JJ104 Workshop Technology CHAPTER9 Arc Welding

WHAT IS ARC WELDING? 

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Arc Welding Welding is the processes processes of joining metal together thru fusion which which is done by the electric electric Arc, Arc, by electrical electrical curren currentt (Arc 1994). 1994). The most most widely widely used type of Arc welding welding is Shielded Metal Arc Welding or stick welding welding (Repp1994). The arc reaches temperatures temperatures of around 6,000 degrees Celsius which is concentrat concentrated ed at the tip of the electrode (Weldwell 2003). The electrodes electrodes have have a metal core core surrou surround nd by flux, which melts melts with the the work work piece piece creating creating a fusion fusion weld. weld. The flux coating coating forms a gas and slag slag that shields shields the molting molting metal pool. This flux material is cleaned cleaned off once once the weld has cooled with a wire wire brush. The weld weld should be as strong strong or stronger then the metal that it is fusing together together.. Shielded Metal  Arc Welding is one of o f the most commonly used types of welding (Repp 1994). This is ecause t s on onee o t e eas est, an t e equ pment ent s nexpens ens ve. e ease o porta ty  makes them very very good for mobile welding. welding.

Arc Welding Equipment he equipment used in arc welding are as follows: 

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 Welding machine as a converter to adjust the welding voltage and current.  Electrode holder is insulated and used to hold the electrode.

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allow the flow of electric current to form the electric arc. 

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 Earthing which connects the base metal and the welding machine power supply to prevent electric shock.  Electrode cable is an electrical connection between the electrode holder and power supply.The cable is insulated with rubber. Cleaning Cleaning tools are used to chip and clean the traces of metal spatters and slag produced on the surface of the welded metal.

Figure :Arc welding joint principle

Electric arc welding carried out by the flow of electricity from the electrodes on the base metal and convert electrical energy into heat energy . Heat energy is used to melt the electrode metal, additional metal or metal connectors are finally done; producing a welded connection. Basically, the more electricity is needed to reach a certain temperature to melt the metal in the short term. Electricity supply from TNB is not suitable for welding works and does not have an impact. Sometimes we use the power transformer to convert electricity supply to the electric current are suitable for use in welding practice. Here are two common types of electrical current used in welding work. a.c.). .). A type of current that changed direction several Alternating current ((a.c times in the flow of current. Alternating current is used to alter the strength and direction 120 times within an hour or an alternating movement within 1 / 60 second. This current frequency of 60 hertz said. In other words, alternating current with a frequency of 60 hertz would alter the strength and direction 60 times per second. (d.c). ). A type of current that has a fixed direction of the flow. Direct current (d.c Remain in the current direction can only be changed by changing the cable connection is used.

elec trical  An electrical

arc occurs when electrical current flows from an electrode tip to the surface of the metal to be welded. This occurs when the current carrying electrodes electrodes in contact with the metal to be welded, and there is voltage voltage between between them. The incident resulted in a high heat in a clan touch base metals and consequently consequently part of the . melting of the electrode tip led to the formation of fine metal balls which moved into the puddles on the base metal occurs through the arc. This is called transfer of  metals. Sometimes a liquid metal that occurs is covered by a protective gases resulting from the melting of the chemical chemical coating of  electrodes and produced from the burning of the

Equipme Equipment nt and Accesso Accessories ries Basic requirements for carrying out a welding supply electrons ¬ trick is to appropriate voltage and current. The required voltage is between 20-100 volts while the current according ampere is between 100-1000. Therefore clear that the power supply from TNB is not appropriate and safe to use for welding work as too high. There are two types of arc welding machines. Namely: a) providing a direct current machine. b) machine that provides alternating current. Direct Current Welding Machine There are two ways to obtain the machines of this type is the set of  generators generators and welding equipment router. advantages (A) Can be used to impose both core and non core electrode. (B) Welding produces a smoother and is useful for welding thin sheet metal. (C) More than safety. safety. Disadvantages (A) the price is higher. (B) Periodic maintenance should be carried out on the type of generating plant because there are moving parts. c) Interference-interferenc Interference-interference e from 'Arc blow'.

Alternating current Welding Machine Alternating current supply for the welding work is ossible ossible from a transfo transformer rmer Here Here the main electricity supply to the power of 230250 volts down to a value of less than 100 volts by the converters. This transformer has a flow control regulator that allows the operator to choose the appropriate value of  current equal to the size of electrodes used. In terms of efficiency and convenience, alternating current equipment is superior. superior. Advantages Advant ages only (A) The price is cheaper. (B) A little maintenance is required or may not be needed immediately. This is because there are no moving parts in the transformer. (C) Not applicable 'arc blow'. (D) Can be used at any place.

ArcW Arc Welding elding Machin Machine e Arc Arc weld weldin ing g mach machin ine e is a tran transf sfor orme merr wher where e to chan change ge from from a high high volt voltag age e to low low volt voltag age e but but high high curr curren entt yiel yield d for for the the issu issue e of the the use use of arc arc weld weldin ing. g. Equi Equipp pped ed with with the the elect electro rode de cabl cable e and and eart earth h cabl cable e to the the desk. desk. Basic Basic comp compon onen ents ts in an arc arc weld welding ing mach machin ine e Is cons consist istss of: of: transformers Eart Earth h cabl cable e went went cable cable went went electro electrodes des The electro electrode de Power su l

There are five types of welding machines. Namely: - Type 'rectifier (DC) - Type of transformer (AC) AC / DC - Ty Typ pee-dr driv iven en en eng gin ine. e. (pe petr tro ol or di dies esel el)) drives. (power)

