Manganese Steel Plate Testing

Manganese steel plate inspection mainly conducts scientific testing and analysis on the chemical composition analysis, tensile property testing, impact toughness testing, hardness testing, metallographic structure examination and bending property 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: This is the basis of the manganese steel plate inspection, aiming to precisely determine the contents of the key elements such as the manganese, carbon, silicon, phosphorus and sulphur. Through the analysis results, it can be judged whether the steel plate meets the composition requirements of the specific designations (such as Q345, 16Mn and 65Mn), and its mechanical properties, welding performance and heat treatment response can be predicted, providing the key basis for the subsequent processing and application.

Tensile property testing: This testing is used to evaluate the mechanical behaviour of the manganese steel plate under the static tensile loads. The main determination indicators include the yield strength, tensile strength, elongation after fracture and reduction of area. These data directly reflect the load-bearing capacity, plasticity and uniform deformation ability of the material, and are the core parameters of the structural design and material selection.

Impact toughness testing: The Charpy V-notch impact testing is usually adopted, and the impact absorbed energy of the specimen is determined at the specified temperatures. This testing aims to evaluate the ability of the manganese steel plate to resist the brittle fracture under the dynamic loads or low-temperature environments, and is crucial for the structures in the cold regions or bearing the dynamic loads (such as the engineering machinery and bridges).

Hardness testing: The hardness is the indicator of the ability of the material to resist the local plastic deformation. For the manganese steel plate, the Brinell hardness (HBW), Rockwell hardness (HRC/B) or Vickers hardness (HV) testing is often adopted. The hardness value can indirectly reflect the strength, wear resistance and heat treatment effect of the material, and is a fast and effective means of the quality control and production process monitoring.

Metallographic structure examination: The microstructures of the manganese steel plate, such as the morphologies, sizes and distributions of the ferrite, pearlite, bainite and martensite, are observed through an optical microscope or scanning electron microscope. The metallographic analysis can reveal the internal quality of the material, judge whether its heat treatment process is appropriate, and explain the micro causes of its macroscopic performance.

Bending property testing: Through the cold bending or repeated bending testing, the plasticity and surface quality of the manganese steel plate during the bending deformation are evaluated. The testing mainly checks whether the cracks occur on the outer surface after the plate is bent to the specified angle under the specified bending mandrel diameters, used to verify the forming and processing adaptability of the material.

Testing Scope

Low-alloy high-strength manganese steel plates: These plates usually contain 1.0%-1.6% manganese, such as the Q345 series, widely used for the structural parts such as the buildings, bridges, ships and vehicles. The testing emphasis is on their comprehensive mechanical properties (strength, toughness and plasticity) and weldability, ensuring their structural safety under the complex stresses.

Wear-resistant high-manganese steel plates: Represented by the ZGMn13 series, with the manganese content as high as 11%-14%. After the water toughening treatment, the single austenitic structures are obtained, with the excellent work hardening ability and impact wear resistance. The testing core is their chemical composition, initial hardness and the depth and hardness of the hardened layers after the impact.

Manganese steel plates for the springs: Such as 65Mn and 60Si2MnA. The manganese element is used to improve the hardenability and strength. The testing needs to strictly control the chemical composition uniformity, decarburization layer depth, non-metallic inclusion grades and fatigue life, to ensure their high elasticity and relaxation resistance.

Manganese steel plates for the pressure vessels: Such as 16MnR and 15MnNbR, used to manufacture the pressure-bearing equipment such as the boilers and storage tanks. In addition to the routine mechanical properties, the testing scope must also include the high-temperature tensile, low-temperature impact, non-destructive testing (UT and RT), as well as the strict grain size and banded structure assessment.

Through-thickness performance steel plates (Z-direction steels): To prevent the lamellar tearing, the through-thickness reduction of area of this type of manganese steel plates needs to be detected. The Z-direction performance grades (Z15, Z25 and Z35) are determined through the tensile testing, supplemented by the sulphur content control and inclusion morphology examination, ensuring their tearing resistance in the thick-plate welded structures.

Hot-rolled and heat-treated steel plates: The testing scope needs to cover the products of the different delivery states. The hot-rolled steel plates mainly test their performances after the rolling; for the plates after the heat treatments such as the normalizing and quenching and tempering, the uniformity and effectiveness of their heat treatment processes need to be additionally verified, such as the hardness gradients and structure uniformity.

