Industrial details of commonly used Q345B straight seam steel pipes

Introduction to Q345B straight seam steel pipes: All steel pipes produced by straight seam welding of strip steel and Q345B straight seam steel pipes on high-frequency welding equipment are called straight seam welded pipes Q345B straight seam steel pipes, which are currently widely used.

Q345B straight seam steel pipe production process:
1. Plate detection: After the steel plate used to manufacture large-diameter submerged arc welded straight seam steel pipe enters the production line, it is first subjected to full plate ultrasonic inspection;
2. Edge milling: The two edges of the steel plate are double-sided milled by the edge milling machine to achieve the required plate width, plate edge parallelism, and groove shape;
3. Pre-bending edge: The plate edge is pre-bent by the pre-bending machine so that the plate edge has the required curvature;
4. Forming: On the JCO forming machine, half of the pre-bent steel plate is first pressed into a "J" shape through multiple-step punching, and then the other half of the steel plate is bent in the same way to form a "C" shape, and then an open "O" shape is formed
5. Pre-welding: The formed straight seam welded steel pipe is seamed and continuously welded by gas-shielded welding (MAG);
6. Internal welding: The inner side of the straight seam steel pipe is welded by longitudinal multi-wire submerged arc welding (four wires at most);

Application fields of Q345B straight seam steel pipe:
Q345B straight seam steel pipe is widely used in the following industrial scenarios due to its excellent comprehensive performance (yield strength ≥345MPa, good weldability, and cost advantage):
1. Building and bridge engineering
Steel structure buildings: high-rise building columns, roof trusses, industrial plant support structures.
Bridge components: main beams, pier support pipes, anti-corrosion coating base pipes for cross-sea bridges (need to be galvanized or painted).
2. Energy transmission pipelines
Oil and gas transportation: land and shallow sea oil and gas gathering and transmission pipelines, medium and low-pressure scenarios with working pressure ≤10MPa.
Water conservancy projects: water pipes and drainage pipes, especially suitable for underground laying (epoxy coal tar anti-corrosion is required).
Heat pipe network: urban centralized heating pipelines, temperature range -20℃~350℃.
3. Machinery manufacturing and equipment
Engineering machinery: crane boom, excavator chassis structure pipe.
Vehicle manufacturing: Truck chassis longitudinal beams, trailer frames, lightweight design and strength.
Agricultural machinery: Combine harvester frames and irrigation equipment support pipes.
4. Infrastructure and municipal engineering
Pile foundation pipes: Building foundation pit support piles, and wharf steel pipe piles (wall thickness can reach more than 20mm).
Street light poles/signal poles: Processed by cold bending forming process, surface hot dip galvanizing.
Urban pipe gallery: Comprehensive pipe gallery support system, used with fire retardant coating.
5. Special industry applications
Wind power tower: used for tower sections in low wind speed areas, by NB/T 31001 standard.
Mine support: Tunnel support steel pipes, high compressive strength, and easy underground welding.
Temporary structures: Scaffolding, and construction platform support pipes, can be disassembled and used repeatedly.


Selection recommendations
High-pressure scenario: If the working pressure is >15MPa or the medium is highly corrosive, it is recommended to upgrade to L245N or alloy steel pipes.
Cost optimization: Compared with Q420 steel, Q345B is more cost-effective and suitable for conventional load projects.
Anti-corrosion requirements: "3PE anti-corrosion" or "epoxy powder coating" is required in humid/coastal environments to extend service life.