JPS59229415A - Manufacture of steel wire for spring with superior sag resistance - Google Patents

Abstract

PURPOSE:To manufacture a steel wire for a spring with superior sag resistance without increasing the strength by hardening and tempering a steel wire rod contg. a specified amount of carbon and by applying a tensile strain to the rod while heating the rod as required. CONSTITUTION:A steel wire rod 2 contg. 0.5-0.7wt% C supplied from a supplier 1 after hardening and tempering is heated to a temp. below the tempering temp. with a heater 5 while applying a tensile strain with strain appliers 3, 4. The rod 2 is quenched to room temp. in a cooling vessel 6 and coiled around a coiler 7 to obtain a steel wire 8 for a spring with high toughness and improved sag resistance without increasing the strength. The wire 8 is suitable for use as the material of a suspended spring for a vehicle.

Description

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

←）Technical background Steel wires for vehicle suspension springs have issues such as fatigue resistance and relaxation value. Here, "deformation" is a phenomenon in which a coil spring undergoes permanent deformation during use, and its free height changes. Conventionally, steel wires for springs like this have been manufactured using JIS standards.
Although steel wires of steel grades such as SUP6-7 and SAE 9254 are used, there is a demand for a lighter weight of vehicles to save energy, and one of them is the demand for spring steel wires with excellent fatigue resistance. ing. 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 sensitivity to minute eaves and internal defects on the surface of the steel wire, resulting in practical problems such as a lack of reliability such as easy breakage during spring 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 The feature of the present invention is that after quenching and tempering, the steel wire is heated below the tempering temperature while applying tensile strain, and then rapidly cooled. It is manufactured in the following manner. FIG. 1 is a schematic diagram showing the process. The steel wire 2 that has been quenched and tempered is transferred to a strain imparting device 6
.

It has been found that the steel wire 8 manufactured in this manner is a spring steel wire with significantly improved resistance to fatigue.

1, the cooling tank 6 is located in front of the strain applying device 4 in FIG. 1, but it may be located after this.

Further, the normal hardening and tempering treatment and the main treatment may be performed in tandem, or may be performed off/ine. Next, an example will be explained.

B) Best Mode for Carrying Out the Invention Embodiment 1 Two sets of two caterpillars rotating in the same direction while being in pressure contact with each other are arranged at intervals between the tensile straining devices 6 and 4, and one set is located on the exit side. The caterpillars are configured to be driven at a faster circumferential speed than the set of caterpillars on the entrance side. Figure 2 shows an example of this device, and on the entrance side AB2
A steel wire 2 is sandwiched between a pair of caterpillars consisting of strips, and the steel wire 2 is fed while being held by caterpillars A and B so that it does not slip even when tension is applied as shown by the arrow. The steel wire rotates the caterpillar CD faster than the caterpillar AB so that a tensile strain is applied between the tracks AB and CD. During this time, it is heated to the tempering temperature by the heating device 5 and cooled to room temperature in the cooling bath 6.

A tensile strength of 200 kg is used as a test sample using the above-mentioned equipment.
/, 417) SAE 9254 Oilte”y bar wire (0,56wt%C, 1,37wt%Si, 0.7
0wt%Mn, 0.59wt%Cr) was used to perform annealing treatment while reducing tensile strain.

Further, tensile strain amounts of 1.2%, 2.5%, and 6.2% were given. The steel wire produced in this manner was processed into a coil spring and subjected to a static test to test its resistance to fatigue. For comparison, SAE 9254 and SUP 7 were subjected to normal quenching and tempering treatment, and the tensile strength was 2゛00kg/I.
The specifications of the coil spring are as follows: A coil spring with the same specifications was made using a steel wire made to have a diameter of 1.

Wire diameter: 9.5. m Coil average diameter = 600 Free height: 2600 Effective number of turns: 4.25 Total number of turns: 6.25 After setting with a stress of 125 kg/ll using this, set the test stress to 120 kg/d. Table 1 shows the results of a settling test at room temperature under which a constant load was applied continuously for 100 hours.

5-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.

