CPM MPL-1 Stainless Steel | Supracor

CPM MPL-1 (Supracor) is a powdered stainless steel developed in 1986 by Crucible and is one of the most popular powdered steels on the market. It has a very high carbon (3.80%) and chromium (24.00 - 24.20%) content, which gives it exceptional wear and corrosion resistance.

CPM MPL-1 | Supracor is a powder steel, meaning it is produced by pressing and sintering metal powders. This process produces a more uniform and stable steel structure than traditional smelting methods. This steel is often used in combination with other steels such as CPM-S30V and CPM-M4 to create composite materials with improved properties.

Crucible - MPL-1 / Crucible - CPM MPL-1 / Supracor (Crucible) - first introduced in 1995, this is a stainless tool steel with an exceptionally high carbon content of 3.75% - 3.80%. There is no other steel with a higher carbon content in the database today.

Supracor - the name is descriptive. The super material provides great abrasion resistance and can also be used for knife blades.

Maximum hardness after hardening 67 - 70 HRC.

Chemical composition

Supracor, as it is called in Europe, is Crucible's flagship. In the US it is called CPM MPl-1. Supracor is the highest alloy powder metallurgy steel in the world. With a carbon content of 3.75% and a very high chromium content of 24% with equally significant amounts of vanadium and molybdenum, Supracor sets the benchmark. Almost 40% of the material is non-ferrous. The proportion of the main carbide is 46% (CPM 440V: 24%). This means that almost half of the material consists of extremely hard carbides (carbon compounds).

The chemical composition alone commands respect. This respect increases significantly when you try to work with Supracor for the first time. Supracor is only available as a round material (e.g. 50 millimeters in diameter). Flat material is not available. Therefore, the rolling tires must be cut from the round material in the longitudinal direction. Although this sounds simple, in practice it is very difficult. Supracor cannot be cut with band saws with a carbide tip. In fact, Supracor has a hardness of 42 HRC in the annealed (non-hardened) state.

Advantages and disadvantages

Like any steel, stainless steel CPM MPL-1 | Supracor | Sopracor has its advantages and disadvantages. Let's consider the main ones.

Advantages CPM MPL-1 | Supracor:

• Very high wear resistance, making it ideal for tools subject to intense wear, such as knives, drills and cutters;
• Excellent corrosion resistance, allowing it to be used in high humidity and moderately aggressive environments;
• High strength, ensuring its durability and resistance to breakage;
• Holds its sharpening for a long time, which reduces maintenance costs.

Compared with CPM 420V steel, the abrasion resistance of CPM MPL-1 is approximately twice as high. A knife made of CPM-420V used by a hunter (expert) can remain in working condition even after half a year, and a knife made of CPM MPL-1 can remain sharp for a whole year.

Another outstanding characteristic of CPM MPL-1 steel is its very high corrosion resistance. Thanks to its composition (the matrix contains a lot of free chromium).

High strength is not a miracle either.

Disadvantages CPM MPL-1 | Supracor:

• Relatively high cost compared to other steels;
• Can be difficult to machine due to its high hardness;
• Impact toughness.

The Achilles heel of this super alloy is its low impact toughness. It is only about a third of CPM 420V (CPM 420V has the same impact toughness as 1.4125 = 440C). If someone uses the knife with dimensional cutting and not abuse, it will last an extremely long time. It takes extraordinary force to break a blade made of CPM MPL-1 Supracor | Soprocor steel. Of course, thickness, processing, sharpening angle and proper heat treatment also play a big role.

It is also not easy to sharpen a Supracor knife: the best sharpness can be achieved at a slow (90 rpm) setting. A diamond stone is not needed. However, the abrasive wear of consumables is higher when sharpening CPM MPL-1 | Supracor than with all other steels, and the procedure takes longer.

It is a very expensive and very difficult to machine stainless steel, making it relatively unprofitable for certain industries.

Conclusion

Despite all the advantages and disadvantages, CPM MPL-1 Supracor steel is a serious challenge (competitor) for other steels for the manufacture of knives and cutting tools.

Applications CPM MPL-1 | Supracor

• Knives for hunting, fishing and tourism;
• Drills and cutters for metal processing;
• Woodworking tools;
• Medical instruments;
• Kitchen knives.

Mechanical processing

CPM MPL-1 | Supracor, with a hardness of 42 HRC in the annealed condition, is very difficult to machine. The steel is difficult to saw with carbide saws.

One of the processing options is wire erosion (Electrical Discharge Machining of Stainless Steel). During wire erosion, using a thin wire and tension added to the spark erosion, the material evaporates. Even the hardest materials can be cut this way, if they are conductive. However, this procedure is not very cheap. Electrical discharge machines are CNC machines and are therefore expensive. This results in a high cost per machine hour.

In addition, this procedure takes a lot of time. Example: cutting a round material with a diameter of 50 mm by a length of 230 mm takes about two hours. Depending on the number of cuts, the thickness of the strips is formed and, accordingly, up to 24 hours of time are spent to cut only one piece of open round material. Consequently, huge cutting costs are added to the very expensive price of materials.

The resulting flat parts are polished on a grinding machine, primarily with CBN discs. The desired contour is then roughly polished before being cut with a diamond disc. This is also suitable with a friction disc made of corundum, but only if the disc is significantly worn. The workpiece is then processed further on a belt grinder. This is suitable with corundum volumes, but the volume consumption is very high.

The required drilling in the CPM MPL-1 | Supracor | Supracor steel plate can only be performed with a tungsten carbide drill, and the service life of the drill will be very short. Also, milling with carbide drills is extremely material-intensive: The service life of the drill up to the wear limit (carbide drill K 05) with one 10 mm drill and a 0.5 mm spatula is only 1-2 minutes.

It is important to understand that CPM MPL-1 is almost half carbide. The fact that the tools wear out very quickly is understandable.

Regarding sharpness: a belt sharpener is absolutely not suitable for obtaining high-quality sharpness (and not only with a Supracor blade). The temperatures during sharpening, which occur at the thinnest point on the cut, can be above 1000 °C. This can even lead to melting of the steel. These temperatures play a very negative role (mainly at the point of the cut - where the cutting edge is located). At extremely high temperatures - the results will be carelessly expressed.

All data on this page is taken from open sources. Some of them need confirmation and verification.