H-beam Steel Material Testing

H-section steel material inspection mainly conducts scientific testing and analysis on the dimension and shape testing, tensile property testing, impact toughness, bending property testing, chemical composition analysis and surface quality and appearance inspection, 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 testing: This is the basic item of the H-section steel inspection, mainly carried out according to the product standards such as GB/T 11263. The testing contents include the heights, flange widths, web thicknesses, flange thicknesses, flange slope, straightness, twist and end face bevel cutting degrees, etc. These dimension parameters directly determine the section characteristics and load-bearing capacity of the section steel, and are the primary indicators of judging whether the product is qualified.

Tensile property testing: Used to evaluate the mechanical properties of the H-section steel under the uniaxial tension. The main indicators include the yield strength, tensile strength, elongation after fracture and reduction of area. These data are the core basis of the structural design, strength verification and safety evaluation, usually completed on the universal material testing machines according to the GB/T 228.1 standard.

Impact toughness (Charpy impact testing): This testing is used to evaluate the ability of the H-section steel to resist the brittle fracture under the dynamic loads or low-temperature environments. Usually adopting the V-notch specimens, the impact absorbed energy is determined at the specific temperatures (such as 0℃ and -20℃). This is crucial for the structures in the cold regions or bearing the dynamic loads (such as the bridges and crane beams), following the GB/T 229 standard.

Bending property testing: Mainly used to evaluate the process plasticity of the H-section steel, that is, its ability to bear the bending deformations without the cracks. According to the standard GB/T 232, the specimens are bent to the specified angles through the mandrels of the specified diameters, and whether there are the cracks, laminations or fractures on the bending outer surfaces is checked, to judge whether its cold bending properties are qualified.

Chemical composition analysis: The qualitative and quantitative analysis of the H-section steel material is carried out, mainly testing the contents of the five major elements carbon, silicon, manganese, phosphorus and sulfur, as well as the alloying elements such as the chromium, nickel and vanadium with the special performance requirements. The chemical compositions are the root of determining the mechanical properties, weldability and durability of the steel. The testing methods include the spectroscopic analysis and carbon-sulfur analysis, etc., and need to meet the standards such as GB/T 4336.

Surface quality and appearance inspection: Through the visual inspection or with the aid of the tools such as the gauges and magnifying glasses, whether the H-section steel surfaces have the defects such as the cracks, scars, folds, inclusions and delaminations, as well as the rust and pits is checked. The surface defects may become the stress concentration points, affecting the safety and service lives of the structures.

Testing Scope

Classification by product standards: Mainly covering the hot-rolled H-section steels, some T-section steels and welded H-section steels. The hot-rolled H-section steels are divided into the wide, medium and narrow flange series according to GB/T 11263; the welded H-section steels need to simultaneously meet the steel base material standards and welding process qualification standards, such as JG/T 137.

Classification by steel designations and grades: The testing scope covers the widely used Q235 and Q355 series carbon structural steels and low-alloy high-strength steels. At the same time, the high-strength grade steels commonly used for the high-rise buildings and large-span structures such as Q390, Q420 and Q460, as well as the steel designations with the special properties such as the weather resistance and fire resistance, are also included.

Classification by application fields: The testing serves the different fields such as the industrial and civil buildings (factories and high-rise buildings), bridge engineering, offshore platforms, port machinery and power transmission towers. The different fields have the focused requirements for the properties of the H-section steel (such as the seismic resistance, low-temperature resistance and corrosion resistance), and the testing items need to be adjusted accordingly.

Classification by production and circulation links: The testing runs through the whole life cycle links such as the raw material incoming re-inspection, production process quality control, finished product ex-factory inspection, third-party type inspection, engineering site sampling re-inspection and regular safety evaluation in use, ensuring that the material quality is always controllable.

Classification by mechanical property states: The testing objects include the H-section steels in the routine hot-rolled states, controlled rolling and controlled cooling states (TMCP), as well as the heat treatment states such as the normalized and tempered. The micro-structures and properties in the different states differ significantly, and the testing methods and judgement standards need to be distinguished.

Special requirement testing: For the applications with the special requirements, the testing scope also includes the special contents such as the Z-direction (through-thickness) properties (preventing the lamellar tearing), fatigue properties, residual stress testing, non-destructive flaw detection (such as the ultrasonic testing of the internal defects) and fire resistance testing.

Testing Methods

Dimension measurement method: The high-precision callipers, micrometers, depth gauges, R gauges, right-angle rulers and feeler gauges are used for the manual measurement. For the large batches or high-precision requirements, the non-contact automatic measurement systems such as the laser scanners and image measuring instruments can be adopted to quickly obtain the complete cross-section profile dimension data.

