New RH system in steel mill increases quality and vacuum capacity
19.07.2017 | Salzgitter Flachstahl GmbH
The fist ladle underwent vacuum treatment in the RH system on April 7 2017. “The investment in an RH system is our response to the challenges that the market and our customers pose,” explains Dr. Andreas Berghöfer. “This was necessary in order for us to be leaders in our target segments.” Salzgitter Flachstahl’s secondary metallurgy capacities were no longer sufficient in this regard, but the new system is expected to remove this bottleneck. The head of the smelting operation knows exactly what he is talking about, because he is seen as the system’s initiator and he also has overall responsibility for its construction and operation.
Salzgitter Flachstahl customers from the automotive industry want grades with very high formability for use in vehicle body shells, for example, “If we also want to open up new sales segments, we need the steel grades with the highest purity levels,” adds Christian Schlüter, head of Secondary Metallurgy. The new system should deliver around 1.3 million metric tons of such steel annually.
“It took ingenious planning to integrate the system into the steel mill,” says Project Manager Dr. Pamela Wolf as she explains the major project’s challenges.
In the system, vacuum treatment decarburizes and degasses the liquid steel in order to improve the steel’s characteristics during further processing. These steel grades with the highest purity levels have very high formability and high strength. The method is named after the two firms that developed it: Ruhrstahl and Heraeus.
How it works:
The RH technique is a so-called vacuum subset procedure. A vacuum sucks a subset of the liquid steel out of the ladle and into a vessel lined with refractory materials with the help of two immersed snorkels that are located on the bottom of the vessel. When argon is injected into one immersed snorkel, the resulting density reduction causes the liquid steel to rise into the vacuum container, where the melt is decarburized with oxygen before it flows through the other immersed snorkel and back into the steel casting ladle. Alloying materials can also be added during the vacuum treatment.
Our Technical Customer Services would be happy to answer any questions you may have on the RH procedure.