AU2015203229A1 - Welding Process - Google Patents

Abstract

1. A welding process comprising the steps of: 5 i) providing a metal cored welding wire having a thickness of 1.2 to 1.6 mm, comprising an external metal casing and a filling material containing iron which represents 8 to 27% by weight of the total mass of the wire, said filling material contains 0.035% to 1.8% calcium by weight of the mass of the filing materials, or 100 ppm to 0.14% by weight of the total mass of the wire; ii) a shielding gas comprising 13.5% to 16.5% carbon dioxide and 9% to 11% helium with the remainder being argon; and iii) a welding surface comprising a low carbon, low alloy, high strength steel. <filename> Figure 1 of 2 Sdtted skit Selected stmtot A ab o Current (A longer arc activity 'Ire (A logracatvt

Description

1 2015203229 15 Jun2015

Welding Process

The present application relates to a welding process which avoids the formation of 5 slag. In particular, the invention described herein relates to selection of the combination of a metal cored welding wire together with a welding gas for a welding process with high strength carbon steels with improved deposition rates.

Background of the Invention 10 Arc welding is a type of welding that may use either a direct current (DC) or an alternating current (AC) to create an electric arc between an electrode and the base material so as to melt the metals at the welding point. The electrode itself may be either a consumable or a non-consumable electrode. The welding region is usually protected by some type of shielding gas, vapour or slag. The purpose of the shielding 15 gas, vapour or slag is to protect the molten weld pool from atmospheric contaminations, which may weaken the weld joint as the weld pool cools, through oxidation or reactions with nitrogen.

One common technique is referred to as “shielded metal arc welding” where an 20 electric current is used to strike an arc between the base metal and a consumable electrode rod or stick. The electrode rod is made from material that is compatible with the base material being welded and is covered with a flux that gives off vapours that serve as a shielding gas and provide a layer of slag, which are capable of protecting the weld area from atmospheric contamination. This process has the disadvantage 25 that the electrode is consumable and must be frequently replaced. The slag which forms must also be chipped away after welding.

An inert gas may be used as a shielding gas where the gas provides a shield around the weld site. It is often problematic to use such gases in areas of high air movement. 30 Flux cored arc welding is a variation of this technique where a fine metal tube filled with powdered flux material is used, where the flux creates a slag which is relied upon to generate the necessary protection from the atmosphere at the weld site. 4307181.1 2 910Z mf ς\ βΖΖ£0Ζ9\0Ζ

Slag is produced in some arc welding processes, particularly shielded metal arc welding processes, and is formed when flux, which may be either the solid shielding material or the core of the welding wire melts in, or on top of the welding zone. Slag is the solidified remaining flux after the weld area cools. Slag does not contribute to 5 the strength or protection of metals after the welding process and is a waste material.

Removal of the slag is necessary so as to allow inspection of the quality of the weld area. It is also important to remove the slag for aesthetics or visual appearance. Removal of slag is usually done manually or with power tools such as a needle gun, 10 and can be a time consuming process. If a second layer of welding is to be made on top of the first, the slag must also be removed first. It is also necessary to remove the slag if a clean or clear surface area is required for coating, such as with a paint or oil.

Flux cored wires are generally well accepted in that they do provide for significant 15 metal penetration, smooth arc transfers, low spatter levels and are generally relatively easy to use although in general, they are limited to flat and horizontal operating positions. The equipment required to use them is also generally heavy and cumbersome. Smaller diameter wires have emerged which does allow flux cored wire to be used in a greater variety of welding positions. 20

As an alternative to the flux cored welding wire, metal cored welding wires have been developed where the core includes significant quantities of iron. Metal cored wires were developed with a view to providing a continuous process that was faster, better and more economical than that which was known with flux cored wires. The aim of 25 metal cored wires is to achieve a higher deposition rate, i.e. the amount of weld metal deposited per hour. The outer metallic sheath of a cored wire conducts the electrical current for welding. It is understood that as a cored wire is composite in nature, they have a greater ability to carry current which improves deposition rates. Metal cored wires are predominantly composed of alloys, such as alloys with manganese, silicon, 30 nickel, chromium as well as very small amounts of arc stabilisers such as sodium and potassium with the balance being iron powder. Metal cored wires give the benefit of being able to have alloy compositions formulated for specific applications and have the benefit of having little to no slag forming ingredients in the internal fill of the wire. 4307181.1 3 2015203229 15 Jun2015

The use of a metal cored welding wire may be used with a high argon gas mixture as the shielding gas. This has the advantage of reducing fume generation however it does generate more heat and higher amounts of radiant light. This can make the process unsuitable for use with certain metals, and/or requires the use of robotic 5 machines, limiting the ability to manually conduct the weld.

