Perforated Steel Plate Testing

Perforated steel plate inspection mainly conducts scientific testing and analysis on the hole diameter and hole spacing, hole shape and burr, plate thickness and flatness, material and mechanical properties, surface quality and coating, and opening rate calculation and verification, 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

Hole diameter and hole spacing: This is the most basic appearance geometric dimension testing item of the perforated steel plate. The precision callipers, hole gauges or image measuring instruments need to be used for the multi-point measurement of the nominal hole diameter sizes and their tolerances, and at the same time, the centre distances of the adjacent holes and the row spacings are measured, to evaluate whether the perforating precision and pattern consistency meet the drawing or standard requirements.

Hole shape and burr: Checks the hole edge quality after the perforating, including observing whether the hole shapes are regular (such as whether the round, square and oblong holes deform), and whether there are the sharp burrs generated by the blanking at the hole mouths. The burr heights usually need to be measured with the micrometers or surface roughness testers, and the excessive burrs will affect the safety and use performance.

Plate thickness and flatness: Detects the actual thickness of the steel plate after the perforating, ensuring that it is within the allowable negative tolerance ranges. At the same time, the flatness of the steel plate needs to be detected. The surface plates, feeler gauges or laser flatness meters are used to evaluate whether the perforating process causes the warping, wavy deformation, etc. of the plate, which affect the subsequent installation and structural strength.

Material and mechanical properties: The chemical composition of the steel plate substrate is verified through the spectrometers, confirming its designations (such as Q235 and 304 stainless steel). When necessary, the samples need to be taken for the mechanical property tests such as the tensile, hardness and bending, to ensure that the perforating process does not cause the significant damage to the material properties (such as the strength and ductility).

Surface quality and coating: Checks whether there are the defects such as the scratches, press marks and rust on the steel plate surface. For the coated perforated plates such as the galvanized, plastic-sprayed and painted, the coating thicknesses (with the coating thickness gauges), adhesion (cross-cut method) and corrosion resistance (salt spray testing) need to be detected, evaluating whether the perforating destroys the continuity and protection of the coating.

Opening rate calculation and verification: The opening rate is an important functional indicator of the perforated plate, referring to the percentage of the total hole area to the total plate area. Through the precise measurement of the hole diameters, hole spacings and arrangement modes, the theoretical calculation is carried out, and compared and verified with the actual sampling weighing method (measuring the mass difference per unit area between the perforated and non-perforated plates).

Testing Scope

Perforated plates for the building decoration: The perforated metal plates applied to the fields such as the building curtain walls, ceilings, guardrails and sound-absorbing panels. The testing emphasis is on the appearance decoration (beautiful and consistent hole pattern designs), safety properties (edge burrs and structural strength) and the specific functionalities, such as the sound absorption coefficient verification of the acoustic materials.

Perforated plates for the industrial screening and filtration: Used for the screening equipment of the mining, grain and chemical industries, or as the filtering elements. The testing core is the hole diameter size precision, tolerance bands and uniformity, directly related to the screening efficiency and filtration precision. At the same time, the wear resistance and fatigue resistance need to be strictly tested.

Machine equipment protection and ventilation covers: Used for the motor housings, equipment protection covers and ventilation and heat dissipation windows. The testing needs to focus on the mechanical protection effects of the holes (such as the finger protection testing, ensuring that the hole sizes will not cause the accidental contact dangers) and whether the ventilation areas meet the design requirements.

Perforated plates for the traffic facilities: Such as the highway noise barriers and metro ventilation grilles. In addition to the routine dimension testing, their long-term outdoor weather resistance and vibration fatigue resistance are emphatically tested, and for the noise barriers, whether their acoustic properties meet the standards also needs to be tested.

Perforated plates for the agriculture and storage: Such as the grain depot ventilation ground cages and livestock and poultry breeding fences. The testing focuses on the hole unobstructedness, anti-clogging ability, and the corrosion resistance of the material (especially when contacting the humid environments or corrosive materials).

Plates for the new energy and environmental protection equipment: Applied to the dust collector filter bag cages, flue gas desulphurization tower packing support grids and photovoltaic equipment bracket ventilation plates. The testing of the high-temperature resistance, corrosion resistance, wear resistance and long-life reliability under the harsh working conditions is the key.

