welding consumables - part 5 - job knowledge 86

4/3/2014 Welding consumables - part 5 - Job knowledge 86

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Welding consumables Part 5 - MIG/MAG and cored carbonsteel wires

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To ensure that there is a consistency in composition and propertiesbetween wires from a variety of manufacturers, specifications havebeen produced that enable a wire to be easily and uniquely identifiedby assigning the consumable a 'classification', a unique identificationthat is universally recognised.

The two schemes that are dealt with in this article are the EN/ISOmethod and the AWS scheme. There are such a large number ofspecifications covering the whole range of ferrous and non-ferrous filler metals, both solid wire and cored, that itwill not be possible to describe all of these here. This article therefore reviews just the carbon steelspecifications.

The identification of the solid wires is relatively simple, as the chemical composition is the major variablealthough both the EN/ISO and the AWS specifications detail the strength that may be expected from an all-welddeposit carried out using parameters given in the specification. It should be remembered, however, that mostwelds will contain some parent metal and that the welding parameters to be used in production may bedifferent from those used in the test. The result is that the mechanical properties of a weld can be significantlydifferent from those quoted by the wire supplier, hence the need to always perform a procedure qualificationtest when strength is important. In addition, the mechanical properties specified in the full designation includethe yield strength. (In the EN/ISO specifications, the classification may indicate either yield or ultimate tensilestrength).

When selecting a wire remember that the yield and ultimate tensile strengths are very close together in weldmetal but can be widely separated in parent metal. A filler metal that is selected because its yield strengthmatches that of the parent metal may not, therefore, match the parent metal on ultimate tensile strength. Thismay cause the cross joint tensile specimens to fail during procedure qualification testing or perhaps in service.

The EN/ISO specification for non-alloyed steel solid wires is BS EN ISO 14341. This specification classifies wireelectrodes in the as-welded condition and in the post weld heat-treated condition, based on classificationsystem, strength, Charpy-V impact strength, shielding gas and composition. The classification utilises twosystems based either on the yield strength (System A) or the tensile strength (System B):

System A - based on the yield strength and average impact energy of 47J of all-weld metal.

System B - based on the tensile strength and the average impact energy of 27J of all-weld metal.

In most cases, a given commercial product can be classified to both systems. Then either or both classificationdesignations can be used for the product.

The symbolisation for mechanical properties is summarised in Table 1A for classification system A and Table 1Bfor classification system B. For classification system B, the 'X' can be either 'A' or 'P', where 'A' indicates testing inthe as-welded condition and 'P' indicates testing in the post weld heat-treated condition. The symbol forchemical composition is summarised in Table 3A and 3B of BS EN ISO 14341 based on each classification system.For classification system A, the standard lists eleven compositions, too many to describe completely here. Six ofthe wires are carbon steel with varying amounts of deoxidants, two wires contain approximately 1% or 2.5%nickel and an additional two wires contain around 0.5% molybdenum. The designation of these wires is forexample G3Si1, 'G' identifying it as a solid wire, '3' as containing some 1.5% manganese and Si1 as containingaround 0.8% silicon; G3Ni1 is a wire with approximately 1.5% manganese and 1% nickel.

Table 1A Symbols for mechanical properties based on classification system A

SymbolMin Yield Strength

N/mm2

UTS

N/mm 2

Min Elongation%

Symbol Charpy-V Test 47 J at Temp C

35 355 440 to 570 22 Z No requirements

38 380 470 to 600 20 A +20

42 420 500 to 640 20 0 0

46 460 530 to 680 20 2 -20

50 500 560 to 720 18 3 -30

4 -40

5 -50

6 -60

7 -70

8 -80

9 -90

10 -100

Table 1B Symbols for mechanical properties based on classification system B

SymbolMin Yield Strength

UTSMin Elongation

Symbol Charpy-V Test 27 J at Temp C

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N/mm2 N/mm 2 %

43X 330 430 to 600 20 Z No requirements

49X 390 490 to 670 18 Y +20

55x 460 550 to 740 17 0 0

57x 490 570 to 770 17 2 -20

3 -30

4 -40

5 -50

6 -60

7 -70

8 -80

9 -90

10 -100

A full designation could therefore be ISO 14341-A-G 46 5 M G3Si1 where the '-A' designates the classificationsystem A, the '-G' designates solid wire electrode/or deposits, and the 'M' designates a mixed gas. An exampleof a System B designation could be ISO 14341-B-G 49A 6 M G3, where 'A' indicates testing in the as-weldedcondition.

The AWS specification AWS A5.18 covers both solid, composite stranded and cored wires comprising six carbonsteel filler metals for MAG, TIG and plasma welding in both US and metric units.

The classification commences with the letters 'E' or 'ER'. 'E' designates an electrode. 'ER' indicates that the fillermetal may be used either as an electrode or a rod. The next two digits designates the tensile strength in either

1000s of psi.(ksi) or N/mm2 eg ER70 (70ksi UTS) or ER48 (480N/mm2 UTS). However, note that there is only onestrength level in the specification.

