Die hot die mold of cold, but few people understand that hot die often meet some problems, Yu Hui steel small die mold according to the recent understanding of the use of heat, the common problems about heat die steel share.
(1) cavity heated metal surface in die forging work, usually the surface temperature is 300~400 DEG C hot extrusion die cavity, up to 500~800 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 more than 1000 DEG C, this high temperature will make the cavity surface hardness and strength decreased significantly, therefore, is the hot plastic deformation resistance is high as basic requirements on the thermal properties of mould steel, including high hardness and high temperature strength, high thermal deformation resistance that is, tempering stability. Join Cr, W, Si and other alloy elements, by alloying method, can improve the stability of tempering steel.
(2) the cavity surface of the metal have Gelau (cracking) hot die at work is usually intermittent, every time the hot metal forming to surface water, oil and air cooling medium cavity. Therefore, the working state is repeatedly heated and cooling, so that the cavity surface of the metal have repeated expansion and contraction, repeated tension and compression under the action of alternating stress. The results of surface cracks caused by the cavity, the phenomenon known as thermal fatigue, therefore, requirements for hot work die steel with high thermal fatigue resistance. And the main factors affecting the thermal fatigue resistance of steel are as follows.
The thermal conductivity of steel: higher thermal conductivity, 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 content, carbon content of high thermal conductivity and low carbon content is too low, will lead to the decline of the hardness and strength of steel. Therefore, in the production of carbon steel is usually used for hot working die.
The critical point of steel: usually the critical point of steel (Ac1) steel is higher, the lower the tendency of thermal fatigue. Therefore, usually by the addition of alloying elements Cr, W, Si by increasing the critical point of steel, improve the thermal fatigue resistance of steel to.
Kunshan hot die steel