Nano Microporous Insulation for RH Degassers

In secondary metallurgy, the RH (Ruhrstahl-Heraeus) degasser is where a heat of steel gets its final chemistry. Molten steel circulates between the ladle and a refractory-lined vacuum vessel to remove hydrogen, nitrogen, and carbon under vacuum. Every pass through that vessel costs heat, and every degree of temperature drop has to be bought back with extra superheat at the converter or EAF. A thin nano microporous backup layer behind the vessel working lining is one of the cheapest ways to slow that loss.

Why RH Vessel Heat Loss Matters

RH treatment is a temperature-sensitive process. The longer or harder the steel circulates, the more heat escapes through the vessel wall, and the further the bath drifts from the target window. When temperature runs low, operators respond in ways that all cost money: raising tap temperature, re-lancing, trimming alloys, or shortening the vacuum cycle before full degassing is complete. A more stable temperature lets the metallurgy do its job without fighting the clock.

The vessel wall is the leak point. A conventional lining stacks a dense working castable over a backing refractory whose insulating value is limited by its own thickness and mass. Nano microporous boards change that trade-off: they deliver the same thermal resistance as a much thicker conventional backup, in a layer only a few millimetres thick.

How the Backup Layer Is Built

A typical RH backup configuration places a nano microporous board between the vessel steel shell and the monolithic working lining. The boards are installed against the inner wall, then the castable working lining is applied over them. Board thickness is usually 3 to 5 mm, chosen to fit the vessel geometry and the thermal gradient the working lining is expected to carry.

The shell is cleaned and prepared before installation.
Microporous boards are fixed to the inner wall, cut and fitted to the vessel profile.
The castable working lining is installed over the boards, forming the hot-face layer.
Flexible sheet or custom-shaped boards cover curved and non-standard sections.

Because nano microporous board is cuttable with ordinary woodworking tools and can be supplied as flexible sheet or pre-formed shapes, it follows the vessel contour without gaps that would leak heat at the edges.

What the Backup Layer Does for the Process

Reduces heat loss during steel circulation, so the bath holds temperature through the full vacuum cycle.
Narrows the temperature window, improving the repeatability of degassing results.
Lowers the cold-face temperature of the working lining, which extends refractory life.
Adds negligible mass and thickness, so it fits vessels with tight geometry.

Choosing the Right Board Grade

The backup layer sits behind the working castable, so it does not see the full steel temperature. What matters is that the board’s continuous-use rating stays comfortably above the interface temperature it will actually experience. For RH vessels, Grade 1000 (rated 1000 °C) is the usual choice for a backup layer behind a monolithic hot face; Grade 1100 (1100 °C) is available where the layer sits closer to the hot face.

Property	Grade 1000	Grade 1100
Classification temperature	1000 °C	1100 °C
Density	220–280 kg/m³	220–280 kg/m³
Thermal conductivity, 200 °C	0.021 W/m·K	0.021 W/m·K
Thermal conductivity, 600 °C	0.028 W/m·K	0.028 W/m·K
Linear shrinkage (800 °C)	<2%	<2%

A 3-5 mm board is the starting point for design; the exact thickness is confirmed by a layer-by-layer thermal calculation so the board never exceeds its rated temperature. Our engineers run this check as part of a project-specific design.

Recommended products for this application: nano microporous insulation for steel ladles, custom-shaped boards, and standard boards.

Frequently Asked Questions

Why use a microporous layer instead of more castable?

Castable refractory is a structural and wear layer, not an efficient insulator. A nano microporous board is roughly three to four times more effective at slowing heat transfer than a conventional backing refractory of the same thickness, so it delivers far more thermal resistance for millimetres of build-up.

Can the boards survive the vacuum cycle?

Yes. The boards operate as a rigid, non-fibrous backup layer behind the working lining, not on the vacuum face. The microporous matrix is dimensionally stable at the interface temperatures it experiences, which keeps the layer effective across repeated treatment cycles.

Does the board affect vessel capacity?

Minimally and in the right direction. Because the board replaces a thicker conventional backup layer, the lining can be thinner for the same thermal performance, which in practice preserves or slightly increases the working volume of the vessel.

What if my RH vessel has an unusual profile?

Custom-shaped boards cut to the vessel profile, plus flexible sheet for curved sections, cover non-standard RH vessel geometries without the heat-leaking gaps that flat boards leave on a radius.

Need a layer-by-layer thermal check for your RH vessel? Talk to our steel-mill insulation engineers for a project-specific board and thickness recommendation. Contact us to get started.