Steel – the All-Rounder That Has to Pass Many Tests

If we wouldn’t comply with the highest standards of quality, we would not rank among the world’s best companies. As an accredited testing laboratory, we have to meet stringent specifications and are therefore able to vouch for the reliability, objectivity and accuracy of our results – irrespective of whether we inspect our own products during the production processes or, for instance, inspect damage and write appraisals on behalf of a customer. Quality control begins from the very moment the steel is melted.

The chemical composition of the melt, the so-called melting lot, is of fundamental importance for the properties of the material for the entire duration of the production process. Only non-destructive examinations can provide the engineer with the necessary information for assessing whether each volume element of the component will bear the required load when in use. The interior of the component is examined with ultrasound to detect any defects, the surfaces are subjected to magna flux or dye penetrant testing to check for the fi nest cracks. Mechanical inspection, purity testing and structural analysis under the microscope of samples from defined test positions of the components yield further data on the properties of the products. The type and number of samples at the various test positions depend on the component, of course. To obtain further information on process influences we also analyze specific samples in the scanning electron microscope.

Generator and turbine shafts weighing up to 70 tons are complex one-off parts from our opendie forge. They are rigorously inspected during the long manufacturing process. If defects are not found until the end, we not only lose money, but also risk losing our reputation with the customer. Most of the series-produced components from our closed die forge or the rolling mill, such as vehicle gear components, also have to meet high quality specifications. The customer has to be sure that the entire series is O.K.

Quality testing is considerably time-consuming. An ultrasonic inspection of a large generator shaft takes between three and five days, depending on the number of test positions. Everything has to be documented – even structural effects under a critical size have to be registered. Mechanical and microscopic testing usually takes us one to two days. Most of the time is spent on taking samples and preparing them for inspection. All the test results related to the criteria defined by the customer are finally documented in a certificate that is given to the customer together with his component.

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