JPS634016A - Production of extra high tension steel wire having excellent ductility - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing ultra-high tensile strength '::@i with excellent ductility.

(Prior art) Piano wire and similar steel wires are used in a wide range of fields such as PWS wires, springs, hose wires, and tire cords, but in recent years there has been a demand for the development of steel wires with strength levels higher than JIS standards. is increasing.

Hereinafter, in the present invention, the term "ultra" high tensile strength steel wire is used because when referring to high tensile strength steel wire, it usually refers to a steel wire having a strength equivalent to JIS G 3522 piano wire.
It was called ultra-high tensile steel wire, meaning that it has a higher strength than that.

JIS G 3522 stipulates the tensile strength of steel wires with diameters from 6mm to o, sw, but the tensile strength depends on the wire diameter, and higher strength can be easily achieved as the wire diameter becomes smaller. Therefore, JIS also has a system similar to this, and the upper limit of tensile strength can be roughly expressed by the following formula.

TS=250-1001ogD (Kgf/Set 2)
(1) However, D is the diameter (bite) of the steel wire.

Equation (1) was determined for a steel wire with a diameter of 6 to 0.0811111, and is valid in the range of approximately 10 to o-osw. The cross-sectional shape of the steel wire is often circular (although it is often used, it may also be square, trapezoidal, trapezoidal, etc. In this case,
As D, the diameter of a circle having the same cross section is used.

Piano wire and similar steel wire use wire rod equivalent to piano wire, and after applying patenting treatment to it,
It is generally manufactured by drawing wire at room temperature.

In addition, cold rolling may be performed instead of wire drawing, and regarding cold rolling of steel wire, see Wire J, 16.
(1983), 7.64, it is difficult to achieve ultra-high tensile strength levels in conventional carbon steels, such as those illustrated.

For cold rolling and roller die drawing, the processing limit is thicker than normal wire drawing for the reason explained later, but the work hardening rate is smaller than normal wire drawing, so the composition of normal piano wire rods cannot be used for ultra-high tensile strength. This is because in order to achieve this level, it is necessary to significantly increase the working degree, which results in a decrease in ductility.

Furthermore, Japanese Patent Publication No. 59-33175 and the like disclose an example of martensitizing medium carbon steel and drawing it with a roller die, but this relates to a tempered martensitic high-tensile wire rod.

Furthermore, if an attempt is made to manufacture an ultra-high tensile strength steel wire with a strength level of (1) 2 or higher using the conventional wire drawing method, the following problems arise.

In other words, in order to increase the strength, there are two methods: increasing the strength during patenting treatment and increasing the wire drawing area reduction ratio, but in either method, as long as the wire is manufactured using a normal wire drawing method, Even if it is possible to increase the strength, the ductility, which is an important characteristic for ultra-high tensile steel wires, and especially the torsional properties, will be significantly reduced, and problems such as cracking and wire breakage will occur during processes such as stranding and coiling. Yasu (naru)

Furthermore, piano wire is often used after being plated or blued, but these treatments cause aging and reduce ductility, making it difficult to achieve an ultra-high tensile strength level.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method for manufacturing a steel wire rod having a steel composition in order to achieve ultra-high tensile strength without causing such a decrease in ductility.

(Means for Solving the Problems) The present invention involves drawing a high carbon steel wire rod mainly composed of C, Si, Mn, Cr, By drawing with a hole die with a cross-section reduction rate of 40% or less after processing, 25
This is a method for producing an ultra-high tensile steel wire with excellent ductility, which achieves a tensile strength of 0-1001 ogD (K9f/a2) (where D is the diameter of the steel wire) or more.

When drawing a steel wire, as the degree of work increases, the strength increases due to work hardening, but when the degree of work exceeds a certain degree, the ductility, represented by the reduction of area or twist value, sharply decreases. The strength at that time is the limit of practically usable strength, and the degree of processing at that time is the practical limit of processing.

The processing limit is essentially caused by a decrease in the ductility of the material due to work hardening, but it also changes depending on the processing conditions. In wire drawing using a normal hole die, it is a known problem that tensile residual stress is generated near the surface of the steel wire, strain age hardening occurs due to heat generated during wire drawing, and deformation texture is generated. However, all of these factors specific to wire drawing lead to a decrease in ductility.

