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Cutting Tools
Published in David A. Stephenson, John S. Agapiou, Metal Cutting Theory and Practice, 2018
David A. Stephenson, John S. Agapiou
High-speed steels (HSS) are self-hardening steels alloyed with W, Mo, Co, V, and Cr. They exhibit red hardness, which permits tools to cut at a dull red heat without loss of hardness or rapid blunting of the cutting edge. HSS is inexpensive compared to the other tool materials, is easily shaped, and has excellent fracture toughness and fatigue and shock resistance. However, the hardness of HSS decreases rapidly at temperatures above 540°C–600°C, and HSSs have less wear resistance, less chemical stability, and a greater tendency to form a built-up edge than other tool materials. Their limited wear resistance and chemical stability makes HSS tools suitable for use only at limited cutting speeds. Plain HSSs are generally used at cutting speeds below 35 m/min in steel, although special alloys such as the HSS-Co alloys discussed in the following can be used at speeds up to 50 m/min. HSS can be accurately ground and resharpened using conventional abrasive wheels. HSS is very commonly used for geometrically complex rotary tools such as drills, reamers, taps, and end-mills as well as for broaches and gear hobs and form cutters. HSS tools are also widely used in multi-spindle machines (e.g., gang drill presses, screw machines, and older transfer machines) with limited rigidity and speed capabilities.
Common Heat Treatment Practices
Published in Bankim Chandra Ray, Rajesh Kumar Prusty, Deepak Nayak, Phase Transformations and Heat Treatments of Steels, 2020
Bankim Chandra Ray, Rajesh Kumar Prusty, Deepak Nayak
When the amount of strong carbide-forming elements is large, and the highly alloyed steels are tempered at 500°C–600°C, the general decrease of hardness with tempering temperature is not only arrested, but an increase in hardness with improved toughness occurs. This increase in hardness is called secondary hardness or red hardness. Above 500°C, these elements have high diffusivity to nucleate and grow to form fine dispersion of alloy carbides to cause secondary hardening. Because of the lower diffusion rates of alloying elements, these alloy carbides are formed only at the high temperatures. Besides, at low temperatures, diffusion of solute atoms is sluggish to result in formation of any carbides.
Application of detonation coatings to design a new metal cutting tool
Published in Transactions of the IMF, 2018
A. A. Gallyamov, M. V. Nenashev, I. D. Ibatullin, A. Yu. Murzin
The application of the high-speed steels as the main material is determined by the following factors. First of all, these steels have low thermal conductivity, which additionally decreases the heat transfer from the processing area. Second, the high-speed steels are cheaper and easier to process than the hard alloys, which make the tool cheaper. Third, the high-speed steels are more resistant to the impacts and vibrations than the hard alloys, which increase the operational reliability of the tool. Fourth, the high-speed steels have high red hardness which provides their ability to work at the cyclic heat of up to 600–650°С with no reduction in strength capacity.