Irregularities during the process of Extrusion. These are mainly due to Non uniform flow and stress distribution

2. Presentation on:
EXTRUSION DEFECTS
Presented by:
Nishat Riaz
MME-13-27
IAM,BZU,MULTAN

3. Extrusion Defects:
• Irregularities during the process of Extrusion
• These are mainly due to Non uniform flow and stress distribution
• Number of defects depends upon:
 Wall friction
 Wall temperature

4. Types of Extrusion defects:
• Surface Cracking
• Internal Cracking
• Piping Defect

5. Surface Cracking:
Surface cracks are developed due to
• High extrusion temperature
• High ram speed
• High Friction

6. • It occurs at High temperature such as Hot hardness
• Can also occur at low temperature
• These cracks are intergranular

7. Internal Cracking:
• Cracks are developed in the center of extruded material
• This is also named as
 Center Cracking
 Center Burst
 Chevron Cracking
 Arrow head Cracking
• These are hard to detect in the material

8. • It occurs due to difference in velocity and tensile stresses in center of
the material
• These can be prevented by using appropriate
 die angle
 Friction
 Extrusion Ratio

9. Piping Defect:
• It occurs during hot extrusion due to presence of impurities and
oxides
• It is also known as:
 Tail pipe
 Fish Tailing
• Propagates as Funnel Shaped Void.

10. • Metal in contact with walls cools down rapidly as compared to center
part resulting in non uniform flow of metal

11. Prevention:
• Modifying flow pattern by controlling temperature and friction
• Machining billet surface prior to extrusion
• Using dummy block