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NB/T 47018-2017 consists of the following five sections under the general title 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 2 of NB/T 47018-2017.
This standard 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 47018.2-2011 Technical permission of welding materials for pressure equipment - Section 2: Electrodes for steel. The following main technical changes have been made with respect to NB/T 47018.2-2011:
——According to the requirements of new national standard (Edition 2012) for electrodes, the previous GB/T 5117 Carbon steel covered electrodes is renamed as Covered electrodes for manual metal arc welding of non-alloy and fine grain steels, the previous GB/T 5118 Low alloy steel covered electrodes is renamed as Covered electrodes for manual metal arc welding of creep-resisting steels, and GB/T 32533 Covered electrodes for manual metal arc welding of high-strength steels is added;
——Seven electrode models (E4303, E4315, E4316, E5015, E5016, E5018 and E5515-G7) are remained for the covered electrodes for manual metal arc welding of non-alloy and fine grain steels, and they are the same as the electrode models in the new standard, however, the technical requirements are changed; five electrode models are remained, their corresponding models changed according to the new standard are given in the brackets: E5015-E (E5015-N1), E5016-E (E5016-N1), E5515-E (-40℃) (E5515-N1), E5516-E (E5516-N1), and E5515-E (-50℃) (E5515-N3); 23 electrode models are added in total: E4318, E5516-G, E5518-G (-30℃), E5018-G (-40℃), E5518-G (-40℃), E5018-1, E5015-G, E5016-G, E5015-N2, E5515-N2, E5018-N2, E5516-N3, E5518-N3, E5515-N5, E5516-N5, E5518-N5, E5015-G (-70℃), E5015-N5, E5016-N5, E5018-N5, E5015-N7, E5016-N7, and E5018-N7.
——The following five electrode models are remained for the covered electrodes for manual metal arc welding of creep-resisting steels, their corresponding models changed according to the new standard are given in the brackets: E5515-B1 (E55××-CM), E5515-B2 (E55××-1CM), E5515-B2-V (E55××-1CMV), E6015-B3 (E62××-2C1M) and E5MoV-15 (E55××-5CMV); eight electrode models are added: E50××-1M3, E52××-1CML, E55××-2C1ML, E55××-2CMWVB, E55××-2CMVNb, E62××-2C1MV, E62××-3C1MV and E50××-G;
——The following 18 electrode models are remained for stainless steel covered electrodes: E308-15, E308-16, E308L-16, E309-15, E309-16, E309L-16, E309Mo-16, E309MoL-16, E316-15, E316-16, E316L-16, E317-16, E317L-16, E318-16, E347-15, E347-16, E410-15 and E410-16; according to the model preparation requirements in the new standard, only E309MoL-16 is changed to E309LMo-16, other electrode models are the same as those given in the new standard; moreover, four electrode models are added: E310-××, E310Mo-××, E347L-×× and E2209-××;
——Three electrode models are remained for the covered electrodes for manual metal arc welding of high-strength steels, the corresponding models in the new standard are given in the brackets: E6015-D1 (E5915-G, -30℃), E6016-D1 (E5916-G, -30℃) andE6015-E (E6215-3M2); 20 electrode models are added: E6215-N2M1, E6216-N2M1, E5918-G (-30℃), E5915-G (-40℃), E5916-G (-40℃), E5918-G (-40℃), E6216-N4M1, E6215-G (-40℃), E6216-G (-40℃), E6218-G (-40℃), E6215-G (-50℃), E6216-G (-50℃), E6218-G (-50℃), E6218-3M2, E6218-3M3, E6215-N5M1, E6216-N5M1, E6215-G (-60℃), E6216-G (-60℃) and E6218-G (-60℃);
——The acceptance criteria for percentage elongation after fracture of deposited metal tensile specimen are changed;
——Except for stainless steel covered electrodes, the impact test requirements for deposited metal of all new electrode models are re-defined;
——Except for stainless steel covered electrodes, the diffusible hydrogen content in all electrodes shall be determined by mercury method or thermal conductivity method, the acceptance criteria are specified, and the determination method of water content in welding electrode covering is no longer used;
——Transverse bending specimen is allowed in bend test, and the requirement that retest is allowed after increasing bending center diameter is added;
——Annex A - “A comparison of electrode models” is 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 editions of this section are as follows:
——JB/T 4747-2002;
——NB/T 47018.2-2011.
