FI64903C - FOERFARANDE FOER GENOMFOERANDE AV BAOGSVETSNING. TRANSFERRED PAEIVAEMAEAERAE-FOERSKJUTET DATUM PL 14 ç 28.06.78. - Google Patents

Description

M fl1, * CUULUTU $ PUBLICATION / i λλ ^ ftijB LBJ ('UTLÄGGNI NGSSKMFT 6 4 903 -¾¾ (45) ^ *' (51) Kv.lk.3 / lnc.CI.3 B 23 K 9/18 ENGLISH— -FINLAND (21) Pttunttlhukumu · - Ptt «ntara6knl» g 780202 (22) Haktmlspilvt - An * 6knlng «iag 30.01.78 (23) AlkupUvi — Giltlghuttdag 28.06.78 (41) Tullut | ulklMkil - Bllvit offaotllg 29 * tantti- ja rekittaHhallitut (44) Nihttrtkslptnon f »kuutjulkibun pvm. - ηη« _

Patent- och registerstyrelgen AmOka / i utlagd och utl. * Krtft * n publkurwl 31.10.03 (32) (33) (31) Requested «uollt * u · —togtrd prloritut (71) Markku Kauppi, 5 ^ + 710 Lemi, Juhani Niinivaara, 5 ^ 710 Lemi,

Markku Nurminen's estate, 5 ^ 710 Lemi, Seppo Karppanen, 5 ^ 750 Välijoki, Finland-Finland (FI) (72) Markku Kauppi, Lemi, Juhani Niinivaara, Lemi, Markku Nurminen,

The present invention relates to a method for performing arc welding according to claim 1 and to an apparatus for carrying out the method. The present invention relates to a method according to claim 1 for performing arc welding and to an apparatus for carrying out the method.

Companies performing welding work and manufacturing welding equipment and materials have sought to obtain and / or sell arc welding methods and equipment that would allow welding to be performed regardless of external conditions. After all, it is well known that arc welding - especially in good external conditions, such an easy-to-use shielding gas arc welding - does not succeed in windy, draft, rainy and / or humid conditions, let alone underwater welding conditions.

Underwater welding has been the subject of growing interest and development in recent years. Repairs to drilling rigs, underwater gas and oil pipelines, ships and port facilities are the areas where underwater welding has been used the most. The structures that can be hit are usually such that it is impossible or very expensive to raise them to the surface. The goal in underwater welding is to achieve a high quality weld.

The known methods for performing underwater welding are divided into two main groups based on the welding environment: wet methods and dry methods. Known wet methods in rod welding mainly use ordinary welding rods coated with waterproof vinyl paint or paraffin to prevent wetting, in gas arc welding, in addition to conventional means, a welder in which a conical water jet from the outer circumference of the nozzle keeps the water away from the arc. The water jet has been used with relatively good results in the CC 2 wet process. In wet methods, as the name suggests, water can enter the arcuate area without hindrance. Dry methods prevent water from entering the arc region by covering the arc region with a substantially closed (the groove to be welded is, of course, free) or opaque or transparent welding shield open from below. The welder is brought from below into open welding shields, usually from below, and into completely closed small welding shields through the wall. If the welding shield is large enough, the welder can work inside the shield. Welding shields have either a shielding gas or air atmosphere.

In underwater welding, welds of almost the same quality are obtained by dry methods at least at shallow depths than in air, in the case of welding outside the water. However, the disadvantages of dry methods are the time-consuming installation and relocation of welding shields and the inconvenience and inflexibility of welding work due to the use of shields. In addition, there are many places where welding shields cannot be used.

The wet welding to which this invention relates is a fairly flexible and economical method for performing underwater welding.

It can be performed with the same 3 64903 equipment as surface welding, except for diving equipment. However, in the quality of the weld, wet methods have not achieved nearly the same results as dry methods. There are three weldability problems in the wet process, all due to the surrounding water. They are the high cooling rate, the high hydrogen content, and the ambient pressure that affect the reactions in the arc and the transfer of matter, as well as the reactions between melt and slag, especially at greater depths.

In wet processes, the worst problem is the presence of hydrogen cracks. This is precisely due to the high hydrogen content entering the weld. The high cooling rate further complicates the diffusion of hydrogen from the weld joint and preheating or post-heating is hardly possible to remove hydrogen, reduce stresses or avoid brittle microstructure. As a result of the high cooling rate, structural steels often form a brittle-prone microstructure with high internal stresses.

