MODEL nanodac™ Heat only Temperature Control and Carbon Potential Control using the nanodac Recorder/Controller Application Note

PublishTime：2022-06-14

When mild steels or certain low carbon steels are heated at temperatures above 900°C in a carbon rich atmosphere the surface of the steel absorbs carbon by diffusion. The depth of carbon enrichment depends on the time and temperature of the treatment known as carburising. The presence of carbon in the steel causes a change in its physical properties.
A Zirconia probe is used to measure the level of oxygen. It generates a millivolt signal based on the ratio of oxygen concentration between the reference airside of the probe(outside the furnace) and the amount of oxygen actually inside the furnace.
The temperature of the furnace is measured using a thermocouple. This may be a thermocouple mounted within the Zirconia probe or installed as a separate item. Together the temperature and oxygen level signals are used by the nanodac recorder/controller to calculate the actual percentage of carbon in the furnace atmosphere.
The carbon potential control loop increases the carbon potential by opening a solenoid valve which allows a carburising or enriching gas (e.g. propane) to enter the furnace. Conversely, to decrease the carbon potential, dilution air or nitrogen is introduced into the furnace.
The nanodac recorder/controller can trigger an alarm when the atmospheric conditions within the furnace are such that carbon will be deposited as soot on all surfaces inside the furnace, including the workpiece. Avoiding sooting protects the furnace lining, maintains the accuracy of the zirconia probe and stops formation of a soot barrier on the workpiece which can prevent carbon diffusion.
The nanodac recorder/controller has a probe cleaning strategy that can be programmed to occur between batches or manually requested by the operator. A short blast of compressed air is used to remove any soot and other particles that may have accumulated on the probe. Once the cleaning has taken place the time taken for the probe to recover is measured. If it is too long this indicates that the probe is ageing and needs replacement or refurbishment.

Brand of Product：	Eurotherm
Part#：	MODEL nanodac™ 、 nanodac™ More Part#
Product Category：	Recorder/Controller More
Application：	More
Data Type：	Application note & Design Guide More
Safety & Environment Standards：	More
Operating Temperature：	Please see the document for details
Qualification Grade：	More
Qualification Approval：	More
Package：
Language：	English Chinese Chinese and English Japanese
Date of Creation：	September 10
Version Number：	Issue 1
Data Encoding：	HA030817U003
Data Size：	760 KB

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