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This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 3045-2003 Abrasive grains - Chemical analysis of silicon carbide, and the following main technical changes have been made with respect to GB/T 3045-2003:
——the applicable scope is modified (see Clause 1 of this standard; Clause 1 of Edition 2003);
——the preparation method for specimen is modified and improved (see 3.1 and 4.2 of this standard; Clause 3 of Edition 2003);
——the method is modified and improved for determining the silicon dioxide by spectrophotometry, and the method is added for determining the silicon dioxide by potassium fluosilicate volumetric (see 3.2.2 of this standard; Clause 4 of Edition 2003);
——the method is modified and improved for determining silica by spectrophotometric, and the method is added for determining silica by the gas volumetric (see 3.3.2 of this standard; Clause 5 of Edition 2003);
——the method is added for determining the free and total carbon by infrared absorption (see 3.4.2 and 4.3.2 of this standard);
——the determination is added for loss on acid treatment (LAT) of specimen (see 3.5 of this standard);
——the method is added for determining the ferric oxide and aluminium oxide by atomic absorption spectrometry (AAS) (see 3.7.2 and 3.8.2 of this standard);
——the method is modified and improved for determining the calcium oxide and magnesium oxide by atomic absorption spectrometry (AAS) (see 3.9.2 of this standard; Clause 12 of Edition 2003);
——the method is added for determining the ferric oxide, aluminium oxide, calcium oxide, and oxidation magnesium by inductively coupled plasma-atomic emission spectrometry (ICP-AES) method (see 3.10 of this standard).
This standard has been redrafted and modified in relation to ISO 9286: 1997 Abrasive grains and crude - Chemical analysis of silicon carbide.
This standard is changed largely from ISO 9286: 1997 in structure; the comparison between this standard and ISO 9286: 1997 in clause and subclause numbers is listed in Annex A.
Technical deviations between this standard and ISO 9286: 1997 and their reasons are as follows:
——the adjustments of technical difference are made for the normative references in this standard so as to adapt to the technical conditions in China. The adjustment is mainly reflected in Clause 2 "Normative references" with the specific adjustments as follows:
● ISO 9138:1993 has been replaced by GB/T 4676 which is modified in relation to the international standard;
——in ISO 9286:1997, the silicon dioxide is determined by the potassium fluosilicate volumetric method, the silica is determined by the gas volumetric method; in this standard, in addition to modifying the use of the above-mentioned methods, the spectrophotometry is also added, in order to adapt to the detection of low-content specimens;
——in ISO 9286:1997, the free carbon and total carbon are determined by gravimetric absorption or coulometric method; in this standard, in addition to modifying the use of the gravimetric absorption method, infrared absorption and loss on ignition method are added to determine free carbon, and infrared absorption method is added to determine total carbon;
——the triacid treatment gravimetric method is added to determine silicon carbide in this standard;
——the method is added to determine the contents of ferric oxide, aluminium oxide, calcium oxide, and magnesium oxide by inductively coupled plasma-atomic emission spectrometry;
——the determination is added for other chemical components in silicon carbide crude;
——Annex A to the international standard is deleted, as it only indicates other methods that may be used, which are already partly provided in the text of this standard;
——Annex B to the international standard is deleted, it specifies the tolerance of silicon carbide chemical analysis due to changes in testing technology, which is specified in the text of this standard.
The following editorial modifications have been made in this standard:
——the standard name is revised as Conventional abrasive - Chemical analysis of silicon carbide.
This standard was proposed by China Machinery Industry Federation.
This standard is under the jurisdiction of the National Technical Committee 139 on Grinding Material and Grinding Apparatus of Standardization Administration of China (SAC/TC 139).
The previous editions of this standard are as follows:
——GB/T 3045-1989, GB/T 3045-2003.
Conventional abrasive - Chemical analysis of silicon carbide
1 Scope
This standard specifies the determination methods of silicon dioxide, free silicon, free carbon, loss on acid treatment, total carbon, silicon carbide, ferric oxide, aluminium oxide, calcium oxide and magnesium oxide in silicon carbide abrasives and crudes.
This standard is applicable to the determination of chemical composition of abrasives and crudes with silicon carbide content of not less than 95 %.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 4676 Abrasive grains - Sampling and splitting (GB/T 4676-2003, ISO 9138: 1993, MOD)
3 Analysis of surface impurities
This clause is applicable to the analysis of surface impurities in the original particle size state of abrasive or after the crude is crushed to a certain particle size.
3.1 Preparation of sample
3.1.1 Abrasives with original particle size state
Take the sample according to GB/T 4676 and divide it to 50 g ~ 60 g, dry it in an oven at (110 ± 5) ℃ for 1 h, take it out, put it in a desiccator, and then cool it for later use.
