Due to the limitation of product structure, multi strand spring has the characteristics of high strength and good performance. The material is required to guarantee the final performance in spring strength and toughness. In the process of processing multi strand spring, the following points should be paid attention to:
1. Cold and hot methods can be selected for supporting ring according to product requirements. It is not allowed to heat the spring to spark or whiten by hot bonding method, and the temperature of silicon manganese steel shall not be higher than 850 ℃. The bearing ring and the effective ring shall be in effective contact, and the clearance shall not exceed 10% of the nominal clearance between rings.
2. The characteristics of multi strand spring can be determined by adjusting lead, and the cable distance can be adjusted when winding. The screw pitch can be 3 ~ 14 times of wire diameter, but generally 8 ~ 13 times is better. The spring force is also closely related to the free height, the end coil, the outer diameter and the properties of the steel wire, which can be changed by adjusting one or more of them.
3. The spring head shall not be welded for the spring without supporting ring and the spring with too small steel wire diameter, but the end wire rope shall not be obviously loose and burr shall be removed. The length of the welding part of the multi strand spring to be welded shall be less than 3 times of the cable diameter (the longest length shall not be greater than 10 mm). The heating length should be less than one circle, and it should be polished smoothly after welding. The welding parts should be annealed at low temperature during gas welding.
4. Generally, the surface treatment of spring can be done by phosphating or other treatments. When zinc and cadmium are to be plated, dehydrogenation treatment shall be carried out after electroplating, and 3% (no less than 3 pieces) shall be taken for retest after dehydrogenation, and there shall be no fracture during retest. The surface dirt, salt mark and oxide scale should be removed by sand blowing or gasoline cleaning, but acid washing is not allowed.
5. The compression time of the important spring is 24 hours, and that of the ordinary spring is 6 hours or 3-5 times continuously, holding for 3-5 seconds each time. The clearance between the spring and the mandrel should be 10% of the mandrel diameter. If the clearance is too small, it is difficult to operate. If the clearance is too large, it is easy to cause the spring to bend and deform. If one of the springs is broken during pressing, the rest should be treated again.