Another major problem in wet processes is the poor impact toughness of the welded joint. The ambient pressure, especially at greater depths, changes the conditions of the slag reactions and rapid cooling does not provide kinetic conditions for adequate weld material cleaning.

Especially in the case of wet welding with a rod method, the avoidance of welding defects, such as pores, slag inclusions, slag line, joint or root defect, requires special skills under severe conditions.

The object of the method according to the present invention is to obviate the drawbacks of wet welding methods to date and to provide an arc welding method and apparatus which is suitable for arc welding in water or another liquid and air. The features of the invention are set out in the claims.

► £ i · '·' 4 64903

The arc conductor and / or the electrically conductive liquid, liquid mixture, solution, etc. forming the arc are intended to facilitate controlled arc combustion, increase the weld pool, slow the cooling of the weld, and limit direct presence of water in the arc region and contact with the weld pool.

Thanks to the invention, an electrically conductive substance in the arc region facilitates the ignition and combustion of the arc in water. When it burns into the arc area, it forms a shielding gas zone to prevent water from entering the arc and melt. Such a shielding gas zone is created especially when organic substances are used. Furthermore, the substance forms a slag layer which protects the melt from the action of water when the substance is so large that it does not have time to burn in the arc of light. The additional slag layer formed by the substance slows down the cooling of the weld, whereby the separation of gases from the weld is improved. Slowed cooling makes it easier to make the weld shape valid. The substance affects melting rate and penetration. The melting rate and penetration are improved, especially when organic substances are used which, when burned in an arc, generate considerable amounts of thermal energy.

The reasons for the excellent results obtained in the welding tests with the method according to the invention are not fully known. In addition to the protective effect of the second coolant retarder additive, side electric currents may be generated due to the additive used between the entire article to be welded and the rod, heating the water in the vicinity and any seam and slag layers. In this case, the weld stays hot for even longer, whereby the hydrogen that embrittles the weld is removed and the weld becomes even stronger.

When using the method according to the invention for underwater welding, the method can be considered as a wet method, because water with possible additives enters the arc area almost without hindrance. The method is suitable for use in all arc and gas arc welding methods, such as stick welding, MIG, MAG, TIG, arcatomic, plasma welding. Performance means and equipment vary depending on the welding method.

The description below has focused mainly on underwater welding, as the problems associated with arc welding in water are currently the greatest. However, the method also makes it possible to perform arc welding in other external conditions, e.g. in connection with arc welding in air. In this case, the electrically conductive substance and / or the substance which forms an electrically conductive liquid, liquid mixture, solution, etc. with water prevents, in addition to water, the harmful effect of air on the weld. When using the method in the case of arc welding in air, the formation of flue gases is stronger than in the case of underwater welding. Mention should be made here of an embodiment of the invention in which a conventional shielding gas has been replaced by a paste which protects both the arc and the weld. The paste is ideal for use in both water and air arc welding, protecting both the arc and the weld.

A method according to the invention, an apparatus and a welding rod for carrying out the method are described in detail below with reference to the accompanying drawings, in which Figure 1 shows an embodiment of the method according to the invention, Figure 2 shows another embodiment of the method according to the invention, Figure 3 shows a third embodiment of the method according to the invention, and Figure 4 shows a fourth embodiment of the method according to the invention and a welding rod for carrying out the method.

In Fig. 1, an arc 1 is formed between the welding rod 9 and the base material 13. At the same time, the welding rod 9 melts and forms a weld seam 10, which melts onto the base material 13. As the weld 10 is formed from the coating of the welding rod 9, a slag layer 11 is formed on the weld.

6 64903

According to the invention, an electrically conductive substance 2 or a substance 3 forming an electrically conductive liquid, liquid mixture, solution or the like with water is introduced into the arcuate region 1 via a pipe 12.

In the embodiment shown in Fig. 2, a substance 2, 3 is introduced into the area of the arc 1 from the annular nozzle 4 surrounding the arc and the welding rod 9, which makes the electric current conductive in the area of the arc. This embodiment of the invention is similar to shielding gas arc welding (MIG, MAG, TIG). The difference is that the shielding gas is replaced by a substance 2, 3, which can advantageously be e.g. a paste. The ring nozzle can, of course, extend as far as the additive wire. It is, of course, possible to use shielding gas as a supplement.

