what is the main reason of cracks 2

[gordonmech]

we find some cracks on tapered zone of welding neck flanges during hydrotest, what is the reason of cracks, it seams that the during forging of flanges there was lamination, how can we find the exact reason?
Thank you

 

[BigInch]

Are we talking about weld zone cracks, or laminations?

Laminations are manufacturing defects.

Weld cracks are often the result of incorrect welding procedures, poor welding material selections, welding incompatiable thicknesses, or incorrect pre/post heat & cooling control.

 

[athomas236]

how long is string ??

 

[chicopee]

About posting a picture of the cracked welding neck flange.

 

[ndeguy]

Laminations are not associated with forgings but with plate material. In plates the cause of laminations is generally 3D inclusions or porosity in the original billet rolled out to become extended 2D defects, classically found at mid-wall.

Forging defects can arise from either the ingot production stage (shrinkage, inclusions, segregations and laps), from the forging operation itself (bursts and laps) or from heat treatment (hairline cracks). Thermal stress cracks may be caused by inadequate degassing, improper heat treatment or localised heating during grinding. Positive I.D. of the cause of detected indications is the remit of the metallurgical laboratory.

 

[adamuk]

You'd have to cut the forging out and have it looked at under the microscope (often this involves sectioning down then grinding, polishing and etching) to identify the root cause.

Cheers

Adam Potter
Axiom Engineering Associates Ltd

http://www.ax-ea.co.uk

Adam Potter MEng CEng MIMechE

http://www.ax-ea.co.uk