Testing Methods

Spectrometry analysis method: The spark discharge atomic emission spectrometer or X-ray fluorescence spectrometer is adopted for the fast and accurate quantitative analysis of the chemical composition of the manganese steel plate. This method has the simple sample preparation, fast analysis speed and high precision, and is the mainstream method of the smelting process control and finished product acceptance.

Universal material testing machine method: In accordance with the standards such as GB/T 228.1, a microcomputer-controlled electronic universal testing machine is used for the tensile testing. Through the high-precision sensors, the load and displacement are measured, and the stress-strain curves and the various strength and plasticity indicators are automatically calculated and output, ensuring the objective and reliable data.

Pendulum impact testing machine method: In accordance with the standard GB/T 229, an instrumented impact testing machine is used to impact the Charpy V-notch specimens at the preset low temperatures (such as -20 ℃ and -40 ℃). The testing machine records the load-time curves during the impact process, and can simultaneously obtain the impact absorbed energy and ductile-brittle transition characteristic data.

Hardness tester indentation method: According to the plate thickness, expected hardness range and standard requirements, the corresponding hardness testers are selected. The Brinell hardness tester (HBW) is suitable for the softer or thicker specimens; the Rockwell hardness tester (HRC/HRB) has the simple operation; the Vickers hardness tester (HV) is used for the precise measurement of the thin layers or micro areas.

Macroscopic and microscopic metallographic method: First, the low-magnification structure examination is carried out through the acid etching, observing the defects such as the porosity, segregation and cracks. Then, the specimens are cut, mounted, ground, polished and etched, and observed under a metallographic microscope according to the standards such as GB/T 13298, rating their microstructures, grain sizes, non-metallic inclusions and decarburization layer depths.

Non-destructive testing method: Including the ultrasonic testing (UT) for the detection of the internal defects (delaminations and inclusions); radiographic testing (RT) for the internal quality inspection of the welds; magnetic particle testing (MT) or penetrant testing (PT) for the inspection of the surface and near-surface defects. These methods do not damage the material and are the important means for ensuring the integrity of the key components.

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 13298, Inspection methods of microstructure for metals

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

Direct-reading optical emission spectrometer: As the core equipment of the chemical composition analysis, it is internally equipped with multiple photomultiplier tubes or CCD detectors, corresponding to the characteristic spectral lines of the different elements. During the analysis, the sample is excited in the argon atmosphere to generate the characteristic spectra, which are received by the detectors after the dispersion of the spectroscopic system and converted into the electrical signals, and the element contents are calculated by the computer.

Microcomputer-controlled electronic universal testing machine: Integrating the precision mechanical transmission, servo motor control, high-precision sensors and computer data processing. The testing process is controlled through the software programming, the force and deformation data are collected in real time, and the curve analysis, result calculation and report generation are automatically carried out, with the high testing precision and automation degree.

Fully automatic impact testing machine: With the functions of the automatic sample feeding, positioning, impacting, data acquisition and waste sample cleaning. The new instrumented impact testing machines are also equipped with the high-speed data acquisition systems, which can record the load-displacement curves of the whole impact process, for the in-depth analysis of the dynamic fracture behaviour and ductile-brittle transition characteristics of the material.

Full Rockwell/Brinell/Vickers hardness testers: The modern hardness testers generally adopt the closed-loop sensor and control technologies, realizing the high-precision loading and holding of the test forces. Most equipment are equipped with the electric lifting platforms, automatic turrets and image measuring systems, which can automatically complete the whole process of the indentation positioning, loading, holding, unloading and indentation diagonal measurement.

Digital intelligent metallographic microscope: Equipped with the high-resolution CCD cameras and professional metallographic analysis software. It can not only be used for the routine structure observation, but also carry out the automatic grain size rating, inclusion statistical analysis, phase area percentage calculation and the two-dimensional and three-dimensional reconstruction of the structure morphologies through the software, greatly improving the examination efficiency and accuracy.

Multi-channel digital ultrasonic flaw detector: Using the high-performance digital circuits and A/D conversion technologies, with the high signal-to-noise ratio and broadband characteristics. It can be connected to the various probes (straight-beam probes, angle probes and twin-crystal probes), realizing the A-scan, B-scan and C-scan imaging, and can store and replay the testing waveforms and data, which is convenient for the tracing and analysis of the defects.