18 and 28% and nickel alloying elements between 3.5 and 5.5%. Stainless steel in this grade possesses equal parts of ferrite and austenite and greatly resists pitting and chloride stress. They are weldable, easy to fabricate, magnetic, and offer better corrosion resistance than the austenitic grades. Examples are S32750 and 2205 stainless steel grades.
They contain about 12-16% chromium, 3-8% nickel, and a small proportion of other alloying elements such as copper, aluminum, and titanium capable of forming a precipitate. They are usually very strong, ductile, and heat-treatable. They are machined in the annealed condition and then heat treated.
Stainless steel is one of the prominent materials with high use. It offers extensive advantages over alloy steel, such as:
Manufacturers across industries improve carbon steel’s mechanical properties with the help of more than 20 alloying elements. Each of these alloying elements offers distinct properties. Here are the top five (5) common alloying elements:
This section compares the different aspects of alloy steel and stainless steel:
Alloy steel is famous for its high strength-to-weight ratio, strength, and durability. Also, it maintains hardness at high temperatures and offers good wear and corrosion resistance. On the other hand, stainless steel is easy to clean and highly resistant to corrosion and stain. It is non-magnetic, durable, electrically conductive, and highly resistant to higher temperatures.
The alloying elements of alloy steel include a high amount of chromium, molybdenum, and other alloying elements. Using higher alloying elements helps heat-treat alloys to a wide range of hardness levels.
In contrast, stainless steel is highly resistant to acid, bases, and other organic solutions. Its primary constituents include chromium, carbon, and iron. However, certain varieties often contain nickel, manganese, silicon, and other elements.
Manufacturers often use alloy steels in the construction, automotive, oil and gas, aerospace, and manufacturing fields. On the other hand, typical applications for stainless steel include Kitchenware, medical equipment, the chemical and petrochemical industry, and the food and beverage industry.
Tensile strength describes a material’s ability to withstand tensile strength before it breaks. However, the alloy and the employed heat treatment often determine this property. Alloy steel is very durable, and its tensile strength is about 960 Mpa, while stainless steel is less durable and with a tensile strength of 621 Mpa.
Fatigue stress defines a material’s ability to withstand stress for a particular number of cycles. A material’s fatigue stress is the maximum stress it can withstand. For instance, 146.45 Mpa is the fatigue stress of the stainless 316L.
Generally, stainless steels have lower fatigue strength than alloy steel—nonetheless, stainless steel grades like duplex stainless steel exhibit high fatigue strength due to their microstructure.
Stainless Steel CNC Machined PartsBesides stainless steel, other alternatives to using alloy steel include:
Combining vanadium atoms with chromium forms lattice structures with excellent strength-to-weight ratios. This makes chromium-vanadium ideal for various applications that need a strong and lightweight material. However, due to its strength, most manufacturers use chromium-vanadium to create cutting tools.
Aluminum is a typical material widely utilized in the automobile manufacturing industry. Aluminum products resist corrosion when exposed to water like iron-based metals do. Also, aluminum is perfect for making body panels and other structural components of vehicles because it is very strong and lightweight.
Here are other similar materials that stainless steel is compared against besides alloy steel:
Carbon Steel is one of the famous steel types. It is commonly used because of the durability and high strength it offers. Manufacturers generally use carbon steel for several applications because it costs less than stainless steel. High carbon steel provides excellent strength and resistance to wear, which many cutting tools need. Meanwhile, low-alloy steel offers versatility and malleability for machinery parts, cookware, and pipes.
This is a carbon steel type commonly used for making tools. It exhibits remarkable hardness and wear resistance. As a result, manufacturers utilize these features in manufacturing products such as drill bits, knives, and saws.
Considering the tips below, you should be able to determine the right steel for your application.
The functional requirement of a product will always determine the steel type suited for such application. For instance, if a part is required to function in a marine environment, its corrosion resistance property is a primary factor. Hence, a stainless steel grade material is a perfect choice. Also, alloy steel would be ideal for structural applications such as construction.
Stainless steel is better than alloy steel when considering maintenance and lifespan. Stainless steel grades need little to no maintenance and exhibit longer lifespans because of their self-repairing properties. More importantly, stainless steel is recyclable.
Stainless steel is quite famous for its aesthetic appeal. Hence, product designers and manufacturers in the architecture and interior designing sectors commonly use stainless steel for most parts. Its highly reflective surface makes it shiny and modern. Additionally, it is available in various shapes offering manufacturers extensive products.
The limitations of your budget determine the ideal steel type for your project. As far as cost goes, alloy steel is less expensive than stainless steel. However, it is advisable not to compromise quality for cost.
This article has detailed an explanation of alloy steel vs. stainless steel, discussing their distinct properties. Although both materials offer impressive mechanical properties and are critical to modern manufacturing, it would be best to determine the one that fits your machining project best, considering all variables.
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