C-section Steel Testing

C-section steel inspection mainly conducts scientific testing and analysis on the dimension and shape inspection, mechanical property testing, chemical composition analysis, surface quality and coating testing, and internal defect testing, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Dimension and shape inspection: Mainly measuring the section height (H), width (B), lip width (C), thickness (t) and length of the C-section steels. The precision measuring tools need to be used to check whether they meet the product standard or drawing tolerance requirements, for example, the deviations of the web heights and flange widths are strictly controlled. This is the basis of ensuring the subsequent installation and load-bearing performance.

Mechanical property testing: This is the key of evaluating the load-bearing capability of the C-section steels, mainly including the testing of the yield strengths, tensile strengths, elongations after fracture and bending properties. Through the tensile testing and bending testing, whether the material satisfies the design standards under the stressed states is verified. For the C-section steels used for the building structures, their yield strengths are the crucial safety indicators.

Chemical composition analysis: Through the means such as the spectroscopic analysis, the contents of the elements such as the carbon (C), silicon (Si), manganese (Mn), phosphorus (P) and sulfur (S) in the steel used for the C-section steels are determined. The compositions directly affect the weldability, cold bending property and final mechanical properties of the steel, and are the core basis of judging whether the material meets the corresponding designation standards (such as Q235 and Q355).

Surface quality and coating testing: Whether the C-section steel surfaces have the defects such as the cracks, scars, laps and pits is checked. For the galvanized C-section steels, the coating thicknesses (such as the double-sided zinc coating amounts), coating adhesion (such as the bending testing) and coating uniformity need to be tested, to ensure that their corrosion resistance reaches the expected service lives.

Internal defect testing: The non-destructive testing technologies are used to explore the potential hazards such as the lamination, inclusions and blowholes inside the material. The commonly used methods include the ultrasonic flaw detection. Through the probe movement on the section steel surfaces, the positions and sizes of the internal defects are judged according to the reflected echoes, ensuring the internal integrity of the material.

Testing Scope

Cold-formed C-section steels for the building structures: Widely applied to the secondary stressed components and enclosure structures such as the purlins and wall beams of the industrial and civil buildings. The testing needs to strictly follow the standards such as GB/T 6725-2017 (General technical delivery conditions for cold formed steel sections) and GB 50018-2002 (Technical code of cold-formed thin-wall steel structures), ensuring that their dimension precision and mechanical properties meet the building safety requirements.

C-section steels for the automotive and transportation applications: Used for the truck frame rails, carriage skeletons and railway freight car side beams. The testing emphases are the fatigue performance under the high strengths, impact toughness and strict dimension tolerances, to adapt to the complex dynamic load working conditions. The relevant testing needs to comply with the technical conditions of the automotive industry or specific transportation equipment.

C-section steels for the storage racks: As the main materials of the beams and columns, the testing focuses on the load-bearing capability, stiffness and reliability of the connection nodes. In addition to the routine mechanical properties, the specific load-bearing testing and stability analysis also need to be carried out, ensuring the safety and stability of the racks under the fully loaded conditions.

C-section steels for the mechanical equipment and supports: Used to manufacture the machine bases, supports and conveyor rails. In addition to the basic properties, the testing scope pays more attention to their shape precision such as the straightness and twist, as well as the corrosion resistance or wear resistance in the specific environments, to meet the requirements of the equipment installation and long-term operation.

Export and special certification requirements: For the C-section steels for the international markets or specific projects (such as the nuclear power and ocean engineering), the testing scope needs to be extended to meet the international standards (such as ASTM A1008 and EN 10162) or the special technical agreements specified by the customers, possibly including the stricter chemical composition control, third-party witnessed testing and comprehensive material traceability records.

Testing Methods

Dimension measurement method: The tools such as the vernier callipers, micrometers, tapes and radius gauges are used for the direct measurement. For the lengths, the laser distance meters or steel tapes are used; for the section dimensions, the multiple points are usually taken at the two ends and the middle of the section steels for the measurement, calculating the averages and ranges to evaluate their dimension uniformity.

