About 10 years ago, I wrote my master’s thesis on scheduling steel production. In my research, I read a lot about the steel industry, particularly about steelmaking processes and optimizing steel production schedules. One of the interesting topics I read about was hot charging: Optimizing the path between steel casting and hot rolling so that the cooling of slabs between those two processes is minimized. Hot charging promises significant cost savings as less energy is needed to reheat the slabs to the temperature required for hot rolling. Consuming less energy for the heating process also leads to reduced CO2 emissions.
Hot charging is not a new idea – it originated in Japan in the 1970s. As a student reading up on the theory 30 years later, I assumed that the hot charging of steel was an already solved problem. But as is often the case, things that seem simple in theory are not quite as straightforward in practice. In the past 10 years I have worked with several steel companies in Europe and the consensus is clear: Hot charging is anything but a solved problem.
What is it that makes hot charging such a difficult goal to reach? First of all, it’s a fallacy to assume that hot charging is something that you only ever need to implement once. Trends in the steel industry such as growing product portfolios and smaller order sizes are actually making hot charging even more difficult, and some steel producers are reaching lower rates of hot charging today than they have in the past.
Steelmaking, casting and hot rolling are all complex processes, and different exceptions and disruptions in each process are common. This creates a need for frequent rescheduling: It is not enough to create a single schedule that optimizes the hot charging rate, because soon enough something is bound to happen in production which will require a change in the schedule. Most steel companies do not have the scheduling support that would enable them to cope with those changes while also maximizing hot charging rate. For example, if some of the slabs need unplanned surface conditioning after they have been cast, planner has to be able to reroute them to appropriate conditioning resources and reschedule them in the hot mill sequence. When the hot rolling mill has an unplanned stop of a few hours, the system should support the planner in adjusting the casting schedule so that the slabs are still arriving hot when the rolling mill is back up and running. This may involve storing slabs temporarily under heat-retaining hoods, but these also typically have a limited capacity which has to be taken into account.
Current scheduling systems at many steel companies do not provide accurate feedback about the latest production status, nor do they provide visibility over both casting and hot rolling. For example, they are not able to calculate the hot charging rate KPI of the schedule. Without accurate feedback and visibility, the consequences of disruptions and of re-scheduling actions are not clear.
At Quintiq, we have spent the past few years mastering the scheduling puzzles of steel casting and hot rolling, both complex puzzles on their own. Today, we are setting the bar higher and helping our customers in the steel industry to schedule both casting and hot rolling in one solution. This gives them the control they need over these processes to enable them to achieve a higher rate of hot charging. This way, we are helping our customers lower their production costs and reduce their CO2 emissions.
To learn more about how we have helped leading steel manufacturers with better process scheduling support, download our brochure.
This post was previously published on LinkedIn.