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Causes and Solutions for Common Defects in Spiral Welded Steel Pipe Joints

2019/08/10

Causes and Solutions for Common Defects in Spiral Welded Steel Pipe Joints

The common defects in spiral steel pipe welds mainly arise from the following causes. Let’s take a look at what they are and how to address them. The first common issue is uneven weld bead width or curvature. This can result from inconsistent welding speed, unstable welding voltage, uneven wire feed rate, poor conductivity of the welding wire, contamination on the wire surface, unreliable conductivity of the contact tip, excessive oxide scale along the groove edges, improper flux cup and rubber baffle, or overly large flux particles and excessive powder. To remedy this, maintain stable welding parameters, troubleshoot any malfunctions in the wire‑feeding mechanism, clean oil and contaminants from the wire surface, replace the contact tip with one of appropriate diameter—ensuring the internal conductive section is not excessively long—thoroughly clean the groove, properly position the flux cup and rubber baffle, and ensure uniform flux particle size. The second common problem is excessive weld reinforcement. This occurs when the current is too high while the voltage is too low, the uphill welding angle is excessively steep, or the wire feed rate is too fast, leading to excessive wire melting. Solutions include adjusting the welding parameters, modifying the uphill welding angle, and fine-tuning the wire feed speed. The third frequent defect is undercut. It arises from improper wire positioning or angle, excessive current combined with low voltage, overly rapid welding speed, misalignment during forming, excessive buildup, uneven wire feeding, inadequate fixation of the welding torch, or torch oscillation during welding. Remedies involve adjusting the wire position or angle, optimizing process settings—avoiding excessive current—eliminating misalignment or excessive buildup, replacing the wire feed roller or bearings, inspecting and repairing the electrical system, and securely fixing the welding torch. The fourth common issue is lack of fusion. This typically results from misaligned wire placement,偏于坡口一侧 (biased toward one side of the groove), excessive local curvature of the weld, or insufficient welding current. Corrective measures include adjusting the wire position, focusing attention and executing precise operations, and fine-tuning the welding current. The fifth frequent problem is incomplete penetration. Causes include misaligned wire placement, significant deviation from the intended position, insufficient welding current or excessive voltage, overly rapid welding speed, excessively blunt groove edges or too small groove angles, inadequate cleaning of the weld root, and overly narrow forming gaps. Solutions involve restoring the wire to its proper position, adjusting both welding current and voltage, regulating welding speed, correcting the groove’s blunt angle and included angle, thoroughly cleaning the weld root, and optimizing forming gap dimensions. The sixth common defect is slag inclusion. This occurs when edge surfaces are not clean, interpass slag removal is incomplete in multi‑layer welding, welding current is too low, welding speed is too fast, wire positioning is improper, molten slag and metal fail to separate adequately, the weld bead’s width‑to‑depth ratio is too small, undercut is severe, groove angles are too shallow, or the flux is contaminated with foreign matter. Typical remedies include cleaning both edges of the strip steel, ensuring thorough interpass slag removal, adjusting welding current and voltage, repositioning the wire, increasing the weld bead’s width‑to‑depth ratio, enlarging the groove angle, and removing impurities from the flux.

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Classification of Spiral Welded Steel Pipes

