What problems may arise when forging is quenched and cooled?
Next, let’s learn about the quality problems and solutions of forgings in quenching and cooling:
Insufficient hardness and enough hardening depth: quenching cooling rate is low is forging quenching hardness is insufficient, the cause of the uneven hardness and hardening depth is not enough, but, according to the actual quenching forging materials, shape, size and heat treatment requirements, and can be divided into high temperature stage of insufficient cooling speed and cooling speed in low temperature stage and different situation such as insufficient cooling speed and low temperature stage.For example.For small and medium forgings, the insufficient quenching hardness is often caused by the insufficient cooling rate in the middle and high temperature stage, and when the forgings with large modulus require a deeper quenched layer, it is necessary to increase the low temperature cooling rate.For quenching oil, generally speaking, the steam film stage of oil is short, the cooling rate of medium temperature is fast, and the cooling rate of low temperature is fast, so it can often obtain high and uniform quenching hardness and enough quenching depth.
High core hardness after quenching: this kind of problem may be related to the selected medium cooling rate too fast or the medium low temperature cooling rate is too high.One solution is to change the quenching oil to meet the requirements.The other way is to contact the quenching medium manufacturer and add appropriate additives to reduce the cooling rate of the quenching oil at medium and low temperature.The third way is to use steel with lower hardenability.
Quenching deformation problem: quenching deformation makes many factories hurt their brains.According to custom, the solution of deformation problem usually involves multiple departments, and the solution is usually a comprehensive measure.The causes of deformation are mainly attributed to insufficient cooling rate and uneven cooling rate. On this basis, the principle and method to improve the cooling rate and achieve uniform cooling are put forward.The measures to improve the quenching cooling rate should be added to the reasonable selection of measures in the same direction of action.The quenching deformation problem of most forgings can be solved.For example, the deformation of the inner spline hole of the forgings is often caused by the insufficient high temperature and cooling rate of the selected quenching oil, or the long vapor film stage of the oil.Increasing the cooling rate of oil at high temperature and increasing the cooling rate of oil in the whole cooling process can generally solve the deformation problem of the inner spline hole.For forgings, especially for more precise forgings, it is necessary to select good isothermal graded quenching oil to control deformation.
Quenching cracking problem of forgings: this problem mainly appears in the induction heating quenching.The problem will be solved by choosing a good water-based quenching medium, such as PAG quenching medium commonly used at home and abroad, instead of tap water.PAG medium is used for induction heating and quenching.Can obtain high and uniform quenching hardness and deep and stable hardening layer, quenching crack risk is minimal.
Bright problem: where there are requirements in this respect, bright quenching oil or fast bright quenching oil should be selected.Usually, the brightness of bright quenching oil is good, the cooling rate is not high enough, and the brightness of quenching oil with high cooling rate is not good enough.In addition, the brightness of the hot oil is generally poor, you can change the new oil or add additives to improve the brightness.