With the rapid development of prefabricated construction, precast concrete magnets have become the "invisible heroes" of modern construction sites. These seemingly simple magnetic devices are actually key tools for ensuring precise formwork positioning and improving construction efficiency. However, with a wide variety of magnet types and specifications on the market, how do you choose the best product for your project?
Why is magnet selection so critical?
Precast concrete magnets, using strong magnetic attraction to replace traditional welding and bolting methods, have revolutionized formwork installation. They securely attach steel formwork to platforms or beams in seconds, eliminating the need for drilling and preventing damage to the formwork platform, extending the life of the formwork by over 30%. Importantly, these magnets can be reused thousands of times, significantly reducing labor costs and material loss. However, improper selection can lead to formwork displacement, concrete leakage, and even safety accidents.
Core Components of Precast Concrete Magnets
1. Steel Housing
The housing is typically made of high-strength, corrosion-resistant steel. It protects the magnet from impact, moisture, and chemical attack, which is critical for long-term use in demanding construction environments. A well-constructed housing ensures consistent clamping force and a longer product life.
2. Neodymium Core
The core of each precast magnet is a rare earth neodymium magnet, renowned for its superior holding power. Unlike ferrite magnets, neodymium magnets are compact and have a high force density, ensuring a secure hold even under vibration or heavy formwork loads.
3. Release Lever or Button
A built-in mechanical release system (typically a lever or button) enables quick, tool-free installation and removal. This feature improves efficiency, reduces fatigue, and minimizes the risk of formwork misalignment.
Four core selection factors
1. Magnetic Strength and Load Requirements (The Core of the Core)
- Light-Duty Applications (Window Frame Covers, Small Wall Panels): Choose 900kg-rated magnets, such as compact magnetic boxes.
- Medium-Duty Applications (Standard Wall Panels, Column Formwork): 1350-1800kg-rated magnets are the best choice.
- Heavy-Duty Applications (Large Floor Slabs, Bridge Components): 2100kg-rated magnets or higher are essential, such as those used in heavy-duty formwork systems.
2. Match the magnet type to the application scenario
| Magnet Types | Best Application Scenarios | Unique advantages | Typical Products |
| Template Magnet Boxes | Composite panels, small wall panels | Simple structure and high cost performance | 600-800kg base magnetic box |
| Stepped Magnets | High side molds, special-shaped components | Anti-slip design, adaptable to uneven edges | Customized stepped magnets |
| Angle Template Magnets | Beam-column joints, wall corners | Precise 90-degree fixing, explosion-proof mold | Reinforced corner magnets |
| Magnetic Chamfer Strips | Wall panel edges, decorative lines | Flexible and bendable, creating precise 45-degree chamfers | Rubber magnetic strips |
| Plug-In Magnets | Embedded parts and pipeline fixing | With threaded connection, precise positioning | Rubber cover with embedded magnets |
| Magnetic Template Systems | Large wall panel production line | Integrated guide rails for quick assembly and disassembly | Suction cup system with steel rails |
Solutions for Special Scenarios:
- Curved surfaces: Use round magnets or flexible magnetic chamfer strips
- Extra-long templates: Strip magnets provide continuous and uniform attraction
- High-temperature steam curing environments: Requires specially manufactured high-temperature-resistant neodymium magnets (operating temperature >80°C)
3. Environmental and Operational Factors
- Temperature Sensitivity: Conventional neodymium magnets begin to demagnetize above 80°C. High-temperature-resistant models must be used near steam curing kilns.
- Surface Condition: Rust, oil, or concrete residue can reduce magnetic force by up to 40%. Ensure the contact surfaces are smooth.
- Corrosion Protection:
- Stainless steel housings are preferred for humid environments (although the cost is 30% higher, the lifespan is doubled).
- High-strength carbon steel housings are suitable for dry locations (a cost-effective option).
- Safety Margin: The actual load should not exceed 70% of the magnet's rated value. An additional 30% safety margin should be added for vibration conditions.
4. Golden Criteria for Supplier Selection
- Certifications: Prioritize manufacturers with ISO 9001 and CE certifications.
- Engineering Support: Suppliers offering magnetic simulation and on-site commissioning services can reduce selection risk.
- Customization Capabilities: For special projects (such as special-shaped components), select manufacturers that support customized production.
Scenario-Based Selection Guide
1. Residential Composite Panel Production: Recommended 600-800kg magnetic cassettes, spaced 1-1.5 meters apart – This offers optimal cost performance and allows for single-mode positioning within 30 seconds, making it particularly suitable for multi-family production.
2. Large Wall Panel Production Line: Suitable for 1350kg magnetic cassettes and magnetic guide rail systems – Suitable for vibration table applications, enabling 5-minute formwork changeovers when combined with a crane.
3. Special-Shaped Component Production (Double T-Beams, Arches): Recommended: A combination of stepped magnets and U-shaped magnets – Precisely secure complex curved surfaces. A project in China successfully implemented this solution, reducing formwork displacement by 90%.
4. High-Temperature Regions/Steam Curing Environments: High-Temperature-Resistant Neodymium Cores (150°C Operating Temperature) + Stainless Steel Sealed Housing – Prevents formwork drift caused by magnetic attenuation.
Golden Rules for Maintenance and Safety
Three Steps to Extend Lifespan:
1. Daily Care: Use a stainless steel scraper to remove debris from the magnet surface—avoid using iron tools, as they are attracted to the magnet. For hardened concrete or stubborn residue, use a polisher equipped with a wire polishing disc to restore smoothness and complete contact.
2. Storage Tips: After use, magnets should be cleaned and stored on a non-ferrous (stainless steel) cart to prevent sticking. Avoid storing magnets on iron surfaces, as this can make removal difficult and cause accidental damage.
3. Regular Inspection: Test monthly with a portable magnetometer. Replace immediately if attenuation exceeds 15%.
Safety Guidelines:
- People wearing pacemakers must stay at least 3 meters away.
- Overloading is strictly prohibited. Additional reinforcement is required under vibrating conditions.
- When removing formwork, remove the magnets before prying the formwork to avoid impact damage to the magnetic core.
Selecting precast concrete magnets isn't a simple matter of picking the strongest magnet; it's a systematic process that requires comprehensive consideration of project characteristics, load requirements, environmental factors, and team collaboration. Accurate selection can increase construction efficiency by 50% while minimizing formwork positioning errors to millimeter levels.
