Analysis of advantages and disadvantages of seamless steel pipe
As a "high-end representative" in the field of steel pipes, seamless steel pipes have long occupied the market of core scenes such as ultra-high pressure and special medium transmission, from deep-sea oil field exploitation to nuclear power auxiliary systems, from aerospace pipelines to chemical high-pressure reaction devices. Hebei Huayang Steel Pipe has been deeply involved in seamless steel pipe production for 18 years, and several intelligent seamless steel pipe production lines have been built, with an annual production capacity of 500,000 tons. The X80 and Q345E seamless steel pipes supplied by Hebei Huayang Steel Pipe have been applied to major projects such as Bohai deep-sea oil fields and oil and gas pipelines in Central Asia. However, seamless steel pipe is not a "perfect choice", and its application scope is also limited by shortcomings such as high cost and low efficiency. Based on the production practice and industry data of Huayang steel pipe, this paper comprehensively analyzes the advantages and disadvantages of seamless steel pipe, and provides professional reference for project selection.
Advantages: What is the core competitiveness of seamless steel pipe?
Uniform and stable mechanical properties, is it a "safety benchmark" for extreme working conditions?
The most outstanding advantage of seamless steel pipe is the uniformity and stability of mechanical properties, which stems from its unique "solid billet piercing- rolling" production process-no welding is needed, which avoids the possible defects such as slag inclusion, incomplete penetration and porosity in the weld area, and the continuity and integrity of the metal matrix are preserved to the greatest extent. According to the test data of CNAS Certification Laboratory of Huayang Steel Pipe, under the same specification (DN200, wall thickness 10mm), the tensile strength of seamless steel pipe can reach 550-620MPa, the yield strength is 345-420MPa, the impact toughness at -20℃ is ≥40J, and the fluctuation range of various mechanical indexes is controlled within 5%, which is far better than that of ERW longitudinal welded pipe (fluctuation range is 12%).
This advantage is more obvious in the verification of extreme working conditions. In the Bohai Deepwater Oilfield Project in 2023, the DN200 seamless steel pipe supplied by Huayang has to withstand a high pressure of 12MPa (equivalent to a water depth pressure of 1200 meters) and a low temperature of -20℃. After 1000 hours of simulated service test, the pipeline has no deformation or leakage, and the risk of failure related to welds is zero. "The seamless structure of seamless steel pipe fundamentally eliminates weld cracking, the most common failure form of welded pipe, and is the best choice for ultra-high pressure scenarios." The technical director of Huayang Steel Pipe said that seamless steel pipes account for more than 90% in areas with extremely high safety requirements such as nuclear power auxiliary cooling water pipelines and aerospace hydraulic pipelines.
Can outstanding high-pressure and high-temperature resistance adapt to special media transmission?
The material purity and structural integrity of seamless steel pipe make it have excellent high-pressure and high-temperature resistance, and at the same time, it can meet the transmission requirements of corrosive, radioactive and other special media. For different scenarios, Huayang Steel Pipe can produce seamless steel pipes covering Q235, Q345, X70, X80 and other steel grades, among which X80 seamless steel pipes can withstand the highest high pressure of 15MPa, and 316L stainless steel seamless steel pipes can run stably at 450℃ for a long time.
In the chemical field, in the high-pressure hydrogenation unit of a large petrochemical enterprise, the 316L seamless steel pipe supplied by Huayang is used to transport corrosive media containing hydrogen and hydrogen sulfide, with an operating pressure of 8MPa and a temperature of 380℃, and has been in stable service for 3 years, without any corrosion and leakage problems. In the scene of radioactive medium transmission, the seamless steel pipe structure can avoid the radioactive material staying at the weld and reduce the risk of leakage, so it is widely used in the radioactive waste liquid and waste gas transmission pipeline of nuclear power plants. Huayang's test data show that the qualified rate of corrosion resistance and sealing test of nuclear-grade seamless steel pipes produced by Huayang is 100%, which is much higher than the industry average of 95%.
Can high dimensional accuracy reduce the difficulty of field installation?
