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Steel Pipe Knowledge

Steel Pipe Knowledge

What should be considered when selecting steel for spiral pipe production?

2021/02/10

What should be considered when selecting steel for spiral pipe production?

What should spiral pipe manufacturers pay attention to when selecting steel during production? Our staff at the spiral pipe manufacturer is here to walk you through it.

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Protection of Anti-Corrosion Spiral Steel Pipes During Construction

2021/02/08

Protection of Anti-Corrosion Spiral Steel Pipes During Construction

Anti-corrosion spiral steel pipes require careful handling not only during manufacturing but also during storage. This approach not only extends the service life of the pipes but also ensures that, even after long-term storage, they remain in as good condition as when they left the factory, making them easier to sell.

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What is the significance of pickling large-diameter steel pipes?

2021/01/16

What is the significance of pickling large-diameter steel pipes?

Pickling of large-diameter steel pipes is a process that uses acidic solutions to remove scale and rust from the steel surface. Common pickling acids include sulfuric acid, hydrochloric acid, phosphoric acid, and mixed acids. The primary purpose of pickling is to eliminate surface oxide scales, followed by lubrication—carbon steels are treated with phosphating soap, stainless steels with oil‑lime, and copper or aluminum tubes with oil coating. Subsequently, the traditional copper‑plating process is applied, after which the material undergoes further deep‑drawing operations.

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Corrosion Mechanism of Steel Plate Coiled Pipes

2021/01/11

Corrosion Mechanism of Steel Plate Coiled Pipes

Corrosion that occurs on the surface of steel pipe coils exposed to the atmosphere is referred to as atmospheric corrosion. This phenomenon arises because the atmosphere contains water vapor, which condenses on the pipe surface to form a thin water film. The water film dissolves oxygen and other impurities from the air, leading to electrochemical corrosion. Since the water film is extremely thin and offers low resistance, and oxygen from the air is continuously supplied, the cathodic process is primarily driven by the depolarization of oxygen. The corrosion of steel pipelines in the atmosphere is influenced by factors such as atmospheric conditions, metal composition, surface morphology, orientation, droplet runoff, and operating conditions.

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Production process of welded steel pipes

