JB/T 7948.6-1999 JB/T 7948.6-1999 Chemical analysis method for melting flux Determination of calcium fluoride content by pyrolysis method JB/T7948.6-1999 Standard download decompression password: www.bzxz.net

JB/T7948.6--1999
This standard is equivalent to JB/T22978.1~22978.10-78 "Chemical Analysis Method for Melting Flux". This standard is an editorial revision of JB/T7948.6--95 "Chemical Analysis Method for Melting Flux", and its technical content has not changed. This standard replaces JB/T7948.6--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 Shuchou. Revision of the determination of calcium oxide content by thermal decomposition method. Only 367
Standard of the Machinery Industry of the People's Republic of China
Methods for chemical analysis of melted welding fluxesThe pyrolytic method for determination of calcium fluoride content1 Scope
JB/T 7948.6--1999www.bzxz.net
Replaces JB/T7948.6-95
This standard applies to the determination of calcium fluoride content in melted welding fluxes. The determination range is 3.00% to 40.0%. This standard complies with the general principles and general provisions of GB/T1467-1978 Standard 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 version of the following standards. GB/T1467-197.8 General Principles and General Provisions of Standards for Chemical Analysis Methods of Metallurgical Products 3 Method Summary
This method is based on the fact that in the presence of a catalyst, calcium fluoride is decomposed by water vapor at 1300~1350℃ to generate hydrofluoric acid, which is carried into an absorber together with water vapor by air or oxygen flow and titrated with sodium hydroxide solution. The amount of calcium fluoride is thereby measured. 4 Reagents
4.1 Lead oxide (burned at 1100℃ for 1h). 4.2 Sodium hydroxide solution (20%).
4.3 Mixed indicator: Weigh 0.125g methyl red and 0.083g methylene blue, and dissolve in 100ml ethanol (99.5%). Store in a brown bottle.
4.4 Sodium hydroxide standard solution: Weigh 0.8g of sodium hydroxide and dissolve it in an appropriate amount of water, transfer it to a 1000mL volumetric flask, dilute it to the mark with water, and mix it. The concentration of this solution is about 0.02N. Calibrate it when needed. Calculate the titer of sodium hydroxide standard solution (4.4) to calcium fluoride according to formula (1): 39.04XN
Wherein: N—
the equivalent concentration of sodium hydroxide standard solution (4.4), T——the amount of calcium fluoride equivalent to 1mL of sodium hydroxide standard solution (4.4), g; 39.04-
gram equivalent of calcium fluoride.
The measuring device is shown in Figure 1.
Approved by the State Machinery Industry Bureau on June 24, 1999 368
Sold on January 1, 2000
JB/T7948.6-1999
1-Purification washing bottle [with sodium hydroxide solution (4.2)], 2-spherical tube (with glass wool inside), 3-stainless steel tube (with inner diameter of 18mm and length of 220mm): 4--stainless steel tube (with inner diameter of 18mm and length of 220mm) 10mm in diameter) 5-Erlenmeyer flask for water vapor; 6-Electric heater; 7-pyrometer, 8-porcelain boat (pre-burned at 9001000℃ for 4-5h); 9-Tube furnace (inclined toward the absorber) 10-porcelain tube or quartz tube (inner diameter is 20-22mm): 11-Water cooler, 12 absorber Figure 1 Calcium hydride determination device diagram
6 Sample
The sample should pass through a 200 mesh screen. Pre-bake at 105~110C 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 0.2000g of sample.
7.3 Determination
Put the sample (7.2) in a porcelain boat containing 0.2~0.4g of aluminum oxide (4.1), mix it, and send it into a porcelain tube or quartz tube at a furnace temperature of 1300℃±10℃. Plug the porcelain tube tightly with a rubber stopper. Send water vapor through branch pipe 3, and at the same time, pass air or oxygen at a rate of 3~5 bubbles/s. The hydrofluoric acid generated during high-temperature hydrolysis enters the absorber 12 containing 50mL of water and 5~6 drops of indicator (4.3), and titrates with sodium hydroxide standard solution (4.4) until the solution changes from lilac purple to green, and keeps it for 2 minutes. 8 Calculation of analysis results
Calculate the percentage of calcium fluoride according to formula (2): CaF.
Wherein: V—
The volume of sodium hydroxide standard solution (4.4) consumed during titration, mLT——The amount of calcium fluoride equivalent to 1mL sodium hydroxide standard solution (4.4), g sample volume g.
9 Allowable difference
The difference between parallel determination results should not be greater than the allowable difference listed in Table 1. (2)
Calcium fluoride content
>5. 0-~10. 0
>10. 0~~20. 0
>20.0~40. 0
JB/T 7948-6—1999
Table 1 Allowable difference
Allowable difference
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