JPH08176730A - Oil tempered wire and production thereof - Google Patents

Abstract

PURPOSE: To provide an oil tempered wire and more particularly an oil tempered wire having excellent toughness and fatigue strength. CONSTITUTION: The steel for this wire consists, by weight%, 0.5 to 0.8% C, 1.2 to 2.5% Si, 0.4 to 0.8% Mn, 0.7 to 1.0% Cr, is added at least one kinds among 0.05 to 0.15% V, 0.05 to 0.5% Mo, 0.05 to 0.15% W and 0.05 to 0.15% Nb or above or above and consists of the balance Fe and inevitable impurities. The content of Al which is the inevitable impurity is <=0.005% and the content of Ti therein is <=0.005%. Such steel is subjected to quench-hardening and tempering at a heating temp. for quench-hardening of 950 to 1100 deg.C higher than heretofore.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil-tempered wire, and more particularly to an oil-tempered wire suitable for a spring used for a valve spring of an automobile engine and having excellent toughness and fatigue resistance, and a method for producing the same.

[0002]

2. Description of the Related Art As springs or spring steels having excellent fatigue resistance, for example, JP-A-5-320826 and JP-A-5-331597 have been proposed. However, these all contain V, Nb, and W in amounts up to 0.5 or 0.6% by weight in order to refine the crystal grains in order to improve the sag resistance, and V, Nb, and W of V, Nb, and W during quenching and heating during quenching and tempering are included. Carbide is deposited to suppress the coarsening of crystal grains. The quenching heating temperature is V
Temperatures exceeding 1000 ° C are not preferable because a large amount of carbides and the like are suppressed and coarsening of crystal grains is suppressed, and the quenching heating temperature in quenching and tempering is usually about 900 ° C, which is also 950 ° C in JP-A-5-320826. ing.

[0003]

[Problems to be Solved] However, if a large amount of V carbides and the like are present, the toughness of the oil tempered wire is greatly reduced,
There is a problem that breakage occurs frequently during spring forming. Also,
When performing nitriding treatment after spring forming, V during the nitriding treatment
Fatigue resistance can be improved by precipitating carbides and the like to increase the softening resistance. From this, it is necessary to reduce the amount of precipitated carbide during spring forming, that is, immediately after quenching and tempering, to increase the solid solution amount of V and the like as much as possible to precipitate a large amount of carbide during the nitriding treatment.

[0004]

Therefore, the precipitation of carbides such as V, Nb, and W greatly contributes to the increase in softening resistance, and the content of alloying elements that are likely to precipitate as carbides during quenching heating must be reduced to the minimum necessary amount. 0.05 to 0.15% by weight,
In addition, the quenching heating temperature is higher than conventional 950 ℃ or more 1100 ℃
It is characterized by the following.

[0005]

The reason for limiting the composition and the reason for specifying the manufacturing conditions in the steel wire of the present invention and the manufacturing method thereof will be described below. C: 0.5 to 0.8 wt% C is an essential element for increasing the strength of the steel wire,
If it is less than 0.5%, sufficient strength cannot be obtained. Conversely, if it exceeds 0.8%, the toughness decreases, and the susceptibility of the steel wire to flaws increases,
This is because reliability is reduced. Si: 1.2 to 2.5% by weight Si is an element effective for improving the strength of ferrite and improving the sag resistance. If it is less than 1.2%, there is no sufficient effect, and if it exceeds 2.5%, the cold workability is deteriorated and the hot workability and decarburization by heat treatment are promoted. Mn: 0.4 to 0.8 wt% Mn improves the hardenability of steel and fixes S in the steel to prevent its damage. However, if it is less than 0.4%, it has no effect, and if it exceeds 0.8%, toughness is increased. This is because it will decrease. Cr: 0.7 to 1.0% by weight Cr, like Mn, improves the hardenability of steel and imparts toughness by the patenting treatment after hot rolling to enhance the softening resistance at the time of tempering after quenching, and high strength. It is an effective element to turn into. This is because if it is less than 0.7%, its effect is small, and if it exceeds 1.0%, solid solution of carbides is suppressed, strength is lowered, and hardenability is excessively increased to lower toughness.

V: 0.05 to 0.15 wt% V is an element that forms carbides during tempering and increases the softening resistance, but if it is less than 0.05%, its effect is small. On the other hand, if it exceeds 0.15%, a large amount of carbide is formed during quenching and heating, which leads to a decrease in toughness. Mo: 0.05 to 0.5 wt% Mo is an element that forms carbides during tempering and increases the softening resistance, but if it is less than 0.05%, its effect is small, and if it exceeds 0.5%, wire drawing workability decreases. is there. W: 0.05 to 0.15 wt% W is an element that forms a carbide during tempering and increases the softening resistance, but if it is less than 0.05%, its effect is small. On the other hand, if it exceeds 0.15%, a large amount of carbide is formed during quenching and heating, which leads to a decrease in toughness. Nb: 0.05 to 0.15 wt% Nb is an element that forms carbides during tempering and increases softening resistance, but if it is less than 0.05%, its effect is small. On the other hand, if it exceeds 0.15%, a large amount of carbide is formed during quenching and heating, which leads to a decrease in toughness. Al, Ti: 0.005 wt% or less All of these are refractory non-metallic inclusions Al ₂ O
₃ , TiO is generated. These inclusions are hard and, when present just below the surface of the steel wire, significantly reduce the fatigue strength. Therefore, all of them are 0.0
It was less than 05%. A raw material having a low concentration of these impurities may be used.