The production process of seamless steel pipe needs many precise rolling and straightening procedures, and the dimensional accuracy is much higher than that of welded pipe. The seamless steel pipe production line of Huayang steel pipe adopts intelligent straightening system, and the roundness deviation can be controlled within ±0.5mm, the wall thickness uniformity error is less than or equal to 1%, and the straightness deviation per meter is less than or equal to 0.3 mm.. This high-precision feature greatly reduces the difficulty of field installation and improves the installation efficiency and sealing performance.
In the hydraulic system project of an urban rail transit in 2024, due to the high dimensional accuracy, the qualified rate of DN50 seamless steel pipe supplied by Huayang reached 99.8%, which was significantly higher than that of 95% when ordinary welded pipe was used, and the installation period was shortened by 20%. "High-precision seamless steel pipe can reduce the counterpart deviation during installation and avoid the sealing failure caused by size mismatch, especially in the scenes with high installation accuracy requirements such as precision equipment pipelines and hydraulic systems, and its advantages are irreplaceable." The person in charge of project installation commented.
Limitations: Where are the application restrictions of seamless steel pipes concentrated?
Is the high production cost the main obstacle to its popularization?
High cost is the core limitation of seamless steel pipe, which stems from its complex production process and low utilization rate of raw materials. Seamless steel pipe takes solid billet as raw material, which needs to go through many processes such as heating, piercing, rolling, sizing, etc. Among them, the piercing process will produce a lot of waste, and the utilization rate of raw materials is only about 75%, while that of ERW welded pipe can reach 95%, and SSAW welded pipe can reach 92%. At the same time, the production cycle of seamless steel pipe is long, and the production time per ton is about 4-6 hours, which is 3 times that of ERW welded pipe and 2 times that of SSAW welded pipe.
The cost difference is particularly obvious in actual procurement. According to the quotation data of Huayang Steel Pipe, the unit price of Q345 seamless steel pipe with the same specification (DN300, wall thickness 10mm) is about 8500 yuan/ton, while the unit price of ERW welded pipe is only 5200 yuan/ton, and the unit price of SSAW welded pipe is 5800 yuan/ton. The cost of seamless steel pipe is 40%-60% higher than that of welded pipe. In the long-distance and large-diameter water and gas transmission projects, the high cost makes it difficult to popularize seamless steel pipes. For example, if all seamless steel pipes are used in a long-distance water conveyance project, the total cost will increase by more than 30%, so it is only used in key nodes such as high-pressure pumping stations, and ERW welded pipes are used in other sections.
Is the low production efficiency and difficult to meet the needs of large-scale batch production?
The production process of seamless steel pipe is complex, with multiple processes and long lead time, which leads to its production efficiency far lower than that of welded pipe, and it is difficult to meet the requirements of large-scale with short leas time projects. The data of Huayang Steel Pipe shows that the daily production capacity of a seamless steel pipe production line is about 50 tons, while the daily production capacity of an ERW welded pipe production line can reach 300 tons, and the daily production capacity of SSAW welded pipe production line can also reach 250 tons. In emergency projects, this gap is more prominent.
In the Henan emergency water supply project in 2024, 10,000 tons of steel pipes need to be supplied within 10 days, and Huayang Steel Pipe urgently started three ERW welded pipe production lines, which were delivered in only 8 days. If the seamless steel pipe production line is adopted, even if all five production lines are started, it will take 40 days to complete, which cannot meet the emergency demand at all. "Seamless steel pipes are more suitable for small-batch, high-precision and high-demand customized orders, and the cost performance of large-scale batch demand is extremely low." The production director of Huayang Steel Pipe said that among his company's seamless steel pipe orders, customized orders with a batch size of less than 500 tons accounted for more than 70%.
Is large-diameter production limited,and can it meet the requirements of major projects?
The production of seamless steel pipe is limited by billet size and piercing process, and the production of large-caliber products is extremely difficult, and the cost will increase exponentially. At present, the largest diameter of domestic mainstream seamless steel pipe is about DN600, while the largest diameter of ERW welded pipe can reach DN1600, and LSAW welded pipe can reach DN2000, which can completely cover the large-diameter requirements of large-scale projects.
