​

SALT BATH

​

Molton Salt Bath of various compositions is available to cover temperature range 150-1320°C. This method offers a number of advantages over alternative processes. Treated parts have a clean, bright, scale-free finish and soft surface ( decarburization) can be completely eliminated. The circulation of molten salt provides a constant temperature throughout the charge giving accurate temperature control and uniform results. The rapid rate of heat transfer by the bath enables a high output to be from a relatively small furnace. Moreover, highly personnel are not operating the salt bath process.

NEUTRAL SALTS:

​

FRANK 720 / FRANK REGENERATOR

WORKING RANGE: 720 -900°C

(950°C if covered with FRANK ECONOMISER)

​

FRANK 720 is usually used with FRANK REGENERATOR as a neutral salt which is free from any decarburization tendency and is readily soluble in water. It neither carburizes nor decarburizes steel.

​

The bath is used for Heat Treatment of various carbon and alloy tool steels in the working range stated.

It is very suitable for the heat treatment of parts which have been carburized and then selectively machined to remove the carburized case from areas required soft. FRANK 720 is also a suitable heating medium for parts that are subsequently martempered or austempered in FRANK 150.

​

To make up the initial melt the weighed quantity of FRANK 720 is placed in a furnace fitted with treated Mild steel or heat-resisting alloy pot or in a ceramic-lined electrode type furnace and is then heated until the Salt melts. When the bath is at the normal operating temperature FRANK REGENERATOR is added at the Rate of 330gms per 100 kg of salt. It is usual to use a layer of FRANK ECONOMISER on the surface of the Molten bath except in special cases like the treatment of stainless steel, for which Economiser is unsuitable.

​

FRANK REGENERATOR forms a layer on the bottom of the pot and in externally fired pots. This layer tends to become hotter than the salt itself.

​

Care should, therefore, be taken to prevent the end of the pyrometer thermocouple, or the work being treated from dipping into this layer. At the end of each working day, the bath is dredged to remove the bath to its normal working level and FRANK REGENERATOR is then added. The amount of FRANK REGENERATOR required varies with the type of furnace, its temperature, the time of soaking at the appropriate temperature, the cleanliness of work and whether the bath is covered with FRANK ECONOMISER. The average additions to a bath with FRANK ECONOMISER cover is about 330 gms per 100 kg of salt per 8 hours a day.

​

When the melt is properly regenerated and had settled, it has a clear transparent appearance. Cloudiness may indicate the need for regeneration, although excessive amounts of FRANK REGENERATOR should not be added or an undesirable heavy layer of sludge will be produced at the bottom of the pot. Normally the sludge dredged from the pot is of a spongy nature if it is sticky, it indicated insufficient regeneration.

​

Treatment of rusty or scaly work should be avoided. This causes an excessive amount of oxides into the bath which produces a sticky slag, necessitating increased additions of FRANK REGENERATOR.

​

SALT BATH

​

Molton Salt Bath of various compositions is available to cover temperature range 150-1320°C. This method offers a number of advantages over alternative processes. Treated parts have a clean, bright, scale-free finish and soft surface ( decarburization) can be completely eliminated. The circulation of molten salt provides a constant temperature throughout the charge giving accurate temperature control and uniform results. The rapid rate of heat transfer by the bath enables a high output to be from a relatively small furnace. Moreover, highly personnel are not operating the salt bath process.

NEUTRAL SALTS:

​

FRANK 720 / FRANK REGENERATOR

WORKING RANGE: 720 -900°C

(950°C if covered with FRANK ECONOMISER)

​

FRANK 720 is usually used with FRANK REGENERATOR as a neutral salt which is free from any decarburization tendency and is readily soluble in water. It neither carburizes nor decarburizes steel.

​

The bath is used for Heat Treatment of various carbon and alloy tool steels in the working range stated.

It is very suitable for the heat treatment of parts which have been carburized and then selectively machined to remove the carburized case from areas required soft. FRANK 720 is also a suitable heating medium for parts that are subsequently martempered or austempered in FRANK 150.

​

To make up the initial melt the weighed quantity of FRANK 720 is placed in a furnace fitted with treated Mild steel or heat-resisting alloy pot or in a ceramic-lined electrode type furnace and is then heated until the Salt melts. When the bath is at the normal operating temperature FRANK REGENERATOR is added at the Rate of 330gms per 100 kg of salt. It is usual to use a layer of FRANK ECONOMISER on the surface of the Molten bath except in special cases like the treatment of stainless steel, for which Economiser is unsuitable.

​

FRANK REGENERATOR forms a layer on the bottom of the pot and in externally fired pots. This layer tends to become hotter than the salt itself.

​

Care should, therefore, be taken to prevent the end of the pyrometer thermocouple, or the work being treated from dipping into this layer. At the end of each working day, the bath is dredged to remove the bath to its normal working level and FRANK REGENERATOR is then added. The amount of FRANK REGENERATOR required varies with the type of furnace, its temperature, the time of soaking at the appropriate temperature, the cleanliness of work and whether the bath is covered with FRANK ECONOMISER. The average additions to a bath with FRANK ECONOMISER cover is about 330 gms per 100 kg of salt per 8 hours a day.

​

When the melt is properly regenerated and had settled, it has a clear transparent appearance. Cloudiness may indicate the need for regeneration, although excessive amounts of FRANK REGENERATOR should not be added or an undesirable heavy layer of sludge will be produced at the bottom of the pot. Normally the sludge dredged from the pot is of a spongy nature if it is sticky, it indicated insufficient regeneration.

​

Treatment of rusty or scaly work should be avoided. This causes an excessive amount of oxides into the bath which produces a sticky slag, necessitating increased additions of FRANK REGENERATOR.