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Help CenterSteel Pipe & Tube & Hot-Dip Galvanized Steel Pipe,Q195、Q215、Q235B、Q345B、20#
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Hot-dip galvanized steel pipe is the most widely used anti-corrosion pipe in current engineering fields. Relying on the anti-corrosion protection characteristics of the surface zinc layer, galvanized steel pipes solve the pain points of ordinary steel pipes such as easy rust, corrosion and short service life. Compared with traditional cold-dip galvanized steel pipes, hot-dip galvanized steel pipe have significantly improved anti-corrosion performance and structural stability. Fire-fighting galvanized steel pipe are special core pipes for fire-fighting engineering, while galvanized seamless steel pipe are suitable for high-pressure and high-standard special working conditions. This article comprehensively details the technology, materials, specifications, performance, delivery and application details of hot-dip galvanized steel pipe, fire-fighting galvanized steel pipe and galvanized seamless steel pipe, providing a complete reference for procurement, construction and bidding.
1. Product Core Definition and Classification
Galvanized steel pipes are divided into hot-dip galvanized steel pipe and electro-galvanized (cold-dip) steel pipes. Hot-dip galvanized steel pipe are preferred in compliant engineering scenarios, and cold-dip galvanized steel pipes are strictly prohibited for pressure-bearing, outdoor and buried working conditions. Hot-dip galvanized steel pipe realize metallurgical combination of zinc layer and steel pipe substrate through high-temperature zinc dipping process, with firm and fully covered internal and external coatings. Fire-fighting galvanized steel pipe are specialhot-dip galvanized steel pipe that meet national fire protection standards, suitable for fire water supply, sprinkler and fire hydrant systems. Galvanized seamless steel pipe take seamless steel pipes as the substrate for galvanizing, with no welds and stronger pressure resistance, applicable to high-pressure fluid transmission scenarios.
With excellent anti-corrosion performance, hot-dip galvanized steel pipe have become mainstream pipes in municipal, construction, agricultural and industrial fields. Fire-fighting galvanized steel pipe strictly comply with fire engineering acceptance standards and are indispensable pipes for fire protection systems. Galvanized seamless steel pipe make up for the insufficient adaptability of ordinary welded galvanized steel pipes in high-pressure working conditions.
2. Production Process
2.1 Hot-Dip Galvanized Steel Pipe (Main Engineering Grade)
Process flow: Steel pipe degreasing → pickling and oxide removal → activator treatment → hot-dipping in molten zinc at 440-480℃ → formation of zinc-iron alloy layer and pure zinc layer → water cooling and passivation → finishing and quality inspection → finished product warehousing. Hot-dip galvanized steel pipe undergo full high-temperature zinc dipping, with uniform zinc layers attached to the internal and external pipe walls. The zinc layer is metallurgically integrated with the steel substrate, featuring strong adhesion and resistance to peeling and falling off, which is the core reason for the excellent corrosion and wear resistance of hot-dip galvanized steel pipe. Standard hot-dip galvanized steel pipe reach the standard in zinc layer thickness, resisting outdoor sun and rain erosion and buried humid corrosion, with a service life far longer than ordinary pipes.
2.2 Fire-Fighting Galvanized Steel Pipe (Special Fire Grade)
Fire-fighting galvanized steel pipe adopt national standard customized hot-dip galvanizing technology. On the basis of ordinary hot-dip galvanized steel pipe technology, an additional passivation and sealing treatment is added to prevent zinc layer peeling, cracking and rusting. The pipe wall is smooth and burr-free, effectively avoiding blockage and leakage of fire-fighting pipes. The uniformity, thickness and adhesion of the zinc layer of fire-fighting galvanized steel pipe are higher than those of ordinary hot-dip galvanized steel pipe, fully meeting fire engineering acceptance specifications. They are suitable for long-term water supply and pressure-bearing fire working conditions and serve as special pipes for fire sprinkler and fire hydrant pipe networks.
