A spring is a mechanical part that uses elasticity to work. Generally made of spring steel. Its elasticity can be used to control the movement of parts, mitigate impact or vibration, store energy, measure force, etc. Widely used in machines and instruments. Therefore, springs are often heat treated using ultrasonic induction heating equipment to meet their working needs. The spring is bent from 60Si2Mn steel wire with a diameter of 2mm. The process flow is: steel wire annealing-straightening-forming-quenching, tempering-galvanizing-finished product inspection. During production, it was discovered that there were many cracks in the axial direction of the finished steel wire, with lengths up to 20mm, widths up to 0.2mm, and a maximum depth of 0.6mm. There were also a small number of cracks in the radial direction, causing some products to be scrapped. Today, we will talk about the causes of spring breakage defects and their preventive measures.
The chemical composition of spring raw materials meets technical requirements. Metallographic inspection revealed that there were spherical or dot-like graphite in the material matrix, which was unevenly distributed. After the workpiece was straightened, it was found that there were obvious scratch defects with shallow depth. The spring quenching process is oil cooling at 860℃ for 4x45min, and the spring surface is sprayed with anti-oxidation paint. The tempering process is 460℃xlh air cooling. After heat treatment, a small amount of axial and radial cracks were found in the workpiece. Cross-sectional inspection revealed that some cracks were severely oxidized. This indicates that these cracks were formed before quenching.
Based on the above analysis, the following improvement and prevention measures are proposed:
(1) When using ultrasonic induction quenching equipment for quenching and tempering heat treatment, we should adopt reasonable quenching and tempering processes to prevent oxidation and decarburization of the parts, and should be protected during quenching and heating.
(2) Improve the alignment process so that there are no scratches and other defects on the spring surface, and prevent surface scratches from causing cracks in the workpiece.
(3) Strictly control the quality of raw materials and use 60Si2Mn steel materials without spherical or point-like graphite.
Fracture defects are common and serious defects in the heat treatment of workpieces. They greatly reduce the service life of the workpiece, and even cause the workpiece to be scrapped, resulting in a waste of resources. After many manufacturers adopt the above improvements and preventive measures, the spring crack defects are solved, the quality of the workpiece is excellent, and the production is normal.
en 
cn 
jp 
ko 
de 
es 
it 
ru 
pt 
vi 
th 
pl 
GS-ZP-1200
