Apron Feeder Main Shaft Material Selection
Main Shaft Assembly of Apron Feeder
The Apron Feeder main shaft assembly (head drive shaft assembly) is installed at the discharge head of the Apron Feeder and consists of shaft, bearing housing, sprocket, support roller and other components. The output torque of the gearbox is transmitted through the main shaft to the drive sprockets on both sides, driving the crawler chain and apron plates to run in circulation, achieving the purpose of conveying and feeding. The feature of this device is that the sprocket and support roller are connected by expansion sleeves, and the main shaft is installed inside the output shaft of the reducer, making disassembly and assembly simple and maintenance convenient.
Main Shaft Material and Manufacturing Process
40CrMo
40CrMo forging belongs to ultra-high-strength steel. It has high strength and toughness, good hardenability, no obvious temper brittleness, high fatigue limit and resistance to repeated impact after quenching and tempering treatment, and good low-temperature impact toughness.
42CrMo
42CrMo is also an ultra-high-strength alloy structural steel. Based on the excellent properties of 40CrMo, it has better hardenability and higher high-temperature strength. After quenching and tempering treatment, it can achieve a higher strength and toughness combination. Its mechanical properties are more stable under large cross-sectional dimensions, and it is suitable for the manufacturing requirements of large-load and large-size main shafts.
45# Steel
45# steel is a medium-carbon high-quality carbon structural steel. It has good plasticity, toughness and machinability. After normalizing and quenching and tempering treatment, it can achieve good comprehensive mechanical properties. Its production cost is relatively low and it is generally used for manufacturing Light-duty Apron Feeder main shafts with smaller loads and smaller cross-sectional dimensions.
Apron Feeder Main Shaft Material Selection
Main Shaft Material Selection According to Type
Light-duty Apron Feeder—-45# Steel
Material selection reason: The materials handled by light-duty feeders have smaller particle size and lower bulk density. The tensile force and impact load applied to the main shaft are relatively small, and the cross-sectional size of the main shaft is usually smaller.
Process and performance: Normalizing or quenching and tempering treatment is adopted. 45# steel has good machinability and comprehensive mechanical properties, and the material cost is low. It can fully meet the strength requirements of light-duty operating conditions and has the highest cost performance.
Medium-duty Apron Feeder—-40CrMo
Material selection reason: Medium-duty feeders need to handle materials with medium particle size and frequent starting/impact loads, requiring higher fatigue resistance and low-temperature toughness of the main shaft.
Process and performance: It must undergo forging + quenching and tempering treatment. 40CrMo is an ultra-high-strength steel with good hardenability and no obvious temper brittleness. After quenching and tempering, it has high strength, high toughness and excellent resistance to repeated impact loads, which can effectively prevent fatigue fracture of the main shaft under alternating loads.
Heavy-duty Apron Feeder—-42CrMo
Material selection reason: Heavy-duty Apron Feeder directly receives severe falling impact from large-size materials (such as large blocks of raw ore in mines). The torque and tensile force are extremely large. The diameter/cross-sectional size of the main shaft is very large, and the requirements for core hardenability and overall comprehensive mechanical properties are extremely strict.
Process and performance: Large deformation forging + quenching and tempering treatment is adopted. Based on inheriting the excellent properties of 40CrMo, 42CrMo has better hardenability. Under large cross-sectional dimensions, it can ensure a uniform combination of high strength and high toughness from the surface to the core, avoiding the problems of insufficient core hardening and insufficient toughness caused by excessive cross-sectional size.
Main Shaft Material Selection According to Operating Conditions
High drop height and large raw ore impact condition
Mining face direct feeding, crushing station bottom, unloading hopper/mine dump truck directly dumping materials onto the Apron Feeder. The material size is greater than 500mm, the drop height reaches several meters, and the main shaft diameter is usually more than 300mm.
Main failure risk: The main shaft may have bending deformation due to insufficient core toughness, or fracture under severe impact.
Material selection: The first choice is 42CrMo (forging).
Selection logic: Core hardenability must be guaranteed under large cross-sectional dimensions. After heavy forging and quenching and tempering treatment, 42CrMo can ensure that the surface and core have extremely high yield strength and low-temperature/high-temperature impact toughness, resisting severe impact.
Frequent start-stop and high-load alternating torque condition
The Apron Feeder is used for feeding before crushing in cement plants and mineral processing plants. The material size is 200–500mm. It is often operated under full-load starting with material, frequent forward/reverse rotation or variable-speed operation.
Main failure risk: Fatigue fracture occurs at stress concentration areas such as keyways and shaft fillet transitions.
Material selection: 40CrMo or 42CrMo (forging) is recommended.
Selection logic: When the main shaft cross-section is medium-sized (150mm~300mm), 40CrMo after quenching and tempering has excellent fatigue limit and resistance to repeated impact loads. If the cross-section is larger or it belongs to a key continuous production line, upgrading to 42CrMo provides higher safety redundancy.
Cold region / high-altitude operating condition
Applied to Apron Feeders in northern open-pit mines and high-altitude areas, where the winter ambient temperature is lower than -20℃ to -40℃.
Main failure risk: Low-temperature brittle fracture of steel occurs (the material loses toughness at low temperature and fractures suddenly under slight impact).
Material selection: 42CrMo or 40CrMo must be selected (and low-temperature impact test shall be added).
Selection logic: The low-temperature brittle transition temperature of 45# steel is relatively high, and it is absolutely prohibited for severe cold outdoor heavy-load conditions. 42CrMo and 40CrMo have excellent low-temperature impact toughness after quenching and tempering treatment (the impact energy requirement at temperatures such as -40℃ shall be specified in the contract).
Strong corrosion / high moisture sticky material condition
Typical applications: Wet ore with high water content, acidic or alkaline slag/underground materials.
Main failure risk: Microscopic pitting corrosion causes stress corrosion cracking, greatly reducing the fatigue life of the Apron Feeder main shaft.
Material selection: 42CrMo / 40CrMo + surface protection process (such as corrosion-resistant alloy overlay welding at shaft journals, anti-corrosion coating spraying, or quenching and tempering + local high-frequency surface hardening).
Selection logic: Conventional alloy steel itself does not have corrosion resistance. It needs to be handled through the combination of “high-strength and high-toughness matrix (42CrMo) + surface corrosion protection/strengthening technology”.
