The standard applies to electrodes made of pure tungsten and tungsten with activating additives (thorium dioxide, lanthanum and yttrium oxides) intended for arc welding with a non-consumable electrode in an inert gas environment (argon, helium), as well as for flame processes of cutting, surfacing and spraying /

Designation:	GOST 23949-80
Russian name:	Electrodes tungsten welding nonconsumable. Specifications
Status:	valid
Text update date:	05.05.2017
Date added to database:	01.09.2013
Date of entry into force:	01.01.1981
Approved:	01/18/1980 USSR State Standard (USSR Gosstandart 217)
Published:	Standards Publishing House (1980) IPK Standards Publishing House (2004)
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GOST 23949-80

INTERSTATE STANDARD

TUNGSTEN ELECTRODES
WELDING NON-CONSUMABLE

TECHNICAL CONDITIONS

IPK STANDARDS PUBLISHING HOUSE

Moscow

INTERSTATE STANDARD

By the Decree of the State Committee of the USSR on Standards dated January 18, 1980 No. 217, the introduction date was set

from 01.01.81

The limitation of the validity period was lifted according to the protocol No. 4-93 of the Interstate Council for standardization, metrology and certification(IUS 4-94)

This standard applies to electrodes made of pure tungsten and tungsten with activating additives (thorium dioxide, lanthanum and yttrium oxides) intended for arc welding with a non-consumable electrode in an inert gas environment (argon, helium), as well as for plasma cutting, surfacing and spraying processes.

1. STAMPS

1.1. Depending on the chemical composition, the electrodes must be made of tungsten grades listed in Table. .

Table 1

	OKP code	Material
		Tungsten pure
		Tungsten with lanthanum oxide additive



		Tungsten doped with thorium dioxide

2. ASSORTMENT

Nominal diameter

Limit deviation

Not less than 3000 in skeins

1,0; 1,6; 2,0; 2,5

75 ± 1; 150 ± 1;

3,0; 4,0; 5,0; 6,0; 8,0; 10,0

200±2; 300±2

1,0; 1,6; 2,0; 2,5; 3,0; 4,0

75 ± 1; 150 ± 1;

5,0; 6,0; 8,0; 10,0

200±2; 300±2

2,0; 3,0; 4,0; 5,0; 6,0

75 ± 1; 150 ± 1;

200±2; 300±2

75 ± 1; 150 ± 1;

5,0; 6,0; 8,0; 10,0

200±2; 300±2

2,0; 3,0; 4,0; 5,0;

75 ± 1; 150 ± 1;

200±2; 300±2

Symbol exampleelectrode brand EVL, diameter 2.0 mm, length 150 mm:

Electrode tungsten EVL- Æ 2-150 - GOST 23949-80

3. TECHNICAL REQUIREMENTS

3.1. Tungsten electrodes must be manufactured in accordance with the requirements of this standard from grades of pure tungsten and tungsten with activating additives, the chemical composition of which corresponds to that specified in Table. .

Table 3

On the surface of electrodes processed by centerless grinding to the sizes indicated in Table. , transverse risks from grinding with a depth of more than half of the maximum deviation per diameter are not allowed.

3.3. The surface of electrodes made by drawing must be cleaned of oxides, technological lubricants and other contaminants by chemical treatment (etching).

Drawing marks with a depth of more than half of the diameter tolerance are not allowed on the surface of the electrodes.

3.4. The unevenness of the diameter along the length of the electrodes and the ovality should not exceed the maximum deviations per diameter.

3.5. The electrodes must be straight. The non-straightness of the electrodes should not be more than 0.25% length.

3.6. The ends of the electrodes must have a straight cut. Chips larger than the maximum deviation per diameter are not allowed on the end section of the electrodes.

4. ACCEPTANCE RULES

4.1. Electrodes are accepted in batches. A batch should consist of electrodes made from a charge of the same preparation and issued with one quality document.

The quality document must contain:

name of the manufacturer and trademark of the manufacturer;

product name and brand;

lot number;

result of chemical analysis;

date of manufacture;

the mass of the party and the number of seats in the party;

standard designation.

The quality document is put into box No. 1.

The batch weight should not exceed 1300 kg.

4.2. To determine the activating additives, three to five welded or sintered rods are selected from each batch.

The determination of impurities is carried out by the manufacturer on each batch of tungsten powder on a sample in accordance with GOST 20559-75.

4.3. Checking the conformity of the electrodes of paragraphs. , - carried out on each electrode.

4.4. If unsatisfactory results are obtained for the chemical composition, repeated tests are carried out on a double sample taken from the same batch. The retest results apply to the entire lot.

5. TEST METHODS

5.1. Sampling and preparation

5.1.1. To determine the activating additives, three to five rods are selected from the sample, pieces weighing 30–50 g are beaten off and rubbed in a mechanical mortar. The resulting powder is subjected to magnetic separation.

5.2. The content of impurities of aluminum, iron, silicon, molybdenum, calcium, nickel is determined according to GOST 14339.5-91.

5.3. The geometric dimensions, the uniformity of the diameter along the length and the ovality of the electrodes are checked with a micrometer according to GOST 6507-90 or a caliper according to GOST 166-89, as well as a ruler according to GOST 427-75.

5.4. The surface quality of the electrodes is checked visually. In case of disagreement in assessing the quality, optical means and a measuring instrument are used.

5.5. The straightness of the electrodes is checked using a probe according to TU 2-034-225-87 on a flat metal plate according to GOST 10905-86.

5.6. Checking the absence of internal delaminations and cracks is carried out using an eddy current flaw detector.

6. MARKING, PACKAGING, TRANSPORT AND STORAGE

6.1. Each electrode must be marked in accordance with the table. .

Electrodes with a diameter of 3.0 mm or more can be marked by chamfering 1 mm × 45 ° or notches.

The marking must be applied to one end of the electrode.

The marking can be applied to the end in the form of a strip or a dot on the surface near the end over a length of 5 - 10 mm.

Table 4

6.2. Electrodes of the same brand, of the same diameter should be placed in boxes made of cardboard with foam, corrugated or pressed thick paper.

6.3. Each box of electrodes is labeled with:

name of the manufacturer or its trademark;

Product name;

symbol of the product;

quantity, pcs.;

lot number;

release date;

type of marking;

technical control stamp.

The method establishes the determination of lanthanum oxide in lanthanum welded tungsten rods and electrodes.

1.1. Method Essence

The method is based on the separation of lanthanum from tungsten by dissolving a pre-oxidized and calcined test sample to tungsten anhydride ( WO3 ) in sodium carbonate solution.

In this case, lanthanum, which is in tungsten in the form of La 2O3 , precipitates, and the soluble form of lanthanum is additionally precipitated with ammonia in the form of La(OH) 3 .