Carbon steels are steels where an alloying constituent is carbon. Generally, a low carbon steel could have a carbon content of from 0.1% to 0.5% by weight and the strength is classified depending on other alloy constituents. High carbon steels have 10 a carbon content above 0.25% up to 2.0% by weight or higher, and again, the strength is classified by other alloy constituents. High carbon steels have generally undergone a heat treatment and are usually combined with other alloying material such as manganese, chromium, cobalt, molybdenum, nickel, titanium, silicon and copper. Higher carbon steels tend to be very strong and used where high strength of 15 the steel is required, such as high strength springs. However, they are not particularly ductile and are not as malleable as low or mild carbon steels.

Low carbon steel may also be high strength depending on other alloying components. In general, higher carbon content steels are difficult to weld as they have a lower 20 melting point and are susceptible to cracking upon the application of heat.

It is a desired feature of the present application to provide a process where a welding gas is selected which in combination with a welding wire is able to provide a sufficient shield around the weld site either without or with minimal formation of slag, and with a 25 high weld deposition rate.

It is a further desired feature to select a combination of a welding wire and a welding gas that is compatible for welding a high strength, low alloy, low carbon steel without the formation of slag or with minimal formation of slag. 30

It is a further desired feature to select a combination of a welding wire, a welding gas, a mean arc voltage and/or a wire feed rate that can create a high average Arc-on time and is compatible for the welding of a high strength, low alloy, low carbon steel with a high weld deposition rate. 4307181.1 4 2015203229 15 Jun2015

It is a further desired feature to select a combination of a welding wire and a welding gas that is compatible for welding a high strength, low alloy, low carbon steel and provide a strong weld suitable for the fabrication of mining buckets. 5 A reference herein to a material which is given as prior art is not to be taken as an admission that that matter was known or that the information was part of the common general knowledge as at the priority date of any of the claims.

Throughout the description and the claims of this specification the word “comprise” 10 and variations of the word, such as “comprising” and “comprises” is not intended to exclude other additives, components, integers or steps.

Outline of the Invention

The present invention relates to a welding process comprising the steps of: 15 i) Providing a metal cored welding wire having a thickness of 1.2 to 1.6 mm, comprising an external metal casing and a filling material containing iron which represents 8 to 27% by weight of the total mass of the wire, said filling material contains 0.035% to 1.8% calcium by weight of the mass of the filing material; or 20 100 ppm to 0.14% by weight of the total mass of the wire; ii) A shielding gas comprising 13.5% to 16.5% carbon dioxide and 9% to 11% helium with the remainder being argon; and 25 iii) A welding surface comprising a low carbon, low alloy, high strength steel.

In a further preferred form, the filling material is from 9% to 22% of the total mass of the wire, more preferably from 10% to 20%. 30 In a further preferred form, calcium is in the form of one or more metal alloys and/or mineral form.

In a further preferred embodiment, the outer metal casing of the welding wire is formed of at least 90% by weight of iron. 4307181.1 5 2015203229 15 Jun2015

In a further preferred form, the filling material contains one or more elements selected from iron powder, the components of de-oxidising elements such as Fe-Mn-Si or Fe, alloying elements such as nickel, chromium and/or molybdenum and an arc stabiliser such as sodium and potassium. The alloying elements are preferred for welding a 5 low alloy steel. In a preferred form, the filling material further includes 0.01% to 0.25% carbon, 0.1% to 1.85% silicon, 1% to 2.9% manganese, 0.001% to 0.03% sulfur, 0.001% to 0.1% aluminium, 0.001% to 0.2% titanium and/or 1 to 150 ppm boron, all based on the % by weight of the total weight of the metal cored wire. 10 Preferably the total amount of calcium is less than 1.7% by weight of the mass of the filling material. Preferably, calcium may be in the form of metal alloys such as silico-calcium and/or mineral form such as calcium carbonate, calcium silicates or calcium sulphates. 15 It has been found that the wire melting speed is improved when the current range is preferably within the average range of from 155 amps to 300 amps, more preferably in the range of 200 amps to 280 amps, but most preferably in the range of 250 and 270 amps. The voltage is preferably in the range of from 22 to 30 v, more preferably in the range of 24 to 29 v, but most preferably in the range of between 26 and 27 v. 20

In a further preferred embodiment, the metal cored wire may be fed at a rate of 3.0 to 8 m/min., more preferably in the range of 4.5 to 7.5 m/min, but most preferably in the range of 5.5 to 6.5m/min. 25 Preferably, the wire has a thickness of approximately 1.4 mm.

