Comparison dimension

Free Forging Process

Multi-directional forging process

Explanation of the Essential Difference

Forming Method 

Unidirectional forging (vertical hammering) 

Simultaneous multi-directional extrusion (horizontal + vertical) 

Free forging only modifies external shape without actively forming internal structure; multi-ram forging enables one-shot forming of complex internal cavities 

Metal flow

Significant surface deformation, minimal core deformation 

Uniform overall deformation, especially thorough extrusion in cross-bore region 

Free forging results in limited metal flow in the core, leading to poor structural density; multi-ram forging ensures active forming of the cross-bore region with continuous flow lines 

Microstructural Uniformity

Fine structure on surface, coarse core with segregation 

Uniformly fine structure throughout, particularly full martensite at cross-bore surface 

Free forging suffers from inherent "good surface, weak core" limitation; multi-ram forging delivers consistent internal and external properties with no performance shortfalls 

Heat Treatment Response 

Slow core cooling, prone to ferrite formation 

Cross-bore geometry accelerates cooling, achieving full martensitic structure 

Free forging yields suboptimal heat treatment results in the core; multi-ram forging leverages structural advantages to optimize heat treatment microstructure 

Performance weak area

Cross-bore region in the core (exposed during final machining) 

No clearly weak areas; overall performance is well-balanced.

The weak zone in free forging coincides precisely with the critical stress region during valve box service; multi-ram forging eliminates this structural vulnerability 

Material Utilization 

Low (substantial stock removal required during machining) 

High (near-net shaping, reducing machining volume)

Free forging requires significant machining stock; multi-ram forging minimizes material removal, reducing costs