Covered Arc-Welding Electrode

A covered arc welding electrode includes a steel core wire and a flux which is applied to the outside periphery of said steel core wire. The welding electrode can form a superior crack-resisting weld zone even if fluctuating stresses are continually applied to a base metal while the base metal is welded. The flux includes 40 to 60% metal carbonate, 10 to 25% metal fluoride and 4 to 25 metal oxide by weight. The flux comprises 24 to 32% of the total weight of said electrode. The composition of the welding electrode includes 0.005 to 0.05% carbon, 0.1 to 1.1% silicon, 1.5 to 2.5% manganese, not more than 0.007% sulfur and not more than 0.25% nickel by weight and the manganese/sulfur ratio is more than or equal to 350 to 1. In addition, the welding electrode can include 0.01 to 0.10% rare earth metal by weight. In which case, the Mn content may be 1.0 to 2.5% by weight and the manganese/sulfur ratio may be more than or equal to 270 to 1. In addition, the composition of the welding electrode can include titanium and zirconium, the total content of which may be less than or equal to 1.2% the total weight of the electrode, and/or aluminum and magnesium, the total content of which may be less than or equal to 1.2% of the total weight of the electrode.

1. A covered arc welding electrode comprising:
a flux including 40 to 60% metal carbonate, 10 to 25% metal fluoride and 4 to 25% metal oxide by weight; and a steel core wire, onto the outer periphery of which said flux is applied so as to comprise 24 to 32% of the total weight of said electrode, said electrode as a whole being comprised of 0.005 to 0.05% carbon, 0.1 to 1.1% silicon, 1.5 to 2.5% manganese, not more than 0.007% sulfur and not more than 0.25% nickel by weight and in which the manganese/sulfur ratio is more than or equal to 350 to 1.

2. A covered arc-welding electrode as set forth in claim 1, further comprising titanium and zirconium, the total content of which is less than or equal to 1.2% of the total weight of the electrode.

3. A covered arc-welding electrode as set forth in claim 2, further comprising aluminum and magnesium, the total content of which is less than or equal to 1.2% of the total weight of the electrode.

4. A covered arc-welding electrode as set forth in claim 1, further comprising aluminum and magnesium, the total content of which is less than or equal to 1.2% of the total weight of the electrode.

5. A covered arc-welding electrode comprising:
a flux including by weight 40 to 60% metal carbonate, 10 to 25% metal fluoride and 4 to 25% metal oxide; and a steel core wire, onto the outer periphery of which said flux is applied so as to comprise 24 to 32% of the total weight of said electrode;
said electrode as a whole being comprised of 0.005 to 0.05% carbon, 0.1 to 1.1% silicon, 1.0 to 2.5% manganese, not more than 0.007% sulfur, not more than 0.25% nickel and 0.01 to 0.10% rare earth metal by weight and in which the manganese/sulfur ratio is more than or equal to 270 to 1.

6. A covered arc-welding electrode as set forth in claim 5, further comprising titanium and zirconium, the total content of which is less than or equal to 1.2% of the total weight of the electrode.

7. A covered arc-welding electrode as set forth in claim 6, further comprising aluminum and magnesium, the total content of which is less than or equal to 1.2% of the total weight of the electrode.

8. A covered arc-welding electrode as set forth in claim 5, further comprising aluminum and magnesium, the total content of which is less than or equal to 1.2% of the total weight of the electrode.

Safety Issues

Welding can be a dangerous and unhealthy practice without the proper precautions; however, with the use of new technology and proper protection the risks of injury or death associated with welding can be greatly reduced.

[edit] Heat and sparks
Because many common welding procedures involve an open electric arc or flame, the risk of burns is significant. To prevent them, welders wear protective clothing in the form of heavy leather gloves and protective long sleeve jackets to avoid exposure to extreme heat, flames, and sparks.