In a most preferred form, the welding wire is Fluxofil™.

The shielding gas is preferably a mixture of argon, carbon dioxide and helium. Most 30 preferably, the shielding gas has approximately 15% by volume carbon dioxide; ± 10% of this constituent; approximately 10% helium ± 10% of this constituent; with the remainder being argon. A most preferred shielding gas is an Areal gas, most preferably Areal 211 ™. 4307181.1 6 2015203229 15 Jun2015

Preferably the gas is applied at a flow rate of from 18 L/min to 25 L/Min. More preferably, the gas is applied at a flow rate of about 20 L/min, with an increase of no more than 20% or a decrease of no more than 10%. Most preferably, the gas is applied at a flow rate approximately 20 L/min. The gas is preferably applied during 5 spray transport mode.

Detailed Description of the Invention

The combination of welding wire and gas has been found to be particularly beneficial for use in welding carbon steel, namely an alloy of carbon and iron, which may 10 include other elements, such as manganese, chromium, cobalt, molybdenum, nickel or other alloying metals. High tensile strength carbon steels have been found to be difficult to weld, as they may be prone to cracking where extra heat is produced, such as when metal cored welding wires are used. High tensile strength steels are best welded with a low hydrogen process such as with low hydrogen consumable 15 electrodes. Thick sections may require pre-heating which will reduce the cooling rate.

Higher tensile strength steels such as those with greater than 1% manganese, become difficult to weld without cracking. They do require preheating and temperature control together with low hydrogen consumables to avoid cracking. 20

The process of the present invention relates to the use of a metal cored welding wire, together with a carbon dioxide, helium and argon gas that has been found to be particularly suitable for welding a low carbon, low alloy, high strength steel. 25 In the process of the present invention, the current that may be applied is preferably from 155 to 300 amps, more preferably 200 to 280 amps, and most preferably in the range of 230 to 270 amps. Preferably, the mean arc voltage of the electrode used is from 22 to 30 v, more preferably 24 to 29 v, but most preferably 26 to 27 v ± 7% of the specified mean arc voltage. It has been found that the metal cored wire is able to 30 carry such electrical currents, which leads to an increase in the deposition rate.

The process of the present invention is able to achieve an average Arc-on time in the range of from 25 to 55 seconds over a series of welds. Preferably the average Arc-on time achieved is in the range of 25 to 45 seconds over the series of welds. This may 4307181.1 7 2015203229 15 Jun2015 be achieved as the need to de-scale has been removed through the lack of build-up of slag, leading to greater deposition rates preferably in the range of 28 to 34 kg/hr or higher. 5 The process of the present invention has particular benefit for welding of high tensile strength carbon steel. In one embodiment, the process is particularly applicable to weld a steel having a tensile strength of from 790 to 930 MPa, preferably approximately 830 MPa. In one particular embodiment, the process has been found to be particularly useful when the steel includes from 1% to 2% manganese, 10 preferably about 1.5% manganese. More preferably, the low carbon, low alloy, high strength steel has from 0.16 to 0.22 % by weight carbon, preferably 0.18 to 0.2% by weight carbon.

Such steels are useful in the mining industry where the steel is subjected to particular 15 abrasive action. A particularly preferred steel is BisPlate 80™, which is useful in the fabrication of mining buckets and the like.

It has been found that with the correct selection of the welding wire together with the wire thickness, the shielding gas and the correct selection of the various settings 20 including mean arc voltage, current and wire feed rate, that it is possible to have a significant increase in the Arc-on time and the deposition rate of the weld. When using a flux cored wire, there is post-weld activity to remove the flux prior to welding being conducted again. This activity significantly lowers the deposition rate of the weld, because the welder cannot re-weld over the slag. With the use of a metal cored 25 wire, this post-weld activity is removed as there is no need to remove the slag.

