Spring steel wire rod excellent in pickling performance

Abstract

A spring steel wire rod according to the present invention is a spring steel wire rod wherein: the spring steel wire rod contains C: 0.35% to 0.7% (by mass, the same is hereunder applied), Si: 1.5% to 2.50%, Mn: 0.05% to 1.0%, Cr: 0.05% to 1.9%, Cu: 0.05% to 0.7%, Ni: 0.15% to 0.8%, P: 0.02% or less (excluding 0%), S: 0.02% or less (excluding 0%); and the balance being Fe and unavoidable impurities, wherein the ratio of Si to Cu (Si / Cu) is in the range of 4 or more; and the difference between the concentration of Cu in the surface layer and the concentration of Cu in the steel is 0.50% or less and the difference between the concentration of Ni in the surface layer and the concentration of Ni in the steel is 1.00% or less. The present invention makes it possible to improve pickling performance in a spring steel wire rod containing Si abundantly and further Cr, Cu, and Ni.

Description

technical field [0001] The present invention relates to a spring steel wire rod having excellent pickling performance, and more particularly, to a technique for improving the pickling performance of a spring steel wire rod rich in Si and also containing Cr, Cu, and Ni. The spring steel wire according to the present invention is advantageously used for: valve springs for engines of automobiles and the like; clutch springs; brake springs; suspension springs such as stabilizer springs or torsion bar springs; and other applications. technical background [0002] The chemical composition of spring steel used for valve springs, suspension springs, etc. is specified in, for example, JIS G3565 to JISG4801, and an appropriate steel type is employed according to the type of spring design. In recent years, as the size and weight of springs have decreased with the reduction of exhaust gas and fuel consumption, the design stress of springs has increased, and it is desirable to provide, f...

AI Technical Summary

Problems solved by technology

[0010] As described above, although spring steel wires rich in Si as well as Cr, Cu, and Ni are mainly used in order to improve yield stress and corrosion fatigue resistance, there is concern that in the case of such spring steel wires, Cu-enriched At the interface between scale (especially fayalite) and the base steel, thus degrading the pickling properties

[0011] However, methods for sufficiently improving the pickling properties of such spring steel wires have not been disclosed

The aforementioned JP-A 223523 / 2004 describes a method for preventing surface cracks due to Cu enrichment without adding a large amount of Si, and by this technique, the improvement of yield stress by adding Si cannot be obtained

At the same time, as pointed out in the "Prior Art" section of the above-mentioned JP-A 223523 / 2004 proposed later, the problem in the above-mentioned JP-A 297026 / 1994 is that the iron scale of the steel material added with Si has poor separability; Even if high-pressure water descaling is performed before rolling, the scale is difficult to be peeled off and removed; the surface properties are degraded, such as scale remains and the surface of the steel becomes red; It hardly dissolves in the pickling process, therefore, the cost of the pickling process increases and the productivity decreases

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