Crankcase manufacturing needs to select a process combination according to the material (such as aluminum alloy, cast iron), batch size, and performance requirements.
Traditional casting and machining are still the mainstream, but additive manufacturing has shown potential for lightweighting and integrated design.
Casting process
Casting is the most popular process in crankcase manufacturing, especially for complex geometries and mass production.
Chill Casting Technical features
The aluminum alloy melted at high temperature is injected into a water-cooled mold to quickly solidify and form a high-density structure.
For example, the aluminum alloy crankcase of the Mercedes-Benz M139 engine adopts this process, which can withstand a high load of 416 hp/500 Nm while ensuring light weight and strength.
Advantages
Grain refinement, low porosity, suitable for high-performance engines.
Case study
The weight of the crankcase of cold casting is reduced by 10%-15% compared with traditional casting, and the tensile strength is increased by 20%.
Low-Pressure Die Casting (LPDC)
Technical characteristics
Liquid metal slowly fills the mold under low pressure, and forms a closed structure with the sand core.
For example, the ALUSIL® technology uses the LPDC process to produce aluminium crankcases without additional cylinder bore reinforcement and the AlSi17Cu4Mg alloy for increased rigidity (12% increase in Young’s modulus).
Advantages
Low turbulence filling reduces porosity, directional solidification optimizes microstructure.
Applications
V-arranged engine crankcases, especially for designs that require high-precision cooling channels.
Die Casting crankcase manufacturing technical
High-pressure injection of aluminum alloy into steel mold, rapid prototyping.
For example, an aluminum alloy crankcase reduces the crater defect rate from 8% to 0.5% by optimizing the heat dissipation design of the mold (such as the heat dissipation mesh of the lateral slider).
Challenges and optimizations
The deep cavity structure is prone to heat concentration, and the use of inlaid core design.
such as dynamic mold insert cooling channel improves heat dissipation efficiency and prolongs the life of the mold.
Sand Casting Material Selection
Compacted graphite cast iron (e.g. S415) combines high strength and thermal conductivity for use in extended-range engine crankcases.
By optimizing the gating system (sprue, sprue) and the number of sprues, sand holes and porosity are avoided.
Aluminum alloy casting
In gravity pouring, the fishbone diagram analysis method was used to optimize the sand core fitting gap, and the proportion of core fracture defects was reduced from 15% to 0.2%.
Forging process
Forging serves primarily in applications requiring high strength and reliability.
Although manufacturers seldom use it for integral crankcases, they commonly employ it in producing crankshafts.
Forged steel crankcase Marine application
The ship crankcase uses forged steel with a tensile strength of 400-1000 N/mm², must undergo explosion pressure testing, and requires explosion-proof valves.
Advantages
The grain structure of forgings is dense, and the fatigue resistance is better than that of castings.
Lightweight forging of crankshafts Example
The crankshaft of the M139 engine is made of forged steel, combined with a lightweight design (such as a hollow balance weight) to reduce inertia forces and improve speed response.
Process Trend
Hot Die Forging Press
Electro-hydraulic hammer automatic line, combined with precision shearing blanking and roll forging billet, forms a flexible manufacturing system (FMS).
Welding process
Welding is mainly used for the assembly, repair and manufacture of special structures of crankcases.
Component welding
Ship crankcase: semi-automatic underwater arc welding, key welds need to pass X-ray and ultrasonic inspection.
Repair welding
If the depression depth of the cast steel crankcase exceeds 0.1t, use argon arc welding for repairs and avoid operating in the cross area
Structural optimization Case
Engineers modified the Mozambique railway 12-cylinder HHP crankcase with welding fixtures to achieve low-cost production without additional investment in molds.
