NB/T 47018.4-2017Technical delivery conditions of welding materials for pressure equipment - Part 4: Steel wires and fluxes for submerged arc welding (English PDF)

3.1 General

3.1.1

In addition to those specified in GB/T 5293-1999, GB/T 12470-2003 and GB/T 17854-1999, electrodes and fluxes for carbon steel, low-alloy steel and stainless steel submerged arc welding of pressure equipment shall meet the requirements of NB/T 47018.1 and this section.

3.1.2

The welding material quality certificate of submerged arc welding of pressure equipment shall include the following contents:

a) flux batch number and phase group electrode batch number, as well as electrode inspection, flux inspection and inspection results of deposited metal after assembly welding;

b) the type of flux (neutral, active) shall be indicated for the flux for carbon steel and low-alloy steel.

3.1.3

The batch number of electrodes and fluxes for submerged arc welding of pressure equipment is the same as that given in the quality certificate conforming to 3.1.2; when the batch number of electrode and/or flux is different from that given in the quality certificate, inspection shall be carried out according to the organization's quality assurance system, and the technical requirements shall not be lower than those given in this standard. Only after passing the test, can the batch number be used for welding pressure equipment.

3.2 Electrodes

In carbon steel and low-alloy steel electrodes for submerged arc welding, the sulfur content shall be no more than 0.015% while the phosphorus content shall be no more than 0.020%; in stainless steel electrodes, the sulfur content shall be no more than 0.015% while the phosphorus content shall be no more than 0.025%.

3.3 Fluxes

In fluxes, the sulfur content shall be no more than 0.035% while the phosphorus content shall be no more than 0.040%.

3.4 Chemical composition of the deposited metal of submerged arc welding material

After the assembly welding of commonly used electrodes and rods for submerged arc welding of pressure equipment, the specified sulfur and phosphorus contents in the deposited metal are shown in Table 1.

Table 1 Requirements for sulfur and phosphorus contents in deposited metal of the commonly used submerged arc welding material for pressure equipment

Standard Flux model S (mass fraction) /% P (mass fraction) /%

3.5 Mechanical properties of deposited metal of submerged arc welding material

3.5.1

The mechanical properties of deposited metal of the commonly used submerged arc welding material for pressure equipment shall meet those specified in Table 2.

3.5.2

The percentage elongation after fracture of the deposited metal tensile specimen shall meet those specified in GB/T 5293-1999, GB/T 12470-2003 and GB/T 17854-1999 respectively, and shall not be less than 18%.

Table 2 Mechanical properties of deposited metal of the commonly used submerged arc welding material for pressure equipment

Standard Flux model Tensile test Impact test

Tensile strength Rm/MPa Test temperature/°C Impact absorption power KV2/J 3.5.3 See Table 2 for the deposited metal Charpy V-notch impact test of commonly used submerged arc welding material for pressure equipment. Three deposited metal impact specimens are taken and the mean of their impact test results shall not be lower than that given in Table 2; while, the impact test result of one specimen is allowed to be lower than the specified value, but shall not be lower than the specified value by 70%.

3.5.4

When the bending specimen of deposited metal 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, and the corner opening defect of deposited metal may not be counted, but the length of corner opening defect caused by incomplete fusion, slag inclusion or other welding defects shall be counted.

For the deposited metal of which lower limit of specified percentage elongation after fracture A is less than 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.