Equipment for local and volumetric PWHT (heat treatment of welded joints)

GOST 34347-2017

08.04.2019 21:02:00
This state standard GOST 34347-2017 is designed to comply with the safety requirements of equipment operating under excessive pressure and to eliminate contradictions in the technical content of standards having the same distribution area.
ГОСТ 34347-2017 Сосуды и аппараты, работающие под давлением

This standard takes into account the main provisions of the Technical Regulation of the Customs Union TR CU 032/2013 "About the safety of equipment operating under excessive pressure", Directive 2014/68 / EC of the European Parliament and the Council of May 15, 2014 on the approximation of the laws of the Member States, concerning pressure equipment.

Heat treatment requirements are outlined in Section 5.11.

5.11 Heat treatment

5.11.1 Vessels (assembly units, parts) made of carbon and low-alloy steels (with the exception of steels listed in 5.11.3) made with welding, stamping or rolling are subject to obligatory heat treatment if:
a) the wall thickness of the cylindrical or conical element of the hull, bottom, flange or nozzle of the vessel in the place of their welded joint is more than 36 mm for carbon steels, more than 30 mm for manganese and manganese-silicon steels, and preheating before and during welding, with a wall thickness over than 38 mm;
b) the relative residual deformation of the cylindrical or conical elements of the vessel (pipe), operating under pressure, made of sheet steel by rolling (stamping), exceeds 5%.
c) vessels (assembly units, parts) are intended for operation in environments that cause corrosion cracking (liquid ammonia, solutions of caustic sodium and potassium, sodium nitrate, potassium, ammonium, calcium, ethanolamine. wet hydrogen sulfide-containing environments and od.);
d) the bottom of the vessels and other elements, regardless of thickness, made by cold stamping or cold flanking.

5.11.2 Welded joints of carbon, low-alloy manganese, manganese-silicon and chromium-molybdenum steels, performed by electric-arc welding, are subject to normalization and high tempering.

When electropack welding of stamped blanks and rolled elements from steel grades 16ГС, 09Г2С and 10Г2С1, designed to operate at a temperature not lower than -40 °C, normalization can be combined with heating for stamping with the end of stamping at a temperature of at least 700 °C.

5.11.3 Welded vessels (assembly units, parts) from steel grades 12MX, 12XM, 15XM, 12X1MF, 10X2M1A, 10X2M1A-A, 10X2M1A-VD, 10X2M1A-SH, 15X2MFA, 15X2MFA-A, 1X2M1, 15X5, XX, X, X, X 15Х5ВФ, 12Х8ВФ, Х9М and of two-layer steels with a main layer of steel grades 12МХ, 12ХМ, 20Х2МА must be subjected to heat treatment according to the regime specified in the regulatory document.

5.11.4 Vessels (assembly units, parts) made of steel grades 08X18H10T. 08Х16Н12Б and other austenitic steels stabilized by titanium or niobium, intended for operation in environments causing corrosion cracking, as well as at temperatures above 350 °C in environments causing intergranular corrosion, it is necessary to heat-treat according to conditions specified in the regulatory document. The need for such heat treatment is indicated in the design documentation.

5.11.5 The necessity and type of heat treatment of vessels (assembly units, parts) made of two-layer steel must be determined in accordance with the requirements of a), b), d) 5.11.1. 5.11.2,5.11.3.

When determining the thickness of the welded element, the main layer thickness of the two-layer steel is adopted.

If the design documentation contains requirements for resistance to intergranular corrosion, the welding technology and heat treatment mode of welded joints of two-layer steels should ensure corrosion resistance of welded joints layer to intergranular corrosion.

5.11.6 Parts made of carbon and low-alloy manganese-silicon steels, stamped (rolled), with final stamping (rolling) at a temperature of at least 700 °C. Parts and details made of austenitic chromium-nickel steels stamped (rolled) at a temperature not lower than 850 °C are not subjected to heat treatment.

Bottoms and other hot-stamped (rolled) elements made of steel grades 09Г2С, 10Г2С1, operating at temperatures from -40 C to -70 C should be subjected to heat treatment - normalization or hardening and high stress relieving, regardless of the temperature at which stamping is completed.

Bottoms and other elements from low-alloy steels of grades 12XM and 12MX are stamped (rolled) hot with the end of stamping (rolling) at a temperature of at least 800 ° C; it is allowed to subject only stress relieving (without normalization).

The manufacturing technology of bottoms and other stamped elements should provide the necessary mechanical properties specified in the standards or specifications * for the material, and if there is a requirement in the design documentation, resistant to intergranular corrosion should be, too.

5.11.7 Bottoms and other elements made of austenitic-grade corrosion-resistant steels by cold stamping or cold flanging should be heat treated (causing or stabilizing) if they work in environments that cause corrosion cracking. In the remaining 8 cases, heat treatment is not allowed. not less than 30% when the degree of deformation in the cold state is not more than 15%.

5.11.8 Cold-bent sections of pipes made of carbon and low alloy steels are subject to heat treatment if the ratio of the average bending radius to the nominal outer diameter of the pipe is less than 3.5, and the ratio of the nominal pipe wall thickness to its nominal diameter exceeds 0.05.

5.11.9 Welding of internal and external devices to vessels subjected to heat treatment must be carried out before the heat treatment of the vessel.

Welding of internal and external devices without subsequent heat treatment to vessels heat-treated in accordance with a), b) of 5.11.1 is allowed, provided that the weld cathetus is not more than 8 mm.

It is allowed to weld external devices on the assembly site to special overlays welded to the vessel body and underwent heat treatment with it at the manufacturer without subsequent heat treatment of the assembly welds.

5.11.10 Local heat treatment of welded joints of vessels is allowed, during which uniform heating and cooling along the entire length of the seam and adjacent zones of the base metal must be ensured.

5.11.11 Volumetric heat treatment is carried out in furnaces or by a method of heating from the inside by supplying heaters to the internal space (volume) of the apparatus isolated from the outside.

At the same time, measures must be taken to protect the vessel (assembly unit, part) from deformation caused by local overheating, improper installation of the vessel, the action of its own weight, and the metal should be protected from the effects of environments that provoke various types of corrosion.

5.11.12 The metal properties of the shells, bottoms, pipes, gratings after all heat treatment cycles must comply with the requirements of standards (specifications *) for the delivery of materials.

The mechanical properties of the base metal after heat treatment cannot be controlled if the tempering temperature does not exceed 650 *C for carbon and low alloy manganese and manganese-silicon steels (Ст3, 16K, 18K, 20K, 22K, 20KA, 20Юч, 16ГС, 17ГС, 17Г1С, 09Г2С, 10Г2С1) and their foreign analogues.

5.11.13 Types and modes of heat treatment of vessels (assembly units, parts) must comply with the requirements of app. 4.

5.11.14 To determine the degree of embrittlement during operation of the base metal and welded joints of 10Х2M1A-A, 10Х2M1A (10Х2M1A-ВД, 10Kh2M1A-Ш), 12Kh2MФA, 15Х2MФA-A steels, tests for step cooling are carried out if indicated in the documentation. The recommended method for step cooling heat treatment is given in app. Н.

5.11.15 The heat treatment of the welded joint can be carried out no more than three times without taking into account intermediate stress relieving.

You can download GOST 34347-2017 here.

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