Compression spring strengthening treatment
Suspension spring strengthening
Thanks to the high-stress and lightweight design, the weight of suspension springs has been greatly reduced in recent years, and it is very common that the stress of the suspension springs of new models>1000Mpa. The service of the spring under such high stress has exceeded the limit that the material can withstand, so it must be supplemented by other strengthening methods (such as shot/shot peening).
The main engine manufacturer adopts very strict test standards for automobile suspension springs. The longest test period is as long as 70 days (10 weeks). It should be a suspension spring that works under high stress conditions. Once the surface is subjected to stress corrosion That is, corrosion fatigue failure occurs. If the broken spring port punctures the tire, it may cause major safety and personal accidents.
Shot/shot peening is the most effective strengthening method for suspension springs. After proper shot peening, the fatigue life of high-stress springs can be increased by more than 5 times. At present, most suspension springs are shot/shot blasted with steel wire cut blasting. Shot peening (different pellet diameters) is commonly used. The strength and depth of the spring surface compressive stress are important indicators to measure the effect of shot peening. The surface stress of good shot peening is at least above -600Mpa, and it can reach -800Mpa at a distance of 50um from the surface. The surface pressure stress of a stress shot peening spring can reach above -800Mpa, and it can reach -1200Mpa at a distance of 50um from the surface.
At present, well-known spring manufacturers at home and abroad, such as Liaoyang Kesuo, etc., generally use a continuous pass-through type roll cage reinforcement equipment, and the workpiece is transported through a suspended conveyor chain. Each part must be in three shot blasting positions, and three shot blasting strengthening cycles are performed according to the set time. After the strengthening is completed, the throwing head stops, the discharge door is opened, the strengthened workpiece is automatically lifted out, the new workpiece enters, and the new cycle starts. The equipment’s capacity can reach 500 pieces/hour.
Leaf spring strengthening
A continuous pass-through shot blasting equipment can be used to strengthen the leaf springs one by one, so that the geometric concave surface of the leaf spring is exposed to the high-speed shot flow. A typical model includes a throwing head for projecting the top of the leaf spring, and a throwing head is installed on the side to spray the left and right sides of the leaf spring at the same time.
The passing speed of this standard leaf spring strengthening equipment is 10 feet per minute. If a higher production speed is required, the number of throwing heads can be increased and the motor frequency can be adjusted. Under working conditions, leaf springs are repeatedly affected by unidirectional bending stress, so they are sometimes stressed by stress. In the strengthening process, it is simulated that the leaf spring will be subjected to “stress strengthening” in the future use process, so that it will be shot peened while applying a “static stress” in the direction of bearing the load. After strengthening, release the applied static stress. Experiments prove that stress strengthening can further extend the service life of leaf springs than conventional strengthening.
Compression spring strengthening
Round springs, due to their spiral geometry, are harder to strengthen than flat surface leaf springs. In addition, it is necessary to strictly evaluate the strengthening effect of the circular spring cross section, so as to fully understand the resistance of the circular spring to fatigue fracture.
The round springs are individually sent to the shot blasting room via a continuous conveyor chain system. A set of parallel roller tables are installed in the shot blasting room. While strengthening, the roller table keeps rolling, driving the round springs to move forward while rotating. This way of rotation allows the high-speed pill flow to pass between the rings of the circular spring and hit the metal surface of the inner ring, where the stress of the circular spring is most concentrated.
For applications with high productivity requirements, an enhanced device that can spray two round springs at the same time can be selected. The latest research and development result is based on the original shot blasting equipment, combined with multiple nozzles, used for more targeted and concentrated shot peening for specific areas of the round spring (stress concentration to please).