Forging Defects

April 2, 2018 | Author: Ashraf Ali | Category: Forging, Fracture, Metals, Lubricant, Industrial Processes


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Forging DefectsS. Arvind Joshua Jaydev (20082203) Defects in Forging may Arise from: •  Inherent Defects while forging •  Faulty cuts in Forging Operations •  Improper Heating and Cooling   Dents 8.  Laps/Folds 3.Types of Defects in Forging 1.  Flow-through 6.  Pitting 4.  Distributed Metal Defects 7.  Cracks 2.  Coarse Grain Wrinkle 5.  Void at Base of Rib 10.  Underfilling 9. Push-through of Web under Rib . •  External cracks are most dangerous •  Cracks may appear at flash (if flash is too thin) •  Internal cracks may develop during Upsetting . etc.1. Cracks •  Excessive working of a surface at too low a temperature leads to cracks •  Cracks may nucleate due to sulphur inclusions. The small inclusion appears to have initiated cleavage fracture. .Inclusions leading to cracking Cavity in the centre of a cleavage facet. “Upsetting” Forging . Flash . Combating cracks in Forging •  Forging at increased temperature •  Stress relieving before cutting off flash •  Hot-cutting of Flash •  Use concave die while upsetting. . •  May be due to Too small die radius. excessive chilling of high friction .2. Laps/Folds •  Also called “Fold-shut” •  Occurs when two surfaces of a metal folds against each other without welding completely •  Metal may flow past a die cavity that has already been filled. Example of Folding during Forging . Pitting .3. Pitting •  Pitting occurs because of incomplete cleaning of Die •  Die and workpiece should be free from scale while forging . 4. •  These wrinkles fold into laps during forging. . Coarse grain Wrinkle •  Wrinkling occurs during forging because the Billets contains coarse grains. 5. Flow-through . •  Maybe avoided by increasing temp. of stock •  Ensure lubricants are not trapped .Also… •  Flow through may occur in cases where metal flows past the die recesses after filling. •  Die impressions are hence not completely filled. 6. Distributed Metal Defects •  Loose oxides minimized die-slug contact •  Avoid too much lubricant . Dents .7. .Dents are caused by •  Improper positioning of stock on die •  Throwing around the forging while it is still hot. 8. Underfilling . Underfilling •  Metal does not fill the recesses of the die completely •  Because of loose scale and lubricant residue that accumulates in deep recesses of the die . this type of defect can be prevented . Rib and Web defects •  A "peeling" lap forms in an aluminum rib-web forging as the corner of the die forces surface material ahead of the contact region.9. With a redesign of the upper die or preform. Dieter •  http://www. E.References •  “Mechanical Metallurgy”. G.com •  Google Images .forgemag.
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