The presentation discusses extrusion defects, highlighting that these irregularities arise from non-uniform flow and stress distribution, influenced by wall friction and temperature. Key types of defects include surface cracking, internal cracking, and piping defects, each caused by specific conditions during the extrusion process. Preventive measures include modifying the flow pattern, controlling temperature and friction, and machining the billet surface prior to extrusion.

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