2020/03/25

Production process of welded steel pipes

The development of steel pipe manufacturing technology began with the rise of the bicycle industry, the early‑19th‑century oil boom, shipbuilding, boiler and aircraft production during the two world wars, and, after World War II, the manufacture of thermal power plant boilers. Additionally, advances in the chemical industry, as well as the drilling, extraction, and transportation of oil and natural gas, have all strongly propelled the steel pipe industry forward in terms of product variety, output, and quality. Steel pipes are typically classified into two main types based on their manufacturing process: seamless steel pipes and welded steel pipes. This discussion will focus primarily on welded steel pipes. Welded steel pipes, also known as seam‑welded pipes, are produced by bending and rolling tube blanks—made from steel plates or strips—into the desired cross‑sectional shape and dimensions using various forming methods, followed by welding along the seam to create the finished pipe. Compared with seamless steel pipes, welded pipes offer higher dimensional accuracy, especially in wall thickness; simpler primary equipment; a smaller footprint; the ability to operate continuously; greater production flexibility; and a broader range of products that can be manufactured on a single production line. I. The general production process for spiral welded steel pipes is as follows: 1. Raw materials include steel strip coils, welding wire, and flux. 2. Prior to forming, the steel strip undergoes leveling, edge trimming, edge planing, surface cleaning, conveying, and pre‑bending operations. 3. A weld gap control device is used to ensure that the weld gap meets welding requirements, with strict control over pipe diameter, misalignment, and weld gap dimensions. 4. After cutting into individual pipe lengths, the first three pipes of each batch undergo rigorous initial inspection, assessing weld mechanical properties, chemical composition, fusion quality, and surface finish. Nondestructive testing is also performed to confirm compliance with manufacturing standards before the pipes are officially put into production. II. Longitudinal Submerged Arc Welded Pipes (LSAW): Longitudinal submerged arc welded pipes are generally manufactured from steel plates. Through various forming processes, including double‑sided submerged arc welding and post‑weld expanding, these pipes are produced. Key equipment includes edge milling machines, pre‑bending machines, forming machines, pre‑welding units, and expanding machines. There are several distinct forming methods for LSAW pipes, such as UOE, RBE, and JCO (JCOE). In the UOE process, the steel plate is first pressed into a U‑shape, then further formed into an O‑shape, followed by internal and external submerged arc welding. Post‑weld expansion is typically applied either at the ends or along the entire length, resulting in what is called a UOE pipe; if no expansion is performed, it is referred to as a UO pipe. For RBE pipes, the steel plate is rolled and bent into shape, then subjected to internal and external submerged arc welding, with subsequent expansion. If no expansion occurs, it is designated as an RB pipe. In the JCO process, the steel plate is sequentially formed into J‑, C‑, and O‑shapes, followed by post‑weld expansion, yielding a JCOE pipe; without expansion, it becomes a JCO pipe. UOE longitudinal submerged arc welded pipe forming process: The three primary forming steps in UOE pipe production involve pre‑bending the edges of the steel plate, forming a U‑shape, and finally forming an O‑shape. Each step employs a dedicated forming press, sequentially completing edge pre‑bending, U‑shaping, and O‑shaping to transform the steel plate into a circular tubular form. As shown in the figure: JCOE longitudinal submerged arc welded pipe forming process: During forming, the JC0 machine performs multiple incremental stamping operations—first pressing half of the steel plate into a “J” shape, then shaping the other half into a “C” shape, and finally applying pressure at the center to produce an open “0”‑shaped blank. Comparison between JCO and UO forming methods: JCO forming uses progressive pressure, transforming the pipe‑forming process from the two steps of UO formation into multiple stages. Throughout this process, the steel plate deforms uniformly, residual stresses remain minimal, and the surface remains free of scratches. The resulting pipes exhibit greater flexibility in diameter and wall‑thickness specifications, allowing for both large‑scale and small‑batch production. They can manufacture high‑strength, thick‑walled pipes of large diameters as well as small‑diameter, thick‑walled pipes. Particularly when producing high‑grade, thick‑walled pipes—especially medium and small diameters—JCO offers advantages unmatched by other processes, satisfying users’ diverse requirements for pipe specifications. Investment is relatively low, but production efficiency is comparatively modest, with annual output typically ranging from 100,000 to 250,000 tons. UO forming, which employs both U‑ and O‑shaped pressure steps, is characterized by its high capacity and substantial output, often reaching 300,000 to 1 million tons per year, making it suitable for large‑volume production of a single specification. However, the capital investment required is considerable, often beyond the reach of developing countries. III. Longitudinal Electric Resistance Welded Pipes (ERW): Longitudinal electric resistance welded pipes are produced by taking hot‑rolled coil stock, forming it through specialized machinery, and then utilizing the skin effect and proximity effect of high‑frequency currents to heat and melt the edges of the pipe blank. Under pressure from the rolling mill, the heated edges are fused together, completing the weld. Welded steel pipes, also known as weld pipes, are manufactured by rolling steel plates or strips into shape and then welding them together. Their production process is simple, highly efficient, and offers a wide variety of grades and specifications, requiring relatively little equipment. However, their overall strength is generally lower than that of seamless steel pipes. Since the 1930s, with the rapid advancement of continuous rolling technology for high‑quality steel strips and improvements in welding and inspection techniques, weld quality has steadily improved, leading to an increasing diversity of welded pipe grades and specifications. Consequently, welded pipes have increasingly replaced seamless pipes across many applications. Welded pipes are categorized according to weld type into longitudinal welded pipes and spiral welded pipes. By manufacturing method, they are further divided into arc‑welded pipes, resistance‑welded pipes, gas‑welded pipes (high‑frequency and low‑frequency), and furnace‑welded pipes. Longitudinal welded pipes feature a straightforward production process, high efficiency, low cost, and rapid development. Spiral welded pipes generally exhibit higher strength than longitudinal welded pipes, enabling the use of narrower blanks to produce larger‑diameter pipes, and even allowing the same‑width blanks to yield pipes of different diameters. Nevertheless, compared with longitudinally welded pipes of equal length, spiral welded pipes typically have weld seams that are 30%–100% longer, while their production speed tends to be slower. Product Standards: Common materials used for welded pipes include Q235A, Q235C, Q235B, 16Mn, 20#, Q345, L245, L290, X42, X46, X60, X80, 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb, among others. The raw material for welded pipes is steel plate or steel strip, which, depending on the welding process, is classified into furnace‑welded pipes, electric‑welded pipes (resistance‑welded), and automatic arc‑welded pipes. Based on the welding configuration, they are further divided into longitudinal welded pipes and spiral welded pipes. Depending on the end‑shape, they may also be categorized as round‑ended welded pipes or irregular‑shaped welded pipes (square, flat, etc.). According to material and intended application, welded pipes can be grouped into the following categories: GB/T 3091‑2001 (galvanized steel for low‑pressure fluid conveyance).

