GOST 18317-94

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  ГОСТ 18317-94

GOST 18317−94 Powder metal. Methods for determination of water

GOST 18317−94

Group B59

INTERSTATE STANDARD

POWDER METAL

Methods for determination of water

Metallic powders. Methods for determination of water

OKS 77.120*
AXTU 1790

____________________
* In the index «National standards», 2008
OKS 77.160. — Note the manufacturer’s database.

Date of introduction 1997−01−01

Preface

1 DEVELOPED by the Institute for problems of materials science im. I. N. Frantsevich of NAS of Ukraine (TC 150 «Powder metallurgy»)

SUBMITTED to the State Committee of Ukraine for standardization, Metrology and certification

2 ADOPTED by the Interstate Council for standardization, Metrology and certification (Protocol N 6 of October 21, 1994)

The adoption voted:

3 Decree of the Russian Federation Committee on standardization, Metrology and certification dated June 19, 1996 N 401 interstate standard GOST 18317−94 introduced directly as state standard of the Russian Federation from January 1, 1997

4 REPLACE GOST 18317−73

1 SCOPE

This standard establishes titrimetric (with mass fraction of from 0.02 to 2.0%) and gravimetric (for the mass concentration of from 0.1 to 5.0%) methods for determination of water in the metal powders used in powder metallurgy.

Methods are used independently or simultaneously with the determination of the mass fraction of components in the analytical samples of the powders and then calculate their mass fraction in absolutely dry powder.

The standard does not apply to metal powders with organic substances on the surface which when heated to 110 °C to react in an inert gas atmosphere with water or decomposing with her education.

Standard suitable for certification purposes.

2 NORMATIVE REFERENCES

The present standard features references to the following standards:

GOST 450−77 Calcium chloride. Specifications

GOST 804−93 primary Magnesium ingots. Specifications

GOST 1770−74 laboratory Glassware measuring glass. Cylinders, beakers, flasks, test tubes. Specifications

GOST 2222−78 Methanol-technical poison. Specifications

GOST 4159−79 Iodine. Specifications

GOST 4204−77 sulfuric Acid. Specifications

GOST 5955−75 Benzene. Specifications

GOST 6709−72 distilled Water. Specifications

GOST 6995−77 Methanol-poison. Specifications

GOST 7995−80 Valves connecting the glass. Specifications

GOST 8984−75 Silica gel-indicator. Specifications

GOST 9932−75 lighting fixtures, glass, laboratory. Specifications

GOST 13647−78 Pyridine. Specifications

GOST 23148−78* Powder metal. Methods of sampling and sample preparation
________________
* On the territory of the Russian Federation GOST 23148−98. Here and further. — Note the manufacturer’s database.

GOST 23932−90 Glassware and laboratory equipment made of glass. General specifications

GOST 25336−82 Glassware and equipment laboratory glass. The types, basic parameters and dimensions

3 TITRIMETRIC METHOD DETERMINATION OF WATER

3.1 the essence of the method

The method is based on the interaction of water, obtained by distilling off the inert gas from prokalavaemy at a temperature of 105−110 °C powders, with the use of Fisher under the electrometric titration.

3.2 Apparatus, glassware and reagents

The installation for determining the mass fraction of water by electrometric titration reagent Fisher (figure 1).

Figure 1

The installation consists of the following elements:

glass laboratory rheometer 1 according to GOST 9932;

two bottles 2 for washing gases according to GOST 25336 filled with concentrated sulfuric acid according to GOST 4204;

the adsorbers 3 pre-calcined at a temperature of at least 200 °C activated carbon;

spiral traps 4 the silica-indicator with GOST 8984;

the three-way tap 5 according to GOST 7995 with two provisions:

A —  — inert gas stream is directed in a quartz tube 6;

In  — flow of inert gas is directed directly into the titration vessel, bypassing the quartz tube;

quartz tube 6 with a length of 400 mm and a diameter of not less than 30 mm, which is placed in Nickel boats 7;

tube furnace with nichrome heater 8, designed for temperatures up to 300 °C;

the three-way tap 9 with two provisions:

