Joining of Metals & Non Metals: Welding Processes, Slides of Materials Processing

Download Joining of Metals & Non Metals: Welding Processes and more Slides Materials Processing in PDF only on Docsity! AAB 3013 Joining of Metals & Non Metals Course Outcomes (CO) CO1: Propose the right joining techniques and equipment for the particulars work to be carried out. (C5,PO3) CO2: Analyze the defects of the joining and welding using NDT techniques and other tools. (C4,PO4) CO3: Explore the requirement of national and international specifications, safety and standard for the joining of the pressure vessel, pipes and component. (C4,PO9) 2.2 Welding: Processes Welding Processes Arc Welding Gas Welding Resistance Energy beam Solid- state 2.3 Welding: Processes - Energy beam ❖ Energy beam welding methods, namely laser beam welding and electron beam welding, are relatively new processes that have become quite popular in high production applications. ❖ The two processes are quite similar, differing most notably in their source of power. ❖ Laser beam welding employs a highly focused laser beam, while electron beam welding is done in a vacuum and uses an electron beam. ❖ Both have a very high energy density, making deep weld penetration possible and minimizing the size of the weld area. Both processes are extremely fast, and are easily automated, making them highly productive. ❖ The primary disadvantages are their very high equipment costs (though these are decreasing) and a susceptibility to thermal cracking. Developments in this area include laser- hybrid welding, which uses principles from both laser beam welding and arc welding for even better weld properties, laser cladding, and x-ray welding. 2.4 Welding: Processes Solid State Welding ❖ Like the first welding process, forge welding, some modern welding methods do not involve the melting of the materials being joined. One of the most popular, ultrasonic welding, is used to connect thin sheets or wires made of metal or thermoplastic by vibrating them at high frequency and under high pressure. ➢The equipment and methods involved are similar to resistance welding, but instead of electric current, vibration provides energy input. ➢Welding metals with this process does not involve melting the materials; instead, the weld is formed by introducing mechanical vibrations horizontally under pressure. ➢When welding plastics, the materials should have similar melting temperatures, and the vibrations are introduced vertically. ➢Ultrasonic welding is commonly used for making electrical connections out of aluminum or copper, and it is also a very common polymer welding process. ❖ Another common process, explosion welding, involves the joining of materials by pushing them together under extremely high pressure. The energy from the impact plasticizes the materials, forming a weld, even though only a limited amount of heat is generated. The process is commonly used for welding dissimilar materials, including bonding aluminum to carbon steel in ship hulls and stainless steel or titanium to carbon steel in petrochemical pressure vessels. ❖ Other solid-state welding processes include friction welding (including friction stir welding and friction stir spot welding), magnetic pulse welding, co-extrusion welding, cold welding, diffusion bonding, exothermic welding, high frequency welding, hot pressure welding, induction welding, and roll bonding. ‘Pressure normal to faying surfaces Electrical Solid- Siato Welding Radiation Induction Resistance Flame Contact Pressure Deformation Radiation Definitions Designation + Welding Process CEW Coextrusion welding cw Cold welding DFW Diffusion welding ExXw Explosion welding FOW Forge welding FRW Friction welding FSw Friction stir welding HPW Hot pressure welding IW Induction welding PGW Pressure gas welding RSEW Resistance seam welding RSW Resistance spot welding ROW Roll welding USW Ultrasonic welding uw Upset welding 2.5 Welding: Geometry ❖ After welding, several distinct regions can be identified in the weld area. ❖ The weld itself is called the fusion zone – more specifically, it is where the filler metal was laid during the welding process. The properties of the fusion zone depend primarily on the filler metal used, and its compatibility with the base materials. It is surrounded by the heat-affected zone (HAZ), the area that had its microstructure and properties altered by the weld. These properties depend on the base material's behavior when subjected to heat. The metal in this area is often weaker than both the base material and the fusion zone and is also where residual stresses are found. The cross-section of a welded butt joint The weld or fusion zone The heat-affected zone (HAZ) The base material The base material 2.6 Welding: Quality of Welds Factors influence the strength of welds Welding method Amount and concentration of energy input Weldability of the base material Filler material Flux material Design of the joint Interactions between all these factors Quality of a weld Free of defects Acceptable levels of residual stresses Acceptable levels of residual distortion Have acceptable heat-affected zone (HAZ) properties ❖ To test the quality of a weld, either destructive or nondestructive testing methods are commonly used. 2.7 Welding: Types of Welding Defects Types of Welding Defects Cracks Distortio n Gas inclusions (porosity) Non- metallic inclusions Lack of fusion Incomplete penetration Lamellar tearing Under cutting Different Types of Welding Joints Different Types Of Welding Joints — i Travet GOOD WELD we Too Long Amperage MARGINAL WELD Too High Amperage Too Low aeiss A welding joint is a point or edge where two or more pieces of metal or plastic are joined together. They are formed by welding two or more workpieces (metal or plastic) according to a particular geometry. There are five types of joints referred to by the American Welding Society: butt, corner, edge, lap, and tee. These configurations may have various configurations at the joint where actual welding can occur. 