2019/04/17

Classification of Spiral Welded Steel Pipes

Pressure‑bearing fluid conveyance: spiral‑seam submerged‑arc welded steel pipe, conforming to SY 5036‑2000, is primarily used for oil and natural gas pipelines. Spiral‑seam high‑frequency welded steel pipe, specified in SY 5038‑2000, is manufactured by high‑frequency lap welding and likewise employed for pressure‑bearing fluid transport. These pipes exhibit strong pressure resistance, good ductility, and are easy to weld and form. For general low‑pressure fluid conveyance, spiral‑seam submerged‑arc welded steel pipe, designated as SY 5037‑2000, is produced via double‑sided automatic submerged‑arc welding or single‑side welding. It is intended for transporting water, coal gas, air, steam, and other common low‑pressure fluids. Common standards for spiral‑welded steel pipes generally include: SY/T 5037‑2008 (a ministry‑level standard, also known as spiral‑seam submerged‑arc welded steel pipe for ordinary fluid conveyance); GB/T 9711.1‑2008 (a national standard, referred to as the technical delivery requirements for steel pipes used in the petroleum and natural gas industries—Part I: Grade A steel pipe; stricter requirements apply to GB/T 9711.2 Grade B steel pipe); API 5L (the American Petroleum Institute standard, also called line pipe, with two grades—PSL1 and PSL2); and SY/T 5040‑2008 (spiral‑welded steel pipe for pile applications). SY/T 5037‑2008, established by the Ministry of Petroleum, is commonly referred to as a “ministry standard.” GB/T 9711.1‑2008 specifies national spiral‑welded pipes for the petroleum and natural gas industries, classified as Grade A. General low‑pressure fluid‑conveying spiral‑seam high‑frequency welded steel pipe (SY 5039‑2000) is fabricated from hot‑rolled steel strip coils serving as tube blanks, formed into spirals at ambient temperature, and welded using high‑frequency lap welding. Spiral‑welded steel pipe for pile applications (SY 5040‑2000) is made from hot‑rolled steel strip coils as tube blanks, shaped into spirals at room temperature, and manufactured through either double‑sided submerged‑arc welding or high‑frequency welding. It is utilized as foundation piles in civil engineering structures, wharves, bridges, and similar applications.

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How to maintain and enhance the stability of spiral steel pipes

2019/04/17

How to maintain and enhance the stability of spiral steel pipes

How to Maintain and Enhance the Stability of Spiral Steel Pipes I. Medium- and small-sized structural steel, wire rod, reinforcing bars, medium‑diameter steel pipes, steel wires, and steel ropes may be stored in well‑ventilated sheds, provided they are covered on top and supported on the bottom. II. Certain small‑size steel products—such as thin steel plates, steel strips, silicon steel sheets, small‑diameter or thin‑walled steel pipes, various cold‑rolled and cold‑drawn steel items—as well as high‑value, corrosion‑prone metal goods, may be kept indoors in a warehouse. III. The site or warehouse for storing spiral steel pipe products should be located in a clean, well‑drained area, away from factories and mines that generate harmful gases or dust. The ground must be cleared of weeds and all debris to keep the steel clean. IV. Large‑section structural steel, rails, heavy steel plates, large‑diameter steel pipes, forgings, and similar items may be stacked outdoors. V. Warehouses must not store steel together with corrosive materials such as acids, alkalis, salts, or cement. Different grades of steel should be stored separately to avoid confusion and prevent contact corrosion. VI. Warehouse selection should be based on local conditions; generally, standard enclosed warehouses are preferred—structures with roofs, perimeter walls, tightly sealed doors and windows, and adequate ventilation systems. VII. Warehouses should ensure proper ventilation on sunny days and be kept closed to prevent moisture ingress during rainy weather, maintaining an appropriate storage environment at all times.

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Epoxy-Coated Steel Pipe Manufacturing Process

2019/04/07

Epoxy-Coated Steel Pipe Manufacturing Process

Epoxy‑Coated Anti‑Corrosion Steel Pipes I. Composition: 1. Steel pipes: including seamless steel pipes, straight‑seam steel pipes, spiral‑welded steel pipes, and various other steel pipelines. 2. Epoxy coating: This product is a two‑component, high-solids epoxy coating, available in primer and topcoat forms. Component A consists of epoxy resin, pigments, fillers, and additives; Component B is a modified amine‑based curing agent [1]. II. Properties and Applications: - Excellent durability: The cured epoxy film is tough, water‑resistant, non‑toxic, and environmentally harmless. - Strong adhesion: Outstanding bonding between coating layers. - Superior rust resistance and water resistance: Utilizing premium anti‑corrosion ingredients to ensure long‑term protection. - High mechanical strength: The coating film is robust, offering excellent wear resistance and impact resistance. - High solids content: Produces a relatively thick coating film. - Cures at room temperature: No need for large-scale baking equipment. Widely applicable for internal lining of water tanks, pipelines, reservoirs, water towers, and other water‑supply facilities, as well as for cargo holds transporting sugar, grains, and similar materials. It can also be used as an interior coating for swimming pools, power‑plant cooling towers, and metal or concrete structures storing fuel oil, gasoline, and other substances. III. Application and Storage: 1) Prior to coating, thoroughly clean the substrate surface of dust, oil, scale, and other contaminants to achieve Sa2.5 cleanliness, ensuring optimal coating quality. Avoid introducing any moisture during application. 2) Mixing procedure: Open Component A completely, add Component B to Component A, and mix thoroughly until uniform. Allow the mixture to mature for 30 minutes before application. 3) This material must be mixed and used immediately; any prepared coating should be applied within eight hours. Unmixed portions must be tightly sealed and stored. Halt work on rainy days or when relative humidity exceeds 75%. For areas exposed to severe corrosive environments, multiple coats are recommended. 4) Store the product in a cool, dry place, protected from direct sunlight, away from open flames and heat sources. Shelf life is twelve months; upon expiration, re‑evaluate all technical parameters. If the product meets the required specifications, it may continue to be used.

