First, details of Q390D straight seam steel pipes
Q390D straight seam steel pipes are steel pipes made using straight seam welding technology. Their main differences lie in the specific processing details and uses, but in general, they all have high strength, good toughness, and welding performance.
(1) Characteristics of Q390D straight seam steel pipes:
- High strength: Q390D steel pipes have high yield strength and tensile strength, allowing the manufactured steel pipes to withstand greater pressure and load.
- Good toughness: Q390D steel pipes have good toughness, making them less likely to break when subjected to impact or vibration.
- Excellent welding performance: Q390D steel pipes are easy to weld, and the welded joints are high in strength, which can meet the needs of various complex engineering structures.
(2) Applications of Q390D straight seam steel pipes:
- Building structures: Q390D straight seam steel pipes and straight seam pipes can be used for the support and load-bearing parts of building structures such as high-rise buildings and large public facilities.
- Bridge engineering: Due to their high strength and good welding performance, they are often used in key parts such as the main beam and cross beam of bridges.
- Machinery manufacturing: In the field of machinery manufacturing, they can be used to make parts of various equipment, such as transmission shafts, hydraulic cylinders, etc.

Second, Q390D straight seam steel pipe processing
The processing of Q390D steel pipe includes raw material preparation, smelting, refining, continuous casting, heating, rolling, controlled cooling, heat treatment (as needed), surface treatment, and quality inspection. The following are the specific processing steps:
- Raw material preparation: Select high-quality pig iron, scrap steel, etc. as raw materials, and conduct strict composition testing and screening to ensure that the raw materials meet the composition requirements of Q390D steel pipes.
- Smelting: Smelting is carried out in a converter or electric furnace, and the temperature and chemical reaction in the furnace are adjusted by controlling the input of oxygen, electricity, etc., removing impurities, and accurately controlling the chemical composition of the molten steel.
- Refining: Use the refining process outside the furnace, such as LF furnace (ladle refining furnace), RH furnace (vacuum cycle degassing refining furnace), etc., to further purify the molten steel, fine-tune the composition, uniform the temperature and composition, and improve the purity of the steel.
- Continuous casting: The refined molten steel is injected into the continuous casting machine and cast into slabs. During the continuous casting process, the cooling rate and the billet drawing speed are controlled to obtain good billet quality and internal structure.
- Heating: The slab is placed in the heating furnace and heated to a suitable temperature for the subsequent rolling process.
- Rolling: The hot rolling process is adopted, and after multiple passes of rolling, the thickness of the slab is gradually reduced, and the structure and performance of the steel pipe are improved.
- Controlled cooling: After rolling is completed, the steel pipe is cooled to room temperature at an appropriate cooling rate by controlling the cooling system, such as laminar cooling, gas mist cooling, etc., so as to obtain the required microstructure and mechanical properties.
- Heat treatment (as needed): Heat treatment processes such as normalizing and tempering may be carried out to further optimize the performance and structure of the steel pipe.
- Surface treatment: The steel pipe is subjected to surface treatment such as pickling and shot blasting to remove oxide scale and surface defects and improve surface quality.
- Quality inspection: The quality of the steel pipe is comprehensively inspected by non-destructive testing (such as ultrasonic testing, magnetic particle testing, etc.) and mechanical property testing (tensile test, impact test, etc.) to ensure that it meets the standards and requirements of Q390D steel pipe.

Third, the processing characteristics of Q390D straight seam steel pipe
(1) Straight seam welding process: Q390D straight seam steel pipe is made by the straight seam welding process, and the weld is in the longitudinal position of the steel pipe. This welding method has the advantages of high production efficiency and stable weld quality.
(2) High-precision processing: During the processing, advanced cutting, bending, welding, and surface treatment technologies are used to achieve high-precision processing of Q390D steel pipes to meet the needs of various complex engineering structures.
(3) Excellent performance: After the above processing, the Q390D straight seam steel pipe has high strength, good toughness, and welding performance, and can meet the use requirements under various high-strength and complex stress conditions.

In summary, the processing of Q390D steel pipe involves multiple links, and the process parameters and quality requirements of each link need to be strictly controlled. Through advanced processing technology and strict quality control, Q390D steel pipe products with excellent performance can be produced to meet the needs of various engineering structures.