Welcome to Sinostar Industrial Machinery Co., Ltd.
Welcome to Sinostar Industrial Machinery Co., Ltd.
As a common technology for metal material forming, casting achieves efficient manufacturing of complex components by injecting molten metal into the mold cavity and solidifying it. This technology integrates the principles of material solidification, fluid dynamics and thermodynamics, forming a complete scientific chain from microstructure control to macro process optimization. Based on the ASTM A802 casting quality standard and the ISO 8062 tolerance system, this paper systematically analyzes the technical characteristics and application boundaries of mainstream casting processes, and reveals the technical logic of its industrial evolution.
Traditional casting process classification relies more on empirical descriptions, while the modern system constructs a technical and economic model through quantitative parameters to achieve the calculability of process selection. This transformation has transformed process selection from experience-driven to data-driven decision-making.
●Consumable molds:Represented by sand molds and investment casting, the molding material recovery rate after a single use is ≥85%. The system cost ratio is 8-12%, which is suitable for small batch and multi-variety production. This model is similar to disposable tableware, with low initial cost but large continuous investment.
●Permanent mold: Die casting and low-pressure casting use metal molds with a lifespan of 50,000 to 500,000 times. The cost of a single mold is in a power law relationship with the output, and the marginal cost approaches zero in mass production. This metal mold can be reused, with high initial investment but low long-term use cost.
It relies on the gravitational potential energy of the molten metal to drive, and needs to maintain a minimum height difference (usually greater than 100mm) to prevent insufficient pouring. It is suitable for large castings (such as wind turbine hubs). The principle is similar to gravity-driven fluid flow, which is natural but difficult to control.
●Pressure casting:
1) Low-pressure casting (0.01-0.08 MPa): Filling speed is 0.5-2 m/s, suitable for thin-walled parts such as automobile hubs. Just like applying a slight air pressure to push the liquid, it is gentle and controllable.
2) High-pressure casting (40-150 MPa): Filling speed reaches 10-60 m/s, and can form 0.5mm thin-walled structures (such as 3C product shells). Similar to rapid filling under high pressure, it has great power but requires precise control.
●Vacuum casting: Absolute cavity pressure ≤25 kPa, effectively reducing pore defects, and is used in aerospace titanium alloy components. Just like pouring under negative pressure, it inhibits gas entrapment.
●Wet sand mold: Tolerance grade CT10-CT12 (250mm dimensional tolerance is about ±1.2mm), surface roughness Ra 12.5-25μm, suitable for agricultural machinery casting parts. This process is similar to basic sand mold molding, with low cost but limited precision.
●Resin sand mold:The minimum wall thickness can be broken through to 3mm, and the surface roughness reaches Ra 6.3-12.5μm, which meets ISO related standards. FAW Group's resin sand cylinder project achieved a weight reduction of 10.5%, and the machining allowance was reduced from 4mm to 2.8mm, verifying the economy of precision near-net forming technology. This is equivalent to using precision molds for molding, which not only improves quality but also saves materials.
●Mold life: zinc alloy mold life is 500,000-1 million molds/aluminum alloy mold life is 80,000-150,000 molds, reflecting the closed-loop optimization of materials-process-cost. Different alloys have a significant impact on mold life.
●Vacuum die casting (VDC): The porosity can be controlled at 0.1-0.8%, meeting the welding requirements of body structural parts.
●Tesla Model Y case: The rear floor integrates 70 parts into 2 through large-scale high-pressure casting (Giga Casting), reducing weight by 10% while increasing production cycle by 40%. This is equivalent to replacing 70 building blocks with one building block, significantly improving lightweight and efficiency.
●Firing process: The shell firing temperature is 950-1100℃ to achieve high temperature stability of the ceramic shell. Just like ceramic sintering, precise temperature control is required.
●Dimensional accuracy: It can reach CT5 tolerance (100mm dimensional tolerance is about ±0.32mm), and in some cases it can directly meet the final machining size requirements.
●GE LEAP engine blades: The single crystal/equiaxed crystal structure is achieved through investment casting, which significantly improves fuel efficiency and verifies the decisive influence of the process on material properties. This is equivalent to directly manufacturing high-performance near-net-shape parts.
●Speed formula:N ≈ 29900 / √D (D is the inner diameter of the casting/mm), which is used to control the centrifugal acceleration of the molten metal. Just as rotation generates centrifugal force, the speed is the key parameter.
●Wall thickness control: The wall thickness tolerance of oil casing (∅244mm) can be controlled within ±1.0mm, meeting the stringent requirements of API standards.
●Dimensional accuracy: CT8-CT9 tolerance (250mm dimensional tolerance is about ±0.9-1.3mm), close to or reaching the upper limit of traditional sand casting.
●Great Wall Motor V6 cylinder head case: The yield rate was increased to 95.5% through the lost foam process, and the processing cost was reduced by 28%, demonstrating the cost-reduction and efficiency-enhancing capabilities of digital molds and process control. This is equivalent to using vaporizable models to achieve complex inner cavity molding, combining flexibility and efficiency.
Modern casting technology is breaking through the boundaries of traditional processes and evolving towards composite and intelligent directions:
●Semi-solid casting: Combining rheological casting and thixotropic casting, high-density, near-net molding of high-melting-point metals or composite materials such as aluminum-based composite materials is achieved, similar to the precision molding of semi-solid slurries.
●Additive manufacturing assistance: 3D printing sand mold/investment mold shortens the mold preparation cycle from weeks to days. This is equivalent to digital rapid mold manufacturing, which greatly shortens the production cycle.
●Digital twin technology: Through the multi-physics coupling simulation of filling flow field-solidification temperature field-residual stress field, the number of mold trials is reduced by 60%. Just like virtual casting process simulation and optimization, accurate prediction and optimization are achieved.
The scientific process of casting technology is essentially the collaborative innovation of materials-processes-equipment. From ASTM standards to ISO tolerance systems, from empirical formulas to multi-physics field simulations, modern casting has built a complete technology chain covering microstructures to macroscopic performance. With the outbreak of lightweight, electrified, and intelligent manufacturing needs, casting technology will continue to serve as the cornerstone of the metal forming field, driving the manufacturing industry to evolve towards higher precision, higher efficiency, and lower energy consumption. This ancient and vibrant technology is reshaping the future of manufacturing with the power of science.
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