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Trump’s latest decision may help ease the trade dispute with China.

2018/06/28

Trump’s latest decision may help ease the trade dispute with China.

On June 27, the Business Insider website reported that U.S. President Trump announced on Wednesday details of a plan to restrict Chinese investment in American technology companies, including an expansion of the powers of the Committee on Foreign Investment in the United States (CFIUS)—a move considerably more moderate than previously anticipated. The report noted that both the House and Senate are considering the “Foreign Investment Risk Review Modernization Act.”

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Massive procurement of national-standard large-diameter spiral steel pipes

2018/05/11

Massive procurement of national-standard large-diameter spiral steel pipes

Large-diameter spiral steel pipes refer to spiral steel pipes with a nominal diameter of DN850 or greater. The primary raw material used in their production is strip steel. Spiral steel pipes generally have higher strength than straight-seam welded pipes, allowing for the manufacture of larger‑diameter pipes from narrower billets, and enabling the production of pipes with different diameters from billets of the same width. Large‑diameter spiral steel pipes are manufactured using double‑sided submerged arc welding, which offers advantages such as stable weld quality, high welding productivity, minimal arc radiation, and reduced fumes and dust. Key parameters include outer diameter, wall thickness, and length. Mechanical tests typically encompass hydrostatic pressure testing, bending tests, and flattening tests. The applicable standards include: SY/T 5037-2008 (a ministry standard, also known as spiral seam submerged arc welded steel pipe for general fluid conveyance); GB/T 9711.1-2008 (a national standard, also referred to as steel pipe for oil and gas transportation); API 5L (American Petroleum Institute standard, also called pipeline steel pipe); SY/T 5040-2008 (spiral seam welded steel pipe for pile applications); and SY 5039-2000 (general low‑pressure fluid transport spiral seam high‑frequency welded steel pipe). The main grades used are Q235A, Q235B, 20#, Q345 (16Mn), and pipeline steels ranging from X42 to X70. Their primary applications include: liquid transport—such as water supply and drainage; gas transport—such as coal gas, steam, and liquefied petroleum gas; and structural uses—such as piling tubes, bridge construction, and piping for docks, roads, and building structures. Below is a brief overview of several types of welded pipes and their applications: 1. General welded pipes are used for conveying low‑pressure fluids such as water, coal gas, air, oil, and heating steam. 2. Ordinary carbon steel conduit pipes (GB 3640-88) are steel tubes employed in electrical installation projects—such as industrial and civil buildings and machinery installations—to protect electrical wires. 3. Straight‑seam electric welded pipes (YB 242-63) are steel pipes whose weld seams run parallel to the longitudinal axis of the pipe. They are commonly categorized into metric electric welded pipes, thin‑walled electric welded pipes, transformer cooling oil pipes, and others. 4. Spiral seam submerged arc welded pipes for pressurized fluid conveyance (SY 5036-83) are manufactured by rolling hot‑rolled steel strips into pipe blanks, forming them into spirals at room temperature, and then welding them using double‑sided submerged arc welding. These pipes are designed for transporting pressurized fluids, offering strong pressure resistance, excellent weldability, and proven safety through rigorous scientific inspections and tests. With large diameters and high conveying efficiency, they help reduce capital costs associated with pipeline installation. They are primarily used for oil and natural gas pipelines. 5. Spiral seam high‑frequency welded pipes for pressurized fluid conveyance (SY 5038-83) are produced by rolling hot‑rolled steel strips into pipe blanks, forming them into spirals at room temperature, and welding them using high‑frequency lap welding. These pipes exhibit strong pressure resistance, good ductility, and ease of welding and shaping. After undergoing stringent scientific inspections and tests, they demonstrate reliable performance, large diameters, and high conveying efficiency, while also reducing pipeline installation costs. They are mainly used for laying pipelines that transport oil and natural gas. 6. General low‑pressure fluid transport spiral seam submerged arc welded pipes (SY 5037-83) are manufactured by rolling hot‑rolled steel strips into pipe blanks, forming them into spirals at room temperature, and employing either double‑sided automatic submerged arc welding or single‑sided welding techniques. These pipes are specifically designed for conveying low‑pressure fluids such as water, coal gas, air, and steam.