A — current of inert gas is directed into the titration vessel;

In a current of inert gas is directed into the atmosphere;

vessel for titration of 10 with a capacity of 300 to 400 cm, which is shown in figure 2;

electric circuit 11 to control the course of the titration;

microburette 12 type II according to GOST 1770 with a capacity of 25 cm, equipped with protection from atmospheric moisture gorkaltseva tube 13 according to GOST 25336;

the flask 14 with the use of Fisher with a capacity of 2000 cm;

U-shaped tube 15 according to GOST 25336 filled with painted and dried gel;

the flask 16 for washing the gases according to GOST 25336 with concentrated sulfuric acid according to GOST 4204;

rubber bulb 17.

The titration vessel (figure 2) consists of the following elements:

glass flask 1 volume of 300−400 cm;

crane fluid drain 8;

tubes 2 for inlet and outlet of inert gas into the flask;

section 3 — type And 29, with drainage pipe 4 or with a sealing cap;

tube 5, the hole where you insert protertuyu the nozzle with the capillary 6, drawn to the required length. Attached to the nozzle drain tube microburette type II according to GOST 1770;

platinum electrodes 7. The electrodes are soldered in a glass tube, ground to the hole in the titration vessel. The electrodes should be placed near the bottom of the vessel;

electric circuit 9 to indicate the progress of titration, consisting of a battery voltage of 1.5 V, the two resistors on the 2000 and 7000 Ohms, the switch and galvanometer sensitivity so that full deflection on the scale of the instrument occurred at a current not exceeding 100 mA.

Figure 2

The volume of the solution in the titration vessel should be at least 60 cm. The solution should completely cover the platinum electrodes.

The design of the titration vessel must ensure unimpeded discharge of fluid through the valve 8.

Volumetric flasks according to GOST 1770 with a capacity of 50 and 100 cm.

Pipettes according to GOST 1770 type I with a capacity of 5 and 10 cm.

Droppers, glass, laboratory for GOST 25336 type II.

Primary magnesium ingots according to GOST 804 brand Мг96.

Methanol is a poison according to GOST 6995 or GOST 2222, dried and distilled according to A. 1.

The use of Fisher’s, prepared by A. Z.

Sulfuric acid according to GOST 4204 concentrated.

Activated carbon.

Pyridine according to GOST 13647, h. e. a., dried and distilled according to A. 2.

Calcium chloride fused according to GOST 450, svezhepoymannyh.

Benzene according to GOST 5955, h.d. a.

Iodine GOST 4159, h

Isatin, h.d. a.

Silica gel-indicator according to GOST 8984.

Distilled water according to GOST 6709.

3.3 Sampling

3.3.1 Samples for testing are selected and prepared according to GOST 23148. Weight of sample for test shall be not less than 200 g. the weight of the portion for test, depending on the assumed mass fraction of water in the powder shall conform to the requirements of table 1.


Table 1

3.3.2 Powder was tested in the delivery condition, i.e. in air-dry condition. Allowed preliminary drying of the powder in the air.

3.3.3 the charge Weight of powder is determined with maximum error of 0.0002 g.

3.3.4 Determination should be carried out not less than two batches of powder.

3.4 Prepare for analysis

3.4.1 According to the scheme given in figure 1, collect the installation for Electromechanical titration of water, contained in the metal powders. As connecting links in the installation use either plastic or poluvalmovye, pre-drained hoses. For the lubrication of valves and sections should use silicone grease. In a quartz tube 6 placed pre-dried and weighed with an accuracy of at least 0.0002 g Nickel boats with a certain suspension of metal powder. In a vessel for titration 10 is placed a glass tube with soldered to it a platinum electrode and collecting the electric circuit as shown in figure 2. In the middle hole of the receptacle insert the nozzle with a capillary tube that is attached to microburette 12 with gorkaltseva tube 13. The vessel 14 is filled, the use of Fisher prepared by the method described in Appendix A.

3.4.2 Fill microburette with the use of Fisher with dehumidified air, which is provided by pear through the bottle 16 for washing the gas with concentrated sulfuric acid, and the tube filled with pre-painted and calcined silica.