- a combination of   - Ty Type pe of el elec ectr triic moto torr

Arc welding machine type 'rectifier' (successor) is used because it has two options of current flow, the reverse polarity direct current and direct current straight polarity. Positive source is connected to the electrodes so it was the reverse polarity. Sources connected to the negative electrode polarity, then it is straight. All types of welding work for most metals are well suited to this type of  machine. For the construction works and maintenance of machines of this type is the right choice. Weaknesses: - Gener Generate ate 'spray arc' (arc blow) - arc is not so stable against the type of power - There is no option for the arc characteristics.

valid 'arc spray' (arc blow) with the penetration of a simple and quiet. Weaknesses: - welding of certain metals and a limited use. - Not all of the electrodes can be used. - Able to operate at high ampere

This type of machine can use both types of flows. It is necessary when welding certain metals with certain currents. Has the widespread use. Can be used on many types of steel and welding position. Weaknesses: - the relatively high costs - Valid 'arc spray' on some connections.

There are two types of polarity arc welding machine. Namely:

- Polarity Direct Current Back (cables installed on the source electrode positive) positive) - Direct Current Straight Polarity (lektrod cables attached to a negative source)

Feat Fe atur ures es of th the e ol olar arit it of th the e DC ol olar arit it is re reve vers rsed ed:: - The liquidity elekrod faster. - Transparency in the shallow - faster welding speeds are required. Features of the polarity of direct current straight polarity is: - The liquidity of the slow electrode - Transparency of the - The speed of the medium.

Arc distance is the distance between the tip of the metal core with the surface electrodes. Where the arc is issued will be maintained at this distance. Arc distance is too high will cause the molding is beautiful and also a lack of transparency. Arc distance is between 5.0mm to 6.0mm.

Tilt angle formed between the electrodes to the surface in the direction of the electrode bendakerja. The angle of the arc is not right will cause a ripple molding so elongated or oval and make a way not beautiful moldings.

Speed is the speed of movement of the arc electrode to move towards the end of the finish welding. This speed is usually dependent on the liquidity of the electrodes. Weld too fast to make too fine moldings and high and low transparency. When we started the beginning of arc welding in place should make it free of paint and materials that can impede the flow of electrical current. Rules adopted park is as if tapping something slowly and can be issued when the arc is an arc distance should be kept at a distance of 5.0mm to 6.0mm. While scraping method,, the electrodes in carek-carek on solid starting point as you scratch matches. When the rising arc of the distance to be maintained as described above.

situation where the rising arc between between the electrode tip and workpiece should stray from the path. Usually the sound emitted from the spray is uite uite stro stron n and and the size of the normal arc also may seem a little large. This happened probably due to its state Earth clip position is inaccurate.

- Position Welding - Type of metal to be welded - Type of  connection design e c ness o the metal

The electrode is functioning as a metal additive in the arc welding which is coated with a mixture of  a flux which comprises of some particular type and have different functions when welding work done.

Protective welding electrodes (SMAW) is a fusion of the electrode coated consumable (consumable), which consists consists of various various types depending on the type of metal core and the coating content of the electrodes. The process of coating of flux in two ways, namely namely how the extrusion extrusion (extrusion (extrusion)) and how to dunk (dipping).

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The electro electrode de is a core wire wire that is surrounde surrounded d by a type of flux. flux. The core core metal and the flux vary depending upon what type of application it is being used for. The flux around the core metal is used for many different reasons. reasons. One reason reason is to protect the molten metal metal from the atmospheri atmospheric c contaminates and gases that surround it. The second reason is that it helps to control control the current to flow thou the electrod electrode e to the work piece. The third is that it helps remove oxygen from the welded metal with deoxidize. These ma er a are use or vary ng app ca ons rom ra s ng e ens e s reng o the weld to de-oxidati de-oxidation. on. The core metal metal is also made of many different different metals metals depend upon the applicatio applications ns it is going to be used for. The electrdes have a numbering system on them that look something like this "E6011 "E6011". ". The "E" in the code code stands stands for the Elect Electrod rode. e. The "60" "60" in the code stands for for the tensile strength strength which which is a minimum minimum of 60,000psi. The "1" in the code stands for the position the electrode is to be used in, the one in this case stands stands for all welding welding positions. positions. The last number in the code "1" stands stands for the welding current either AC or DC.

Electrode coating mixture consisting of several materials depending on the features of IRRIIRRI -use -use electrodes. Among the materials are mixed in the electrode coating is serbok iron oxide oxide-titania -titania, titania, sodium silicate, potassium, asbestos, ferro ferro-manganese. -manganese. Coating of the electrodes is divided into three: ThinThin -coating (not coated) -coating MediumMedium-coating -coating -Coating -Coating thickness

Function Function is a coatin coatin on the electrodes electr electrodes: odes:: - Producing gas masks. - Generate ‘slag’ cap molding - Stabilizing the arc - Contains a mixture to use special features. Coating of the electrodes can be categorized into types: - Rutile - Cellulose - Iron filings

namely: - Soft Steel - Steel 'low alloy' - Stainless steel - Hardening surface - Nickel and nickel pancalogam - Aluminum and aluminum pancalogam - Copper and copper pancalogam

‘ ’ melting molding surface coating of the electrodes. The functions are: - Protect the moldings from the outside air during the cooling occurs. - float the dirt to the surface of the molten crater. - Control of molding so that uniform. - Slows down the rate of cooling to improve the properties of metals - Providing mechanical protection to the transfer of metal from the electrode into the base metal.