1. Do not blindly mark the hardness requirements of heat treatment HRC on the spring drawings.
Commonly used small springs commonly used spring steel wire is the cold drawn steel wire of Paidengtuo <lead-dissolved austempering heat treatment>. Usually, the diameter of this kind of steel wire is less than 10 mm. This kind of steel wire is comprehensively strengthened by heat treatment and cold drawing, and has the mechanical strength required by the spring material. But its surface hardness is not high, generally only HRC30-35. After the spring is formed, it can be used only after stress relief and tempering. National standards GB4357-89 and GB4358-89 both give the mechanical properties of this type of steel wire.
Another type of spring is made of soft “annealed” steel wire or steel plate, then it needs to be heat treated, quenched and tempered, and the surface has a certain hardness to meet the requirements of spring performance. The drawings of this type of spring can be marked with HRC hardness requirements .
2. Do not increase the number of spring detection points randomly.
Randomly indicate more than two points or even up to eight load detection points on the spring drawing, which will only greatly increase the manufacturing cost of the spring and reduce the qualification rate. If it is not a special requirement, the general spring only needs 1-2 load detection points in mechanical transmission. In fact, due to the characteristics of the spring’s geometric structure, the geometrical size error and heat treatment springback deformation error existing in the spring production will affect the actual load of the spring. Make the actual load-deformation is not a straight line. The best design should be under the premise of meeting the requirements of mechanical transmission, testing a little working point load, and ensuring a certain installation elasticity.
3. For springs that require service life> 104 or more, the fatigue life of the spring should be checked. Especially for springs that require a life of more than 106, life checking is required. Generally speaking, the smaller the working stress and the smaller the working amplitude, the longer the service life. Therefore, for springs with long life, sufficient space should be reserved as much as possible in the mechanical structure design. Reduce the stress amplitude of the spring work as much as possible and reduce the limit working stress of the spring. Different spring materials allow different fatigue limit stresses. Customers can refer to other design materials. In order to improve the life of the spring, special techniques such as shot peening and strong pressure can be adopted. These strengthening methods can increase the fatigue life by 15%-25%.