DH31-EX
High strength, tough and high heat check resistance hot work die steel.
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.
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ81.gif?fit=350%2C271&ssl=1)
Applications include:
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/08/plastic-molds.jpg?fit=612%2C408&ssl=1)
Aluminum Die Cast Dies
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/08/Zinc.jpg?fit=612%2C407&ssl=1)
Aluminum Die Cast Parts
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/08/aluminum.jpg?fit=612%2C408&ssl=1)
Hot Forging Dies
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/08/plunger.jpg?fit=387%2C258&ssl=1)
Hot Pressing Dies
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/08/die-plate.jpg?fit=385%2C257&ssl=1)
Aluminum Extrusion Dies
- 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.
PHYSICAL PROPERTIES
Coefficient of thermal expansion
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ98.gif?fit=500%2C39&ssl=1)
Specific heat
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ100.gif?fit=500%2C53&ssl=1)
Thermal conductivity
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ99.gif?fit=500%2C55&ssl=1)
Density
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ101.gif?fit=269%2C73&ssl=1)
Characteristics
Tempering hardness
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ85.gif?fit=283%2C247&ssl=1)
- Quenching temp: 1030°C
- T.P. size: 10H x 10W x 15L
Softening resistance
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ87.gif?fit=290%2C228&ssl=1)
- 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
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ89.gif?fit=300%2C365&ssl=1)
An example to improve heat check resistance (200mmm thickness air cool quenched die)
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ90.gif?fit=275%2C178&ssl=1)
<Test procedures>
- Specimen: 15mm
- I/Heating: 20<-> 700C
- Number of cycles: 1000 times
Toughness
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ86.gif?fit=331%2C240&ssl=1)
- Quenching temp: 1030°C x 30min. –> 150 Dia. Bar, AC
- T.P. size: L
Elevated temperature tensile properties
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ88.gif?fit=349%2C247&ssl=1)
- T.P. size: Ø 8 x 40L
Erosion resistance
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ91.gif?fit=287%2C294&ssl=1)
Creep properties
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ92.gif?fit=313%2C248&ssl=1)
Hardenability
Continuous cooling transformation curve
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ82.gif?fit=500%2C232&ssl=1)
Bainite hardenability
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ83.gif?fit=306%2C220&ssl=1)
Quenching cooling time vs. toughness
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ84.gif?fit=363%2C234&ssl=1)
Cooling time of mid portion from 1030°C to 300°C (min)
TP size: Ø440
Quenching temp: 1030°C
Surface Hardening Properties
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/dh31-s18.gif?fit=298%2C227&ssl=1)
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/dh31-s19.gif?fit=171%2C272&ssl=1)
PS, PW process
- Daido Amistar’s originally developed process.
- PW process improves wear, fatigue and corrosion resistance.
- PS process improves scuffing and erosion resistance.
Machinability
- DH31-EX shows good machinability as high strength-high tough grades.
- Recommended machining conditions
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ95.gif?resize=500%2C73&ssl=1)
Repair Welding Conditions
- TIG manual welding condition
![](https://i0.wp.com/imsteel.com/wp-content/uploads/2023/09/includ97.gif?resize=500%2C305&ssl=1)
BENEFITS
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