BS ISO 7524:2020 pdf free.Ferronickels一- Determination of carbon content一Infrared absorption method after induction furnace com bustion.
BS ISO 7524 Ceramic crucibles, containing the sample and any additions that can be necessary, are required for the combustion. They shall be of precise dimensions for the system and fit the supporting pedestal post so that the test portion in the crucible is positioned correctly within the induction coil for heating.Tlypical dimensions of combustion crucibles are: a height of 25 mm, an external diameter of 25 mm, an internal diameter of 20 mm, a wall thickness of 2,5 mm and a thickness of base of 8 mm. The dimension of the hole of the lid should be larger than 10 mm.Crucibles and lids shall be as specified by the manufacturer of the instrumentation used and shall
be capable of withstanding combustion in an induction furnace without evolving carbon-containing chemicals so that achieving and maintaining blank values within specification is possible.In order to remove any carbon contamination, for the determination of carbon levels of less than 0,05 % (mass fraction), pre-ignite the crucibles in air or oxygen in a furnace for not less than 1 h at 1 100 °C and store in a desiccator or a closed container. A resistance furnace with a combustion tube through which a flow of oxygen passes may also be used.Crucible lids, used to help retain the solid oxidation products in the hot zone of the induction coil, shall be pre-ignited in a similar manner.For each instrument range, transfer the selected mass of flux (5.5.2), to the nearest 0,005 g, into a pre- ignited crucible [6.2), add the selected mass of a CRM (5.6) having a very low carbon content, and then cover it with the selected mass of accelerator (5.5.3). The type and mass of the flux and accelerator used in the blank test should accord with those used for determinations (details as in 8.4.1). Record the mass of the CRM. Place the crucible and contents on the furnace pedestal and operate the furnace in accordance with the manufacturer’s instructions. Repeat the determination three more times. Average the results.Subtract the carbon content of the CRM from the average to determine the blank value. If the blank is greater than 0,001 % (mass fraction) and the related standard deviation is greater than 0,000 2 % (mass fraction), find the cause of the problem, fix it and repeat the experiment.
Record the average blank value into the analyser in accordance with the manufacturer’s instructions.BS ISO 7524 pdf download.