Development of a method of non-destructive testing of springs using magnetic structural analysis

Abstract

The article examines the relationship between hardness, residual deformation under load and coercive force of springs of rolling railway transport. According to the results of spring tests for residual deformation under load, it was established that the optimal structure of springs is tempering troostite. It is the structure of the tempering troostite that ensures optimal elastic properties of spring steels under conditions of alternating loads. It has been proven that instead of hardness and residual deformation measurement procedures, the coercive force measurement procedure of springs can be used to control the quality of springs. Coercive force, like hardness, is a structurally sensitive parameter. The introduction of magnetic structural analysis into the production process instead of hardness measurement and spring tests for residual deformation allows to significantly simplify the spring quality control procedure. It was established that the presence of a decarburized layer on the surface of the springs practically does not affect the coercive force of the springs, provided that the thickness of the decarburized layer does not exceed the values regulated by the current standard. Therefore, a certain, but not very significant decrease in the coercive force of the springs in relation to the recommended values may indicate the presence of a decarburized layer of excessive thickness on the surface of the springs. The presence of cracks on the spring surface does not affect their coercive force, regardless of the nature of the cracks and the mechanisms of their formation. The coercive force of the springs depends exclusively on their structure, which is determined by the heat treatment regime. It has been proven that the optimal hardness of springs and the coercive force corresponding to this hardness can be established only based on the results of preliminary tests of springs for residual deformation under load. It is the residual deformation under load that is the main operational characteristic of springs, which determines the possibility or impossibility of their use in certain conditions. Thus, the results of the research make it possible to establish the relationship between the operational characteristics and the structure of the springs and to develop, on the basis of this relationship, a method of non-destructive control of the structure of the springs in the conditions of mass production.