It has been found that with the process of the present application that a weld deposition rate of between 28 to 34 kg/hr or higher may be achieved. Current rates of between 12 to 16 kg/hr using a flux core wire and Areal 8™ gas may be achieved. 30 Metal core wires may have a deposition rate of about 20kg/hr although the presence of helium or otherwise may vary this rate. Helium is a chemically inert gas with the highest electron volt value in the mixture of 24.5 eV. Therefore it does not add additional oxidising activity but brings more heat value to the plasma column. So overall, it helps the wire melt rate at any given amp voltage setting. 4307181.1 2015203229 15 Jun2015 8

The process of the present invention has been found to be particularly useful for the welding of high strength steels that are used in particularly abrasive environments such as in the mining industry. A particularly preferred metal for welding is a high 5 tensile strength carbon steel such as BisPlate 80™ carbon steel. Such metals have been particularly suitable for use as mining buckets. The improved deposition rate of the weld provides a significant advantage in the fabrication of such mining buckets.

Brief Description of the Drawings 10 Figure 1 illustrates a measurement of the current in Amps, and a measure of the Arc-on time for a trial using Areal 211 ™ gas and Fluxofil™ wire.

Figure 2 illustrates a measurement of the current in Amps and a measure of the Arc-on time for a trial using Areal 8™ gas at a Flux Centred Arc Welding wire. 15

Examples Example 1

This example demonstrates a welding trial conducted over approximately 27 minutes, 20 where Areal 211 ™ was used as the gas, and Fluxofil™ was used for the welding wire. The average current in Amps, the Arc-on time and the deposition rate were measured amongst other criteria. The metal to be welded was Bisalloy 80™ carbon steel.

Performance per station

Coiortorl fimo slot 12/01/2015 [14:05:00 - 20:05:00]

Selected shift 2

Selected shop Liebherr Australia Assodated gas Areal 211 Selected station stationl Process [135] GMAW (Active gas) Duty cyde 20.8/¾ Wire type Tubular Deposition rate 30.78 Kg/h Wire diameter 1.4 mm 4307181.1 9 2015203229 15 Jun2015

Time Weld number Average current (A) Average wire speed {m/min} Arc-on time (s) Wire used C^g) Wire deposited i*g) 16:13:02 37 168 3.5 15 0.59 0.56 16:13:25 38 169 3.5 13 0.52 0.49 16:13:40 39 169 3.5 35 1.43 1.36 16:14:19 40 176 3.7 98 4.19 3.98 16:16:22 41 167 3.4 10 0.41 0.39 16:17:26 42 173 3.6 85 3.56 3.39 16:19:05 43 171 3.6 68 2.79 2.65 16:20:13 44 173 3.6 5 0.21 0.2 16:20:18 - - - < 1 s - - 16:20:19 46 167 3.4 7 0.27 0.25 16:20:39 - - - < 1 5 - - 16:20:39 48 175 3.7 38 1.61 1.53 16:21:17 49 155 3.1 2 0.05 0.05 16:21:44 - - - < 1 5 - - 16:21:46 51 171 3.5 92 3.77 3.58 16:23:32 52 171 3.5 116 4.8 4.56 16:26:05 53 170 3.5 75 3.05 2.9 16:27:36 54 174 3.6 112 4.73 4.49 16:30:54 - - - < 1 5 - - 16:30:55 56 170 3.5 7 0.28 0.27 16:31:02 57 171 3.5 10 0.38 0.36 16:31:15 58 162 3.3 12 0.47 0.45 16:31:32 - - - < 1 5 - - 16:31:32 60 170 3.5 30 1.22 1.16 16:32:05 61 173 3.6 2 0.08 0.08 16:32:07 - - - < 1 5 - - 16:32:09 63 167 3.4 31 1.23 1.17 16:39:12 64 171 3.5 45 1.85 1.76 16:40:00 65 161 3.3 23 0.86 0.81 16:40:25 66 161 3.3 4 0.16 0.15 16:40:33 67 173 3.6 _ Average arr : ............72............. 3.02 2.87 on 1 40.3 5 10 4307181.1 10 2015203229 15 Jun2015

Example 2

This example demonstrates a welding trial conducted over approximately 22 minutes, where Areal 8™ was used as the gas, and a Flux Centred Arc Welding Wire was 5 used. The average current in Amps, the Arc-on time and the deposition rate were measured amongst other criteria. The metal to be welded was Bisalloy 80™ carbon steel.

