How can squeeze-cast valve plates withstand long-term fatigue under high-pressure conditions?
Publish Time: 2026-01-06
In the thermal management systems of hydraulic, pneumatic, and even new energy vehicles, valve plates, as core components controlling fluid pathways and pressure distribution, are constantly subjected to harsh environments of high pressure, high-frequency switching, and temperature fluctuations. Even minor deformations, internal cracks, or seal failures can lead to reduced system efficiency, downtime, or even safety accidents. Therefore, valve plates not only need to meet initial strength requirements but also must be able to withstand long-term alternating loads (i.e., fatigue). Valve plates manufactured using squeeze casting, with their unique metallurgical structure and dense microstructure, have become an ideal solution to this challenge.Their fatigue resistance stems primarily from their near-defect-free internal structure. Traditional casting methods, such as sand casting or ordinary die casting, are prone to microscopic defects such as porosity, shrinkage cavities, and oxide inclusions during solidification. These defects may be harmless under static loads, but under repeated pressure cycles, they become stress concentration points, inducing microcracks that gradually propagate and eventually lead to sudden fracture. Extrusion casting applies high pressure immediately after the molten metal is filled into the mold, causing the melt to solidify under pressure. This effectively suppresses gas entrapment and volume shrinkage, significantly reducing internal voids and porosity. The resulting casting has a fine and uniform microstructure, approaching that of forgings, fundamentally eliminating the "breeding ground" for fatigue cracks.Secondly, the fine-grained strengthening effect significantly improves the material's toughness and fatigue limit. During extrusion casting, the combined effect of high pressure and rapid cooling promotes grain refinement. According to basic principles of materials science, the finer the grains and the more grain boundaries, the stronger the resistance to dislocation movement, thus improving the overall performance of strength and ductility. This fine-grained structure allows the valve plate to maintain rigidity while possessing a certain degree of plastic deformation capacity under high-pressure impact, avoiding brittle fracture. More importantly, in tens of thousands or even millions of pressure pulses, the fine microstructure can more evenly distribute stress, delaying the accumulation of fatigue damage and significantly extending service life.Furthermore, the high dimensional accuracy and surface quality brought about by near-net-shape forming further reduce the risk of fatigue. Extrusion casting can directly form complex internal cavities and precision mounting surfaces, significantly reducing subsequent machining. This means that critical pressure-bearing areas (such as oil passage corners and the root of sealing grooves) retain intact surface metal, avoiding tool marks, microcracks, or residual tensile stress introduced by cutting—these are often the starting points of fatigue cracks. Simultaneously, the high surface finish of the cast material and the smooth inner walls of the flow channels not only reduce fluid resistance but also decrease fretting wear caused by turbulent scouring, indirectly improving long-term reliability.Furthermore, the integrated structural design eliminates weak points in the connections. Traditional multi-piece valve bodies require bolt or welding connections, and the joints are prone to micro-leakage or stress concentration due to assembly errors or differences in thermal expansion. Extrusion casting allows for the integration of multiple functional cavities and intersecting flow channels into a single valve plate, achieving "one-piece molding." This seamless, seal-free integrated structure experiences continuous and uniform stress under high-pressure alternating loads, avoiding sudden local stress changes and fundamentally improving system sealing and structural durability.Finally, the flexibility in material selection and compatibility with heat treatment also support fatigue resistance. Lightweight alloys such as aluminum and magnesium alloys can fully utilize their high specific strength through extrusion casting while maintaining good thermal conductivity, which helps dissipate heat and reduce thermal fatigue. The dense microstructure also provides an ideal foundation for subsequent heat treatment (such as T6 solution aging), further optimizing mechanical properties.Ultimately, the ability of extruded cast valve plates to withstand long-term fatigue under high-pressure conditions does not rely on a single technological highlight, but rather on the entire chain of metallurgical control and structural optimization from melt to finished product. It uses pressure to "compact" every inch of metal, uses fine grains to "weave" a strong and tough network, and uses one-piece molding to "eliminate" potential weaknesses. While the hydraulic system operates day and night, that silent valve plate, with its inherent density and toughness, silently safeguards every precise fluid control—because true reliability is never accidental, but rather the composed response of precision manufacturing to time and pressure.
