DH31-EX Steel – Advanced Mold & Die Steel by Titus Steel

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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.

Features

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

Microstructure

CCT Curves

Heat Treatment Condition

Heat Treatment

Forging Temperature (°C)	Treating Temperature (°C)			Hardness		Transformation Point (°C)
Forging Temperature (°C)	Annealing	Quenching	Tempering	Annealed	Quenched & Tempered	Ac	Ms
1200~900	820-870 Slow Cooling	1000-1050 Air Cooling	550~650 Air Cooling	≤235HB	≤53HRC	805~885	300 Austenite Temp. 1030°C

Tempering Hardness

Nitriding Characteristics

Machinability

Machinability Endmilling

Machinability Drilling

Characteristics

Softening Resistance

Toughness

Heat Checking Resistance

Hot Hardness

Al Erosion Resistance

Mechanical Properties

Fatigue Properties

Physical Properties

Thermal Expansion Rate

Temperature	20~100°C	20~200°C	20~300°C	20~400°C	20~500°C	20~600°C	20~700°C
x10^-6/K	11.6	11.8	12.0	12.2	12.5	12.8	12.9

Thermal Conductivity

Temperature	100°C	200°C	300°C	400°C	500°C	600°C	700°C
W/m • K	26.7	27.9	29.0	29.4	29.7	30.0	29.5

Specific Heat

Temperature	100°C	200°C	300°C	400°C	500°C	600°C	700°C
J/kg • K [cal/g • °C]	487 [0.116]	527 [0.126]	572 [0.137]	626 [0.150]	703 [0.168]	802 [0.192]	985 [0.235]

Density

20°C

7800.0 kg/m³
[7.80] [g/cm³]

Applications

Aluminum die cast dies especially for large size – long life use
Aluminum die cast parts such as pins and plunger sleeve
Hot forging dies
Hot pressing dies
Aluminum extrusion dies

Examples of Applications

Field	Application Mold	DH31-EX		Conventional
Field	Application Mold	Hardness (HRC)	Life (Shot)	Grade	Hardness (HRC)	Life (Shot)
Die Cast	Water Jacket	36 Ion Nitriding	24000	DH21	36 Ion Nitriding	10000
Die Cast	Cylinder Head Cover	50 (HIT)	> 40000	SKD61	47	18000
Hot Forging	Rear Axcel	48	8000	SKD62	43	2000
Hot Forging	Rear Spindle	48 Ion Nitriding	11000	SKD62	45 Ion Nitriding	4000