3.4.3 Check the electrical diagram of the device. In the case of figure 2, the galvanometer is in circuit with the titration vessel. It can also be connected in shunted state. In the first case the galvanometer shows «0» at the end point when completion of the titration, and in the second case, the galvanometer during the titration is deflected to the side. At the bottom of the electrode by bringing a metal object to the conclusions of the electrodes. With closed electrodes, the arrow should deflect to full scale.

3.4.4 Establish the water equivalent of the reagent Fisher. To do this in a dry titration vessel through the hole 3 (figure 2) using a pipette make at least 60 cmof methanol until complete coating them with platinum electrodes. Installing the tap 5 (figure 1) to position b, the inert gas stream passed through the drying system directly into the titration vessel. To install the purge gas is passed in for 5−7 minutes, Include electrical circuit and titrated contained in the methanol water with the use of Fisher. At the beginning of the titration reagent Fisher served in the titration vessel at a speed of one drop per second. This galvanometer needle is deflected from the zero position slightly. When the needle of the galvanometer will strongly fluctuate, the use of Fisher’s adds at a speed of one drop per five seconds, and when approaching the equivalence point at a speed of one drop per ten seconds.

The titration is carried out until, until the galvanometer needle is not located in a certain position, which is maintained for 30−60 s. the Addition of 1−2 drops of reagent Fisher should not change the position of the needle of the galvanometer. This indicates the end of the titration. The volume of the reagent consumed in the titration of dehydrated methanol, isn’t taken into account.

Further check the completeness of the drying inert gas used for Stripping water from metal powders. With this aim pass during the hours gas through the titration vessel. If the galvanometer is deflected from the position established during the titration of methanol, then titrated again water inert gas with the use of Fisher to establish the permanent position of the galvanometer. Determine the amount of reagent Fisher spent on titrovaya water available in Gaza. Experience again, once again blowing an inert gas for one hour through the titration vessel. If the amount of water in the gas will be more than 0,002% per hour of purge, it should be taken into account when calculating the amount of water in the metal powders. Next to install the titer of the reagent Fischer titrated mixture through the hole 3 (see figure 2) contribute with a dropper one drop of distilled water with a mass of about 10 mg. Drip is removed and the hole closed with a ground joint cap. The drip is weighed before and after taking the signs with the maximum error of 0.0002 g. Allowed into the titration vessel a stream of nitrogen (crane 5 is in position b), and titrated water with the use of Fisher according to the method described above.

Water equivalent (titer) of Fischer reagent , g/cm, is calculated by the formula

, (1)

where is the mass of water introduced into the titration vessel by means of a dropper, g;

 — the volume of Fisher reagent consumed for titration of water, cm.

For the water equivalent of the reagent Fisher be the arithmetic mean of three parallel definitions, allowable differences between which should be no more than 0,00004 g/cm.

3.4.5 Preparing for the analysis of Nickel boats. Before application they must be maintained in a muffle for one hour at a temperature of 105−110 °C, then placed in a desiccator over a drying agent.

3.5 analysis

Through a quartz tube 6 of the installation (figure 1) flow inert gas (tap 5 is in position A, and the faucet 9 in the situation). The furnace was purged for 15−20 min. flow Rate of inert gas, such as in establishing the water equivalent of the reagent Fischer 3.4.4.

Simultaneously with the venting of the furnace is weighed in a Nickel boat, prepared in 3.4.5, a portion of the powder mass that meets the requirements of table 1.

Heat the oven to a temperature of 105−110 °C. the quartz tube at the outlet of the furnace take the plug out and in the stream of inert gas is inserted into the cold part of the tube Nickel boat with a charge of powder. A quartz tube closed with a stopper and 5−7 min move the boat through valves in the hot zone of the furnace where it is kept at a temperature of 105−110 °C until the termination of allocation of water from the powder. Systematically electrometric titration of allocated water with the use of Fisher according to the methods given in 3.4.4.

The analysis is considered complete when the inert gas used for Stripping water from a powder will not contain water. In this case, record the time spent on the analysis.

