JPS5956520A - Production of steel wire for spring having excellent settling resistance - Google Patents

Abstract

PURPOSE:To obtain a steel wire for a spring having excellent settling resistance to be used as a cold formed suspension spring for automobiles by tempering a wire rod which has completed a hardening treatment while applying working strain free from deformation with straightening rolls. CONSTITUTION:A wire rod 2 is set roughly to a linear shape with a setting machine and is then fed to a heater 6, where the wire rod is heated. The heated wire rod is cooled in a cooling tank 7 and thus the hardening treatment is completed. The hardened wire rod 2 is immediately fed to a heater 10 where the wire rod is heated to a tempering temp. The wire rod is tempered while working strain free from deformation is applied thereon by straightening rolls 11 or the like and the tempered wire rod is cooled down to an ordinary temp. A steel wire 15 for a spring having excellent settling resistance to be used for a cold formed suspension spring for automobiles is obtd. by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a method for producing a spring steel wire with excellent fatigue resistance 11 used in automatic suspension springs and the like.

(b) Background of the Technology Steel wires for small automatic suspension springs have problems such as fatigue resistance and reluffation value. Here, "settling" is a phenomenon in which the coil undergoes permanent deformation during use, and its free height changes.

Conventionally, steel wires of steel grades such as 11S (5 to 7 and 5AE9257!I) have been used for such spring steel wires, but there is a demand for light fittings for vehicles to save energy. As one of these, there is a demand for a spring steel wire with excellent fatigue resistance.In other words, if a spring steel wire with excellent fatigue resistance can be developed, the design stress can be further increased. As a result, the weight of the coil spring can be reduced.

In order to improve this resistance to fatigue -1-, attempts have been made to increase the strength through various heat treatments, but if the strength is increased unnecessarily, the increased strength may result in a lack of toughness such as elongation and drawing. There is a problem with doing so. In addition, the increased strength increases the sensitivity to minute eaves and internal defects on the surface of the steel wire, resulting in
The fact is that it lacks reliability, such as being easily damaged during operation or use.
There was a problem with D-1-.

The inventors of the present invention achieved the objective as a result of carrying out various tests on a 1-1 basis to create a spring steel wire with excellent fatigue resistance without reducing its strength. It was successful.

DISCLOSURE OF THE INVENTION The feature of the present invention is to provide a spring steel wire with excellent fatigue resistance, which is made by subjecting it to quenching and then tempering it using stretching rolls to remove the strain caused by bending. This is the manufacturing method.

The spring steel wire of the present invention is manufactured as follows. 1st
The figure is a schematic diagram showing the process. The wire A2 supplied from the supply 1 is sent in the direction of the arrow by the feeding pinch roller, and after being straightened into a straight line by the straightening machine 4, it is sent to the second straight line.
It is sent to the heating device B by the feed pinch roller 5. At this point, the wire is heated to a quenching temperature determined by the type of steel of the relevant steel weight, and then cooled in a cooling tank 7 to complete the quenching process.

Thereafter, the steel wire is immediately sent to a heating device 10 by the sixth feeding pinch roller 8 and heated to a tempering temperature to obtain the required strength. The feature of the present invention is this heating device 10.
During heating, the paper is bent and tempered using straight rolls 11, and then immediately cooled to room temperature in a cooling tank 12, and then wound into a winder 14 by a pinch roller 1 for feeding the paper.

It has been found that the steel wire 15 manufactured in this manner is a spring steel wire with significantly improved resistance to sagging. In -1-, the heating devices 6 and 10 may be provided with one or more induction heating coils if it is necessary to increase the heating speed, and the tempering device 11, which is a feature of the present invention, may be provided with one or more induction heating coils. Examples of processing devices include devices that press from both the vertical and horizontal directions, straight rolls that press from only one direction, or rotational straight rolls, but devices that can perform other bending processes may also be used.

Although the tempering and pressing device 9 has a processing device 11 after tempering and heating in FIG. 1, the steel wire of the present invention can also be obtained by processing such as heating-knee heating.

Depending on the method and processing described above, the steel wire may undergo work hardening and its strength will increase significantly. Conditions must be determined appropriately.

Next, an example will be explained.

B) Best Mode for Carrying Out the Invention Example 1 SAE 9254 (C: 0.56W
1%, 5i11 Rohashi [96, M, : Q, 7 w
t%, Cr: 0.59wt%) and various processing using a straight roll that is pushed in from both vertical and horizontal directions as the processing device 11]
After applying two strains, tempering treatment was performed. The quenching temperature at this time is 970'C1, the tempering temperature is 465'C1, and the maximum bending strain of the steel wire is 04%, 1.2%, and 21%, and the wire diameter after processing is 95n1φ. The tensile strength of the steel wire was 200:9/-.

First, we investigated the mechanical properties of this steel wire.

The results of the tensile test are shown in FIG.

As can be seen from the figure, as the maximum bending strain increases, elongation and drawing toughness hardly change, but σ0.2 significantly changes. In contrast, σ1ηax hardly changes.

Next, a static test was carried out by applying pressure to the coil spring from this steel wire. For comparison, 9.5 m
A coil spring with the same specifications was made using a steel wire having a diameter of SΔE9254 and a steel wire of 5UP7 which had been subjected to normal quenching and tempering treatment (without pressure) to have a tensile strength of 185 Kq/-.

The specifications of the coil spring are as follows.

Wire diameter: 95 φ Coil average diameter: 60 φ Free height: 26 CJn Shoulder Effective number of turns: 4.25 Total number of turns = 625 Using this, after sesoting at a stress of 120 to 9/-, the test stress was A constant load was continuously applied for 100 hours so that the ratio was 9/- to 115, and a settling test was conducted at room temperature. The results are shown in FIG.

In FIG. 6, the horizontal axis shows the maximum bending strain, and the vertical axis shows the residual shear strain, and it can be seen that as the strain increases, the residual shear strain becomes significantly smaller and the fatigue resistance improves.

As is clear from the following Examples, the manufacturing method of the present invention can improve the fatigue resistance without increasing the strength or using expensive special metals as in the conventional manufacturing method of oil-tempered wire. This makes it possible to produce superior steel wire for springs.

It has also been found that the steel wire of the present invention is useful for weight reduction when used in suspension springs for type 2 automobiles.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a process for explaining the present invention in detail, FIGS. 2 and 6 are diagrams explaining the present invention in detail, FIG. 2 is a diagram showing mechanical characteristics, and FIG. Showing the static sag test results. It is. 1: Subrai 2: Line shrine, 6.5.8.16: Feeding pinch roll 4:
Straightening machine, 6.10 = heating device, 7.12: cooling tank 11:
Stretching straight roll, 10: Tempering processing device, 14: Winding machine 15
: Steel wire of the present invention

Claims (1)

[Claims] (1) In the manufacturing method of spring steel wire, after quenching treatment,
A spring with excellent fatigue resistance, characterized in that a durable wire is used for cold-formed automobile suspension springs, which is characterized by being tempered while applying processing strain without deformation by straightening rolls, etc. Manufacturing method for industrial steel wire.