The influence of temperature on the mechanical properties of grey cast iron
The mechanical properties of grey cast iron are an important factor for considering the quality of grey cast iron products. With the changes of temperature in the processing and application of grey cast iron, the mechanical properties of grey cast iron also show obvious changes. It is of great theoretical and practical significance to study the influence of temperature on the mechanical properties of grey cast iron. In this paper, the influence of temperature on the mechanical properties of grey cast iron is studied.
First, the mechanical properties of grey cast iron will change with temperature. Generally speaking, with the increase of temperature, the hardness, strength and plasticity of grey cast iron will decrease. This is mainly due to the decrease in the yield strength and ultimate strength of grey cast iron with the increase of temperature. As the temperature increases, the material structure of grey cast iron is loosen, the better plasticity and toughness is increased, but its strength and hardness are decreased. The decrease of strength and hardness with the increase of temperature is mainly due to the decrease of the corresponding strength of crystal grains with the increase of temperature, so the yield strength and ultimate strength of materials to be processed are decreased.
Second, the applicability of grey cast iron is affected by temperature. Under the influence of temperature, grey cast iron can show different characteristics in different temperature range. Generally speaking, at high temperature, the structure of grey cast iron is more relaxed, the plasticity and toughness will increase, but its strength, hardness and stability will decrease. This kind of casting material can not be used as a structural material in high temperature environment. However, at low temperature, the structure of grey cast iron is more dense, with better strength, hardness and fatigue resistance, so it can be used as structural materials in cryogenic environment.
Third, the production of grey cast iron will be affected by temperature. Different temperatures will cause different states of the material in the process of grey cast iron production. In the normal temperature range, the metallographic structure of cast iron can remained relatively stable and uniform to ensure the quality of the part. If the casting temperature is too low, the cohesion and plasticity of the cast iron will be weakened, and the thermal shock caused by the rapid heat dissipation of the part directly entering the cold water can also cause the spheroidizing structure to be replaced by white graphite structure, which will make the mechanical properties of the part worse. If the casting temperature is too high, the frictional heat between the sand layer and the molten iron may cause the molten iron in the sand to be overheated and overheated, which will lead to the destruction of the casting structure.
Fourth, the composition of grey cast iron will also be affected by temperature. At high temperature, the effect of chemical composition on the properties of grey cast iron is weakened. The casting defects will be increased and the mechanical properties will be reduced. In addition, with the increase of temperature, the melting point of steel and casting alloy will decrease and the density of the material will increase, which will affect the filling performance and solidification shrinkage of the cast iron.
In a word, temperature is a key influencing factor in the mechanical properties of grey cast iron. The changes of production temperature, processing temperature and using temperature will all cause different effects on the mechanical properties of grey cast iron. Therefore, the temperature must be strictly controlled and monitored in the production and processing of grey cast iron. It is necessary to carry out theoretical analysis and process design reasonably to ensure the stability of mechanical properties and quality of grey cast iron products.