The precipitate is filtered off, dissolved in hydrochloric acid, and all lanthanum is again precipitated with ammonia in the form of La(OH) 3, which is filtered off, washed and calcined to La 2 O 3 .

The error of the method with a mass fraction of lanthanum oxide from 1% to 3% is 0.1% with a mass fraction of lanthanum oxide less than 1% -0.05%.

1.2. Reagents

Sodium carbonate crystalline according to GOST 84-76, 30% solution.

Water ammonia according to GOST 3760-79, 25% solution.

Hydrochloric acid according to GOST 3118-77, density 1.12 g / cm 3.

1.3. Sample preparation

Tungsten anhydride is pre-calcined in a muffle furnace at 700 - 750 ° C for 1.5 - 2 hours.

Tungsten powder, a sample from a rod or electrode is oxidized to anhydride by calcination in a muffle furnace at a temperature of 700 - 750 ° C. In this case, the sample is poured into a porcelain crucible at 1/3 of its height and placed in a muffle at 400 - 500 ° C for 1.5 - 2 hours, and then the temperature is raised to 700 - 750 ° C and the crucible is kept until the powder is completely oxidized (~ 3 hours).

For uniform oxidation of tungsten, the crucible is removed from the furnace two or three times and the sample is stirred.

1.4. Conducting an analysis

2 - 3 g of tungsten anhydride is placed in a glass of 150 - 200 cm 3, 50 - 70 cm 3 of sodium carbonate solution is poured and dissolved by heating.

After the dissolution of tungstic anhydride, the solution is diluted with distilled water to a volume of ~100 cm 3 , 20 - 30 cm 3 of ammonia solution are added, the beaker is placed in an electric bath and the precipitate is allowed to coagulate. The precipitate is filtered through a filter - "white ribbon" with an adsorbent, washed with a warm 5% ammonia solution; the filter with sediment is placed in a beaker in which precipitation was carried out, 15–20 cm 3 of hydrochloric acid are added, and the contents of the beaker are heated until the precipitate is completely dissolved and the filter is mocerated.

The filtrate is neutralized with a solution of ammonia according to litmus, after which another 15 - 20 cm 3 of ammonia are added.

The precipitate of La(OH) 3 is allowed to coagulate, then it is filtered through a filter - "white tape" with an adsorbent. The precipitate is washed with hot water, to which a few drops of ammonia solution are added until a negative reaction for Cl (sample with AgNO 3 and HNO 3 ).

The washed precipitate with a filter is placed in a pre-calcined and weighed porcelain crucible, ashed and calcined in a muffle furnace at a temperature of 700 - 750 ° C to constant weight.

1.5. Results processing

The mass fraction of lanthanum oxide in percent is calculated by the formula

Where T - sediment mass, g;

m 1 - weighed weight of tungsten anhydride (WO 3), d;

0.7931 - conversion factor from tungsten anhydride to tungsten.

Note. The calcined precipitate of lanthanum oxide contains iron oxide, the amount of which is very small compared to the amount of lanthanum oxide, so the mass of iron oxide can be neglected.

If the determination of pure lanthanum oxide is required, then the calcined precipitate is dissolved in hydrochloric acid, iron is colorimetric, and the mass of lanthanum oxide is determined by difference.

2. METHOD FOR DETERMINING THE CONTENT OF YTTRIUM OXIDE

The method establishes the determination of yttrium oxide in yttrated welded tungsten rods and electrodes.

2.1. Method Essence

The method is based on the separation of yttrium from tungsten by dissolving the test sample in hydrofluoric acid with the addition of nitric acid.

With a mass fraction of yttrium oxide from 1 to 3%, the error of the method is 4 - 5%.

2.2. Equipment, reagents and solutions

Drying cabinet providing heating to a temperature of (150 ± 50) °С.

Muffle furnace with a thermocouple, providing heating to a temperature of (1100 ± 50)° C.

Platinum cups and crucibles - GOST 6563-75.

Laboratory porcelain glassware - GOST 9147-80.

Hydrofluoric acid (hydrofluoric acid) - according to GOST 10484-78.

Nitric acid - GOST 4461-77.

Water ammonia - GOST 3760-79, diluted 1:1.

Funnels are polyethylene.

Distilled water - GOST 6709-72.

Rectified ethyl alcohol - GOST 5962-67*.

* On the territory of the Russian Federation, GOST R 51652-2000 applies.

Laboratory filter paper - GOST 12026-76.

2.3. Sample preparation

Samples of yttrated tungsten are cleaned of possible contamination by washing them several times with alcohol and then drying in an oven at a temperature of 50–70 °C for 10 minutes. Prepared samples are stored in glass bottles or test tubes with ground stoppers.

2.4. Conducting an analysis

A sample weighing 1 g is placed in a platinum cup with a capacity of 100 cm 3 , 25–30 cm 3 of hydrofluoric acid are added, and nitric acid is carefully added dropwise until the metal dissolves.

After the complete dissolution of tungsten and the cessation of the release of nitrogen oxides, 30 cm 3 of water, heated to a temperature of 80 - 90 ° C, is added to the cup.

The precipitated solution is allowed to stand for 1 h, after which it is filtered through a polyethylene funnel.

After the sediment has been transferred to the filter, the bottom of the cup is wiped with a piece of a wet filter, and all the contents on it are poured onto the filter with hot water. Then the precipitate is washed five or six times with hot ammonia solution (60 - 70 °C) and two or three more times with hot water.

The washed precipitate is transferred to a pre-weighed porcelain crucible, dried in an oven at a temperature of 100–150 °C, and then calcined in a muffle furnace at a temperature of 650–700 °C to constant weight and weighed in the form of yttrium oxide.

2.5. Results processing

The mass fraction of yttrium oxide in percent is calculated by the formula

Where m- mass of the calcined residue, g;

T 1 - weight of the sample sample, g.

3. METHOD FOR DETERMINING THE CONTENT OF THORIUM DIOXIDE

The method establishes definitions of thorium dioxide in thoriated welded tungsten rods and electrodes.

3.1. Method Essence

The method is based on the formation of ThF precipitate 4 4H 2 O when the sample is dissolved in a mixture of hydrofluoric and nitric acids.

The error of the method at a mass fraction of thorium dioxide from 1.5% to 2% is 0.1%.

3.2. Reagents

Hydrofluoric acid (hydrofluoric) - GOST 10484-78.

Nitric acid according to GOST 4461-77.

Water ammonia according to GOST 3760-79, diluted 1:1.

Distilled water according to GOST 6709-72.

3.3. Sample preparation

The samples are boiled for several minutes in an alkali solution until the oxides are completely removed from the surface, washed in distilled water, and dried in an oven.

3.4. Conducting an analysis

A sample weighing 1 - 2 g is placed in a platinum cup with a capacity of 100 cm 3, 25 - 30 cm 3 of hydrofluoric acid are added and nitric acid is carefully added dropwise.

