With a powered-by-phlebotinum (ergo very handy, very powerful) rifle, I am able to shoot high-energy beams which, in turn, can pulverize anything in their path in a considerable radius. The beams can travel very far in open air, and pierce every material known to man. They transmit mostly kinetic energy, but carry heat also.
At the present moment, for plot reasons, I'm shooting down a thick steel floor. I imagine that my beam will carve an hole into it, of the size of the beam itself.
To be precise, I'm shooting at an inclination of 30° from the ground, the beam is around 70 centimeters (27 inches) diameter, and I expect it to travel into layers of steel for about 200 meters before emerging on the other side. The beam is automatically focused, meaning it retains its width no matter the distance from the gun; also it can be emitted in a single, continuous pulse.
While I'm very sure that this will be enough to create a tunnel in the floor, I'm not sure how will the steel around the beam react. Will it overheat, and if so, for how long? Will it melt? I'm asking because I hope to use the hole created as a tunnel of sorts.
Extra informations: Feel free to suggest other characteristic for the beam, if you think they would suit the task better. Also, for the sake of the question, assume that the gun doesn't suffer from recoil, power shortage or overheating.