After the end of the titration pushing the boat into the cold zone of the quartz tube for cooling, switch the tap 9 to position In and remove the boat from the tube. Stop heating the furnace and turn off the gas flow.

Use the titration vessel for analysis of several samples of powder. The mass fraction of water absorbed by the methanol titration vessel, should not exceed 0.5%.

3.6 Processing of results

3.6.1 If the mass fraction of water in inert gas is not more than 0.002% per hour of the purge, the mass fraction of water in the powder ,%, is calculated by the formula

, (2)

where  — the volume of Fisher reagent consumed in the titration of the water evolved from the mass of sample of powder, cm;

 — water equivalent of the reagent Fisher, g/cm;

 — weight of powder,

3.6.2 If the mass fraction of water in inert gas is more than 0.002% per hour of the purge, the mass fraction of water in the powder ,%, is calculated by the formula

, (3)

where  — the volume of Fisher reagent consumed in the titration of the water contained in the inert gas cm.

Note — Time titration of water, contained in the sample powder, and the water contained in the inert gas must be the same.

3.6.3 the analysis result should be the arithmetic mean of at least two parallel definitions. Allowable absolute differences of the results of the parallel definitions should not exceed the values specified in table 2.


Table 2

Percentage

3.6.4 test Results (definitions) of the record containing:

— the name (brand) of powder and data on the conditions of storage and composition;

— sample mass and the sample taken for analysis, g;

— the volume of Fisher reagent consumed in the titration, cm;

— water equivalent of the reagent Fisher, g/cm;

— the arithmetic mean of the results of the analysis, %;

— the designation of this standard;

— the date of the test.

4 GRAVIMETRIC METHOD DETERMINATION OF WATER

4.1 the essence of the method

The method is based on drying in an oven at a temperature of 105−110 °C of sample of sample of powder, previously air-dried or taken in air-dry condition, to constant weight.

4.2 Equipment, utensils and reagents

The installation shown in 3.2 (figure 1).

Cups for weighing (boxy) with a sealing cap according to GOST 23932 and GOST 25336.

Desiccator, according to GOST 23932 and GOST 25336.

Calcium chloride, calcined at 700−800 °C, or melted to fill the desiccator.

4.3 Sampling

A sample of the powder for testing are selected and prepared in compliance with the requirements of 3.3. The mass of sample for testing, depending on the assumed mass fraction of water in the powder shall conform to the requirements of table 3.


Table 3

4.4 analysis

Prepare the installation (figure 1) for analysis. In the analysis through a quartz tube 6of the installation should always be purged with dry inert gas (tap 5 is in position A, and the faucet 9 in the situation). Mass fraction of water in a dry inert gas in the analysis should be not more than 0.005%. Check it periodically between tests according to 3.4.4.

Buxo, previously dried in the oven 8 (figure 1) in a stream of dry inert gas at a temperature of 105−110 °C, is weighed with the lid. A portion of the powder is placed in a balanced buxo, cover with lid and weighed.

To remove water from the powder weighted buxu with the open linkage and placed in an oven. The powder dried in a stream of dry inert gas at a temperature of 105−110 °C. the rate of inert gas passing through the heater 8, after a three-way tap 9 must be at least 25 mm/sec. in an hour buxu removed from the oven, quickly cover with a lid and cooled in a desiccator for 20−30 min. Buxu removed from the desiccator and weighed. Before weighing cover buxy need to open and close quickly.

The procedure of drying (within 30 min), cooling and weighing boxy powder is repeated until the differences between the last two masses of less than 0.0005 g.

All the weighting in the analysis carried out with a maximum error of 0.0002 g.

May be performed drying test portions of powder in a drying Cabinet with electric heating and thermostat without the use of inert gas environments or in vacuum, if there are indications in regulatory documents for a specific powder.

4.5 Processing of results

4.5.1 Mass fraction of water ,%, is calculated by the formula

, (4)

where is the mass of buxy with lid and weighed the powder before drying, g;

 — weight boxy with a lid and a powder after drying, g;

 — weight of powder,

4.5.2 For the result of the analysis be the arithmetic mean of at least two parallel definitions.

Permissible discrepancies in the results of parallel definitions should not exceed the values specified in table 4.