In large-scale long-distance pipeline projects such as West-to-East Gas Pipeline and Central Asia Energy Pipeline, the diameter of the main pipeline is mostly DN1200-DN1600, and the seamless steel pipe can not be used as the main pipeline due to the diameter limitation, and it is only used in small-diameter high-pressure scenes such as branch high-pressure sections and wellhead. Huayang Steel Pipe tried to produce DN600 seamless steel pipe, and found that its cost per ton increased by 80% compared with DN300 seamless steel pipe, and the qualified rate of production was only 85%, which was far lower than 99% of small-diameter seamless steel pipe. "The production of large-diameter seamless steel pipes requires larger billets and more sophisticated piercing equipment, and the input-output ratio is extremely low. Few enterprises in the industry produce them on a large scale." The person in charge of research and development of Huayang Steel Pipe explained.
Will complex downstream processing lead to higher total project costs?
The material of seamless steel pipe has high hardness and good toughness, and the subsequent cutting, welding and bending are much more difficult than welded pipe, which requires special equipment and a construction team with higher technical level, which will further increase the comprehensive cost of the project. The after-sales technical service data of Huayang steel pipe shows that the on-site welding time of seamless steel pipe is 1.5 times that of welded pipe, the cost of welding consumables increases by 20%, and the technical level of welders is higher, which requires personnel with welding qualification of high-pressure pipeline to operate.
In the pipeline reconstruction project of a chemical industry park, the welding construction of 1000m DN150 seamless steel pipe was involved. Due to the great processing difficulty, the construction team invested two additional special welding equipments and three senior welders, and the construction cost increased by 25% compared with that when welded pipes were used. "Many project parties will ignore the subsequent processing costs and only pay attention to the purchase price of steel pipes, and finally find that the comprehensive cost of seamless steel pipes is much higher than expected." The after-sales engineer of Huayang Steel Pipe reminded that the whole process cost such as procurement, processing and installation should be considered comprehensively in project selection.
Selection suggestion: What scenarios are seamless steel pipes suitable for?
Combining the advantages and disadvantages of seamless steel pipe, based on 22 years' project experience, Huayang Steel Pipe has summed up a clear selection boundary: when the project needs ultra-high pressure (≥10MPa), high temperature (≥300℃), special medium (corrosive, radioactive) and high-precision installation, the advantages of seamless steel pipe can make up for its short cost, and it is the best choice. However, in long-distance, large-diameter, medium and low-pressure common transmission scenarios, or large-scale batch and emergency delivery projects, welded pipes (ERW, LSAW, SSAW) are more cost-effective and more suitable for selection.
For example, seamless steel pipes are indispensable in wellhead high-pressure pipelines in deep-sea oil fields, radioactive medium transmission pipelines in nuclear power plants, and aerospace hydraulic systems. In urban municipal water supply, general gas transmission trunk lines, long-distance irrigation and other projects, welded pipes are more economical and reasonable. The order data of Huayang Steel Pipe in 2024 also confirmed this rule: in seamless steel pipe orders, ultra-high pressure and special media scenes accounted for 82%, while in welded pipe orders, municipal and long-distance trunk scenes accounted for 75%.
Conclusion: Objectively evaluating both advantages and disadvantages and ensuring precise adaptation is essential
Seamless steel pipe has become the "safety cornerstone" in extreme working conditions and high-end fields because of its advantages of no seam, high strength and high precision, but its short board with high cost, low efficiency and limited large diameter also determines that it cannot completely replace welded pipe. The practice of Hebei Huayang Steel Pipe has proved that there is no "optimal solution" for steel pipe selection, and only "optimal solution"-fully understanding the advantages and disadvantages of seamless steel pipe, combining the pressure grade, media characteristics, size requirements, cost budget and delivery cycle of the project, can we choose a scheme with both safety and economy.
In the future, with the innovation of rolling technology and material technology, the production cost of seamless steel pipe may be gradually reduced, the large-diameter production capacity will also be improved, and its application scope is expected to be further expanded. However, no matter how the technology develops, it is always the core logic of steel pipe selection to face up to the advantages and disadvantages and accurately adapt to the scene, and it is also the key to ensure engineering safety and control costs.
