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Carbon electrodes

 Use of SonicByte^TM on a production line of carbon electrodes for the steel industry's electric arc furnaces

Electric arc furnaces in the steel industry

Used to melt scrap, electric arc furnaces in the steel industry involve the use of graphitized electrodes whose premature failure causes production shut downs whose estimated cost is 1000$ per minute! (see Fig. 1). 

Fig. 1: Electrodes premature failure in service. 

Electrodes quality control using SonicByte^TM

A total of 284 graphitized electrodes were tested at the factory using SonicByte^TM. These tests were made on line by installing two hydraulic hammers and two microphones on the 4-point bench test traditionally used by the manufacturer as a tool for quality control. One of the hammer was used to impact the electrodes under flexural conditions. The other hammer was used to impact the electrodes along their longitudinal axis (see Fig. 2).

Two groups of electodes having a lenght of about 259 cm (8,5 feet) and an outer diameter of about 64 cm (2,1 feet) were tested with the SonicByte^TM prior being submitted to the 4-point bend test. The acoustic signals generated by each electrode after impact were treated by the SonicByte^TM to determine non destructively their modulus of rupture (MOR).

By referring to the graph shown on figure 2, the SonicByte^TM detected two different mechanical resistance intervals from the two groups of electodes. Among the group showing lower resistances, the two electodes with the lowest MOR values, according to SonicByte^TM, are also those that were fractured during the 4-point bend test (see the two red dots on the graph). 

Fig. 2: Automated quality control devices and results obtained.

Unlike the later traditional quality control test method, which reduces the electrodes' strenght by up to 5% (according to previous work), SonicByte^TM offers much higher resolution for non destructive detection of the quality variations between the produced electrodes.