Technical permission of welding materials for pressure equipment
Section 2: Electrodes for steel
1 Scope
This section of NB/T 47018-2017 specifies the technical requirements, bend test of deposited metal, and product identification of electrodes for steel.
This section is applicable to the covered electrodes for manual metal arc welding of non-alloy and fine grain steels, creep-resisting steels and high-strength steels and the stainless steel covered electrodes for pressure equipment.
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 983-1995 Stainless steel covered electrodes
GB/T 983 Covered electrodes for manual metal arc welding of stainless and heat-resisting steels
GB/T 2653 Bend test methods on welded joints
GB/T 3965 Determination of diffusible hydrogen in deposited metal
GB/T 5117-1995 Carbon steel covered electrodes
GB/T 5117 Covered electrodes for manual metal arc welding of non-alloy and fine grain steels
GB/T 5118-1995 Low alloy steel covered electrodes
GB/T 5118 Covered electrodes for manual metal arc welding of creep-resisting steels
GB/T 32533 Covered electrodes for manual metal arc welding of high-strength steels
NB/T 47013.2 Nondestructive testing of pressure equipment - Part 2: Radiographic testing
NB/T 47014 Welding procedure qualification for pressure equipment
NB/T 47018.1 Technical permission of welding materials for pressure equipment - Part 1: General rule
3 Technical requirements
3.1 General
In addition to the requirements of GB/T 983, GB/T 5117, GB/T 5118 and GB/T 32533, the electrodes for steel used for pressure equipment shall also meet the requirements of NB/T 47018.1 and this section.
See Annex A for the correspondence between the electrode models in this section and those in other relevant standards.
3.2 Electrode eccentricity
3.2.1 For the electrode with the diameter not greater than 2.5mm, its eccentricity shall not be greater than 5%; however, the eccentricity of 5% of tested electrodes are allowed to be greater than 5% but shall not be greater than 7%.
3.2.2 For the electrodes with diameter of 3.2mm and 4.0mm, the eccentricity shall not be greater than 4%; however, the eccentricity of 5% of tested electrodes are allowed to be greater than 4% but shall not be greater than 5%.
3.2.3 For electrodes with diameter not less than 5.0mm, the eccentricity shall not be greater than 3%; however, the eccentricity of 5% of tested electrodes are allowed to be greater than 3% but shall not be greater than 4%.
3.3 Chemical composition of deposited metal
See Table 1 for the requirements for sulfur and phosphorus contents in deposited metal of electrodes for steel commonly used for pressure equipment.
Table 1 Requirements for sulfur and phosphorus contents in deposited metal of electrodes for steel commonly used for pressure equipment
3.4 Mechanical properties of deposited metal
3.4.1 The difference between the tensile strength of covered electrodes for manual metal arc welding of non-alloy and fine grain steels, creep-resisting steels and high-strength steels and the lower limits specified in GB/T 5117, GB/T 5118 and GB/T 32533 shall not exceed 120MPa, wherein, the difference between the tensile strength of deposited metal of covered electrodes for manual metal arc welding of creep-resisting steels with diameter not greater than 2.5mm and the lower limit specified in GB/T 5118 shall not exceed 130MPa.
3.4.2 The percentage elongation after fracture of deposited metal tensile specimen shall meet the requirements of GB/T 9831, GB/W 5117, GB/T 5118 and GB/T 32533 respectively, and shall not be less than 18%.
3.4.3 See Table 2 for the Charpy V-notch impact test requirements for deposited metal of electrodes for steel commonly used for pressure equipment. Take three impact specimens, the mean of their impact test results shall not be less than the specified value, the impact test result of only one specimen is allowed to be less than the specified value but shall not be less than 70% of the latter.
3.4.4 When the deposited metal bending specimen is bent to the angle specified in Table 3, the opening defect with single length larger than 3mm is not allowed in any direction in the deposited metal on a stretching plane. The corner opening defect of the deposited metal may not be counted, but the length of the corner opening defect caused by non-fusion, slag or other internal defects shall be counted.
For the deposited metal whose lower limit of the specified percentage elongation after fracture A is less 20%, if it is unqualified upon bend test according to those specified in Table 3, and the measured value is less than 20%, the diameter of the bending center is allowed to be increased for retesting. The diameter of the bending center is equal to (A is the lower limit of the specified percentage elongation after fracture multiplied by 100), and the distance between the supports is equal to the diameter plus 23mm.
Foreword II
1 Scope
2 Normative references
3 Technical requirements
4 Bend test of deposited metal
5 Product Identification
Annex A (Informative) A comparison of electrode models