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Understanding the Function of Insulated Steel Pipes

2019/08/29

Understanding the Function of Insulated Steel Pipes

The manufacturing process of steel‑jacketed steam insulated pipes is highly advanced; employing a cast‑in‑place, monolithic forming technique, these pipes not only achieve superior structural integrity but also exhibit excellent aesthetic appeal. They can be readily adapted to a wide range of specifications and models for use in diverse environments, making them suitable for both industrial production and everyday household applications.

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Applications of 3PE Polyethylene Anti-Corrosion Insulated Pipes

2019/08/29

Applications of 3PE Polyethylene Anti-Corrosion Insulated Pipes

At present, pipeline anti-corrosion technologies have received widespread acclaim in practical market applications. These technologies are employed across a wide range of industrial sectors, including construction, petroleum, power generation, metallurgy, national defense, transportation and storage, boilers, heat exchangers, fans, and vehicles and ships. Among them, anti-corrosion and thermal‑insulation pipe technology typically involves applying an external anti-corrosion coating to the outer surface of spiral‑wound pipes to mitigate corrosion and extend service life. Currently, the primary external anti-corrosion coatings used for spiral pipes include three‑layer polyethylene (3PE), epoxy powder, and epoxy coal tar pitch; accordingly, products such as epoxy‑powder‑coated thermal‑insulation pipes and epoxy‑coal‑tar‑pitch‑coated steel pipes can be manufactured. The use of three‑layer polyethylene and epoxy powder coatings offers several advantages: excellent waterproofing and corrosion resistance, electrical insulation, and low‑temperature performance. In many European and North American countries, these coatings are the standard choice for underground pipelines. Considering factors such as overall service life and maintenance costs, China currently prioritizes the three‑layer polyethylene composite anti-corrosion coating. The specific manufacturing process for three‑layer polyethylene‑coated spiral anti‑corrosion and thermal‑insulation pipes is as follows: medium‑frequency heating of the spiral pipe, shot blasting for rust removal, quality inspection of the blast‑cleaned surface, medium‑frequency heating, application of epoxy powder, coating with an adhesive, extrusion of polyethylene, water‑cooling treatment, leak testing of the coating, and finally stacking the coated pipes.

