Materials engineering investigation of welds
We can perform all weld inspections. Both destructive testing and non-destructive testing. Partially we fall back on partners for this. Below are some examples of tests as they are regularly performed and documented in our laboratory.
Inspection of welds:
Due to our extensive technical center, we are also able to produce and directly test samples with the welding procedures 111, 131, 135 and 141 in order to determine the optimum process parameters for a specific application. The derivation of preliminary welding procedure specifications (WPSs) from these test results is part of our daily activities. If necessary, you can weld samples again with these parameters under our supervision, from the test results of which we derive a procedure qualification record (WPQR- Welding Procedure Qualification Record) after testing. Of course, we also offer the supervision of welder and operator tests.
Testing of welded components:
You buy welded components and want to check whether the weld seam meets the technical requirements. Send us the technical drawing and the component and we can test it, for example, by macrosection and hardness tests and/or as a certified visual and radiographic tester for its internal and external values. In addition to internal quality assurance, we can also prepare reports on these component weld seam tests, e.g. in accordance with DVS Merkblatt 1621 "Arbeitsproben im Schienenfahrzeugbau".
Testing of components or materials:
Apart from weld seams, there is often the question of whether the hardness of a sheet or the strength of a bar meets the requirements. We can carry out a wide range of internal hardness testing procedures (e.g. Rockwell, Brinell, Vickers). In addition to the conversion of hardness into strength, we can determine by means of tensile testing at which point a component fails at which load or force.
Real-world examples:
Hardness tests and macrosections
Figure 3: TIG welded structural steel component in which inadmissible and potentially dangerous bonding defects were found in the macrosection. The component was removed from the production line during a supplier audit.
Fracture test for welder tests according to ISO 960
Tensile tests
Figure 6: Tensile test on welded reinforcing steel Fig. C.3 according to DIN 17660; material B500B; MAG welded 2 bars with a diameter of 20 mm to a bar with a diameter of 28 mm. The Ø = 28 mm bar has a load-bearing area of approx. 616 mm², the two Ø = 20 mm bars together have a load-bearing area of approx. 628 mm². Due to an impermissible ignition point on one of the Ø = 20 mm bars, failure of the link bars occurred despite the area advantage, which is otherwise very unusual with a link joint. Minimum breaking force approx. 338 kN ~ 34 t
Figure 7: Tensile test on welded reinforcing steel Fig. C.2 according to DIN 17660; material B500B: Process 111 was used to weld 2 bars with a diameter of 25 mm together in a lap joint. The Ø =25 mm bar has a load-bearing area of approx. 491 mm². In the upper series of images, only the root was welded and the top layer was omitted for experimental reasons. The specimen of the lower picture series is completely welded (i.e. root layer and cover layer). Minimum breaking load approx. 270 kN ~ 27 t. In the case of the specimen where only the root was welded, the base material was weakened to a lesser extent by the application of heat, so it was able to withstand a minimally higher force. It can be clearly seen that the upper specimen did not fail in the heat-affected zone of the weld, although a three-dimensional stress state is created here due to the geometry of the lap joint. The lower specimen failed precisely in this area.
Figure 8: Tensile test at right angles to the machined weld according to DIN EN ISO 4136 of welded S355XY It is clearly evident from the stress-strain diagram that the minimum tensile strength of the material is exceeded. As expected, the elongation at break decreases compared to the unwelded material. Responsible for the decrease in elongation at fracture are, for example, the shrinkage-induced strain hardening, residual stresses, the local strain concentration at the position of the heat-affected zone and the notch effect (microstructure notch, chem. gradient) at the transition from base metal to weld metal.
