GB/T 4702.14-1988 Chemical analysis of chromium metal - Determination of carbon content by infrared absorption method

This standard applies to the determination of carbon content in metallic chromium. GB/T 4702.14-1988 Chemical analysis method for metallic chromium - Determination of carbon content by infrared absorption method GB/T4702.14-1988 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Methods for chemcal analysils of chronlum meta]Tbe infrared absorption method for thedetermination of carhon contentThis standard is applicable to the determination of carbon content in chromium. Determination range: 0.010%～0.070%. UDC 669.26
GE 47 02. 14—88
This standard complies with the general principles and general provisions of GB 146778 Standard for Chemical Analysis Methods for Metallurgical Products. 1 Method Summary
The sample is heated and burned in the oxygen flow of a high-frequency induction furnace. The generated carbon nitride is carried by oxygen to the measuring chamber of the infrared analyzer. Carbon dioxide absorbs a certain amount of infrared energy, and its absorption energy is proportional to its concentration. The carbon content can be measured according to the change in the energy dissipation received by the detector. 2 Reagents and Materials
2.1 Acetone: The carbon content of the residue after evaporation is less than 0.0005%. 2.2 Magnesium perfluorate: anhydrous, granular.
2.3 Burnt stone: granular.
2.4 Glass wool.
2.5 Duck pellets: The carbon content is less than 0.002%. The particle size is 0.8~1.4 mm. 2.6 Tin pellets: The carbon content is less than 0.002%, and the particle size is 0.4~0.8 mm. If necessary, wash with acetone (2.1) and dry the coal at room temperature. 2.7 Oxygen: purity greater than 99.95%. Other grades of oxygen may also be used if a low and consistent blank can be obtained. 2.8 Power gas source: nitrogen or compressed air, with impurities (water and oil) less than 0.5%. 2.9 Quality crucible: medium ×, m: 23×23 or 25×25, and burned in a high-temperature heating furnace above 1200℃ for 4 hours or burned with oxygen until the empty value is the lowest.
2.10 Glass tongs.
3 Instruments and equipment
3.1 Infrared absorption carbon determination instrument (sensitivity is 1.0ppm). Its device is shown in the figure.
3.1.1 Washing bottle (3): Contained with caustic soda asbestos (2.3). 3.1.2 Drying tube (4,9); Contained with magnesium perchlorate (2.2). 3:2 Gas source
3.2.1 The carrier gas system includes an oxygen container, a two-stage pressure regulator and a timing control part that ensures the provision of appropriate pressure and rated flow. 3.2-2 The power gas source system includes power gas (nitrogen or compressed air), a two-stage pressure regulator and a timing control part that ensures the provision of appropriate pressure and rated flow.
Approved by the Ministry of Metallurgical Industry of the People's Republic of China on February 2, 1988 and implemented on March 1, 1989
3.3 High-frequency induction furnace
GB 4702. 14-88
1—Hydrogen cylinder, 2—Two-stage pressure regulator 13—Gas washing bottle: 4, 9—Drying belt, 5—Pressure regulator, 6—Commercial frequency induction furnace + 7—Combustion tube, 8—Dust removal tube, 10—Flow controller + 11—Converter for converting carbon dioxide into carbon dioxide, 12—Desulfurizer, 13—Carbon dioxide infrared detector should meet the requirements of the melting temperature of the sample.
3.4 ​​Control system
3.4.1 The microprocessor system includes a central processing unit, memory, keyboard input device, information center display screen, analysis result display screen and analysis result printer, etc.
3.4.2 Control functions include automatic loading and unloading and furnace lifting, automatic cleaning, analysis condition selection and setting, analysis process monitoring and alarm interruption, analysis data collection, calculation, calibration and processing, etc. 3.5 Measurement system
It is mainly composed of an electronic balance (sensitivity not greater than 1.0 mg) controlled by a microprocessor, an infrared analyzer and electronic measuring elements. 4 Sample
4.1 All samples should pass through a 1.68 mm sieve. 5 Analysis steps
5.1 Sample quantity
Weigh 0.400~0.500g of sample.
5.2 Blank testbzxz.net
Weigh 0.400~0.500g of low-carbon (carbon content less than 50ppm) standard sample of the same type as the sample to be tested (if there is no standard sample of the same type, other steel standards with similar composition can be selected) and place it in a crucible (2.9) containing 0.300±0.500g of tin particles (2.6), covering 1.500±0.005g of potential particles (2.5), and measure according to 5.5 in the same range or channel. Repeat enough times until a consistent reading is obtained. The blank value should be equal to the difference between the measured carbon content and the known carbon content of the standard sample. GB 4702. 14 -- 88
Record the minimum three readings, calculate the average value, and enter the average value into the analyzer with reference to the instrument manual. The instrument will then perform electronic compensation for the blank value when measuring the sample. 5.3 Analysis preparation
5.3.1 Check the instrument according to the instrument manual to make it in a normal and stable state. 5.3.2 Select and set the best analysis conditions.
5.3.3 Use standard sample skin flux to make two test tests according to 5.5.1 and 5.5.2 to determine whether the instrument is normal. 5.3.4 Weigh 1.000 g of standard samples with a carbon content of about 0.05%, and measure them according to 5.5. The result fluctuation should be within the range of +0.003%, otherwise the sensitivity of the instrument should be adjusted according to the instrument requirements. 5.4 Calibration test
5.4.1 According to the carbon content of the sample to be tested, select the corresponding bone program and channel, and select three standard samples of the same type (the carbon content of the sample to be tested should fall within the range of the carbon content of the selected three standard samples), and calibrate them in turn. The fluctuation of the results should be within the allowable range to confirm the linearity of the system, otherwise the linearity of the system should be adjusted according to the instrument manual. 5.4.2 For different ranges or channels, their blank values ​​should be measured and calibrated respectively. 5.4.3 When the analysis conditions change, such as when the instrument has not been preheated for 1 hour, and the blank values ​​of the oxygen source, exhaust gas or flux have changed, it is required to re-measure the blank value and calibrate it.
5.5 Determination
5.5,1 According to the carbon content range of the sample to be tested, select the best analysis conditions of the instrument respectively: such as the combustion integration time of the instrument, the setting conditions of the comparison level (or set value).
5.5.2 Place the weighed sample (5.1) in (2.9) which has been pre-filled with 0.500g tin particles (2.6), cover it with 1.500g tungsten particles (2.5), take the crucible with tongs and place it on the seat of the furnace, operate according to the instrument manual, start analysis and read the results. 6 Allowable difference
The difference in analysis results between laboratories should not be greater than the allowable difference listed in the following table. %
.0. 025
≥>0. 025-0, 070
Additional remarks:
This standard was drafted by Jilin Ferroalloy Factory.
This standard is mainly drafted by Chang Yanfu.
Allowance
White From the implementation of this standard, the original standard of the Ministry of Metallurgy YB582:65 "Metallic Chromium Chemical Analysis Method" will be invalid. This standard level mark GB4702.14-88I
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