Robotic Welding of Steel Casing for Electrodes used in Silicon Production

Abstract

Robotic welding systems are today frequently used in various types of manufacturing applications. This master's thesis examines the possibilities for implementing robotic welding in limited space at the smelting factories at Elkem Thamshavn and Elkem Salten. The goal is to see if it is possible with an efficient and economical way to automate the welding process. All furnaces using the Søderberg and Composite electrodes have the same challenge.

Ferroalloys and Silicon are produced in electrical furnaces at high temperatures, with carbon electrodes as the energy source (Elkem`s composite electrode technology). There are several types of electrodes, and the specific types that are examined in this thesis are the Søderberg and Elkomp electrode. The thesis will include practical experiments on the Søderberg electrode, and visual simulations of robotic welding on both electrode types.

Robotic welding is an important part of this thesis. The various parameters, requirements and methods are described for the welding process. Methods for programming of the welding trajectories are described in addition to technology such as optical laser system that makes the process more accurate. A description of the electrodes is given in addition to the challenges and limitations which make the automated welding difficult.

The possibilities for robotic welding is studied for two different electrode types, and the method has been approached differently for the two cases. An experimental study has been utilized on the Søderberg electrode in addition to simulation of the possible solution for the robotic welding in the future. For the situation at Thamshavn, which has Elkomp electrodes in the furnaces, a concept study has been utilized to see whether it is feasible or not to implement a robotic welding system on the electrodes.

The experimental study of the Søderberg electrode was successful and showed that it is possible to weld the most difficult parts of the casing at the electrode with an industrial robot. The result was demonstrated by programming the robot to weld two Søderberg casings together. The simulation also illustrated that it is possible to weld the whole casing with only one robot, with the solution that was created in this thesis.

The concept study included a solution which could reduce the amount of time with manual welding at Thamshavn and replace it with robotic welding. The solution includes CAD models of the electrodes and the area around with necessary equipment. The CAD model is implemented in a simulation software to illustrate the concept. Some modifications are done on the solution before the result is presented. The solution presented is however only feasible depending on the electrode positions, as the electrodes move vertically. To be able to implement an efficient and economical robotic welding process at Thamshavn, some reconstruction of the electrodes and the area around, are most likely necessary according to the result given in this thesis.