1- Butt Joint The butt joint is obtained by butt together the two plates lying in the same Peceeadpret ina eed aesemen tioned pia caitettsed toy cistne Butt Joints - Edge P: ion & Weld T Petednenngeihictresstiet one hana atesiemincgteattnecaecallecst ees mm do not require beveling of edges whereas plates having a thickness [ I } [ |Z lI kK | between 5 to 12 mm, should be bevelled to form a single -V, single or Single Square Groove Single Bevel Groove Double Bevel Groove double-U, or J-groove. It is the simplest type of joint used to join metal or [ NZ I| jl x 1 | IZ } Hestepartisitegetiter Single-V Groove Double-V Groove ‘Single-I Groove [ K J XZ I Pv J The different weld types in butt welding are 1- Square Buttweld 2- Bevel groove weld 3- V-groove weld 4- J-groove weld 5- U-groove weld 6- Flare-V-groove weld 7- Flare-bevel-groove butt weld Butt Joint Edge Prepration Method es os pe <=] Straight Single V Double Vv Corner Joint 2- Corner Joint TYPICAL CORNER JOINTS The joint is obtained by joining the edges of two plates whose surfaces are at U tg | 1- Fillel weld Celia MRC la el Reese 2- Spot weld 3- Square-groove weld or butt weld 90° Lo each other. This joi One thing that is important to note about this type of weld is that you do it on the outside of the corner. is used for light and heavy thickness sheel metals. The different weld types in a corner joint are as follows 4- V-groove weld 5- Bevel-groove weld 6-U-groove weld 7-J-groove weld Laie slime CC og MUM eco 8- Tlare- V-groove weld 9- Edge weld a; L 5- Edge Joint The edge joint is obtained by joining two parallel plates. This joint is used economically for plates having a thickness of less than 6 mm. It is not suitable for severe loading subjected to tension and bending, This is generally used for Ed ge Joint (t WTS TUS TTR ) unimportant work and sheet metal work. The various weld types in this welding joint are a OTE et CL. ) naalanens {- Square-groove weld or butt weld 2- Bevel-groove weld 3- V-groove weld 4-J-groove weld 5- U-groove weld 6- Edge-flange weld T-Comer-flange weld Filler Rod Consumption During Welding Ua UCT  Good and Bad Stick Welds Example of Good and Bad Stick Welds See AE 1k death EA Good rt Cage teeta pe OO: LO Weld : GOOD WELD Travel Too Fast - = aaa Travel aE Too Slbw = Arc Too Short Arc Too Long Amperage Too High Amperage Too Low 2.9 Welding: Heat Affected Zone (HAZ) ❖The blue area results from oxidation at a corresponding temperature of 316°C. ❖This is an accurate way to identify temperature but does not represent the HAZ width. The HAZ is the narrow area that immediately surrounds the welded base metal. 2.9 Welding: Heat Affected Zone (HAZ) ❖ The heat-affected zone (HAZ) is a ring surrounding the weld in which the temperature of the welding process, combined with the stresses of uneven heating and cooling, alter the heat- treatment properties of the alloy. ❖ The effects of welding on the material surrounding the weld can be detrimental – depending on the materials used and the heat input of the welding process used, the HAZ can be of varying size and strength. ❖ The thermal diffusivity of the base material plays a large role – if the diffusivity is high, the material cooling rate is high and the HAZ is relatively small. Conversely, a low diffusivity leads to slower cooling and a larger HAZ. ❖ The amount of heat injected by the welding process plays an important role as well, as processes like oxyacetylene welding have an unconcentrated heat input and increase the size of the HAZ. ❖ Processes like laser beam welding give a highly concentrated, limited amount of heat, resulting in a small HAZ. ❖ Arc welding falls between these two extremes, with the individual processes varying somewhat in heat input. ❖ To calculate the heat input for arc welding procedures, the following formula can be used: where Q = heat input (kJ/mm), V = voltage (V), I = current (A), and S= welding speed (mm/min). ❖ The efficiency is dependent on the welding process used, with shielded metal arc welding having a value of 0.75, gas metal arc welding and submerged arc welding, 0.9, and gas tungsten arc welding, 0.8. ❖ Methods of alleviating the stresses and brittleness created in the HAZ include stress relieving and tempering. 2.10 Welding: Unusual conditions ❖ While many welding applications are done in controlled environments such as factories and repair shops, some welding processes are commonly used in a wide variety of conditions, such as open air, under water, and vacuums (such as space). ❖ In open-air applications, such as construction and outdoors repair, shielded metal arc welding is the most common process. ❖ Processes that employ inert gases to protect the weld cannot be readily used in such situations, because unpredictable atmospheric movements can result in a faulty weld. ❖ Shielded metal arc welding is also often used in underwater welding in the construction and repair of ships, offshore platforms, and pipelines, but others, such as flux cored arc welding and gas tungsten arc welding, are also common. ❖ Welding in space is also possible – it was first attempted in 1969 by Russian (Soyuz 6 mission). Advances in these areas may be useful for future endeavors like the construction of the International Space Station, which could rely on welding for joining in space the parts that were manufactured on Earth.