Performance per station

Selected time slot 12/01/2015 [14:05:00 - 20:05:00]

Selected shift 2

Liebherr Associated Australia gas Areal 8

Selected station station3 Process [136] FCAW Duty cycle Deposition rate Table 2 15.85 Kg/h Wire type Wire diameter Tubular 1.6 mm Time Weld number Average current (A) Average wire speed (m/min) Arc-on time is) Wire used (Kg> Wire deposited (Kg) 19:13:24 109 290 7 25 2.01 1.71 19:14:03 110 298 7.2 20 1.67 1.42 19:14:42 111 298 7.2 19 1.59 1.35 19:15:16 112 306 7.4 20 1.73 1.47 19:15:58 113 299 7.2 17 1.43 1.22 19:16:31 114 300 7.3 17 1.39 1.18 19:17:13 115 298 7.2 13 1.09 0.92 19:17:37 116 290 7 11 0.87 0.74 19:18:04 117 292 7.1 17 1.36 1.15 19:18:44 118 300 7.3 21 1.78 1.51 19:19:23 119 302 7.3 17 1.44 1.23 19:19:57 120 298 7.2 17 1.45 1.24 19:20:30 121 298 7.2 15 1.22 1.04 19:21:08 122 300 7.3 25 2.12 1.8 19:21:47 123 297 7.2 19 1.56 1.32 19:22:34 124 297 7.2 22 1.85 1.57 19:23:27 125 299 7.2 18 1.52 1.29 19:24:11 126 277 6.6 19 1.49 1.27 19:24:42 127 282 6.8 18 1.44 1.23 19:25:17 128 283 6.8 17 1.33 1.13 19:25:58 129 282 6.8 22 1.69 1.44 4307181.1 2015203229 15 Jun2015 19:26:40 130 19:27:12 131 19:27:42 132 19:28:12 133 19:28:42 134 19:29:28 135 19:30:00 136 19:30:32 137 19:31:04 138 19:31:32 139 19:32:02 140 19:33:29 141 19:33:56 142 19:34:21 143 19:34:47 144 19:35:13 145 19:35:39 146 11 279 6.7 290 7 278 6.7 280 6.7 278 6.7 275 6.6 282 6.8 281 6.8 289 7 286 6.9 275 6.6 278 6.7 280 6.7 281 6.8 281 6.8 284 6.8 282 6.8

Average Arc on 19 1.51 1.28 19 1.55 1.32 19 1.43 1.22 18 1.4 1.19 26 2.03 1.72 21 1.61 1.36 19 1.52 1.29 19 1.49 1.27 17 1.38 1.17 16 1.28 1.09 23 1.79 1.52 17 1.27 1.08 15 1.15 0.97 16 1.21 1.03 15 1.13 0.96 14 1.13 0.96 12 0.95 0.81 183 !

Example 1 demonstrates that use of Areal 211™ gas together with Gas Metal Arc Welding wire Fluxofil™, provided an average Arc-on time of 40.3 seconds. This average Arc-on time is demonstrative of an improved rate of deposition of the wire. 5 The deposition rate achieved was 30.78 kg/hr.

Figure 1 demonstrates the increase in Arc-on time with longer duration of arc activity. The increase in Arc-on time together with the fact that there is no need for descaling as no flux has been deposited, has led to the increase in the deposition rate achieved. 10

Example 2 provides a comparative example where the welding wire was a Flux Centred Arc Welding Wire and the gas used was Areal 8™. The average Arc-on time achieved was 18.3 seconds, which led to a weld deposition rate of 18.85 kg/hour. The average voltage across a range of welds is shown in Figure 2, where the reduced 15 Arc-on time may be seen by the shorter arc activity.

The metal welded in each of Examples 1 and 2 was a low carbon, low alloy, high strength Bisalloy carbon steel. 4307181.1 12 2015203229 15 Jun2015

The process of the present invention does provide significant improvement in the deposition rate of the weld leading to time and cost savings.

Example 3 5 Two multiple weld runs were conducted using a Bisalloy carbon steel with a thickness of 30.5 millimetres. The welding wire used was Fluxofil™ M10MCW.

