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Submerged arc welding consumables. Part 2 - specifications

   

Job Knowledge 88

Part 1
Part 3

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Of all the arc welding processes, only submerged arc welding uses two completely separate components, both of which may have a major effect on the mechanical properties of the weld deposit. This makes the specifying of consumables somewhat complicated. It will not be possible therefore to cover all the alloy types in this brief article which will cover the carbon, carbon-manganese and low alloy structural steels only.

BS EN ISO 14171:2010 is the specification for Welding consumables: Solid wire electrodes, tubular cored electrodes and electrode/flux combinations for submerged arc welding of non alloy and fine grain steels. This standard replaces BS EN 756:2004.

The specification covers the classification of the wire chemical composition and the wire/flux combination. It also specifies the mechanical properties of all weld metal deposits in the as-welded condition.

This standard is a combined specification providing for classification utilizing a system based upon the yield strength and the average impact energy for weld metal of 47 J, or utilizing a system based upon the tensile strength and the average impact energy for weld metal of 27 J.

The classification is composed of:

  • A reference to the standard 'ISO 14171'
  • A symbol 'A' if the classification is based on yield strength and average impact energy is 47J or 'B' if the classification is based on tensile strength average impact energy is 27J.

And of five parts, plus a sixth supplementary part:

Part 1. A symbol indicating the process - in the case of submerged arc welding this is 'S'.
Part 2. Two digits indicating either the tensile properties of a multi-run deposit or the tensile properties of the parent metal to be welded using a two run technique - see Tables 1 and 2.

Table 1A. Symbols for tensile properties - multi-run technique (classification based on yield strength and average impact energy 47J)

Multi-run Tensile Properties
SymbolMin. Yield N/mm 2Min. UTS N/mm 2Min. Elongation %
35 355 440 - 570 22
38 380 470 - 600 20
42 420 500 - 640 20
46 460 530 - 680 20
50 500 560 - 720 18

Table 1B. Symbols for tensile properties - multi-run technique (classification based on tensile strength and average impact energy 27J)

Multi-run Tensile Properties
SymbolMin. Yield N/mm 2Min. UTS N/mm 2Min. Elongation %
43X 330 430 - 600 20
49X 390 490 - 670 18
55X 460 550 - 740 17
57X 490 570 - 770 17

Note: 'X' is 'A' or 'P', where 'A' indicates testing in the as-welded condition and 'P' indicates testing in the post-weld heat-treated condition.

Table 2A. Symbols for tensile properties - two-run technique (classification based on yield strength and average impact energy 47J)

Two-Run Tensile Properties
SymbolMin. Yield Parent Metal N/mm 2Min. Tensile Strength of Welded Joint N/mm 2
2T 275 370
3T 355 470
4T 420 520
5T 500 600

Table 2B. Symbols for tensile properties - two-run technique (classification based on tensile strength and average impact energy 27J)

SymbolMin. Tensile Strength of Welded Joint N/mm 2
43S 430
49S 490
55S 550
57S 570

Note that the two-run technique has two tensile results specified; one for the minimum yield strength of the parent metal, one for the tensile strength of the welded joint.

Part 3. Table 3 gives the temperature at which the average Charpy-V impact value of 47J or 27J may be achieved.

Table 3. Symbol for Charpy-V impact properties

SymbolTemp. for Min Impact Energy 47J or 27J at °C
Z No requirements
A +20
0 0
2 -20
3 -30
4 -40
5 -50
6 -60
7 -70
8 -80
9 -90
10 -100

Part 4. The symbol for welding flux type shall be in accordance with ISO 14174.

Flux type symbol

Flux TypeSymbol
manganese-silicate MS
calcium-silicate CS
zirconium-silicate ZS
rutile-silicate RS
aluminate-rutile AR
aluminate-basic AB
aluminate-silicate AS
aluminate-fluoride basic AF
fluoride-basic FB
any other type Z

Part 5. Tables 4 and 5 in ISO 14171 contain a listing of the chemical composition of 22 wires and are too lengthy to include in full in this article. The wires all contain a maximum carbon content of 0.15% and range from plain carbon, through C-Mn, C-Mo, Mn-Mo to Ni and Ni-Mo. All are prefixed 'S' followed by a number from 1 to 4 denoting from 0.5% Mn (1) to 2% Mn (4). The addition of nickel and/or molybdenum is denoted by the chemical symbol of the alloy addition being included. Thus an S3 wire contains 1.5% Mn, an S2Ni1Mo 1%.

Part 6. (optional) The standards also provides symbols symbols given an optional symbol indicating the diffusible hydrogen content of the weld metal obtained in accordance with ISO 3690 (see Table 6 in the standard).

Examples of designations:

The designation for an electrode/flux combination for submerged arc welding for multi-run technique depositing a weld metal with a minimum yield strength of 460 MPa (46) and a minimum average impact energy of 47 J at -30°C (3) produced with an aluminate-basic flux (AB) and a wire S2 would be:

ISO 14171-A-S 46 3 AB S2

In addition to BS EN ISO 14171 which specifies the mechanical properties expected from a particular flux/wire combination, there is an additional specification, BS EN ISO 14174:2012, that specifies the fluxes in greater detail, including the application for which a flux may be used. The specification uses a total of seven symbols, four being compulsory and three optional. The first symbol,'S', identifies the flux as being intended for submerged arc welding and the second the method of manufacture. This may be 'F', a fused flux; 'A', an agglomerated flux and 'M', a mixture of fused and agglomerated. The third part gives an indication of the chemical constituents and uses the same notation as in Table 4 above. In addition BS EN 760 gives a range of percentages for each of the constituents in Table 1.

The fourth part gives a symbol for the application(s), Class 1 being intended for the welding of carbon and low alloy steels, including high strength structural and creep resistant steels. There is no alloying from this class of flux. Class 2 fluxes are for the welding of, and the surfacing with, stainless and heat resisting steels and nickel alloys. Class 3 is for use with hard surfacing weld metals, the flux providing such elements as carbon, chromium and molybdenum to the weld deposit.

The remaining three symbols are not compulsory and comprise, firstly, a number or chemical element symbol that defines what is termed in the specification as the 'metallurgical behaviour' of the three classes of flux mentioned above. Two digits then specify the pick-up or loss of silicon and manganese (in this order) to be expected when welding carbon or low alloy steels using flux Class 1, as shown in Table 5 below. Flux Classes 2 and 3 may be characterised by the use of a chemical symbol to identify the alloying element being added via the flux, eg Cr, if the flux is chromium compensating.

The current type is indicated by the addition of DC or AC to the symbols and finally an 'H', followed by a number, gives the weld metal hydrogen level expected from a correctly dried or baked flux eg H5.

A designation for a flux supplied in accordance with BS EN 760 may therefore be S A AF 1 55 DC H5 for an agglomerated alumina-calcium fluoride basic flux intended for the welding of carbon or low alloy steels, no pick-up or loss of silicon or manganese, used with DC welding current and with a hydrogen content of less than 5mls/100gms weld metal.

It must be remembered that the properties given by these designations are obtained from as welded, all weld metal specimens deposited using standard welding parameters of current, voltage and travel speed.

The properties achieved in a production weld may be entirely different due to the effects of dilution from the parent metal, higher or lower heat input, different wire diameters, preheat and interpass temperatures and post weld heat treatment. It is essential, therefore, that the suitability of a flux/wire combination is confirmed by procedure qualification testing.

Note also that flux/wire combinations supplied to the same specification designation by different manufacturers may not necessarily provide similar mechanical properties or weld cleanliness.

This article was written by Gene Mathers and Marcello Consonni.

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