Water-stop Steel Plate Testing

Waterstop steel plate inspection mainly conducts scientific testing and analysis on the chemical composition analysis, mechanical property testing, dimension and shape inspection, surface quality inspection, corrosion resistance assessment, welding procedure qualification and weld 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

Chemical composition analysis: Through the methods such as the spectrometry analysis, the contents of the main and residual elements such as the carbon (C), silicon (Si), manganese (Mn), phosphorus (P) and sulphur (S) in the waterstop steel plate are precisely determined. The composition analysis is the basic testing item, directly affecting the weldability, processing performance and durability of the steel, ensuring that it meets the material designations required by the design, such as Q235B and Q345B.

Mechanical property testing: Mainly including the tensile testing, bending testing and impact testing. The tensile testing determines the yield strength, tensile strength and elongation after fracture, evaluating its load-bearing and deformation abilities; the bending testing inspects its cold bending performance, ensuring that no cracks are produced during the processing and installation; the impact testing (especially the low-temperature impact) evaluates its toughness in the cold environments, preventing the brittle fracture.

Dimension and shape inspection: The precision measuring tools (such as the vernier callipers, micrometers and steel tape measures) are used to measure the key dimensions such as the thickness, width, length and folded edge heights of the waterstop steel plate. At the same time, its flatness, straightness and bending angles are checked, ensuring that its geometric shapes meet the construction drawings and technical specification requirements, and guaranteeing the tightness of the on-site splicing and the installation precision.

Surface quality inspection: The plate surface is visually inspected or with the aid of the magnifying glasses, emphatically checking whether there are the defects such as the cracks, scars, folds, delaminations, rust and excessively thick oxide scales. The surface quality directly affects the waterstop effect and the bonding force with the concrete, and the serious surface defects may become the stress concentration points and corrosion initiation points, which must be strictly controlled.

Corrosion resistance assessment: For the waterstop steel plates with the special anti-corrosion requirements (such as the galvanized and plastic-coated), the salt spray testing, coating adhesion cross-cut testing and coating thickness testing need to be carried out. The uniformity, compactness and durability of their anti-corrosion layers are evaluated, ensuring that within the service life specified by the engineering design, the erosion of the corrosive media in the groundwater or soil can be effectively resisted.

Welding procedure qualification and weld testing: When the waterstop steel plates need to be lengthened by the on-site welding, the welding procedure needs to be qualified. The appearance inspection, non-destructive testing (such as the ultrasonic flaw detection) and mechanical property re-inspection are carried out on the welded joints, ensuring that the weld quality is equivalent to that of the base material, and guaranteeing the overall continuity and sealing reliability of the waterstop belt.

Testing Scope

Underground structures of the building engineering: Mainly used for the construction joints, post-pouring belts and deformation joints (settlement joints and expansion joints) of the basement bottom plates, external walls and roof plates. The testing needs to ensure that the steel plate can effectively block the water seepage paths after the concrete pouring. It is the key link of the underground waterproofing engineering, related to the durability and use safety of the building main structures.

Structures of the water conservancy and hydropower projects: Applied to the permanent joints and construction joints of the hydraulic structures such as the dams, sluices, pumping stations and water conveyance tunnels. The testing standards of this field are more stringent. In addition to the routine items, the performance stability and corrosion resistance under the long-term water pressures, dry-wet cycles and freeze-thaw environments need to be emphatically focused on.

Transportation tunnels and utility tunnel projects: Applicable to the circumferential construction joints and deformation joints of the underground linear projects such as the metros, highway and railway tunnels and utility tunnels. The testing needs to consider the complex stressed states such as the uneven settlement and lateral pressures of the tunnels, and puts forward the higher requirements for the toughness, fatigue resistance and connection reliability of the steel plate.

Municipal sewage treatment facilities: Used for the construction joints of the concrete tank bodies such as the sewage tanks, sedimentation tanks and regulating tanks. The testing needs to particularly focus on the chemical corrosion resistance of the steel plate in the environments containing the corrosive media such as the chloride ions and sulphate ions, as well as the material degradation under the long-term immersion.

Industrial buildings and special structures: Covering the containment vessels of the nuclear power plants, large storage tank foundations and anti-seepage structures of the important plants. This type of projects has the extremely high testing requirements for the waterstop steel plates, usually needing to follow the stricter special technical specifications, and carrying out the comprehensive material certification and life assessment.

Incoming inspection and finished product ex-factory inspection of the raw materials: The testing scope covers the steel plate raw materials provided by the steel mills, ensuring that their quality certificates are complete and the materials are qualified; it also includes the ex-factory inspection of the formed waterstop steel plates, checking their processing precision, surface treatment quality and packaging markings. It is the key step of the production quality control.

