Oct 25 2012
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
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.