die tools types are complex, operating conditions vary greatly, and damaged parts are also different, but the failure methods can be summed up in roughly three types, namely wear, cracking, and plastic deformation.
①. Wear failure
When the die tools is in operation, it touches the forming blank and produces relative movement. Because of the relative movement of the surface, the phenomenon of gradually losing the material when touching the surface is called abrasion. Wear failure can be divided into the following types:
a. Tired and worn
When the two touch surfaces move relative to each other, under the effect of cyclic stress (mechanical stress and thermal stress), the phenomenon that the surface metal fatigues and falls is called fatigue wear.
b. Cavitation wear and erosion wear
The bubbles on the surface of the metal burst, causing instant shock and high temperature, causing the appearance of the die tools to form small pits and pits, which is called cavitation wear.
Liquid and solid fine particles repeatedly impact the surface of the die tools at high speed, causing the loss of part of the surface of the die tools. The phenomenon of forming pits and pits is called erosion wear.
c. Abrasion and wear
In the friction process, chemical or electrochemical reactions occur between the surface of the die tools and the surrounding medium, coupled with the mechanical effect of friction, causing the appearance of data to fall out of the phenomenon called abrasive wear.
In the relative movement of the die tools and the workpiece (or blank), wear often coexists in a variety of ways and affects each other.
②. Crack failure
When the die tools has a large crack or is separated into two parts and several parts lose the working capacity, it becomes a crack failure.
Cracking can be divided into plastic cracking and brittle cracking. Most of the die tools materials are medium and high-strength carbide, and the cracking method is mostly brittle cracking. Brittle cracking can be divided into one-time cracking and fatigue cracking.
③. Plastic deformation failure
The die tools receives a lot of stress during operation and is uneven. When the stress of a certain part of the die tools exceeds the yield limit of the die tools material at the current temperature, plastic deformation occurs through methods such as lattice slippage, twinning, and grain boundary slippage, which changes the shape or size of the die tools, and When the operation cannot be corrected, it is called plastic deformation failure. The failure methods of plastic deformation are upsetting, tortuous, cavity expansion, sinking and so on.
The plastic deformation of the die tools is the yielding process of the metal material of the die tools. Whether plastic deformation occurs, the dominant effect is the mechanical load and the room temperature strength of the die tools. Whether or not plastic deformation occurs in a die tools that is operated at a high temperature mainly depends on the operating temperature of the die tools and the high temperature strength of the die tools material.
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