1、International Standard INTERNATIONAL ORGANIZATION FOR STANDARDIZATIONMEMYHAPDIIHAR DPrAHHJAUtiR fl0 CTAHAAPrbl3ALWl.DRGANlSATlON INTERNATIONALE DE NORMALISATION Steel and cast iron - Determination of total carbon content - Combustion gravimetric method Aciers et fontes - Dosage du carbone total - Mk
2、thode gravimdtrique apr b) for C contents ranging from 1 to 2 % : m3 about 1 g; c) for C contents greater than 2 % : m3 about 0,5 g. 7.3 Blank test Carry out the blank test by the combustion of the boat (HI in the presence of the same quantity of flux (4.3) used in the analysis, and carefully determ
3、ine the increase in mass (7) of the absorption bottles IN). Where there is any doubt about the purity of the boat, this should be verified by the combustion of the same boat in the presence of the same quantity of flux (4.3) used in the analysis and carefully weighed, and a quantity of weighed elect
4、rolytic iron (4.4). 7.4 Combustion Place the test portion (7.2) in the boat (HI and, if necessary, add 1 to 2 g of flux (4.3) to the test portion, especially in the case of high alloy steels. Open the combustion tube at the end where the oxygen enters and, using a rigid nickel wire, place the boat (
5、H) and the test portion in the middle of the heated zone of the tube. Quickly close the tube and, after about 1 min, pass through it a current of oxygen at the rate of 300 to 500 ml/min, depending on the diameter of the tube used. After about 1 min, when the com- bustion has ended, continue to pass
6、oxygen through for another 15 to 20 min so that the carbon dioxide is completely removed from the combustion tube (G), the washing bottle (L) and the drying bottle (MI. NOTE - Shorter times may be used for low carbon contents and when using induction furnaces. 7.5 Determination Cut off the oxygen cu
7、rrent, close the taps of the weighed ab- sorption bottles (N) and remove the porcelain boat from the combustion tube (G). It is necessary to verify that the combus- tion has been efficiently completed by examining the fused mass in the boat removed from the furnace. Disconnect the absorption bottles
8、 (N) and weigh them at am- bient temperature. It is recommended that any electrostatic charge on the absorption bottles should be eliminated by earthing the moving element of the balance. The increase in mass (ml1 represents the carbon dioxide absorbed. 3 Copyright International Organization for Sta
9、ndardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 437-1982 (El 8 Expression of results The carbon content is given, as a percentage by mass, by the formula 0,273 m1 - m2 x loo m3 = 27.3 m - m2 “3 where ml is the
10、mass, in grams, of the carbon dioxide obtained from the combustion of the test portion; m2 is the mass, in grams, obtained from the blank test; m3 is the mass, in grams, of the test portion; 0,273 is the carbon dioxide to carbon conversion factor. 9 Test report The test report shall include the foll
11、owing particulars : a) the method used, by reference to this International Standard; b) the results, and the form in which they are expressed; c) any unusual features noted during the determination; d) any operation not specified in this International Stan- dard, or any optional operations which may have influenced the result. 4 Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