At normal strength levels, these factors resulting from wire drawing do not have a noticeable effect because the material still has sufficient ductility; however, as the strength level increases, wire drawing Processing factors become important and this leads to a reduction in processing limits. Therefore, it is difficult to produce an ultra-high tensile strength steel wire with a strength level equal to or higher than that expressed by formula (1) using the wire drawing method.

The present inventors have studied various methods for manufacturing ultra-high tensile strength steel wires, and have obtained the following knowledge. In normal wire drawing processing (hereinafter simply referred to as wire drawing processing), the steel wire is passed through a hole die and drawn, so the frictional force between the die and the steel wire,
Since the processing is performed in a complex stress field due to a combination of compressive force from the die and pulling force, the strain within the cross section of the steel wire rod at an angle in the longitudinal direction is non-uniform.

In particular, since the pullout force is assigned larger than the compression force, minute cracks tend to occur around non-metallic inclusions in the material (which causes a decrease in ductility).

In addition, since the frictional work is large, heat generation at the surface is large (and aging embrittlement due to temperature rise near the surface layer is large. Embrittlement of the surface layer is particularly harmful to torsional properties.

All of the above-mentioned problems are caused by the drawing of hole dies, so we investigated alternative methods and found that cold rolling and roller die drawing were effective.

In cold rolling and roller die drawing, the abrasive work between the roll and the copper wire is smaller than that with a hole die, and the drawing force is almost zero in the rolling method, and even with a roller die, compared to a hole die. Therefore, the main deformation stress is the compressive stress from the rolls, so the deformation is uniform, it is less likely to cause thin cracks around non-metallic inclusions, and it is also less prone to embrittlement due to aging ( For the sake of
This can prevent a decrease in ductility.

Such excellent ductility of the rolled and roller die processed material does not suddenly disappear even if it is subsequently subjected to hole die wire drawing, and if the amount of wire drawing is within about 40% of the area reduction rate, The effect was recognized.

Ordinary rolling and roller die processing vs? The cross-sectional shape accuracy and dimensional accuracy of IN are inferior to hole die wire drawing, which may be inconvenient depending on the application.In such cases, wire drawing after rolling or roller die processing It can be made into an ultra-high tensile steel wire with high ductility (and excellent dimensions and shape).

Furthermore, since a high work hardening rate can be obtained in wire drawing, the combination of rolling and drawing has the advantage that strength can be easily increased compared to the case of rolling (or roller die) alone. Therefore, there is positive significance in wire drawing after rolling (or roller die).

The present inventors investigated the influence of steel composition in order to achieve higher strength and improved ductility, and as a result, it was found that the following composition system is suitable.

C is an economical and effective reinforcing element, but in order to achieve strength equal to or higher than formula (1) without special alloying addition, 0.85
% or more, and when adding alloying elements as described below, 0.6% or more is required.

Moreover, if it is 1.0% or more, pro-eutectoid cementite is generated during patenting, making it unsuitable for cold working. However, in order to obtain superior ductility with a strength equal to or higher than formula (1), it is desirable to contain alloying elements as described below.

0.1% or more of Si is required for deoxidation. Si is effective in strengthening as a solid bath hardening agent, but if it is less than 0.35%, the effect is small, and if it is more than 2%, the ductility deteriorates, so it is not suitable.

The reduction of the steel wire is closely related to the pearlite lamella spacing, and reaches its maximum at about 28 OA, but Si strengthens the ferrite layer without changing the pearlite lamella spacing of the material, so the decrease in ductility is minimal. It is effective in increasing the strength of steel wire with little effort.

Therefore, if the purpose is deoxidation, the minimum value of Si should be set to 0.
．． 1%, and if the purpose is solid solution hardening, the minimum value is 0.
．． It shall be 35%.

1'VLn is required in an amount of 0.1% or more to deoxidize and remove the harmful effects of S. As an element for improving hardenability, 1'VLn is particularly effective in increasing the patenting strength of thick wire rods. The effect is remarkable when adding 0.9% or more, but
If the ratio exceeds 2, the ductility deteriorates, so it is not suitable.

