Casting vs Forging vs Welding: Cut 30 % Cost on Your Next OEM Part

Today, let's join SMEMACH in exploring the efficiency trade-offs between welding, casting, and forging in the manufacturing process selection of mechanical parts.

As the global mechanical manufacturing sector accelerates towards high-precision and high-performance development, the selection of manufacturing processes for mechanical parts has become a crucial factor influencing the overall performance, operational costs, and usage efficiency of equipment.

Currently, the industry faces numerous challenges: Firstly, heavy-duty components need to strike a balance between lightweight design and high strength. Secondly, complex working conditions demand that key components possess excellent impact resistance. Thirdly, the small and medium-sized repair market urgently requires cost-effective spare part solutions.

Welding, casting, and forging, as the three core processes for metal forming, are closely linked to the actual needs of various mechanical equipment. The welding process achieves framework weight reduction through bimetallic composite structures. The casting process meets the production demands of complex shell-type parts with its low-cost advantage. The forging process, on the other hand, provides irreplaceable mechanical performance support for critical components such as transmission systems. However, process selection is not a simple technical trade-off but requires a comprehensive consideration of multiple factors, including material properties, production volume, cost thresholds, and service environments.

I. Comparison of Process Characteristics

(1) Welding Process

Core Advantages:

· Saves labor and materials, reducing material and man-hour costs by 12% - 20% compared to riveting.

· Enables the fabrication of bimetallic structures, effectively conserving the use of precious metals.

· High production efficiency, making it highly suitable for mechanized and automated production modes.

Limitations:

· Residual stresses after welding may cause component deformation, affecting dimensional accuracy.

· The cost of welding complex structures is relatively high.

Typical Application Scenarios: Large structural components (such as mechanical frames) and bimetallic parts.

(2) Casting Process

Core Advantages:

· Capable of manufacturing parts with complex internal cavities (such as engine cylinder blocks) to meet diverse design requirements.

· Wide range of raw material sources, resulting in relatively low costs.

· Suitable for mass production, effectively reducing unit costs.

Limitations:

· Mechanical properties are inferior to those of forged parts, with a relatively coarse structure.

· Prone to defects such as porosity and shrinkage porosity, affecting part quality.

Typical Application Scenarios: Complex-shaped parts such as boxes, shells, and gear blanks.

(3) Forging Process

Core Advantages:

· Dense structure with excellent mechanical properties, featuring high strength and toughness.

· High material utilization rate, reducing raw material waste.

· Suitable for manufacturing high-load components, ensuring stable operation of equipment under heavy-duty conditions.

Limitations:

· High equipment investment, leading to relatively high production costs.

· Incapable of forming complex internal cavities, limiting the manufacturing of parts with intricate internal structures.

Typical Application Scenarios: Parts subjected to heavy loads, such as gears, shafts, and crankshafts.

II. Analysis of Process Selection for Mechanical Part Spare Parts

(1) Large Structural Components or Parts Requiring Bimetallic Structures

If the part is a large structural component or requires a bimetallic structure (such as mechanical frames and transmission components), the welding process is the preferred choice.
Reasons: 

Welding enables the "assembly of small parts into large ones," effectively saving material costs. Bimetallic structures (such as steel-aluminum composites) can reduce weight while ensuring strength.
Example: 

The suspension system of a certain mechanical device adopts a welded structure, successfully reducing weight while maintaining strength.
Notes:

Strict control of welding parameters is required to avoid component deformation caused by residual stresses. If the performance requirements for spare parts are not extremely high, the welding process is the first choice, and it can also deliver good results when combined with CNC machining.

(2) Blank Parts with Complex Shapes and Internal Cavities

If the part is a blank with a complex shape and internal cavity (such as engine cylinder blocks and gearbox housings), the casting process is the preferred option.
Reasons: 

Casting can manufacture parts with complex shapes at a low cost and is suitable for mass production. Processes such as sand casting and die casting can meet the production requirements of different parts.
Example: 

The engine cylinder block of a certain mechanical device is manufactured using the casting process, reducing the amount of cutting and lowering production costs.
Notes: 

The melting process needs to be optimized (such as increasing temperature and enhancing stirring) to reduce defects such as porosity and cracks. If some equipment has weight reduction requirements for spare parts, depressions can be created on the surface to achieve weight reduction without affecting the service life and performance of the spare parts. Using precision casting (investment casting) process, good results can be achieved without the need for CNC machining at the weight reduction depressions.

(3) Parts Requiring Heavy Load, Impact Load, or High Mechanical Properties

If the part needs to withstand heavy loads, impact loads, or has high mechanical property requirements (such as gears and transmission shafts), the forging process is the preferred choice.
Reasons: 

Forging results in a dense metal structure, with mechanical properties (strength and toughness) significantly superior to those of cast parts, making it suitable for manufacturing critical components.
Example: 

The gears of a certain mechanical device are manufactured using the forging process, improving wear resistance and service life.
Notes: 

The parting line needs to be reasonably designed to avoid defects such as flash and burrs. Many customers have high requirements for the surface finish of spare parts, and the surface finish of forged parts is superior to that of other processes, with high durability of forged spare parts.

III. Comprehensive Recommendations and Cases

(1) Recommended Combined Processes

· Cast Blank + Forged Critical Parts:For example, combining a mechanical gearbox housing (cast) with internal gears (forged) can enhance overall performance while keeping costs under control.

· Welded Structure + Local Forging Reinforcement: For instance, combining a mechanical suspension arm (welded) with critical connection parts (forged) can effectively improve equipment reliability.

(2) Typical Cases

· John Deere: Adopted ductile iron castings in mechanical transmission boxes, reducing costs by 40% compared to steel parts while improving performance through heat treatment.

· A Chinese Group: Used a welded structure in large mechanical frames, combined with CO₂ gas shielded welding, achieving high production efficiency and low deformation.

Based on considerations of manufacturing processes, whether you are concerned about cost, performance, or safer and more efficient usage requirements, we can find the most suitable manufacturing process for you. As a leading enterprise in the spare part manufacturing industry, SMEMACH welcomes your inquiries if you have any questions about any process.

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