This article examines the two main processes for producing connecting rods: casting and forging. After looking at the processes' benefits and drawbacks, you will better grasp which manufacturing process is most appropriate for their application.
The connecting rod is the crucial part of an engine that joins the piston to the crankshaft. They must be sturdy and resilient enough to endure tremendous strains and temperatures during engine operation.
Connecting rods can be produced via casting or forging, each with benefits and drawbacks. In this manual, we'll look at how each method is made and analyse how they differ from one another.
You will better understand the casting and forging processes at the end of this article. You will be able to decide which approach is best for you.
Did you know? India is one of the world's largest connecting rod manufacturers, with a significant global market share.
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Understanding the Connecting Rod Manufacturing Process
Connecting rods are manufactured depending on the material used. Connecting rods are made of steel alloys such as chrome, nickel, and aluminium.
One common method is hot forging. This involves several steps, including the hot forging of a connecting rod rough forging, a heat treatment and a machining operation.
The weight of a connecting rod is significant as it affects the balance of the engine. To keep the engine balanced, connecting rods are appropriately matched in sets of equal weight. The resultant power increases with connecting rod and piston weight, while vibration decreases as reciprocating weight decreases.
Engine connecting rods are crucial because they link the piston to the crankshaft. They transfer the force created when gasoline burns in the cylinder to the crankshaft.
In other forms of machinery where a reciprocating motion needs to be changed into a rotational motion, connecting rods can be employed. For instance, it is used in steam engines, pumps, and compressors.
Major global automotive connecting rod market players include Albon Engineering & Manufacturing Plc. These players continuously work to improve engine components and provide consumers with a better experience. This development is expected to reduce fuel consumption and emissions.
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Methods for Connecting Rod Manufacturing Process
Over the years, the production methods of connecting rods have constantly changed. Forging techniques include casting, metal powder, hammer, and press forging.
Hammer forging was regarded as one of the best forging techniques in the early years of the development of the auto industry. Due to higher quality and tolerances, manufacturers began to use mechanical presses to replace hammers.
Another method used is powder forging. This method has the advantage of being able to forge the connecting rod cover together with the connecting rod, thus saving manufacturing costs. The forged steel connecting rod is stronger than the powder metallurgy rod.
1. Forging Method
Forging is a metalworking process in which the useful shape of a metal component is obtained by using tools and dies to apply compressive forces to a solid state.
The most popular forging method is hot forging. Hot forging is performed at a temperature higher than the metal's recrystallisation temperature. The temperature at which new metal grains form is called the recrystallisation temperature. Extreme heat is necessary to avoid strain hardening of the metal during deformation.
The forged connecting rod process includes several steps: blanking, heating, roll forging, closed die forging, trimming punching, heat treatment, shot blasting and correction.
Here is a short description of the various steps of hot forging:
- Blanking: This is the first step in the process, where the raw material is cut into the desired shape and size for forging.
- Heating: The blank is then heated to a temperature above its recrystallisation temperature to make it more malleable and easier to shape. Medium-frequency induction heating is often used for this step.
- Roll Forging: The heated blank is then passed through a series of rollers to shape it into the desired form.
- Closed Die Forging: The shaped blank is then placed into a die and compressed to its final shape.
- Trimming and Punching: Excess material is trimmed off, and holes are punched where needed.
- Heat Treatment: The forged connecting rod undergoes heat treatment to improve its mechanical properties, such as strength and toughness.
- Shot Blasting: The connecting rod surface is cleaned using shot blasting to remove any scale or other impurities
- Correction: Any final corrections or adjustments are made to ensure the connecting rod meets the required specifications.
2. Casting Method
Casting is a manufacturing process where liquid materials are poured into a mould and allowed to solidify into a shape. The solidified part is then removed from the mould to complete the process.
Sand is used as a moulding material in the metal casting technique known as sand casting. Foundries are specialised factories where sand castings are made. The process of "sand casting" is used to create more than 70% of all metal castings.
Here are the steps involved:
- Patternmaking: A pattern is created in the shape of the desired final product. This pattern is usually made of high-precision metal.
- Moulding: The pattern is placed in a flask and packed with sand to create a mould. The sand is compacted around the pattern to ensure that it holds its shape.
- Melting: The metal to be cast is melted in a furnace and brought to the correct pouring temperature.
- Pouring: The molten metal is carefully poured into the mould and allowed to solidify.
- Cooling: The metal can cool and solidify entirely within the mould.
- Removal: Once the metal solidifies, the mould is broken apart, and the casting is removed.
- Finishing: The casting and any excess material are cleaned. Further finishing processes may be required, such as machining or heat treatment.
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Casting vs Forging
|
Basis |
Casting |
Forging |
|
Process |
Casting involves heating the metal into a liquid state and pouring it into a mould, solidifying it into the desired shape. |
Forging involves shaping the metal while it is still in a solid state by applying compressive forces through dies and tools. |
|
Material properties |
Forging can improve the mechanical properties of the metal, such as strength and toughness, due to the deformation and grain alignment that occurs during the process. |
Cast parts may have less strength and toughness than forged parts due to defects such as porosity or inclusions. |
|
Size and complexity |
Casting can produce parts with complex shapes and intricate details that may be difficult or impossible to achieve through forging. |
Forging is better suited for producing parts with simple shapes and large sizes. |
|
Cost |
casting may be more cost-effective for producing small, complex parts in large quantities. |
Forging may be more cost-effective for producing large, simple parts in smaller quantities. |
|
Material usage |
Forging generally uses less material than casting to produce a part of the same size and shape.
This is because the forging process involves shaping a piece of metal already close to the part's final shape. |
While casting involves pouring molten metal into a mould and removing any excess material. |
|
Production speed |
The production speed for casting can be slower than forging as it involves multiple steps, such as mould making, pouring, solidification, and finishing. |
Forging can produce parts more quickly because it involves shaping the metal rather than moulding it. |
Conclusion
An internal combustion engine's connecting rod is an essential part. It joins the piston to the crankshaft and changes its linear motion into its rotating action. Due to the fact that it must be able to endure extremely heavy loads and convey a significant amount of power, it becomes a crucial component of the engine's design.
Connecting rods are typically made of forged steel or aluminium alloy. They are precisely matched in sets of similar weight to maintain engine balance.
Connecting rods are widely used in heavy machinery in rotary motors and other industrial equipment. With the increasing mechanisation of industrial output, the global demand for connecting rods will be expected to increase.
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