2.3 Galvanized Seamless Steel Pipe (High-Pressure Special Grade)
Galvanized seamless steel pipe are made of high-quality seamless carbon steel pipes as the substrate, which are finely pretreated and then subjected to high-temperature hot-dip galvanizing. With no welding gaps and compact overall pipe structure, galvanized seamless steel pipe have excellent pressure resistance. They retain the high-strength characteristics of seamless steel pipes and possess the anti-corrosion advantages of hot-dip galvanized steel pipe, combining high strength and high corrosion resistance to adapt to special industrial scenarios of high pressure, high temperature and high corrosion.
2.4 Cold-Dip (Electro-Galvanized) Steel Pipe (Obsolete Grade)
Adopting normal-temperature electroplating process, the zinc layer is only physically adsorbed on the pipe surface with an extremely thin coating and almost no inner wall coating, leading to easy rusting and peeling. At present, such pipes are prohibited by national specifications for pressure-bearing projects such as water supply and drainage, fire protection and gas transmission. They are only used for simple indoor dry support components and cannot replace hot-dip galvanized steel pipe, fire-fighting galvanized steel pipe and galvanized seamless steel pipe.
3. Material Models (Full Specification Details)
Hot-dip galvanized steel pipe, fire-fighting galvanized steel pipe and galvanized seamless steel pipe all adopt high-quality low-carbon carbon steel substrates with stable material quality, good toughness and easy processability, suitable for construction processes such as cutting, threading, grooving and welding. The specific material models are as follows:
Q195 Material: Good toughness and high cost performance, mostly used for light-duty hot-dip galvanized steel pipe, greenhouse frames, simple supports and low-pressure ventilation pipes. It is a common material for civilhot-dip galvanized steel pipe with large output and sufficient stock.
Q215 Material: Balanced strength and toughness, suitable for small and medium-sized hot-dip galvanized steel pipe, widely used in ordinary water supply and drainage, garden guardrails and light steel structures, meeting the needs of most conventional civil engineering hot-dip galvanized steel pipe.
Q235B Material (Mainstream Standard): National standard core material with high strength, good stability and strong impact resistance. More than 90% of engineering hot-dip galvanized steel pipe and fire-fighting galvanized steel pipe adopt this material. It is applicable to pressure-bearing pipes for fire protection, municipal and construction projects, serving as the special standard material for fire-fighting galvanized steel pipe with strong universality.
Q345B Material (High-Strength Grade): Higher yield strength and stronger compression and load-bearing capacity, mostly used for large-diameter thick-walled hot-dip galvanized steel pipe, heavy steel structures, bridge supports and high-pressure fluid pipes, adapting to heavy-load and harsh outdoor working conditions.
20# Seamless Steel Material: Special substrate for galvanized seamless steel pipe, featuring compact texture, no impurities and excellent pressure resistance. It is suitable for high-pressure industrial fluid transmission and high-end fire-fighting high-pressure pipe networks, and is the core material of high-quality galvanized seamless steel pipe.
Foreign Trade Materials: Hot-dip galvanized steel pipe and galvanized seamless steel pipe conforming to international standards such as ASTM A53, SS400 and A36 can be produced to meet the procurement needs of overseas projects.
