Cold Work Die Steels
DC53
Heat Treat:
DC53 Heat Treat – DC53 is only as good as the heat
treatment it receives. The heat treat process can be broken down into two
segments, Hardening & Tempering. DC53 is typically air hardened using a vacuum
furnace however it can also be processed by using a gas or electric furnace with
or without a controlled atmosphere when wrapped in stainless foil or salt bath
hardened by immersing the part in high temperature salts.
Air Hardening – Air hardening DC53 is best accomplished
under vacuum. First, preheat and hold at 800° C (1,475° F) to 850° C (1,560° F)
until the part is uniformly heated and then increase the heat to 1,030° C
(1,885° F) to Austenitize, otherwise known as soaking the tool. Austenitize 25
to 30 minutes per inch at temperature (to be safe, minimum austenitize time for
smaller parts under 1 inch can be up to 1 hour) up to 4 inches thick in cross
section and 10 to 25 minutes per inch for thickness over 4 inches before inert
gas pressure quenching (Generally in nitrogen), to rapid cool with 2 times
atmosphere pressure (2 bar) or high velocity equivalent. To be safe, longer
times are acceptable while shorter times are not.
Quench rates using 3 bar pressure or higher are not recommended
due to the potential for distorting and the higher stress involved. The
quenching phase converts the majority of the tool steel from the austenitic
state to an un-tempered martensite condition. The part should then be
immediately tempered once it has reached 45° C (120° F). Be sure to check
hardness at this point to assure that the part has reached the desirable
hardness if at least 64 HRC.
Salt Bath Hardening - Per-heat the part to 850° C (1,550°
F) until uniformly heated. Austenitize in a molten salt bath at 1,030° C (1,885°
F) for a minimum of 5 minutes. See chart below for details. Salt quench and then
allowed to slow cool in still air to 45° C (120° F) to 65° C to (150° F) before
tempering.
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Material growth
.10% to .15% (.001” to .0015” per inch).
An optional third temper recommended for intricate high
precision components requiring EDM work or PVD coatings. |
Tempering – Tempering is commonly performed in a non-atmosphere
controlled convection furnace. The first temper should be conducted as soon as
the part can be handled at about 45° C (120° F) to 65° C to (150° F). The part
should be allowed to cool to ambient temperature between subsequent tempers.
To achieve HRC 60-62, temper DC53 twice at 540° C (1,005° F) for 60 to 90
minutes per inch in thickness in cross section. The minimum tempering time is
90 minutes. Temper twice at 520° C (970° F) for the same amount of time to
achieve HRC 62-64. A hardness les than HRC 60 is not generally recommended for
most punch and die components due to insufficient compressive strength
typically needed for stamping applications. Applications requiring additional
toughness can be double tempered at 550° C (1,020° F) to achieve HRC 58-60.
If size change or distortion of hardened DC53 due machining, grinding,
applying surface treatments or wire EDM work is a concern in high precision
applications, an optional third temper of 400° C (750° F) can be applied to
the initial heat treat process. This final tempering temperature is high
enough to temper the remaining un-tempered martensite, but not high enough to
convert additional retained austenite resulting in a more stable structure.
The third temper is typically not necessary if the tool has been hardened
using the salt bath process.
Inspection - Conducting a hardness test after the heat treat process
is complete is just one method used to measure the quality of heat treat. For
additional quality assurance, it is also recommended that a precise
dimensional measurement be taken from a given feature both before and after
the entire heat treat process to assure that the proper amount of growth has
taken place. Properly heat treated DC53 can be expected to grow approximately
.1% to .1 ½% (.001” to .0015” per inch) of its original size before hardening.
Shrinkage of the tooling can be a sign of problems in the hardening and or
tempering process and is generally attributed to excessive amounts of retained
austenite.
Vacuum Tempering – As when tempering most tool steels, vacuum
tempering is a more difficult process to control than convection tempering and
fluctuations in hardness results are to be expected. It should only be used
when absolutely necessary and ideally be limited to smaller parts with a
simple geometry.
Cryogenics - Freezing at 185° C (-300° F) between the first and
second temper may also be beneficial to toughness however, specific data is
not readily available. It is important to note that cryogenics should always
be followed by a temper.
Forging – For special applications, DC53 can also be forged into
many shapes. The temperature for forging is between 900° C (1,650° F) and
1,100° C (2,010° F). Annealing after forging in highly recommended to minimize
stress in the part and assuring optimum heat treat response.
Annealing - DC53 can be annealed by uniformly heating the part to
800° C (1,475° F) to 850° C (1,550° F), and holding for 2 hours followed by a
slow cooling at no more than 27° C (50° F) degrees per hour to until the it
has dropped below 500° C (930° F). The part can then be removed from the
furnace and allowed to continue to cool in still air to room temperature. If
decarburization is a concern, annealing vacuum is recommended. In order to
minimize size change, the pre-coating and post heat treat will need to be as
similar as possible.
Daido Steel Limited and International Mold Steel, Inc. shall not be
responsible for damages caused by misunderstanding or improper use of the
technical information contained in the brochure. The contents of this brochure
may be subject to change without notice. Please inquire for the latest
information. No portion of this brochure may be reproduced without express
permission of Daido Steel Limited and International Mold Steel, Inc. DC53 in a
registered trademark of Daido Steel Limited and International Mold Steel, Inc.
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