After the complete dissolution of tungsten and the cessation of the release of nitrogen oxides, 30 cm 3 of hot water are added to the cup. The solution with the thorium oxide precipitate is allowed to settle for 1 hour, after which it is filtered through a rubber, vinyl plastic or platinum funnel.

Before filtering, a small amount of adsorbent is placed on the filter.

After the sediment is transferred to the filter, the bottom of the cup is wiped with a piece of a wet filter and the cup is washed with hot water. When the precipitate of thorium oxide is completely transferred to the filter, it is washed several times with hot water, and then five or six times with hot ammonia solution and two or three more times with hot water.

The wet filter is transferred to a porcelain or platinum crucible pre-weighed to a constant mass, ashed, calcined at a temperature of 750-800 °C and weighed.

Simultaneously conduct a control experiment with all reagents.

3.5. Results processing

The mass fraction of thorium dioxide in percent is calculated by the formula

Where m- sediment mass ThO 2 , g;

m 1 - sediment mass in the control experiment, g;

m 2 - weight of sample sample, g.

STATE STANDARD OF THE UNION OF THE SSR

TUNGSTEN ELECTRODES
WELDING NON-CONSUMABLE

TECHNICAL CONDITIONS

GOST 23949-80

USSR STATE COMMITTEE ON STANDARDS

Moscow

STATE STANDARD OF THE UNION OF THE SSR

By the Decree of the USSR State Committee for Standards dated January 18, 1980 No. 217, the introduction period was established

from 01.01.81

By Decree of the State Standard of the USSR dated July 22, 1986 No. 2200, the validity period was extended

until 01.01.90

1. STAMPS

1.1 . Depending on the chemical composition, the electrodes must be made of tungsten grades listed in Table. .

Table 1

brand	OKP code	Material
EHF	1853741000	Tungsten pure
EVL	1853742000	Tungsten with lanthanum oxide additive
EVI-1	1853743000
EVI-2	1853744000	Tungsten with yttrium oxide additive
EVI-3	1853745000	Tungsten with yttrium oxide additive
EVT-15	1853746000	Tungsten doped with thorium dioxide

2. ASSORTMENT

2.1 . The dimensions of the electrodes and the maximum deviations must correspond to those indicated in Table. .

Table 2

brand	Nominal diameter	Limit deviation	Length
EHF		±0.2	Not less than 3000 in skeins
	1,0; 1,6; 2,0; 2,5	±0.1	75 ± 1; 150 ± 1;
	3,0; 4,0; 5,0; 6,0; 8,0; 10,0	±0.2	200±2; 300±2
EVL	1,0; 1,6; 2,0; 2,5; 3,0; 4,0;	±0.1	75 ± 1; 150 ± 1;
EVL	5,0; 6,0; 8,0; 10,0	±0.2	200±2; 300±2
EVI-1	2,0; 3,0; 4,0; 5,0; 6,0	±0.1	75 ± 1; 150±1
EVI-1	8,0; 10,0	±0.2	200±2; 300±2
EVI-2	2,0; 3,0; 4,0; 5,0; 6,0; 8,0; 10,0	±0.15
EVI-3	2,0; 3,0; 4,0; 5,0; 6,0; 8,0; 10,0	±0.15
EVT-15	2,0; 3,0; 4,0; 5,0 6,0; 8,0; 10,0	±0.15	75 ± 1; 150 ± 1; 200±2; 300±2

Symbol exampleelectrode brand EVL, diameter 2.0 mm, length 150 mm:

Electrode tungsten EVL- Æ 2-150 - GOST 23949-80

3. TECHNICAL REQUIREMENTS

3.1 . Tungsten electrodes must be manufactured in accordance with the requirements of this standard from grades of pure tungsten and tungsten with activating additives, the chemical composition of which corresponds to that specified in Table. .

3.2 . On the surface of the electrodes there should be no shells, delaminations, cracks, oxides, residues of technological lubricants, foreign inclusions and contaminants.

Table 3

Electrode brand	Mass fraction, %
	Tungsten, not less	Additives				Impurities, no more
	Tungsten, not less	Lanthanum oxide	yttrium oxide	Thorium dioxide	Tantalum	Aluminium, iron, nickel, silicon, calcium, molybdenum (sum)
EHF	99,92					0,08
EVL	99,95	1,1 - 1,4				0,05
EVI-1	99,89		1,5 - 2,3			0,11
EVI-2	99,95		2,0 - 3,0		0,01	0,05
EVI-3	99,95		2,5 - 3,5		0,01	0,05
EVT-15	99,91			1,5 - 2,0		0,09

Notes :

1 . The mass fractions of lanthanum oxide, yttrium oxide, thorium dioxide and tantalum indicated in the table are included in the mass fraction of tungsten.

2 . For the EVL brand, nickel is not included in the amount of impurities.

3.3 . The surface of electrodes made by drawing must be cleaned of oxides, technological lubricants and other contaminants by chemical treatment (etching).

Drawing marks with a depth of more than half of the diameter tolerance are not allowed on the surface of the electrodes.

3.4 . The unevenness of the diameter along the length of the electrodes and the ovality should not exceed the maximum deviations per diameter.

3.5 . The electrodes must be straight. The non-straightness of the electrodes should not exceed 0.25% of the length.

3.6 . The ends of the electrodes must have a straight cut. Chips larger than the maximum deviation per diameter are not allowed on the end section of the electrodes.

3.7 . Internal delaminations and cracks are not allowed.

4. ACCEPTANCE RULES

4.1 . Electrodes are accepted in batches. A batch should consist of electrodes made from a charge of the same preparation and issued with one quality document.

The quality document must contain:

name of the manufacturer and trademark of the manufacturer;

product name and brand;

lot number;

result of chemical analysis;

date of manufacture;

the mass of the party and the number of seats in the party;

standard designation.

The quality document is put into box No. 1.

The batch weight should not exceed 1300 kg.

4.2 . To determine the activating additives, 3 - 5 are selected welded or sintered rods from each batch.

The determination of impurities is carried out by the manufacturer on each batch of tungsten powder on a sample in accordance with GOST 20559-75.

4.3 . Checking the conformity of the electrodes of paragraphs. , - carried out on each electrode.

4.4 . If unsatisfactory results are obtained for the chemical composition, repeated tests are carried out on a double sample taken from the same batch. The retest results apply to the entire lot.

5. TEST METHODS

5.1 . Sampling and preparation

5.1.1 . To determine the activating additives, 3–5 rods are selected from the sample, pieces weighing 30–50 g are beaten off and rubbed in a mechanical mortar.

The resulting powder is subjected to magnetic separation.

5.2 . The content of impurities of aluminum, iron, silicon, molybdenum, calcium, nickel is determined by GOST 14339.5-82.

