What is the casting process of cast iron wheels?

Cast iron wheel casting requires strict control over melting, molds, pouring, and post-processing to ensure strength and precision.

The core process is as follows:

Melting: Pig iron, scrap steel, coke, and alloys (such as ferrosilicon and ferromanganese) are blended according to performance requirements (gray iron/ductile iron). Ductile iron requires the addition of magnesium/cerium alloy for spheroidization. Melting is performed in a cupola or medium-frequency furnace (1400-1500°C), impurities (sulfur and phosphorus) are removed, and the molten iron composition and temperature are tested.

Molds: Sand molds are commonly used (low cost). Resin-reinforced sand, sodium silicate sand, or metal molds can be used for complex or high-precision parts. The mold consists of a cavity (wheel shape), a gate (for molten iron intake), a riser (for feeding and preventing shrinkage cavities), and vents (for preventing air holes). Critical areas (spokes and hubs) require optimized wall thickness and cooling design.

Molding and Core Making: Sand and a binder (clay/resin) are mixed and filled into the mold, compacting to form upper and lower sand molds. Complex internal cavities (rims, hubs) require prefabricated sand cores (core box core making). The sand mold and core are assembled and securely fastened to prevent misalignment.

Pouring: The molten iron is allowed to settle and deslagging is removed. Ductile iron requires spheroidization (addition of a spheroidizing agent) and inoculation (addition of ferrosilicon). The temperature (1300-1400°C) and speed are controlled, and the casting is poured smoothly into the mold cavity along the gate. Stepped gates or bottom pouring can be used for large parts.

Sand Cleaning: The casting is cooled to below 200°C before unpacking and vibrating or hydraulically cleaning the sand. Sprues, flash, and burrs are removed, and surface sand and scale are removed by shot blasting or sandblasting.

Heat Treatment: Stress relief annealing is performed (550-650°C with slow cooling). Surface hardening (such as rim quenching and tempering, carburizing, or nitriding) may be performed for high wear resistance requirements.

Inspection and Processing: Visual inspection, nondestructive testing (such as ultrasonic testing), mechanical properties (hardness, strength), and dimensional measurement are performed. Key areas (hub bore and rim) are precision-machined to precise installation dimensions.

Process Features: Sand casting is the mainstream method, offering flexibility and low cost. Performance and cost are balanced through precise

control of composition, molds, and cooling. Ductile iron wheels undergo spheroidization and heat treatment, resulting in a balance of strength, wear resistance, and impact resistance, making them suitable for heavy-duty applications.