EN 439 STANDARD: WELDING CONSUMABLES – SHIELDING GASES FOR ARC WELDING AND CUTTING

Objective

The objective of the following standard is to classify shield gases from their chemical properties and as a basis to approve of the binary “addition materials – gases or moistures for shielding”. The purity of the gases and the moistures tolerances are also specified.

Table 1 – Physical and chemical properties of base gases

Supply forms Gases are supplied in liquid or gas form, for simple gases or moistures. When the moistures are mixed on the field, from their components, the moisture system should be designed and kept to maintain the gases purity and tolerances specified as referred before. High pressure containers (bottle): Except on carbon dioxide, all the gases and moisture, shown on table 2, are found in gas state, supplied in high pressure containers (bottle). Designation Gases for protection are called shield gases in the present standard, using the symbols referred as the group and the number of identification, shown on table 2.

Field of applications Applicable on arc welding and cutting processes, where the utilize gases or gas moistures. Appropriate but not limited only on the following processes: gas tungsten arc welding, gas metal arc welding, plasma welding, plasma cutting and root gaseous protection.

Gas Chemical Symbol

Specified for 0ºC and 1,013 bar (0,101 MPa)

Behaviour during welding operations

Density (air=1,293) Kg/m3 Relative density Boiling point

at 1,013 bar (ºC)

Argon Ar 1,784 1,380 -185,9 Inert Helium He 0,178 0,138 -268,9 Inert

Carbon dioxide CO2 1,977 1,529 -78,5 1) Oxidizing Oxigen O2 1,429 1,105 -183,0 Oxidizing

Nitrogen N2 1,251 0,968 -195,8 Nonreactive 2) Hydrogen H2 0,90 0,070 -252,8 reducing

1) sublimation temperature 2) The behavior of nitrogen varies with the material, in some cases, can be harmful

Shield gases classification In table 2 the gases and the moistures are classified in groups according to their chemical reaction and composition. The symbols utilized in the group classification are: R (reducing gas moistures), I (inert gases and moistures), M (oxidizing moistures with oxygen, carbon dioxide or both), C (highly oxidizing gases and moistures), F (nonreactive gases or reducing moistures). Some components are not listed on table 2, when these components are added on one of the listed components, the result is called as a special gas moisture and the prefix S is added for the original designation.

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Table 2 – Shield gases classification for arc welding and cutting Symbol1) Volume of percentage of the constituent

Applications Observations Group Identification number

oxidizing inert reducing nonreative

CO2 O2 Ar He H2 N2

R 1 2

reamain2) reamain2) >0 to 15

>0 to 35

GTAW,

Plasma, root protection

reducing

I 1 2 3

100

reamain

100

>0 to 95

GTAW, GMAW,

Plasma, root protection

inert

M1

1 2 3 4

>0 to 5 >0 to 5

>0 to 5

>0 to 3 >0 to 3

reamain2) reamain2) reamain2) reamain2)

>0 to 5

GMAW

mildly oxidizing

Sharply oxidizing

M2

1 2 3 4

>5 to 25

>0 to 5 >5 to 25

>3 to 10 >3 to 10 >3 to 10

reamain2) reamain 2) reamain 2) reamain 2)

M3 1 2 3

>25 to 50

>5 to 50

>10 to 15 >8 to 15

reamain 2) reamain 2) reamain 2)

C 1 2

100 reamain

>0 to 30

F 1 2

>0 to 50 100

reamain

Plasma cutting,

protecção de raíz

nonreactor reducing

1) When the components are not listed on a specified classification on this table, the result is called as an special gas moisture and the prefix S is added for the original designation. Section 4 shows the details relative to the suffix S. 2) Argon can be replaced with by Helium at 95 %. The content of helium is call for an additional number of identification, show on table 3 according to section 4.

Identification number Percentage of Helium in volume (1) >0 to 33 (2) >33 to 66 (3) >66 to 95

Table 3 – Identification number for R and M groups with Helium

Moistures and Tolerances For components at concentrations of 5%, in volume, the allowed margin is kept within ± 0.5% (in absolute value). For concentrations within 5% to 50%, in volume, the margin is kept within ± 10% of the specified value (relative value). Purities and dew point The minimum purity and the maximum dew point of the supplied gases, in bottles or tanks, can be found on table 4, for each of the classification listed on table 2. The purities and dew points of the special moistures should correspond to the utilized gas or moisture, according on table 4. For welding of some material, e.g. titanium and tantalum, where the utilization of high purity gases is needed, and in these cases, the specifications can be accorded with the supplier. The supply system of the gases to the user should be designed to maintain the purity of the products until further usage.

Table 4 – Purity and dew point of gases and moistures Group1) Minimum purity

involume % Dew point at

1,013 bar (max ºC) Humidity max. ppm

R 99,95 -50 40 I 99,99 -50 40

M1 99,70 -50 40 M2 99,70 -44 80 M3 99,70 -40 120 C 99,70 -35 200 F 99,50 -50 40

Oxigen 99,50 -35 200 Hydrogen 99,50 -50 40

1) Values for oxygen and hydrogen are also included in this table.

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