1. What M42 High-Speed Steel Is
M42 is a high-speed steel belonging to the M-series, distinguished by a high cobalt content of about 8 percent that boosts its hot hardness. The steel is designed for cutting tools that operate at high speeds and generate intense heat at the cutting edge. It is supplied as round bar, flat bar and forgings in the annealed condition, ready for machining and heat treatment by the tool maker.
2. Chemical Composition
M42 contains roughly 1.10 percent carbon, 9.5 percent molybdenum, 3.75 percent chromium, 1.5 percent tungsten, 1.15 percent vanadium and 8 percent cobalt. The molybdenum and tungsten form hard carbides, while the cobalt raises the temperature at which the steel softens. The balance of alloying elements gives the combination of wear resistance and red hardness that cutting tools need.
3. Hardness and Heat Treatment
After hardening from around 1180-1210 degrees Celsius and tempering, M42 reaches 66-69 HRC, higher than standard M2 high-speed steel. The high hardening temperature and multiple tempers develop secondary hardening and the maximum red hardness. The steel is always supplied annealed at about 255-269 HB so that it can be machined before hardening.
4. Red Hardness and Wear Resistance
Red hardness means the cutting edge stays hard even when it glows red-hot during heavy machining. M42 can operate at higher cutting speeds than M2 because its cobalt content delays softening at 550-600 degrees Celsius. The fine carbides give excellent wear resistance in abrasive workpiece materials such as titanium, stainless steel and hardened alloys.
5. Applications and Working Practice
M42 is used for drills, end mills, taps, reamers, broaches, slitting saws and form tools machining tough and abrasive materials. Because of its hardness, grinding after hardening uses CBN or aluminum oxide wheels with light cuts and coolant. When ordering M42, specify the size, the condition (annealed or hardened), and the standard such as ASTM A600 to ensure the correct composition.
Frequently Asked Questions
Q: What is M42 high-speed steel?
M42 is a high-speed steel of the M-series, distinguished by a high cobalt content of about 8 percent that boosts its hot hardness. It is designed for cutting tools that operate at high speeds and generate intense heat at the cutting edge, and is supplied as round bar, flat bar and forgings in the annealed condition.
Q: What is the chemical composition of M42?
M42 contains roughly 1.10 percent carbon, 9.5 percent molybdenum, 3.75 percent chromium, 1.5 percent tungsten, 1.15 percent vanadium and 8 percent cobalt. The molybdenum and tungsten form hard carbides, while the cobalt raises the temperature at which the steel softens.
Q: What hardness does M42 reach?
After hardening from around 1180-1210 degrees Celsius and tempering, M42 reaches 66-69 HRC, which is higher than standard M2 high-speed steel. The steel is always supplied annealed at about 255-269 HB so that it can be machined before hardening.
Q: What is red hardness and why does it matter?
Red hardness means the cutting edge stays hard even when it glows red-hot during heavy machining. M42 can operate at higher cutting speeds than M2 because its cobalt content delays softening at 550-600 degrees Celsius, and its fine carbides give excellent wear resistance in abrasive workpiece materials.
Q: What is M42 used for?
It is used for drills, end mills, taps, reamers, broaches, slitting saws and form tools machining tough and abrasive materials such as titanium, stainless steel and hardened alloys. Grinding after hardening uses CBN or aluminum oxide wheels with light cuts and coolant.
Q: What should be specified when ordering M42?
Specify the size, the condition (annealed or hardened) and the standard, such as ASTM A600, to ensure the correct composition and heat treatment.