Greetings from Germany.
You asked me about Henrichshütte.
I can tell you that it is still open for public. In addition, there are permanent exhibitions as well as special exhibitions.
However, the demonstration sites (don't know if that is the right word in english), such as a working foundry, are closed from November till March.
Hope I could help.
If you have further questions, I will try to answer them.
Greetings again, Julia.