International Mold Steel

DH31-EX

High strength, tough and high heat check resistance hot work die steel. 

Overview  

DH31-EX is a hot working die steel with the best balance of strength and toughness showing the comparable softening resistance to SKD7 and twice hardenability as that of SKD61.

Applications include:

Aluminum Die Cast Dies

Aluminum Die Cast Parts

Hot Forging Dies

Hot Pressing Dies

Aluminum Extrusion Dies

Unique Characteristics

  • High hardenability
    High toughness is obtained even in large size die.
  • High strength
    High softening resistance  at elevated temperature contributes to high wear resistance.
  • High toughness
    DH31-EX has higher toughness than that of SKD61.
  • High heat check resistance
    Excellent heat check resistance leads to longer life. 

Coefficient of thermal expansion

Specific heat

Thermal conductivity

Density

Characteristics

Tempering hardness

  • Quenching temp: 1030°C
  • T.P. size: 10H x 10W x 15L

Softening resistance

  • Holding temp.: 600°C
  • Quenching temp: 1030°C x 30min. –> 150 Dia. Bar, AC
  • T.P. size: 10H x 10W x 15L

Heat check resistance

Heat check resistance is further improved by increasing hardness without deteriorating toughness.

An example to improve heat check resistance (200mmm thickness air cool quenched die)

<Test procedures>

  • Specimen: 15mm
  • I/Heating: 20<-> 700C
  • Number of cycles: 1000 times

Toughness

  • Quenching temp: 1030°C x 30min. –> 150 Dia. Bar, AC
  • T.P. size: L

Elevated temperature tensile properties

  • T.P. size: Ø 8 x 40L

Erosion resistance

Creep properties

Hardenability

High toughness is obtained even in large size dies due to high hardenability.

Continuous cooling transformation curve

Bainite hardenability

As Bainite transformation starting time is twice as that of SKD61, 130min., quenching operations is easily and safely carried out without troubling such as toughness deterioration in large size dies.

Quenching cooling time vs. toughness

Cooling time of mid portion from 1030°C to 300°C (min)

TP size: Ø440

Quenching temp: 1030°C

Surface Hardening Properties

PS, PW process

  • Daido Amistar’s originally developed process.
  • PW process improves wear, fatigue and corrosion resistance.
  • PS process improves scuffing and erosion resistance.
  • DH31-EX shows good machinability as high strength-high tough grades.
  • Recommended machining conditions
  • TIG manual welding condition

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