JPS59133326A - Steel wire for spring having superior sag resistance and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a steel wire for a spring having superior sag resistance without increasing the strength by hardening and tempering a steel wire for a spring contg. a specified amount of C, heating the wire to the tempering temp. or below, producing a strain, and quenching the wire to ordinary temp. CONSTITUTION:A steel wire 2 for a spring contg. 0.5-0.7wt% C supplied from a supplier 1 is sent in the direction of an arrow with pinch rolls 3 for sending. The wire 2 is nearly straightened with a straightener 4 and sent to a heater 6 with pinch rolls 5 for sending. The wire 2 is heated to the hardening temp. and cooled in a cooling vessel 7, and the hardened wire 2 is sent to a heater 9 with pinch rolls 8 for sending. The wire 2 is heated to the tempering temp. and cooled to ordinary temp. in a cooling vessel 10. The wire 2 is sent to a heater 13, heated to the tempering temp. or below, and subjected to plastic working or straightening at the temp. with a working device 14 to produce >=10% strain. The wire 2 is then quenched to ordinary temp. with a cooler 15 and coiled around a coiler 17.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a spring steel wire with excellent fatigue resistance used in vehicle suspension springs, etc., and a method for manufacturing the same.

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

Conventionally, JIS SUP 6 to 7 was used for such spring steel wires.
and 5AE9254. However, there is a need to reduce the weight of vehicles in order to save energy, and one of these demands is a steel wire for springs with excellent fatigue resistance. That is, if a spring steel wire with excellent resistance to fatigue could be developed, it would be possible to further increase the design stress, and as a result, the weight of the coil spring could be reduced.

In order to improve this resistance to sagging, attempts have been made to increase the strength through various heat treatments, but if the strength is increased unnecessarily, the problem is that the increased strength results in a lack of toughness such as elongation and drawing. There is. In addition, increasing the strength of the steel wire increases its susceptibility to minute scratches and internal defects on the surface of the steel wire, leading to practical problems such as a lack of reliability such as easy breakage during processing or use.

The inventors of the present invention have conducted various studies aimed at obtaining a spring steel wire with excellent resistance to fatigue without increasing the strength, and as a result, they have succeeded in achieving their objective.

(C) Disclosure of the Invention A feature of the present invention is that after quenching and tempering, the steel wire is heated to a temperature below the tempering temperature, and the strain amount is 1 in the temperature range.
This is a spring steel wire with excellent fatigue resistance and a method for manufacturing the same, which consists of applying strain by adding 0% or more plastic working or straightening, and then rapidly cooling to room temperature.

The reason for limiting the carbon content of this steel wire to 0.5 to 0.7% is that if the aim is to reduce the weight of the vehicle and improve its resistance to fatigue, it is necessary to give the steel wire sufficient strength. However, if the carbon content is less than 0.5%, sufficient strength cannot be obtained;
This is because the toughness is inhibited in the above case.

The spring steel wire of the present invention is manufactured as follows. 1st
The figure is a schematic diagram showing the process.

The wire 2 supplied from the supply 1 is sent in the direction of the arrow by a feeding pinch roller 3, straightened into a substantially straight line by a straightening machine 4, and then sent to a heating device 6 by a second feeding pinch roller 5. Here, the wire rod is heated to a quenching temperature determined by the steel type of the steel product, cooled in a cooling tank 7 to complete the quenching process, and then immediately transferred to a heating device 9 by a third feeding pinch roller 8. It is sent, heated to a tempering temperature, and cooled down to room temperature in a cooling bath 10.

A feature of the present invention is that after the quenching and tempering treatments are completed, the steel wire is heated to a temperature below the tempering temperature by the heating device 13, and in that temperature range, the processing device 14 is used to reduce the amount of strain to 10.
% or more by plastic working or straightening, and then rapidly cooled to room temperature by a cooling device 15 and wound up by a winding machine 17 by a feeding pinch roller 16. It has been found that the steel wire 18 manufactured in this manner is a spring steel wire with significantly improved resistance to fatigue. In the above, the heating device 13, the processing device 14, and the cooling device 15 may be used in tandem with the previous quenching and tempering process, or the quenching and tempering process may be heated and processed separately. good.

