Common defects in tempering of quenching equipment
Common defects in tempering of quenching equipment:
The common tempering defects are high and low hardness, uneven hardness, tempering deformation and brittleness.
(1) Unqualified tempering hardness is too high, too low or uneven, mainly due to the tempering temperature is too low, too high or the furnace temperature is not uniform.After tempering hard over low need to repair, re-quenching, tempering.If the hardness is too high after tempering, it can be tempered again according to the tempering specification.The reason that hardness is not uniform, may be because the quantity of furnace is too much, or choose heating furnace to be caused by improper.If the tempering is carried out in an atmosphere furnace, the forced circulation of air flow in the furnace should be made, otherwise the temperature in the furnace cannot be uniform.
(2) Distortion occurs to the workpiece after tempering: it is usually caused by the unbalance of stress in the workpiece before tempering, stress relaxation and stress redistribution during tempering.The distortion after tempering can be avoided or eliminated by tempering straightening and hot spot straightening.
(3) If the toughness is too low in the first type of tempering brittleness of the tempered workpiece, or the steel with the second type of tempering brittleness, the tempering brittleness of the workpiece will occur if there is no rapid cooling after tempering.For the first kind of temper brittleness, only by re-heating quenching, another tempering temperature to eliminate.For the second type of temper brittleness, you can use the method of reheating tempering and then fast cooling to eliminate.
(4) In addition, sometimes during the tempering process, there will be network cracks, such as quenched high carbon steel workpiece in the tempering, if heated too fast, the surface first tempering, compared to the volume, resulting in multi-direction tensile stress, easy to form network cracks.
According to the specific causes of network cracks, corresponding measures can be taken to avoid them.