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What are the classification characteristics of hot work die steel?

Update:12-09-2020
Summary:

Composition characteristics of hot work die steel: 1. C […]

Composition characteristics of hot work die steel:
1. Carbon content
Generally medium carbon, the mass fraction of carbon is 0.3% to 0.6%. The guarantee material has higher strength and hardness, higher hardenability, better expectation and toughness.
2. Alloying elements
The added alloying elements include Cr, Mn, Si, Ni, W, Mo, V and other alloying elements. Among them, the role of Cr, Mn, Si, Ni alloying elements is to strengthen ferrite and improve hardenability. W and Mo alloying elements are to prevent temper brittleness. Cr, W, and Si alloying elements can increase the phase transition temperature, so that the mold will not undergo phase transition during the alternating heating and cooling process and cause a large volume change, thereby improving its resistance Thermal fatigue capability. In addition, W, Mo, V, etc. are precipitated in the form of carbides during tempering to produce secondary hardening, so that the hot work die steel maintains a relatively high hardness at a higher temperature, which is important for the normal operation of the hot work die steel One of the conditions is that Cr and Si can improve the oxidation resistance of steel.


Hot work die steel classification:
There are many classification methods for hot work die steel, which can be classified according to alloy element content and performance after heat treatment. It can be classified by purpose or alloy element.
(1) According to the purpose, it can be divided into steel for hot forging die, steel for hot extrusion die, steel for die casting die, and steel for hot blanking die.
(2) According to heat resistance, it can be divided into low heat resistant steel (350~370℃), medium heat resistant steel (550~600℃) and high heat resistant steel.
(3) Divided into high toughness hot work die steel, high heat strength hot work die steel, high wear resistance hot work die steel according to its unique properties.
(4) According to the classification of alloying elements, it can be divided into low alloy hot work die steel (tungsten, chromium and molybdenum series), medium alloy hot work die steel and high alloy hot work die steel (tungsten molybdenum series and chromium molybdenum series); Or divided into tungsten hot mold steel, chromium hot mold steel and chromium tungsten molybdenum hot mold steel. The high-temperature strength and thermal stability of the chromium-tungsten high-alloy hot-work die steel are not as good as those of the tungsten-molybdenum series, and the cold and hot fatigue resistance and toughness are higher than those of the tungsten-molybdenum series.
Hot work die steel refers to alloy tool steel suitable for making molds for thermal deformation processing of metals, such as hot forging dies, hot extrusion dies, die-casting dies, and hot upsetting dies. Because the hot work mold works under high temperature and high pressure for a long time, the mold material is required to have high strength, hardness and thermal stability, especially high thermal strength, thermal fatigue, toughness and wear resistance.

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