JB/T 7948.11-1999 This standard is equivalent to ΓOCT 2978.1~.10-78 "Methods for chemical analysis of melting flux". This standard is a revision of JB/7948.11-95 "Methods for chemical analysis of melting flux - Determination of sulfur content by combustion-iodine titration". During the revision, only editorial changes were made according to relevant regulations, and its technical content has not changed. This standard is applicable to the determination of sulfur content in melting flux, with a determination range of 0.02%~0.20%. This standard was first issued in 1985 as GB 5292.11-85 and was adjusted to JB/T 7948.11-95 in April 1996. JB/T 7948.11-1999 Methods for chemical analysis of melting flux - Determination of sulfur content by combustion-iodine titration JB/T7948.11-1999 Standard download decompression password: www.bzxz.net

JB/T 7948.11--1999
This standard is equivalent to the chemical analysis method of melting flux in TOCT22978.1~~2297.8.10-78≤. This standard only makes editorial changes to the chemical analysis method of melting flux in JB/T7948.11-95, and its technical content remains unchanged. This standard replaces JB/T7948.11-95 from the date of implementation. This standard is proposed and managed by the National Welding Standardization Technical Committee. The drafting unit of this standard: Harbin Welding Research Institute. The main drafters of this standard: Lin Kegong, Bai Shuyun. Revision of the determination of sulfur content by combustion-sulfurization method. Revision 389
Standard of the Machinery Industry of the People's Republic of China
Methods for chemical analysis of melted welding fluxesThe direct combustion-iodimetric method fordetermination of sulfur contentThis standard applies to the determination of sulfur content in melted welding fluxes. Determination range: 0.02% to 0.20%. JB/T 7948.11---1999
Replaces JB/T7948.11-95
This standard complies with GB/T1467-1978 "General Principles and General Provisions for Chemical Analysis Methods of Metallurgical Products". 2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T1467-1978 General Principles and General Provisions of the Standard for Chemical Analysis Methods of Metallurgical Products 3 Method Summary
This method is based on the combustion of the sample in a high-temperature furnace at 1250-1300℃ with oxygen. The generated sulfur dioxide is absorbed by water in the absorber to generate sulfurous acid, which is then titrated with potassium iodate standard solution using starch as an indicator. The percentage of sulfur is obtained by this. 4 Reagents
4.1 Starch solution: Weigh 16g of starch and dissolve it in an appropriate amount of boiling water, cool it, and dilute it to 1000mL with water. Add 1000mL of glycerol and mix it. Store in a brown bottle.
4.2 Starch solution: Take 50mL of starch solution (4.1), add 3300mL of water, and slowly add 20ml of sulfuric acid (specific gravity 1.84). 4.3 Potassium iodate standard solution: Weigh 0.05g potassium iodate, 10g potassium iodide and 0.2g potassium hydroxide and dissolve in appropriate amount of water, transfer to a 1000mL volumetric flask, dilute to scale with water and mix well. Calibration: The titer of potassium iodate standard solution is determined based on the standard flux with known sulfur content. The analytical conditions of the standard sample and the sample should be the same.
Calculate the sulfur titration of potassium iodate standard solution (4.3) according to formula (1): Sstandard (%Xm
Wherein: Sstandard (%) ~-the percentage of sulfur in the standard sample: V
The volume of potassium iodate standard solution (4.3) consumed during titration, mI: T-the amount of sulfur equivalent to 1mL potassium iodate standard solution (4.3), g; m-the amount of standard sample, g.
Approved by the State Machinery Industry Bureau on June 24, 1999 390
Implemented on January 1, 2000
5 Instruments
The sulfur determination device is shown in Figure 1.
JB/T7948.11-1999
1-Equipped with 1. Oxygen cylinder with pressure reducing valve; 2. Selected gas cylinder [containing potassium permanganate solution (4%) dissolved in potassium hydroxide solution (40%)], 3. Drying tower (filled with calcium oxide); 4. Tubular furnace; 5. Porcelain tube (inner diameter 20~22mm, length 750~800mm); 6. Sulfur determination absorber: 7. Comparison container 8. Burette Figure 1 Sulfur determination device diagram
6 Sample
The sample should pass through a 200-mesh sieve. Pre-bake at 105~110℃ for 1h, place in a desiccator and cool to room temperature. 7 Analysis steps
7.1 Determination quantity
Three samples should be weighed for determination during analysis and the average value should be taken. 7.2 Sample quantity
Weigh 0.5 000g sample.
7.3 Determination
7.3.1 Preparation before determination: Before analyzing the sample or standard sample, check the porcelain tube for the presence of reducing substances. Add 70-80ml starch solution (4.2) to the absorber and comparator respectively, and add potassium iodate standard solution (4.3) from the burette until the solution turns light blue. Open the valve and let in oxygen. If the color of the solution in the absorber disappears, add potassium iodate standard solution (4.3) until the blue color of the solution no longer disappears (compare with the color of the solution in the comparator).
7.3.2 Place the sample (4.2) in a porcelain boat, send it to the high temperature zone of the tubular furnace, and quickly plug it with the rubber stopper. At a rate of 4-5 bubbles/s Oxygen is introduced at a certain degree. When the gas in the furnace enters the absorber and the blue color of the solution begins to fade, immediately titrate with potassium iodate standard solution (4.3) (the solution in the absorber should always remain blue), and finally titrate until the color of the solution in the absorber and the comparator is consistent and stable. 8 Calculation of analysis results
Calculate the percentage of sulfur according to formula (2):
The volume of potassium iodate standard solution (4.3) consumed during titration, mL; Wu Zhong: -
9Allowance
1mL potassium iodate standard solution (4.3) is equivalent to the amount of sulfur * g; sample size + name.
The difference between parallel determination results should not be greater than the allowable difference listed in Table 1. (2)bZxz.net
0. 02 ~~0. 05
>0. 05~0. 10
>0.10~0.20
JB/T 7948.11--1999
Table 1 Allowable difference
Allowable difference
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