3.1.2 Crudes
Take statistically representative crudes according to GB/T 4676, crush them until they can completely pass through a 2 mm sieve, mix well, and divide them into 50 g ~ 60 g by quartering. Continue to grind with a steel mortar until all pass through a 355 μm sieve. Attract out the iron brought in during the crushing by a magnet with an attraction of 9.8 N ~ 14.7 N. Mix well, put it into a specimen bag, dry it in the oven at 105 ℃ ~ 110 ℃ for 1 h, take it out, put it into the desiccator, and cool it for later use.
If there are strict requirements for the determination of ferric oxide, separate samples shall be prepared for the determination of ferric oxide according to the following methods: take statistically representative crudes, crush them until they all pass through the 2 mm sieve, mix well, and divide them into 50 g ~ 60 g by quartering. Then grind it by a corundum mortar until all pass through a 500 μm sieve, mix well, and divide it into 20 g ~ 25 g by quartering. Continue to grind it by the corundum mortar until all pass through the 355 μm sieve, mix well, put it into a sample bag, dry it in the oven at 105 ℃ ~ 110 ℃ for 1 h, take it out, put it into the desiccator, and cool it for later use.
3.2 Determination of silicon dioxide
3.2.1 Spectrophotometry
3.2.1.1 Principle
Treat the specimen with sodium chloride - hydrochloric acid - hydrofluoric acid to dissolve silicon dioxide, add ammonium molybdate to generate silicomolybdic heteropoly acid, and then use 1, 2, 4- acid reducing agent to reduce the silicomolybdic heteropoly acid to molybdenum blue, and determine its absorbance at the wavelength of 700 nm.
3.2.1.2 Reagents or materials
Unless otherwise specified, only the recognized analytical reagents and distilled water or deionized water or water with equivalent purity shall be used during the analysis.
3.2.1.2.1 Hydrochloric acid: (1+1), (1+4).
3.2.1.2.2 Aqueous ammonia (1+4): Dilute concentrated aqueous ammonia (with the density of 0.90 g/cm3) with water at a volume ratio of 1:4 and it shall be freshly prepared.
3.2.1.2.3 Hydrofluoric acid: (1+1).
3.2.1.2.4 Sodium chloride solution (10%).
3.2.1.2.5 Aluminium chloride solution (45%): Weigh 90 g of aluminium chloride hexahydrate, dissolve it in water, and dilute it to 200 mL with water.
3.2.1.2.6 Ammonium molybdate solution (5%): Weigh 5 g of ammonium molybdate and dissolve it in water, dilute it to 100 mL with water, stand it for 24 h and then filter for use; if precipitation appears, it shall not be used.
3.2.1.2.7 Tartaric acid solution (10%).
3.2.1.2.8 1, 2, 4-acid solutions (0.15%): Weigh 0.15 g of 1,2.4-acid (1-amino-2-naphthol-4-sulfonic acid), dissolve it in 20 mL of sodium sulfite solution (7%) and then mix it with 180 mL of sodium sulfite solution (10%). The shelf life of this solution is two weeks.
3.2.1.2.9 P-nitrophenol indicator (0.2% ethanol solution): Weigh 0.2 g of p-nitrophenol and dissolve it in 95% ethanol and dilute it to 100 mL with ethanol.
3.2.1.2.10 Silicon dioxide standard solution: 0.05 mg/mL.
Weigh 0.100 0 g of silicon dioxide (high purity reagent) which has been ignited at 1,000 ℃ and place it in a platinum crucible, carefully mix with 2 g of anhydrous sodium carbonate (reference reagent), cover it with 0.5 g of anhydrous sodium carbonate (reference reagent), put into a high-temperature furnace and melt at 850 ℃ ~ 900 ℃ for 20 min, take it out, cool it, clean the outer wall of the crucible, leach the mixture out with hot water into a polyethylene beaker, transfer to a 1,000 mL volumetric flask after cooling, dilute to the scale with water and shake well, and immediately move into a clean and dry plastic bottle for storage. 1 mL of this solution contains 0.1 mg silicon dioxide.
Pipette 50 mL of the above 0.1 mg/mL silica solution into a 100 mL volumetric flask containing 10 mL of hydrochloric acid (1+4), dilute to the scale with water and shake well, and this solution is silicon dioxide standard solution. 1 mL of this solution contains 0.05 mg silicon dioxide.
3.2.1.2.11 Blank solution: Add 1 mL of sodium chloride solution (3.2.1.2.4), 3 mL of (1+1) hydrochloric acid (3.2.1.2.1), 3 mL of hydrofluoric acid (3.2.1.2.3) and 12 mL of aluminium chloride solution (3.2.1.2.5) into a polytetrafluoroethylene beaker, mix well, transfer it into a 100 mL plastic volumetric flask, dilute to the scale with water and shake well.
