GB/T 8454-1987 Determination of ferrous iron content in reduced ilmenite powder for welding electrodes
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National Standard of the People's Republic of China
Determination of ferrous iron content in reduced ilmenite powder for welding rod This standard applies to the determination of ferrous iron content in reduced ilmenite powder for welding rod. Determination range: above 1%. This standard complies with GB1467-78 "General Principles and General Provisions of Standards for Chemical Analysis Methods of Metallurgical Products". 1 Method Summary
UDC 669. 15' 295
GB 8454-87
The determination is carried out in two steps:
1.1 In the absence of air, the sample is dissolved with ammonium fluoride, sulfuric acid and hydrochloric acid, and titrated with potassium dichromate standard solution to calculate the percentage of metallic iron and ferrous iron (A).
1.2 Accurately add an excess of ferric chloride solution to the sample to extract the metallic iron, then use the standard solution of mercurous nitrate to back-titrate the remaining trivalent iron in the filtrate and calculate the percentage of metallic iron (). The difference between the two determination results (AB) is the percentage of ferrous iron. 2 Reagents and materials bZxz.net
2.1 Ammonium fluoride.
2.2 Sulfuric acid (1+1).
2. 3 Hydrochloric acid (p 1. 19 g/ml).
2.4 Saturated boric acid solution.
2. 5 Perchloric acid (1+1).
2. 6 Phosphoric acid (p 1. 70 g/ml).
2.7 Sodium diphenylamine sulfonate solution (0.5%). 2.8 Potassium dichromate standard solution [C (K, Cr.0) -0.008335ma1/17; Weigh 4.9035g potassium dichromate base reagent, dissolve in water, transfer to a 2000ml volumetric flask, dilute to scale with water, and mix. 2.9 Ferric chloride solution (10%): Weigh 100g ferric chloride (FeCl6H0), dissolve in 600ml water, filter, dilute to 1 000ml with water, and shake.
2.10 Iron standard solution: Weigh 0.5000g pure iron powder (99.9% or more), add 20ml hydrochloric acid (2.3), 5ml nitric acid (p1.42g/ml), heat to dissolve, add water to a volume of about 100ml, heat to boil, drive out nitrogen oxides, cool, weigh into a 250ml volumetric flask, dilute to scale with water, and shake well. This solution contains 2.00 mg iron per ml. 2.11 Ammonium thiocyanate solution (20%).
2.12 Mercurous nitrate standard solution C[Hg(NO,)·2H,O]=D.025mol/1. 2.12.1 Preparation Weigh 14g mercurous nitrate and add it to 200ml water and 20ml nitric acid (p1.42g/ml). After stirring and dissolving, add 1g urea, stir thoroughly to remove nitrogen oxides, filter into a 1000ml volumetric flask, dilute with water to the scale, and shake. Store in a dark place. 2.12.2 Calibration Take 25,000ml of iron standard solution (2.10), add water to a volume of about 100ml, add 10ml sulfuric acid (2.2), 15ml ammonium thiocyanate solution (2.11), and titrate with mercurous nitrate standard solution (2.12.1) until the solution is colorless. Calculate the titer (T) of mercurous nitrate to metallic iron according to the following formula. Approved by the Ministry of Metallurgical Industry of the People's Republic of China on 19B7-12-03 and implemented on 1989-01-01
In the formula, T_
GB 8 454-87
The titer of mercurous nitrate standard solution for metallic iron, mg/ml, m—-the mass of iron (Fe+) in the iron standard solution, mg; V—the volume of mercurous nitrate standard solution consumed in the titration, ml. (1)
2.13 Acid-washed asbestos: Burn chemically pure acid-washed asbestos at 1000°C for 2~3h, cool it, add hydrochloric acid (1+1) to boil it, filter it with glass filter cloth, wash it with 5% hydrochloric acid until there is no trivalent iron ion (check it with 5% thiocarbamide until it does not show red), then wash it with water until there is no chloride ion (check it with 1% silver nitrate until it does not show white turbidity), and place it in a conical flask for later use. 3 Instruments
