Metal springs deform during heat treatment

1、 What are the main reasons for the deformation of metal springs during heat treatment?
(1) I believe everyone who frequently orders springs knows that springs sometimes deform during heat treatment. So, what are the main reasons for this situation? In fact, the main reason for the shape change of the parts in the conventional heat treatment of Dongguan hardware springs is the thermal stress and phase transformation stress during the heat treatment and quenching process. If the heating speed is too fast, the parts are too large compared to the heating furnace, and the temperature of each part is different, it will cause thermal deformation. During the insulation process, residual stress will be released, resulting in deformation, and the weight of the parts will also cause deformation.
(2) During the cooling process, due to the different cooling rates of different parts of the component, thermal stress will be formed, causing deformation of the component. Even if the cooling rate is the same, surface cooling is always fast and center cooling is always slow. Therefore, the phase transition surface causes plastic deformation in non phase transition centers. If alloy composition segregation or decarburization occurs on the material surface, the phase transition stress is more uneven and more likely to cause part deformation. In addition, if the thickness of the parts is uneven, the cooling rate will also be different.
(3) In the heat treatment of forgings, the parts that reduce deformation are placed in the following ways: first, they are suspended vertically as much as possible; second, they are placed vertically at the bottom of the furnace; third, they are supported horizontally by two points, with the fulcrum position between one-third and one-quarter of the total length; fourth, they are placed horizontally on heat-resistant steel tools. During the cooling process of parts, the type of quenching medium, cooling performance, and hardenability are related to deformation. The change in cooling performance can be adjusted by changing viscosity, temperature, liquid pressure, using additives, stirring, etc. The higher the viscosity and temperature of quenching oil, the smaller the elliptical deformation. When static, the deformation is small.
2、 What methods can effectively reduce deformation
(1) Salt bath quenching;
(2) High temperature oil quenching;
(3) QSQ method;
(4) Decompression quenching;
(5) One bath three-level quenching.
(6) Salt bath quenching is similar to high-temperature oil quenching, both quenching at the martensitic transformation temperature to increase the uniformity of martensitic transformation. Qsq is double liquid quenching. Reduced pressure quenching is the process of lowering the liquid pressure of the quenching medium, thereby extending the number of stages of the steam film, lowering the cooling rate in the high-temperature zone, and achieving uniform cooling rates in all parts of the component. The structure of one bath three-stage quenching is simple. Firstly, cool the parts from the quenching temperature oil to a temperature slightly above the MS point, then remove them from the furnace and store them in the atmosphere to ensure uniform temperature of the parts as a whole. Then, cool the parts with oil to ensure even martensitic transformation and greatly improve deformation irregularity.