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Substitutability of forged aluminum and forged steel and comparison of casting processes

Submitted by anonymous » Wed 23-Jul-2025, 11:46 Subject Area: Quality Keywords: metal castings, metal forgings, forged aluminum, forged steel, casting processes	0 member ratings

In the field of metal parts manufacturing, aluminum and steel produced by forging processes are increasingly becoming a powerful alternative to casting products. This article will deeply analyze the differences between forged aluminum and forged steel in mechanical properties, production costs, application scenarios, etc. compared with cast aluminum and cast steel, and provide professional reference for engineering design and material selection.

1. Comparison of mechanical properties: significant advantages of forging process

1.1. Strength and toughness performance
The forging process significantly improves the internal structure of the material through metal plastic deformation:

·Forged aluminum (such as 6061-T6) has the following advantages over casting aluminum (A356-T6):

Tensile strength increased by 30-50% (310MPa vs 220MPa)

Elongation increased by 2-3 times (12% vs 5%)

·Forged steel (4140) compared with cast steel (SC450):

Yield strength increased by 25-40% (655MPa vs 450MPa)

Impact toughness increased by more than 50% (40J vs 25J)

1.2. Differences in microstructure
The streamlined structure of metal produced by forging brings fundamental improvements:

Grain size: The grain size of forged products is usually 1-2 levels finer than that of casting (ASTM standard)

Defect control: Eliminate defects such as casting pores and shrinkage (X-ray inspection pass rate increased by 15-20%)

Anisotropy: The lateral performance loss of forged products is 30-50% lower than that of casting

2. Process characteristics and economic analysis

2.1 Comparison of production costs

Cost factors Forging process Casting process

Mold cost High (precision mold) Medium and low (sand mold/metal mold)

Material utilization rate 60-80% 85-95%

Piece working time 3-8 minutes 10-30 minutes

Batch economy >500 pieces are more economical <500 pieces are more economical

2.2. Process applicability
Forging is more suitable for:

High stress parts (connecting rods, gears, etc.)

Thin-walled complex structures (multi-step forging required)

Precision mating surfaces (IT7-IT8 level accuracy)

Casting is more suitable for:

Oversized parts (>3 meters)

Complex internal structures (valve body, pump housing, differential housing)

Small batch special-shaped parts (rapid prototyping advantage)

3. Typical industry application replacement cases
3.1. Automobile manufacturing industry
Traditional solution: cast aluminum engine bracket

Material: A356-T6

Weight: 4.2kg

Fatigue life: 500,000 times

Alternative solution: forged aluminum bracket (6082-T6)

Weight reduction of 15% (3.6kg)

Life extended to 800,000 times

Although the unit cost is 20% higher, the life cycle cost is reduced by 30%

3.2. Lightweight application in automobiles
Replacement case of steering knuckle parts:

Original solution: cast aluminum A356-T6, weight 4.8kg, fatigue life 500,000 times

New solution: forged aluminum 6082-T6, weight 4.1kg (weight reduction 14.6%), life increased to 850,000 times

Cost analysis: $3.5 per piece, but warranty failure rate reduced by 60%

3.3. Energy equipment field
Problems with cast steel valve body (WCB):

Maximum working pressure: 25MPa

Defect repair rate: 8%

Forged steel replacement solution (F22):

Pressure capacity increased to 40MPa

Almost eliminate casting defects

Wall thickness reduced by 20%, achieving lightweight

3.4. Energy equipment upgrade
Gas turbine blade replacement:

Casting solution: IN718 castings, operating temperature 650℃, creep life 8,000h

Forging solution: IN718 forgings, operating temperature increased to 700℃, life extended to 12,000h

Technological breakthrough: Isothermal forging + δ phase control to achieve ASTM grade 10 grain size

4. Key considerations for replacement decisions
4.1 Situations where forging is preferred
Subject to alternating loads or impact loads

High fatigue strength required (>10⁶ cycles)

Harsh working environment (low temperature, corrosion, etc.)

Weight-sensitive applications (aerospace)

4.2. Scenarios where casting process is retained

Large components with a single weight of more than 3 tons

Parts with particularly complex internal structures

Small batch customized production (<100 pieces)

Not high requirements for surface finish (Ra>6.3μm)

5. Future development trends
Application of composite processes: forging + casting combined process (such as casting and forging composite forming)

Digital production: CAE-based process optimization reduces forging costs

New material development: high-strength forged aluminum (7xxx series) replaces some steel forgings

Green manufacturing: reduced energy consumption in forging process (15-25% energy saving compared to casting)

Forged aluminum and forged steel are gradually replacing traditional casting products in many application fields due to their excellent mechanical properties. In engineering practice, substitution decisions should comprehensively consider component functional requirements, production batches, cost structures and full life cycle benefits. With the continuous advancement of forging technology and cost optimization, its application scope will be further expanded, but it will still maintain a complementary and coexisting relationship with casting technology for a long time. It is recommended that manufacturers establish a detailed alternative evaluation system to select the optimal process solution for specific application scenarios.

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