HSS PM M4 HC Steel

HSS PM M4 HC impresses with a very clean and homogeneous microstructure with evenly spread carbides which optimize its wear resistance. The high carbon and vanadium content gives HSS PM M4 HC an exceptional abrasion resistance which makes it suitable for cold work punches, machining abrasive alloys and cutting applications that involve high speed.

General information to High Speed Steels

High Speed Steel a high alloyed tool steel, often used for drills, taps, turning tools and broaches, has a 3-4 times higher cutting speed without loosing its hardness up to a temperature of 1112°F (600°C). In comparison ordinary cold work tool steel loses its hardness at about 392°F (200°C). The foundation for its abilities can be found in its alloys as well as its martensitic microstructure.

Tungsten (W): Forms carbides (especially tungsten carbide) which increase the red hot hardness, tempering resistance and wear resistance.

Molybdenum (Mo): Molybdenum can replace tungsten and has the same effect as tungsten at half the mass. Molybdenum does form carbides, increases red hot hardness, temper- and wear resistance but has to undergo a more complex heat treatment.

Vanadium (V): It forms vanadium carbide, which, as in some other steels, increases wear resistance because of its hardness (601 HBN / 58 HRC).

Chromium (Cr): Is involved in carbide formation and improves through hardenability. This enables tools with large cross sections to be hardened.

Carbon (C): Is needed both to form martensite and carbides. The proportion is adjusted in line with the proportion of the other elements.

Cobalt (Co): Increases the temperature up to which the material can be used, meaning above which temperature martensite transforms. It prevents the growth of precipitated carbides.

Heat treatment

Annealing

Heat the work piece uniformly to a temperature of 1550-1600°F (843-871°C), hold for 2 hours and then slowly cool by a rate of 20-40°F (11-22°C) per hour to a temperature of 1100°F (593°C).

Stress relieving

After machining the material roughly heat it to a temperature of 1110-1290°F (599-699°C) for about 2 hours, then slowly cool down and finish machining after cooling.

Hardening

It is recommended to harden PM M4 in a salt bath, vacuum furnace or in a controlled atmosphere.

Preheat PM M4 uniformly to 1450-1550°F (788-843°C), then raise the temperature to range of 2175-2225°F (1191-1218°C) and soak slightly according to the chosen working hardness, avoid over-soaking. Finish the process with cooling the part down to a temperature of 100-120°F (38-49°C) and quench.

Quenching media

• Air
• Oil
• Vacuum
• Molten salt (temperature of 1000-1099°F (538-593°C))

Tempering

Tempering should be done straight after quenching. Heat the parts uniformly to a temperature range of 1000-1200°F (538-649°C) for the first temper.

A double temper is required, with a cool down to ambient temperature in between tempers and a third temper recommended for maximum wear resistance when hardening from 2100°F (1149°C).

For our tempering diagram, please click here.

Machining

Forging

Heat slowly to a temperature of 2000-2100°F (1093-1149°C), do not forge under the temperature of 1700°F (927°C) and reheat as often as needed. When forging is finished cool the parts down slowly in lime or ash.

Welding

When welding PM M4 the parts should be preheated and similar fillers to the base material should be used.

Grinding

Local heat on the surface should be avoided during grinding as it may alter the temper of the work piece.

Surface treatment

This steel grade can be coated with chemical and physical deposition (CVD and PVD).

Decarburization

This steel grade is susceptible to decarburization which can be prevented with a controlled atmosphere furnace during heat treatment.