Figure 3 shows an embodiment of the invention in which the arc 1 formed between the welding rod 9 and the base material 13 is partially protected by a synchronous mass 3. A substance which makes the arc region electrically conductive detaches from the mass 3 and dissolves in the arc region; welding takes place under water as the water surrounds the welding object. As the welding progresses, the mass 3 is conveyed after the arc when the weld is formed so that the arc returns to the cavity formed in the mass piece 7. The protective layer 8 also releases a protective layer 8 on the weld 10. The protective layer 8 prevents the weld from cooling and prevents water from coming into contact with the weld. Still remaining on the hot weld seam 10, the mass 3, when using organic matter, continues to burn even after the Arc, which is effective in preventing the weld from cooling too quickly.

Figure 4 shows a welding rod 9 for carrying out the method according to the invention. In this case, an ordinary, either coated or uncoated welding rod 9 is further coated with a substance 3 which detaches and / or dissolves in the arcuate region 1 a conductive conducting substance. The cavity 7 can, of course, also be closed by the mass on the open groove side, whereby the arc is in a substantially closed state.

7 64903

The following embodiments are intended to illustrate in particular the additives used in the process according to the invention.

Example 1.

In one study, a butt welding test was performed underwater at a depth of 3 m. The steel used was Fe-52 C (respectively Norske Veritas' shipbuilding steel NVW-36 or NVA-36). The welding rods used were painted with vinyl paint. Welding was performed by the method of Figure 3 using pine soap as a shielding agent. The water temperature was about 3 ° C. The pieces were subjected to impact tests according to SFS 3326 at a temperature of ± 0 ° C. The fracture energy for the weld metal was 37 J as the average of three experiments and 40 J at the melt limit, respectively. For the shipbuilding steel used, Norske Veritas requires an impact strength value of 34 J at 0 ° C. The result of any of the impact tests was below this limit.

The pine soap used as a preservative was solid, ca. about 80% by weight, of which about 75% by weight of fatty acids, oil and linoleic acid, sodium salts, and 25% by weight of sodium salts of resin acids such as pimaric, isopimaric and abietic acid. When the pine felt was removed from the top of the weld about 1 min after the welding took place, the weld seam continued to glow.

Example 2.

In one embodiment of the invention, the welding was performed in a normal atmosphere using MIG welding means. No shielding gas was used. A piece of pine soap as shown in Figure 3 was used to replace the shielding gas. The arc was stable and the resulting weld was excellent.

Example 3.

In one embodiment of the invention, the welding is carried out in a normal atmosphere 8 64903, whereby an aqueous solution forming an electrolyte is introduced into the arc region and / or in its immediate vicinity. The aqueous solution can be introduced into the arc region, e.g. by a nozzle 4 of the type shown in Fig. 2, which surrounds the arc region. In this case, the electrolyte is sprayed onto the welding target and the electrolyte forms a sheath around the target. This application is especially suitable in difficult external conditions, such as windy, rainy, and humid locations, where arc ignition is difficult and combustion is unstable. The method achieves rapid arc ignition as well as a stable arc.

Example 4.

The method can be used, for example, with electrolytes consisting of, for example, the following inorganic acids and salts of acids: inorganic mineral acids, halogenated hydrogens, sulfuric acid, sulfuric acid, nitric acid, nitric acid, silicic acid, etc. Particularly soluble salts, e.g. alkali metal salts, potassium, sodium and ammonium salts and alkaline earth metal salts, magnesium and calcium salts such as K, Na, Ca, Mg, and NH 4 carbonates.

Example 5.

Dissociable salts of organic carboxylic acids are particularly suitable for use in the process. These are, for example, carboxylic acids having a straight or branched carbon chain, e.g. 3 to 15 carbon atoms; saturated or unsaturated; substituted with an anomatic, carbocyclic or heterocyclic ring compound; mono- or polybasic; halogenated or non-halogenated; an amine derivative or, in general, any dissociable organic acid or a salt thereof. If it is desired to use semi-solids, solid substances which are partially soluble in water as an electrolyte and which form a solid protective mass for the resulting weld, it is preferable to use semisolids, saponifiable fatty acids such as oleic acid, linoleic acid, etc. The process can then be used. metal soaps, e.g. aluminum, calcium, magnesium, copper, zinc or lead stearate, laurate, resinate, naphthenate, oleate, etc. Of course, conventional potassium and sodium salts of said fatty acids, soaps are most suitable. and favor. In the experiments performed, good results have also been obtained with silicate compounds.

