Welding Defects Causes And Remedies Pdf Nptel
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- What is Casting Defects – Types, Causes and Remedies?
- 7 Most Common Welding Defects, Causes and Remedies
- What is Welding Defects – Types, Causes and Remedies?
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.
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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.
Shrinkage defects: shrinkage cavity 3. Mold material defects: Cut and washes, swell, drops, metal penetration, rat tail 4. Pouring metal defects: Cold shut, misrun, slag inclusion 5. Metallurgical defects: Hot tears, hot spot. The defect caused due to misalignment of upper and lower part of the casting and misplacement of the core at parting line. It is the enlargement of the mold cavity because of the molten metal pressure, which results in localised or overall enlargement of the casting.
When gases entrapped on the surface of the casting due to solidifying metal, a rounded or oval cavity is formed called as blowholes. These defects are always present in the cope part of the mold. Drop defect occurs when there is cracking on the upper surface of the sand and sand pieces fall into the molten metal. Fluxing means addition of a substance in molten metal to remove impurities. After fluxing the impurities from the molten metal can be easily removed.
These casting defects appear as an uneven and rough surface of the casting. When the size of sand grains is larges, the molten fuses into the sand and solidifies giving us metal penetration defect. Because of this the molten metal penetrates in the molding sand and we get rough or uneven casting surface. They are very small holes of about 2 mm in size which appears on the surface of the casting.
This defect happens because of the dissolution of the hydrogen gases in the molten metal. When the molten metal is poured in the mold cavity and as it starts to solidify, the solubility of the hydrogen gas decreases and it starts escaping out the molten metal leaves behind small number of holes called as pinholes.
The formation of cavity in the casting due to volumetric contraction is called as shrinkage cavity. It is a type of surface defects and a line on the surface can be seen. When the molten metal enters into the mold from two gates and when these two streams of molten metal meet at a junction with low temperatures than they do not fuse with each other and solidifies creating a cold shut appear as line on the casting.
It looks like a crack with round edge. When the molten metal solidifies before completely filling the mold cavity and leaves a space in the mold called as misrun. This defect is caused when the molten metal containing slag particles is poured in the mold cavity and it gets solidifies.
The failure of casting in this case is looks like cracks and called as hot tears or hot cracking. Hot spot defects occur when an area on the casting cools more rapidly than the surrounding materials. Hot spot are areas on the casting which is harder than the surrounding area.
It is also called as hard spot. It is the holes created on the external surface or inside the casting. It occurs when loose sand washes into the mold cavity and fuses into the interior of the casting or rapid pouring of the molten metal.
It is an external defect in which there is a number of small cavities in close proximity present in the metal casting. It is an accidental and unwanted deformation in the casting that happens during or after solidification. Due to this defect, the dimension of the final product changes. This induces stresses in adjoining walls and result in warpage. A thin projection of metal, not considered as a part of casting is called as fins or fin.
It is usually occurs at the parting of the mold or core section. Here we have discussed about what is casting defects — types, causes and remedies to eliminate it. If you find any query regarding this post feel free to ask. Pankaj Mishra is a blogger by passion and Mechanical Engineer by profession. He has completed his B.
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What is Casting Defects – Types, Causes and Remedies?
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. Undercut 3. Spatter 4.
No manufacturing process is immune to defects. The same goes true with Welding. Welding defects are the irregularities that are formed due to the wrong welding process or due to inexperienced welders. Even if irregularities are very minimal but if the shape, size, and quality of the weld are way different than what is expected, it is also called welding defects. Some amount of weld defects are acceptable if that is under the tolerable limit and do not impact the product function and performance. You may also like to Read: Why Plastics are replacing metals.
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.
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7 Most Common Welding Defects, Causes and Remedies
Disclaimer: welderportal. When you purchase through links on our site, we may earn a small commission at no extra cost to you. Defects are common in any type of manufacturing, welding including. In the process, there can be deviations in the shape and size of the metal structure. It can be caused by the use of the incorrect welding process or wrong welding technique.
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What is Welding Defects – Types, Causes and Remedies?
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. Shrinkage defects: shrinkage cavity 3.
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