The next two characters identify the composition, essentially small variations in carbon, manganese and siliconcontents, the wire type (solid wire (S) or metal cored or composite wire (C)) and the Charpy-V impact values.

With one exception, the solid wires are tested using 100% CO2, the cored wires with argon/CO2 or as agreed

between customer and supplier, in which case there is a final letter 'C' designating CO2 or 'M', a mixed gas.

The permutations in these identifiers are too many and too complicated to be able to describe them all insufficient detail but as an illustration, a typical designation would be ER70S-3, a 70ksi filler metal, CO2 gas

shielded and with minimum Charpy-V energy of 27J at -20C. E70C-3M identifies the wire as a solid wire 70ksiUTS metal cored filler metal, 27J at -20C and tested with an argon/CO2 shielding gas.

The EN/ISO specification for non-alloy steel flux and metal cored wires is BS EN ISO 17632. This covers gasshielded as well as self-shielded wires. The standard identifies electrode based on two systems in a similar wayas BS EN ISO 14341, indicating the tensile properties and the impact properties of the all-weld metal obtainedwith a given electrode. Although the specification claims that the wires are all non-alloy, they can containmolybdenum up to 0.6% and/or nickel up to 3.85%. The classification commences with the letter 'T', identifyingthe consumable as a cored wire.

The classification uses the same symbols for mechanical properties as shown in Table 1A&B and a somewhatsimilar method to describe the composition as BS EN ISO 14341. Thus MnMo contains approximately 1.7%manganese and 0.5% molybdenum; 1.5Ni contains 1% manganese and 1.5% nickel. In addition to the symbolsfor properties and composition, there are symbols for electrode core composition. Table 2 summarises thesymbols for electrode core type and welding position in accordance with classification system A. Classificationsystem B uses Usability Indicators as oppose to a one-letter symbol for electrode core type, which can be foundin Table 5B of BS EN ISO 17632.

Table 2 Symbols for electrode core type and position based on classification system A

Flux Core Welding Position

Symbol Flux Core Type Shielding Gas Symbol Welding position

R Rutile, slow freezing slag Required 1 All

P Rutile, fast freezing slag Required 2 All except V-down

B Basic Required 3 Flat butt, flat and HV fillet

M Metal powder Required 4 Flat butt and fillet

V Rutile or basic/fluoride Not required 5 V-down and (3)

W Basic/fluoride, slow freezing slag Not required

Y Basic/fluoride, fast freezing slag Not required

Z Other types

In addition, there are symbols for gas type. These are 'M' for mixed gases, 'C' for 100% CO2 and 'N' for self-

shielded wires and 'H' for hydrogen controlled wires. A full designation may therefore be ISO 17632-A -T46 3 1NiB M 1 H5 in accordance with classification system A. For classification system B, an example may be ISO 17632-B-T55 4 T5-1MA-N2-UH5, where 'T5' is the usability designator, 'A' indicates test in the as-welded condition, 'N2' isthe chemical composition symbol, and 'U' is an optional designator.

The American Welding Society classification scheme for carbon steel flux cored wires is detailed in thespecification AWS A5.36. This also contains information from A5.18, but does not officially supercede it. The fulldesignation is ten characters in length beginning 'E' for an electrode then designators for strength, weldingposition, cored wire, usability, shielding gas, toughness, heat input limits and diffusible hydrogen, the last fourdesignators being optional.

There are two strength levels - E7 (70ksi UTS) and E6 (60ksi UTS) followed by a designator for weldingposition,'0' for flat and horizontal and '1' for all positions, including vertical-up and vertical-down.

The next symbol 'T' identifies the wire as being flux cored and this is followed by either a number between 1 and14 or the letter 'G' that identifies the usability. This number refers to the recommended polarity, requirementsfor external shielding, and whether the wire can be used to deposit single or multi-pass welds. 'G' means thatthe operating characteristics are not specified. The sixth letter identifies the shielding gas used for theclassification, 'C' being 100% CO2, 'M' for argon/CO2, no letter indicating a self-shielded wire.

The non-compulsory part of the designation may include the letter 'J', confirming that the all-weld metal test cangive Charpy-V values of 27J at -40C; the next designator may be either 'D' or 'Q'. These indicate that the weldmetal will achieve supplementary mechanical properties at various heat inputs and cooling rates. The final twodesignators identify the hydrogen potential of the wire.

A full AWS A5.36 designation could therefore be E71T-2M-JQH5. This identifies the wire as a cored, all positionalwire to be used with argon/CO2 shielding gas on electrode positive polarity. The weld metal should achieve

70ksi tensile strength, 27J at -40C, 58 to 80ksi yield strength at high heat input, a maximum 90ksi at low heatinput, and a diffusible hydrogen content of less than 5ml of H2/100g of deposited weld metal.



This article was written by Gene Mathers, reviewed and modified by Runlin Zhou.

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welding consumables - part 5 - job knowledge 86

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