Curing Agent for One Component Polyurethane System
Curing agent for one component polyurethane system is aliphatic polyisocyanate based on hexomthylene diisocyanate.
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In recent years, with the advancement of steel structure application technology in China, economical profiles such as cold-formed thin-walled steel have experienced rapid development. Compared to traditional rolled sections, cold-formed thin-walled steel offers a more efficient material distribution, a larger radius of gyration, and superior resistance to bending and torsion. Unlike hot-rolled steel, which increases bearing capacity by adding more material, cold-formed steel enhances performance while saving steel through optimized cross-sectional design.
One of the key advantages of cold-formed steel is its economic section characteristics. In the context of transmission towers, the web often operates under conditions of instability due to high slenderness ratios. Traditional angle sections lack significant advantages in this regard, and their available specifications are limited. Cold-formed steel allows for the selection of appropriate cross-sections based on the structural forces, making full use of its section properties to achieve greater efficiency and cost-effectiveness.
Another benefit is the flexibility in product specifications. A conventional 10-ton transmission tower may require up to 25 different types of angle steel, leading to challenges in procurement and processing. This often results in substitution of materials, causing waste—up to 10% in some cases. In contrast, cold-formed steel can be produced in various sizes using simple rolling equipment, offering greater flexibility in quantity and specifications, ensuring a steady supply of tower materials.
The variable dimensions of components in a 10-ton tower also present challenges when using hot-rolled steel, which is typically manufactured in fixed lengths. This often leads to material waste, with up to 5% loss due to length mismatches. Cold-formed steel, however, can be customized to meet specific user needs, resulting in a high finished product rate (up to 99%) and minimal leftover material, significantly reducing waste during the manufacturing process.
Additionally, the diverse cross-sectional shapes of cold-formed steel provide greater design flexibility. It overcomes the limitation of angle steel, which restricts tower designs to square or rectangular shapes, often leading to non-coplanar joints. This allows engineers to create more efficient and innovative tower structures. For instance, a three-column tower can lead to optimized web systems, improving overall structural performance and reducing weight and component count.
High-strength cold-formed steel also offers advantages in terms of material properties. It avoids the limitations of hot-rolled steel in terms of supply volume and production complexity, especially when high-strength materials are required.
Regarding corrosion resistance, transmission towers are typically protected by hot-dip galvanizing. However, cold-formed steel's complex cross-sections and thin profiles make it unsuitable for this process. Fortunately, new anti-corrosion technologies, such as weather-resistant materials and advanced plating methods, now offer effective solutions for protecting cold-formed steel.
The production of high-strength weathering steel has matured and is widely used in railway systems. Applying this material to transmission towers not only reduces tower consumption and processing costs but also minimizes environmental impact. Although the initial investment may be slightly higher, the long-term economic and environmental benefits are substantial, with a potential cost reduction of about 20% per ton.
Research into the feasibility of using cold-formed steel for transmission towers began in the late 1980s. However, due to high costs and technical limitations at the time, and because early towers were small in scale, hot-rolled steel remained sufficient. As a result, the project was not approved. Recently, with the advancement of steel structure technology, the use of cold-formed steel has grown rapidly. Its cost is decreasing, and its structural advantages are becoming more evident, opening new possibilities for its application in transmission towers.
Using cold-formed thin-walled steel helps save resources and energy. Promoting high-strength weather-resistant cold-formed steel on transmission towers not only reduces material usage and processing costs but also avoids environmental pollution. It is an initiative with significant economic and environmental value, making it essential to conduct further research and application of high-strength weather-resistant cold-formed steel in transmission towers.