أنواع الفولاذ المجلفن: شرح الاختلافات والاستخدامات

Galvanized steel comes in various types, developed to meet diverse applications, performance demands, and production constraints. These include hot-dip, electro-galvanized, Galvannealing, sherardized, and continuously galvanized steel.

This article will explore the types of galvanized steel, their characteristics, and uses across different industries. We will also provide an overview of cold galvanized steel.

What Is Galvanized Steel?

Galvanized steel is coated with a zinc layer to prevent corrosion and enhance longevity. It is defined by standards like ASTM A653, EN 10346, and JIS G3302, which specify coating thickness and mechanical properties. Common grades, including DX51D+Z and SGCC, are used in construction, automotive, home appliances, and agriculture, where durability and rust resistance are key.

Overview of Different Types of Galvanized Steel

The table below offers a concise comparison of various galvanized steel types. Generally, thicker coatings provide stronger protection against corrosion. Use this guide to efficiently compare options and choose the most suitable steel for your requirements.

الفولاذ المجلفن بالغمس الساخن

Hot-dip galvanized steel is carbon steel coated with zinc through immersion in molten zinc, forming a durable and corrosion-resistant layer. The surface provides a distinctive spangled or matte finish. This type of steel adheres to international standards such as ASTM A123, EN ISO 1461، و JIS H8641, with popular grades like S235JR+Z و دي اكس 51 دي + زد.

In the past, lead was added to hot-dip galvanized steel to improve zinc fluidity and coating uniformity. Due to health and environmental concerns, lead has been eliminated, with modern processes now adhering to stricter safety and sustainability standards.

Process of Hot-Dip Galvanized Steel

The process starts with cleaning the steel through degreasing, pickling, and fluxing to remove contaminants. The steel is then dipped in molten zinc at around 450°C (842°F), forming a metallurgical bond and multiple protective layers, including a zinc-iron alloy and a pure zinc coating.

Characteristics of Hot-Dip Galvanized Steel

• مقاومة التآكل: Offers exceptional protection in outdoor and harsh environments due to its thick zinc coating.
• متانة: The metallurgical bond between zinc and steel enhances the coating’s longevity and wear resistance.
• طلاء موحد: Ensures full coverage, including corners and edges, minimizing weak points.
• الشفاء الذاتي: Zinc acts as a sacrificial anode, protecting exposed steel in case of minor damage.
• صيانة منخفضة: Requires little upkeep, reducing long-term maintenance costs.

Applications of Hot-Dip Galvanized Steel

• بناء: Used in bridges, guardrails, roofing, and structural beams due to its strength and corrosion resistance.
• السيارات: Commonly applied in chassis parts, underbody components, and other exposed areas.
• البنية التحتية للطاقة: Utilized in transmission towers, wind turbines, and solar panel supports for long-term outdoor use.
• زراعة: Ideal for fencing, silos, and irrigation equipment exposed to soil and weather.
• بحري: Employed in docks, piers, and offshore platforms due to its resistance to saltwater corrosion.

Limitations of Hot-Dip Galvanized Steel

Hot-dip galvanized steel’s thick coating is unsuitable for precision parts or smooth finishes. High temperatures can warp thin structures, and internal surfaces of hollow sections may be unevenly coated. It is less durable in abrasive or acidic environments and may be costly for small or specialized uses.

Electro-galvanized Steel

Electro-galvanized steel is steel coated with zinc through an electroplating process, resulting in a thin, smooth, and uniform layer of zinc. It adheres to international standards such as ASTM A879, EN 10152، و JIS G3313, with common grades including مركز التعليم والتعلم و DX54D+ZE.

Process of Electro-galvanized Steel

Electro-galvanizing involves immersing steel in a zinc electrolyte solution and applying an electric current to deposit a thin, even zinc coating. This process ensures a smooth finish, corrosion resistance, and precise control of coating thickness.

Characteristics of Electro-galvanized Steel

• Smooth Surface: Delivers a uniform finish ideal for painting and aesthetic applications.
• Thin Coating: Provides precise control over thickness for cost efficiency and reduced weight.
• مقاومة معتدلة للتآكل: Suitable for indoor or low-corrosion environments.
• Good Workability: Offers excellent formability for stamping and shaping processes.
• تحسين قابلية اللحام: Thin coatings minimize challenges during welding.

Applications of Electro-galvanized Steel

• السيارات: Commonly used for car body panels, interiors, and components requiring a smooth, paintable surface.
• الأجهزة المنزلية: Ideal for refrigerators, washing machines, and other products demanding a clean and durable finish.
• الالكترونيات: Used in enclosures and casings for devices, where precision and appearance are key.
• أثاث: Applied in office furniture and storage systems for its aesthetic appeal and corrosion resistance.

Limitations of Electro-galvanized Steel

Electro-galvanized steel’s thin zinc coating offers limited corrosion and abrasion resistance, making it unsuitable for harsh outdoor conditions. It is also less cost-effective for applications requiring thicker coatings, restricting its use to controlled environments where appearance and precision are priorities.

الفولاذ المجلفن

Galvannealed steel is hot-dip galvanized steel that undergoes an additional annealing process to create a zinc-iron alloy coating. It meets international standards such as معايير ASTM A653, EN 10346، و JIS G3317, with common grades including A40, A60، و DX56D+ZF.