In the first run, a fillet weld was conducted with a 1.4 millimetre welding wire fed at 5.5-6.5 m/min. The voltage was 26-27 v with current amp 230-270. The shielding 10 gas used was Areal 211™ while the welding technique was a push technique. The flow rate of the gas was 20 L/min and the size of the weld was 9 mm. The same welding parameters were also used for a double V butt weld, producing a weld size of 7-11 mm. 15 With both these test welds, no slag was produced, while the shielding gas provided sufficient protection to prevent atmospheric conditions form affecting the weld. 20 25 30 35 40 4307181.1

Claims (21)

1. The Claims Defining the Invention Are As Follows:

   1. A welding process comprising the steps of: i) providing a metal cored welding wire having a thickness of 1.2 to 1.6 mm, comprising an external metal casing and a filling material containing iron which represents 8 to 27% by weight of the total mass of the wire, said filling material contains 0.035% to 1.8% calcium by weight of the mass of the filing materials, or 100 ppm to 0.14% by weight of the total mass of the wire; ii) a shielding gas comprising 13.5% to 16.5% carbon dioxide and 9% to 11% helium with the remainder being argon; and iii) a welding surface comprising a low carbon, low alloy, high strength steel.
2. 2. A welding process according to claim 1 wherein the outer metal casing of the welding wire is formed of at least 90% by weight of iron.
3. 3. A welding process according to claim 1 wherein calcium is in the form of one or more metal alloys and/or mineral form.
4. 4. A welding process according to claim 1 wherein the filling material is from 9% to 22% of the total mass of the wire, preferably from 10% to 20%.
5. 5. A welding process according to claim 1 wherein the filling material contains one or more elements selected from iron powder, the components of de-oxidising elements, alloying elements and an arc stabiliser.
6. 6. A welding process where the thickness of the welding wire is about 1.4 mm.
7. 7. A welding process according to any one of the preceding claims wherein the welding wire is Fluxofil™.
8. 8. A welding process according to any one of the preceding claims wherein the shielding gas is approximately 15% carbon dioxide ± 10% of this constituent; approximately 10% helium ± 10% of this constituent with the remainder being argon.
9. 9. A welding process according to any one of the preceding claims wherein the shielding gas is an Areal™ gas.
10. 10. A welding process according to claim 9 wherein the shielding gas is Areal 211™.
11. 11. A welding process according to any one of the preceding claims wherein the shielding gas is applied at a flow rate of from 18 L/min to 25 L/min, more preferably from approximately 20L/min with an increase of no more than 25% and a decrease of no more than 10%.
12. 12. A welding process according to any one of the preceding claims wherein the arc voltage of the electrode used is from 22 to 30 v, preferably from 24 to 29 v, and more preferably from 26 to 27 v ± 7% of the specified mean arc voltage.
13. 13. A welding process according to any one of the preceding claims wherein the low carbon, low alloy high strength steel includes from 1 to 2% manganese, preferably about 1.5% manganese by weight.
14. 14. A welding process according to any one of the preceding claims wherein the low carbon, low alloy high strength steel has from 0.16 to 0.22%, preferably 0.18 to 0.2%, by weight of carbon.
15. 15. A welding process according to any one of the preceding claims wherein the low carbon, low alloy, high strength steel has a tensile strength of from 790 to 930 MPa, preferably approximately 830 MPa.
16. 16. A welding process according to any one of the preceding claims wherein the low carbon, low alloy, high strength steel is Bisalloy 80™ carbon steel.
17. 17. A welding process according to any one of the preceding claims wherein the metal cored wire is fed at a rate of 3 to 8 m/min, preferably 4.5 to 7.5 m/min., and more preferably 5.5 to 6.5 m/min.
18. 18. A welding process according to any one of the preceding claims, wherein a current of 155 to 300 amps, preferably 200 to 280 amps and more preferably 230 to 270 amps is applied.
19. 19. A welding process wherein the deposition rate is 24 to 34 kg/hour, preferably about 30 kg/hour.
20. 20. A welding process wherein the Arc-on time is an average of 25 to 55 seconds, preferably 35 to 45 seconds, over a series of welds.
21. 21. A welding process according to any one of the preceding claims wherein the arc welding process is performed in a vertical downward position.