I. Introduction
Material choice is a critical production criterion when embarking on a manufacturing project. And while many manufacturing projects employ metallic materials like aluminum and stainless steel across several industries in different applications, it is always best to understand that not all metals are created equally. Several metals and alloys have various unique properties based on their constituents. Furthermore, these constituents determine their properties and behavior or performance in specific use cases. Aluminum and stainless steel, as widely used manufacturing materials in mold manufacturing and other applications, are the focus of this article. These metals are unique in strength, durability, weight, and other parameters, indicating their suitability for engineers and structural designers in many industries. At the end of this article, you will be armed with the knowledge that will help you correctly identify the most suitable material between the two in your projects. So, if you’re ready, let’s dive in.
II. Element Composition
At their core, metals, and alloys are composed of one or more elements significantly responsible for their properties and usability for different purposes. Aluminum and stainless steel are no different in this regard.
Aluminum in itself is an element and, as such, can be taken as a single-element metal so that its properties will be based on this single element. Many manufacturing sectors, including automotive, construction, and aerospace, all use aluminum in one form or the other.
It is known for its lightweight and relatively high strength, comparable to several other high-strength metals.
On the flip side is stainless steel, which is equally popular across several industries especially considering its use in the field where it is preferred for its anti-corrosion properties. It also comprises several elements that contribute to its properties in different capacities. Its main anti-corrosion element is chromium, with other elements like iron and nickel also contributing significantly to other properties. Nevertheless, carbon and other elements also make up the constituents of stainless steel in different quantities depending on the desired performance.
Evidently, aluminum and stainless are never in short demand across different industries. Nonetheless, their elemental composition remains critical in analyzing and predicting their performance in various use cases.
III. Corrosion Resistance
Due to its negative effect on manufacturing components like equipment and machines, corrosion is often a primary consideration when selecting materials for a production project. Its impact can cause significant deterioration to these manufacturing components during their service life leading to loss of production time and revenue.
Thankfully, materials like aluminum and stainless steel offer anti-corrosion properties to combat these negative consequences. However, they vary in their levels of anti-corrosion attributes.
For instance, aluminum is corrosion-resistant by default and can preserve itself with a layer of aluminum oxide when subjected to water and high humidity. Nonetheless, its protective layer can crumble in the face of very harsh chemicals and environments. With stainless steel, the presence of chromium gives it a better resistance to corrosion than what is obtainable with aluminum. This chromium develops a protective layer over the steel material during oxidation, ensuring that the material remains intact in areas with high degrees of moisture and extreme temperature. Composition, among other factors like temperature and duration, are the underlying considerations when choosing one of these materials for their anti-corrosion properties.
IV. Electrical Conductivity
Being able to easily pass along electricity is a unique property known as electrical conductivity. Designers and engineers often seek this property in special use cases where electricity flow is an important consideration. Consequently, materials like stainless steel and aluminum are usually considered for use in some projects based on their ability to transmit electric current in such situations.
For aluminum, which is often a preferred material for highly electrically conductive devices, its application for producing electrical components is noteworthy. Compared to stainless steel, its conductivity can be as high as twenty times and over, especially since it has a higher electron density.
Notwithstanding, stainless steel offers a considerable electrical conductivity though lower than aluminum, reducing its preference in situations requiring electrical conductivity.
V. Thermal Conductivity
Again, the ability to transmit heat away from a device is often required in certain high heat-generating processes. This property is often critical in analyzing the efficiency of heat-distributing devices like heat sinks and radiators. In that light, accessing the thermal conductivity of both aluminum and stainless-steel materials reveals that aluminum has superior heat conduction than stainless steel. This explains why aluminum is often preferred to manufacture heat sinks, boilers, and other heat-transmitting devices. The presence of this property in abundance or the lack of it is majorly a result of the different elements constituting both stainless steel and aluminum.
VI. Melting Point
For manufacturing devices that will be exposed to extreme temperatures during their service lives, considering the melting point of their production material is crucial for the product’s effectiveness. Especially in mold design, where engineers and production specialists understand the implication of a material’s melting point, selecting a suitable material for molds is significantly governed by its melting point.
A material like stainless steel generally exhibits a higher melting point than aluminum, even though stainless steel’s melting point can vary depending on the percentage of certain constituents. In essence, it takes more heat to liquefy stainless steel than is required for aluminum. The downside is that the ease of working with stainless steel using manufacturing methods like forging can be significantly higher than with aluminum. However, stainless steel can resist stress due to extreme temperatures than aluminum.
VII. Hardness
The ability of a material to resist indentation or scratch reveals how hard it is. It also indicates a material’s durability, as hard materials are often less impacted by wear and tear over a long period. For stainless steel, made up of different elements in different quantities, its hardness usually varies depending on the percentage of specific constituents. Nevertheless, it is still harder than aluminum, making it a preferred material where high performance and motion are critical. Aluminum, being softer, is more workable, especially with manufacturing processes like CNC machining since it is more ductile than stainless steel.
VIII. Density
A material’s density indicates how heavy or light it is compared with a standard medium like water. This property helps metallurgists and materials engineers identify which material will be most suitable where the ease of lifting and working with a material or component is a major consideration. For instance, in mold manufacturing, where moving molds is critical to production efficiency, comparing the densities of materials like aluminum and stainless steel will be very useful.
Aluminum is a light material, about four times less dense than stainless steel. This property makes aluminum more suitable for specific uses, especially in producing components like airplane parts where strength and low density are critical. On the downside, aluminum is less durable than stainless steel as it can’t withstand as much pressure as stainless steel without deteriorating.
IX. Durability
Material that can withstand pressure or significant forces without appreciable wear or tear of the material can be said to be durable. For example, a mold’s durability will be equated to its ability to withstand mold injection pressure without deforming or deteriorating. The hardness of a material also plays a significant role in a material’s durability seeing that hard materials often resist stresses easily.