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Steel prices have risen by more than 1,000 yuan, and steelmakers have generally turned losses into profits.

2017/03/20

Steel prices have risen by more than 1,000 yuan, and steelmakers have generally turned losses into profits.

Since the first half of last year, steel prices have begun to recover, driven by supply-side reforms and measures to phase out outdated production capacity. Taking rebar as an example, its average price on March 9 last year was 2,475 yuan per ton, while on March 9 this year it had risen to 3,852 yuan per ton—a 35% increase. Benefiting from rising steel prices, steel companies’ financial performance improved markedly last year. In 2015, Nangang Co., Ltd., Liugang Co., Ltd., and *ST Shaogang reported losses of 2.432 billion yuan, 1.189 billion yuan, and 2.596 billion yuan, respectively; in 2016, these three companies posted profits of 350 million yuan, 185 million yuan, and 101 million yuan, respectively. According to data from the China Iron and Steel Association, in 2016, large and medium-sized steel enterprises recorded total sales revenue of 2.80 trillion yuan, down 1.81% year-on-year, yet their combined profits reversed from a loss of 84.7 billion yuan in 2015 to a gain of 30.378 billion yuan, marking an overall turnaround for China’s steel industry. Since 2016, the steel sector has also embarked on a capacity‑reduction drive. However, according to the National Bureau of Statistics, China’s crude steel, pig iron, and steel output in 2016 reached 808 million tons, 701 million tons, and 1.139 billion tons, up 1.24%, 0.74%, and 2.30% year-on-year, respectively. China’s share of global crude steel production rose to 49.6%, an increase of 0.2 percentage points over the previous year. Domestic apparent consumption of crude steel stood at 709 million tons, up 2.08% year-on-year. This indicates that capacity cuts have not significantly curtailed steel output, suggesting that the sharp price surge is closely tied to fluctuations in demand. On March 5, the government’s work report for this year explicitly stated: “This year, we will further cut steel capacity by approximately 50 million tons and retire more than 150 million tons of coal‑related capacity. At the same time, we will phase out, suspend construction on, or slow down over 50 million kilowatts of coal‑fired power capacity, aiming to mitigate risks associated with excess coal‑power capacity, enhance industry efficiency, and create room for the development of clean energy.” Although this year’s targets—50 million tons of steel capacity and 290 million tons of coal capacity—are lower than last year’s actual reductions of 65 million tons of steel and 290 million tons of coal—the majority of last year’s cuts targeted inefficient capacity, while overall output continued to hit record highs. Consequently, this year’s supply‑side capacity reduction is expected to move toward more substantive progress, particularly with the complete elimination of “strip steel” capacity in the first half of the year, which will have a tangible impact on market supply. As the market enters the peak consumption season of “Golden March and Silver April,” demand is anticipated to improve further. On the supply side, the National Development and Reform Commission has announced a comprehensive ban on the use of power‑frequency and medium‑frequency induction furnaces for producing construction steel in the first half of the year. Meanwhile, during the Two Sessions, steel mills in North China were subject to a 50% production cut, and the Ministry of Environmental Protection conducted unscheduled environmental inspections—all of which are likely to constrain overall supply, especially for construction steel. Nangang Co., Ltd. On March 10, 2017, Nangang Co., Ltd. issued an announcement forecasting a significant increase in first‑quarter earnings for 2017. The company expects net profit attributable to shareholders of the listed company to reach 400–500 million yuan, representing a substantial year‑on‑year improvement. While strengthening its core steel business, the company is actively pursuing transformation and upgrading, planning to integrate its existing diversified industrial resources and external investment platforms to focus on emerging sectors such as energy conservation, intelligent manufacturing, and Internet Plus. It is also aligning closely with the development plan of Nanjing’s Jiangbei New Area. In 2015, the company established Jin Kai Energy Conservation and Environmental Protection Investment Holding Co., Ltd., consolidating its internal energy‑conservation and environmental‑protection operations into this platform, thereby laying a solid foundation for the growth of these industries. Moving forward, the company intends to adopt a strategy of collaborative partnerships combined with independent integration, concentrating on areas such as solid waste treatment, wastewater treatment, and waste‑heat power generation, with the aim of swiftly bringing relevant projects to fruition. Liugang Co., Ltd. As Guangxi’s sole integrated steel producer, Liugang holds an overwhelming dominant position in the region’s steel market. The company is also expanding into neighboring provinces such as Guangdong and Hainan, dispatching technical personnel to maintain long‑term presence in Guangdong. In 2015, its building‑material products saw a significant rise in market share across Guangxi. In the first half of 2016, the company further reduced rail freight rates for its steel products, making Yunnan, Guizhou, Sichuan, as well as Changsha and Guangzhou, part of a unified regional market with consistent transportation costs. Additionally, the company’s e‑commerce platform has introduced timely trading models—including spot sales, auction sales, and forward contracts—to serve key infrastructure projects and directly supply end users. *ST Shaogang *ST Shaogang released its 2016 annual report, reporting operating revenue of 13.973 billion yuan, up 25.38% year on year; operating costs of 13.326 billion yuan, up 6.40% year on year; and net profit attributable to shareholders of the listed company of 101 million yuan, compared with a loss of 2.596 billion yuan in the same period last year. Earnings per share (EPS) for 2016 stood at 0.04 yuan, versus −1.07 yuan in the prior year. As Guangdong Province’s largest steelmaker, *ST Shaogang’s main products—rebar, wire rod, and shipbuilding plates—command market shares of 13%, 16%, and 10%, respectively, within the province. The company’s successful turnaround in 2016 was primarily driven by a recovery in industry conditions, increased non‑recurring gains, and cost optimization.