Tensile testing method: According to GB/T 228.1-2021 (Metallic materials — Tensile testing — Part 1: Method of test at room temperature), the standard tensile specimens are made from the flanges or webs of the C-section steels, and are stretched at the specified rates on the universal material testing machines until the fracture, thereby obtaining the key data such as the yield strengths, tensile strengths and elongations after fracture.

Bending testing method: According to GB/T 232-2010 (Metallic materials — Bend test method), the specimens are bent around the mandrels of the specified diameters to the specified angles, and whether the outer sides of the bends have the cracks is checked. This method is used to evaluate the plastic deformation capability and cold bending processing property of the material, and is one of the mandatory testing items of the cold-formed section steels.

Spectroscopic analysis method: The direct-reading spectrometers or inductively coupled plasma optical emission spectrometers (ICP-OES) are used for the chemical composition analysis. After the sample surfaces are ground flat, the characteristic spectra are generated through the excitation, and compared with the standard spectral lines, the contents of the various elements are quickly and accurately quantitatively analysed. It is the common means of the process control and finished product acceptance.

Coating thickness measurement method: The magnetic thickness gauges are the main tools of measuring the coating thicknesses of the galvanized C-section steels. Based on the magnetic induction principle, the non-magnetic coating thicknesses on the ferromagnetic matrix materials are non-destructively measured. The multiple points need to be uniformly selected on the section steel surfaces for the measurement, to evaluate the average thicknesses and uniformity of the coatings.

Testing Standards

Domestic Standards:

1. GB/T 6725-2017, General technical delivery conditions for cold formed steel sections

2. GB 50018-2002, Technical code of cold-formed thin-wall steel structures

3. GB/T 228.1-2021, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

4. GB/T 232-2010, Metallic materials — Bend test method

International Standards:

1. ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

2. ASTM A1008, Standard specification for steel, sheet, cold-rolled, carbon, structural, high-strength low-alloy, high-strength low-alloy with improved formability, solution hardened, and bake hardenable

3. EN 10162, Cold rolled steel sections — Technical delivery conditions — Dimensional and cross-sectional tolerances

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Universal material testing machine: The core equipment of carrying out the mechanical property testing such as the tensile, bending and compression. The modern models are usually equipped with the computer control systems, which can automatically draw the stress-strain curves, precisely calculate the various mechanical property indicators and output the standardized test reports. The measuring ranges need to cover the expected strengths of the C-section steels to be tested.

Spectroscopic analyser: Used for the fast on-site or precise laboratory chemical composition analysis. The portable spectrometers are suitable for the fast incoming material screening and furnace-front analysis; the laboratory benchtop spectrometers provide the higher precision and lower detection limits, and are the key equipment of issuing the composition reports.

Ultrasonic flaw detector: The non-destructive testing equipment used to detect the internal defects of the C-section steels. Through the emission and reception of the ultrasonic waves by the piezoelectric transducers, the depths and sizes of the defects are judged according to the positions and amplitudes of the reflected echoes from the defect interfaces on the screens. It is crucial for ensuring the safety of the materials in the high-risk application fields.

Coating thickness gauge: Including the magnetic thickness gauges and eddy current thickness gauges. The magnetic thickness gauges are used to measure the non-magnetic coatings (such as the galvanized layers and paints) on the steel matrices; the eddy current thickness gauges are used to measure the insulating coatings on the non-ferrous metal matrices. The equipment needs to be regularly calibrated with the standard sheets to ensure the measurement accuracy.

Precision dimension measuring tools: Including the high-precision digital callipers (resolution 0.01mm), outer diameter micrometers, wall thickness micrometers, steel tapes, laser distance meters, as well as the platforms, feeler gauges and dial indicators used for measuring the straightness and flatness. The combined use of these tools can comprehensively evaluate the shape dimension precision of the C-section steels.