What does HSS stand for?

HSS primarily stands for High-Speed Steel or High-Speed Tool Steel. It is a crucial category of alloy steels predominantly used for creating engineering cutting tools.

Definition and Primary Function

High-Speed Steels (HSS) are a class of alloy steels specifically designed for applications requiring materials that can maintain their hardness and cutting edge even at elevated temperatures generated during high-speed machining operations. They are extensively utilized to manufacture various engineering cutting tools.

Chemical Composition

The following table shows the composition of the high-speed steel we produce.

Steel Type	C	Si	Mn	Cr	V	W	Mo	Co
M2	0.78-1.05%	0.20-0.45%	0.15-0.40%	3.75-4.50%	1.60-2.20%	5.50-6.75%	4.50-5.50%	–
M35	0.80–0.90%	0.20–0.45%	0.20–0.45%	3.75–4.50%	1.75–2.20%	5.50–6.75%	4.50–5.50%	4.50–5.50%
M42	1.05 – 1.1%	0.15 – 0.65%	0.15 – 0.40%	3.5 – 4.25%	0.95 – 1.35%	1.15 – 1.85%	9.0 – 10.0%	7.75 – 8.75%

Key Characteristics and Properties

• High Hardness: HSS exhibits high hardness, which is important for resisting penetration and deformation during cutting.
• Red Hardness (Heat Resistance): Refers to its ability to resist softening or annealing at temperatures of 400°F (205°C) and above. However, these abilities decline rapidly at temperatures above 540°C to 600°C.
• Wear Resistance: HSS has good resistance to abrasive wear.
• Toughness and Shock Resistance: HSS demonstrates excellent fracture toughness and resistance to shock loading, allowing tools to withstand impact forces without brittle fracture.
• Machinability: HSS can be hot-rolled and forged into rough shapes, then machined before heat treatment and finish grinding. 
• Cost-Effectiveness: HSS tools are relatively inexpensive compared to other tool materials, making them a common choice, especially for monolithic tools.

Classification and Grades

• T-type Steels: These grades primarily use tungsten as the major alloying element. They tend to be less tough than M-types but are easier to heat-treat.
• M-type Steels: These grades primarily use molybdenum. They are more commonly used for rotary tools, such as drills, end mills, and taps. M2 is a commonly used grade for drills and taps, while M42 exhibits the greatest hot strength.
• International and National Standards: HSS grades are specified in various standards, such as BS 4659:1989 in the UK, which includes details on hot-work, cold-work, and plastic molding tool steels. The ISO Standard 4957 and the German system (prefix ‘S’ for Schnellstahl) also classify HSS by chemical composition and application. ISO designations, like HS2-9-1-8, denote the percentages of tungsten, molybdenum, vanadium, and cobalt.

Applications

HSS is a versatile material used in a wide array of tools:

• Cutting Tools: Common applications include drills, reamers, taps, milling cutters, broaches, and gear hobs. It is also used for turning operations, especially in multi-spindle machines.
• Specialized Machining: HSS tools are employed for machining challenging materials like titanium and aluminum alloys.
• Industrial Tools: This includes saw blades (especially bi-metal steel strips for band saws), precision punching tools, and various punches and dies.
• Dies: Used for presses and hammers, hot trimming, hot swaging, and hot extrusion tools and mandrels.