5.3 . The geometric dimensions, the uniformity of the diameter along the length and the ovality of the electrodes are checked with a micrometer according to GOST 6507 -78, or caliper according to GOST 166 -80, as well as a ruler along GOST 427-75.

5.4 . The surface quality of the electrodes is checked visually. In case of disagreement in assessing the quality, optical means and a measuring instrument are used.

5.5 . The straightness of the electrodes is checked using a probe according to GOST 882-75 on a flat metal plate according to GOST 10905-86.

5.6 . Checking the absence of internal delaminations and cracks is carried out using an eddy current flaw detector.

6. MARKING, PACKAGING, TRANSPORT AND STORAGE

6.1 . Each electrode must be marked in accordance with the table. .

Electrodes with a diameter of 3.0 mm or more can be marked with a chamfer of 1 mm´ 45° or notch.

The marking must be applied to one end of the electrode.

The marking can be applied to the end in the form of a strip or a dot on the surface near the end over a length of 5 - 10 mm.

Table 4

brand	Color
EHF	Not marked
EVL	Black
EVI-1	Blue
EVI-2	Violet
EVI-3	Green
EVT-15	Red

6.2 . Electrodes of the same brand, of the same diameter should be placed in boxes made of cardboard with foam, corrugated or pressed thick paper.

6.3 . Each box of electrodes is labeled with:

name of the manufacturer or its trademark;

Product name;

symbol of the product;

quantity, pcs.;

lot number;

release date;

type of marking;

technical control stamp.

6.4 . Boxes with electrodes are packed in wooden boxes according to GOST 2991-85 type 1 or 2, lined inside with packing waterproof paper according to GOST 8828 -75. The remaining free volume of the box is tightly filled with wrapping paper or cotton wool. GOST 5679-85.

Gross weight of the box - no more than 40 kg.

6.5 . The box is labeled according to GOST 14192-77 with additional information:

names, brands, sizes of electrodes;

lot numbers;

packaging dates;

net weight.

6.6 . Packed electrodes are transported by all modes of transport in covered vehicles.

During transportation, the stacking of boxes should prevent their movement, mechanical damage to the packaging and electrodes, and moisture ingress.

Transportation conditions in terms of the impact of climatic factors - according to GOST 15150-69 group GOST 15150-69.

6.7 . The electrodes should be stored in the packaging provided for in p. , according to the group of storage conditions L GOST 15150-69.

APPLICATION

Mandatory

1. METHOD FOR DETERMINING THE CONTENT OF LANTHANUM OXIDE

The method establishes the determination of lanthanum oxide in lanthanum welded tungsten rods and electrodes.

1.1 . Method Essence

The method is based on the separation of lanthanum from tungsten by dissolving a pre-oxidized and calcined test sample to tungsten anhydride ( WO3 ) in sodium carbonate solution.

In this case, lanthanum, which is in tungsten in the form La2O3 , precipitates, and the soluble form of lanthanum is additionally precipitated with ammonia in the form La (OH) 3 .

The precipitate is filtered off, dissolved in hydrochloric acid, and all lanthanum is again precipitated with ammonia in the form La(OH ) 3 , which is filtered off, washed and calcined to La2O3.

The error of the method with a mass fraction of lanthanum oxide from 1% to 3% is 0.1%, with a mass fraction of lanthanum oxide less than 1% - 0.05%.

1.2 . Reagents

Sodium carbonate crystalline according to GOST 84-76, 30% solution.

Water ammonia according to GOST 3760-79, 25% solution.

Hydrochloric acid according to GOST 3118-77, density 1.12 g/cm3.

Distilled water according to GOST 6709-72.

1.3 . Sample preparation

Tungsten anhydride is pre-calcined in a muffle furnace at 700 - 750 ° C for 1.5 - 2 hours.

For uniform oxidation of tungsten, the crucible is removed from the furnace 2–3 times and the sample is stirred.

1.4 . Conducting an analysis

2 - 3 g of tungsten anhydride is placed in a glass of 150 - 200 ml, 50 - 70 ml of sodium carbonate solution is added and dissolved by heating.

After the dissolution of tungstic anhydride, the solution is diluted with distilled water to a volume of ~ 100 ml, 20–30 ml of ammonia solution is added, the beaker is placed in an electric bath and the precipitate is allowed to coagulate. The precipitate is filtered through a filter - "white ribbon" with an adsorbent, washed with a warm 5% ammonia solution; the filter with sediment is placed in a beaker in which precipitation was carried out, 15–20 ml of hydrochloric acid are added, and the contents of the beaker are heated until the precipitate is completely dissolved and the filter is mocerated.

The filtrate is neutralized with a solution of ammonia according to litmus, after which another 15 - 20 ml of ammonia is added.

Precipitate La(OH ) 3 is allowed to coagulate, then it is filtered through a “white tape” filter with an adsorbent. The precipitate is washed with hot water, to which a few drops of ammonia solution are added until a negative reaction to Cl (sample with AgNO 3 and H N O 3).

The washed precipitate with a filter is placed in a pre-calcined and weighed porcelain crucible, ashed and calcined in a muffle furnace at a temperature of 700 - 750 ° C to constant weight.

1.5 . Results processing

The mass fraction of lanthanum oxide in percent is calculated by the formula

Where T- sediment mass, g;

t 1- weight of sample of tungsten anhydride ( WO 3 ), g;

0 ,7931 - conversion factor from tungsten anhydride to tungsten.

Note . The calcined precipitate of lanthanum oxide contains iron oxide, the amount of which is very small compared to the amount of lanthanum oxide, so the mass of iron oxide can be neglected.

2. METHOD FOR DETERMINING THE CONTENT OF YTTRIUM OXIDE

The method establishes the definition of yttrium oxide in iterated welded tungsten rods and electrodes.

2.1 . Method Essence

The method is based on the separation of yttrium from tungsten by dissolving the test sample in hydrofluoric acid with the addition of nitric acid.

With a mass fraction of yttrium oxide from 1 to 3%, the error of the method is 4 - 5%.

2.2 . Equipment, reagents and solutions

Drying cabinet providing heating to a temperature of (150 ± 50) °С. A muffle furnace with a thermocouple providing heating to a temperature of (1100 ± 50) °C.

Platinum cups and crucibles - GOST 6563-75.

Samples of yttrated tungsten are cleaned from possible contamination by washing them several times with alcohol and then drying in an oven at a temperature of 50 - 70° C for 10 min.

Prepared samples are stored in glass bottles or test tubes with ground stoppers.

2.4 . Conducting an analysis

A sample weighing 1 g is placed in a platinum cup with a capacity of 100 ml, 25–30 ml of hydrofluoric acid are added, and nitric acid is carefully added dropwise until the metal dissolves.

