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NB/T 47018-2017 consists of the following five sections under the general title of Technical permission of welding materials for pressure equipment:
——Section 1: General rule;
——Section 2: Electrodes for steel;
——Section 3: Steel electrodes and rods for gas shielded arc welding;
——Section 4: Electrodes and fluxes for submerged arc welding;
——Section 5: Stainless steel strip electrodes and fluxes for overlay welding.
This is Section 5 of NB/T 47018-2017.
This section is developed in accordance with the rules given in GB/T 1.1-2009 Directives for standardization - Part 1: Structure and drafting of standards.
This section is a revision of NB/T 47018.5-2011 Technical permission of welding materials for pressure equipment - Section 5: Stainless steel strip electrodes and fluxes for overlay welding. The following main technical changes have been made with respect to NB/T 47018.5-2011:
——3 strip electrode models, i.e. EQ317L, EQ2205 and EQ2209, are added;
——3 surfacing metal models for flux/strip electrode combination, i.e. FX317L-E, FX2205-E and FX2209-E, are added;
——Requirements for used strip electrodes when inspecting the chemical composition of FX317L-E, FX2205-E and FX2209-E surfacing metals are added;
——Application requirements for quality certificate and its inspection contents as well as batch number are added.
This section was proposed by and is under the jurisdiction of the National Technical Committee on Boilers and Pressure Vessels of Standardization Administration of China (SAC/TC 262).
The previous edition of this section is as follows:
——NB/T 47018.5-2011.
Technical permission of welding materials for pressure equipment - Section 5: Stainless steel strip electrodes and fluxes for overlay welding
1 Scope
This section of NB/T 47018-2017 specifies the model, technical requirements, test methods, inspection rules, packaging and marking as well as product identification of stainless steel surfacing metal for overlay welding (surfacing).
This section is applicable to pressure equipment submerged arc or electroslag corrosion resistant overlay welding
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 223 (all parts) Methods for chemical analysis of iron, steel and alloy
GB/T 1954 Methods of measurement for ferrite content in austenitic Cr-Ni stainless steel weld metals
GB/T 2653 Bend test methods on welded joints
GB/T 4334 Corrosion of metals and alloys - Test methods for intergranular corrosion of stainless steels
GB/T 17854-1999 Stainless steel electrodes and fluxes for submerged arc welding
NB/T 47013.3 Nondestructive testing of pressure equipment - Part 3: Ultrasonic testing
NB/T 47013.5 Nondestructive testing of pressure equipment - Part 5: Penetrant testing
NB/T 47018.1 Technical permission of welding materials for pressure equipment - Section 1: General rule
3 Model
3.1 Strip electrode model
3.1.1 The strip electrode model is divided according to its chemical composition.
3.1.2 The strip electrode model consists of two parts.
a) Letters "EQ" in the first part represent the strip electrode;
b) The second part is the number or combination of number and letter after “EQ”, representing the chemical composition classification, where “L” indicates a low carbon content, and if there is other chemical composition with special requirements, the chemical composition is expressed by element symbol and placed at the back position.
3.1.3 Example of strip electrode model is as follows:
3.2 Surfacing metal model
3.2.1 The surfacing metal mode is divided according to the chemical composition of surfacing metal after the strip electrode-flux assembly.
3.2.2 The surfacing metal mode usually consists of four parts. Letter "F” represents the flux; the letter after "F" represents the overlay welding method, and the number or combination of number and letter after "F" represents the type code of the chemical composition of surfacing metal, where "L" indicates a lower carbon content, and if there is other chemical composition with special requirements, the chemical composition is expressed by element symbol and placed after the number, and the position code of the overlay welding layer is placed after "-".
3.2.3 Example of surfacing metal model is as follows:
4 Technical requirements
4.1 General
In addition to the requirements of NB/T 47018.1, the stainless steel strip electrodes and fluxes for overlay welding of pressure equipment shall also meet the requirements of this section.
4.2 Strip electrode
4.2.1 The strip electrode shall have a smooth surface and be free from defects such as burrs, cracks, creases and delamination, but scratches and local defects with a depth not exceeding the thickness deviation ±0.025mm are allowed.
4.2.2 The standard width of the strip electrode is specified as 30mm, 60mm, 90mm and 120mm, and the standard thickness of the strip electrode is specified as 0.5mm. Strip electrodes of other specifications may be supplied through negotiation between the supplier and the purchaser. The permissible deviation of width and thickness of strip electrode is as shown in Table 1.
Table 1 Thickness and width of strip electrode and their permissible deviation In: mm
Item Allowable deviation
Width ±0.20
Thickness ±0.05
4.2.3 Joint is not allowed for finished strip electrode.
4.2.4 The straightness requirements of trimming strip electrode are given in Table 2.
Table 2 Straightness of trimming strip electrode In: mm
Strip electrode width Length Permissible deviation
≤60 1 000 ≤3.0
>60 1 000 ≤2.0
4.2.5 The chemical composition of strip electrode shall meet those specified in Table 3.
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Table 3 Model and chemical composition (mass fraction) (%) of strip electrode
Strip electrode model C Si Mn P S Ni Cr Mo Cu Nb N
4.3 Flux for overlay welding
4.3.1 The flux for overlay welding is granular and can pass the supply pipe, valve and nozzle of the standard welding equipment freely. The granularity is divided into two grades: ordinary granularity and fine granularity. The limit range of granularity shall meet those specified in Table 4, but fluxes of other granularities are allowed to be supplied according to the agreement between the supplier and the purchaser.
Table 4 Limit range of flux granularity
Category of flux granularity Ordinary granularity Fine granularity
Limit range of granularity <0.450mm (40 meshes) ≤5% <0.180mm (80 meshes) ≤5%
>2.50mm (8 meshes) ≤2% >2.00mm (10 meshes) ≤2%
4.3.2 The mass of mechanical inclusions (scrap irons, raw material particle, ferroalloy bead and other sundries) in flux for overlay welding shall not exceed 0.30%.
4.3.3 Sulfur and phosphorus contents in the flux for overlay welding: the sulfur content in the flux for overlay welding shall not exceed 0.035%, and the phosphorus content shall not exceed 0.040%.
4.3.4 Assembly of flux for overlay welding and strip electrode: when reasonable overlay welding process parameters are adopted for overlay welding, the overlay welding process shall be kept stable and the weld bead shall be smooth, aesthetic and easy for slag removal. The weld beads as well as weld bead and base metal shall be well fused.
Foreword i
1 Scope
2 Normative references
3 Model
4 Technical requirements
5 Test methods
6 Inspection rules
7 Quality certificate
8 Packaging
9 Product identification
