PRIOR ART: It is widely known, that the GMAW (gas metal arc welding - MIG-MAG), GTAW (gas tungsten arc welding - TIG) and FCAW (flux cored arc welding, DUALSHIELD) welding processes require the addition of either inert or active gases during the welding, to form the shielding gaseous atmosphere at the melt pool.

It is also known that the welding wires are of ferritic steel, austenitic steel, nickel alloys or cupper al- loys.

The ferritic steel welding wires are coated with copper in order to facilitate the electric contact, improve the traction of the wire and avoid the corrosion problem.

These welding wires are usually manufactured in accordance with international rules and codes such as ASME/AWS/EN/DIN, etc., for the purpose of classifying and homologating the welding wires in accordance with, for instance, chemical anal- ysis, mechanical properties, etc.

In this way, the industry acquires welding wires

from a given manufacturer within the specification which the industry needs for carrying out its work or manufacturing its products.

It is important to point out that the makers of welding wires, by their own system of quality guarantee, evi- dently manufactures the welding wire within the guidelines of the international codes, thus ensuring its chemical analysis, as well as the mechanical properties of the weld material de- posited.

The copper coating is used only on ferritic materi- als, and does not have any mechanical, metallurgical or chemi- cal influence on the weld.

Besides, at present, for the classic high- productivity welding processes there are several shielding gases which are used during the welding operation, precisely to avoid the presence of air, which contains oxygen (02) in the percentage of from 18 to 21%, which would lead to a rapid oxidation of the metallic elements during the welding opera- tion, thus causing unacceptable porosity defect in the weld bead.

For this reason, in the welding of nickel and aluminium alloys, for example, which have a great affinity for oxygen, an inert gas, namely Argon, is compulsorily used, pre- cisely to avoid oxidation of these materials. Hence the clas- sic name of MIG Process (Metal Inert Gas). In the welding of ferritic steels in general, or even stainless steels, mixtures containing active gases are used; hence the name MAG Process (Metal Ative Gas). It is usually employed in welding ferritic steels in general. Today, usually in all industrial countries there are standardized active gaseous mixtures, which are sold by gas industries, such as: Argon + Oxygen, Argon + Carbon Dioxide, Argon + Oxygen + Carbon Dioxide, and so on.

SHORTCOMINGS OF THE PRIOR ART: It is clear that the semiautomatic, mechanized and robotized welding processes, under inert or active shielding gas, need systems for storing industrial gases such as tanks or cylinders which, besides taking physical space, oblige the

companies to pay rent and maintenance fees, as well as to buy the shielding gas. In addition, it becomes necessary to use gas distribution systems such as networks, feeding lines, instrumentation lines, etc.

All these factors raise substantially the final cost of the welding processes.

OBJECTIVES OF THE INVENTION The objective of the invention is to simplify the electric arc welding processes and to reduce the direct welding costs.

This objective is achieved by using either a massive or tubular self-shielded welding wire, the coating layer or inner flux of which, upon burning, generates its own melt pool shielding atmosphere d, thêfê6fe, it does not require the addition of either inert or active shielding gas in the welding region. The welding wires are of ferritic steel, austenitic steel, nickel alloys or cupper alloys.

The invention also relates to a welding process, which uses the above-mentioned welding wire and which can be carried out in the presence of ambient air, compressed air or sucked air.

In a first embodiment, the welding wire of the in- vention is massive and is designed for being used in the GMAW (gas metal arc welding or MIG-MAG) and SAW (submerse arc welding) welding processes. The massive wire may also be cut into pieces and be used as either a welding electrode in the SMAW (shield metal arc welding) welding process or as a welding rod in the GTAW (gas tungsten arc welding or TIG) process.

In a second embodiment, the wire welding of the in- vention is tubular, with inner flux, and is designed for being used in the FCAW (flux arc welding or inner shield-dualshiel) welding process.

In a third embodiment, the welding wire of the in- vention is tubular, does not present inner flux and can be used in the same welding processes for which the massive welding wire is employed.

It should be again noted that the welding processes GMAW and FCAW that usually require the addition of shielding

gases, by using the weldind wire according the invention no longer require the addition of the said shielding gases.

Thus, the welding wire of the invention is coated with at least one layer of zinc or a zinc-containing alloy; or with at least one layer of tin or a tion-containing alloy; or with at least one layer of aluminium or an aluminium- containing alloy. Conveniently the welding wire may also pres- ent at least one layer of copper. In this case, the layers of copper and the other coating material of the wire are alter- nate.

The welding wire of the invention may be either mas- sive or tubular. In the case of the tubular wire, the coating layer is arranged in the inner and/or outer surface of the wire. This tubular wire may be either without inner flux or with inner flux.

The welding wire according to the invention may also be tubular and not present a coating layer, but rather an in- ner flux containing the material which, upon burning, gener- ates the shielding atmosphere. In this case, the inner flux is completely of zinc or has at least a portion of zinc or of a zinc-containing alloy. The inner flux may also be completely of tin or have at least a portion of tin or of a tin- containing alloy.

The inner flux may further be completely of aluminium or have at least a portion of aluminium or of an alluminium-containing alloy.

