Die 1, hot working conditions
Including hot die forging die, hot extrusion die and die three. As mentioned before. The main characteristics of hot working die working conditions is in contact with hot metal, which is the main difference with the cold die working conditions. It will have the following two problems:
(1) cavity heated metal surface. Usually die forging work. The cavity surface temperature is 300~400 DEG C hot extrusion die above can reach 500 to 800 DEG C; die casting mold cavity temperature and type of material and the casting temperature. Such as black metal die-casting mold cavity temperature can reach 1000 DEG C. This high temperature causes the surface hardness and strength of the cavity was significantly lower in the use of prone play crib. Therefore. The basic performance of hot die steel is hot plastic deformation resistance is high, including high hardness and high temperature strength, high thermal deformation resistance, actually reflects the high tempering stability of steel. The first way so we can find the hot die steel alloy, namely Cr, W and Si. added alloy elements can improve the stability of tempering steel.
(2) the cavity surface of the metal have Gelau (Gui Lie). Hot mold work is characterized by intermittent. Every time after the hot metal forming to the surface of water, oil and air cooling medium cavity. The hot work die state is repeatedly heated and cooled, so that the cavity surface of the metal have repeated expansion and contraction, the tension and compression under repeated stress. The results of surface cracks caused by the cavity, the phenomenon known as thermal fatigue, thus, puts forward second basic requirements on the performance of hot die steel. That has a high thermal fatigue resistance. Generally speaking, the main factors affecting the thermal fatigue resistance of steel is:
The thermal conductivity of steel. High thermal conductivity of steel, can minimize heat the metal mold surface, thereby reducing the tendency of thermal fatigue of steel. Is generally believed that the thermal conductivity of steel and carbon, the carbon content of high thermal conductivity is low, so not hot work die steel with high carbon steel. Commonly used in the production of carbon steel (C0.3%5~0.6%) carbon content is too low. Leads to the decrease of the hardness and strength of steel is also unfavorable.
The critical point of steel. Usually the critical point of steel (Acl steel). The higher the lower the tendency of thermal fatigue. Usually by the addition of alloying elements Cr, W, Si, critical point lead to increase of steel. In order to improve the thermal fatigue resistance of steel.
Die steel, 2 commonly used heat
(1) hammer forging die steel. Generally speaking, hammer forging die steel are two problems: one is the impact load of work. Therefore, the mechanical properties of steel are higher, especially high requirements on plastic deformation resistance and toughness; the two section of die forging of large size (< 400mm) of the Steel Hardenability Requirements in order to ensure the high performance of the whole organization and even die.
The commonly used building hammer forging steel with 5CrNiMo, 5CrMnMo, 5CrNiW, 5CrNiTi and 5CrMnMoSiV etc.. Eye pattern of different types of hammer should be used in different materials. Hammer forging die for large or large to 5CrNiMo as well. You can also use 5CrNiTi, 5CrNiW or 5CrMnMoSi etc.. Hammer forging die for small and medium usually used 5CrMnMO steel.
(2) steel hot extrusion die, hot extrusion dies is the characteristics of slower loading rate, therefore, the cavity temperature is higher, usually up to 500 to 800 DEG C. Use of such performance requirements of steel should be based on high temperature strength (high tempering stability) and high thermal fatigue performance. AK and hardenability of the requirements may be appropriate to lower. Hot extrusion die generally smaller, often less than 70~90 mm.
The commonly used hot extrusion die with 4CrW2Si, 3Cr2W8V and 5%Cr type 4CrW2Si. hot die steel, which can be cold working die steel, hot die steel can be done. As for different purposes, using different treatment methods. The lower quenching temperature and cold die (870 - 900 DEG C) and low or medium temperature tempering; high temperature quenching is used for heat mode (generally 950 to 1000 DEG C) and high temperature tempering.
(3) die casting mold steel. On the whole, and the thermal performance requirements of steel die extrusion die steel, Kunshan hot die steelThe tempering require high stability and high thermal fatigue resistance. So often the choice of steel is roughly the same as hot extrusion die steel. As usual with 4CrW2Si. and 3Cr2W8V steel. But differ as to the low melting point Zn alloy die-casting mold. The choice of 40Cr, 30CrMnSi and 40CrMo; Al and Mg alloy die-casting mold, can choose 4CrW2Si and 4Cr5MoSiV on Cu alloy casting die made of 3Cr2W8V steel.