TPT March 2024

ARTICLE

OMNI-X

The detail of an interface between aluminium-bronze and tool steel and the course of Vickers microhardness HV 0.5 for selected material combination is presented in the graph in Figure 2a and 2b. The balls were made of aluminium bronze as standard. Testing of the mandrel with bi-material shank was performed under the controlled conditions in Donaldson Domjean SAS company. The required bend radius (centre line radius – CLR) was 112mm ie 1.1D bend.

(a)

(b)

Figure 2: (a) The detail of an interface between aluminium-bronze and tool steel; (b) the course of Vickers microhardness HV 0.5 of the material combination aluminium-bronze/tool steel

Results The test took place in production batches for various CLRs over a ten-month period. 11,112 pieces of tubes were bent in total using the mandrel with the bi-material shank. Some tubes had multiple bends; therefore, the final number of actual bends was 16,232. The mandrel ball sets were replaced three times during the life cycle of the shank. Contrary to a standard shank, the increase of overall length of the processed tubes was over 2km. After the total wear of the shank, which was apparent on the quality of the bends, the shank was removed from a production and send back to OMNI-X to be restored.

Figure 3: The life cycle of the bi-material shank: (a) new mandrel with bi-material aluminium bronze/tool steel shank; (b) partially worn mandrel – after 8,000 bends; (c) worn out bi-material shank before restoration; (d) bi-material shank after restoration – ready to return to the production process (a) (d) (c) (b)

• Overall mandrel costs reduction thanks to the possibility of repeated shank restoration. • Less steel and aluminium bronze waste thanks to the possibility of restoring the functional surfaces of mandrels. • Ecological and health-friendly substitute of a galvanic surface treatments. Acknowledgements Special thanks to Donaldson Domjean SAS company for giving us the opportunity to test our mandrels and providing valuable feedback during testing.

After the cladding and manufacturing of new functional surface layer on final dimensions, the shank was placed back in a standard production.

The life cycle of shank is outlined in Figure 3a-d.

Conclusions Based on the information presented and the results shown in the above-mentioned, it can be concluded that the mandrel with the thermally applied layer to the shank, developed and tested by OMNI-X has the indisputable technological advantages. The main benefits are: • Longer expected statistical lifetime of mandrels – significant increasing of the service life in the course of operational tests under controlled conditions. • Thicker functional layer with a strong metallurgical bond with the base material. • Better abrasive wear protection. • Appropriate coefficient of surface friction. • Many possible potential material combinations; this cladding method is also applicable for other material combinations such as hard chrome, alternatively cobalt or cobalt-vanadium alloys.

OMNI-X – Czech Republic sales@omni-x.cz www.omni-x.com

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MARCH 2024