Depending on the processing method and amount of processing, the steel wire may undergo work hardening and its strength will significantly increase, so heat treatment conditions must be determined appropriately to obtain the desired strength depending on the steel type, processing method, and amount of processing. .

Although the heating processing apparatus 12 has a processing apparatus 14 after heating in FIG. 1, the steel wire of the present invention can be obtained even if the heating-processing-heating process is performed.

Next, an example will be explained.

B) Best Mode for Carrying Out the Invention Example 1 SAE 9254 (C: 0.56 wt%
, si: 1.37 wt%, Mn: 0.7 wt%
, Cr: 0.59wt%), and a wire drawing die was used as the processing device 14 to give processing strain. The quenching temperature at this time is 970°C1, the tempering temperature is 465°C1, and the area reduction rate of the steel wire is 20%, and the heating temperature during processing is 450°C.
The wire diameter after C processing was 9.5 mmφ, and the tensile strength of the steel wire after processing was 185 kg/12.

The steel wire produced in this manner was processed into a coil spring and subjected to a static test for resistance to fatigue. For comparison, 9
．． 5 or butt φ 5AE9254. And the tensile strength is 1 after normal quenching and tempering treatment (no processing) of SUP 7.
85K! A coil spring with the same specifications was fabricated using a steel wire that was adjusted to have a speed of 1/min.

The specifications of the coil spring are as follows.

Wire diameter: 9.5mm φ Coil average diameter: 60flφ Free height: 2600 current Effective number of turns: 4.25 Total number of turns: 6.25 After setting with a stress of 1'lQKg/M2 using this, A constant load was continuously applied for 100 hours so that the test stress was 115 Kg/rtmQ, and a settling test was conducted at room temperature. Table 1 shows the results.

Table 1 As shown in Table 1, the spring steel wire according to the present invention was found to have extremely superior fatigue resistance compared to conventional products.

Example 2 The same 5AE9254 as in Example 1 was used as a test material, and a straight roll was used as a processing device to apply distortion while processing.

At this time, the quenching temperature is 970°C1 and the tempering temperature is 435°C.
The maximum bending strain is 2.1%, and the heating temperature during processing is 410℃.
“Wire diameter after C1 processing: 9.5#+711φ, tensile strength: 2
00 Ky/M”.

A coil having the same specifications as in Example 1 was prepared using this copper wire, and a test for resistance to settling at room temperature was conducted.

Again, the same type of steel wire 5AE9254.5UP7 is used as a comparison product.
A 9.5 diameter steel wire having a tensile strength of 2 o Ky/#L2 was prepared by ordinary quenching and tempering treatment, and a coil of the same shape was produced. After setting with a stress of 125Kg/M2, a constant load was applied continuously for 100 hours so that the test stress was 115 kg/mx2, and a fatigue resistance test was performed at room temperature.The results are shown in Table 2. show.

As shown in Table 2, it can be seen that the product of the present invention is more than twice as good in resistance to settling as the comparative product.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a method for manufacturing the product of the present invention. 1: Supply, 2: Wire rod, 3, 5.8.11.16: Pinch roll for feeding, 4=
Straightening machine, 6.9.13 : Heating device, 7.10.15
: Cooling tank, 14 = Processing equipment, 12: Heating processing equipment, 17
: Winding machine, 182 invention steel wire. 147

Claims (1)

[Scope of Claims] (1) After quenching and tempering a spring steel wire with a carbon content of 0.5 to 0.7% by weight, the steel wire is heated to a temperature below the tempering temperature and strained at that temperature. A steel wire for springs having excellent resistance to setting, characterized in that the steel wire has been subjected to plastic working of 10% or more or straightening to create distortion, and then rapidly cooled to room temperature to impart resistance to setting. . (2. The steel wire for springs according to claim (1), which is processed by cold forming and is used for suspensions for vehicles. The steel wire for springs has excellent sag resistance. ( 3) In the manufacturing method of spring steel wire, the carbon content is 0.5 to 0.
．． A 7% by weight steel wire is quenched and tempered, then heated to Kundem or separately below the tempering temperature, and then subjected to plastic working with a strain of 10% or more at that temperature, or subjected to straightening to give it strain. A method for producing spring steel wire with excellent resistance to settling, which is characterized by rapid cooling to room temperature.