Understand the details of fine casting processing operations

　　Robot stainless steel accessoriesThe use of fine casting is more and more extensive, and the processing technology is becoming more and more. During this period, the cooling process is an indispensable process. Some have to experience the solid phase transformation of the alloy, and the comparison of the metal changes during the phase transformation, for example, The volume of carbon steel changes from the δ phase to the γ phase, and the volume increases when the γ phase undergoes eutectoid changes.

However, assuming that the temperature of all parts of the casting is the same, microscopic stress is unlikely to occur when solid phase transformation occurs, but only microscopic stress. When the phase transition temperature is higher than the critical temperature of plastic-elastic modification, the alloy is in a plastic state during the phase transition. Even if the temperature of each part of the casting exists, the phase transition stress that occurs is not large, and will gradually decrease or even disappear.

HypothesisDongguan Precision CastingThe phase transition temperature of the part is lower than the critical temperature, and the temperature difference of each part of the casting is large. If the phase transition time of each part is not the same, it will cause the microscopic phase transition stress. Because the phase transition time is different, the phase transition stress may become a temporary stress or a residual stress. .

When the thin-walled part of the dewaxing casting undergoes a solid phase transformation, the thick-walled part is still in a plastic state. Part of it is plastically stretched. As a result, only a small tensile stress occurs inside the casting, and it gradually disappears over time. In this case, assuming that the casting continues to cool, the thick-walled part undergoes a phase change to increase its volume. Because it is already in an elastic state, the thin-walled part will be elastically stretched by the inner layer to form a tensile stress. The thick-walled part is elastically compressed by the outer layer to form a compressive stress. Under this condition, the remaining phase change stress and the remaining thermal stress have opposite signs and can cancel each other out.

When the thin-walled part of the casting releases a solid phase transition, the thick-walled part is already in an elastic state. If the new phase volume is greater than the old phase, the thick-walled part is elastically stretched to form a tensile stress, and the thin-walled part is elastically compressed to form a temporary compression. stress. At this time, the sign of the phase transformation stress is the same as the sign of the thermal stress, that is, the stress is superimposed.Dongguan Precision CastingWhen the cooling is continued until the phase change occurs in the thick wall part, the specific volume increases and expands, so that the phase change stress formed in the previous section disappears.