4. Dimension Specifications (Full National Standard Series)
Hot-dip galvanized steel pipe, fire-fighting galvanized steel pipe andgalvanized seamless steel pipe are all produced in strict accordance with national standards GB/T 3091-2024 and GB/T 13793-2025, covering full specifications of round pipes and square and rectangular pipes with customizable fixed lengths. The conventional specifications are detailed as follows:
4.1 Hot-Dip Galvanized Round Pipe / Fire-Fighting Galvanized Round Pipe (Fluid Transmission)
This series of specifications is the mainstream size for fire-fighting galvanized steel pipe and water supply and drainage hot-dip galvanized steel pipe, suitable for most low-pressure fluid transmission projects:
DN15 (1/4"): Outer diameter 21.3mm, wall thickness 2.5-2.8mm
DN20 (3/8"): Outer diameter 26.9mm, wall thickness 2.5-2.8mm
DN25 (1"): Outer diameter 33.7mm, wall thickness 3.2-3.5mm
DN32 (1.2"): Outer diameter 42.4mm, wall thickness 3.2-3.5mm
DN40 (1.5"): Outer diameter 48.3mm, wall thickness 3.5-4.0mm
DN50 (2"): Outer diameter 60.3mm, wall thickness 3.5-3.8mm
DN65 (2.5"): Outer diameter 76.1mm, wall thickness 3.8-4.0mm
DN80 (3"): Outer diameter 88.9mm, wall thickness 4.0-4.5mm
DN100 (4"): Outer diameter 114.3mm, wall thickness 4.0-4.5mm
DN125 (5"): Outer diameter 139.7mm, wall thickness 4.5-5.0mm
DN150 (6"): Outer diameter 168.3mm, wall thickness 4.5-5.5mm
DN200 (8"): Outer diameter 219.1mm, wall thickness 5.0-6.0mm
DN250-DN300 Large Diameter: Outer diameter 273mm-323.9mm, wall thickness 6.0-10.0mm
Fixed length: conventional 6m, 12m, customizable from 3m to 12m; Zinc layer standard: ordinaryhot-dip galvanized steel pipe ≥275g/㎡, fire-fighting galvanized steel pipe ≥350g/㎡, high anti-corrosion customized models up to 600g/㎡.
4.2 Galvanized Seamless Steel Pipe Specifications (High-Pressure Use)
Galvanized seamless steel pipe have no welds and high pressure resistance, with specifications covering DN20-DN300 and wall thickness of 3.0-12mm. Customizable SCH40 and SCH80 thickened high-pressure models are available, suitable for industrial high-pressure fluid transmission and high-end fire-fighting pressure stabilizing pipe networks, making up for the high-pressure bearing deficiency of ordinary hot-dip galvanized steel pipe.
4.3 Galvanized Square & Rectangular Pipe (Structural Use)
Specifications: 20×20mm-200×200mm square and rectangular pipes, wall thickness 1.2-12mm, fixed length 6m/12m. Mostly used for steel structure supports, greenhouse frames and curtain wall keels, all produced by hot-dip galvanizing process with the same anti-corrosion performance as hot-dip galvanized steel pipe.
5. Implementation Standards
Domestic Standards: GB/T 3091-2024 《Welded Steel Pipes for Low-Pressure Fluid Delivery》, GB/T 13793-2025 《Straight Seam Electric Welded Steel Pipes》, GB 50981 《Code for Construction Quality Acceptance of Building Mechanical and Electrical Engineering》 (special acceptance standard for fire-fighting galvanized steel pipe); International Standards: ASTM A53, BS EN10255, JIS G3444, API 5L, ensuring the qualified quality of hot-dip galvanized steel pipe, fire-fighting galvanized steel pipe and galvanized seamless steel pipe.
6. Delivery Cycle (Accurate Delivery)
To ensure project construction progress, we have formulated a hierarchical delivery mechanism for hot-dip galvanized steel pipe, fire-fighting galvanized steel pipe and galvanized seamless steel pipe with sufficient spot inventory and priority production for urgent orders:
Conventional Spot Specifications: DN15-DN200 standard wall thickness hot-dip galvanized steel pipe and fire-fighting galvanized steel pipe are in sufficient stock, delivered within 3-5 working days after payment, with loading available on the day of ordering for rapid delivery.
Large-Diameter / Thickened Specifications: Large-diameter pipes above DN200, thick-walledhot-dip galvanized steel pipe and conventional galvanized seamless steel pipe are in sufficient stock, delivered within 5-7 working days after payment.
Customized Products: Custom hot-dip galvanized steel pipe and galvanized seamless steel pipe with special lengths, high zinc layers, non-standard wall thicknesses and foreign trade specifications are delivered within 7-15 working days after production scheduling.
Large-Batch Orders: Bulk purchases of tonnage level can be arranged for priority production by the production line with negotiable urgent delivery to ensure project schedule; full-truck delivery avoids transshipment and reduces pipe collision loss.
