File Name: welding defects causes and remedies nptel.zip
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Causes and cures of common welding troubles Porous welds why? Short arc, with the exception of low hydrogen and stainless. Insufficient puddling time. Impaired base metal. Poor electrodes What to do? Check impurities in base metal. Allow sufficient puddling time for gases to escape. Use proper current. Weave your weld to eliminate. Use proper electrodes for job. Hold longer arc. Causes and cures of common welding troubles Poor penetration why? Speed too fast..
Electrodes too large. Current too low. Faulty preparation. What to do? Use enough current to get desired penetration — weld slowly. Calculate electrode penetration properly. Select electrode according to welding groove size. Leave proper free space at the bottom of weld. Causes and cures of common welding troubles Warping why? Shrinkage of weld metal. Faulty clamping of parts. Over heating at joint. Peen joint edges before welding. Weld rapidly. Avoid excessive space between parts.
Clamp parts properly; back up to cool. Adopt a welding procedure. Use high — speed, moderate penetration electrodes. Faulty electrode manipulation 2. Faulty electrode usage. Current too high. Use uniform weave in butt welding. Avoid using an overly large electrode. Avoid excessive weaving. Use moderate current; weld slowly. Hold electrode at a safe distance from vertical plane in making horizontal fillet welds.
Causes and cures of common welding troubles Fig. Causes and cures of common welding troubles Distortion why? Uneven heat 2. Improper sequence. Deposited metal shrinks. Tack or clamp parts properly. Form parts before welding. Dispose of rolling or forming strains before welding. Distribute welding to prevent uneven heating. Examine structure and develop a sequence.
Causes and cures of common welding troubles Distortion of parts after welding Fig. Causes and cures of common welding troubles Cracked welds why? Wrong electrode. Weld and part sizes unbalanced. Faulty welds. Rigid joints. Design structure and welding procedure to eliminate rigid joints. Heat parts before welding. Avoid weld in string beads. Keep ends free to move as long as possible. Make sound welds of good fusion. Adjust weld size to parts size.
Allow joints a proper and uniform free space. Work with as low an amperage as possible Cracks caused by thermal stresses Fig. Causes and cures of common welding troubles Poor appearance why? Faulty appearance 2. Over hang. Improper use of electrodes. Wrong arc and current voltage.
What is weld decay? Weld decay is a form of intergranular corrosion, usually of stainless steels or certain nickel-base alloys, that occurs as the result of sensitization in the heat-affected zone during the welding operation. The corrosive attack is restricted to the heat affected zone HAZ. Positive identification of this type of corrosion usually requires microstructure examination under a microscopy although sometimes it is possible to visually recognize weld decay if parallel lines are already formed in the heat affected zone along the weld see photo below. Mechanisms of Weld Decay.
It is an unwanted irregularities that appear in the casting during metal casting process. There is various reason or sources which is responsible for the defects in the cast metal. Here in this section we will discuss all the major types of casting defects. Some of the defects produced may be neglected or tolerated and some are not acceptable, it must be eliminated for better functioning of the parts. Gas Porosity: Blowholes, open holes, pinholes 2.
Injection Molding Machine 1. Foxconn P4mp7ma Rs2 Drivers Windows 7. Molding Operation. Cold cracking occurs when residual stresses reduce the strength of the base material which can lead to catastrophic failure. Cold cracking is limited to steels and is commonly associated with the development of martensite as the weld area cools.
Elastic and plastic deformation. Concept of strain hardening. Hot and cold working processes -rolling, forging, extrusion, swaging, wire and tube drawing. Machines and equipment for the processes. Parameters and force calculations. Test methods for formability. Forming processes like bending, cup drawing, coining, embossing, etc.
In Mechanical Engineering Welding is one of the most important Metal joining process. As we know that in Casting we some defects are always there and similarly in welding defects are there. Welding defects is very common problem but need to solve it because it lead to failure to the material. Download Now Rhinoceros 5. Rhinoceros 5 Portable is a helpful, free gpl Windows program, belonging to the category Development software with subcategory Development editors and has been created by WS3. Rhinoceros 5.
Welding Defects can be defined as the irregularities formed in the given weld metal due to wrong welding process or incorrect welding patterns, etc. The defect may differ from the desired weld bead shape, size, and intended quality. Welding defects may occur either outside or inside the weld metal. Some of the defects may be allowed if the defects are under permissible limits but other defects such as cracks are never accepted. Weld Crack 2.
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rnasystemsbiology.org Welding Defects Weld defect may be in the form of variations from the intended weld bead shape, size and from the weld pool and may cause inclusion. Slag inclusion can be.Reply