The selection of mold material plays a crucial role in the overall process of mold making. It is an essential aspect that should not be overlooked.
When selecting a mold material, it is important to consider three key principles. Firstly, the mold should fulfill the work requirements in terms of wear resistance, strength, and toughness. This ensures that the mold can withstand the necessary work conditions without getting damaged or worn out easily. Secondly, the mold should meet the process requirements, meaning it should be compatible with the manufacturing processes involved in the production. This ensures smooth and efficient production without any hindrances or complications. Lastly, the mold material should also be economically feasible, taking into account the cost of the material and its lifespan. This ensures that the chosen material provides a good return on investment and is economically viable for the production process. Overall, these principles guide the selection of a mold material that can effectively fulfill its purpose in terms of performance, compatibility, and affordability.
Condition requirements
1. Wear resistance
One of the most fundamental and essential properties of a mold is its wear resistance. This characteristic is crucial because when the blank undergoes plastic deformation in the mold cavity, it flows and glides along the cavity's surface. Unfortunately, this movement causes intense friction between the cavity's surface and the blank, leading to wear and eventual failure of the mold. Therefore, it is imperative to have a mold material with high resistance to wear in order to maintain the mold's longevity and functionality.
The resilience of a mold component largely depends on its level of hardness, given that higher levels result in reduced wear and improved resistance to the same. That said, the material's carbide type, distribution, shape, size, and quantity also play a significant role in determining its wear resistance.
2. Toughness
The harsh working conditions that molds are subjected to can be extremely detrimental to their integrity. Many molds end up bearing the brunt of heavy impact loads and this can often lead to the occurrence of brittle fractures. It is essential for molds to possess high strength and toughness to avoid the risk of sudden fractures while in operation. Only then can they handle the work-related stresses that they are constantly exposed to, and perform efficiently without compromising on quality.
The carbon content, grain size, and organization state of the material are the key factors that determine the toughness of the mold.
3. Fatigue fracture performance
Fatigue fractures are commonly observed during the mold work, particularly under the influence of cyclic stress over a prolonged duration. These fractures can manifest in various forms, including low-energy multiple impact fatigue fractures, tensile fatigue fractures, contact fatigue fractures, and bending fatigue fractures. It is important to note that these fractures are induced due to repetitive loading and can significantly impact the structural integrity of the mold.
The mold's strength, toughness, hardness, and inclusion content are the primary factors determining its fatigue fracture performance.
4. High temperature performance
To ensure that the mold maintains its hardness and strength under high working temperatures, it is crucial for the mold material to possess excellent anti-tempering stability. In cases where the working temperature of the mold is elevated, the hardness and strength tend to diminish, resulting in premature mold wear, deformation, and ultimately failure. Therefore, by utilizing a mold material with higher anti-tempering stability, we can guarantee that the mold retains its desirable hardness and strength even when subjected to elevated working temperatures.
5. Heat and cold fatigue resistance
When working with molds, some may undergo repeated heating and cooling cycles which can lead to surface cracks and peeling due to changes in pressure and stress. This can cause an increase in friction, hinder plastic deformation, and lead to reduced dimensional accuracy, ultimately resulting in mold failure. Hot and cold fatigue is a common form of failure for hot work molds and these types of molds need to have a high resistance to this type of stress. To ensure proper functionality, it's important to monitor and maintain molds for signs of fatigue and address any issues promptly to prevent further damage.
6. Corrosion resistance
During the operation of plastic molds, the presence of chlorine and fluorine in the plastic often leads to the emergence of corrosive gases such as HCI and HF once heated. As a result, these gases will penetrate the mold cavity's surface and trigger a series of issues, including increased surface roughness and wear failure. The erosion caused by these gases can compromise the integrity and longevity of the mold, which may necessitate costly repairs or replacements. Therefore, it's crucial to take proactive measures to prevent the accumulation of these gases and protect the mold from erosion.