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Introduction to Polyurethane Direct-Buried Insulated Pipes

2019/08/29

Introduction to Polyurethane Direct-Buried Insulated Pipes

Polyurethane direct‑buried insulated pipes are prefabricated, directly buried insulation solutions that offer excellent thermal performance, high safety and reliability, and low installation costs. These pipes not only surpass traditional trench‑laying and overhead‑suspended pipelines in advanced technology and practicality but also deliver significant social and economic benefits, serving as an effective measure for heating energy conservation. The adoption of direct‑buried heating pipeline technology marks a new milestone in the development of China’s heating pipeline engineering. As global energy resources dwindle and demand continues to rise, energy efficiency, emission reduction, and environmental protection have become worldwide trends. National and local governments alike are vigorously promoting the development, application, and industrialization of energy‑saving, emission‑reducing, and environmentally friendly products. In the construction sector, rigid polyurethane foam insulation materials represent an important segment of the polyurethane industry, distinguished by their versatility—providing simultaneous thermal insulation, waterproofing, and other functions. Since their introduction into European construction in the 1960s, these products have enjoyed a history spanning four decades; some countries have even enacted legislation designating polyurethane as the preferred material for both insulation and waterproofing in building applications. In recent years, with the rapid expansion of China’s building energy‑efficiency market, rigid polyurethane foam insulation has found widespread use in thermal insulation and waterproofing, emerging as one of the leading insulation and energy‑saving products on the market. As an integrated thermal insulation and waterproofing material, rigid polyurethane foam breaks away from the conventional limitation of single‑purpose building materials—where waterproofing fails to insulate, and insulation fails to waterproof—and eliminates the common issue of insulation losing its effectiveness once the waterproofing layer develops leaks. Compared with other single‑function insulation or waterproofing materials, rigid polyurethane foam offers distinct advantages: 1. It combines multiple functions in one material, providing thermal insulation, waterproofing, soundproofing, vibration absorption, and more. 2. Its thermal insulation performance is outstanding: among all domestic building materials, it boasts the lowest thermal conductivity (≤0.024) and the highest thermal resistance, with a thermal conductivity only half that of EPS expanded polystyrene boards. 3. Rigid polyurethane foam features a continuous, dense surface skin and nearly 100% closed-cell structure with strong interconnections, delivering ideal impermeability. When applied via spray‑on methods, it creates seamless, joint‑free waterproofing and insulation layers, forming leak‑proof roofs and monolithic exterior wall insulation shells with superior water‑resistance and anti‑seepage properties. 4. It exhibits exceptionally strong self‑adhesive properties—requiring no additional bonding agents—ensuring firm adhesion to roofing and exterior walls while offering excellent resistance to wind uplift and negative wind pressure. Full‑area spray application completely eliminates “thermal bridges” and “cold bridges,” and its flexible gradient technology effectively prevents cracking of the waterproofing layer. Mechanized operations, automated batching, consistent quality, rapid installation, and short project timelines further enhance efficiency. 5. Chemically stable with a long service life, it does not pollute the surrounding environment; it self‑extinguishes upon exposure to open flames and, when burned, chars rather than dripping, with the size and shape of the charred layer remaining largely unchanged. This helps block air ingress and inhibit fire spread, ensuring excellent fire‑safety performance. As the only integrated thermal insulation and waterproofing material currently available, rigid polyurethane foam is still in its early stages of adoption within China’s construction industry. Fortunately, to accelerate innovation in building insulation materials and promote the wider application of rigid polyurethane foam in energy‑efficient construction, the Ministry of Construction has established a dedicated “Polyurethane Building Energy‑Efficiency Application Working Group” to advance the use of this material across China’s energy‑saving construction sector. Polyurethane insulated pipes possess numerous outstanding characteristics, including light weight, high strength, excellent thermal insulation, soundproofing, flame retardancy, cold resistance, corrosion resistance, non‑absorbency, and ease and speed of installation, making them indispensable for thermal insulation, waterproofing, sealing, and leak‑prevention in industries such as construction, transportation, petroleum, chemical processing, power generation, and refrigeration. (For steel pipe purchases, contact Chengyuan.) 1. Low thermal conductivity: Among insulation materials, polyurethane foam exhibits the lowest thermal conductivity, thereby minimizing heat loss in applications.

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Guangxi Nanning Canghai Steel Co., Ltd. All rights reserved

by:www.300.cn

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