M46 Molybdenum High Speed Tool Steel (UNS T11346)

Topics Covered

Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Other Designations
Fabrication and Heat Treatment
     Forging
     Annealing
     Tempering
     Heat Treatment
Applications

Introduction

High-speed tool steels are divided into molybdenum high-speed steels and tungsten high-speed steels. Molybdenum high-speed steels are known as Group M steels. They have lower initial cost even though both types of high-speed steels are equivalent in performance. Tools made using high-speed tool steels can be coated with titanium carbide, titanium nitride, and other coatings by physical vapor deposition process for enhancing performance and prolonging life of the tool. There are different types of molybdenum high speed tool steels. Except M6, M 1 to M 10 contains some tungsten, but no cobalt.

M46 (UNS T11346) is a type of molybdenum high speed tool. Tungsten, chromium, molybdenum, cobalt, and vanadium are added to M46 for increasing its strength. Its vanadium content and carbon content of 1.25% can increase wear resistance, and the cobalt content increases its performance.

Chemical Composition

The following table shows the chemical composition of M46 molybdenum high speed tool steels.

Element Content
FE, Iron
Balance
C 1.10-1.20%
Mn 0.20-0.40%
Si 0.30-0.55%
Cr 4.00-4.75%
Ni 0.3%
Mo 6.00-7.00%
W 5.00-5.75%
V 1.85-2.20%
Co 11.00-12.25%
Cu 0.25%
P 0.03%
S 0.03%

Physical Properties

The physical properties of M46 molybdenum high speed tool steels are outlined in the following table.

Physical Properties Metric Imperial
Density 7.7-8.03 ×1000 kg/m3 480-501 lb/ft3
Melting Point 1427°C 2600°F

Mechanical Properties

The mechanical properties of M46 molybdenum high speed tool steels are tabulated below:

Mechanical Properties Metric Imperial
Poisson's ratio 0.27-0.30 0.27-0.30
Elastic modulus 190-210 GPa 27557-30457 ksi

Other Designations

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Other designations that are equivalent to AISI M46 molybdenum high speed tool steel include:

  • ASTM A600
  • FED QQ-T-590
  • UNS T11344
  • UNS T11346

Fabrication and Heat Treatment

Forging

M46 steels are forged from 1149 to 955°C (2100 to 1750°F). They should not be forged below 955°C (1750°F ).

Annealing

M46 tool steels are annealed at 871-899°C (1600-1650°F). They are then slowly cooled in the furnace at a temperature of less than 4°C (40°F) per hour.

Tempering

M46 steels are tempered at a temperature ranging from 524 to 566°C (975 to 1050°F) with Rockwell c hardness of 69 to 67. Tempering process can be repeated at the same temperature for one hour.

Heat Treatment

M46 steels are preheated to 788°C (1450°F). They are then rapidly heated to 1205°C (2200°F). Parts are held at 1205°C (2200°F) for 3 to 5 minutes followed by salt bathing or quenching in oil or air.

Applications

M46 molybdenum high speed tool steels are mainly used for cutting tools.

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