HEAT TREATMENT

Stress - Relieving / Heat Treatment:- There is a lot confusion observed by us, amongst many of our customers that stress reliving is necessary or not. We recommend that all spring material should be subjected to a stress-relieving operation after forming. In the case of cold drawn spring steel this would be at a temperature between 220°C and 350°C for 2 minute to 1 hour depending on the type of row material size of the wire types of spring and its application. The objective of this is to reduce the stresses introduced during coiling especially in the case of compression and extension spring as these stresses are not beneficial. Stress reliving also slightly increases the elastic limit of the material and stabilizes the spring dimension. The problem with stress reliving that as the coiled in stresses are removed the spring will rotate and move and this leads to dimensional change. This dimensional change has to be taken into account by the spring maker before coiling. Heating small torsion spring after coiling to relieve the stresses is often omitted.

Surface Treatment:- When the spring operates in a corrosive environment some from of surface protection is required. Depending on the application this can take a number of from. Obviously the spring can be designed using material that will not readily corrode in the application working environment but this may not be possible when costs have to be kept down or where the material needs to be of a required strength. Stainless steel alloy in particulars are excellent for corrosion resistance but the cost of the material can be prohibitive. The simplest method is to simply oil the spring. This should give sufficient corrosion protection for spring in transit or in storage or general use provided the conditions are not very corrosive.