Corrugated Steel Plate Testing

Corrugated steel plate inspection mainly conducts scientific testing and analysis on the geometric dimension inspection, yield strength and tensile strength testing, coating quality and adhesion testing, surface quality and appearance inspection, coating performance testing and chemical composition analysis, 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

Geometric dimension inspection: Precisely measures the corrugation height, corrugation pitch, effective width, thickness and length of the corrugated steel plate. This is the basis for ensuring that the plate can be correctly installed, connected and achieve the expected structural performance. The testing needs to use the high-precision measuring tools, and the multi-point measurements need to be carried out at the different positions of the plate, to evaluate its dimensional uniformity.

Yield strength and tensile strength testing: Through a tensile testing machine, the specimens cut from the corrugated steel plate are subjected to the tensile testing, determining their yield strength (ReH/ReL) and tensile strength (Rm). These data are the core mechanical indicators for evaluating the load-bearing capacity and structural safety of the corrugated steel plate, directly related to its deformation and failure limits under the loads.

Coating quality and adhesion testing: For the galvanized or galvalume corrugated steel plates, the coating thickness, uniformity and adhesion need to be detected. The common methods include the magnetic thickness measurement method, hammering testing and bending testing. The coating quality directly affects the corrosion resistance life of the corrugated steel plate, and is the key to evaluating its durability.

Surface quality and appearance inspection: Through the visual inspection or with the aid of the tools, it is checked whether there are the defects affecting the use on the corrugated steel plate surface, such as the cracks, scars, corrosion, missed coating, scratches and irregular corrugation shapes. Although the appearance inspection is simple, it is crucial for guaranteeing the overall product quality and the engineering aesthetics.

Coating performance testing (if applicable): For the corrugated steel plates with the colour coatings or special anti-corrosion coatings, the coating thickness, gloss, colour difference, flexibility, impact resistance, salt spray resistance and weather resistance need to be detected. These items evaluate the protection effects and appearance retention abilities of the coatings under the long-term outdoor environments.

Chemical composition analysis: Through the methods such as the spectrometry analysis, the chemical composition of the corrugated steel plate substrate, such as the contents of the elements including the carbon (C), silicon (Si), manganese (Mn), phosphorus (P) and sulphur (S), is determined. The chemical composition directly affects the mechanical properties, welding performance and corrosion resistance of the steel, and is one of the bases for the material conformity judgement.

Testing Scope

Support structures of the highway and railway culverts and tunnels: The corrugated steel plates used to form the culvert arch structures or the initial supports of the tunnels. The testing emphasis is on their ring stiffness, load-bearing capacity, connector strength and the long-term resistance to the groundwater and soil corrosion, ensuring the safety and durability of the underground structures.

Municipal utility tunnels and underground storage: The corrugated steel plate components applied to the prefabricated assembled utility tunnels or large underground storage facilities. The testing needs to focus on their dimensional precision, sealing performance, resistance to the external pressure stability and the performance of the fire-retardant coatings (if required).

Building envelope systems: The colour-coated corrugated steel plates used as the building exterior wall panels and roof panels. The testing scope focuses on the decoration, weather resistance, wind uplift resistance, thermal insulation performance of the coatings and the compatibility with the supporting connectors.

Water conservancy projects and river slope protection: The corrugated steel plates used to make the flood control walls, river bank revetments and drainage channels. The testing needs to emphatically evaluate their corrosion resistance and structural integrity under the harsh environments such as the dry-wet alternation, water flow scouring and freeze-thaw cycles.

Temporary works and movable structures: Such as the corrugated steel plates used for the construction temporary bridges, emergency passages and temporary warehouses. The testing focuses on the lightweight, rapid installation, reusability of the material and the mechanical properties meeting the safety standards of the temporary structures.

Raw materials and semi-finished products: The incoming inspection of the steel coils (strips) used to produce the corrugated steel plates is carried out, including their mechanical properties, coating quality and dimensions. At the same time, the process inspection of the formed corrugated steel plate semi-finished products is carried out, ensuring the production consistency.

