Tool Steel


Also found in: Dictionary, Thesaurus, Wikipedia.

tool steel

[′tül ¦stēl]
(metallurgy)
Any of various steels capable of being hardened sufficiently so as to be a suitable material for making cutting tools.

Tool Steel

 

carbon or alloy steel for the manufacture of cutting and measuring tools, and dies for hot and cold forming, as well as parts of machines which undergo increased wear under moderate dynamic loads (ball and roller bearings, gears, and motion screws in high-precision machine tools). As a rule, tool steel contains more than 0.6–0.7 percent carbon; die steels for hot forming, which contain 0.3–0.6 percent carbon, are an exception. For improved performance characteristics, tool steels undergo thermal treatment (hardening or tempering), which increases their Rockwell C hardness (HRC) to 60–66 and the bending strength to 2.5–3.5 giganewtons per sq m (GN/m2), or 250–350 kilograms-force per sq mm (kgf/mm2). As the hardness of tool steel increases so does its wear resistance (the ability to retain fixed dimensions and shape of the operating surface under friction with high pressures). Tool steels alloyed with chromium and manganese have higher hardenability and calcinability than carbon steels. Increased red hardness of tool steel—the ability to retain high hardness and wear resistance at temperatures up to 500°-700°C—is achieved by alloying steels with tungsten, molybdenum, and vanadium. Tool steels are subdivided into three groups according to their resistance to the heat that is generated during their use (see Table 1).

Steels with low heat resistance retain great hardness up to 150°-200°C and are used for low-speed cutting of soft materials and for cold forming. Carbon steels of this group are characterized by low hardenability—upon hardening, articles with a diameter or thickness of more than 15–20 mm acquire great hardness (up to 65 HRC) only in a thin surface layer, retaining a soft and viscous core. Because of increased deformation during hardening with cooling in water, mainly tools of simple shapes, such as files, reamers, and hand taps, are made of carbon steel. Low-alloy steels, which have somewhat better hardenability, are used for tools with a small cross section requiring high and uniform hardness, such as hacksaw blades for manual cutting of metals, razor blades, and circular wood saws. Alloyed steels of this group have high hardenability (25–100 mm) and are used for measuring tools, ball races of antifriction bearings, and dies of complex shape.

Table 1. Chemical composition of common Soviet tool steels (average, percent)
 CMnSiCrwMoV
 Steels with low heat resistance
Carbon steels       
USA............0.80.250.25≦0.1
U10A...........1.00.250.25≦0.1
U12A...........1.20.250.25≦0.1
U13A...........1.30.250.25≦0.1
Low-alloy steels       
9KhF...........0.90.40.250.550.2
11KhF..........1.10.50.250.550.1
13Kh...........0.30.40.250.55
V2F............1.20.40.250.51.70.1
Alloy steels       
Kh............1.00.30.21.5
KhVSG.........1.00.750.850.90.850.1
7KhG2VM.......0.752.10.31.71.10.70.15
6KhS..........0.650.250.81.1
 Steels with high heat resistance
KhGVF.........1.10.250.2561.306
Kh6F4M........1.650.250.2560.838
Kh12M.........1.550.250.25120.5
55Kh6V3SMF......0.550.250.8630.80.8
 Heat-resistant steels (die steels)
4Kh52VFS........0.40.251.052.00.8
4Kh3BMFS........0.40.350.83.51.01.40.7
3Kh2V8F.........0.350.250.252.58.00.3
2Kh8V8M2K5......0.250.250.47.57.51.88.0

Steels with high heat resistance retain their performance characteristics at temperatures up to 250°-4O0°C. They are mainly alloyed steels with a high chromium content (up to 12 percent). They have increased wear resistance under conditions of abrasive wear, since they contain up to 20–30 percent high-hardness chromium and vanadium carbides: Me7C3 (Vickers hardness [HV], 1, 200–1,400) and MeC (2,000 HV). After thermal treatment (hardening with cooling in air, oil, or molten salts with a temperature of 150°-180°C), they acquire a hardness of up to 63 HRC. These steels are characterized by high hardenability (up to 300–400 mm) and minimal volume changes during hardening. High-chromium steels are used in manufacturing large dies that undergo increased wear, as well as surgical instruments that are stable in aggressive mediums.

Steels that are resistant to heat retain their hardness up to 560o-700°C. Tungsten and molybdenum are the basic alloying elements of these steels and provide their red hardness. Steels with an increased carbon content (0.7–1.5 percent) and high hardness (up to 64–68 HRC) are used for the manufacture of cutting tools; steels with up to 0.4 percent carbon (die steels), which have lower hardness but better viscosity, are used for hot-forming dies and pressure metal-casting molds.

REFERENCES

Guliaev, A. P., K. A. Malinina, and S. M. Saverina. Instrumental’nye stali: Spravochnik. Moscow, 1961.
Geller, Iu. A. Instrumental’nye stali, 3rd ed. Moscow, 1968. (Contains bibliography.)

IU. A. GELLER

References in periodicals archive ?
The global tool steel market is predicted to touch USD 5.86 billion at a 5.05% CAGR over the forecast period (2017-2023), states the new Market Research Future (MRFR) report.
This paste contains small copper and graphite particles that roll up like ball bearings between the tool steel and working bushing.
A difference in behaviour, as a function of temperature, was clearly observed for the three tool steel samples.
(TOKYO: 5486) (ISIN: JP3786200000) has concluded an agreement with Diehl Steel company in the US for the transfer of assets owned by Diehl to a subsidiary of Hitachi Metals America, LLC to expand global sales of die, mold and tool steels in our specialty steel business, the company said.
Southern Tool Steel has two locations and around 90 employees serving the southeastern United States.
Carrs Tool Steels, which supplies machine tool-makers with steel, and employs 30 people, has changed hands for a multi-million pound sum.
An incredibly promising candidate for successful semisolid material application is high-carbon, high-chromium ledeburitic tool steel. Due to the growing demand for cold-work tool steel in various industrial applications, it is crucial to improve the fabrication technique because complex shapes involve an extensive and costly workshop effort.
The functional performance (testing in blanking conditions) of the tool steel S390 (the best grade in adhesive wear tests) with thin PVD coatings was studied in the same conditions as the blanking performance of carbide composites in our previous research [12,13].
The material studied was a conventional ledeburitic high-carbon, high-chromium tool steel named DIN 1.2379 (AISI D2) obtained by ingot metallurgy routes.
Initial investment costs of copper alloys are higher than for tool steel. At UK prices at the time of writing, copper alloys cost between 8 and 12 times more than an equivalent mass of P20 tool steel, depending upon the exact alloy formulation and properties.
The set shown has a slide cut from 17-4 PH stainless and a receiver machined from 4140 tool steel. These major parts are manufactured from a solid piece of billet steel and machined on new, CNC machining centers to exacting, close tolerances.