Embodiment 2 Two capstans are used as the tensile strain imparting devices 3 and 4, and the capstan on the exit side is configured to be driven at a faster circumferential speed than the capstan on the inlet side. 6th
The figure shows an example of this device, in which capstan F is rotated faster than capstan E so that a tensile strain is applied to the steel wire between capstans E and F. During this time, it is heated to the tempering temperature by the heating device 5 and cooled to room temperature in the cooling bath 6. This treatment was carried out while applying tensile strain using the same SAE 9254 as in Example 1, which had a tensile strength of 185 to 9/, as the test material, using an apparatus as described in 1 above. Tensile strain amount: 1.2%, 2.5%, 3.2
% was given. A coil spring with the same specifications as in Example 1 was prepared using this steel wire and tested for resistance to settling at room temperature. As a comparative product, 5AE9254.5UP7 steel wire was subjected to normal quenching and tempering treatment to have a tensile strength of 185", 4'
We prepared a coil with the same shape as above. 1 of these
After setting 25 with a stress of 7+,', a constant load was applied continuously for 100 hours so that the test stress was 120''/, l, and a fatigue resistance test was conducted at room temperature. Table 2 shows the results. Shown below.

Table 2 As shown in Table 2, it can be seen that the product of the present invention is significantly superior in fatigue resistance compared to the comparative product. As is clear from the above examples, the steel wire of the present invention can be used for springs with excellent fatigue resistance without increasing the strength or using expensive special metals as in the conventional manufacturing method of oil tempered wire. Steel wire can be manufactured. It has also been found that the steel wire of the present invention is useful for weight reduction when used in cold-worked vehicle suspension springs.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 6 are all diagrams for explaining the present invention in detail. 1: Supply, 2: Wire rod, 3, 4: Strain imparting device. 5: Heating device, 6: Cooling tank, 7: Winding machine, 8: Steel wire of the present invention, A, B, C, D: Caterpillar, E, F8- Item 1' 2nd Procedural Amendment 1982 July/7th Japan Patent Office Commissioner Manabu Shiga 1, Indication of the case 1982 Patent Application No. 103027 2, Name of the invention Manufacturing method of steel wire with excellent resistance to fatigue (3, amendment) Relationship with the case involving the person who filed the patent application Person name: 5-15 Kitahama, Higashi-ku, Osaka Name (21
3) President of Sumitomo Electric Industries, Ltd. Tetsubu 4, Agent address: Inside Sumitomo Electric Industries, Ltd., 1-1-3 Shimaya, Konohana-ku, Osaka (telephone: Osaka 461-1031) 5. Voluntary amendment of the date of the amendment order 6. In the specification to be amended, the claims column and the detailed description of the invention column. 7. Contents of the amendment (1) The claims are corrected as shown in the attached sheet. (2) In the specification, page 2, lines 2 to 3, "relaxation" is corrected to "relaxation." Claim r(1) In a method for manufacturing a spring steel wire containing 0.5 to 0.7 wt% carbon and manufactured by quenching and tempering, after the quenching and tempering treatments are performed. , the steel wire is heated below the tempering temperature while applying tensile strain, and then rapidly cooled to room temperature t3- or JLUt*JL'', 11] JL strain m,
A method for manufacturing a spring steel wire with excellent resistance to setting, characterized by imparting resistance to setting. (2. In the manufacturing method set forth in claim (1), ft.
UIJ! A method for manufacturing a steel wire for springs with excellent resistance to fatigue, which is characterized by its ability to withstand the characters ■■ [Kanri Hunri Fake - Use 11 ■ 櫃Re 1 Song]. ”

Claims (1)

[Claims] (1) In a method of manufacturing a spring steel wire containing 0.5 to 0.7 wt% carbon and manufactured by quenching and tempering, the steel wire is A method for producing a spring steel wire having excellent resistance to setting, characterized by heating the wire to a temperature below the tempering temperature while applying tensile strain, and then rapidly cooling it to room temperature to impart resistance to setting. (2. A method for manufacturing a spring steel wire with excellent resistance to fatigue, characterized in that the manufacturing method described in claim (1) is cold-open molding, and is used for a vehicle suspension.