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 tabulated below: CastingForgingCasting involves heating the metal to a liquid state.In Forging, heating (if required) will be below the recrystallization temperature.There is no size limit; as casting involves melting the material and pour it into proper mold.With an increase in size, Forging becomes not-feasible due to the requirement of higher compressive forces.Casting can easily produce complicated parts.Producing complicated parts using the forging method is highly difficult.Economic Casting itemsForged Products are CostlyWide Material RangeSelected Material RangeMechanical Properties are comparatively inferior to forged products. Low Impact Strength and Tensile Strength.Superior Mechanical Properties than casting products. High impact and tensile strength.Grain 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 productsHeavierThe machining requirement is less as the mold is approximate to the required shape.Forging parts need more secondary machining to match the final shape.Higher production rate once the mold is preparedLower production rate.The reliability of cast parts is less.Highly reliableHigh Labour Cost as precision control is required to avoid defects.Low Labour cost.Preferred in the low-end applicationsPreferred for high-end applications.Table: Casting vs Forging-Difference between casting and Forging