What is the processing method for Q355B seamless square and rectangular steel pipes

First, what are the basic properties of Q355B seamless square and rectangular steel pipes?

(1) Material composition: Q355B is a low-alloy high-strength structural steel. Its chemical composition mainly includes elements such as carbon, silicon, manganese, phosphorus, and sulfur. The carbon content generally does not exceed 0.2%, the silicon content is about 0.5%, and the manganese content can reach about 1.6%. The presence of alloying elements effectively improves the strength and toughness of the steel pipe.

(2) Mechanical properties: The yield strength is not less than 355MPa, the tensile strength is usually between 470-630MPa, and the elongation is not less than 21%. These performance indicators enable Q355B seamless square and rectangular steel pipes to withstand large loads in many fields, such as construction and machinery, ensuring the stability and safety of the structure.

Second, what are the types and characteristics of Q355B seamless square and rectangular steel pipes?

(1) Welded square and rectangular steel pipes: These are made by rolling and welding steel strips or plates. Their production process is relatively simple, and the cost is low. Welded rectangular steel pipes have high dimensional accuracy and can be customized to meet specific needs, such as side length and wall thickness. They are widely used in applications where shape accuracy is critical, and the load-bearing pressure is not particularly high.

(2) Seamless rectangular steel pipes: These are made by piercing solid round steel to form a rough tube, which is then hot-rolled, cold-rolled, or cold-drawn. Seamless rectangular steel pipes have better strength and toughness and can withstand higher pressure. Because they have no internal welds, the stress distribution is more uniform under pressure, resulting in higher reliability. They are widely used in fields with extremely high requirements for steel pipe quality, such as petrochemicals and aerospace.

Third, what are the details of the processing technology for Q355B seamless rectangular steel pipes?

(1) Raw material preparation: Selecting suitable Q355B round steel billets is crucial, as the quality of the billets directly affects the quality of the seamless rectangular steel pipes. The billets must have no obvious surface defects, and their chemical composition must meet standard requirements.

(2) Piercing process: This is a key step in the production of seamless rectangular steel pipes. The round steel billet is heated to a suitable temperature, generally around 1200℃, and then pierced through a piercing mill to form a rough tube. During the piercing process, parameters such as piercing speed and mandrel pressure must be carefully controlled to ensure the quality of the rough tube.

(3) Hot rolling or cold rolling (drawing) process: Hot rolling involves heating the pierced rough tube and then rolling it in a rolling mill, processing it into a rectangular steel tube shape through multiple rolling passes. Cold rolling (drawing) involves stretching or extruding the rough tube at room temperature using dies, gradually deforming it into a rectangular steel tube. Cold rolling (drawing) produces steel tubes with higher precision, but it is more difficult to process and has a relatively higher cost.

(4) Finishing process: This includes cutting, straightening, and flaw detection. Cutting involves cutting the steel tube to a specified length; straightening corrects bending deformations that occur during processing; flaw detection uses ultrasonic and magnetic particle testing methods to check for internal defects in the steel tube, ensuring that the steel tube meets quality requirements.

Fourth, what are the application areas of Q355B seamless square and rectangular steel pipes?

(1) Construction industry: Used for structural supports and frames in buildings. For example, using Q355B seamless square and rectangular steel pipes in the column structure of high-rise buildings can effectively improve structural strength.

(2) Machinery manufacturing: As a raw material for mechanical parts, such as for manufacturing crane booms and supports for engineering machinery, its high strength and good processing performance can meet the requirements of machinery manufacturing.

(3) Automotive industry: Q355B seamless square and rectangular steel pipes are also used in some automotive frame and anti-collision bar structural components to improve the safety and stability of automobiles by utilizing their strength and toughness.

(4) Energy sector: Q355B seamless square and rectangular steel pipes are also used in supports for oil and natural gas pipelines and in some small pipeline systems to ensure structural stability during energy transmission.