As already mentioned, the massive welding wire or the tubular wire without inner flux, according to the in- vention, are suitable for the GMAW (gas metal acr welding - MIG-MAG), GTAW (gas tungsten arc welding- TIG), SMAW, and SAW welding processes, wherein for the GMAW and GTAW processes it is not necessary to add any inert or active protection gas.

The tubular welding wire with inner flux according to the invention is suitable for the FCAW (flux cored arc welding - innershield-dualshield) welding processes. For the dualshield process it is not necessary to add any inert or ac- tive protection gas.

The electric arc welding process of the invention, in which the melt pool and the transferred drop are protected

by a gaseous atmosphere, uses the either massive or tubular welding wire cited previously and wherein the burning of zinc, tin or aluminium generates the gases which form the protecting gaseous atmosphere. Additionally, in the welding process ac- cording to the invention, one may apply compressed air or forced air in the region of the electric arc.

Besides, in the process of the invention one may also suck the ambient air and the welding fumes from the re- gion of the electric arc.

ADVANTAGES OF THE INVENTION Thus, the welding wire of the invention is self- shielded, that is to say, it generates its own protecting gaseous atmosphere during the welding, and it is no longer necessary to add any inert or active shielding gas.

The wire may be used directly in the presence of air, be it ambient air, compressed air or sucked air; even with the presence of air in the melt pool and in the region of addition-metal (drops) transfer, no oxidation of the element iron (Fe) occurs, which would cause porosity defect in the weld bead.

The welding wire of the invention may have any diam- eter and may be used for welding various metals, such as ferritic materials in general, stainless steels, alloys of nickel, copper, etc.

As mentioned previously, the welding process of the invention can employ compressed air in the welding region, by using the same conduits which were used before by the active gas or by the inert gas, which provides the following advan- tages: a) greater cooling of the welding torch (contact tip), which implies longer useful life thereof; b) greater stability of the electric arc, which pro- vides a considerable increase in the final quality of the welding; c) increase in the filler metal deposition rate, which provides a considerable increase in productivity.

The welding process according to the invention can also employ air suction in the welding region, which, besides providing the above-cited advantages (a), (b), and (c), will

also provide suction of the fumes from the welding region, thus rendering the air clean and protecting the health of the operator.

It should be pointed out that the companies which manufacture special products and wish to maintain the shield- ing gas together with the self-shielded wire can do so without problems. In this case, the flow of the protection gas can be reduced by over 50%.

However, for the case of most conventional, struc- tural welds, the use of a shielding gas can be completely eliminated, since the process will then function just as the shielding metal arc welding process (SMAW), with a coated electrode, in which, as it is well known, the gaseous shield- ing is supplied by the burning of the electrode coating, mainly of the cellulosic material.

It should be noted that the self-shielded welding wire according to the invention, functions in a way similar to that of the classic shielding metal arc welding process (SMAW), with a coated electrode. For this technical reason, it is perfectly employable in the welding operations of high- productivity welding processes.

It should be stressed once again that the massive self-protected welding wire is exactely the same wire produced by the maker of welding wires, meeting all the technical re- quirements of manufacture already homologated and qualified, following the requirements of the international codes, but with a new factor, which is the coating or treatment of the surface with zinc (Zn), tin (Sn), or Aluminium (Al) instead of the classic copper (Cu) coating, which is usually employed in the solid ferritic wires.

The coating of the welding wire with zinc, tin or aluminium is what provides the new technical fact, since the elements has a lower reduction potential than certain ele- ments, principally iron (Fe), leaving this element free from oxides and, consequently, the weld bead free from pores. For this reason the self-shielded wire according to the invention may be applied under ambient air.

In addition, in the case of the zinc, for example, the melting temperature of zinc (Zn) is of 4200 C, which is

quite low as compared with that of steel, which is of about 16000 C. In this way, even at the beginning of the weld bead, the required protection is guaranteed, not only for the melt pool, but also in the addition-metal transfer region (drops).

The layer of zinc, tin or aluminium or coating thickness can be equal or thicker than the copper layer which is normally used in the technique of treating ferritic welding wires with copper.

It is important to stress that the technique of coating the wire, be it hot or not, is perfectly mastered by the makers of wires, also providing excellent storing proper- ties of the wound welding wire, mainly when it is wound on me- <BR> <BR> tallie steels, As it is fizz known at present, the wires treated with copper and wôiind d spools exhibit a rapid oxidation at the surface, when the roll remains exposed to long periods of work.

Another important fact is that with the welding wire according to the invention, the spatters, which usually occur during the welding, adhere quite less to the surface of the base metal as compared with the classic copper-treated welding wire, either reducing or eliminating the use of antispatters agents, which are technically regarded as contaminants and are expensive.

When it comes to tubular wires, the coating opera- tion can be carried out on the metal strip itself which origi- nates the tubular wire, or else after shaping the strip itself.

It should also be pointed out that the welding proc- ess of the invention can use already-zincified smooth ferritic wires, which are usually employed in fences for marking off land. These wires, provided that they are duly wound, can be employed directly in the welding machines, mainly in simple, structural welding and without project responsibility.

Besides the embodiments presented above, the same inventive concept can be applied to other alternatives or pos- sibilities of utilization of the invention. Thus, it will be understood that the present invention should be interpreted in a broad manner, its scope being determined by the terms of the claims.