JB/T 7948.4-1999 This standard is equivalent to ΓOCT 2978.1~.10-78 "Methods for chemical analysis of melting flux". This standard is a revision of JB/7948.4-95 "Methods for chemical analysis of melting flux - Determination of alumina content by EDTA volumetric method". 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 alumina content in melting flux, with a determination range of 1.00%~40.0%. This standard was first issued in 1985 as GB 5292.4-85 and was adjusted to JB/T 7948.4-95 in April 1996. JB/T 7948.4-1999 Methods for chemical analysis of melting flux - Determination of calcium oxide and magnesium oxide by EDTA volumetric method JB/T7948.4-1999 Standard download decompression password: www.bzxz.net

JB/T7948.4--1999
This standard is equivalent to IOCT22978.122978.10--78 "Methods for Chemical Analysis of Melting Fluxes". This standard is a revision of JB/T7948.4--95 "Methods for Chemical Analysis of Melting Fluxes - EDTA Volumetric Method for Determination of Alumina Content". During the revision, only editorial changes were made to the standard, and its technical content remained unchanged. This standard replaces JB/T7948.4--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 and Bai Shuyun. 359
1 Scope
Standard of the Machinery Industry of the People's Republic of China
Methods for chemical analysis of melted welding fluxesThe EDTA volumetric method for determinationof aluminium oxide content
JB/T7948.4-1999
Replaces JB/T7948.4--95
This standard applies to the determination of aluminium oxide content in melted welding fluxes. The determination range is 1.00% to 40.0%. 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 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 of the standard for chemical analysis methods of metallurgical products JB/T7948.2—1999 Chemical analysis methods for melting flux Potentiometric titration method for determination of manganese oxide content 3 Method summary
This method is based on the formation of a colorless complex between aluminum ions and EDTA at pH 5~~6. Using dithiol as an indicator, the excess EDTA is back-titrated with zinc acetate solution. The percentage of aluminum oxide is thus measured. Interfering elements such as iron and manganese need to be separated in advance. 4 Reagents
4.1 Ammonium acetate.
Sulfuric acid (specific gravity 1.84).
Nitric acid (specific gravity 1.42).
Glacial acetic acid.
Ammonium hydroxide (specific gravity 0.88). Www.bzxZ.net
Hydrogen peroxide (30%).
Hydrochloric acid (1+1).
Sodium hydroxide solution (20%)
Sodium hydroxide solution (10%).
Ammonium chloride solution (20%).
Ammonium chloride washing solution (1%). Neutralize with ammonium hydroxide (4.5) until the methyl red indicator (4.14) changes color. [Use methyl red solution (4.14) as indicator].
Sodium sulfide solution (5%).
Approved by Guoxiang Machinery Industry on June 24, 1999
Implemented on January 1, 2000
JB/T7948.4—1999
4.13 Acetic acid-ammonium acetate buffer solution: Weigh 500g of ammonium acetate (4.1) and dissolve it in 1000mL of water. Add 20mL of glacial acetic acid (4.4) and mix well.
4.14 Methyl red solution: weigh 0.1g methyl red and dissolve it in 100mL ethanol (99.5%). 4.15 Dithiol solution: weigh 0.04g dithiol and dissolve it in 100mL ethanol (99.5%). Prepare when needed. 4.16 Aluminum standard solution: weigh 0.5000g metal aluminum powder (99.99%) and place it in a 250mL conical cup, add 30mL hydrochloric acid (4.7), heat to dissolve, wait for the action to stop, add hydrogen peroxide (4.6) dropwise until it is completely dissolved, boil, and cool. Transfer to a 1000mL volumetric flask, dilute to the mark with water, and mix well. This solution contains 0.5mg aluminum in 1mL. 4.17 Zinc acetate standard solution: weigh 2:74g zinc acetate [Zn(CHsCOO)2·2H2O] and dissolve it in 500mL water, add 5mL glacial acetic acid (4.4), transfer to a 1000mL volumetric flask, dilute to the mark with water, and mix well. 4.18 Disodium ethylenediaminetetraacetate (EDTA) standard solution: weigh 4.5g disodium ethylenediaminetetraacetate (C1oH4N.0:Na2·HO) and dissolve it in 1 000mL water.
Calibration: Take three portions of 10.00 mL aluminum standard solution (4.16) and place them in 250 mL conical cups respectively. Add 50 mL water and 25.00 mL of LEDTA standard solution (4.18) and 1 Q mL of sodium hydroxide solution (4.9). Add hydrochloric acid (4.7) to neutralize the solution to change the Congo red test paper from red to blue. Then add 20 mL of acetic acid-ammonium acetate buffer solution (4.13), boil for 2-3 minutes, and cool. Add 1-1.5 mL of disulfide indicator (4.15) and use zinc acetate standard solution (4.17) to fully adjust until the solution changes from yellow to pink. Calculate the titration degree of EDTA standard solution (4.18) on lead oxide according to formula (1): mX1. 889 5
Wherein: m---the amount of aluminum equivalent to the aluminum standard solution (4.16) transferred, g; VI---the volume of EDTA standard solution (4.18) added, mL: V
(1)
The average volume of zinc acetate standard solution (4.17) consumed during titration (if the extreme difference exceeds 0.10mL, it should be recalibrated), mL:
-1mLEDTA standard solution (4.18) equivalent to the amount of aluminum oxide + g; 1.889 5
The conversion factor of lead to lead oxide;
K--the coefficient of zinc acetate standard solution (4.17) to EDTA standard solution (4.18). The method is as follows: take three portions of 10.00 mL of LEDA standard solution (4.18), place them in 250 mL conical cups respectively, add 50 mL of water and 10 mL of sodium oxyammonium solution (4.9), add hydrochloric acid (4.7) dropwise to neutralize the solution until the Congo red test paper changes from red to blue, add 20 mL of acetic acid-ammonium acetate buffer solution (4.13), add 1 to 1.5 mL of dithiol trace indicator (4.15), and titrate with zinc acetate standard solution (4.17) until the solution changes from yellow to pink.