After the complete dissolution of tungsten and the cessation of the release of nitrogen oxides, 30 ml of water, heated to a temperature of 80 - 90 ° C, is added to the cup.

The precipitated solution is allowed to stand for 1 h, after which it is filtered through a polyethylene funnel.

After the sediment has been transferred to the filter, the bottom of the cup is wiped with a piece of a wet filter, and all the contents on it are poured onto the filter with hot water. Then the precipitate is washed 5-6 times with hot ammonia solution (60-70 °C) and 2-3 more times with hot water.

2.5 . Results processing

The mass fraction of yttrium oxide in percent is calculated by the formula

where m - mass of the calcined residue, g;

m 1 - weight of sample sample, g.

3. METHOD FOR DETERMINING THE CONTENT OF THORIUM DIOXIDE

The method establishes definitions of thorium dioxide in thoriated welded tungsten rods and electrodes.

3.1 . Method Essence

The method is based on the formation of a precipitate T hF 4 × 4H2 About when dissolving the sample in a mixture of hydrofluoric and nitric acids.

The error of the method at a mass fraction of thorium dioxide from 1.5% to 2% is 0.1%.

3.2 . Reagents

Hydrofluoric acid (hydrofluoric) - GOST 10484-78.

Nitric acid according to GOST 4461-77.

Water ammonia according to GOST 3760-79, diluted 1: 1.

Distilled water according to GOST 6709-72.

3.3 . Sample preparation

The samples are boiled for several minutes in an alkali solution until the oxides are completely removed from the surface, washed in distilled water and dried in an oven.

3.4 . Conducting an analysis

A sample weighing 1 - 2 g is placed in a platinum cup with a capacity of 100 ml, 25 - 30 ml of hydrofluoric acid are added and nitric acid is carefully added dropwise.

After the complete dissolution of tungsten and the cessation of the release of nitrogen oxides, 30 ml of hot water are added to the cup. A solution with a precipitate of thorium oxideallow to settle for 1 hour, after which it is filtered through a rubber, vinyl plastic or platinum funnel.

Before filtering, a small amount of adsorbent is placed on the filter.

After the sediment is transferred to the filter, the bottom of the cup is wiped with a piece of a wet filter and the cup is washed with hot water. When the precipitate of thorium oxide is completely transferred to the filter, it is washed several times with hot water, and then 5-6 times with hot ammonia solution and 2-3 more times with hot water.

The wet filter is transferred to a porcelain or platinum crucible pre-weighed to a constant mass, ashed, calcined at a temperature of 750-800 °C and weighed.

Simultaneously conduct a control experiment with all reagents.

3.5 . Results processing

The mass fraction of thorium dioxide in percent is calculated by the formula

Where T- sediment mass T hO 2 , g;

t 1- mass of sediment in the control experiment, g;

t 2- weight of sample sample, g.

INTERSTATE STANDARD

TECHNICAL CONDITIONS

Official edition

IPK PUBLISHING STANDARDS Moscow

INTERSTATE STANDARD

TUNGSTEN WELDING ELECTRODES

Specifications

Welding nonconsumable tungsten electrodes. Specifications

GOST

23949-80

MKS 25.160.20 OKP 18 5374 0000

By the Decree of the State Committee of the USSR on Standards dated January 18, 1980 No. 217, the introduction date was set

The validity period was removed according to protocol No. 4-93 of the Interstate Council for Standardization, Metrology and Certification (IUS 4-94)

1.1. Depending on the chemical composition, the electrodes must be made of tungsten grades listed in Table. 1.

Table 1

2. ASSORTMENT

2.1. The dimensions of the electrodes and the maximum deviations must correspond to those indicated in Table. 2.

Official edition

Reprint prohibited

★

Reissue. September 2004

Table 2mm

Nominal diameter	limiting deviation
		Not less than 3000 in skeins
1,0; 1,6; 2,0; 2,5
3,0; 4,0; 5,0; 6,0; 8,0; 10,0
1,0; 1,6; 2,0; 2,5; 3,0; 4,0
5,0; 6,0; 8,0; 10,0
5,0; 6,0; 8,0; 10,0
2,0; 3,0; 4,0; 5,0; 6,0



5,0; 6,0; 8,0; 10,0
2,0; 3,0; 4,0; 5,0; 6,0; 8,0; 10,0		75±1; 150±1; 200±2; 300±2

An example of a symbol for an EVL electrode, 2.0 mm in diameter, 150 mm long:

Tungsten electrode EVL-0 2-150 - GOST 23949-80

3. TECHNICAL REQUIREMENTS

Table 3

Notes:

1. The mass fractions of lanthanum oxide, yttrium oxide, thorium dioxide and tantalum indicated in the table are included in the mass fraction of tungsten.

2. Nickel is not included in the amount of impurities for the EVL brand.

3.2. On the surface of the electrodes there should be no shells, delaminations, cracks, oxides, residues of technological lubricants, foreign inclusions and contaminants.

On the surface of electrodes processed by centerless grinding to the sizes indicated in Table. 2, transverse risks from grinding with a depth of more than half of the maximum deviation per diameter are not allowed.

3.3. The surface of electrodes made by drawing must be cleaned of oxides, technological lubricants and other contaminants by chemical treatment (etching).

Drawing marks with a depth of more than half of the diameter tolerance are not allowed on the surface of the electrodes.

3.4. The unevenness of the diameter along the length of the electrodes and the ovality should not exceed the maximum deviations per diameter.

3.5. The electrodes must be straight. The non-straightness of the electrodes should not exceed 0.25% of the length.

3.6. The ends of the electrodes must have a straight cut. Chips larger than the maximum deviation per diameter are not allowed on the end section of the electrodes.

3.7. Internal delaminations and cracks are not allowed.

4. ACCEPTANCE RULES

4.1. Electrodes are accepted in batches. A batch should consist of electrodes made from a charge of the same preparation and issued with one quality document.

The quality document must contain:

name of the manufacturer and trademark of the manufacturer;

product name and brand;

lot number;

result of chemical analysis;

date of manufacture;

the mass of the party and the number of seats in the party;

standard designation.

The quality document is put into box No. 1.

The batch weight should not exceed 1300 kg.

4.2. To determine the activating additives, three to five welded or sintered rods are selected from each batch.

The determination of impurities is carried out by the manufacturer on each batch of tungsten powder on a sample in accordance with GOST 20559-75.

4.3. Checking the conformity of the electrodes of paragraphs. 2.1, 3.2-3.7 are carried out on each electrode.

4.4. If unsatisfactory results are obtained for the chemical composition, repeated tests are carried out on a double sample taken from the same batch. The retest results apply to the entire lot.

5. TEST METHODS

5.1. Sampling and preparation

5.1.1. To determine the activating additives, three to five rods are selected from the sample, pieces weighing 30-50 g are beaten off and rubbed in a mechanical mortar.

