Protective gas for tig welding

Details Protective gas for tig welding Protective gas for tig welding

2000-05-01

2001-05-29

Ryan, Patrick (Department: 1725)

Metal fusion bonding

Process

With protecting of work or filler or applying flux

C219S075000

Reexamination Certificate

active

06237836

ABSTRACT:

The invention relates to an inert gas for TIG welding of metals, the thermal conductivity of which is below that of aluminium, in particular high-alloy or low-alloy steels, with argon as the principal component of the gas.
It is known from publications that TIG welding of metals with a thermal conductivity below that of aluminium, in particular high-alloy or low-alloy steels, is carried out with argon as the inert gas. To improve the welding efficiency, other gases, in particular 2-10% of hydrogen, have frequently been added to the argon. Nevertheless, the welding results using such inert gases vary depending on the material composition and the welding filler material.
The following problems are encountered during TIG welding using the known inert gases:
insufficient arc stability
welding speed too low
oxidation of the seam surface
flow performance only moderate
weld appearance (uneven weld ripples)
poor suitability for out-of-position welding
poor gap bridging ability.
The invention is based on the object of providing an inert gas which makes it possible to improve efficiency of TIG welding while maintaining suitability for out-of-position welding.
This object is achieved by means of the features of claim
1
.
The features of claim
1
advantageously result in an improved arc stability, an increase in the welding speed, reduced oxidation of the seam surface, an improved flow performance and uniform weld ripples.
In this context, the principal gas component in a gas mixture is understood to mean a gas component which forms at least 90% by volume in the gas mixture. The inert gas mixture generally contains at least 90% by volume argon as principal gas component, preferably at least 95% by volume argon.
It has been found that, with a view to good suitability for out-of-position welding, a high welding speed, low oxidation of the seam surface and reliable penetration, particularly advantageous results are achieved if the inert gas contains from 0.15 to 1.5% by volume hydrogen, preferably 0.25 to 1.2% by volume hydrogen, and particularly preferably 0.35 to 0.9% by volume hydrogen, from 0.5 to 9% by volume helium, preferably from 0.8 to 5% by volume helium, and particularly preferably 1.2 to 3.5% by volume helium, remainder argon, i.e. the total of the hydrogen, helium and argon contents amount to 100% by volume of the overall gas mixture. Furthermore, it has proven particularly advantageous to use a ratio of the volumetric fractions (expressed in per cent by volume) of hydrogen to helium in the range from 1:2 to 1:8, in particular in the range from 1:3 to 1:5. Outside these ratio ranges, either the oxidation behaviour or the suitability for out-of-position welding or both deteriorate(s) significantly.


REFERENCES:
patent: 3582604 (1971-06-01), Konjushenny et al.
patent: 5210388 (1993-05-01), Farwer
patent: 5210389 (1993-05-01), Farwer
patent: 5296676 (1994-03-01), Gilman
patent: 5347098 (1994-09-01), Murakami et al.
patent: 5667703 (1997-09-01), Soula et al.
patent: 5686002 (1997-11-01), Flood et al.
patent: 5714729 (1998-02-01), Yamada et al.

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