Q390D hot-rolled seamless steel pipe, as a high-strength low-alloy structural steel material, plays an important role in the industrial field. With its excellent mechanical properties, good weldability, and weather resistance, Q390D hot-rolled seamless steel pipe is widely used in bridge construction, engineering machinery, high-pressure vessels, and various heavy steel structures.
First, the material characteristics and performance advantages of Q390D hot-rolled seamless steel pipe.
Q390D belongs to the low-alloy high-strength structural steel category in GB/T1591 standard. The letter “D” indicates its low-temperature impact toughness at -20℃. Its chemical composition incorporates appropriate amounts of alloying elements such as manganese, silicon, vanadium, and niobium. Through solid solution strengthening and fine-grain strengthening mechanisms, the material significantly improves its strength while maintaining good ductility and toughness. Typical mechanical properties are: yield strength ≥390MPa, tensile strength 510-670MPa, elongation ≥18%, and impact energy at -20℃ ≥34J. Compared to ordinary Q235B steel pipes, Q390D exhibits approximately 66% higher yield strength and can reduce weight by 20%-30% under the same load-bearing requirements, significantly lowering structural weight and material costs. The hot-rolling process endows this product with unique microstructure characteristics. By controlling the rolling temperature and deformation, a fine ferrite-pearlite structure can be obtained, with grain size typically reaching level 8 or higher. This uniform and dense metallographic structure not only ensures matrix strength but also significantly improves the material’s resistance to lamellar tearing. Particularly noteworthy is that after Q390D undergoes controlled rolling and controlled cooling (TMCP) processing, the softening tendency of its weld heat-affected zone is significantly reduced, which is crucial for engineering structures requiring extensive welding operations.
Second, the production process and key technologies of Q390D hot-rolled seamless steel pipes.
The production of high-quality Q390D hot-rolled seamless steel pipes involves multiple precision-controlled processes. First, the material is smelted in a converter or electric arc furnace, followed by LF ladle refining and VD vacuum degassing to control the sulfur and phosphorus contents to below 0.025% and 0.035% respectively, and the hydrogen content to ≤2ppm, ensuring material purity from the source. Electromagnetic stirring technology is used during continuous casting to effectively reduce center segregation. After surface grinding, the billet enters the rolling process. Hot rolling production lines typically include key equipment such as ring furnaces, piercing mills, continuous rolling mills, and sizing mills. The billet is heated to approximately 1200℃, formed into a tube by a two-roll conical piercing mill, and then extended and deformed by a 5-7 stand continuous rolling mill. The core of process control lies in maintaining the final rolling temperature within the range of 850-880℃, followed by accelerated cooling at a rate of 5-15℃/s to promote the transformation of austenite into fine ferrite. This controlled rolling and cooling process can omit subsequent heat treatment processes, directly obtaining the required mechanical properties. Quality inspection includes multiple stringent indicators. In addition to routine dimensional tolerance checks, ultrasonic testing (compliant with GB/T5777 standard), hydrostatic testing (test pressure calculated according to standard formula), and comprehensive mechanical property testing are required. Higher-level orders often require additional NDT testing, hardness testing, and grain size rating. It is worth noting that some suppliers on the 1688 platform provide product descriptions indicating that their steel pipe ellipticity is controlled within ±1.0%D and wall thickness deviation does not exceed ±12.5%S; these parameters directly affect the assembly accuracy and safety of the pipes.
Third, Typical Application Scenarios of Q390D Hot-Rolled Seamless Steel Pipes.
In bridge engineering, Q390D hot-rolled seamless steel pipes are mainly used in the chords of long-span arch bridges, compression components of truss bridges, and pier support systems.
The construction machinery industry is another important application market for this product. Key load-bearing components such as concrete pump truck booms and crane booms commonly use Q390D material; through optimized design, the working radius of the equipment can be increased by 10%-20%.
In petrochemical equipment manufacturing, Q390D is commonly used in high-pressure heat exchanger tube bundles, reactor skirts, and other components. Compared to austenitic stainless steel, its coefficient of thermal expansion is closer to that of carbon steel shells, effectively reducing thermal stress.
Fourth, Procurement Recommendations and Market Status of Q390D Hot-Rolled Seamless Steel Pipes.
When purchasing Q390D hot-rolled seamless steel pipes, several key factors should be considered. First, verify the manufacturer’s special equipment manufacturing license (Class A certification for pressure piping components) and the mechanical performance report issued by a third-party testing agency. Depending on the application scenario, the impact test temperature (usually -20℃ or -40℃) and sample orientation (transverse or longitudinal) must be specifically confirmed. Regarding price, current market conditions show that Q390D hot-rolled seamless steel pipes are approximately 15%-20% more expensive than Q345B products of the same specifications. Taking φ273×10mm steel as an example, the reference price in October 2025 was approximately RMB 5800-6200/ton (including tax). The specific price is affected by factors such as raw material fluctuations, order volume, and transportation distance. Large-volume purchases (50 tons or more) typically enjoy a 3%-5% discount. It is worth noting that some suppliers offer “material storage” services, allowing users to pick up goods in batches according to the construction progress, effectively reducing warehousing costs.
For quality verification, the following procedures are recommended: check whether the steel grade, specifications, and applicable standards printed on the ends of the steel pipes are clear and complete; use calipers to measure the actual wall thickness deviation; and request the supplier to provide a complete quality certificate (including chemical analysis, mechanical properties, non-destructive testing data, etc.). For critical engineering applications, third-party re-inspection can be considered, focusing on verifying impact toughness and Z-axis performance. Market feedback indicates that the pass rate of products from major steel mills in Shandong and Jiangsu is relatively stable. While products from smaller steel mills are about 10% cheaper, there is a risk of large fluctuations in composition and unstable performance.
Fifth, Precautions for the Use and Maintenance of Q390D Hot-Rolled Seamless Steel Pipes
The processing of Q390D hot-rolled seamless steel pipes must follow specific process specifications. During cold bending, the bending radius should not be less than 3 times the pipe diameter, and the hot bending heating temperature should be controlled within the range of 900-950℃. Before welding, thoroughly remove oil and rust from the bevel and within 20mm on both sides. E5515-G type low-hydrogen welding rods are recommended, with a preheating temperature not lower than 120℃ and an interpass temperature controlled between 150-250℃. For welding thick-walled pipes (≥25mm), post-weld heat treatment at 250-350℃ should be performed immediately after welding. When used in corrosive environments, additional protective measures are recommended. Steel pipes used in coastal areas should preferably use a thermal spray aluminum composite coating (thickness ≥150μm), while epoxy coal tar anti-corrosion systems can be used in industrial atmospheric environments. During regular maintenance, special attention should be paid to checking stress concentration areas at the pipe connections; if surface cracks are found to be deeper than 0.5mm, they should be repaired promptly. During storage, contact with substances high in chloride ions (such as de-icing agents) should be avoided. Stacking height should not exceed 2 meters, and layers should be separated by wooden strips.
With the advancement of the “dual-carbon” strategy, Q390D hot-rolled seamless steel pipes are increasingly widely used in new energy fields such as wind turbine towers and photovoltaic supports. After using Q390D hot-rolled seamless steel pipes to manufacture the tower of a 2.5MW wind turbine, compared to the traditional Q345 material solution, the steel consumption per unit can be reduced by approximately 8 tons, and the carbon emissions over the entire life cycle can be reduced by 12%. In the future, with the continuous optimization of the TMCP process and the application of composite micro-alloying technology, the performance of the Q390D series products will be further improved, providing better material solutions for modern industrial construction.
Post time: Nov-17-2025