CPM REX M4 steel, often called simply M4 steel, is a special-purpose type of high speed steel. It is noted for its wear-resistance characteristics. It has very high carbon and vanadium contents. It is an excellent choice for premium cutting tools such as those used on abrasive alloys, heat-treated materials and castings.
Benefits of Choosing REX M4
Like all high speed steel, M4 is noted for its excellent resistance to wear and heat. This makes it very well-suited for cutting and similar machinery/tooling uses. This type of steel can be exposed to high temperatures without losing its hardness.
M4 steel has particularly high carbon and vanadium content, even compared to other types of HSS. This offers exceptionally good abrasion resistance. This alloy has high hardness, exceeding 65 on the Rockwell C scale.
When used for cutting applications, CPM REX M4 steel can take on even the most challenging materials. Its impressive hardness and resistance to abrasion help it to excel at cold work punches, die inserts and cutting. Compared to M2 and M3 steel, this alloy handled wear better when working with abrasive materials.
Top Applications for M4 Steel
As described above, M4 is well-suited for applications in which hardness and abrasion resistance at particularly important. These are a few common uses for REX M4:
- Form tools
- Broach inserts
- Header tooling
However, M4 steel should not simply be substituted for other alloys in all cases. The high hardness and high vanadium carbide content make this type of steel very challenging to grind after it has been heat treated. While this may be preferable in some cases, it is not optimal in others. Additionally, its hardness can be a detriment in some applications compared to PM M4, for example.
Technical Characteristics of CPM REX M4 Steel
The typical chemistry of M4 includes 4% vanadium and 1.3% carbon. Other major elements include 5.5% tungsten, 4% chromium, 4.5% molybdenum (where the “M” comes from), 0.3% manganese and 0.3% silicon.
The density of M4 is 0.288 pounds per cubic inch (7972 kilograms per cubic meter). Its specific gravity is 7.97.
The annealed hardness of CPM REX M4 steel is BHN 225/255. In this state, its machinability is around 35-40% of 1% carbon steel.
Thermal Treatments of REX M4
Use a double preheat to reduce distortion and stresses, particularly in large or complex tools. First, heat to 1100°F at a rate of no more than 400°F. Then, heat to between 1450°F and 1550°F. Normal tools can simply be preheated to the second range.
For austenitizing, heat rapidly after preheating. The range for furnace applications is 2200°F to 2250°F. For sale, it is 2175°F to 2225°F.
For pressurized gas quenching, rapidly quench to below 1000°F. For oil, quench to around 900°F (until black) then cool in air to between 125°F and 150°F. For salt, equalized to 1000°F to 1100°F then cool in air to between 125°F and 150°F.
Tempering range is typically between 1000°F and 1100°F. Hold that temperature for two hours than air cool to ambient. Double tempering is required, and a third tempering may be optimal. The third temper should be between 800°F and 1000°F.
Finally, annealing must be performed following hot work and before re-hardening the steel. To do this, heat to 1550°F to 1600°F at a rate of 400°F per hour. Hold that temperature for one hour per inch at 25.4-millimeter thickness. Cool slowly to 1000°F at a rate of 50°F per hour. Finally, let cool to ambient temperature.
Our M4 Steel Stock
We have several options for M4 rounds. They are available in 0.093, 0.109, 0.118, 0.125, 0.156, 0.203, 0.281, 0.312, 0.390, 0.515 and 0.578 inches. We do not currently have flats for CPM REX M4.