JB/T 7948.1-1999 JB/T 7948.1-1999 Chemical analysis methods for melting fluxes Gravimetric determination of silicon dioxide content JB/T7948.1-1999 Standard download decompression password: www.bzxz.net

JB/T 7948.1..-1999
This standard is equivalent to "OCT22978.1~~22978.10-78 "Methods for chemical analysis of molten flux". This standard is an editorial revision of JB/T7948.1--95 "Methods for chemical analysis of molten flux", and its technical content has not changed. This standard replaces JB/T7948.1-95 from the date of implementation. This standard is proposed and managed by the National Technical Committee for Welding Standardization. The drafting unit of this standard: Harbin Welding Research Institute. The main drafters of this standard: Lin Kegong, Bai Shuyun. 348
Determination of silicon dioxide content by gravimetric method" revision. Revision of Mechanical Industry Standard of the People's Republic of China
Methods for chemical analysis of melted welding fluxesThe gravimetric method for determination of silicon dioxide content1Scope
JB/T 7948.1--1999
Represented by JB/T 7948. 1-95
This standard applies to the determination of silicon dioxide content in melted welding fluxes. Determination range 10.0%~50.0%This standard complies with GB/T1467-1978 "General Principles and General Provisions for Chemical Analysis Methods for Metallurgical Products" 2Cited 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 are subject to revision, 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 for Chemical Analysis Methods of Metallurgical Products 3 Method
The sample is melted with a mixed flux of potassium carbonate sodium and sodium tetraborate, leached with hydrochloric acid, heated and evaporated to dehydrate the silicic acid, filtered and burned to silicon dioxide. Then it is treated with oxyfluoric acid to volatilize and remove silicon in the form of silicon tetrafluoride. The percentage of silicon dioxide is calculated from the mass difference before and after the hydrofluoric acid treatment.
4 Reagents
4.1 Mixed flux: Grind and mix four parts of potassium carbonate sodium and two parts of sodium tetraborate (NazB,O,·H,O). 4.2 Hydrochloric acid (specific gravity 1.19).
4.3 Hydrofluoric acid (40%).
4.4 Methanol.
4.5 Sulfuric acid (1+1).
4.6 Hydrochloric acid (1+1).
4.7 Hydrochloric acid (5+95).
Iodic acid solution (10%).
Animal glue solution: Weigh 1g of animal glue and dissolve it in 100mL of boiling water. 5 Sample
The sample should pass through a 200-mesh screen. The sample is pre-dried at 105~110℃ for 1h and placed in a desiccator to cool to room temperature. 6 Analysis steps required
6.1 Quantity of determination
Three samples should be weighed for determination during analysis and the average value should be taken. Approved by Guohao Machinery Industry Bureau on June 24, 1999, and implemented on January 1, 2000
6.2 Sample quantitybZxz.net
Weigh 0.5000g of sample.
6.3 Determination
JB/T 7948.1--1999
6.3.1: Place the sample (6.2) in a platinum crucible containing 4g of mixed flux (4.1), mix, cover with 2g of mixed flux (4.1), and cover the crucible. Transfer to a high-temperature furnace at 1000℃±20℃ and melt for 30min. Take out and cool. 6.3.2 Use filter paper to clean the outer wall of the crucible, place it in a porcelain evaporating tube with a handle, cover with a tube, add 5ml of boric acid solution (4.8) and 50ml of hydrochloric acid (4.6), heat until the frit is dissolved, wash with water and take out the crucible. 6.3.3 Heat the solution (6.3.2) to evaporate to dryness, and cool slightly. Add 20ml of hydrochloric acid (4.2) and 20ml of methanol (4.4), and heat evaporate to dryness. Repeat the operation with hydrochloric acid (4.2) and methanol (4.4) once more, and cool. 6.3:4 Add 20 mL of hydrochloric acid (4.2) and 80 mL of hot water to the dry residue (6.3.3), heat to dissolve the salts, boil, and remove. Filter with medium-speed quantitative filter paper, wipe the precipitate on the evaporating blood wall with a wiper, then wash the evaporating dish and the precipitate with hot hydrochloric acid (4.7) 6 to 8 times, and then wash the precipitate with hot water 8 to 10 times. Save the precipitate (1). 6.3.5 Evaporate the filtrate (6.3.4) to dryness, add 35 mL of hydrochloric acid (4.2), heat to dissolve the salts, add 10 mL of animal glue solution (4.9), and keep warm at low temperature (about 50°C) for 10 minutes. Add 50 ml of hot water. Filter with medium-speed quantitative filter paper, wash the evaporating dish and the precipitate with hot hydrochloric acid (4.7) 6 to 8 times, and then wash the precipitate with hot water 8 to 10 times. Save the precipitate (2) and discard the filtrate. 6.3.6 Place the precipitates (1) and (2) in a platinum crucible, dry and incinerate, then transfer to a high-temperature furnace at 1000℃±20℃ and burn for 30min. Take out, cool slightly, and place in a desiccator to cool to room temperature. Weigh. Repeat the burning until constant weight. 6.3.7 Add 5~10 drops of sulfuric acid (4.5) and 5~8mL of hydrofluoric acid (4.3) to the solution, heat and evaporate until white smoke is eliminated. Transfer to a high-temperature furnace at 1000℃±20℃ and burn for 5min. Take out, cool slightly, and place in a desiccator to cool to room temperature. Weigh. Repeat the burning until constant weight. 7 Calculation of analysis results
Calculate the percentage of silicon dioxide according to formula (1): SiOz=
Wherein: m-
Mass of the sample before hydrofluoric acid treatment and the precipitate, g; mass of the sample after hydrofluoric acid treatment and the residue·g: m. -Sample amount+g.
8 Allowable difference
The difference between the parallel determination results should not be greater than the allowable difference listed in Table 1. Table 1 Allowable difference
Silicon dioxide content
10. 0-- 20, 0
>20.0~50.0
Allowable difference
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