Steel Castings
Steel Casting Methods
Sand Casting
Sand casting is one of the most popular and simplest types of casting, and has been used for centuries. Sand casting allows for smaller batches than permanent mold casting and at a very reasonable cost. Not only does this method allow manufacturers to create products at a low cost, but there are other benefits to sand casting, such as very small-size operations. From castings that fit in the palm of your hand to train beds (one casting can create the entire bed for one rail car), it can all be done with sand casting. Sand casting also allows most metals to be cast depending on the type of sand used for the molds.
Sand casting requires a lead time of days, or even weeks sometimes, for production at high output rates (1–20 pieces/hr-mold) and is unsurpassed for large-part production. Green (moist) sand has almost no part weight limit, whereas dry sand has a practical part mass limit of 12,000 lbs. The sand is bonded together using clays, chemical binders, or polymerized oils (such as motor oil). Sand can be recycled many times in most operations and requires little maintenance.
Centrifugal Casting
In this process, molten metal is poured in the mold and allowed to solidify while the mold is rotating. Metal is poured into the center of the mold at its axis of rotation. Due to centrifugal force the liquid metal is thrown out towards the periphery.
Centrifugal casting is both gravity- and pressure-independent since it creates its own force feed using a temporary sand mold held in a spinning chamber at up to 900 N. Lead time varies with the application. Semi- and true-centrifugal processing permit 30–50 pieces/hr-mold to be produced, with a practical limit for batch processing of approximately 20,000 lbs total mass with a typical per-item limit of 5 to 10 lbs.
Industrially, the centrifugal casting of railway wheels was an early application of the method developed by the German industrial company Krupp and this capability enabled the rapid growth of the enterprise.