What is the reason for the heating cracks in the heat treatment of the box furnace?
Box furnaces are mainly used for heat treatment such as normalizing, quenching and annealing of alloy steel products, various metal parts, or for high-temperature sintering of cutting blades such as diamond. During the heating process, sometimes the heated workpiece will have cracks, resulting in What are the reasons for these cracks? Here is a brief introduction:
The most common defect in workpiece heating is the appearance of cracks, including surface cracks and internal cracks. There are two reasons for surface cracks in products during heating:
One is caused by the existence of subcutaneous bubbles, impurities and original cracks on the surface of the workpiece itself;
The second is that surface defects develop under the action of temperature stress during heating. In addition, surface overheating will also cause surface cracks.
Internal cracks are caused by too fast heating speed or too high furnace temperature. Under the condition of too fast heating and cooling speed or too high furnace temperature, it may cause a large temperature difference between the surface and center of the workpiece, resulting in excessive thermal stress. , resulting in uneven internal expansion or contraction and internal cracks.