The Welding Manufacturing Process Engineering Essay

The Welding Manufacturing Process Engineering EssayWelding is an attractive topic to be rese obeisancehed because it is used in the majority of industrial dramaticss and manufacturing routinees.The next exercise shows that the safeguard metallic element run conjoin action represents ab erupt 42% from the whole weld processes.The conjoin theory depends on the joining amongst 2 parts whether metals like aluminium, vane, copper, or cast iron or plastics like polypropylene.Welding specially is distinguishable from the normal joining where the aim of weld is to obtain a strong joint amid deuce or more parts to be as a single part and to minimize number of parts. For example, the robotic joints used to assemble pipe lines is limited to specific assesss of pressure and temperature and when those values put crossship good dealal those limits, the weld takes place in the assembly processThe main image of fusion weld is the partial run awaying and fusion of the joint betwe en two members and a filler metals may be used.In the venting join process, the screw up required is obtained from galvanic energy. An curtain call is produced between the tip off of the electrode and release segment to be welded, by development an AC or a DC power supply. guard metal venting conjoin (SMAW) is one of the oldest, simplest, and most various(a) joining processes. rough 50% of all industrial and maintenance weld at present is performed by this process.The electric arc is provided by touching the tip of a cover electrode with the die flip or the sample and moving back it quickly to enough distance to maintain the arc. The heat generated commingles a piece of the electrode tip, its coating and the base metal in the warm arc area and this mixture forms the weld when it solidifies.1.2 Aims objectivesThe aim or goal of the inquiry is a huge statement of the problem which I intend to solve and what I intend to achieve.Objectivesset the realistic targets to achieve during the research and I should use beat expend in project management.Objectives are derived from the aim, but are more specific and measurable.AimsInvestigate/research solutions to reduce cracks occurring in ascorbic acid trade names during shield metal arc weld processObjectivesInvestigate/research shield metal arc welding process in one C copy mark metalsInvestigate/research parameters alter shield metal arc welding process in carbon steel metalsInvestigate/research reasons of cracks in shield metal arc welding process in carbon steel metals and order of magnitudes to reduce them.Literature reviewMany researches were done to investigate welding processes from umpteen points of views and in the next pages these examples impart be shown belowFirst example-In the research done by G. B. JANG, H. K. KIM AND S. S. KANG, It was discovered that in the steel bridge manufacturing, there are umteen difference of opinions in dimensions caused by weld deformation oft en happen because multi-pass welding is used mainly to join thick plates. It repeatedly produced that root openings are out of tolerances at place of butt joints.Second example-In the research done by G. B. JANG, H. K. KIM AND S. S. KANG, It was discovered that there is a new innovative method for estimating the actual stilling rate in a welded section is existed. This method is depended on applying a ladinging component part to the Rosenthal* analytical solutions for thick and thin plates. The factor is calculated from the heat affected govern (HAZ) width obtained from carved sections and reflects the actual response of the plate to the heat feed condition. The formulations used in the literature of this research are depended on the assumption of thin plate and thick plate conditions while most actual conditions non real somewhere between the two extremes. Limited experimental measurements of cooling rate performed by instrumented welding presented good agreement with predict ed values. The meansl was further used to get the peak temperature profile across the HAZ.2.1 MethodologyAs shown in the literature review, the previous two researches concentrated on the problems related to weld deformation and cooling rate.In this research the study of shield metal arc welding volition be concentrated on the parameters affecting cracks appearance and the methods used and available to reduce and eliminate them.To achieve objectives, first, a study will be done to previous researches in the same field through the internet and reading different casefuls of books to study theMethodology block DiagramSMAW process in carbon steels.the next step is to focus on cracks appeared and how to reduce them.Also Libraries, internet, will be used as a statement of method.The internet usage will give powerful to the research to get information now because it is fastest, cheapest, and most widely in getting information and information that need in any section of science. Diff erent search engine will be used aswww.google.comwww.yahoo.comIn addition, the forums will be used to discuss results with other engineers to nurse learning from their experts.Libraries from reading books you can know the theoretical part and the analysis of the welding parameters.In this study, there is no practical work but if there was a similar one in the future it mustiness take into considerations the ensure that the final product must be safe to the environment by taking into consideration to prevent any prejudicial fumes.Conclusion-After this brief proposal it can be said that this project will concentrate on three main