Logistics Distribution: Multiple national warehouses for nearby delivery, covering all provinces and cities nationwide, supporting full-truck, less-than-truckload and special logistics lines with fast arrival. Hot-dip galvanized steel pipe and fire-fighting galvanized steel pipe are fully coated and protected during transportation to avoid zinc layer falling off and wear.
7. Core Product Advantages
1. Superior Anti-Corrosion and Durability: The metallurgically bonded zinc layer of hot-dip galvanized steel pipe isolates air and moisture, with a service life of 15-25 years in outdoor and buried working conditions. Fire-fighting galvanized steel pipe undergo enhanced anti-corrosion treatment, no rust or scaling during long-term water supply. Galvanized seamless steel pipe adopt double protection with strong stability in high-pressure and corrosive environments.
2. Excellent Mechanical Properties: Hot-dip galvanized steel pipe have high strength, compression and bending resistance and are not easy to deform. Fire-fighting galvanized steel pipe have stable pressure bearing capacity, meeting the constant pressure water supply demand of fire pipe networks.Galvanized seamless steel pipe have no weld defects, with far stronger high-pressure resistance and impact resistance than ordinary pipes.
3. Efficient and Convenient Construction: All hot-dip galvanized steel pipe, fire-fighting galvanized steel pipe and galvanized seamless steel pipe support cutting, threading, grooving, welding and flange connection with complete matching pipe fittings, adapting to various construction processes and greatly shortening the construction cycle.
4. Stable and Compliant Quality: Each batch of hot-dip galvanized steel pipe, fire-fighting galvanized steel pipe and galvanized seamless steel pipe is equipped with material certificates and test reports, fully complying with national standards and passing engineering and fire acceptance, with higher cost performance than similar anti-corrosion pipes.
8. Application Fields
1. Fire-Fighting Engineering: Fire-fighting galvanized steel pipe are specially used for fire hydrant pipe networks, sprinkler systems and main fire water supply pipes, serving as the core materials for fire-fighting projects. Compliant fire-fighting galvanized steel pipe are preferred for all fire pipe projects.
2. Municipal Engineering: Hot-dip galvanized steel pipe are used for municipal water supply and drainage, low-pressure gas transmission, road guardrails and street lamp brackets, with excellent outdoor durability to meet long-term service requirements of municipal projects.
3. Construction Engineering: Hot-dip galvanized steel pipe are applied to building water supply and drainage, ventilation pipes, curtain wall keels and indoor and outdoor steel structure supports.
4. Agricultural Facilities: Hot-dip galvanized steel pipe are used for greenhouse frames and farmland irrigation pipes, featuring corrosion resistance, wind and rain resistance and long service life.
5. Industrial Working Conditions: Galvanized seamless steel pipe are used for factory high-pressure fluid transmission, equipment pipes and chemical low-pressure anti-corrosion pipe networks; hot-dip galvanized steel pipe are used for factory ventilation and compressed air transmission.
6. Power and Communication: Hot-dip galvanized steel pipe serve as cable protection casings, power supports and auxiliary components of communication equipment.
9. Operation Notes
1. Cutting and welding of hot-dip galvanized steel pipe and fire-fighting galvanized steel pipe will damage the local zinc layer. It is necessary to timely paint zinc-rich paint for repair to avoid rust and corrosion at damaged positions and extend the service life of pipes.
2. Ordinary hot-dip galvanized steel pipe are not recommended for direct drinking water pipelines; food-grade anti-corrosion treated pipes are optional. Fire-fighting galvanized steel pipe are only used for fire water supply and not applicable to direct drinking water transmission.
3. Regular hot-dip galvanized steel pipe or customized high anti-corrosion hot-dip galvanized steel pipe must be used for buried and outdoor projects. Cold-dip galvanized steel pipes are strictly prohibited to avoid later rusting and rework.
4. Galvanized seamless steel pipe must be adopted for high-pressure working conditions. Ordinary welded hot-dip galvanized steel pipe and fire-fighting galvanized steel pipe cannot be used as substitutes to prevent pipe pressure damage.
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