Therefore, for that purpose, the minimum values for earth are 0.1% and 0.
You can choose between 9%.

Cr is an effective element for refining the spacing between pearlite lamellae, and is effective in strengthening wire rods from thin to thick sizes, but if it exceeds 1%, it is difficult to fully demonstrate its effect.

(2) is an element that improves hardenability and is particularly effective in increasing the patenting strength of thick wire rods. It also refines the austenite grain size and is effective in improving ductility.2)
Ru. Below 0.002%, the effect is small and 0.5%
Exceeding this is not appropriate because the ductility will actually deteriorate.

Teeth refine the austenite grain size and are effective in improving ductility, but are ineffective at 0.002% or less, and 0.002% or less.
If it exceeds 5%, it is not suitable because the ductility deteriorates.

Regarding At, if fine-grained steel is desired, 0.0
About 1 to 0.1% is added, and if it is necessary to soften coarse-grained steel or inclusions, it is reduced to 0.01% or less.

Since any of these cases may occur, the content of At is not particularly specified.

By cold rolling or roller die drawing a material with increased strength during patenting due to the above components, it is possible to obtain (1) an ultra-high tensile strength wI4m with a strength of 2 or more without causing a decrease in ductility; It becomes possible to manufacture easily.

(Example) After lead patenting, a steel wire rod was pickled to remove scale, and then subjected to zinc phosphate coating treatment. During wire drawing, a wire drawing lubricant was used to draw the wire, and during cold rolling and roller die drawing, rolling or roller die drawing was performed while lubricating with rolling oil.

After processing, the steel wire was heated to 450°C in the as-processed state and at 450°C.
A bluing treatment was applied for 5 seconds, and the material quality was evaluated by a tensile test and a twist test.

Table 1 shows the results of manufacturing with various steel components.

No. 1 to 14 increase C, St, and Mn, or increase C.
By adding r, V, and Nb, the strength during patenting has been further increased, but with the conventional wire drawing method, the torsion value is particularly low (and it is difficult to obtain sufficient performance). However, in the rolling or roller die method of the present invention, excellent ductility with high reduction of area and high twist values was obtained.

Table 2 shows the results of hole die wire drawing after rolling or roller die processing, and it was found that sufficient ductility remained when wire drawing was performed within 40% of the present invention.

(Effects of the Invention) As described above, the present invention improves ductility by cold working steel wire rods having specific components by rolling or roller dies, or by drawing them within 40% after the working. This made it possible to manufacture ultra-high tensile strength steel wire without deterioration. The present invention has made it possible to significantly reduce wire breakage during wire drawing and stranding, processing cracks during molding, and breakage during use.

Claims (1)

[Claims] 1 A high carbon steel wire rod whose basic components are C: 0.60/1.0%, Si: 0.1/2.0%, Mn: 0.1/2.0%, 250-100lo by cold rolling or roller die drawing, or by cold rolling or roller die drawing and then drawing with a hole die with a reduction in area of 40% or less.
A method for producing an ultra-high tensile steel wire with excellent ductility, characterized in that the tensile strength is greater than gD (Kg/mm) (where D is the diameter of the steel wire, mm). 2 High carbon steel wire rod, C: 0.85/1.0%, Si:
0.1/2.0%, Mn: 0.1/2.0%, and the balance consists of iron and inevitable impurities.
A method for producing an ultra-high tensile strength steel wire with excellent ductility as described in . 3 High carbon steel wire rod, C: 0.60/1.0%, Si:
Contains 0.35/2.0%, Mn: 0.1/2.0%,
The method for producing an ultra-high tensile strength steel wire with excellent ductility according to claim 1, wherein the balance is iron and unavoidable impurities. 4 High carbon steel wire rod, C: 0.60/1.0%, Si:
0.1/2.0%, Mn: 0.1/2.0%, and further contains Cr: 0.1/1.0%, V: 0.002/0.
5%, Nb: 0.002/0.50%, and the balance is iron and unavoidable impurities.