What Is Steel Casting? Fundamentals & Use Cases

What is Steel Casting?

A casting is a part made by pouring liquid metal (molten steel) into a mold, which becomes the final intended design. Castings can be produced in a wide variety of shapes, often with intricate features and complex geometries to meet specific design needs of manufactured products with use cases for many industries, including construction, mining, oil & gas and more.

Steps of Steel Casting:

• The casting process begins with a pattern (master tool) that resembles the desired geometry of the part to be made yet split in halves.
• A mold is made by making an impression of the pattern with molding material; usually loose sand mixed with a self-hardening binder.
• The mold halves are assembled.
• Metal is poured into the cavity in the mold and allowed to solidify and cool.
• When cooled, the casting is broken away from the mold materials; this is called “shake-out.”
• The casting is then processed through various steps (including grinding, heat-treating and inspections), until it passes specification and can be shipped.

Although steel can be difficult to melt, its chemical composition allows for greater flexibility and complexity in design along with increased strength.

Steel Casting with Nucor: POK

Founded in 1894 and acquired by Nucor in 2018, POK, S.A. de C.V. (POK), is a fully integrated precision castings company with a facility in Guadalajara, Mexico. POK produces complex castings and precision machined products intended for the oil and gas, mining and sugar processing industries.

POK produces a wide array of precision castings using steel, bronze, iron and specialty exotic alloys. Throughout its history, POK has developed proprietary technology and innovative engineering solutions that render complex steel castings through sand and investment molding processes.

Need a one-stop destination for all your casting needs? POK offers comprehensive turnkey solutions for every stage of the casting process, ensuring a seamless and hassle-free experience for our valued customers. From initial design to final product shipment, we handle it all under one roof, saving you time, effort and resources.

Our Product Development Center was specially designed to fast-track first-article development for steel casting, and alongside our internal pattern shop, we can manufacture either permanent tooling or rapid prototyping solutions to meet your project needs.

We use a wide range of materials for tool and pattern making:

• Wood
• Resin
• Foam
• Aluminum
• Rapid prototyping (FDM Fused Deposition Modeling or SLA Stereolithography)

Nucor can develop casting molds based upon your needs and specifications through sand casting, investment casting, and POK cast. Our 5+ induction furnaces vary in size, giving us the flexibility to make small heats and large heats depending on your needs. Additionally, our 10+ heat-treating furnaces that vary in size help us obtain the mechanical properties best suited for your products. We partner with local and international suppliers to be able to offer any special coatings or special heat-treat services.

With proven experience, our expert machinists are here to convert finished castings into turnkey solutions. With more than 35 CNC turning and milling machining centers both vertical and horizontal, we can deliver machined products to customers like you to reduce supply chain logistics and lead times.

Learn more about POK

Characteristics of Steel Casting

Casting provides a large grain size, flexible geometry, isotropic properties, high silicon for fluidity (chemistry for casting properties) and leverages shape for strength.

What are the benefits and characteristics of steel casting for design and manufacturing?

Design in Steel Casting:

• Freedom to add or reduce thickness as needed
• Ability to produce essentially any shape or design
• Easily reduces design stress
• Creates complex internal designs using cores
• Welding efficiency when compared to fabrications:
  • No metallurgical notch from base metal to weld
  • No heat affected zone (HAZ) in critical areas

Manufacturing in Steel Casting:

• Readily machinable
• Smaller batch sizes compared with other methods
• Quantity flexibility: 1 to 100,000 pieces
• Unlimited ranges of chemistries
• Fast time to market:
  • Patterns and molds can be rapidly 3D printed without tooling committed

In comparison, wrought materials have smaller grain size, orthogonal geometry, properties with forming direction, chemistry for properties and strength from material properties. Closed-die forging also does not allow for as much complexity, has higher tooling and production costs and slow prototyping.

What Makes a Good Steel Casting Candidate?

Curious to know if you should implement steel casting into a future project? Ideal steel casting projects fall into the following categories:

Structural Parts with Complex Shapes:

• Nonlinear or asymmetric geometries
• Curved or angled profiles
• Hollow interiors (difficult to machine)

Part with Joints:

• Welded joints
• Mechanically fastened joints
• Castings eliminate joining processes, reduce part count, decrease tolerance stack-up and minimize leak paths

Other Characteristics:

• Expensive alloys
• Castings will reduce material costs and eliminate machining operations

Case Study: A Fabrication Conversion

The Fundamentals of Steel Casting webinar provides a case study featuring “Yamato Roller Table Bearing Housing Conversion from Fabrication to Casting.”

The case study reveals how the conversion enabled an increased radius to reduce stress and improve solidification, an added rib for strength and directional solidification, a raised machining stock to avoid an interrupted cut during machining, and optimization for soundness and an improved cost-effective pattern.

The Nucor-Yamato and POK engineering teams worked closely together to ensure an optimized design both for functionality and manufacturability.

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