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Technical Information for 420 Mold Quality Steel

AISI 420 is an air-or-oil hardening ESR or VAR remelted stainless mold steel noted for its excellent polishability characteristics. typical analysis is shown in the chart below:

Carbon Silicon Manganese Chromium Vanadium
.38% 0.75% 0.5% 13.6% 0.3%
AISI 420 is used in mold applications requiring corrosion resistance, good machinability and dimensional stability. as well as good polishability. Typical applications are:
Injection molds
Compressions molds
Transfer Molds
Fixtures
Jigs
Glass Molds
Knives
Scissors
Meat Choppers
Surgical Instruments
Springs
Constructional Parts
Die Casting Nozzles

 

Heat Treatment:
Forging:
Heat Slowly to 1650°F - 2010°F
Allow steel to heat through before forging.
After forging, allow 420 to cool slowly in furnace, sand, vermiculite or dry coke breeze.
Anneal as soon a possible.
Soft Annealing:
Surface protection - pack in tubes/containers with cast-iron chips.
Heat thoroughly to 1400°F, and allow to cool.
Annealed hardness will be approximately 210-215 Brinell.
Stress Relieving:
Rough machine prior to stress relieving.
Heat steel to 1250°F; hold at temperature for 2 hours.
Cool in furnace to 900°F - 940°F, and then air-cool.
Hardening:
Pre-heat to 1110°F - 1560°F
Austenitizing temperature: 1800°F - 1920°F
Hold steel at hardening temperature until workpiece is thoroughly heated through.
Surface Protection: pack hardening or controlled atmosphere furnaces.

 

Hardening Temperature,°F Holding time, minutes Surface hardness before tempering
1830 40 53±2 HRc
1880 30 55±2 HRc
1920 20 56±2 Hrc

 

Tempering:
Double tempering of 420 is preferred. Refer to tempering chart for desired hardness. minimum tempering temperature is 360°F. Minimum holding time at temperature is 2 hours.

 

Tempering Temperature, °F Hardness, Rc
360 53
390 52
440 52
480 52
930 53
1020 47
1110 36

 

For More Information please call or fax us at 800-654-2901  (fax) 860-684-6354

 

 

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Last modified: March 16, 2000