Design Solution for Ingot Handling and Machining
Abstract: At the electro remelting slag (ESR) facility at Uddeholm, cylindrical steel ingots are produced in several different sizes. The ESR process requires a “starting step” that consist of a 20mm thick steel plate and is a little larger than the diameter of the ingot. During casting the steel plate is inevitably welded to the ingot, also a protective slag layer is also present and flows on top of the melt when the ingot is produced. This layer is sacrificial and is removed before forging. The plate consists of a different and unwanted material composition and must be removed at some point to ensure the best material properties of the ingot. Current process steps at Uddeholm causes the steel plate to be smeared out on the high-quality ingot. The “impure” part of the ingot leads to extra waste and costs after forging. The ingots are cast vertically but needs to be positioned horizontally to be transported to the forge, this is done using an overhead crane and a clamp. This maneuver exerts excessive stress that damages the crane and the clamp sometimes fails and drops the ingot. Because of the high-risk steps during ingot handling as well as the extra waste that is created due to the starting step, the purpose of this thesis is to develop a solution that can: move the ingots from a vertical to a horizontal position in a controlled manner, a method to remove the starting step before forging and reduce the overall risks during ingot handling. The goal is to develop a complete concept that solves the problems mentioned so that the solution can later be realized.To get a deeper understanding of the current procedures and problems, visits and meetings at Uddeholm were carried out. This master thesis builds on the principle of the product development process. Interviews with operators, managers, and other impacted employees at Uddeholm were conducted in order to specify a product specification. To make the project more fathomable, six sub functions were defined. Later a concept generation session using the principles of brainstorming was held with engineers and managers at Uddeholm to find new, plausible solutions to the problems. The results from the session were reviewed and some solutions were discarded directly. Solutions that passed the screening was scored using a weighted decision matrix based on a Kesselring matrix.The chosen concepts were: milling to remove the starting step, “rotary axis grab” to rotate the ingots, a conveyor belt to transport slag, a vacuum and conveyor belt to remove chips, a roll bed with V-pallets to handle and transport the ingots, and let the slag fall of naturally when horizontal. These solutions fulfill almost all of Uddeholm’s requirements and will significantly increase the safety and profitability. The new solutions also bring in high flexibility for production and will free up time for the operators.The lifting tool of the solution needed to be structurally verified to prove it is a valid option. This was done by analyzing the maximum stress in one part of the tool. The results gave that it was indeed a feasible solution.The whole product development process has proven helpful for this machine system. It has especially proven useful for documenting all decisions made throughout the project. This makes it easier for Uddeholm to adopt the solution and develop it further and later realize it.
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