Q345E hot-rolled seamless steel pipe is a high-quality steel widely used in construction, machinery, petroleum, chemical, and power industries. Its excellent mechanical properties and processing characteristics make it an indispensable material in modern industry.
First, the material characteristics and standards of Q345E hot-rolled seamless steel pipe.
Q345E belongs to low-alloy high-strength structural steel and conforms to the GB/T 1591-2018 standard. In its naming, “Q” represents yield strength, “345″ indicates that the lower limit of yield strength is 345MPa, and “E” represents low-temperature impact performance at -40℃, indicating that the material can maintain high toughness in extremely cold environments. Compared with ordinary Q345B/C, Q345E significantly improves its low-temperature resistance to brittle fracture by adding microalloying elements such as niobium and vanadium and strictly controlling the phosphorus and sulfur content. Chemically, Q345E has a carbon content controlled below 0.18%, a manganese content of 1.00%~1.60%, and contains small amounts of silicon, titanium, and other elements. In terms of mechanical properties, its tensile strength can reach 470~630MPa, elongation ≥21%, and impact energy at -40℃ ≥27J, exhibiting both high strength and good plasticity. Furthermore, the hot-rolled seamless process results in a dense internal structure, free of weld defects, and significantly superior pressure resistance and fatigue life compared to welded steel pipes.
Second, the production process and key technologies of Q345E hot-rolled seamless steel pipes.
The production process of Q345E hot-rolled seamless steel pipes mainly includes steelmaking, billet heating, piercing, rolling, sizing, cooling, and finishing:
1. Steelmaking and continuous casting: Converter or electric furnace smelting is used. LF ladle refining and VD vacuum degassing ensure the purity of the molten steel. After continuous casting into billets, surface inspection is required.
2. Hot Rolling Forming: After heating the round billet to approximately 1200℃, it is formed into a hollow tube through a piercing mill, and then extended by a continuous rolling mill for wall reduction. The final rolling temperature (approximately 850℃) must be strictly controlled during hot rolling to avoid grain coarsening.
3. Heat Treatment Process: Some high-requirement pipes undergo normalizing treatment to refine the grains, homogenize the microstructure, and further improve low-temperature toughness.
4. Inspection and Straightening: Finished products undergo non-destructive testing such as ultrasonic flaw detection and eddy current testing, and straightness correction is performed to ensure dimensional accuracy and surface quality.
Third, Core Application Areas of Q345E Hot-Rolled Seamless Steel Pipes.
1. Energy Transmission: Widely used in oil and gas pipelines, especially in high-altitude and cold regions (such as Siberia and Arctic Circle projects), its low-temperature toughness effectively prevents pipeline freezing and cracking.
2. Construction Machinery: As a key component of hydraulic supports and crane booms, it withstands high dynamic loads.
3. Building Structures: Suitable for supporting columns in super high-rise buildings and bridges, such as the pile foundation pipes for cross-sea bridges, with weather resistance superior to ordinary carbon steel.
4. Special Equipment: High-pressure pipelines for chemical reactors and power plant boilers, requiring compliance with GB 5310-2017 high-pressure boiler tube standards.
Fourth, Market Status and Competitive Landscape of Q345E Hot-Rolled Seamless Steel Pipes.
Currently, domestic Q345E seamless steel pipe production capacity is mainly concentrated in large steel mills, with hot-rolling accounting for approximately 60%. According to data, the mainstream price for Q345E seamless steel pipes with a diameter of 219mm × 10mm is 5200~5800 yuan/ton (October 2025), with prices significantly affected by iron ore fluctuations and downstream infrastructure investment.
Market competition is polarized: the high-end market is dominated by state-owned enterprises, whose products are used in special projects such as nuclear power and deep-sea oil and gas; small and medium-sized private enterprises compete for the civilian market through flexible pricing, but some enterprises are selling Q345B as Q345E, requiring verification of impact performance through third-party testing (such as SGS reports).
Fifth, Future Technological Development Directions for Q345E Hot-Rolled Seamless Steel Pipes
1. Green Manufacturing: Promote short-process electric arc furnace steelmaking to reduce carbon emissions, such as by adopting hydrogen reduction technology.
2. Performance Upgrade: Develop Q345E+ grade materials, using TMCP (controlled rolling and cooling) technology to increase yield strength to over 400MPa.
3. Intelligent Production: Apply AI vision inspection systems to monitor surface defects in real time, and optimize rolling parameters using big data.
Sixth, Recommendations for Purchasing and Using Q345E Hot-Rolled Seamless Steel Pipes
1. Qualification Verification: Require suppliers to provide material certificates and third-party testing reports, focusing on verifying the -40℃ impact energy data.
2. Corrosion Protection: For use in humid environments, epoxy coal tar coating or hot-dip galvanizing is recommended.
3. Welding Process: J507 welding rods are recommended. Preheating temperature should not be lower than 100℃, and interpass temperature should be controlled between 150~200℃.
Conclusion: Q345E hot-rolled seamless steel pipes, with their comprehensive performance advantages, are increasingly irreplaceable in harsh working conditions. With the advancement of infrastructure construction along the “Belt and Road” initiative and the explosive growth of the new energy industry, market demand for these pipes will continue to grow, while material innovation and process upgrades will further expand their application boundaries.
Post time: Nov-21-2025