[edit] Eye damage
The brightness of the weld area leads to a condition called arc eye in which ultraviolet light causes inflammation of the cornea and can burn the retinas of the eyes. Goggles and helmets with dark face plates are worn to prevent this exposure and, in recent years, new helmet models have been produced featuring a face plate that self-darkens upon exposure to high amounts of UV light. To protect bystanders, transparent welding curtains often surround the welding area. These curtains, made of a polyvinyl chloride plastic film, shield nearby workers from exposure to the UV light from the electric arc, but should not be used to replace the filter glass used in helmets.[26]
Those dark face plates must be much darker than those in sunglasses or blowtorching goggles. Sunglasses and blowtorching goggles are not adequate for arc welding protection.
In 1970, a Swedish doctor, Åke Sandén, developed a new type of welding goggles that used a multilayer interference filter to block most of the light from the arc. He had observed that most welders could not see well enough, with the mask on, to strike the arc, so they would flip the mask up, then flip it down again once the arc was going: this exposed their naked eyes to the intense light for a while. By coincidence, the spectrum of an electric arc has a notch in it, which coincides with the yellow sodium line. Thus, a welding shop could be lit by sodium vapor lamps or daylight, and the welder could see well to strike the arc. The Swedish government required these masks to be used for arc welding, but they were not used in the United States. They may have disappeared.[27]

[edit] Inhaled matter
Welders are also often exposed to dangerous gases and particulate matter. Processes like flux-cored arc welding and shielded metal arc welding produce smoke containing particles of various types of oxides. The size of the particles in question tends to influence the toxicity of the fumes, with smaller particles presenting a greater danger. Additionally, many processes produce various gases (most commonly carbon dioxide and ozone, but others as well) that can prove dangerous if ventilation is inadequate. Furthermore, the use of compressed gases and flames in many welding processes pose an explosion and fire risk; some common precautions include limiting the amount of oxygen in the air and keeping combustible materials away from the workplace.[28]

[edit] Interference with pacemakers
Certain welding machines which use a high frequency AC current component have been found to affect pacemaker operation when within 2 meters of the power unit and 1 meter of the weld site[29].

Consumable Electrode Methods

One of the most common types of arc welding is shielded metal arc welding (SMAW), which is also known as manual metal arc welding (MMA) or stick welding. An electric current is used to strike an arc between the base material and a consumable electrode rod or 'stick'. The electrode rod is made of a material that is compatible with the base material being welded and is covered with a flux that protects the weld area from oxidation and contamination by producing CO2 gas during the welding process. The electrode core itself acts as filler material, making a separate filler unnecessary. The process is very versatile, requiring little operator training and inexpensive equipment. However, weld times are rather slow, since the consumable electrodes must be frequently replaced and because slag, the residue from the flux, must be chipped away after welding.[16] Furthermore, the process is generally limited to welding ferrous materials, though specialty electrodes have made possible the welding of cast iron, nickel, aluminium, copper and other metals. The versatility of the method makes it popular in a number of applications including repair work and construction.[17]
Gas metal arc welding (GMAW) is a semi-automatic or automatic welding process that uses a continuous wire feed as an electrode and an inert or semi-inert shielding gas to protect the weld from contamination. When using an inert gas as shield it is known as Metal Inert Gas (MIG) welding. A constant voltage, direct current power source is most commonly used with GMAW, but constant current systems as well as alternating current can be used. GMAW welding speeds are relatively high due to the automatically fed continuous electrode, but is less versatile because it requires more equipment than the simpler SMAW process. Originally developed for welding aluminium and other non-ferrous materials in the 1940s, GMAW was soon applied to steels because it allowed for lower welding time compared to other welding processes. Today, GMAW is commonly used in industries such as the automobile industry, where it is preferred for its versatility and speed. Because it employs a shielding gas, however, it is rarely used outdoors or in areas of air volatility.[18]
A related process, flux-cored arc welding (FCAW), uses similar equipment but uses wire consisting of a steel electrode tube surrounding a powder fill material. This cored wire is more expensive than the standard solid wire and generates extra shielding gas and/or slag, but it permits higher welding speed and greater metal penetration.[19]
Submerged arc welding (SAW) is a high-productivity automatic welding method in which the arc is struck beneath a covering layer of flux. This increases arc quality, since contaminants in the atmosphere are blocked by the flux. The slag that forms on the weld generally comes off by itself and, combined with the use of a continuous wire feed, the weld deposition rate is high. Working conditions are much improved over other arc welding processes since the flux hides the arc and no smoke is produced. The process is commonly used in industry, especially for large products.[20] As the arc is not visible, it requires full automatization. In-position welding is not possible with SAW.