Testing Methods

Mechanical property testing method: In accordance with the standards such as GB/T 228.1, the tensile testing is carried out on a universal material testing machine, obtaining the yield strength, tensile strength and elongation after fracture. For the structural corrugated steel plates, the bending testing (GB/T 232) may also be needed to evaluate their cold bending properties.

Geometric dimension measurement method: The tools such as the steel tape measures, vernier callipers, micrometers, depth gauges and templates are used to directly measure the various external dimensions of the corrugated steel plate according to the product standards (such as GB/T 12755). For the large-size plates, the method of taking the average values of the multi-point measurements needs to be adopted.

Coating testing method: The coating thickness is usually non-destructively measured with the magnetic method (GB/T 4956) or eddy current method (GB/T 4957). The coating adhesion is rated through the hammering testing or bending testing (bending the specimen to the specified angle and observing whether the coating peels off).

Chemical analysis method: The spark discharge atomic emission spectrometry (GB/T 4336) or inductively coupled plasma atomic emission spectrometry (ICP-OES) is adopted for the fast and precise quantitative analysis of the steel composition. The equipment such as the carbon-sulphur analysers can also be used for the special determination of the specific elements.

Coating performance testing method: The coating thickness is measured with the eddy current thickness gauges; the adhesion is commonly tested with the cross-cut method (GB/T 9286); the impact resistance is tested with the impact testers (GB/T 1732); the salt spray resistance is tested through the accelerated corrosion testing in the salt spray test chambers (GB/T 10125).

Non-destructive testing method: For the important structural parts, the ultrasonic flaw detection (UT) can be adopted to detect whether there are the defects such as the delaminations and inclusions inside the plate; or the penetrant flaw detection (PT) can be adopted to detect the fine cracks open to the surface, ensuring the internal quality of the material.

Testing Standards

Domestic Standards:

1. GB/T 12755, Profiled steel sheets for building

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

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

4. GB/T 4956, Non-magnetic coatings on magnetic substrates — Measurement of coating thickness — Magnetic method

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

6. GB/T 1732, Determination of impact resistance of film

7. GB/T 9286, Paints and varnishes — Cross-cut test

8. GB/T 10125-2021, Corrosion tests in artificial atmospheres — Salt spray tests

International Standards:

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

2. ISO 9227, Corrosion tests in artificial atmospheres — Salt spray tests

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 for carrying out the mechanical property tests such as the tensile, bending and compression of the corrugated steel plate. Its precision grade needs to meet the standard requirements, and it is equipped with the corresponding fixtures and extensometers, which can automatically draw the stress-strain curves and calculate the various mechanical parameters.

Coating thickness gauge: Divided into the magnetic thickness gauges (used to measure the thicknesses of the non-magnetic coatings such as the zinc and chromium on the steel substrates) and eddy current thickness gauges (used to measure the thicknesses of the insulating coatings on the non-conductive substrates or the non-conductive coatings on the conductive substrates). The instruments need to be regularly calibrated with the standard foils.

Spectrometer: The equipment for the fast chemical composition analysis of the metal materials. The direct-reading optical emission spectrometer can analyse the contents of the multiple elements in the sample within a few seconds, with the high precision. It is the key equipment for the incoming inspection and product identification of the steel materials.

Salt spray test chamber: The accelerated corrosion testing equipment simulating the marine or industrial atmospheric environments. By placing the corrugated steel plate specimens in an enclosed chamber with the constant temperature and humidity and the continuous spraying of the sodium chloride solution, the corrosion resistance and failure times of their coatings or layers are evaluated.

Dimension measuring tool set: Including the high-precision large vernier callipers, outer diameter micrometers, plate thickness micrometers, radius templates, dedicated callipers for the corrugation heights and pitches, steel tape measures and laser range finders. These tools need to be verified and qualified by the metrological verification, and used within the validity periods.

Coating performance testing instruments: Including the cross-cut testers and tapes (for the cross-cut method adhesion testing); impact testers (for evaluating the deformation and cracking resistance of the coatings); gloss meters and colour difference meters (for evaluating the coating appearances); as well as the series of dedicated tools such as the cross-cut knives and pencil hardness testers.