The resulting powder is subjected to magnetic separation.

5.4. The surface quality of the electrodes is checked visually. In case of disagreement in assessing the quality, optical means and a measuring instrument are used.

5.5. The straightness of the electrodes is checked using a probe according to TU 2-034-225-87 on a flat metal plate according to GOST 10905-86.

5.6. Checking the absence of internal delaminations and cracks is carried out using an eddy current flaw detector.

6. MARKING, PACKAGING, TRANSPORT AND STORAGE

6.1. Each electrode must be marked in accordance with the table. 4.

Electrodes with a diameter of 3.0 mm or more can be marked by chamfering 1 mm x 45 ° or notches.

The marking must be applied to one end of the electrode.

The marking can be applied to the end in the form of a strip or a dot on the surface near the end over a length of 5-10 mm.

6.2. Electrodes of the same brand, of the same diameter should be placed in boxes made of cardboard with foam, corrugated or pressed thick paper.

6.3. Each box with electrodes is labeled with a label containing: the name of the manufacturer or its trademark; Product name;

symbol of the product;

quantity, pcs.;

lot number;

release date;

type of marking;

technical control stamp.

6.4. Boxes with electrodes are packed in plank boxes according to GOST 2991-85 type 1 or 2, lined inside with waterproof packaging paper according to GOST 8828-89. The remaining free volume of the box is tightly filled with packing paper or cotton wool in accordance with GOST 5679-91.

Gross weight of the box - no more than 40 kg.

6.5. The box is marked according to GOST 14192-96 with additional data: names, brands, sizes of electrodes;

lot numbers; packaging dates; net weight.

6.6. Packed electrodes are transported by all modes of transport in covered vehicles.

During transportation, the stacking of boxes should prevent their movement, mechanical damage to the packaging and electrodes, and moisture ingress.

Transportation conditions in terms of the impact of climatic factors - according to GOST 15150-69 group GOST 15150-69.

6.7. The electrodes should be stored in the packaging provided for and. 6.4, according to the group of storage conditions L GOST 15150-69.

APPLICATION

Mandatory

1. METHOD FOR DETERMINING THE CONTENT OF LANTHANUM OXIDE

The method establishes the determination of lanthanum oxide in lanthanum welded tungsten rods and electrodes.

1.1. Method Essence

The method is based on the separation of lanthanum from tungsten by dissolving a previously oxidized and calcined test sample to tungsten anhydride (WO3) in a solution of sodium carbonate.

In this case, lanthanum, which is in tungsten in the form of LasOz, precipitates, and the soluble form of lanthanum is additionally precipitated with ammonia in the form of La(OH) 3 .

The precipitate is filtered off, dissolved in hydrochloric acid, and all lanthanum is again precipitated with ammonia in the form of La(OH) 3 , which is filtered off, washed and calcined to ba 2 03.

The error of the method with a mass fraction of lanthanum oxide from 1% to 3% is 0.1% with a mass fraction of lanthanum oxide less than 1% -0.05%.

1.2. Reagents

Sodium carbonate crystalline according to GOST 84-76, 30% solution.

Water ammonia according to GOST 3760-79, 25% solution.

Hydrochloric acid according to GOST 3118-77, density 1.12 g/cm3.

1.3. Sample preparation

Tungsten anhydride is preliminarily calcined in a muffle furnace at 700-750°C for 1.5-2 hours.

Tungsten powder, a sample from a rod or electrode is oxidized to anhydride by calcination in a muffle furnace at a temperature of 700-750 °C. In this case, the sample is poured into a porcelain crucible at 1/3 of its height and placed in a muffle at 400-500 °C for 1.5-2 hours, and then the temperature is increased to 700-750 °C and the crucible is kept until the powder is completely oxidized (~ 3 hours).

For uniform oxidation of tungsten, the crucible is removed from the furnace two or three times and the sample is stirred.

1.4. Conducting an analysis

2-3 g of tungsten anhydride is placed in a glass of 150-200 cm 3 , 50-70 cm 3 of sodium carbonate solution is added and dissolved by heating.

After the dissolution of tungstic anhydride, the solution is diluted with distilled water to a volume of -100 cm 3 , 20-30 cm 3 of ammonia solution are added, the beaker is placed in an electric bath and the precipitate is allowed to coagulate. The precipitate is filtered through a filter - "white ribbon" with an adsorbent, washed with a warm 5% ammonia solution; the filter with sediment is placed in a beaker in which precipitation was carried out, 15–20 cm 3 of hydrochloric acid are added, and the contents of the beaker are heated until the precipitate is completely dissolved and the filter is mocerated.

The filtrate is neutralized with a solution of ammonia according to litmus, after which another 15-20 cm 3 of ammonia are added.

The washed precipitate with a filter is placed in a pre-calcined and weighed porcelain crucible, ashed and calcined in a muffle furnace at a temperature of 700-750 °C to constant weight.

1.5. Results processing

The mass fraction of lanthanum oxide in percent is calculated by the formula

100,

where m is the mass of sediment, g;

t\ - mass of a sample of tungsten anhydride (WO3), g;

0.7931 - conversion factor from tungsten anhydride to tungsten.

Note. The calcined precipitate of lanthanum oxide contains iron oxide, the amount of which is very small compared to the amount of lanthanum oxide, so the mass of iron oxide can be neglected.

2. METHOD FOR DETERMINING THE CONTENT OF YTTRIUM OXIDE

The method establishes the determination of yttrium oxide in yttrated welded tungsten rods and electrodes.

2.1. Method Essence

The method is based on the separation of yttrium from tungsten by dissolving the test sample in hydrofluoric acid with the addition of nitric acid.

With a mass fraction of yttrium oxide from 1 to 3%, the error of the method is 4-5%.

2.2. Equipment, reagents and solutions

Drying cabinet providing heating to a temperature of (150±50) °С.

A muffle furnace with a thermocouple providing heating to a temperature of (1100±50) °C.

Platinum cups and crucibles - GOST 6563-75.

Laboratory porcelain glassware - GOST 9147-80.

Hydrofluoric acid (hydrofluoric acid) - according to GOST 10484-78.

Nitric acid - GOST 4461-77.

Water ammonia - GOST 3760-79, diluted 1:1.

Funnels are polyethylene.

Distilled water - GOST 6709-72.

Rectified ethyl alcohol - GOST 5962-67*.

Laboratory filter paper - GOST 12026-76.

2.3. Sample preparation

Samples of yttrated tungsten are cleaned of possible contamination by washing them several times with alcohol and then drying in an oven at a temperature of 50–70 °C for 10 min. Prepared samples are stored in glass bottles or test tubes with ground stoppers.

2.4. Conducting an analysis

A sample weighing 1 g is placed in a platinum cup with a capacity of 100 cm 3 , 25-30 cm 3 of hydrofluoric acid are added and nitric acid is carefully added dropwise until the metal dissolves.

