Tungsten Hot Work Tool Steels

Introduction
Hot work tool steels are steels capable of withstanding high abrasion, heat and pressure conditions that prevail in manufacturing units that perform processes such as forming, shearing and punching of metals at high temperatures of 480 to 760°C (900 to 1400°F). These steels have wear resistance up to 540°C (1000°F).

Hot work tool steels are designated as group H steels and they have 0.35% to 0.45% carbon, 6% to 25% chromium, with vanadium, molybdenum, and tungsten as the other alloying elements. Tungsten is primarily used in hot forming tool steels due to its high temperature strength, toughness and resistance to grain growth.

Overview
Tungsten hot-work steels constitute the H21 to H26 types of hot work steels. These steels have similar characteristics as those of other of high-speed steels. The hot work steel type H26 has low carbon content when compared to that of T1 high speed steel. The primary alloying elements of tungsten hot-work steels include tungsten, carbon, chromium and vanadium.

Properties
Tungsten hot work steels have high alloy content, which enhances their heat resistance. The high alloy content also makes the tungsten steels brittle and unsuitable for the water-cooling process. Breakage of tungsten hot work steels can be reduced if they are preheated to operating temperatures prior to use. Tungsten steels have normal working hardness of 45 to 55 HRC. Thermal shock resistance and toughness of these steels can be improved by reducing the carbon content. In such cases, it is necessary to adjust the tungsten and vanadium content also as these two reduce the hardenability of steel by trapping large amount of carbon in the form of carbides.

Scaling can be reduced by quenching tungsten hot-work steels in oil or hot salt. Tungsten hot-work steels are resistant to distortion when they are air- hardened, and have higher hardening temperature when compared to chromium hot-work steels.

Applications
Tungsten hot work steels find applications in the following areas:

•Manufacturing mandrels and extrusion dies for high temperature applications, such as extrusion of brass, nickel alloys, and steel
•Hot-forging dies of rugged design.

Tungsten Alloy Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-alloy.com
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