In the field of foundry industry, Centrifugal Casting (Centrifugal Casting) has become one of the key
technologies for producing high-performance castings by virtue of its unique metal molding method.
It replaces the traditional gravity casting by physical centrifugal force, which greatly improves the density
and uniformity of the material, and is widely used in the manufacture of pipelines, bearings, turbines and
other key components. This paper will systematically analyze the centrifugal casting process principles,
core advantages and its important role in modern industry.
Centrifugal casting core principles and process classification
The essence of centrifugal casting is to use the centrifugal force generated by high-speed rotation, the liquid
metal uniformly distributed on the inner wall of the mold, and ultimately form hollow or shaped castings. The
core principle can be summarized as follows:
Centrifugal force-driven molding: the mold rotates around a fixed axis at high speed (speed usually 300-3000 rpm),
the molten metal under the action of centrifugal acceleration against the wall of the cavity, gas and impurities to
the center of the pool, the formation of a high-density outer layer and removable loose inner layer.
Sequential solidification from the inside out: the liquid metal is cooled layer by layer from the surface of the mold
in the direction of the axis, and the grains are arranged in an orderly manner, which reduces defects such as
shrinkage holes and air holes.
According to the direction of the rotation axis, centrifugal casting can be divided into three major types:
Horizontal centrifugal casting: the mold rotates horizontally, suitable for the production of long cylindrical castings
(such as oil pipelines, cylinder liner), the length of a single piece up to 12 meters.
Vertical centrifugal casting: the mold rotates vertically, suitable for short diameter ratio of small ring-shaped parts
(such as gear blanks, flanges), up to 4 meters in diameter.
Tilted centrifugal casting: mold was 15 ° -30 ° inclination, taking into account the length and wall thickness uniformity,
mostly used for shaped castings.
Centrifugal casting process and technical points
A complete set of centrifugal casting process contains six key links:
1. mold pretreatment
Metal or sand molds need to be preheated to 200-400 ℃, spray high-temperature resistant coatings (such as graphite
or ceramic-based coatings), to prevent the metal from sticking and adjust the cooling rate.
2. Melting and Pouring
Alloy in the induction furnace refining to the target composition, temperature control in the liquid phase line above
50-150 ℃. Dosing ladles are injected precisely along the mold axis to avoid metal splashing.
3. Centrifugal rotational molding
The centrifugal force is usually 40-150 times the acceleration of gravity (G value). The rotation speed should be
dynamically adjusted according to the diameter of the casting, for example, Φ200mm pipe should be maintained at 1200 rpm.
4. Cooling and solidification control
The outer metal is initially solidified within 5-30 seconds, and the inner part is gradually solidified by water cooling
system or air convection. Gradient cooling strategy is adopted to refine the grain size and improve the
mechanical properties.
5. demolding and post-processing
When the casting cools down to below 300℃, the machine stops and demolds, removing the inner layer of impurities
through mechanical processing to obtain a dense metal layer. Sand casting requires additional sand cleaning treatment.
6. Quality Inspection
Ultrasonic flaw detection, X-ray inspection and other means, focusing on checking the wall thickness uniformity
(tolerance ± 1.5%) and internal defects.
Centrifugal casting four technical advantages
Compared with sand casting, die casting and other traditional processes, centrifugal casting in a number of
dimensions to show the unique value:
1. Material performance jump
Density increased by 8% -15%, tensile strength increased by 20% or more
Porosity of less than 0.3%, pressure sealing significantly enhanced
Grain size refinement to 50-100μm, fatigue life extended by 3-5 times.
2. Production cost optimization
Save risers and pouring system, material utilization rate of more than 90
Sand centrifugal casting can reduce the consumption of sand by 60%.
Precise control of wall thickness reduces subsequent machining allowance (only 1-3mm)
3. Complex structure molding capability
Preparation of bimetallic composite pipes (wear-resistant outer layer, corrosion-resistant inner layer)
Realization of gradient materials (e.g. tungsten carbide particles reinforcing the surface layer)
Production of variable cross-section castings with a wall thickness difference of more than 10:1
4. Outstanding environmental benefits
70% reduction of process waste, 25% reduction of melting energy consumption
No harmful gas emissions, cooling water can be recycled
Typical application areas of centrifugal casting
1. Energy equipment manufacturing
Oil and gas transportation pipeline: Φ50-1200mm bimetallic composite pipe, pressure-resistant grade up to 30MPa.
Nuclear power main pump impeller: 316L stainless steel castings, intergranular corrosion rate decreased by 40%.
2. Transportation core components
High-speed train brake disk: centrifugal casting ductile iron, thermal fatigue life of more than 500,000 times
Ship diesel engine cylinder liner: high phosphorus cast iron layer hardness of HB220-260
3. High-end machinery and equipment
Large rolls: the outer layer of high-chromium cast iron (hardness HRC58-62), the core for the ductile cast iron
Hydraulic valve body: dimensional accuracy up to CT6 level, inner wall roughness Ra ≤ 3.2μm
4. Emerging field expansion
Spacecraft fuel tanks: aluminum-lithium alloy thin-walled parts, 15% weight reduction
3D printing metal powder: centrifugal atomization method to prepare micro-fine powder with a sphericity of > 95%
Technical challenges and trends
Despite the significant advantages, centrifugal casting still need to break through the following bottlenecks:
Material limitations: high melting point alloys (such as tungsten, molybdenum) are prone to cracks when centrifugal molding
Equipment precision requirements: large casting mold runout needs to be controlled <0.1mm / m
Intelligent short board: process parameters still rely on experience to adjust, digital model has not yet been popularized
The future evolution of technology presents three major directions:
Composite process innovation: combined with electromagnetic stirring, laser cladding and other technologies to
improve material properties
Intelligent control system: speed-temperature adaptive adjustment platform based on the Internet of Things.
Green manufacturing upgrade: development of bio-based mold coating, waste heat recovery system
Conclusion
Centrifugal casting has redefined the technological boundaries of metal molding through the innovative application of
physical force fields. From the oil and gas pipelines thousands of meters underground to the aerospace components in the
sky, this process continues to promote the upgrading of high-end equipment. With the deep integration of new materials
and intelligent technology, centrifugal casting is breaking through the ceiling of traditional manufacturing, opening a new
chapter on the road of precision, composite and sustainability, providing more reliable manufacturing solutions for
modern industry.