Description
Steel Rectangular Profile Pipes are hollow closed-section profiles in the shape of a rectangle, manufactured by forming and welding from steel strip. Due to high rigidity and rational cross-sectional shape, they are widely used in construction and mechanical engineering.
Production Technology

The manufacturing process includes the following key stages:
1.    Strip Preparation: Steel strip (skelp) is uncoiled, aligned, and cleaned.
2.    Forming: In successive stands, the strip is gradually bent, forming a closed round cross-section.
3.    Welding: The longitudinal edges are reliably joined by one of the methods:
o    HF Welding (high-frequency currents) – the most common method.
o    Arc Welding in inert gases (TIG, Plasma) – for high-quality welds.
o    Laser Welding – for precision profiles.
4.    Profiling into a Rectangle: The round pipe blank passes through special rolls, which give it the final rectangular shape.
5.    Calibration and Cooling: Precise sizing, cooling, and straightening.
6.    Cutting and Control: Cutting to measured lengths, visual and instrumental quality control.

Characteristics and Assortment
•    Cross-Section Sizes (height x width): from 15x10 mm to 500x400 mm.
•    Wall Thickness: from 0.8 mm to 20 mm.
•    Length: measured (6-12 m) and non-measured.
•    Steel Grades: carbon (St3sp), low-alloy (09G2S), stainless (AISI 304).
•    Accuracy Classes: increased and ordinary.
•    Production Methods: hot-deformed, cold-deformed, electric-welded.

Advantages
•    High Bending Rigidity in two planes, ensuring excellent load-bearing capacity.
•    Easy Installation and Joining with flat surfaces.
•    Aesthetic Appearance and compactness of structures.
•    Metal Savings compared to solid profiles.
•    Versatility and Processability of processing (cutting, welding, drilling).
•    Lower Weight of structures compared to square pipes with equal strength in one of the planes.

Areas of Application
•    Construction: building frames, trade pavilions, trusses, floors.
•    Mechanical Engineering: equipment frames, guides, housings, conveyors.
•    Automotive and Railcar Manufacturing: body elements, load-bearing frames.
•    Furniture Manufacturing: office and outdoor furniture frames, shelving.
•    Advertising Structures: billboard bases, lightboxes, signs.
•    Agriculture: greenhouse structures, livestock complexes.

Normative Documentation (GOST Standards)
Main standards regulating the production of rectangular profile pipes:
GOST 8645-68 – "Steel rectangular pipes. Assortment"
•    Establishes the full assortment of cross-section sizes and wall thicknesses.
•    Defines limit deviations for geometry (dimensions, straightness, twist).
•    Indicates the theoretical mass of 1 meter of pipe.
GOST 13663-86 – "Steel profile pipes. General technical specifications"
•    Defines general technical requirements for profile pipes.
•    Establishes steel grades, mechanical properties, test methods.
•    Regulates acceptance, marking, packaging rules.
Additional Standards:
•    GOST 10705-80 / GOST 10706 – Requirements for electric-welded pipes (as a blank).
•    GOST 5632-2014 – For stainless steels.
•    GOST 19281-2014 – For pipes made of high-strength steel.