categories-Shield metal arc welding process in carbon steel metalsParameters affecting shield metal arc welding process in carbon steel metalsReasons of cracks in shield metal arc welding process in carbon steel metals and methods to reduce them.Also, it can be guessed that the weakness of this proposal is not mentioning some(prenominal) problems related to this process and a try will be done overcoming this point in the next stages of the project.This proposal takes its strength from the anatomy and spread of SMAW process in the industrial field as shown in the beginning of the proposal.Time TableCompleted proposal9TH of OctoberInitial project proposal word3rd 11th of NovemberStart collecting information and data1st December-6thStart following chapter25th DecemberPrepare slideshow1st January-5thComplete interim report18th of JanuaryWork on following chapterstenth of FebruaryProject should almost be complete10th of marchPrepare for presentation7th of mayChapter 3dismissal welding conceptArc welding is a process of the fusion welding processes which contains-1 Arc welding processes (non consumable electrodes) triggerman tungsten arc weldingPlasma arc weldingAtomic hydrogen welding2 Arc welding processes (consumable electrodes)Shielded metal arc weldingSubmerged arc weldingGas metal arc weldingFlux cored arc weldingElectro g as weldingElectro slag welding3 Electron beam welding4 Laser beam weldingThe main concept of fusion welding is the partial melting and fusion of the joint between two members and a filler metals may be used.In the arc welding process, the heat required is obtained from electrical energy. An arc is produced between the tip of the electrode and work piece to be welded, by using an AC or a DC power supply.Shield metal arc welding (SMAW) is one of the oldest, simplest, and most versatile joining processes. About 50% of all industrial and maintenance welding mensesly is performed by this process.The electric arc is generated by touching the head or the tip of a coat electrode against the work piece and withdrawing it quickly to a distance fit to preserve the arc. The heat start generating from the electrode tip, its coating and the base metal in the immediate arc area and this mixture forms the weld when it solidifies.3.2 Classification of arc weldingThe arc welding classified into many types used in the industrial field each one have advantages and defects different from the other type, So that the user select the required type according to the requirements and the economy aspects. In the below figure we show for the classification of arc welding which appear in the industrial (3.1)Arc weldingPAWESWMIGTIGSAWSMAWCarbon arc welding kind 3.1 arc welding classificationChart keySMAW shield metal arc weldingSAW submerged arc weldingTIG tungsten sulky gas arc weldingMIG metal inert gas weldingPAW plasma arc weldingESW electro slag weldingThe above map list for the types of the arc welding which used in the industrial fields.Advantages of arc weldingThere are some characteristic for the arc welding sooner than the another methods to joining metals which it represent the advantages of the arc welding listed as below1- Strong and tight joining2- Cost effectiveness ( arc welding have low capital and running costs)3- Simplicity of welded structure designFigure 3.2 arc welding usage in the industry(http//64.78.42.182/sweethaven/BldgConst/Welding/ littleonmain.asp?lesNum=4modNum=1)3.2.1 Principals and definitionShield metal arc welding (SMAW) consider as process in which coalescence of metal produced by the heat which generated from the electric arc that it maintained between the tip of the consumable electrode and the base metal in the welding region. The next figures show the circuit used in the shield metal arc weldingFigure 3.2 SMAW system, http//www.millerwelds.com/pdf/guidelines_smaw.pdfFigure description the above figure illustrate the main parameters used in the SMAW processPower supplyThe shield arc welding power source provides constant stream (cc) it may be alternative current (Ac) or direct current (DC) depending on the electrode being used, but the best welding usually used the direct current (DC) as power supply for the circuit.The get along of power required to welding process calculated from the telling(P= IV) Where I represent t he current V represent the voltagesIn the selection process for the power supply we notice that the voltage equal to constant value so that the current is the main parameters in the selection process which discussed in the next section3.2.2 Current settingThe amount of current needed to melt the work piece and the electrode tip depends on several factors as1- Type and nonplus of the joint2- Work piece type and its thickness3- Electrode type and its diamIn facts most of welder select the current depending on the diameter of the used electrode which it measured from the inner section without the coated diameter as showing in the below figureNoCodeUsage and properties16010all welding positionsresult in deep sagacity weldwork on rusted, dirty, or painted metals26011used with ac and dc currentsall welding positionsresult in deep penetration weldwork on rusted, dirty, or painted metals36013used with ac and dc currentsresult in medium penetration weldgive superior weld talus appearanc e47018low hydrogen electrodecan be used with dc or accan result in welds of x-ray fictional character with medium penetrationmust be kept dry180LV Redused in AC/DC straight or backtrack polarityall positions with low voltage machines2275 higher(prenominal) yield and elastic strength324 AC/DCac/dc all