I can't get very far in this tunnel; there's a locked gate

Hint 1 of 5:

The locked gate is blocking access to the rest of the tunnel.

Hint 2 of 5:

You don't have a key for this gate; besides, it looks as though it has been
welded shut.

Hint 3 of 5:

You could probably bust it open if you had a welding torch.

Hint 4 of 5:

Since you don't, you'll have to improvise.