Stainless steel is often more favored for its higher durability as it can resist more stress than aluminum without undergoing permanent deformation or failure. This results from its high strength and hardness, making it suitable for automotive manufacturing components like gears, wheels, and engine parts. Nonetheless, aluminum still offers appreciable strength, especially when you compare its strength-to-weight ratio.
X. Machinability
The ease of working on material or shaping it using different manufacturing tools and equipment, including CNC, drilling, and milling machines, indicates its level of machinability. The easier it is to use a machine to achieve production with a material, the higher the material’s machinability. Several factors depend on the material’s machinability, including the duration and cost of manufacturing.
Aluminum has more machinability than stainless steel, considering that it is softer and more pliable. Hence, it will require less effort, time, and cost to achieve production with an aluminum material than with stainless steel. Furthermore, aluminum requires simple tools to achieve production, unlike stainless steel, which often requires specialized tools to achieve the same result. Nevertheless, the durability of stainless steel often justifies the additional effort and cost due to its strength and durability.
XI. Formability
Some production requires specific manufacturing processes, including hot and cold rolling and forging, which often depend on easily shaping a material without deformation. This process is also known as its formability. Considering a material’s formability is often crucial in manufacturing complex geometrical components requiring high accuracy and speed. Aluminum generally has the upper hand when it comes to shaping it into various intricate shapes, as it can form various shapes easily and speedily, especially with rapid prototyping. However, stainless steel is often tough to form into complicated shapes and requires special equipment, which comes at exorbitant costs. Ultimately, the product’s accuracy and complexity will determine the preferred material between stainless steel and aluminum.
XII. Weldability
Fusing two or more components or parts by heating them is a standard manufacturing procedure known as welding, and it has come a long way as many industries utilize it in their production. Hence, many of these industries often consider the ease of welding production materials in their design, as it can significantly impact their production process and bottom line. Generally, it is agreed that you can weld aluminum easier and faster without any failures or cracks than stainless steel.
The reason is related to the thermal conductivity of both materials, as aluminum can conduct heat better than stainless steel with a relatively lower expansion than stainless steel when both are heated. Also, you’ll require advanced methods to weld stainless steel to get the required welding quality, unlike aluminum, which uses standard welding methods and equipment.
XIII. Yield Strength
The ability of materials to return to their original size and dimension after a force or load has stretched them without any permanent deformation is known as their yield strength. This parameter is essential for structures and components that often experience elongation when impacted by temporary or semi-permanent forces.
For materials like stainless steel and aluminum, which are used across many facilities in manufacturing several products, their yield strength can make them suitable or unfit for a particular project. Aluminum is generally agreed to have less yield strength than stainless steel as it can withstand less impact before its deformation. Although certain grades of stainless steel may have considerably lower yield strength, proper consideration should be given to the grade of stainless steel in material selection.
XIV. Tensile Strength
The ability of a material to bend under a force without experiencing any failure or deformation is termed its tensile strength. This parameter is essential for situations where materials are subjected to forces and loads that may cause material bending. These situations happen quite often during a product’s service life. Stainless steel generally has more tensile strength than aluminum, as this is often related to the weight of which stainless steel has more. As a result, stainless steel is usually preferred in manufacturing automotive and mechanical components and devices that are usually subjected to tensile stress, including shafts and rods.
XV. Shear Strength
The shear strength of a material measures its ability to withstand any force that tends to separate a single material into two parts at the point on the material where the force was applied. It is often critical for components subjected to direct forces or load.
Stainless steel can resist direct forces of higher magnitude than aluminum as it has more shear strength. It is why stainless steel is often preferred over aluminum for mold materials usually subjected to direct forces and pressure, including injection molding. Its superior shear strength also translates to stainless steel’s higher durability than is obtained with aluminum.
XVI. Color
Inspection of both aluminum and stainless can be tricky for an untrained eye. While they both appear silvery in color, their luster and glitter differentiate them apart. For example, aluminum has a clearer silver finish, while stainless steel has a darker feel to its silver finish. However, stainless steel appears to glitter more than aluminum under visible light. Furthermore, aluminum and stainless steel retain coating well and can be given a variety of colors with coating depending on the color specification.
XVII. Applications
The unique properties of aluminum and stainless steel have always been the main determinant of their suitability for a project. While they remain popular across many industries, their applications remain unique, with some highlighted below.
Stainless Steel:
- It is used for structural components in construction, including door hinges, handles, and locks.
- It is employed for automotive accessory manufacture, including wheels and grills.
- It functions as unreactive hygienic utensils in the medical field.
- It is also engaged for durability and strength in the aerospace industry for aircraft components.
Aluminum:
- It is also used for structural members in construction, including for poles, roofing, and doors.
- It is employed in the electrical industry for its electrical conductivity.
- It is applied in consumer industries for packaging products and household items.
- It is used in the marine industry for its anti-corrosion properties to make components.
XVIII. Cost
Several factors can determine aluminum and stainless steel costs, most of which we have previously highlighted in this article. However, the chief of these factors includes the quantity of each constituent, especially for stainless steel, which has a number of constituting elements. These constituents determine the grades of stainless steel and its properties, including its strength, durability, and machinability. In essence, stainless steel is always more expensive because of its strength, durability, and constituent elements. However, the specific requirements of a project may reverse this norm.
XIX. Conclusion
All the differences and unique properties of aluminum and stainless steel highlighted here will help you save costs. The strongest material might not necessarily be the most suitable for your project. Rather, a material that satisfies your strength requirement will be most appropriate. And if your strength requirement is not too high, aluminum may be satisfactory. Ultimately, your project requirements and your budget are crucial in choosing the best-suited material of the two.