Testing Methods

Spectrometry analysis method: The direct-reading spectrometer or X-ray fluorescence spectrometer is adopted for the fast, non-destructive qualitative and quantitative analysis of the chemical compositions of the steel plate. This method has the high precision and fast speed, and is the preferred method of the raw material incoming acceptance and material re-inspection, effectively eliminating the risks of the material non-conformity or "passing off the inferior as the superior".

Universal material testing machine method: In accordance with the standards such as GB/T 228.1, the microcomputer-controlled universal testing machine is used to carry out the tensile and bending testing. The load-displacement curves are automatically acquired through the sensors and software systems, and the various mechanical property indicators are precisely calculated. It is the method of assessing the strength and plasticity of the material.

Pendulum impact testing method: On an impact testing machine, the Charpy V-notch specimens of the specified shapes and sizes are used to carry out the impact absorbed energy testing at the specific low temperatures (such as -20 ℃ and -40 ℃). By measuring the energy consumed by the specimen fracture, the toughness transition temperature and brittle fracture resistance of the steel are scientifically evaluated.

Ultrasonic thickness measurement and flaw detection method: The ultrasonic pulse reflection principle is used to measure the steel plate thickness, especially suitable for the thickness re-check of the coated or installed components. The ultrasonic flaw detection (UT) is used to detect the hidden defects such as the delaminations and slag inclusions inside the steel plate and the lack of fusion and blowholes inside the welds, ensuring the material integrity.

Salt spray testing method: The specimens with the anti-corrosion coatings are placed in a salt spray test chamber, simulating the marine or salt-containing damp atmospheric corrosion environments, and the spraying is continuously carried out for a certain period (such as 500 hours and 1000 hours). By observing the times and areas of the rust, blistering and peeling on the specimen surfaces, and comparing with the standard diagrams, the corrosion resistance grades are assessed.

Coating thickness gauge method: The magnetic thickness gauges (used for the non-magnetic coatings on the iron and steel substrates such as the galvanized layers and paints) or eddy current thickness gauges (used for the non-ferrous metal substrates) are adopted to fast and non-destructively measure the local thicknesses of the anti-corrosion coatings. Through the multi-point measurement, the average thicknesses and minimum thicknesses are calculated, judging whether the coating uniformity meets the standards.

Testing Standards

Domestic Standards:

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

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

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

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

5. GB/T 4340.1-2009, Metallic materials — Vickers 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 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

Direct-reading spectrometer: The core chemical composition analysis equipment. Through the arc or spark excitation of the sample to generate the characteristic spectra, which are received by the CCD detectors after the grating dispersion, and compared with the built-in standard curves, the contents of more than ten elements in the steel can be simultaneously determined within dozens of seconds, with the precise results. It is a powerful tool of the material identification.

Microcomputer-controlled electronic universal testing machine: The main equipment of the mechanical property testing. Equipped with the high-precision load cells, electronic extensometers and all-digital control systems, it can realize the various static mechanical tests such as the tensile, compression, bending and shear, with the automatic data processing and test report generation, meeting the high-precision testing requirements.

Pendulum impact testing machine: The dedicated equipment for evaluating the material toughness. Composed of the frame, pendulum, specimen supports and energy indication systems. During the testing, the pendulum is lifted to the specified height and released, and after breaking the specimen, the remaining energy is read, thereby calculating the impact absorbed energy. Equipped with the low-temperature baths, the impact testing at the different temperatures can be realized.

Ultrasonic flaw detector and thickness gauge: The portable non-destructive testing equipment. The flaw detector transmits and receives the ultrasonic waves through the probes, converts the signals into the waveform diagrams, and the technicians interpret the positions and sizes of the internal defects. The ultrasonic thickness gauge directly displays the thickness values in the digital form, with the simple operation, suitable for the fast on-site spot checks.

Salt spray corrosion test chamber: The artificial accelerated corrosion aging testing equipment. By atomizing the sodium chloride solution and uniformly depositing it on the specimen surfaces, a constant-temperature, constant-humidity and constant-concentration corrosive environment is created, which can greatly shorten the natural corrosion cycles and evaluate the long-term corrosion resistance of the coatings or materials in a relatively short time.

Coating thickness gauge and adhesion cross-cut tester: The common tools of the coating quality testing. The magnetic/eddy current thickness gauges are used for the fast measurement of the coating thicknesses. The adhesion cross-cut testers are equipped with the multi-blade cutting knives, which can cut the grid patterns on the coatings, and combined with the tapes for the pulling, the bonding strength with the substrate is assessed according to the coating peeling areas, with the simple and effective operation.