High speed steel. Its properties and classification

In our time, high-speed steel continues to be the leading material for the production of a variety of metal tools and cutting tools. Such alloys are often used in the manufacture of machine tools, drills and drill heads. Despite the wide variety of carbide composite and ceramic materials that now appear, which provide even greater processing capacity, high-speed tool steels firmly hold their positions.

The wide use of such alloys for the production of complex cutting tools is due to the combination of a high strength index (up to 68 HRC) and heat resistance (they do not lose their working properties even at a temperature of 650 ° C) with a high viscosity value significantly higher than that for carbide composite materials . In addition, high-speed steel has extremely high manufacturability, which implies good workability by pressure and cutting.

What properties such an alloy will have depends on the alloying additives. Usually high-speed steel is a multicomponent system with the content of chromium, molybdenum, tungsten, cobalt and vanadium. The presence of various components, as well as their content in percentage terms, is indicated in the marking. The letter P here means that the steel is high-speed, the subsequent figure indicates the percentage of tungsten. Further letters denote the presence of other alloying elements, and the numbers following the letters are their percentage mass fraction in the alloy. Thus, the letter M means the presence in the system of molybdenum, Ф-vanadium, К-cobalt, and А-nitrogen.

According to the content of alloying additives, high-speed steel can be classified into tungsten, molybdenum, tungsten-molybdenum. Cobalt- doped metals are distinguished into a special group. Such alloys, as a rule, are used in the manufacture of tools for processing hard-to-work parts from heat-resistant alloys. High - speed steel, alloyed with vanadium is mainly intended for the production of tools of so-called "finishing" finishing - broaches, sweeps and others.

The most common and, perhaps, the oldest brand of high-speed steel P18 is used for making complex and shaped thread-cutting tools. Means of the same standard form for high-quality metal processing are made mainly from the alloy grade P9. Cutters, cutters and the like are made of it.

According to the operating temperature regime, high-speed steels are divided into three categories: alloys with normal, high and high heat resistance. The first group includes tungsten (P18, P9) and tungsten-molybdenum (P6M5). These grades are used in the processing of non-ferrous metals, structural steels and cast iron.

For materials of the second category, an unusually high content of cobalt, carbon and vanadium is characteristic. The most popular brand in this group is P6M5F3. Vanadium steels are characterized by increased wear resistance. Their only serious drawback is poor sandability, since the hardness of vanadium carbides is not inferior to that of an electrocorundum grinding wheel.

And, finally, the third category is characterized by a low percentage of carbon content, which makes them suitable for processing high-temperature, stainless and titanium alloys. Another of their characteristic distinguishing features is the large number of alloying elements. This group includes such brands as 3В20К20Х4Ф, В11М7К23, etc.