Designation by Standards

Chemical Composition (in weight ％)

DeＳＣＲＩＰＴion
UTOPMO4 is a 5％ chromium hot work tool steel designed particularly for applications requiring extreme toughness combined with good red hardness. It provides an extra margin of safest in tools subject to heavy hammer blows,***those tools containing deep recesses***sharp corners. While UTOPMO4 has been designed primarily as a hot work tool steel, it has been used in many cold work applications where extra toughness is required at the sacrifice of some wear resistance.

Applications
UTOPMO4 has been used primarily for tools requiring resistance to softening at elevated temperatures. Such tools include forging dies***punches, die-casting dies, aluminum extrusion dies, hot heading dies, piercing***forming punches, etc. 

Physical properties (avarage values) at ambient temperature
Modulus of elasticity [103 x N/mm2]: 215 
Density [g/cm3]: 7.70
Thermal conductivity [W/m.K]: 25.0 
Electric resistivity [Ohm mm2/m]: 0.52
Specific heat capacity[J/g.K]: 0.46

Coefficient of Linear Thermal Expansion 10-6 oC-1

Continuous Cooling Transformation (CCT) Diagram

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Time-Temperature Transformation (TTT) Diagram

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Soft Annealing
Heat to 760-820oC, cool slowly in furnace. This will produce a maximum Brinell hardness of 250.

Stress Relieving
To relieve machining strains for greater accuracy in hardening, first rough machine, then anneal below the critical 649/677oC a minimum of one hour at temperature,***cool very slowly, followed by finish machining.

Hardening
Harden from a temperature of 1000-1040oC followed by air, oil warm bath (450-550oC) quenching. Hardness after quenching is 54-58 HRC.

Tempering
Tempering temperature: See the diagram bellow.

Tempering Temperature (oC) vs. Hardness (HRC) vs. Tensile Stregth (N/mm2)