KN-BLOCK, a protective steel plate for underground installations registered with NETIS, protects with the ductility of ultra-soft iron.
The underground protective steel plate "KN-BLOCK" is a protective board designed to safeguard buried utilities from pavement cutter blades in various infrastructure projects, including electrical duct construction, telephone lines, and water pipes. It uses ultra-soft steel as its material, achieving a unique structure that absorbs blade impacts with excellent toughness. Despite a thickness of 12mm, it provides protective performance equivalent to that of a typical 16mm thick SS400 protective board. The reduction in thickness results in a lightweight design, improving transportation and construction efficiency, while also contributing to reduced work burden and environmental impact. This product is registered with NETIS and is recognized as a new technology eligible for evaluation in public works. Kumagai Special Steel has established a consistent production system at its own factory as the manufacturer of KN-BLOCK. It ensures thorough quality control and stable supply. As of July 2025, it has a delivery record to 123 projects across 28 prefectures nationwide and supports nationwide shipping. It safely and reliably supports the electrification of utility poles and the development of road infrastructure.
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basic information
KN-BLOCK is a protective steel plate made of ultra-soft iron with a thickness of 12mm for underground installations. Compared to the typical 16mm thick protective plates made of SS400, it achieves weight reduction while ensuring equivalent protective performance. The weight is approximately 103kg per square meter, which is about 25% lower than SS400 (approximately 134.4kg per square meter). In load tests assuming a T-25 impact coefficient of 0.4 and a soil cover of 10cm, the residual deflection at a maximum load of 29.4kN was confirmed to be less than 0.03mm, demonstrating excellent recovery. Additionally, in a soil corrosion test equivalent to 14 years of exposure, the material showed a thickness reduction of 0.62mm, which is equal to or better than that of SS400 equivalent materials (0.70mm) in terms of corrosion resistance. The standard dimensions are W500×L550×t12mm (26kg per sheet), with custom sizes available up to a maximum of 1,500×3,000mm. With a welding specification for end-offset prevention angles, it balances workability and safety, making it a high-performance protective plate suitable for public works.
Price range
Delivery Time
※The price varies depending on the quantity and the size (width x length) due to yield factors, so please contact us first.
Applications/Examples of results
KN-BLOCK is widely adopted across the country for underground installation protection purposes, focusing on joint trench construction for electric wires, telephone lines, and water pipes. By July 2025, it has a track record of delivery to 123 projects in 28 prefectures nationwide, being utilized in public infrastructure projects such as urban pole removal initiatives and major road renovation works. It has received high evaluations as a NETIS registered product, gaining support from both clients and construction companies in terms of safety, workability, and cost-effectiveness. Despite a thickness of 12mm, it ensures protective performance equivalent to 16mm SS400, achieving improved transportation efficiency and reduced workload through weight reduction. Additionally, the consistent production system at its own factory enables stable supply and quick response to short delivery times, allowing for flexible adaptation to sudden changes in project schedules. Moving forward, it will continue to expand its nationwide deployment as a protective board that meets the demands for pole removal promotion and infrastructure renewal.
Detailed information
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Easy installation With a free design, it is easy to install on-site by simply arranging the pieces. Available in dimensions up to 1,500mm x 3,000mm, it can accommodate curved shapes as well. Gentle curves can be easily installed on-site without any processing, just by arranging the pieces.
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Furthermore, since we also offer custom processing, we can accommodate free design according to construction conditions such as burial extension, width, and angle.
Line up（1）
| Model number | overview |
|---|---|
| KN-BLOCK standard dimensions: thickness 12mm x 500mm x 550mm | A protective plate with a unique structure that uses soft iron material and stops the cutter blade with resilience. |
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Company information
Since our establishment in 1913, we have been a specialized trading company of special steel for nearly a century, listening to the needs of many customers and building an ideal relationship between customers and steel manufacturers as a conductor of steel distribution. As a trading company with various processing equipment, including cutting machines and laser cutting machines, we also contribute to reducing our customers' capital investment. Please feel free to contact us if you have any requests.
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