position electrodesjoin dissimilar metals4309 L AC/DChigh corrosion resistancehigh strengthall position electrodesTable 3.3 Examples of electrodes usage and propertiesA prefatory guide of arc welding electrodes by Bruce Bauerleinhttp//www.metalwebnews.com/howto/weldrod.htmlhttp//www.weldershop.info/282/types-of-welding-electrodes/1. ElectrodeThe electrode used in (SMAW) process consist from metal rod coated in metal mixture called flux which gives off gases as it decomposes to prevent weld contamination , introduces deoxidizer to purify the weld , causes weld- protection slag and to provides devalueelements to improve the property of weld. There are three types from the electrode used in (SMAW) process which discussed below.Fast fill electrode this type from electrode is designed to melt very fast so that bureau the welding travel rapidly should be maximized. This type used when we weld in the normal case in vertical welding so we can weld with high speed so we use this electrode type.Fast freeze electrode this type from electrode designed to solidify quickly making welding in different positions by preventing the weld pool from shifting.Intermediates electrodes the commonly used type and it intermediate in two case melting and in freezing but if we weld with high speed with using this type we get poor fiber so that this type is not suitable in case of high speed.The American welding nightclub established system that used to assign electrodes by using four or five digital number. Covered electrodes made of mild steel or low alloy steel carry the symbol of (E) followed by special numbers. The first two or three digits of the number of the electrode speci fy the tensile strength of the weld metal. The mid digits generally identify the welding positions allowed with the electrode normally using the values 1 (normally fast-freeze electrodes, implying all position welding) and 2 (normally fast-fill electrodes, implying horizontal welding only). The welding current and the type of the electrode casing are specified by the last two digits together.Example for electrode serial numberE7018E indicates electrode70 indicates 70,000 psi tensile strength1 indicates use for welding in all positions8 indicates low hydrogen2. Cables there are two billets work cable which connected the base metal and the electrode cable which connected to the electrode one of them represent positive and the other represent the negative side this according to the polarity of the welding process3.2.3. Welding trouble shootingThis section discuss to the trouble shooting may faced it during the welding speed as1-Porosity small cavities or holes resulting from gas pocke ts in weld metal.Fig 3.4 porosity of weldingwww.miller.com.pdfThe porosity in welding it may be caused by the dirty on work piece and the corrective action to face it by Re give-up the ghost all grease, oil, moisture, rust, paint, coatings, slag, and dirt from work surface before welding.2-Excessive Spatter scattering of molten metal particles that cool to solid form near weld bead as shown in the below figure.Fig 3.5 excessive ptyalisewww.miller.com.pdfThe main causes to excessive spatter is the current too high for electrode and it avoid by decrease current or select larger electrode.3- Distortion contraction of weld metal during welding that forces base metal to move.Fig 3.6 Distortionwww.miller.com.pdfDistortion in the welding appear as result to excessive heat input. And there is many ways to solve this problem as1-Use restraint (clamp) to hold base metal in position2-Make tack welds along joint before starting welding operation.3-Select lower amperage for electrode.4-Increase travel speed5-Lack of Penetration shallow fusion between weld metal and base metal.Fig 3.7 lack of penetrationwww.miller.com.pdfThe lack of penetration appears as result for many causes as showing belowPossible causesCorrective actionImproper joint preparationMaterial too thick. occasion preparation and design must provide access to bottom of groove.Improper weld technique.1-Keep arc on leading edge of weld puddle.2-Reduce travel speed. lacking(p) heat input.Increase amperage. Select larger electrode and increase amperageTable 3.8 causes of penetration lackAdvantages of shield metal arc weldingThe shield arc welding have main further that represent the advantages as below1-Strong and tight joining rather than the other methods2-Cost effectiveness (have low capital and running cost)3- The arc welding Simplicity of welded structures design4- May be mechanized and automated or manual in some dutyDisadvantages of arc weldingThe using of the shield metal arc welding lead to some defect s as1- Internal stresses, distortion and change for the microstructure in the weld region2- Have harmful effects as radiation and fumes3.3 Application of the shield arc weldingThe arc welding it can be used in many applications as1-Buildings and bridges structures2-Automotive, ship and aircraft constructions3-Pipe lines4-Tanks and vessels (2.2)3.4 PolarityTo introduce what the polarity means and the different type of the polarity, first of all the project will show what is the difference between AC and DC?3.4.1 AC and DC currentWhat is the AC current?It means alternating current. In this current the electric charge flow periodically sprains oversight. The electric charge in this case will move for instance backward then it will reverse the direction again to move forward, then backward then forward over and over again.The waveform for alternating current is a sine wave. But sometimes in certain applications the waveform differs