Page 16 - MetalForming magazine • December 2022

F
Tooling by Design
Increased Area
Fig. 2—Stress is reduced when the con- tact area increases.
demands of any application. These demands can cause premature wear, chipping, galling and plastic deforma- tion. Strive to achieve the best overall punch performance through a com- bined balance of tool-steel toughness and wear resistance.
Tool-Steel Selection
The most common tooling material for cold-working dies, D2 steel, can exhibit premature chipping and/or
In-Die Lubrication
Programmable Systems
wear when used in applications with higher-strength materials. This makes tooling hardness a prime concern. Hardness must be high enough to resist plastic deformation but not too high as to cause premature chipping or cracking. In general, tooling hardness usually falls in the range of 58-62 HRC.
For additional chipping resistance and wear resistance, powder metallurgy (PM) tool steels may offer a solution. PM tool steels feature a unique microstructure characteristic: small metal carbide particles uniformly dis- persed in the steel matrix. Though more costly, PM tool-steel materials often are more economical due to their low wear rate, and also are good sub- strates for surface coatings.
Tool steels are only as good as the heat treatment they receive. Unlike machining tools (drills, end mills, etc.), the nature of the stamping process places a high demand on compressive strength and toughness. As controlling these prop- erties directly impacts the performance
of the tool steel in service, consider the following when heat treating:
• Segregation by size and material type because each grade has a specific heat-treatment process
• The use of fixturing to ensure even support and uniform exposure to heat- ing and cooling cycles
• Preheat temperature, number of steps and soaking time
• Hardening temperature and soak- ing time
• Quenching (cooling) rate
• Quenching medium (air, oil, inert gas)
• Tempering temperature, time and number.
Most tool steels feature a generous range of acceptable tempering tem- peratures. In general, use the highest tempering temperature that will pro- vide the desired hardness. When select- ing a tool steel, choose one that best meets the toughness requirements of the job, then improve wear resistance with surface coatings. MF
radius = 0.002 in. max.
In-Die and Stock Lubrication Designed for Stampers by Stampers
Spray Cabinets & Roller Coater
t Co
s
ntain & Recycle Lube
Systems Customized for YOUR Needs
s
t
t
h
h
a
a
t
o
Small, Economical System
m
m
s
www.PaxProducts.com
www.metalformingmagazine.com
MetalForming/December 2022 13