After the complete dissolution of tungsten and the cessation of the release of nitrogen oxides, 30 cm 3 of water, heated to a temperature of 80-90 ° C, is added to the cup.

The precipitated solution is allowed to stand for 1 h, after which it is filtered through a polyethylene funnel. Before filtering, a small amount of adsorbent is placed on the filter.

After the sediment has been transferred to the filter, the bottom of the cup is wiped with a piece of a wet filter, and all the contents on it are poured onto the filter with hot water. Then the precipitate is washed five or six times with hot ammonia solution (60-70 °C) and two or three more times with hot water.

The washed precipitate is transferred to a pre-weighed porcelain crucible, dried in an oven at a temperature of 100-150 °C, and then calcined in a muffle furnace at a temperature of 650-700 °C to constant weight and weighed in the form of yttrium oxide.

2.5. Results processing

The mass fraction of yttrium oxide in percent is calculated by the formula

Y 2 0 3 = - 100, z J m l

where m is the mass of the calcined residue, g; rn - weight of the sample sample, g.

3. METHOD FOR DETERMINING THE CONTENT OF THORIUM DIOXIDE

The method establishes definitions of thorium dioxide in thoriated welded tungsten rods and electrodes.

3.1. Method Essence

The method is based on the formation of a precipitate of ThF 4 -4H 2 0 when a sample is dissolved in a mixture of hydrofluoric and nitric acids.

The error of the method at a mass fraction of thorium dioxide from 1.5% to 2% is 0.1%.

3.2. Reagents

Hydrofluoric acid (hydrofluoric) - GOST 10484-78.

Nitric acid according to GOST 4461-77.

Water ammonia according to GOST 3760-79, diluted 1:1.

Distilled water according to GOST 6709-72.

3.3. Sample preparation

The samples are boiled for several minutes in an alkali solution until the oxides are completely removed from the surface, washed in distilled water, and dried in an oven.

* On the territory of the Russian Federation, GOST R 51652-2000 applies.

3.4. Conducting an analysis

A sample weighing 1-2 g is placed in a platinum cup with a capacity of 100 cm 3 , 25-30 cm 3 of hydrofluoric acid are added and nitric acid is carefully added dropwise.

Before filtering, a small amount of adsorbent is placed on the filter.

The wet filter is transferred to a porcelain or platinum crucible preliminarily weighed to a constant weight, ashed, calcined at a temperature of 750-800 °C and weighed.

Simultaneously conduct a control experiment with all reagents.

3.5. Results processing

The mass fraction of thorium dioxide in percent is calculated by the formula

100,

where t is the mass of the sediment TYu 2, g;

mi is the mass of sediment in the control experiment, g; sh 2 - sample weight, g.

Editor R.G. Goverdovskaya Technical editor L.A. Guseva Proofreader R.A. Mentova Computer layout I.A. Naleykina

Ed. persons. No. 02354 dated 07/14/2000. Handed over to the set 29.09.2004. Signed for publication on 10/15/2004. Uel. pech.l. 0.93. Uch.-ed.l. 0.75.

Circulation 90 copies. C 4203. Order 908.

IPK Standards Publishing House, 14 Kolodezny per., Moscow, 107076. e-mail: Typed at the PC Publishing House

Printed in the branch of IPK Publishing house of standards - type. "Moscow printer", 105062 Moscow, Lyalin per., 6.

In gas-shielded fusion welding, a powerful electric arc is used as the main tool. In the arc, electrical energy is converted into thermal energy, the density of which is sufficient for local melting of the base metal. Under atmospheric conditions (21% O 2 + 78% N 2), the welding zone must be reliably protected from saturation of the weld metal with oxygen and nitrogen in the air, which, as a rule, worsen its properties. The shielding gases fed through the nozzle displace the air and thus protect the weld pool and the electrode. To fill the gap between the edges of the parts to be joined or to cut the edges and regulate the composition of the weld metal, filler metal or electrode wire is fed into the melting zone. The principle of arc welding with a non-consumable tungsten electrode in shielding gas is shown in (Fig. 3)

Fig.3
Principle of arc welding with non-consumable tungsten electrode in shielding gas

Argon welding is predominantly performed with a tungsten electrode in the inert gas Ar (TIG) and less often in He, in active gases N 2 and H 2 or in CO 2 with a carbon electrode. Welding can be performed without filler (IN) or with filler (INp) from solid and non-continuous flux-cored or activated wires. Depending on the type of current, the type of arcs, their number and external influences on it, welding methods can be distinguished: on direct, pulsed or alternating current, with an arc of direct, indirect and combined action; surface, submerged and penetrating arc; free and compressed; without exposure to an external magnetic field and in a magnetic field; with arc fluctuations and without them; at reduced pressure (in vacuum) and at elevated; single and multi-arc, etc.
The main types, structural elements and dimensions of welded joints made of steels, as well as alloys on iron-nickel and nickel bases, performed by gas-shielded arc welding are specified in GOST 14771
Depending on the level of mechanization and automation of the process, welding is distinguished:
- manual, in which all movements of the burner are performed manually;
- mechanized, in which the movements of the torch are performed manually, and the wire feed is mechanized (limited for TIG);
- automated, in which all movements of the torch and wire feed are mechanized, and the welding process is controlled by the operator-welder;
- automatic (robotic), in which the welding process is controlled without the direct participation of the operator-welder.

Influence of shielding gases on the technological properties of the arc.

Technological properties of the arc significantly depend on the physical and chemical properties of shielding gases, the composition of the electrode and welded metals, welding parameters and other conditions.
When arc welding is used:
- inert gases Ag and He and their mixtures Ag + He,
- active CO 2, N 2, H 2,
- mixtures of inert and active Ag + O 2, Ag + CO 2, Ag + O 2 + CO 2,
- mixtures of active gases CO 2 +O 2 .
The physical properties of shielding gases (Table 1) and the metal of the electrodes have a different effect on the properties of the arc with a non-consumable "hot" cathode (W-arc) and the arc with a consumable "cold" cathode (Me-arc).