Example 6.

In one study, a welding test was performed underwater at a depth of 3 m. The steel used was high-strength fine-grained steel according to SFS 250. Acid-coated unalloyed welding rods ISO E 43 4AR24 (OK50.10) were used in the experiment. Welding was performed by the method of Figure 3 using pine soap as a shielding agent. Welded rods were subjected to tensile tests according to SFS 3173 and impact tests according to SFS 2853. Further, the welded joint was x-rayed. In addition to the welding carried out by the method according to the invention, a parallel comparative test was carried out, in which the corresponding welding was carried out without additive. The results of the experiment are shown in Tables 1-2: the seams welded without the additive were not valid in appearance, the seams had shape defects and hydrogen cracks; there were cracks in the seams due to internal stresses.

X-ray examinations showed that the seams had an X-ray class of 3 (rating 1-5, 1 worst and 5 best). Further, there was only porosity in the welded joints. A few small slag-closing grooves and pores invisible in the X-ray image were found in the surface fire just below the surface during the microstructural examination.

In the tensile test, the rods clearly broke on the base material side despite the softer additive than the base material (the tensile strength of pure weld metal 2 2 440-490 N / mm). The tensile strengths of 550 and 545 N / mm corresponded to the strength of the base material (Rf 490-620 N / mm).

The experiments showed that obtaining a weld of suitable shape and avoiding planar welding defects is clearly easier in the method according to the invention than in the conventional wet welding method without additional protection. Even a demanding welding joint can be welded flawlessly with the method according to the invention, because in the welded test there was no so-called

____ ___ Il II I. ------, 10 64903 planar welding defects. The method according to the invention makes it substantially easier to obtain a weld of suitable shape than in wet welding without an additive. The strength of the welded joint corresponded to the strength required of the base material. The impact toughness was adequate in water at the temperatures in question.

Table 1, tensile tests

Rod No. 1 2

Width mm 20.0 20.0

Thickness mm 16.1 16.1

Cross section mm ^ 322 322 2

Breaking strength N / mm 550 545

Fracture: base material B, weld W B B

Distance from melt limit mm 10 10

Table 2, impact tests

Rod ID Rod ID

SI 27 KV / 0 ° C H 7 40 KV / 0 ° C

S 2 31 KV / 0 ° C H 8 39 KV / 0 ° C

S3 36 KV / 0 ° C H 9 40 KV / 0 ° C

S 4 36 KV / -20 ° C H 10 32 KV / -20 ° C

S 5 26 KV / -20 ° C H 11 27 KV / -20 ° C

S 6 17 KV / -20 ° C H 12 26 KV / -20 ° C

The invention is not limited to the examples presented, but its applications may vary within the scope of the appended claims. In this case, e.g. the control members of the additive used in the welding of the device may consist, for example, of a ring nozzle or the like partially, preferably substantially completely surrounding the welding rod or wire, of one or more tubular or other nozzles or the like placed in the immediate vicinity of the rod or wire. Furthermore, the additive supply means may consist of, for example, a piston, centrifugal, diaphragm, etc. pump or a similar or other type of supply device, such as a screw conveyor or the like.

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Claims (14)

1. A method of conducting beaker welding by using a metal welding electrode (9) whose electrically conductive substance is brought to the area of the beaker (1), characterized in that the substance being brought to the area of the beaker (1) is semi-solid or alternatively solid paste-like substance, which is at least partially water-soluble and forms an electrolyte. 2. A process according to claim 1, characterized in that the substance melts and / or burns away from the arc. Process according to Claim 1 or 2, characterized in that the substance is a metal, non-metal, or the like of an organic or inorganic acid. 4. A process according to any one of claims 1-3, characterized in that the substance consists mainly of the alkali salts of fatty acids » Process according to any of claims 1-4, characterized in that the substance is soap or soap. Method according to any of claims 1-5, characterized in that the blank is spread for protection over the upright weld and / or over its operating range. Process according to any one of claims 1-6, characterized in that the beaker has been arranged to burn partially or substantially completely within the substance or mass, paste, liquid, liquid mixture, solution or the like containing substance. Method according to any of claims 1-7, characterized in that the blank is guided into the area of the beaker partially or completely through an annular nozzle (4) surrounding