In modern manufacturing, liquid die forging technology is emerging as a powerful new force in the field of metal processing due to its unique advantages. It can produce high-quality metal parts while offering broad material applicability, efficient production processes, and environmentally friendly features. This article provides a detailed introduction to the principles, advantages, process flow, and comparisons with traditional methods of liquid die forging, helping readers gain a comprehensive understanding of this advanced manufacturing technology.
Liquid die forging is a material forming method in which molten qualified metal is directly injected into a high-strength pressure chamber or mold cavity. Then, mechanical static pressure is continuously applied, causing the molten metal to fill the cavity, crystallize and solidify, and undergo high-pressure shrinkage compensation. The final result is a part with dense internal structure, smooth appearance, and precise dimensions. This technology combines the advantages of casting and forging, retaining the ability to form complex shapes like casting, while achieving the high strength and density characteristic of forging.
For example, the traditional technique of cast cookware is essentially a simple form of liquid die forging. By pouring molten metal into molds and applying pressure, high-quality cookware can be produced. This technology is suitable not only for everyday products but also for manufacturing high-performance industrial parts.
Liquid die forging demonstrates several significant advantages thanks to its unique process. It accommodates a wide range of materials and meets diverse production needs, while providing strong adaptability to part structures and dimensions, handling complex shapes and special sizes with ease.
The material range for liquid die forging is extremely broad. During solidification, the liquid-forged parts are under compressive stress, which facilitates material flow and prevents cracking. Therefore, it is basically unrestricted by the plastic forming properties of alloys. This means that casting alloys, deformation alloys, non-ferrous metals, ferrous metals, high-temperature metals, and composite materials can all be processed using liquid die forging.
Examples include non-ferrous alloys such as aluminum, copper, magnesium, and zinc, as well as ferrous metals like steel and iron. Particularly for specialty materials with poor casting and forging properties, such as alloy steels, composites, hypereutectic alloys, and alloys prone to segregation, liquid die forging offers distinct advantages.
Liquid die forged parts exhibit excellent adaptability to structure, shape, and size. Parts with a wide range of wall thicknesses, from several millimeters to tens of millimeters, can be successfully formed. Even complex parts with highly variable wall thicknesses can achieve good forming quality through proper process design.
For instance, liquid die forging can produce cup-shaped parts, wheel cover types, fork seats, and housing components, widely used in automobiles, motorcycles, aerospace, and other fields. The technology is especially suitable for important parts with simple or moderately complex structures, near-net-shape parts requiring minimal machining, as well as parts requiring airtightness, watertightness, or complex curved surfaces.
The process flow of liquid die forging is very short. It requires no billet preparation but uses external mechanical pressure on molten metal to form parts, eliminating billet cutting, heating, and other intermediate steps. This allows for one-step part forming and significantly higher production efficiency compared to traditional forging.
For example, traditional forging requires multiple steps, including billet preparation, heating, and forging. In contrast, liquid die forging directly injects molten metal into the mold and applies pressure to complete part formation, saving time and labor while improving productivity.
Liquid die forging is an environmentally friendly manufacturing process. It consumes less material, allows waste recycling, and requires no billet heating typical in conventional forging, thus avoiding oxidation and burning losses. Moreover, it easily forms parts with holes, grooves, and steps, minimizing machining allowance and material waste, with material utilization rates up to 100%.
The equipment has small tonnage requirements and low energy consumption. It can use recycled materials to reduce raw material dependency. Also, it eliminates the need for traditional sand molds, saving complicated molding, core making, and sand treatment steps, resulting in no dust pollution, no silicosis hazards, minimal wastewater discharge, and overall low environmental impact. It is a sand-free, riser-free, high-quality, low-energy green manufacturing technology.
Compared with traditional technologies, liquid die forging stands out for its material and structural adaptability, production efficiency, and environmental benefits.
Liquid die forging can form complex parts in a single step like traditional casting and has broad applicability. Compared to conventional sand casting, it offers better workpiece quality, energy savings, reduced material consumption, and higher environmental friendliness.
For example, liquid die forging applies pressures up to 100 MPa to the molten metal to achieve rheological shrinkage compensation, making it easier to obtain dense forged parts than conventional gravity-fed riser shrinkage in casting. Even without risers, shrinkage porosity and shrinkage defects can be eliminated, resulting in dense, uniform microstructures with fine grains.