Table 1

Technological properties of the arc

in protective gases, the following criteria are determined:
- electrical properties of the arc (near-electrode voltage drops, tension in the arc column, electron emission, ionization, etc.);
- arc stability;
- shape of the arc column, its spatial stability;
- melting of the electrode metal and the type of its transfer;
- spattering of the electrode metal and spatter weldability;
- melting of the base metal and formation of a seam (depth and shape of penetration, height and shape of the bead, cleanliness of its surface);
- effectiveness of welding zone protection (oxygen and nitrogen content in the weld, loss of alloying elements);
- resistance of the seam against the formation of porosity. Let us consider the influence of the physical properties of gases and welded metals (Table 1) on the technological properties of the arc.

welding equipment

By purpose, welding equipment is divided into universal, special and specialized. Let us briefly consider the principles of the layout of universal general-purpose welding equipment, which is mass-produced.
The welding equipment includes a welding power source and a welding machine. Its components and their functions are determined mainly by the level of mechanization and automation of the process, the parameters of the welding mode, the need for their installation and adjustment in the mode of setting up and welding.
The parameters can be divided into electrical (lc, Uc) and mechanical (d3H, Ld.c., Vc, dnn, Vnn, qr).
The main parameters of automated arc welding with a tungsten electrode in inert gases Ar or He (TIG) are:
1. Welding current Ic (~10...600 A);
2. Welding voltage 1) s (-10...30 V);
3. Welding speed Vc (-1.5...15 mm/s), (-5.4...54 m/h);
4. Diameter of non-consumable electrode d3H(~0.5...6.5 mm);
5. Adjustment arc length Ldu (~1...5 mm);
6. Filler wire diameter dnn (-2...6 mm);
7. Filler wire feed speed Vnn (-1.5...30 mm/s), (-5.4...108 m/h);
8. Consumption of protective gas qr (~ 1... 12 l/min).
Based on the principle of argon welding and process parameters, it is possible to determine the main functions of the equipment:
-supply to the arc of electrical energy and its regulation (lc, Uc);
- movement of the torch with welding speed (Vc) and its regulation;
- supply of filler (Vnn) wire to the welding zone and regulation of its speed;
- supply of protective gas (qr) to the welding zone and regulation of its consumption;
- setting the arc length (Ld.u.) and corrective movements of the burner;
- arc excitation and crater welding;
-automatic tracking along the welding line, etc.
When starting the welding machine, the control circuit must provide the following sequence of switching on the parts and mechanisms of the equipment:
1) shielding gas supply (qr), pre-purge of the gas supply system;
2) turning on the arc power source (Uxx.);
3) arc excitation (lc, Uc);
4) movement of the machine with welding speed (Vc)
At the end of welding, the sequence of switching off systems and mechanisms should ensure filling of the crater and protection of the cooling seam:
Argon welding is most often performed in a production room at a specially equipped workplace (welding station, installation, machine, RTK) and less often outside it. The welding station is equipped with local ventilation and is surrounded by shields or screens to protect others from arc radiation.
The welding station for manual arc welding with a tungsten electrode in argon (TIG) has:
- DC and/or AC welding current source;
- a burner or a set of burners for different currents;
- a device for initial arc ignition or for stabilization of an alternating current arc;
- equipment for controlling the welding cycle and gas protection;
a device for compensating or regulating the direct component of the welding current;

Welding consumables

The inert gases argon and helium are used in combination with tungsten electrodes. When tungsten is exposed to oxygen, the latter is intensively oxidized and destroyed. Argon is predominantly used, since it is cheaper than helium (argon is obtained from air), better protects the welding zone (heavier than air), and maintains a long (elastic) arc. The W-arc in helium has a higher temperature than the arc in argon, which makes it possible to weld aluminum of small thickness (foil) at direct current of direct polarity. According to GOST 10157-79, gaseous argon is produced in the highest and first grades. Helium is supplied according to TU 51-689-75 grades A, B, and C.
Tungsten electrodes for arc welding are manufactured according to GOST 23949-80 in the form of rods 75-300 mm long, 0.5-10 mm in diameter. To increase the spatial stability of the arc and the allowable current (Fig. 4), activating additives of yttrium oxides (EVI-1, EVI-2, EVI-3 grades), lanthanum oxides (EVL grade), less often thorium (EVT-15) are introduced into tungsten. Bars made of pure tungsten are produced under the EHF brand.

Fig.4

TIG welding is performed on butt, fillet, tee and lap joints in various welding positions. Types of preparation of edges and seams for arc welding of steels and nickel-based alloys with a non-consumable and consumable electrode in shielding gases are regulated by GOST 14771-76. TIG welding according to the standard is recommended for thicknesses up to 20 mm, which is associated with a small depth of penetration of the metal in one pass (up to 4 mm) and a low productivity of melting the filler and, consequently, filling the gap or cutting edges. Butt joints of steel up to 3-4 mm thick, and aluminum up to 5-6 mm thick are welded without beveled edges. TIG welding is often used for root-passing of small-diameter pipes "on the fly".
Low-melting metals Mg, A1, Si are recommended to be welded in the lower position. When welding refractory metals Mo, Nb, Zr, W, the thickness is limited to 2-3 mm. Alloys based on Mg, Al, Be are recommended to be welded on alternating current, so that cathodic cleaning of the weld pool from refractory oxide films occurs in the half cycles of reverse polarity. The remaining metals and alloys are recommended to be welded at direct current of direct polarity, since in this case there is a minimum heating of the tungsten electrode and maximum penetration of the base metal.
The main welding modes for various metal thicknesses and wire diameters are given in Table 1.

Tab.1

Special welding methods

To expand the technological capabilities of TIG welding, special narrow-purpose welding methods have been developed that make it possible to overcome the disadvantages of a typical one: low productivity, too wide seams, burn-through and increased warping when welding thin sheet metal, etc.
Welding AI, 77, Alloy Steels with Fluoride Flux allows to increase the depth of penetration and reduce the width of the joint, besides, it improves the formation of the root pass, eliminates porosity and contamination with oxide films.
Submerged Arc Welding at currents up to 650 A, it allows welding metal up to 10-14 mm thick in one pass (high-alloy steels, aluminum, titanium).
Three-phase arc welding on alternating current (two phases are supplied to the tungsten electrodes, one - to the product) provides high arc stability without an oscillator, increases the power and melting ability of a three-phase arc (up to 20 mm per pass on AI).
Pulsed arc welding ensures the concentration of the arc thermal effect in time, which reduces the HAZ and deformations, and has a favorable effect on solidification and weld formation on thin metal (thickness 0.4–2 mm).
Welding with hot filler(electronic filler heating) combines the high quality of TIG welding with the productivity of MIG welding. It is used for welding corrosion-resistant steels up to 50 mm thick.
Orbital welding of fixed pipe joints it is carried out both with and without an additive, with and without oscillations of the electrodes. The welding cycle is programmable. Backing rings are used to form a back bead, and with a pipe wall thickness of more than 3 mm, argon blowing with forming pressure is used.
Welding with an arc controlled by a magnetic field, allows you to increase the welding speed, reduce the HAZ and achieve a high quality of weld formation. The use of an arc rotated by a magnetic field is effective when welding pipes between themselves and with flanges, when welding pipes to tube sheets and other joints of a closed circuit. Tungsten or copper water-cooled electrodes are used. The movement of the arc causes a magnetic field transverse to the direction of welding. A magnetic field longitudinal with respect to the electrode axis causes spatial stabilization of the arc column and its rotation.