CPM® REX® M4 High Speed Steel
DATA SHEET
Typical Composition
| C | Mn | Si | Cr | W | Mo | V |
|---|---|---|---|---|---|---|
| 1.30 | 0.30 | 0.30 | 4.30 | 5.60 | 4.50 | 4.00 |
CPM® REX® M4 is a special-purpose high speed steel designed to give high wear resistance in tools. Its high vanadium and carbon content provide high resistance to cratering and wear in cold work punches, die inserts, and cutting applications involving high speeds and light cuts. It is designed to give maximum performance working with abrasive materials, exhibiting better wear resistance than M2 and M3.
The typical applications of Rex® M4 High Speed Steel include punches, spade drills, die inserts, slitter knives, broaches, shear blades, reamers, roll turning tools, milling cutters, form tools, chasers, taps, and lathe and planer tools.
Note: The above are some typical applications. Your specific application should not be undertaken without independent study and evaluation for suitability.
Critical Temperature
AC1 – 1545°F.
Forging
Heat slowly and uniformly to 1900 to 2000°F, soak long enough to ensure thorough heat penetration. Reheat if temperature falls below 1700°F. After forging, cool slowly in vermiculite or in a furnace.
Annealing
CPM® REX® M4 must be annealed after forging and before rehardening.
For full annealing, heat uniformly to 1600°F, hold at temperature for two hours, and cool slowly at 25°F per hour maximum in the furnace to below 1000°F. The steel may then be cooled in air if desired. For cycle annealing*, heat to 1600°F and hold at temperature for two hours, furnace cool to 1400°F and hold at temperature for six hours. The steel may then be cooled in air if desired. Annealing in controlled atmosphere furnaces or with suitable protective media is recommended.
Note: Temperatures shown throughout this data sheet are metal temperatures.
This data sheet is for informational purposes only. Alloy characteristics are subject to change due to chemical composition and/or processing. We do not certify the material’s suitability for specific applications.
*Cycle (isothermal) annealing is most practical for applications in which full advantage may be taken of the rapid cooling to the transformation temperature, and from this temperature down to room temperature. Thus, for small parts which can be handled in salt or lead baths, or for light loads in batch-type furnaces, cycle (isothermal) annealing makes possible large time savings as compared with the conventional slow furnace cooling.The method offers no particular advantage for applications such as batch annealing of large furnace loads, in which the rate of cooling to the center of the load may be so slow as to preclude any rapid cooling to the transformation temperatures. For such applications, conventional annealing offers a better assurance of obtaining the desired microstructure and properties.
Hardening
In hardening REX® M4, it is customary to use two furnaces. The first furnace is used to preheat to 1500°F to 1550°F; the second furnace is used to heat rapidly from the preheating temperature to the hardening temperature of 2150°F to 2250°F.
When a salt bath is used, the usual hardening temperature is 2125°F to 2225°F. The high-temperature bath should not be overloaded to the extent that cold charges cause a severe drop in bath temperature.
Vacuum hardening may be used for small sections, or when oil or pressure quench capabilities are available.
The high side of the hardening temperature range should be used for cutting tools. For cold work punch and die applications where increased toughness is required, the low side of the hardening temperature range should be used.
Quenching
Quench in oil, air, or a salt bath maintained at 1000°F to 1100°F. When oil quenching is used, particularly for tools of large sections or complicated design, it is good practice to use an interrupted quench. The tools should be quenched in oil until they have reached approximately 1000°F to 1100°F (dull red). They should then be removed from the oil and allowed to cool naturally in air.
When a salt bath is used, the tool is quenched into the bath and held just long enough to cool to the temperature of the bath. It is then removed from the bath and allowed to cool naturally in air.
Physical Properties
| Property | Value |
|---|---|
| Modulus of Elasticity in Tension (psi × 106) | 31 |
| Specific Gravity | 7.97 |
| Density (lbs./cu.in.) | 0.286 |
| Thermal Coefficient of Expansion (in/in/°F × 10-6) | |
| 100–500°F | 5.32 |
| 100–800°F | 6.24 |
| 100–1000°F | 6.64 |
| 100–1200°F | 6.82 |
| 100–1500°F | 6.99 |
Salt bath quenching of large sections generally results in slightly lower hardness than an interrupted oil quench. No matter what method of quenching is used, the tool should be allowed to cool to a temperature below 150°F or to a point where the tools can be held comfortably in the bare hand.
Straightening
Any necessary straightening is best done from the quench at any temperature down to 400°F.
Tempering
Temper immediately after quenching and cooling below 150°F or as soon as the tool can be held comfortably in bare hands. The tempering temperature may be varied depending on the application and required hardness. Triple tempering is required. For example: Heat to 1025°F and hold for two hours, allow to cool to room temperature; reheat to 1025°F and hold for two hours, and again cool to room temperature; finally heat for a third time to 1025°F, hold for two hours, and cool to room temperature.
Hardness
Austenitized as shown below in a salt bath, held two minutes at heat, quenched in oil, and tempered 2 + 2 + 2 hours at the temperature indicated.
| Tempering Temperature | Rc Hardness | |
|---|---|---|
| 2125°F | 2200°F | |
| As Quenched | 64/66 | 64/66 |
| 1000°F | 63.5/65.5 | 64/66 |
| 1025°F | 63/65 | 64/66 |
| 1050°F | 62/64 | 63/65 |
| 1075°F | 61/63 | 62/64 |
| 1100°F | 59/61 | 61/63 |
| 1150°F | 56/58 | 58/60 |
Impact Touchness: Rex® M4
| Hardening Temperature* | Temper** | Hardness | C-Notch Impact Strength |
|---|---|---|---|
| 2200°F | 1025°F | Rc65 | 20 Ft. lbs |
| 2125°F | 1050°F | Rc63 | 28 Ft. lbs |
*Salt bath temperatures
**Triple Tempered
Machining Data
Brinell 225/255
Approximately 30% of 1% Carbon Steel (W1)
| Operation | Tool Width or Depth of Cut (in) | High Speed Tooling | Carbide Tooling | ||
|---|---|---|---|---|---|
| Speed (fpm) | Feed (in/rev) | Speed (fpm) | Feed (in/rev) | ||
| Turning-Single Point |
.150 | 50 | .015 | 250 | .015 |
| .025 | 60 | .007 | 310 | .007 | |
| Drilling | ¼ | 30 | .003 | ||
| ½ | 30 | .005 | |||
| 1 | 30 | .010 | |||
| 2 | 30 | .013 | |||
| Broaching | 5 | .002 | |||
| Face Milling | .125 | 55 | .007 | 240 | .010 |
| .025 | 70 | .005 | 320 | .008 | |
| Cut Off | .062 | 35 | .001 | 150 | .002 |
| .125 | 35 | .001 | 150 | .003 | |
| .250 | 35 | .0015 | 150 | .0045 | |
| Cutting Fluid | Sulfurized Oil-Light Duty | Water Soluble Oil |
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Niagara Specialty Metals | 12600 Clarence Center Road, Akron, NY 14001