3.1 Electromagnetic stirrer.
3.2 Filter pump.
4 Analysis steps
4.1 Determination of the total amount of metallic iron and ferrous iron
4.1.1 Weigh 0.2000g of sample (200 mesh), place in a 300ml conical flask, add 1g of ammonium fluoride (2.1), 25ml of sulfuric acid (2.2) and 15ml of hydrochloric acid (2.3), cover the bottle, place on a preheated medium-temperature electric hot plate, heat to dissolve for 30~40min (almost smoking). 4.1.2 Remove and cool slightly, add 10ml of saturated acid solution (2.4) and 10ml of water, heat to boiling, remove, immediately add 10ml of perchloric acid (2.5), shake the hook, add 70ml of water, and cool under running water. 4.1.3 Add 5 ml phosphoric acid (2.6) and 3 drops of sodium diphenylamine sulfonate solution (2.7), and titrate with potassium dichromate standard solution (2.8) until the solution turns purple. Record the number of liters (V) of potassium dichromate standard solution consumed. 4.2 Determination of metallic iron
4.2.1 Weigh 0.5000 g of sample (200 ml), place it in a dry 150 ml conical flask, add 25.00 ml of ferric chloride solution (2.9), add a magnetic core, plug it with rubber, and stir it on an electromagnetic stirrer for 30 minutes. 4.2.2 Remove it, filter it with a funnel covered with washed asbestos (2.13), wash the conical flask and filter thoroughly with water, transfer the filtrate into a 250 ml volumetric flask, dilute it to the mark with water, and shake it. 4.2.3 Weigh 50.00ml solution (4.2.2) into a 300ml conical flask, add 10ml sulfuric acid (2.2) and 15ml ammonium thiocyanate solution (2.11), and titrate with standard mercuric nitrate solution (2.12) until the solution becomes colorless. Record the milliliters of standard mercuric nitrate solution consumed in the titration ().
4.2.4 Blank test solution: Transfer 25.00ml ferric chloride solution (2.9) into a 250ml volumetric flask, dilute to the mark with water, and shake well. Proceed as in (4.2.3). Record the milliliters of standard mercuric nitrate solution consumed (V.). 5 Calculation of analytical results
5.1 The percentage content of metallic iron and ferrous iron combined (4) is calculated according to the following formula: Fe(%)=VX0.002 792 5 × 100
The volume of potassium dichromate standard solution (2.8) consumed in titrating the total amount of metallic iron and ferrous iron, ml;
0.0027925—1 ml of potassium dichromate standard solution (2.8) is equivalent to the amount of iron?8;—the amount of sample.
5.2 The percentage of metallic iron (B) is calculated according to the following formula: (V,-V) - T
Fe(%)--
m.×2×1000
(V,-V)· T
m，X200
GB-8454—87
Wherein: V,--——the volume of the standard solution of mercurous nitrate consumed by titrating the remaining ferric chloride (4.2.3) in the sample extraction solution, ml; V——the volume of the standard solution of mercurous nitrate consumed by titrating the blank test solution (4.2.4), ml; T——the titration degree of the standard solution of mercurous nitrate on metallic iron, mg/ml; m,——the amount of sample, B.
5.3 The percentage of ferrous iron is calculated as follows: Fe'+(%) = A- B
Wherein: A is the percentage of metallic iron and ferrous iron combined, and B is the percentage of metallic iron.
Note: The factor for converting ferrous iron to ferrous oxide is 1.2865. 6 The difference in the analysis results between laboratories should not be greater than 0.45%. Note: The analysis results should be the average of more than three determinations. Additional notes:
This standard is under the technical coordination of the Iron and Steel Research Institute of the Ministry of Metallurgical Industry of the People's Republic of China. This standard was drafted by the Iron and Steel Research Institute of the Ministry of Metallurgical Industry. The main drafters of this standard are Hu Shufen, Zheng Lufei, and Xu Sujian. The level of this standard is marked as GB8454-8714
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