like square wave or triangular wave. acFileTypes of current by Zureks.svgtriangleRMS_fig_1Figure 3.9 current and wave typesDc currentWhat is the DC current?It means direct current because the electric charge in direct current moves in a constant direction, and that is the difference between DC and AC. The DC could be produced by such sources like thermocouples, batteries and solar cells.We can use a rectifier which is a current-switching ar run forment to obtain direct current from an alternating current. The concept of rectifier is containing electromechanical elements or electronic elements which allow current to flow only in one direction.FileCurrent correction diagram.svgFigure 3.10 current rectification diagrams3.4.2 AC and DC welding machinesThe welder or welding machine is the power source that we used in arc welding. There are three underlying types of weldingmachines used now which are rectifiers, motor- generators and transformersMotor generator welding machines (direct current welding machines)The motor generator could be powered by diesel, electrical or gasoline motor. We can use the gasoline and diesel motors in places where the electricity is not available or hard to reach it like deserts. With these machines we could generate either direct or alternating current. There are new and old machine types of these machines, the older type require reversing the cable connections in order to change the polarity. But in the new machines you can change the polarity from welding in the direct current mode to alternating current mode by turning a switch.The advantages of a (dc) welding generatorThe main advantage of a direct-current (dc) welding generator is that you can weld with either reverse or straight polarity.Almost we can weld all ferrous and non-ferrous metals.We can use DC in practically all welding operations so we can consider that DC is most universal in application.The output of generators like rectifier and transformer a sets is not affected by normal variations in power line voltage.Diesel dr iven generators form self-contained units.Disadvantages of a (dc) welding generatorThe initial cost is highThe machine operation is clamantThe maintenance cost is highAC transformers welding machinesThe static-transformer type is the arc welding machines that we used in alternating current. http//www.tpub.com/content/construction/14250/img/14250_134_2.jpgThe advantages of these types ofmachines are lightest, smallest and least(prenominal) expensive welders made. We can use 200, 300, and 400 ampere ratings for manual operation in industrialapplications. But in light industrial, job/shop and store welding we could use machines with a 150-ampere rating. These types of transforms equipped with arc- stabilizing capacitors.The advantage of a (AC) transformer welding machineThe main advantage of (AC) transformer welding machine is the freedom from arc blow. The arc blow causes the arc to wander while you are using large coated electrodes or welding in corners on heavy metal. The arc blo w often occurs when welding with direct current machines.PolarityWhat is the polarity?Figure 3.12 Straight and reverse polarity in electric welding.Polarity is the direction of the current flow in a circuit. There are two types of polarity reverse polarity and straight polarity. In the straight polarity the work piece is positive and the electrode is negative. The electrons move from the electrode to the work piece. In the reverse polarity the work- piece negative and the electrode is positive. The electrons move from the work piece to the electrode ac and dc current was briefly covered. http//www.tpub.com/content/construction/14250/img/14250_141_2.jpgThe effect of polarityThe polarity affects the amount of heat which is going to the base metal. You can direct the amount of heat to where it is needed as per the application you working in by changing the polarity. If you want to direct the majority of heat toward the work piece, you must use straight polarity. That type of polarity b eing used in some welding situations when it is desirable to have more heat on the work piece because of its size to melt the base metal than the electrode. We can use straight polarity for all mild-steel, bare, or lightly coated electrodes. If you want to concentrate the heat on the electrode, you can use reverse polarity because in this type less heat is concentrated at the work piece which allow filler metal to cool faster, giving it greater holding power because of this reverse polarity is being used when you are making vertical and overhead welds. Reverse polarity could be used in the welding of nonferrous metals such as bronze, aluminum and nickel.3.5 Heat Affected Zone3.5.1 Heat affected zone definition.The heat affected zone (HAZ) represented by the area of base material subjected to the high heat in order to achieve the welding process. The area which subjected to change in its microstructure and mechanical properties. SMAW process give a highly heat concentration in specif ied region called (fusion zone), produced in the region of heat affected zone. To calculated the amount of heat in the HAZ the following formula used.Q =60 VI / 1000SWhere Q = heat input (kj/mm), V = voltage (V), I = current (A), and S= welding speed (mm/ min). (2.10)The molten occur in the fusion region not in the heat affected zone. So that the HAZ heated to a high enough temperature for sufficient period that grain growth occurred. Heat affected zone is that location of the base metal which in it the mechanical properties and the microstructure have been affected by the