system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why aren't stainless steel countertops, like in restaurant kitchens, magnetic, but stainless steel knives are?
gpt
Mechanical engineer here (some material engineer might come around and give a better explanation):

It all has to do with the crystalline composition of your Stainless Steel. Most of the Stainless steel is made of Ferritic SS, which is cheap to fabricate and can be transform quite easily. Austenitic SS is the most corrosion resistant steel and is mostly used for specific application. The 304 series are usually used for Food grade purpose for example. Both of them are non magnetic.

Mastensitic SS is highly durable, very hard and easy to machine. Those 3 properties makes it very good for kitchen knives. It is also (almost?) the only type of SS that is magnetic.

Hope that helps.