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Description:
H21 is a hot work tool steel suitable for applications where red hardness, high compressive
strength and wear resistance at elevated temperatures are required. These features together with
good impact resistance provide a steel with excellent properties for general purposes, hot working
conditions. Preheating prior to use in service will considerably improve tool life.
Applications:
H21 is particularly useful for hot forging and blanking dies and punches for making nuts, bolts and
other similar small components. Dies, cores, inserts, pins, etc for the die casting of copper base
alloys are also prime applications for this steel. Other uses include forming dies, shear blades, hot
extrusion dies, mandrels, punches, die holders, ejector discs and extrusion liners.
GRADE(%)
C
Si
Mn
W
Cr
V
P/S
H-21
0.30-0.40
<=0.40
<=0.40
7.5-9.0
2.20-2.70
0.20-0.50
<=0.03
Annealing:
Pack preferably in a suitable sealed container with spent carburising mixture or cast iron chippings
to prevent excessive scaling or decarburisation. Heat to 850°C / 880°C, holding at temperature for
sufficient time to achieve uniformity. Cool at less than 25°C per hour to 650°C followed by air
cooling. Correctly annealed the tools or parts should not exceed 248 HB.
Stress Relieving:
Heat to 600°C / 650°C. Hold for 2-4 hours and furnace cool.
Hardening:
Before heat treatment, sufficient machining should be carried out to remove surface decarburisation. Hardening should be carried out in controlled atmosphere furnaces or
neutral salt baths. Preheat slowly to 800°C / 850°C then transfer to a bath or furnace at
1120°C / 1170°C allowing sufficient time for uniform heating. Quench into warm oil or salt bath
operating at 520°C / 540°C. In the latter case ensure that the tools are allowed to equalise before
completing the quench by cooling in air.
Huangshi Young Sea Industry & Trade Co.,Ltd.
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Tel/Fax: +86-714-6330300
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