The mold used in liquid die forging is a metal mold with excellent thermal conductivity. Under high pressure, the molten metal tightly contacts the mold wall, providing high surface finish, dimensional accuracy, and minimal machining allowance, while eliminating gas gaps and enabling rapid solidification.
Additionally, liquid die forging requires no traditional sand molds, removing complex molding, core making, and sand treatment processes, avoiding dust pollution, silicosis risks, and reducing waste discharge. It is a sand-free, riser-free, high-quality, low-energy green manufacturing technology.
Though both liquid die forging and die casting use liquid metal to form parts, they differ significantly:
Filling speed: Die casting fills at tens to hundreds of meters per second, while liquid die forging fills at less than 1 m/s. This slower speed in liquid die forging avoids excessive gas entrapment and reduces porosity.
Pressure range: Liquid die forging pressure ranges from 20 to 150 MPa, whereas die casting pressures are typically 50 to 80 MPa. Higher pressure in liquid die forging helps produce denser parts.
Solidification sequence: Die casting solidifies from the gate first, limiting pressure application on the main casting during holding. Liquid die forging solidifies from the far end toward the gate, maintaining a feeding channel for pressure compensation throughout holding.
Part types: Die casting mainly produces thin-walled, complex parts, while liquid die forging is suited for thicker, important components. Liquid die forged parts have surface quality and dimensional accuracy comparable to die casting but higher internal density, allowing performance tuning by heat treatment.
Quality characteristics: Die casting parts have smooth surfaces and high dimensional accuracy but often contain internal porosity, limiting mechanical performance and causing cracking during heat treatment. Liquid die forged parts can be heat-treated to enhance mechanical properties, effectively achieving forged-like performance via casting methods.
The liquid die forging process consists of five main steps: melting, pouring, pressing, holding pressure, and demolding.
Melting is similar to conventional casting, involving melting metal materials into qualified molten metal. Strict control over temperature and time ensures proper composition and properties.
Pouring transfers molten metal into the mold cavity or pressure chamber. It can be manual or robotic, gravity or non-gravity pouring. Control of pouring speed and temperature ensures smooth cavity filling.
Pressing applies mechanical pressure on the molten metal using a liquid die forging machine. It can be direct pressing (pressure directly on molten metal in the cavity) or indirect pressing (pressure applied to molten metal outside the cavity and transmitted into the cavity). Pressure magnitude and duration are controlled to ensure full flow and solidification.
Holding pressure maintains pressure on the molten metal after cavity filling until complete solidification, preventing shrinkage defects and ensuring internal density.
Demolding removes the formed part from the mold cavity without damage, allowing for subsequent production cycles.
Thanks to its unique advantages, liquid die forging is widely applied in automotive parts, aerospace components, and industrial machinery parts, demonstrating strong adaptability and efficiency.
In automotive manufacturing, liquid die forging is widely used for wheel hubs, brakes, shock absorbers, pistons, and aluminum parts for motorcycle engines and transmissions.
For example, automotive pistons can be largely formed in one step with liquid die forging, reducing subsequent machining. The parts have better surface quality and dimensional accuracy, meeting stringent engine requirements. It also enables lightweight pistons, improving fuel economy and vehicle performance.
In aerospace, liquid die forging plays a crucial role. Key engine parts like compressor connecting rods and high-pressure valve bodies require high strength, toughness, and fatigue resistance. Liquid die forging can form these parts at lower pressures, avoiding cracks and defects common in traditional forging, while providing superior dimensional accuracy to meet aerospace standards.
In industrial machinery, parts like aluminum alloy pump bodies and shaft sleeves requiring airtightness and watertightness benefit from liquid die forging. Most shapes can be formed in one step, reducing machining. The parts have better surface quality and dimensional precision to meet industrial requirements.
Liquid die forging technology, as an advanced metal processing method, has been widely applied across many fields. It produces high-quality parts with dense structures, excellent surface finish, and precise dimensions. Offering broad material compatibility, efficient process flows, and green manufacturing benefits, liquid die forging is a promising technology for future metal manufacturing development.
