In the last article we talked about structure of the rolls, today we will continue discuss the roll casting moulds, and we will focus on their use.

Part 2: What They Do Dictates the Details—Moulds for Hot, Cold, and Section Rolling

Now that we’ve covered structure, let’s talk about how rolls are used. A roll that presses red-hot steel (hot rolling) needs a very different mould than one that smooths cold, thin sheets (cold rolling).

Hot rolling rolls are workhorses. They handle blistering temps (500-1000°C) and constant thudding from heavy steel. Their moulds:

• Use sand coated with a fireproof “paint” (like bauxite) to stop molten metal from sticking or leaving pockmarks.

• Have extra-large risers (those “reservoirs” of molten metal) to feed the roll as it cools—up to 50% of the roll’s weight! Slow cooling (aided by insulation) keeps the metal from cracking under stress.

Cold rolling rolls are perfectionists. They press cold steel into ultra-smooth sheets, so their surfaces need to be flawlessly smooth (Ra≤0.8μm—smoother than a polished stone). Their moulds:

• Use super-fine resin-bonded sand for a glassy-smooth cavity. A graphite coating makes it even easier to pop the roll out without scuffing.

• Have ultra-precise shapes—no wobbly edges allowed. The mould’s “entry” for molten metal is at the bottom (a bottom-pour design) to avoid splashing and ruining that perfect surface.

Section steel rolls are the artists. They shape steel into angles, I-beams, and other tricky profiles, so their surfaces have complex grooves (called passes). Their moulds:

• Often use foam patterns (lost foam casting) that melt away when metal is poured, leaving behind exact replicas of those intricate grooves.

• Split into segments (like a puzzle) to make removing the pattern easy without damaging the delicate grooves. A thick coating protects those sharp edges from wearing down during casting.

In short: Hot rolling needs tough, stress-resistant moulds; cold rolling needs precision polish; and section rolling needs to nail the details.