Table 4

Percentage

4.5.3 test Results (definitions) of the record containing:

— the name (brand) of powder and data on the conditions of storage and composition;

— sample mass and the sample taken for analysis, g;

— the arithmetic mean of the results of the analysis;

— the designation of this standard;

— the date of the test.

Annex a (recommended). PREPARATION OF REAGENTS

APPENDIX A
(recommended)

A. 1 Preparation of dehydrated methanol

Dehydrated methanol is produced by processing the magnesium methylate, which, reacting with water contained in the methanol, forming a hydroxide of magnesium.

In a round bottom flask with a capacity of 1 DM, equipped with a reflux condenser with gorkaltseva tube, was placed 5 g of magnesium chips, 0.5 g of sublimated iodine and pour 250−300 cmof methanol. While there is a vigorous evolution of hydrogen. If hydrogen is underdeveloped, and the mixture is slightly heated in a water bath for better dispersion of magnesium and complete its transition to methylate magnesium. Then across the top of the fridge poured into a bulb 500−600 cmof methanol and boil the mixture for 30 min. of Dehydrated methanol is distilled using reflux Christmas. In a receiver of glass with gorkaltseva tube, collecting the fraction boiling at a temperature of from 64 to 65.5 °C (at pressure PA 101330). In the distillation needs to be taken precautions against the ingress of air into the distilled methanol. The degree of dehydration (dehydration) of methanol should provide a mass fraction of water not more than 0.02%.

The maximum allowable concentration of methanol in air is 5 mg/m.

In one laboratory is not permitted to use methyl and ethyl alcohols at the same time.

Not allowed to work with methanol without ventilation.

Methanol should be stored in glass containers, the empty container should be rinsed out with water.

A. 2 Preparation of dehydrated pyridine

Dehydration of pyridine conduct azeotropic Stripping of water with benzene. To do this, in a round bottom flask with a capacity of 1 DMcontribute 500 cmof pyridine and 100 cmof benzene without thiophene (reaction with istinom: crystal isatin moistened with a few ml of concentrated sulfuric acid, then pour the benzene, in the presence of thiophene will appear in blue color). The contents of the flask thoroughly stirred for 5−10 min and subjected to distillation using a dephlegmator Christmas. Then, in a receiver of glass with gorkaltseva tube, collecting the fraction boiling at temperatures of from 114 to 116 °C (at pressure PA 101330). In the distillation needs to be taken precautions against the ingress of air into distilled pyridine.

The degree of dehydration (drying) of pyridine should provide the mass fraction of water not more than 0.02%.

The maximum permissible concentration of pyridine in air of 5 mg/m.

Not allowed to work with pyridine without ventilation.

Preparation of dehydrated methanol or pyridine is allowed to carry out any other method that provides the mass fraction of water not more than 0.02%.

A. H Preparation of reagent Fisher

The Fischer reagent is prepared according to the instructions attached to it. Water equivalent (titer) of Fischer reagent should be from 0.003 to 0.004 g/cm. It can be prepared in the following manner: in a dry flask with a capacity of 2000 cmstoppered measure 800 cmof anhydrous pyridine. Glass replace rubber stopper with two glass tubes, one of which reaches almost to the bottom of the bulb and is suitable for gas inlet, one for outlet of gas. The flask with contents is weighed and cooled in ice water. The introductory tube is connected with a glass siphon, filled with sulfur dioxide, used in refrigeration industry, and passed gas in the flask with continuous stirring until then, until the total mass of the flask with the contents of the will not increase on the 40, then remove the rubber stopper with the tubes and add 90 g of sublimated iodine. Close the vessel with a glass stopper, and shake to dissolve the iodine and leave the mixture for 24 h in a dark place, after which it is transferred into the vessel for reaction.

Flask storage Fischer reagent needs to be made of dark glass or closed cover of dark fabric to protect the reagent from light.

Water equivalent (titer) of Fischer reagent set 24 hours after its preparation, further definition is carried out at least once a day.