Metallography
The mechanical, chemical and physical properties of metals and their alloys largely depend on their structure. They are determined through macro- and microscopic metallography that helps assess the impact of various processes on structural changes.
Macroscopic tests are used to:
- Examine welds;
- Reveal discontinuities in the material, such as cracks, porosity, insertions;
- Reveal segregation;
- Reveal the original structure;
- Reveal the distribution of sulfur - Baumann method.
Microscopic examination are used to:
- Identify the alloy;
- Reveal the structure, specifying the shape, dimensions, quantity and distribution of components;
- Detect structural defects or material defects;
- Examine phase transition mechanisms;
- Identify phases;
- Reproduce the applied processes;
- Examine the phenomena occurring during operation.
The testing options enumerated above can be used as long as the specimens are cut at the right place and prepared accordingly. The preparation process consists of:
- cutting;
- grinding;
- polishing;
- etching.
Break test
Break test consists of breaking a specimen on a strength testing machine by increasing the applied load until the specimen ruptures. The break surface is then observed to determine any defects such as cavities, non-metallic insertions, cracks, lack of fusion or incomplete fusion.
Break testing is among the test methods performed during a welder qualification exam.
Break tests are performed in conformity with the following standards:
PN-EN ISO 9606-1:2017-10 - Qualification testing of welders — Fusion welding — Part 1: Steels
PN-EN ISO 9017:2018-03 - Destructive tests on welds in metallic materials — Fracture test
Destructive hardness testing
Hardness measurement consists of pressing the indenter into the inspected material beyond the limit of elasticity until plastic strain occurs. In practical terms, hardness can be defined as a measure of a material’s resistance to plastic strain.
Hardness measurements are very often used in the industry as simple and quick tests, thanks to the correlation of a material’s hardness and its strength. Hardness measurements are used for material quality control, particularly after heat treatment or heat and chemical treatment.
We use KB Pruftechnik GmbH type KB 30 S FA hardness tester.
Hardness tests are performed in conformity with the following standards:
PN-EN ISO 9015-1:2011 - Destructive tests on welds in metallic materials — Hardness testing — Part 1: Hardness test on arc welded joints
PN-EN ISO 6507-1:2018-05 - Metallic materials — Vickers hardness test — Part 1: Test method
PN-EN ISO 6506-1:2014-12 - Metallic materials — Brinell hardness test — Part 1: Test method
PN-EN ISO 6508-1:2016-10 - Metallic materials — Rockwell hardness test — Part 1: Test method
Impact strength testing
Impact test is the simplest crack resistance testing method. It consists of striking a notched specimen, supported without attachment at each end, with a Charpy pendulum hammer, and measuring the rupture energy. The specimen is positioned so that the hammer strikes opposite the notch. The test result is the energy used to rupture the specimen.
We use Zwick/Roell Type HIT450P Charpy hammer for impact testing.
Impact tests are performed in conformity with the following standards:
PN-EN ISO 9016:2022-09 - Destructive tests on welds in metallic materials — Impact tests — Test specimen location, notch orientation and examination
PN-EN ISO 148-1:2017-02 - Metallic materials — Charpy pendulum impact test — Part 1: Test method
Bend test
A bend test is carried out specifically to identify the mechanical properties of brittle metals or alloys which are not identified accurately by a tensile test. In addition, brittle metals under tension are extremely sensitive to additional bending stress occurring in abaxial fixing of the specimen. Without the plastic deformation necessary to mitigate and balance the excessive additional stress, the specimen will break prematurely, which will ultimately render the results seriously flawed.
In a bend test, a specimen is bent at three points to a defined angle, typically 180°. After bending, the specimens are observed to determine whether any cracks or other defects are visible on the surface.
Bend tests are performed in conformity with the following standards:
PN-EN ISO 7438:2021-04 - Metallic materials — Bend test
PN-EN ISO 5173:2010 - Destructive tests on welds in metallic materials — Bend tests