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(DC53)

Description

DC53 steel is a new general purpose cold work die and mold steel whose strength and toughness approach those of high-speed steels. DC53 steel, is an improvement over alloy tool steel D2 specified in Standard (JIS) G4404. It eliminates the disadvantages of insufficient hardness and toughness, resulting from high-temperature tempering found with D2, and is intended to replace D2 in use for general purpose and precision dies. DC53 steel also has excellent machining characteristics and is well suited as a substrate for PVD surface treatments. DC53 steel can also be hot process CVD and TD (Thermal Diffusion) coated, however post heat treat is generally recommended.

Chemical Composition

CSiMnPSCrMoV
0.961.000.280.0180.0028.002.100.32

Standards

JISDINBOHLERHITACHI
DC531.2990K340SLD MAGIC

Properties

  1. Higher hardness (62-64 HRc) than D2 after heat treatment.
  2. Twice the toughness of D2 with superior wear resistance.
  3. Substantially higher fatigue strength compared to D2.
  4. Smaller primary carbides than D2 protect the die from chipping and cracking.
  5. Secondary refining process (DLF) reduces impurities.
  6. Machines and grinds up to 40% faster than D2.
  7. Less residual stress after wire EDMing.

Applications

  1. Stepped punch and press-punching dies
  2. Concrete sprayer parts, rotor plates
  3. Swaging dies and backers
  4. Dies for cold forging
  5. Thread-rolling circular dies
  6. Piercing punch
  7. Thread-rolling dies for heat-treated bolts
  8. Forming dies
  9. Stripper plates for lead frame blanking
  10. Gauges
  11. Screws for injection molding machines
  12. Plastic Molds

Heat Treatment

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. Preheating (1)：Warming to 550~600℃, holding 30 minutes per 25 mm.

Welding: Lower minimum pre-and post – heating temperature than D2 reduces the incidence of weld cracking and simplifies welding. Low hardness decline in heat affected zone minimises any deterioration in performance.

Hardening Vacuum Furnace: Pre-heat to 300-400oC and then to 800-850oC
allowing sufficient time to equalise. Raise to 1,020-1,040oC and allow soaking time

Quenching Vacuum Furnace: The high hardenability of this steel enables it to
be satisfactorally quenched in a vacuum furnace.

Surface Treatments: Surface treatments such as CVD, PVD, TD and Nitriding require the use of relatively high processing temperatures. While this can be a problem with standard D2, the higher through hardness of DC53 steel at elevated temperatures will allow these surface treatments to be used successfully.

Tempering: Double temper according to the hardness and toughness charts below. As with D2, a third temper at 400oC should be carried out to avoid any chance of any delayed grain growth and distortion. This is the preferred heat treatment for most applications as high hardness will be the primary consideration. Where maximum toughness is required, double temper between 200 and 300oC (depending on application). Note the material tempered at the lower temperature should not be subjected to subsequent high temperature processes such as PVD.

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. 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.

Salt Bath Hardening

Thickness Inch (mm)Immersion Time (Min)
1/4" (5mm)5-8
1/2" (12mm)10-12
3/4" (20mm)10-15
1 1/2" (30mm)15-20
2" (50mm)20-25
4" (100mm)30-40
AustenitizeDouble High Temperature Draw
1,030 ° C
1,885 ° F		520 ° C HRC 62/64
968 ° F
540 ° C HRC 60/62
1,004 ° F
550 ° C HRC 58/60
1,022 ° F
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 less 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.