Tensile testing method: Strictly carried out according to GB/T 228.1. The proportional or non-proportional specimens are taken from the flange legs or webs in the specified directions, and the tensile forces are applied at the specified strain rates or stress rates on the microcomputer-controlled electronic universal testing machines. The data are automatically recorded through the force-displacement transducers, and the various strength and plasticity indicators are calculated.

Impact testing method: According to GB/T 229, the samples are taken from the products and machined into the standard Charpy V-notch impact specimens. The specimens are placed in the low-temperature baths of the impact testing machines, cooled to the specified temperatures and maintained, then quickly moved between the anvils and broken by the pendulums at one time, and the impact absorbed energy values are directly read by the testing machines.

Bending testing method: According to GB/T 232, the rectangular cross-section specimens are placed on two parallel support rollers, and the concentrated forces are applied at the middles of the specimens through the mandrel indenters of the specified diameters, making them slowly bend to the specified angles (such as 180°). After the testing, whether there are the cracks visible to the naked eyes on the bending outer sides of the specimens is checked.

Chemical composition analysis method: The spark discharge atomic emission spectrometry (OES) is the mainstream fast method. The specimens are used as the electrodes to excite the spectra for the quantitative analysis. The infrared absorption method is often used for the precise determination of the carbon and sulfur. In addition, the inductively coupled plasma atomic emission spectrometry (ICP-OES) is used for the multi-element simultaneous analysis, and the titration method and photometric method are used as the arbitration or verification methods.

Non-destructive testing method: The ultrasonic testing (UT) is used to probe the internal defects such as the delaminations, inclusions and holes; the magnetic particle testing (MT) or penetrant testing (PT) is used to detect the fine surface and near-surface cracks. These methods do not destroy the material, and are often used for the comprehensive quality screening of the H-section steel for the important structures.

Testing Standards

Domestic Standards:

1. GB/T 11263, Hot-rolled H and cut T section steel

2. JG/T 137, Structural welding H-section steel

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

4. GB/T 229-2020, Metallic materials — Charpy pendulum impact test method

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

6. GB/T 4336, Carbon and medium-low alloy steel — Determination of multi-element contents — Spark discharge atomic emission spectrometric method

7. GB/T 230.1-2018, Metallic materials — Rockwell hardness test — Part 1: Test method

International Standards:

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

2. ISO 148-1, Metallic materials — Charpy pendulum impact test — Part 1: Test method

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 mechanical property testing equipment, used to carry out the static mechanical testing such as the tensile, compression and bending. The modern models are mostly the microcomputer-controlled electro-hydraulic servo or electronic types, equipped with the high-precision load transducers and displacement extensometers, which can automatically draw the stress-strain curves and output the test reports.

Pendulum impact testing machine: The dedicated equipment of determining the impact toughness of the metal materials. The key components include the liftable pendulums, specimen supports, energy indicating mechanisms and safety protection devices. The equipment needs to be equipped with the auxiliary devices such as the low-temperature baths or impact specimen notch projectors, to ensure the accuracy of the test conditions and the reliability of the result interpretation.

Spectrometer: The core instrument of the fast quantitative chemical composition analysis. The direct-reading spectrometers excite the samples through the arc or spark and analyse the generated characteristic spectra, which can simultaneously determine the contents of the various elements in the steel within tens of seconds. The equipment needs to be regularly calibrated with the reference materials to ensure the analysis precision.

High-precision dimension measurement system: Including the traditional manual gauges such as the vernier callipers, outer diameter micrometers and universal angle rulers, as well as the modern laser three-dimensional scanners and optical image measuring instruments. The latter adopts the non-contact measurement, which can quickly reconstruct the three-dimensional models of the H-section steel cross-sections and automatically calculate all the key dimensions and geometric tolerances.

Metallographic microscope and sample preparation equipment: Used to observe and analyse the micro-structures of the H-section steel, evaluating the grain sizes, non-metallic inclusion grades and decarburized layer depths. The system includes the cutting machines, mounting machines, grinding and polishing machines, etching devices, as well as the digital metallographic microscopes with the image analysis software.

Non-destructive testing equipment: The ultrasonic flaw detectors are the main tools of detecting the internal defects, judging the defect positions and sizes by transmitting and receiving the ultrasonic signals through the probes. The magnetic particle flaw detectors magnetize the workpieces and apply the magnetic particles to display the surface defects. The probes, couplants and sensitivity test blocks of these equipment all need to meet the relevant standard requirements.

Hardness tester: Used for the fast evaluation of the hardness of the H-section steel surfaces or local areas, indirectly reflecting their strengths. The common ones include the Brinell hardness testers (HBW, suitable for the coarser structures), Rockwell hardness testers (HRB/HRC) and portable Leeb hardness testers. The different hardness values can be approximately converted through the conversion tables.