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The development of seamless steel pipe manufacturing technology has gone through three major stages.

2016/10/11

The development of seamless steel pipe manufacturing technology has gone through three major stages.

Over the past century and more since the Mannesmann brothers invented the rotary piercing process, the development of seamless steel pipe manufacturing technologies has progressed through three distinct phases: 1. From the 1880s to the 1930s—nearly half a century—seven major pipe‑making processes emerged in succession: the periodic rolling mill (1892), the push‑through mill (1899), the continuous rolling mill (1901), the automatic rolling mill (1903), the Dieser rolling mill (1932), the three‑roll rolling mill (1937), and the extrusion mill. All these processes had reached industrial maturity and gradually became standardized; at the time, the automatic and periodic rolling mills were widely adopted, while pipes produced by the push‑through and three‑roll mills accounted for only a small share. Meanwhile, the continuous rolling mill and the Dieser rolling mill saw little further development. 2. During the roughly four decades from the 1940s to the early 1980s, the fully floating mandrel continuous rolling process experienced significant advancement, as evidenced by the commissioning of two rolling mills in the United States and two continuous rolling mills in Germany. The introduction of the MPM rolling mill at Dalmine’s Bergamo plant in 1978 and the semi‑floating mandrel continuous rolling mill at Yawata in 1983 marked the beginning of a new phase in which three distinct continuous rolling processes coexisted. During this period, developments in seamless steel pipe production also included the evolution of the push‑through process into the CPE process, the widespread adoption of tension‑reduction techniques, and the successful use of continuously cast round billets as raw material for pipe rolling. 3. Since the early 1980s, over the past two decades, both the three‑roll rolling mill and the Dieser rolling mill have undergone improvements, giving rise to new types of three‑roll mills and the Accu‑Roll mill. In addition, the three‑roll planetary rolling mill (1982), the GPS process (1989), and the PQF process (1993) have all been introduced. It is worth noting that the resurgence of the conical‑roller piercing machine represents a major breakthrough in this stage, one that will exert a profound influence on the future evolution of seamless steel pipe manufacturing technology.

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

by:www.300.cn

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