(1) Plastic deformation failure

Mainly due to the die material strength level is not high; or heat treatment process is not correct, failing to achieve the best toughness of steel; mold improper use of local overload occurs; for hot work mold high temperature softening will also lead to mold thermoplastic deformation failure. Plastic deformation failure can lead to mold deformation, which ultimately affect the quality of forgings.

(2) Die wear failure

The fundamental cause of die wear failure is the friction between the die and the blank. But the specific form of wear and wear process is related to many factors; mold pressure, temperature, billet deformation speed and lubrication in the working process. For hot work mold, due to its cavity surface by high temperature softening and wear resistance decline, plus the oxide itself also play the role of abrasive, it is decided that the wear process appears more complex. Die wear failure mainly leads to the forging die wear, affecting the precision of forgings.

(3) Die fatigue failure

Die fatigue failure is the root cause of stress concentration and cyclic loading. Although the load on the die is sometimes significantly lower than its yield strength, but because of the local stress concentration, so that the low load, in the stress concentration will still form micro-cracks. And mold are usually in high strength and low plastic state service, when the formation of micro-cracks, in the mold under the action of cyclic loading, micro-cracks are easy to expand and eventually lead to fatigue fracture.

(4) Cold and hot fatigue failure of the mold

For hot work mold, work with hot blanks due to mutual action, caused by the mold surface temperature often rises to 600 ~ 900 ℃ range. In order not to reduce the strength of the mold, it is necessary to spray coolant on the mold after demolding, so that it cools down. This week after week, is the mold surface repeatedly experienced rapid cold and hot process, in the mold surface will accumulate a considerable cycle of thermal stress, the stress is ultimately in the way of hot and cold fatigue release, the formation of hot and cold fatigue cracks. As for high-temperature oxidation, coolant corrosion and mold and high-temperature billet friction between the role is to accelerate the process of thermal fatigue.

(5) Failure under the influence of a combination of factors

Molds due to the actual working conditions are extremely complex, therefore, a mold can often appear at the same time a variety of forms of damage. Once these injuries occur, each may promote each other, and ultimately will accelerate the failure of the mold.