What Is Stronger, Cast Steel or Forged Aluminum?

Choosing between materials is tough. Need strength but worried about weight? Let's explore if forged aluminum can truly outperform cast steel for your demanding applications.

Deciding between cast steel and forged aluminum depends on specific needs. Forged aluminum often offers a better strength-to-weight ratio. However, certain high-strength cast steel alloys can achieve higher absolute tensile and yield strengths than many forged aluminum alloys.

At SWA Forging, our slogan is "Master Southwest Aluminum Right," and we specialize in high-quality forged aluminum like large-diameter rings and discs. So, questions about strength comparisons come up often. Clients, from traders in the Middle East to sourcing managers at machining plants, always want the best material. The "stronger" debate isn't always straightforward. It involves looking at different types of strength and other important factors.

Is forged aluminum stronger than cast steel?

Material choices are complex. Need strength without excessive weight? Forged aluminum and cast steel are common, but which wins for your demanding application?

Forged aluminum can offer a superior strength-to-weight ratio compared to many cast steels. However, some high-performance cast steel alloys can exhibit higher absolute tensile and yield strength, so the answer truly depends on the specific alloys being compared and the application's priorities.

When we talk about strength, it's not just one single measure. We need to consider a few things:

• Tensile Strength: How much force it can take before breaking when pulled.
• Yield Strength: How much force it can take before permanently deforming.
• Impact Strength: How well it handles sudden loads.
• Strength-to-Weight Ratio: This is where forged aluminum often shines. An aluminum part might be significantly lighter than a steel part of similar strength, or stronger than a steel part of similar weight.
  From my experience at SWA Forging, I've seen many applications where our forged aluminum, like a 7075-T6 alloy, offers yield strengths over 500 MPa. Some common cast steels might have yield strengths around 250-350 MPa. In this case, the forged aluminum is stronger. However, there are specialized, high-strength cast steels that can exceed 700 MPa or more in yield strength. So, in terms of absolute strength, high-end cast steel can be stronger. But, steel is about three times denser than aluminum. So, if you need a part that's strong and light, forged aluminum often wins. For example, for a machinery component that needs to move quickly, the lower weight of forged aluminum can be a huge advantage, even if a slightly thicker section is needed to match the stiffness of steel.

What is stronger, forged or cast?

Choosing manufacturing methods is vital. Wondering if forging or casting yields stronger parts? The process itself significantly impacts material properties and final component strength.

Forging generally produces stronger and more durable parts than casting for the same material. This is due to the refined grain structure, elimination of porosity, and improved ductility achieved during the forging process.

The manufacturing process itself plays a huge role in a material's final strength. At SWA Forging, we specialize in forging because it imparts superior mechanical properties.
Forging involves shaping metal using localized compressive forces, often at elevated temperatures. This process does several important things:

• Refines Grain Structure: The intense pressure breaks down large grains into smaller, more uniform ones. This increases strength and toughness.
• Closes Porosity: Any tiny voids or pores present in the original metal billet are closed up, making the material denser and more consistent.
• Aligns Grain Flow: The grains align with the direction of metal flow during shaping, which can be designed to follow the contours of the part. This provides strength where it's most needed.
  Casting, on the other hand, involves pouring molten metal into a mold. While it's great for complex shapes, it can result in:
• Larger Grain Size: Cooling metal tends to form larger grains.
• Potential Porosity: Gas bubbles or shrinkage can create internal voids.
• Random Grain Orientation: Less control over grain direction.
  This is why, if you take the same aluminum alloy and forge one piece and cast another, the forged piece will almost always be stronger, more ductile, and have better fatigue resistance. This is critical for the large-diameter forged rings and discs we produce for demanding industrial applications. Our clients rely on this enhanced integrity.

Is cast aluminum stronger than steel?

Comparing materials directly is key. Is cast aluminum a viable alternative to steel for strength? Understanding their inherent properties is crucial for correct material selection.

No, generally cast aluminum is not stronger than steel when comparing typical alloys. Most steel alloys exhibit significantly higher tensile and yield strengths, as well as greater stiffness, compared to standard cast aluminum alloys.

When you put typical cast aluminum alloys head-to-head with common steel alloys, steel usually comes out on top in terms of raw strength. For example, a widely used cast aluminum alloy like A356-T6 might have a tensile strength around 230-300 MPa. A basic structural steel like A36 can have a tensile strength around 400-550 MPa, and many other steel alloys go much higher.
Steel also has a higher modulus of elasticity, meaning it's stiffer – it resists bending and stretching more than aluminum for the same shape and size.
However, this doesn't mean cast aluminum isn't useful. I often explain to sourcing managers that the choice depends on the application. Cast aluminum is much lighter (about one-third the weight of steel), has excellent corrosion resistance, and can be cast into very intricate shapes more easily and often more cheaply than steel. So, if extreme strength isn't the primary requirement, but weight saving, rust prevention, or complex geometry are important, cast aluminum is a great choice. Think of automotive engine blocks or intricate housings. But if you need sheer brute strength or high stiffness in a compact space, steel is often the go-to. Even our high-quality forged aluminum is chosen for its balance of properties, especially its strength-to-weight ratio, rather than trying to beat steel in every absolute strength metric.

What is forged aluminum?

Hearing about forged aluminum¹ is common. Curious what makes it different and desirable? This manufacturing process transforms aluminum, enhancing its mechanical properties for demanding uses.

Forged aluminum is an aluminum alloy that has been shaped by the process of forging. This involves applying localized compressive forces, which refines its grain structure and significantly enhances its strength, ductility, and fatigue resistance compared to cast or extruded forms.

Forged aluminum is essentially aluminum alloy that has undergone a 'strength-training' process. Instead of melting it and pouring it into a mold (casting) or pushing it through a die (extrusion), we take a solid piece of aluminum (a billet or preform) and shape it using immense pressure. This is typically done with hammers or presses.
The key benefits come from what happens to the metal's internal structure:

1. Refined Grain Structure: The forging process breaks down the coarse, crystalline structure of the raw aluminum into a much finer, more uniform grain structure. Smaller grains mean higher strength and toughness.
2. Elimination of Defects: Any internal voids, porosity, or inclusions that might have been in the billet get squeezed out or welded shut, leading to a denser, more reliable material.
3. Improved Mechanical Properties: As a result, forged aluminum typically shows significant improvements in:
   • Tensile and Yield Strength: It can withstand greater pulling forces.
   • Ductility: It can deform more before fracturing.
   • Fatigue Resistance: It can endure more stress cycles.
   • Impact Strength: It's tougher against sudden blows.
     At SWA Forging, this is our specialty. We make large-diameter forged rings and forged discs from alloys like 6061, 7075, 2A12, and 5083. These are used in critical applications in machinery, aerospace, and other industries where reliability and strength are paramount. Our ISO certifications (ISO9001, ISO14001, ISO45001) and the product quality certificates we provide with every order assure our clients of these enhanced properties.

Conclusion

Forged aluminum can be stronger than some cast steels, especially by weight. Forging strengthens materials, but high-strength cast steels can have higher absolute strength than even forged aluminum.