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Study on Crack of Cylindrical Surface during the Upsetting of Heavy Forging

Author: WangZiLiang
Tutor: RenYunLai
School: Yanshan University
Course: Materials Processing Engineering
Keywords: Forging Large forgings Upsetting Drum coefficients Hole expansion ratio Side surface cracking
CLC: TG316.192
Type: Master's thesis
Year: 2007
Downloads: 263
Quote: 5
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Abstract


The rapid development of modern metal processing industry , heavy machinery manufacturing industry to provide quality forgings . Large forgings and forged from ingot . Ingot inevitable presence of segregation, porosity , microcrack tissue defects . The ingot is the greater , the more serious defects . In order to obtain high quality forgings by forging eliminate these defects . Upsetting is an extremely important step in the manufacturing process of large forgings , its main purpose is to increase the forging ratio, nip internal cavity defects , to improve material performance . Upsetting process , due to the presence of friction , it is difficult deformation zone coarse grains , the core section tensile stress defects , deformation, uneven side surface cracking . Which side surface cracking is the most common , and often leads to the discarding of large forgings . Cracks in the plastic deformation process , the development eventually leading to macroscopic fracture phenomenon is a complex process influenced by many factors of the metal organizational structure , stress state , the rate of deformation , but the ultimate cause or metal internal inclusions and second phase particles separation of defects at the interface to form a hole . The hole expansion under certain external conditions , and subsequent polymerization or connect eventually form a macroscopic crack . Departure from the internal mechanism of plastic material cracks , the critical hole expansion ratio theory to actual upsetting process to solve the decision problem of cracking of the side surface of the upsetting process . Crack nucleation and expansion is due to non-uniform deformation induced describe uneven deformation in the upsetting process defined upsetting drum coefficient , through numerical simulation analysis , the coefficient drum upsetting the relationship between the circumferential stress and axial stress , and eventually established a one-to-one relationship between the drum coefficients and characterization of materials stress triaxiality of the stress state . Simplified during the deformation process of solving the hole expansion ratio , so that the application in the actual production process critical void growth the upsetting side surface cracking than the theoretical determination through the establishment of the correspondence between the drum coefficient of stress triaxiality becomes possible.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metal pressure processing > Forging, forging and blacksmith > Forging process > Blacksmith operating a general method > Forging defects and their prevention
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