casting or forging – What Is Piping

Both Casting and Forging are part of the mechanical manufacturing process. Both Casting and forging are widely used in the metal fabrication process and produce thousands of useful components. The method of production; whether casting or forging is decided based on end-use and required properties of the product or component. In this article, we will explore the key differences between casting and forging processes; i.e Casting vs Forging Processes. What is Casting? In the casting process, the metal is melted to liquid form and then it is poured into a mold or die to cool and solidify. The metal in solid form takes the form of the mold. Casting is highly beneficial for mass production of parts as the same mold can be re-used. Fig. 1 shows typical steps followed in Sand Casting Process. Fig. 1: Typical Sand Casting Process Steps What is Forging? In forging, a hammer, press or die uses the compressive force over a metal billet to deform it in the desired shape. The hammering effect produces superior mechanical properties, eliminating defects, porosity, inclusions, etc. Depending on how the metal if deformed, forging can be of two types. In cold forging, the metal is deformed at room temperature; whereas in hot forging, the metal is shaped in a heated condition. Fig. 2 below shows typical steps in the forging process. Fig. 2: Typical Forging Process Steps Casting vs Forging: Which one is better? The selection of the production process depends entirely on the cost involvement and end-use of the part. Where higher strength and rigidity is required, forging is the ideal choice. But for complex shapes, including spaces, Casting is the better option. Studies have found that: The tensile strength of cast products is around 26% lower than their forging counterparts.Forging products exhibit approximately 37% higher fatigue strength as compared to cast products. Factors affecting selection between Casting and Forging The following factors govern the selection of casting or forging (casting vs forging) for a part: Material QuantityEconomic ConsiderationTooling costsMachining CostDesign of the part (Simple/Complex)Tolerances requiredMechanical properties Requirement (Ductility, fatigue strength requirement)Metal specification (Normal Steel or Custom alloy Materials)Surface finish requiredDelivery requirements Normally its preferable to use casting for large and complex products and forging for simple and smaller size products. Differences between Casting and Forging: Casting vs Forging Fig. 3: Casting vs Forging The Key differences between Casting and Forging are: Metal Casting vs Metal Forging: Mechanical Properties Metal products produced from forging have higher strength and toughness than metal processed in castings. The metal working process by pressing and hammering during forging attributed to the increased strength. On the other hand, the mechanical properties for products made by casting process are relatively inferior. Casting products possess low impact strength and tensile strength. Forging vs Casting: Process Casting process involves heating the metal into liquid state and then pouring the liquid metal in a die or mold. Whereas in forging, heating of material if required is below recrystallization temperature. Casting vs Forging: Process Limitations A wider range of products are manufactured using casting process as it involves only melting the material and pouting into proper mold. As the casting process is easier, complex shapes can easily be produced. Practically, any material can be cast. Hence, casting process provides greater flexibility. However, forging has size limitations due to difficulty in shaping a metal in a solid-state. There’s a limit on the material size and thickness as changing the metal’s shape is more difficult with forging. Other differences between forging and casting are tabulated below: CastingForgingCasting items are cheaper than forged items.Forged Products are costlier than cast products.Wide Material Range is suitable for casting operation.Forging has a selected material rangeGrain Structure of casting products is random.Grains of forged products are aligned in one direction.For prodicing hollow cavities, casting is the best optionForging is not suitable for hollow spaces.Casting products are relatively lighter in weight as compared to forged productsForging process produces heavier products as compared to casting.The machining requirement of cast products are less as the mold is approximate to the required shape.Forging parts need more secondary machining to match the final shape.Casting provides higher production rate once the mold is prepared. So, the mass production of a specific component by casting method is quite easy.In forging, the production rate is lower. Mass production is difficult and time consuming in forging. The reliability of cast parts is less.Forged components are highly reliableCasting requires high labor cost as precision control is required to avoid defects.Labor cast is low in case of forging process.Casting is preferred in the low-end applications and products requiring highly complex shapes.Forging is widely used for high-end applications and for components not requiring complex shapes.In casting process, custom alloy addition to change the material composition and properties is possible.Forging is not flexible for new material additions.Cost of tools in casting process are cheaper.Forging dies are costly as compared to casting molds.Any modifications in component design and molds are easier and quicker to implement in casting process.In forging, modifications in components are very difficult.The density of cast component may not be uniform.Parts produced in forging possess uniform density.Table: Casting vs Forging-Difference between casting and Forging