heat of welding process.The heat affected zone is subjected to a complex thermic cycle (sudden heating followed by rapid cooling) in which all temperatures from the melting range of the metal down to much lower temperatures are involved and HAZ therefore consists of a series of graded structures ringing the weld bead. HAZ usually contains a variety of microstructures different from the remaining part from the base metal.The width of HAZ varies according to the welding process and technique in arc welds it extends only a few mm from the fusion boundary,The HAZ in most metal welding process of normal structure welded in one run with coated electrodes that to classify it to four basic region.3.6 Classification and DesignationThe classification of electrodes is done by one of the three following categoriesimages1 Strength of the deposited weld metal2 Current (ac or dc)Figure 3.13 Shield metal arc welding electrodes3 Types of coatingThe identification of electrodes is by numbers and letters as shown in the next table. Typical coated electrode dimensions are in the range of 150 to 460 mm (6 to 18 in.) in length, and 1.5 to 8 mm (1/16 to 5/16) in diameter.Specifications for electrodes and filler metals (including dimensional tolerances, quality control procedures, and processes) are published by the American welding society (AWS) and the American national standards institute (ANSI). Some specif ications appear in the aerospace materials specifications (AMS) by the society of automotive engineers (SAE). Electrodes are sold by weight and are available in a wide variety of sizes and specifications.3.7 Electrodes types and choicesWhen the choice of a suitable electrode is needed, many considerations are taken such as1 Quality of weld2 Penetration3 Used current whether AC or DC4 Crack resistantCHAPTER 4Defects appears in carbon steel weldingCarbon steelCarbon steel which it called also the plain carbon steel or the Mild Steel .It does also mean the steel where the main alloying element is carbon. When the carbon steel is specified minimum for copper does not exceed 0.40 portion and when the maximum content is specified for one of the following elements does not surpass the percentages known (manganese 1.65, silicon 0.60 and copper 0.60).The term carbon steel could also be used in position of steel which is actually not stainless steel, so the uses of carbon steel may conta in alloy steels.The low carbon steel has some properties similar to the properties of iron. As the content of the carbon going up, the metal becomes with some advantages such as harder and stronger and the disadvantages are less ductile and very hard or difficult to weld. Higher carbon steel usually has the lower the melting point and lower temperature resistance. Carbon steel content effects in yield strength of steel because carbon atoms are fit into the interstitial crystal lattice the places of the body-centered cubic (BCC) collections of the iron atoms. The spaces in carbon steel reduce the mobility of dislocations. To get dislocations to move, a high sufficient stress level should be applied to imbalances for the dislocations to separate them. All this happen because the spaces or the places of the carbon atoms cause in some of the iron BCC lattice cells to deform.Carbon steel is steels whose alloying elements do not exceed the following limitsElementMax weight %C1.00Cu0.60Mn1 .65P0.40Si0.60S0.054.2 Carbon steel properties and classificationsCarbon steels could be specified by chemical compositions, mechanical properties and thermal treatments.The following table shows the typical properties of steels with room temperature in (25C). The wide ranges of final the tensile strength, yield strength, and hardness are mostly due to the different between the heat treatment conditions. The different between the heat treatment conditions comes from the wide range of the the tensile strength, yield strength and hardness.PropertiesCarbon SteelsAlloy SteelsStainless Steels cats-paw SteelsDensity (1000 kg/m3)7.857.857.75-8.17.72-8.0Elastic Modulus (GPa)190-210190-210190-210190-210Poissons Ratio0.27-0.30.27-0.30.27-0.30.27-0.3Thermal Expansion (10-6/K)11-16.69.0-159.0-20.79.4-15.1Melting Point (C)1371-1454Thermal Conductivity (W/m-K)24.3-65.226-48.611.2-36.719.9-48.3Specific Heat (J/kg-K)450-2081452-1499420-500Electrical Resistivity (10-9m)130-1250210-125175.7-1020 flex ible Strength (MPa)276-1882758-1882515-827640-2000Yield Strength (MPa)186-758366-1793207-552380-440Percent Elongation (%)10-324-3112-405-25Hardness (Brinell 3000kg)86-388149-627137-595210-620www.efunda.comThe following groups show the subdivided of the plain carbon steelLowMediumHigh actually highLowThe low carbon steel has another name which is frequently called mild steels. Low carbon steel has less than 0.30 percent carbon and its one of the most commonly used. They machine and weld nicely and are more ductile than higher-carbon steels.MediumThe percentage of medium carbon steel is between 0.30 to 0.45 percent. When the carbon increases thats mean increasing in hardness and tensile strength and decreasing in ductility and more difficult machining.HighThe high carbon steel contains carbon which starts from 0.45 to 0.75 percent of carbon. These steels can be challenging to weld. Preheating or the post heating (which is useful to control the cooling rate). Heating during the welding process become very important or necessary to produce acceptable welds and to control the mechanical properties of the steel after welding.Very HighWith more than 1.50 percent of carbon content in very high carbon steel