Strengthening treatment of compression spring

Strengthening and treatment of compression spring
It is difficult to strengthen the surface of the spiral spring because of its flat surface. In addition, the strengthening effect of the cross section of the circular spring must be strictly evaluated, so as to fully understand the resistance of the circular spring to fatigue fracture.

The round spring is sent to the shot blasting chamber one by one through a continuous conveying chain system. A group of parallel roller tables are installed in the shot blasting chamber. While strengthening, the roller table keeps rolling to drive the round spring forward while rotating. In this way, the high-speed shot flow can pass through 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 capacity requirements, a kind of strengthening equipment that can spray two round springs at the same time can be selected. The latest research and development result is that on the basis of the original shot blasting strengthening equipment, a number of nozzles are combined to achieve more targeted and centralized shot peening for the specific area (stress concentration to please) of the circular spring.

Leaf spring strengthening
A continuous through shot blasting equipment can be used to strengthen the leaf spring one by one, so that the geometric concave surface of the leaf spring is exposed to the high-speed shot flow. A typical model consists of a projectile head for ejecting the top of the leaf spring, a projectile head is installed on the side, and the left and right sides of the leaf spring are sprayed at the same time.

The standard leaf spring intensifier has a passing speed of 10 ft / min. if higher production speed is required, the number of burners can be increased and the motor frequency can be adjusted. Under working conditions, leaf spring is repeatedly affected by unidirectional bending stress, so it is sometimes strengthened by stress. In the process of strengthening, it is simulated that the leaf spring will be subjected to “stress strengthening” in the later use process, so that it is applied with a “static stress” in the direction of bearing load, and at the same time, it is shot peened. After strengthening, the static stress is released. The experimental results show that the service life of leaf spring can be further prolonged by stress strengthening than by conventional strengthening.

Suspension spring reinforcement
Due to the high stress lightweight design, the weight of suspension spring has been greatly reduced in recent years. It is very common for new type suspension spring with stress > 1000MPa. The spring service under such high stress has exceeded the limit that the material can bear, so it must be supplemented by other strengthening means (such as shot blasting / shot peening).

The main engine manufacturer adopts a very strict test standard for automobile suspension spring. The longest test cycle is as long as 70 days (10 weeks). The original reason is that once the surface of suspension spring working under high stress condition is subjected to stress corrosion, corrosion fatigue failure will occur. If the broken spring end pierces the tire, it may cause major safety and personal accidents.

Shot peening / shot peening is the most effective strengthening method for suspension spring. After proper shot peening, the fatigue life of high stress spring can be increased by more than 5 times. At present, steel wire shot blasting is mostly used in suspension spring shot peening, and multiple shot peening (different shot diameter) is widely used in technology. The compressive stress intensity and depth of spring surface are important indexes to evaluate shot peening effect. A good shot peening surface stress is at least – 600MPa and – 800MPa at 50um away from the surface. The surface compressive stress of stress shot peening spring can reach – 800MPa and – 1200Mpa at 50um away from the surface

At present, well-known spring manufacturers at home and abroad, such as Liaoyang Kesuo, widely use a continuous through roll cage strengthening equipment, and the workpiece is transported through a hanging conveyor chain. Each part must be in three shot blasting positions, according to the set time for three shot blasting strengthening treatment cycles. After strengthening, the throwing head stops, the discharge door opens, the strengthened workpiece is automatically lifted out, the new workpiece enters, and the new cycle begins. The capacity of the equipment can reach 500 pieces / hour.