Process of Galvannealed Steel

Galvannealed steel is made by hot-dip galvanizing steel and then heating it to 500–600°C in an annealing furnace. This process creates a zinc-iron alloy layer with a durable, matte finish that is weldable and paintable.

Characteristics of Galvannealed Steel

• لمسة نهائية غير لامعة: Provides an ideal surface for painting without additional preparation.
• Improved Adhesion: The alloy coating strongly bonds to the steel, ensuring long-term durability.
• مقاومة معتدلة للتآكل: Slightly less resistant than pure zinc coatings but suitable for many environments.
• صلابة عالية: The zinc-iron alloy is harder than pure zinc, offering better abrasion resistance.

Applications of Galvannealed Steel

• صناعة السيارات: Used in body panels, frames, and structural parts requiring weldability and paintability.
• الأجهزة: Ideal for washing machines, dryers, and other white goods where a smooth, paintable surface is needed.
• بناء: Used in ceilings, panels, and partition walls for its durability and ease of coating.
• العلب الكهربائية: Preferred for electrical boxes and cabinets requiring strong adhesion for paint and corrosion protection.
• أثاث: Applied in office furniture and shelving for its combination of strength and aesthetic qualities.

Limitations of Galvannealed Steel

Galvannealed steel has lower corrosion resistance than pure zinc coatings, is prone to cracking during deep drawing, and lacks the bright finish of other galvanized options.

Continuously Galvanized Steel

Continuously galvanized steel is steel coated with zinc in a continuous production process, ensuring uniform thickness and quality. It adheres to international standards such as معايير ASTM A653, EN 10346، و جي اي اس جي 3302, with popular grades like دي اكس 51 دي + زد و جي90.

Process of Continuously Galvanized Steel

Steel strips are continuously fed through a molten zinc bath, creating a thin, even coating. Air knives control thickness and the coating is rapidly cooled to solidify, ensuring uniform quality and high production efficiency.

Characteristics of Continuously Galvanized Steel

• مقاومة التآكل: Offers effective protection in various environments, particularly in mild to moderate conditions.
• High Efficiency: The continuous process supports large-scale production with minimal waste.
• تشطيب السطح: Smooth and clean, ideal for further processing like painting or forming.
• فعالة من حيث التكلفة: Efficient production lowers costs while maintaining high quality.

Applications of Continuously Galvanized Steel

• السيارات: Widely used for body panels, roofs, and structural components requiring lightweight and corrosion resistance.
• بناء: Ideal for roofing sheets, wall cladding, and steel framing in residential and commercial buildings.
• الأجهزة: Used in washing machines, air conditioners, and kitchen equipment for its clean surface and durability.
• Electrical Industry: Suitable for cable trays, enclosures, and other components exposed to low-corrosion environments.

Limitations of Continuously Galvanized Steel

Continuously galvanized steel has a thin zinc coating, offering moderate corrosion resistance, unsuitable for harsh environments. The smooth surface may also reduce paint adhesion, and the thin coating is less durable in extreme conditions, requiring more maintenance.

Sherardized Steel

Sherardized steel is a type of galvanized steel coated with zinc through a dry diffusion process, creating a uniform zinc-iron alloy layer. It complies with standards like ISO 17668 and is commonly used for small components like fasteners and fittings.

Process of Sherardized Steel

Sherardizing involves heating steel parts in a sealed drum with zinc powder at 300–450°C (572–842°F). Zinc vaporizes and diffuses into the steel surface, forming a durable zinc-iron alloy. This method ensures even coverage, ideal for small, complex parts.

Characteristics of Sherardized Steel

• Uniform Coating: Provides consistent coverage, even on irregular shapes and small components.
• مقاومة عالية للتآكل: Particularly effective in harsh environments, including marine and industrial settings.
• مقاومة التآكل: The alloy coating is harder and more wear-resistant than pure zinc.
• Eco-Friendly Process: The dry method produces no liquid waste, making it environmentally friendly.

Applications of Sherardized Steel

• Fasteners and Bolts: Used for screws, nuts, and other hardware exposed to moisture or corrosive environments.
• تجهيزات الأنابيب: Preferred for threaded components in plumbing and industrial pipelines.
• الأدوات الزراعية: Applied to small equipment parts requiring durability and weather resistance.
• المكونات الكهربائية: Used in connectors and other small fittings needing precision and protection.

Limitations of Sherardized Steel

Sherardized steel is suited for small parts due to process size limits, with thinner coatings less effective in harsh environments. It is slower and costlier than other methods, with a matte finish that may not suit all aesthetic needs.

What Is Cold Galvanizing?

Cold galvanizing, also called zinc-rich coating, involves applying zinc-rich paint to steel surfaces to protect against corrosion. Unlike true galvanizing, it lacks a metallurgical bond and is not classified as genuine galvanized steel. Techniques such as mechanical plating, spray galvanizing, and zinc-rich painting create a surface barrier for protection.

This method is affordable and simple to apply but offers only moderate corrosion resistance compared to traditional galvanizing. It is commonly used for repairing galvanized surfaces, providing short-term protection, or maintaining steel in environments with minimal corrosion risks.

Various Types of Galvanized Steel Suppliers

Steel Pro Group offers a diverse selection of galvanized steel products, like q235 Galvanized steel coil و s235 Galvanized steel sheet. We are equipped to handle all your galvanized steel project needs with exceptional quality and reliability.

Committed to excellence, Steel Pro Group ensures each product meets strict standards, providing durable and high-performance solutions for construction, automotive, appliances, and more.