Quenching heating temperature: 950 ° C. or more and 1100 ° C. or less The quenching heating temperature determines the solid solution amount of V and the like during quenching, and the higher the temperature, the larger the solid solution amount. V below 950 ℃
The amount of solid solution, etc. becomes small, and a large amount of carbide precipitates. Also
At 1100 ° C, most of V, W, and Nb in the present invention are considered to be in solid solution in Fe.
Even if it exceeds, the toughness is not improved and the softening resistance is not increased.

[0008]

EXAMPLES Steels having the compositions of Examples A, B, C, D and E of Table 1 and Comparative Examples F, G and H of Table 1 were melted in a vacuum melting furnace, hot forged and heat-treated. A wire rod with a diameter of 6.5 mm was obtained by hot rolling.

[0009]

[Table 1]

This is subjected to heat treatment, peeling, and cold drawing to obtain the diameter.
Processed to 4.0 mm. In addition, quenching heating temperature to these is 10
Quenching was performed at 00 ° C, and tempering treatment was performed at 420 ° C to obtain an oil tempered wire. Table 2 shows the tensile properties of each sample.

[0011]

[Table 2]

It can be seen that Examples A to E of the present invention are larger in elongation and drawing value than those of Comparative Examples F to G and are excellent in toughness. This relationship is the result of the trial made in parallel at 950 ℃
It was almost the same in the range of up to 1100 ° C.

In order to show this more clearly, Table 3 shows the difference in tensile properties depending on each quenching heating temperature in sample A.
Shown in The tendency of this difference is the same in Samples B to E as well, and in the range of 950 ° C to 1100 ° C, the elongation is 5%.
As described above, it is understood that the toughness is excellent when the aperture value is 50% or more.

[0014]

[Table 3]

[0015]

As described above, in the present invention,
By specifying the composition and the quenching heating temperature during quenching and tempering, an oil tempered wire having excellent toughness can be obtained. Further, since the softening resistance at the time of nitriding treatment after the spring forming increases, a spring having excellent fatigue resistance can be obtained. Therefore, it can be expected to be effectively used for valve springs of automobile engines, which have been improved in performance and weight in recent years.

Claims (4)

[Claims] 1. C: 0.5-0.8% by weight%, Si: 1.2-
2.5%, Mn: 0.4-0.8%, Cr: 0.7-1.0%, balance Fe and unavoidable impurities, Al content 0.005% or less, Ti content 0.005% or less An oil-tempered wire made by quenching and tempering steel, which has a quenching heating temperature of 950 ° C to 1100 ° C. 2. C: 0.5-0.8% by weight%, Si: 1.2-
2.5%, Mn: 0.4 to 0.8%, Cr: 0.7 to 1.0%,
V: 0.05 to 0.15%, the balance Fe and unavoidable impurities, and the Al content of unavoidable impurities is 0.0
An oil tempered wire made by quenching and tempering steel having a Ti content of less than 05% and a Ti content of less than 0.005% at a quenching heating temperature of 950 ° C to 1100 ° C. 3. C: 0.5-0.8% by weight%, Si: 1.2-
2.5%, Mn: 0.4 to 0.8%, Cr: 0.7 to 1.0%,
V: 0.05 to 0.15%, Mo: 0.05 to 0.5%, W: 0.
05-0.15%, Nb: 0.05-0.15% of at least one or more, and the balance Fe and inevitable impurities, Al content of 0.005% or less as inevitable impurities,
An oil tempered wire obtained by quenching and tempering steel having a Ti content of 0.005% or less at a quenching heating temperature of 950 ° C or higher and 1100 ° C or lower. 4. The composition of steel in% by weight below 1), 2), 3)
A method for producing an oil tempered wire, characterized in that the quenching and heating temperature during quenching and tempering of any of the steels is 950 to 1100 ° C. 1) C: 0.5 to 0.8%, Si: 1.2 to 2.5%, Mn:
Al, which is an inevitable impurity, contains 0.4 to 0.8% and Cr: 0.7 to 1.0%, and consists of the balance Fe and inevitable impurities.
The content is 0.005% or less, the same Ti: the content is 0.005% or less. 2) C: 0.5 to 0.8%, Si: 1.2 to 2.5%, Mn:
It contains 0.4 to 0.8%, Cr: 0.7 to 1.0%, V: 0.05 to 0.15%, and the balance is Fe and inevitable impurities. The Al content as inevitable impurities is 0.005% or less, and the Ti content is 0.005%. %Less than. 3) C: 0.5 to 0.8%, Si: 1.2 to 2.5%, Mn:
0.4-0.8%, Cr: 0.7-1.0%, V: 0.05-0.15%,
And Mo: 0.05-0.5%, W: 0.05-0.15%, N
b: 0.05 to 0.15% of at least one kind is added, and the balance is Fe and unavoidable impurities, the Al content of the unavoidable impurities is 0.005% or less, and the Ti content is 0.0.
0 5 or less.