生产护坡模具时，在温挤压前除了要对坯料进行加热和润滑外，还要对挤压凸模和凹模进行预热。一般预热至150～300℃再进行挤压生产。护坡模具预热主要为了保证：
In the production of slope protection die, not only the blank should be heated and lubricated, but also the extrusion punch and die should be preheated before warm extrusion. Generally preheat to 150-300 ℃ before extrusion. The preheating of slope protection mould is mainly to ensure:
(1)使挤压坯料放入模具时坯料降温不致过快，以免塑性降低、变形抗力增加；同时避免坯料表面和中心层温差过大，以防止由于变形不均匀性而导致挤压件产生缺陷或护坡模具损坏。
(1) when the extruded blank is put into the mold, the temperature of the blank will not be lowered too fast, so as to avoid the decrease of plasticity and the increase of deformation resistance; at the same time, the temperature difference between the surface and the center layer of the blank will not be too large, so as to prevent the defects of the extruded part or the damage of the slope protection mold due to the uneven deformation.
(2)减小护坡模具与毛坯接液压钢坝触的温差，避免模具表面的温度迅速上升而导致护坡模具内部温差过大而产生很大的内应力，以降低护坡模具在工作时产生破坏的危险。
(2) reduce the temperature difference between the slope protection mold and the blank, avoid the rapid rise of the temperature on the surface of the mold, which will lead to the excessive temperature difference inside the slope protection mold and generate great internal stress, so as to reduce the risk of damage of the slope protection mold during operatio