If it was homogenous steel plate, definitely. My understanding is that modern tank armor is actually a composite with many layers of materials like hardened steel, rubber, ceramic, etc. Those allow disruption of kinetic penetrators and shaped charges more effectively than a homogenous piece of steel, so effectively more armor 'thickness' for a given weight/thickness.

No idea how they weld those things together!

There are some neat videos on youtube showing some pretty cool simulations of the how and why.

Yup good points. I now rememeber "dorchester" and "chobham" armours. I must say that I too am at a loss to imagine how they are fabricated into solid hulls!