Testing Methods

Dimension measurement method: The traditional measuring tools such as the vernier callipers, micrometers and height gauges are used for the contact measurement, suitable for the fast detection of the regular hole shapes and easily accessible parts. For the batch testing, the go/no-go gauges (plug gauges) are commonly used to quickly judge whether the hole diameters are within the tolerance bands, with the high efficiency but without the specific values.

Optical image measurement method: The two-dimensional image measuring instruments or three-dimensional video microscopes are used for the non-contact measurement. This method has the high precision, can detect and capture the hole edges, automatically measure the geometric parameters such as the hole diameters, hole spacings and roundness, and can generate the test reports. It is particularly suitable for the precision detection of the complex patterns and micro holes.

Coordinate measuring method: For the large or perforated plate components with the three-dimensional geometric tolerance requirements, the coordinate measuring machines (CMM) are used for the high-precision testing. The three-dimensional coordinates of the hole centres can be precisely obtained, thereby calculating the complex form and position errors such as the hole position degrees and plate surface flatness.

Surface roughness and burr measurement method: The probes of the portable surface roughness testers are used to move across the hole edges, quantitatively measuring the burr heights (Rz values) or roughness. The profilometers can also be used for the cross-section scanning, obtaining the more precise burr shapes and size data.

Chemical and mechanical property analysis method: The material compositions are quickly and non-destructively analysed with the spark direct-reading spectrometers or X-ray fluorescence spectrometers. The mechanical properties need to be tested by cutting the standard specimens from the plates according to the standards such as GB/T 228.1, and carrying out the destructive tests such as the tensile and bending on the universal material testing machines.

Coating property testing method: The coating thicknesses are measured with the magnetic or eddy current thickness gauges; the adhesion is tested with the cross-cut method and rated with the tape peeling; the salt spray resistance is tested according to the GB/T 10125 standard, placing the specimen in a salt spray test chamber for the continuous spraying, regularly observing the rust conditions and evaluating the corrosion resistance times.

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 10125-2021, Corrosion tests in artificial atmospheres — Salt spray tests

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

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

5. 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 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

General length measuring instruments: Including the high-precision digital vernier callipers (resolution 0.01 mm), outer diameter micrometers and depth gauges, used for the manual measurement of the basic dimensions. The hole gauges (plug gauges) are the dedicated limit gauges for quickly judging whether the hole diameters are qualified, and a set includes the go-end and no-go end.

Optical and image measuring equipment: The two-dimensional image measuring instruments combined with the high-resolution CCD cameras and automatic stages can automatically identify the edges through the software, and are the core equipment of the batch testing of the geometric dimensions of the perforated plates. The tool microscopes are suitable for the micro observation and measurement of the single hole shapes and burrs in the laboratories.

Coordinate measuring machine: As the ultimate testing means of the high-precision dimensions and geometric tolerances, the CMM acquires the point cloud data by contacting the workpiece surfaces with the probes, and can generate the comprehensive test reports after the software processing. Its measurement precision can reach the micron level, commonly used for the first article inspection and die acceptance.

Surface characteristic testing instruments: The portable surface roughness testers are used for the fast on-site evaluation of the hole edge quality. The profile measuring instruments can carry out the high-precision cross-section analysis of the burrs. The laser flatness meters can quickly scan the overall flatness of the large-size steel plates and generate the flatness cloud maps.

Material analysis instruments: The direct-reading spectrometers are used for the fast non-destructive analysis of the metal chemical compositions on site. The universal material testing machines equipped with the various fixtures can carry out the mechanical property tests such as the tensile, compression and bending. The hardness testers (Brinell, Rockwell and Vickers) are used to detect the hardness changes of the work-hardened areas possibly caused by the perforating.

Environmental and coating performance test chambers: The salt spray test chambers are used to simulate the marine or industrial atmospheric environments, testing the corrosion resistance of the perforated plates and coatings. The constant temperature and humidity chambers are used to test the performance changes under the damp heat environments. The adhesion cross-cut testers and coating thickness gauges are the essential tools of the coating quality control.

Dedicated function testing devices: Such as the protection performance test fingers (simulating the human hand joints), used to verify the mechanical safety of the protective perforated plates. The acoustic impedance tubes or reverberation chambers are used for the professional testing of the sound absorption coefficients and sound insulation of the sound-absorbing perforated plates.