EN 439-1994 pdf download.Welding consumables – Shielding gases for arc welding and cutting.
This EN 439 is applicable to gas shielded arc welding and cutting processes with gases and gas mixtures defined within. Applications indude, but are not limited to:
– tungsten inert gas (TIG) welding;
– metal active gas (MAG) welding;
– metal inert gas (MIG) welding;
— plasma arc welding;
– plasma arc cutting;
— back shielding.
The purpose of this standard is to classify shielding gases in accordance to their chemical properties as a base for the approval of shielding gas and filler wire combinations.
Gas purities and mixing tolerances are also specified.
Properties of gases
The physical and chemical properties are listed in table 1.
Classification of shielding gases
Table 2 classifies into groups the vailous component/composition combinations of shielding gases according to their reaction behaviour.
The symbols used for dassitication groups are:
– R: reducing gas mixtures;
– I: inert oases and inert mixtures;
– M: oxidizing mixtures containing oxygen,
carbon dioxide or both;
-C.highly oxidizing gas and highly oxidizing
– F: un,eactive gas or reducing gas mixtures.
Where components not listed in table 2 are added to one of these classifications it is designated as a special gas mixture and carries the prefix S. Details of the S designation are given in clause 4.
Designation
Shielding gases shall be designated by the term “shielding gases”, the number of this standard, group and identification number according to table 2.
EXAMPLE 1: A gasmixture containing 30 % helium, and balance argon is designated:
Shielding gas EN 439 – 13
EXAMPLE 2: A gasmixture containing 10 % carbon dioxide, 3 % oxygen and balance argon is designated:
Shielding gas EN 439 – M2.4’
If argon is partly replaced by helium, the helium content is designated by an additional identification number, see table 3. This identification number is added in brackets as a suffix.
EXAMPLE 3: A gasmixture M21 containing 25 % helium is designated: Shielding gas EN 439 – M21(1)
Special gases shall be designated by the prefix S followed by the base gas or mixture symbol as in table 2, followed by the percent concentration by volume and chemical formula of the additional gases.
S (designation) + % chemical symbol
EXAMPLE 4: A special gas mixture containing 10 % carbon dioxide, 3 % oxygen and balance argon, designation M24, but also containing 2,5 % neon is designated:
Shielding gas EN 439 – S M24 + 2,5Ne
Tolerances of mixtures
For component concentrations up to 5 % by volume the permissible deviation shall not exceed +. 0,5 % by volume from the specified value. For component concentrations of between 5 % by volume and 50 % by volume the concentration shall not vary by more than +. 10 % of the specified value.
For some materials, e.g. titanium and tantalum, gases of higher purities may be required and specifications can be agreed between the user and the supplier. The users gas supply system should be designed and maintained such that the purity as delivered is maintained up to the point of use.
7 Forms of supply
Shielding gases are supplied in the gaseous or liquid state either as single gas or gasmixture.
Where gas mixtures are prepared on site from individual gases, the mixing system shall be designed and maintained such that the tolerance and the purity specified in clauses 5 and 6 can be achieved and maintained.
7.1 Gas cylinders
With the exception of carbon dioxide, all the gases and gas mixtures listed in table 2 are fully in the gaseous state when supplied in gas cylinders.
The gas cylinders for the gases listed in table 2 are filled to a stated volume and pressure as indicated by the supplier. The actual pressure will vary with the ambient temperature, e.g. the pressure of argon (II) will vary as in figure 1.
Suitable regulators shall be fitted to the gas cylinder before use.
72 Liquid Liqu.EN 439-1994 pdf download.