Extending Die Life for Aluminum Die Casting

Failure of dies for aluminum die casting is typically caused by thermal fatigue cracking or gross cracking. Other modes of failure include soldering to the die surface, erosion and corrosion of the die surface. It is clear that many factors can impact die life, including steel composition, heat treatment conditions, fabrication techniques and die casting processing parameters. This book provides a review of research published by NADCA in these areas over the past 15 years or so.

 

TABLE OF CONTENTS

Prelude …………………………………………………………………………………………………… i

Introduction ……………………………………………………………………………………………… 1

Background ……………………………………………………………………………………………… 3

Scope of the Book ……………………………………………………………………………………… 5

Factors that Influence Heat Checking ……………………………………………………………… 7

Heat Checking Mechanism ………………………………………………………………………… 8

Impact of Heat Treatment on Heat Checking …………………………………………………… 9

Austenitizing Temperature ……………………………………………………………………… 10

Quench Cooling Rate …………………………………………………………………………… 10

Tempering ……………………………………………………………………………………… 14

Impact of Electric Discharge Machining (EDM) on Heat Checking …………………………… 16

Impact of Die Coatings on Heat Checking ……………………………………………………… 18

Factors that Impact Gross Cracking ………………………………………………………………… 19

Introduction ………………………………………………………………………………………… 19

Steel Making Process ……………………………………………………………………………… 19

Annealed Microstructure …………………………………………………………………………… 20

Heat Treatment Process …………………………………………………………………………… 21

Die Preheating ……………………………………………………………………………………… 22

Factors Influencing Erosion …………………………………………………………………………… 25

Introduction ………………………………………………………………………………………… 25

Primary Parameters Influencing Erosion ………………………………………………………… 25

Impact of Die Coatings on Erosion ……………………………………………………………… 28

Minimizing erosion in Die Casting Dies ………………………………………………………… 30

Steel Chemistry ………………………………………………………………………………………… 33

Introduction ………………………………………………………………………………………… 33

Impact of Steel’s Constituents …………………………………………………………………… 34

Impact of Die Steel Composition on Heat Checking …………………………………………… 35

Impact of Steel Hardness on Heat Checking for Different Steels …………………………… 39

Impact of Steel Composition on Gross Cracking ……………………………………………… 42

Summary of New Die Steels ……………………………………………………………………… 42

Non-Ferrous Die Materials …………………………………………………………………………… 45

Impact of Die Casting Process Parameters on Die Life ………………………………………… 49

Influence of Cycle Time …………………………………………………………………………… 49

Impact of Lubricant Spraying ……………………………………………………………………… 50

Effect of Cooling Line Location and Spraying …………………………………………………… 51

Impact of Cooling Line Position …………………………………………………………………… 54

Pre-Heating ………………………………………………………………………………………… 55

Impact of Cycle Time on Die Temperature ……………………………………………………… 56

Practical Applications ………………………………………………………………………………… 59

Bibliography ……………………………………………………………………………………………… 63

Appendix 1: Description of the Case Reserve University Thermal Fatigue Tester …………………… 67