Power Supplies

To supply the electrical energy necessary for arc welding processes, a number of different power supplies can be used. The most common classification is constant current power supplies and constant voltage power supplies. In arc welding, the voltage is directly related to the length of the arc, and the current is related to the amount of heat input. Constant current power supplies are most often used for manual welding processes such as gas tungsten arc welding and shielded metal arc welding, because they maintain a relatively constant current even as the voltage varies. This is important because in manual welding, it can be difficult to hold the electrode perfectly steady, and as a result, the arc length and thus voltage tend to fluctuate. Constant voltage power supplies hold the voltage constant and vary the current, and as a result, are most often used for automated welding processes such as gas metal arc welding, flux cored arc welding, and submerged arc welding. In these processes, arc length is kept constant, since any fluctuation in the distance between the wire and the base material is quickly rectified by a large change in current. For example, if the wire and the base material get too close, the current will rapidly increase, which in turn causes the heat to increase and the tip of the wire to melt, returning it to its original separation distance.[12]
The direction of current used in arc welding also plays an important role in welding. Consumable electrode processes such as shielded metal arc welding and gas metal arc welding generally use direct current, but the electrode can be charged either positively or negatively. In welding, the positively charged anode will have a greater heat concentration and, as a result, changing the polarity of the electrode has an impact on weld properties. If the electrode is positively charged, it will melt more quickly, increasing weld penetration and welding speed. Alternatively, a negatively charged electrode results in more shallow welds.[13] Non-consumable electrode processes, such as gas tungsten arc welding, can use either type of direct current (DC), as well as alternating current (AC). With direct current however, because the electrode only creates the arc and does not provide filler material, a positively charged electrode causes shallow welds, while a negatively charged electrode makes deeper welds.[14] Alternating current rapidly moves between these two, resulting in medium-penetration welds. One disadvantage of AC, the fact that the arc must be re-ignited after every zero crossing, has been addressed with the invention of special power units that produce a square wave pattern instead of the normal sine wave, eliminating low-voltage time after the zero crossings and minimizing the effects of the problem

STAINLESS STEEL AND SPECIAL ELECTRODES

1-SATINCROME 308L-17

Description and Applications:

Satincrome 308L-17 is a smooth running, rutile type stainless steel electrode manufactured by CIGWELD for the all positional (except vertical-down) fillet and butt welding of 19Cr/10Ni type stainless steels. The features of Satincrome 308L-17 include high AC arc stability, sound radiographic quality, smooth arc transfer characteristics, very low spatter levels and excellent bead shape and contour. The advanced moisture resistant (MR) flux coating provides improved resistance to start-of-run porosity. Slag lift of Satincrome 308L-17 is enhanced in all welding positions, it is self peeling and non-spitting. Applications of Satincrome 308L-17 include the single and multi-pass welding of 19Cr/10Ni type stainless steel grades including 201, 202, 301, 302,303, 304, 304L, 305, 308 etc.

2-SATINCROME 309Mo-17

Description and Applications:

Satincrome 309Mo-17 is a rutile type, high alloy stainless steel electrode manufactured by CIGWELD for the all positional (except vertical-down) fillet and butt welding of 24Cr/13Ni type stainless steels. The features of Satincrome 309Mo-17 include high AC arc stability, sound radiographic quality, smooth arc transfer characteristics, very low spatter levels and excellent bead shape and contour. The advanced moisture resistant (MR) flux coating provides improved resistance to start-of-run porosity. Slag lift of Satincrome 309Mo-17 is enhanced in all welding positions, it is self peeling and non-spitting. Applications of Satincrome 309Mo-17 include the single and multi-pass welding of matching 309 and 309L stainless steels. Satincrome 309Mo-17 is also suitable for the dissimilar welding of other “300 series” austenitic stainless steels and selected “400 series” ferritic grades to mild or low alloy steels such as 403, 405, 410, 416, 420, 430, 430F-Se, 446 etc and BHP 3CR12.