3.2.1.3 Apparatuses
Visible spectrophotometer.
3.2.1.4 Test procedure
3.2.1.4.1 Determination
Weigh about 0.2 g of specimen, to the nearest of 0.000 1 g. Place the sample into the polytetrafluoroethylene beaker, add 1 mL of sodium chloride solution (3.2.1.2.4), 3 mL of (1+1) hydrochloric acid (3.2.1.2.1) and 3 mL of hydrofluoric acid (3.2.1.2.3), heat it on a water bath at 80°C ~ 90°C for 15 min ~ 20 min, cool it, and add 12 mL of aluminium chloride solution (3.2.1.2.5), mix well, transfer to a 100 mL plastic flask, dilute to the scale and shake well, and leave to stand (the micro powder specimen may be dry filtered), pipette the upper 10 mL of clarified liquid into a 100 mL plastic volumetric flask, add water until the solution volume reaches 50 mL, add 2 drops ~ 3 drops of p-nitrophenol indicator (3.2.1.2.9), neutralize with aqueous ammonia (3.2.1.2.2) until the solution is yellow, immediately add 5mL of (1+4) hydrochloric acid (3.2.1.2.1), then add 5 mL of ammonium molybdate solution (3.2.1.2.6), and stand for 15 min. Add 10 mL of tartaric acid solution (3.2.1.2.7) and 5 mL of 1, 2, 4-acid solutions (3.2.1.2.8), dilute it to the scale with water and shake well, and stand for 30 min. Determine the absorbance at the wavelength of 700 nm using a 1 cm cuvette with water as the reference solution. Carry out the blank test using the same method. After subtracting the absorbance obtained from the blank test, obtain the mass of silicon dioxide from the working curve.
3.2.1.4.2 Construction of working curve
Pipette 10 mL of blank solution (3.2.1.2.11) into eight 100 mL volumetric flasks, and then add 0.00 mL, 0.50 mL, 1.00 mL, 2.00 mL, 4.00 mL, 6.00 mL, 8.00 mL and 10.00 mL of silicon dioxide standard solution (3.2.1.2.10) with the microburet respectively, then operate it according to the method in 3.2.1.4.1, determine the absorbance. Correspond to the corresponding mass of silicon dioxide and construct the working curve after subtracting the absorbance measured from the blank solution.
3.2.1.5 Test data processing
Calculate the mass fraction of silicon dioxide, ω(SiO2), using the Equation (1):
(1)
where,
m1——the mass of the specimen, g;
m2——the value of the mass of silicon dioxide obtained from the working curve in the specimen solution taken after subtracting that obtained from the blank test , g;
V1——the total volume of test solution, mL;
V2——the volume of test solution taken, mL;
Round the calculation result to two decimal places.
3.2.2 Potassium fluosilicate volumetric method
3.2.2.1 Principle
Heat and dissolve the silicon dioxide in hydrofluoric acid - potassium fluoride solution and hydrochloric acid solution to form potassium fluosilicate (K2SiF6) precipitation, hydrolyze it in boiling water and titrated with a 0.1 mol/L sodium hydroxide standard solution, and then calculate the silicon dioxide content from the volume of the sodium hydroxide standard solution consumed. The chemical equations are as follows:
SiO2+2KF+4HF→K2SiF6↓+2H2O
K2SiF6+4NaOH→2KF+4NaF+SiO2+2H2O
Note: The presence of elemental silicon will not affect the determination. If silicates and/or silicides are present, there may be a reaction leading to higher SiO2 results. Therefore, it must be checked as to whether this method is applicable in such cases.
Foreword i
1 Scope
2 Normative references
3 Analysis of surface impurities
3.1 Preparation of sample
3.2 Determination of silicon dioxide
3.3 Determination of free silicon
3.4 Determination of free carbon
3.5 Determination of loss on acid treatment (LAT)
3.6 Determination of silicon carbide
3.7 Determination of ferric oxide
3.8 Determination of aluminium oxide
3.9 Determination of calcium oxide and magnesium oxide
3.10 Determination of ferric oxide, aluminium oxide, calcium oxide and magnesium oxide by inductively coupled plasma-atomic emission spectrometry (ICP-AES)
4 Determination of silicon carbide in abrasives and crudes (indirect method)
4.1 Principle
4.2 Preparation of sample
4.3 Determination of total carbon
4.4 Determination of free carbon
4.5 Test data processing
4.6 Allowable error
5 Other methods of analysis
6 Test report
Annex A (Informative) Structural changes between this standard and ISO 9286:
