How can the aluminum cylinder head mold withstand 200+bar pressure?

As a core component in engine manufacturing, the aluminum alloy cylinder head mold is designed to operate stably for a long time under high temperature, high pressure and complex working conditions. Under extreme conditions of 200+bar (about 2000 standard atmospheric pressure), the reliability of the mold directly determines the performance and life of the engine.

1. Material selection: dual guarantee of thermal fatigue resistance and wear resistance
The performance of the mold material is the basis for withstanding high pressure. Taking the mold designed by Yunmai (JYD) for Isuzu engine as an example, it uses H13 steel (4Cr5MoSiV1) as the core material. This tool steel is widely used in the field of hot working molds and has three core advantages:
High temperature strength: H13 steel can still maintain a yield strength of more than 500MPa at 600℃, which is far higher than ordinary alloy steel, ensuring that the mold does not undergo plastic deformation under high pressure.
Thermal fatigue resistance: By controlling the morphology and distribution of carbides, H13 steel can withstand tens of thousands of thermal cycles (from room temperature to 600°C) without cracking, and adapt to the high-frequency pressure shock of continuous engine operation.
Hardenability and tempering stability: After quenching at 1020°C + tempering at 580°C, the surface hardness of the mold can reach HRC48-52, while the core maintains toughness to avoid brittle cracking due to excessive hardness.

2. Structural optimization: pressure dispersion and stress balance design
The mold structure needs to achieve pressure dispersion through three-dimensional topological optimization. Taking a certain type of mold as an example, its design includes the following key elements:
Parting surface reinforcement: The stepped parting surface is adopted with a processing gap of 0.05mm to ensure smooth aluminum liquid filling and avoid parting surface dislocation under high pressure.
Support rib layout: A "M"-shaped support rib is designed at the bottom of the mold cavity, and the thickness gradually changes from 15mm at the edge of the cavity to 8mm in the center, which not only improves rigidity but also reduces material waste.
Cooling water channel network: Through ANSYS Fluent simulation optimization, a "spiral + cross" composite water channel is designed to ensure that the temperature gradient of the mold surface is ≤30℃/mm, reducing deformation caused by thermal stress.

3. Manufacturing process: micron-level precision control
The mold manufacturing accuracy directly affects its pressure bearing capacity. Yunmai uses the following processes to ensure a tolerance of ±0.02mm:
Five-axis linkage processing: Using the German DMG MORI five-axis machining center, the cavity is finely processed at a feed rate of 0.1μm, and the surface roughness Ra≤0.4μm.
Electrodischarge forming technology: For complex surfaces, mirror electrodischarge machining (EDM) is used, and graphite electrodes are used to achieve 0.01mm discharge gap control.
Surface strengthening treatment: The mold surface is treated with ion nitriding (IPN) to form a 0.2mm thick hard nitriding layer (HV1200), which increases the hardness by 4 times and the wear resistance by 30%.

4. Simulation verification: Pressure test from virtual to real
Mold design needs to be verified by multi-physics field simulation:
Thermal-mechanical coupling analysis: ABAQUS is used to establish a coupling model of mold-aluminum liquid-cooling system, and the stress distribution of the mold under 200 bar pressure is simulated. It is found that the maximum stress point is near the gate. By increasing the local thickness, the stress peak is reduced from 1200MPa to 850MPa.
Fatigue life prediction: Based on Fe-Safe software, the actual working condition parameters (temperature cycle 200-600℃, pressure 200bar, frequency 50 times/minute) are input, and the mold life is predicted to reach 150,000 cycles, which meets the mass production requirements.
Prototype verification: A 1:1 prototype mold is manufactured, and 100,000 cycles are tested on a 200bar hydraulic press, and the deformation is monitored to be ≤0.01mm to verify the design reliability.