3-SATINCROME 316L-17

Description and Applications:

Satincrome 316L-17 is a low carbon, rutile type stainless steel electrode manufactured by CIGWELD for the all positional (except vertical-down) fillet and butt welding of 19Cr/10Ni type stainless steels. The features of Satincrome 316L-17 include high AC arc stability, sound radiographic quality, smooth arc transfer characteristics, very low spatter levels and excellent bead shape and contour. The advanced moisture resistant (MR) flux coating provides improved resistance to start-of-run porosity. Slag lift of Satincrome 316L-17 is enhanced in all welding positions, it is self peeling and nonspitting. Applications of Satincrome 316L-17 include the single
and multi-pass welding of matching Molybdenum bearing stainless steels, 316 and 316L. Satincrome 316L-17 is also suitable for the general purpose welding of other “300 series” austenitic stainless steels including 301, 302, 303 and 304/304L, 305, 3CR12 types. The 2.5% Molybdenum content gives increased resistance to pitting corrosion and raises the creep strength for higher temperature applications.

4-SATINCROME 318-17

Description and Applications:

Satincrome 318-17 is a Niobium stabilised, rutile type stainless steel electrode manufactured by
CIGWELD for the all positional (except vertical-down) fillet and butt welding of stabilised and unstabilised 19Cr/10Ni type stainless steels, such as 316, 318 and 321. The features of Satincrome 318-17 include high AC arc stability, sound radiographic quality, smooth arc transfer
characteristics, very low spatter levels and excellent bead shape and contour. The advanced moisture resistant (MR) flux coating provides improved resistance to start-of-run porosity. Slag lift of Satincrome 318-17 is enhanced in all welding positions, it is self peeling and non-spitting. The Molybdenum content of Satincrome 318-17 gives improved resistance to pitting corrosion and the Niobium addition gives improved resistance to intergranular corrosion and good strength retention at elevated temperatures up to ≈ 700°C.

Steel industry

History of the modern steel industry, Global steel industry trends, Steel production by country, and List of steel producers

It is common today to talk about "the iron and steel industry" as if it were a single entity, but historically they were separate products. The steel industry is often considered to be an indicator of economic progress, because of the critical role played by steel in infrastructural and overall economic development.^[41]

The economic boom in China and India has caused a massive increase in the demand for steel in recent years. Between 2000 and 2005, world steel demand increased by 6%. Since 2000, several Indian ^[42] and Chinese steel firms have risen to prominence like Tata Steel (which bought Corus Group in 2007), Shanghai Baosteel Group Corporation and Shagang Group. ArcelorMittal is however the world's largest steel producer.

The British Geological Survey reports that in 2005, China was the top producer of steel with about one-third world share followed by Japan, Russia, and the USA.^[43]

In 2008, steel started to be traded as a commodity in the London Metal Exchange. At the end of 2008, the steel industry faced a sharp downturn that led to many cut-backs.^[44]

Steel

Steel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese, chromium, vanadium, and tungsten.^[1] Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another. Varying the amount of alloying elements and form of their presence in the steel (solute elements, precipitated phase) controls qualities such as the hardness, ductility, and tensile strength of the resulting steel. Steel with increased carbon content can be made harder and stronger than iron, but is also more brittle.

Alloys with a higher carbon content are known as cast iron because of their lower melting point and castability.^[1] Steel is also distinguished from wrought iron, which can contain a small amount of carbon, but it is included in the form of slag inclusions. Two distinguishing factors are its increased rust-resistance and better weldability.

Though steel had been produced by various inefficient methods long before the Renaissance, its use became more common after more efficient production methods were devised in the 17th century. With the invention of the Bessemer process in the mid-19th century, steel became a relatively inexpensive mass-produced material. Further refinements in the process, such as basic oxygen steelmaking, further lowered the cost of production while increasing the quality of the metal. Today, steel is one of the most common materials in the world and is a major component in buildings, infrastructure, tools, ships, automobiles, machines, and appliances. Modern steel is generally identified by various grades of steel defined by various standards organizations.