Equipment for local and volumetric PWHT (heat treatment of welded joints)
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Rules for the nuclear industry PNAE G

03.09.2019 08:18:00
Safety requirements vary from industry to industry. The nuclear industry has some of the highest demands.

For example, PNAE G-7-009-89 applies to welding and surfacing of equipment and pipelines, on which the Rules for the design and safe operation of equipment and pipelines of nuclear power plants are spreaded.

These rules establish the basic requirements for welding equipment, welding materials, preparation and assembly for welding, welding, surfacing, heat treatment of welded joints and deposited parts (products), safety measures, as well as the main recommended types of welded joints and welding modes (surfacing).

Repair of structures, in operation, should be carried out according to the technological process drawn up in accordance with the requirements of these rules, taking into account the specifics of the structure being repaired.

Heat treatment requirements are contained in paragraph 8.

In local heat treatment of welded joints, the general zone of controlled metal heating consists of the main and additional zones and should include a welded joint and sections of the main metal adjacent to its edges.

The main zone of controlled heating includes a welded joint and sections of the main metal adjacent to its edges at distances equal to the nominal thicknesses of the welded parts with a thickness of parts up to 50 mm (inclusive), and with a larger thickness of parts - at a distance of 50 mm. Within the main zone, the temperature of the metal during the aging process should correspond to the set stress relieving temperature (austenization) taking into account the established tolerances.

An additional zone of controlled heating includes sections of the common zone main metal that are not included in the main zone. Within the additional zone, a decrease in the temperature of the metal during the aging process is allowed in comparison with the set stress relieving temperature (austenization), but not more than 50 °C from the minimum allowable temperature (taking into account the minus tolerance).

The temperature of the welded joints stress relieving from steels of various grades, for which the indications of Table. 15 provide a different temperature of stress relieving is seted by. In this case, the nominal temperature of the stress relieving should not fall beyond the interval between the nominal temperatures determined in accordance with the instructions of the table. 15 for stress relieving of welded joints of parts from steels of the corresponding grades, and should not meet the requirements of subdivision. 8.12 and 8.13.

Таблица 15

Stress relieving temperature of welded joints made by arc or electron beam welding.


Steel grade

Thikness, mm

Stress relieving temperature, °С

Intermediate

Final

Nominal

Critacal deviations

Nominal

Critacal deviations

1

2

3

4

5

6

Ст3сп5, 10, 15, 15Л, 20, 20Л

Up to 36 (inclusive)

-

-

-

-

Over 36

610

±20

630

±20

20К, 22К, 25Л

Up to 36 (inclusive)

-

-

-

-

Over 36

620

±20

640

+20

-10

06X12Н3Д

Up to 10 (inclusive)

-

-

-

-

Over 10

620

±10

640

+10

-15

15ГС, 16ГС, 20ГСЛ, 09Г2С, 10ХСНД, 10ХН1М

Up to 30 (inclusive)

-

-

-

-

Over 30

630

±15

650

±15

10ГН2МФА, 10ГН2МФАЛ

Up to 10 (inclusive)

-

-

-

-

Over 10

620

±10

650

±10

15Х2НМФА, 15Х2НМФА-А, 15Х3НМФА, 15Х3НМФА-А

Regardless of thickness

620

±10

650

±10

07X16Н4Б

Same

-

-

650

±10

16ГНМА, 15ГНМФА

Up to 25

-

-

-

-

Over 25

640

±15

660

±15

12Х2МФА, 15Х2МФА, 15Х2МФА-А, 18Х2МФА

Regardless of thickness

655

±10

670

±10

05X12Н2М

Same

-

-

670

±20

20ХМА, 20ХМ, 20ХМЛ

Same

670

115

700

±15

12МХ, 12ХМ, 15ХМ

Up to 10 (inclusive)

-

-

-

-

Over 10

690

±20

710

±20

10Х2М, 12Х2М1Л,

08X13, 12X13

Up to 6 (inclusive)

-

-

-

-

Over 6

690

±20

710

±20

12ХМФ, 20ХМФЛ

Up to 6 (inclusive)

-

-

-

-

Over 6

715

±15

730

±120

15Х1М1Ф, 15Х1М1ФЛ

Up to 6 (inclusive)

-

-

-

-

Over 6

725

±15

740

±15

12Х11В2МФ

Up to 3 (inclusive)

-

-

-

-

Over 3

730

±15

750

±15

Notes:

1. The nominal thickness of the welded parts should be taken for butt welded joints as their nominal thickness in the area immediately adjacent to the welded joint.

2. In case of local heat treatment (stress relieving) of welded parts made of steel grades Ст3сп5, 10, 15, 15Л, 20, 20Л, 20К, 22К, 25Л, 15ГС, 16ГС, 20ГСА, 09Г2С, 10ХСНД, 10ХН1М, 10ГН2МФА, 10ГН2МФЛ, 16ГНМА, 15ГНМФА, 12МХ, 12Х, 15Х, 20ХМЛ, 12Х1МФ, 20ХМФЛ, 15Х1М1Ф и 15Х1М1ФЛ, in agreement with the parent material science organization, it is possible to increase total maximum deviations from the nominal stress relieving temperatures indicated in the table up to 40 °C is allowed.

3. By agreement with the parent material science organization, it is allowed not to conduct high stress relieving of welded joints of 10ХСНД and 10ХН1М steels with a nominal wall thickness up to 40 mm (inclusive).

4. In the cases stipulated by the project, for welded joints of parts from steel grades Ст3сп5 and 20, an increase in the upper limit of the temperature of the final stress relieving to 660 °C is allowed.

5.  It is allowed to carry out an intermediate stress relieving In the cases stipulated by the project of welded parts made of steel grades 12X2MFA and 15X2MFA at a temperature of 650 ± 10 °C.



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