Calculate the coefficient of converting zinc acetate standard solution (4.17) to EDTA standard solution (4.18) according to formula (2): a
Wherein: Vs—
5 Sample
The volume of EDTA standard solution (4.18) transferred, mL; + (2)
The average volume of zinc acetate standard solution (4.17) consumed during titration (if the extreme difference exceeds 0.10mL, it should be recalibrated), mL.
The sample should pass through a 200-mesh sieve. Pre-dry at 105~110℃ for 1h and place in a desiccator to cool to room temperature. 6 Analysis steps
6.1 Determination quantity
Three samples should be weighed for determination during analysis and the average value should be taken. 6.2 Sample volume
Pipette 50.00mL of test solution.
JB/T7948.4—1999
Weigh 0.5000g of sample and operate according to steps 7.3.1 to 7.3.5 of JB/T7948.2--1999. 6.3 Determination
6.3.1 Place the test solution (6.2) in a 300mL beaker, add 5mL nitric acid (4.3), carefully add 8mL sulfuric acid (4.2) and mix, cover with table III, heat and evaporate until white smoke appears, cool slightly, rinse the beaker and table III with water, mix, heat and evaporate again until white smoke appears, cool, rinse the beaker and table III with water, mix. Add 10mL hydrochloric acid (4.7) and 150mL water, heat until the salts are dissolved. Add 10mL of ammonium hydroxide solution (4.10): heat to 70~80℃, add 1 drop of methyl red indicator (4.14), and use ammonium hydroxide (4.5) to neutralize the solution from red to yellow, with an excess of 2~3 drops. Keep warm on a low-temperature electric stove for 3~5min, do not boil. Filter with medium-speed filter paper, wash the beaker and precipitate 2~4 times with hot ammonium chloride washing solution (4.11). Save the filtrate.
6.3.2 Rinse the precipitate in the funnel with hot water into the original beaker, add 20mL of hot hydrochloric acid (4.7), and heat until the precipitate dissolves. Precipitate again with ammonium hydroxide (4.5), filter with the original filter paper again, wash the beaker 2~3 times and the precipitate 5~6 times with hot ammonium chloride washing solution (4.11). Collect the two filtrates in a 500mL volumetric flask for the determination of calcium oxide and magnesium oxide. 6.3.3 Rinse the precipitate in the funnel into the original beaker with hot water, and then use 20 mL of hot hydrochloric acid (4.7) Wash the filter paper, and then wash the burning paper with hot water for 10 to 12 times. The total volume of the solution is 60 to 70 mL. Cover the nozzle, heat to dissolve the precipitate, and rinse the wall of the cup with water. Add 0.5 mL of sodium sulfide solution (4.12), and neutralize the solution with hot sodium hydroxide solution (4.8) until the Congo red test paper changes from blue to red, with an excess of 30 to 40 mL. Boil the solution for 3 to 4 minutes and cool. Transfer to a 250 mL volumetric flask, dilute with water to the scale, and mix. Dry filter with medium-speed filter paper. 6.3.4 Transfer part of the solution (6.3.3) and add EDTA standard solution (4.18) according to the values ​​in Table 1 according to the different aluminum contents. Table 1 Volume of EDTA added for different aluminum contents
Alumina content
>5.0～20.0
>20.0-~30.0
>30.0~40.0
Amount of filtrate taken
Amount of EDTA added
Add salt (4.7) to neutralize the solution until the Congo red test paper changes from red to blue, add 20mL acetic acid-ammonium acetate buffer solution (4.13), heat and boil for 2-~3min, and cool. Add 1~1.5mL disulfide indicator (4.15), and titrate with zinc acetate standard solution (4.17) until the solution changes from yellow to pink.
7 Calculation of analysis results
Calculate the percentage of aluminum oxide according to formula (3): (VV,K)T
Al,O3=
Wherein: Vi--the volume of EDTA standard solution (4.18) added, mL; Vz--the volume of zinc acetate standard solution (4.17) consumed during titration, mL; K--the coefficient of converting zinc acetate standard solution (4.17) into EDTA standard solution (4.18); T-
8 Allowable difference
--the amount of aluminum oxide equivalent to 1 mL of EDTA standard solution (4.18), the amount of sample equivalent to the pipetted test solution (6.3.4) in g. The difference between the parallel determination results should not be greater than the allowable difference listed in Table 2. 362
（3）
Aluminum plating
1.00~2.00
>2. 00 ～4. 00
>4. 00~10.00
>10. 00-~20. 00
>20. 00~40. 00
JB/T 7948.4
Table 2 Allowable difference
Allowable difference
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