Baltic Refractory Solution

Usage instructions for NOLTINA crucibles

NOLTINA crucible filling recommendations

Apter placed in a furnace the crucible should slowly get heated to 200°C in about 2 hour period to avoid moisture.. NOLTINA crucible is to be heated with low power to 600°C, before usage - to 950°C or higher if needed.

When NOLTINA crucible is used for aging, temperature of 950°C should be maintained for about and hour.

This will provide complete meltdown (amalgamation) of the glaze with additiona; ani-oxidating (layer) coating which  significantly extends the maximum lifetime of the crucible.

The crucible heating process should be repeated regularly but always before using after a long interval of desuetude. This helps to avoid unwanted effects from low temperatures.

Every time when the crucible is heated after cooling it is to be heated by the same regime as the first time after installation. The heating period of two hours could be ignored. However if NOLTINA crucible hasm't been used for a long time, it is necessary to avoid moisture that could have been absorbed from dross. In this case the crucible is to be heated to 200°C temperature. As soon as the specified temperature has been reached, the heating regime is to be continued as in the first time of heating.

The insjtruction description above conserns new crucibles that are placed in furnaces. Furnaces manufacturers instructions are to be followed if a new NOLTINE crucible is placed into a furnice. If the manufacturer of the furnaces has specified drying and melting time periods longer than the ones in this instruction, then the preperation of the furnaces is to be done without the crucible. This is necessary so that the crucible is palced into a completely dry furnace.

Storing

Crucible is to be store into a completely dry place. Absorption of moisture can result as cracks and flaking of the crucible during heating which could be a reason for oxidation of the material.

Transporting

Do not roll the crucible on the floor. Transport only in a suitable cart.

Examination

Chech the crucible for cracks and/or other defects before placing the crucible into a furnace.

Installation

A suitable stand should be used. It should be plain and flat and it's diameter should be a few millimeters wider thant the crucibles base. Base of the crucible will be compressed inward and may crack if the surface of the stand ir too small. Unprotected side of the base can be affected by a direct flame and it can burn out. A crucible can be installed into a furnace where space for the expansion of the crucible is considered. If the base of the crucible is close to the sides or bottom of the furnace, it has nowhere to expand and can result into cracks in the fringe or base of the crucible.

A crucible should be installed deep enough in the furnace to make sure that the top fringes are completely heated.

If a fringe of a crubile isn't protected with a furnaces lid, it is recommended to use steel rings to protect from cooling and mechanical wear at the time of loading. The rings should fit percetly inside the crucible at a depth of few centimeters.

Check for the flame to be controlled (steady).

The frame should enclose the whole crucible in a spiral up to it's top. The flame should create a smoke trail of a light green tincture which means that the atmosphere in the furnaces needs to be maintained in readily oxidizable conditions. However an excessive amount of air can cause burning of graphite, anticipatory oxidation and deterioration of thermal conduction.

Avoid any kind of cold (drafts) from getting into the furnace.

Keep the kilns emergency discharger concluded to avoid cold air from entering the frunace after turning of the burners. In case of using a fully automatical tilting furnace, make sure that the automatic air supply damper for the burner is closed when the furnace is in a inclined position.

Regularly check the furnaces state.

A damaged gass or oil furnaces lining will delay the movement of the flame in the chimney. This can cause flame limitation and heat accumulation which can lead to overheating of the crucibles walls.

Loading

• At the first time of burning ceramic crucibles are to be heated empty to their working temperature.
• Silicone carbide crucibles are to be heated fast to red heat.
• CLAY-GRAPHITE crucible should be heated slowly tillt they become red and then fastly to red heat.

This process ir described more detailed in the catalogue or techincal documentation.

Ingots and larger peaces of metal before placing into the furnace should be heated and then placed into the crucible with grips.

Do not nip the melting material into the crucible. Neiespīlējiet kausējamos materiālus tīģelī. Take care to always have place for the material to expand. Take in consideration that the thermal expansion factor ir higher than the crucibles material.

Do not force metal peaces or pressed metal chumps into the crucible. Avoid seizing. Metal expands faster and more than the crucible when heating up which can create cracks and snacks in the crucible.

Place ingots vertically and gently in the crucible using gripes. Forcing or throwing ingots, squeezing metal peaces will damage the curcibles interior.

Melting

Always fill the crucible possibly fuller. Heated, partially filled crucibles oxidize faster. It is recommended to pour out the melted metal from the crucible as soon as possible (as soon as it has reached puring temperature) or else the lifetime of the crucible reduces.

Preperation of melting material

Fluxes, modifying agents and chemicals affect the crucible with corrosion Do not place fluxes into an empty crucible. They melt faster then metal, enter the pores of the crucible, loosen it, burn out or evaporate before metal dissolves. Fluxes are to be added to melted metal or even yet - submersed to the bottom of the crucible with submersion bell (mixer). This will prevent the adverse effects on the crucible of fluxes and wil best dissolve in metal

Do not overdose with fluxes.  All undissolved material can get in the surface of a crucible, damage it and reduce it's lifetime if left in it.

Usage

Use exactly fitting lifting gripes. Gripes that do not fit perfectly on a crucible create an increased pressure in certain points and can result into wall lesions. Lifting gripes should cover the crucible at it's lower third.

Do not place a hot crucible on a cold surface. Uneven cooling can estroy crucibles base.

Always empty the crucible completely. Consolidated metal will heat and expand faster then the crucible at next heating and can break the crucible.

Cleaning

Remove slag and clean while it is still hot (red). Any kind of worn-out slag or residue behave as an isolator interfering normal heat flow and increase energy needed for melting. In addition excess fluxe in slag will expand 10 times more than the crucible which can caus ethe crucible to break.