JPS6324046A - Wire rod for high toughness and high ductility ultrafine wire - Google Patents

Abstract

PURPOSE:To obtain a wire rod capable of giving a high toughness and high ductility ultrafine wire having high strength in a high yield by specifying a composition consisting of C, Si, Mn, P, S, Al and Fe so as to make the C and Si contents high and the amounts of P, S and Al very small. CONSTITUTION:This wire rod for a high toughness and high ductility ultrafine wire consists of, by weight, 0.75-1.00% C, 1.00-1.60% Si, 0.20-0.60% Mn, <=0.020% P, <=0.020% S, <=0.003% Al and the balance Fe with inevitable impurities or further contains 0.10-0.50% in total of Cr and/or V. When the wire rod is used, a high toughness and high ductility ultrafine wire of <=0.5mm diameter having >=300kgf/mm<2> tensile strength can be manufactured without breaking.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a wire rod for producing a high-strength, high-toughness, high-ductility ultrafine wire, and in particular, a wire rod with a tensile strength of 300 kgf.
The present invention relates to a wire rod for producing ultrafine wires such as steel cords, belt cords, hose wires, etc., which have a wire diameter Q of 5 mm or more and have high toughness and high ductility.

Conventional technology Ultra-fine wires are usually produced by hot rolling steel having a predetermined chemical composition, and then adjusting and cooling the steel as required.
It is manufactured from a wire rod with a diameter of mm through primary drawing processing, patenting processing, secondary wire drawing processing, patenting processing again, plus plating, and final wet double wire processing.

For example, steel coat is manufactured by twisting the ultrafine wires obtained as described above.

In such a manufacturing process, the thin wire after plus plating is subjected to a strong processing of 93 to 98% in the final wet wire drawing, and then several or dozens of these wet wire drawn ultra-fine wires are twisted. Together they are formed into a steel cord. The ultra-fine wire is subjected to stronger torsional, tensile and bending stresses during this wire stranding process than during the wet wire drawing process.

In addition, the tensile strength of normal ultra-fine wire is 250 to 300 kg.
Since f/+nm2 is very high, even if there is a slight defect in the ultrafine wire, these steel wires will break during the wet wire drawing process or the subsequent wire stranding process.

In particular, 300 to 330 kgf/m manufactured in recent years
In the case of high-strength steel cords with a diameter of 1.5 mm, the wire breakage increases because the toughness and ductility of the ultra-fine wire used is lower. Such wire breakages lead to reduced productivity and yield during the wet wire drawing and stranding processes. Not only this, but also the number of joints in the steel cord as a final product increases, deteriorating the quality of the steel cord.

As a result of intensive research to solve the above-mentioned problems in manufacturing high-strength, high-toughness, high-ductility steel cords, belt cords, hose wires, etc., the present inventors have found that: Cff10. which has been commonly used as a raw material wire rod.
High C high Si instead of 65~0.85% high carbon steel wire rod
The present invention was achieved by discovering that by using i'tA material, it is possible to produce ultrafine wires having high strength, high toughness, and high ductility.

Therefore, the present invention can reduce wire breakage in the wet wire drawing process and the wire stranding process, and can produce ultra-fine wires such as steel cords with high yield, especially ultra-fine wires of about 300 kgf/mm2 or more. The object of the present invention is to provide a wire rod for ultra-fine wires, in which the resulting ultra-fine wires have higher toughness and ductility than before.

1.Means for solving the FI problem The high toughness and high ductility wire rod for ultrafine wire according to the present invention has, in weight percent, C 0.75 to 1,00%, Si 1.00 to 1.60%, and Mn 0.20. ~0.60%, P 0.020% or less, S 0.020% or less, A7! 0.0030% or less, balance consisting of iron and unavoidable impurities, tensile strength 300
This is a wire rod for producing high toughness and high ductility ultrafine wire with a wire diameter of kgf/mm2 or more and a wire diameter of 0.5 y or less.

First, the chemical components of the high toughness and high ductility wire rod for ultrafine wire according to the present invention will be explained.

In order to obtain a high-strength ultra-fine wire with a tensile strength of 300 kgf/mm2 or more, it is advantageous to increase the above-mentioned patenting strength as high as possible, and also to increase the twist value of the final ultra-fine wire. Also, it is advantageous to increase the tensile strength of the patented material and reduce the total processing rate in wet wire drawing.

Generally, the higher the Cfi in the wire, the easier it is to obtain a high-strength polar f-1II wire.
Since it is an element that easily segregates, when increasing Cl, wire breakage is likely to occur in the wet wire drawing process or the wire stranding process due to this central segregation. In particular, when Cl exceeds 1.00%, mesh-like cementite is generated at the prior austenite grain boundaries in the final patenting process. If cementite is generated in this way, it not only deteriorates the subsequent wire drawability but also significantly deteriorates the toughness and properties of the ultra-fine wire, resulting in frequent wire breakage during wet wire drawing or stranding.

For this reason, in the present invention, the amount of C added is 0.
The range is 75 to 1,00%, preferably 0.75 to 1,00%.
The range is 0.90%.

Si is effective in increasing the tensile strength of patented materials, as shown in Figure 1 for 5ii(7) different 0,82C0,5OMn steels, and in order to obtain high strength in ultra-fine wires, Si is effective in increasing the tensile strength of patented materials. It is also very effective. Therefore, as in the case of C, in order to obtain an ultra-fine wire with a constant tensile strength, the processing rate in the final wet wire drawing process can be reduced, and as a result, the final ultra-fine wire has a high twist value. can be obtained. In addition, in the case of C, even if its content is increased, under a certain tensile strength of ultrafine wire, the drawing area, which is a guideline for ductility, does not depend on the C content and remains constant, but when Si is increased As shown in FIG. 2, the steel shown in FIG. Therefore, the addition of Si is also effective in obtaining high strength, high ductility, and extremely high mvA.

Furthermore, the addition of Si has the effect of delaying aging due to C. In the wet wire drawing process, the steel wire is aged by C and N, which deteriorates the toughness and ductility of the steel wire.

Since Si delays these aging processes, it is possible to manufacture a high-strength steel wire without reducing the toughness and ductility of the steel wire. This seems to be the reason why Si-added steel exhibits a high reduction of area even under the above-mentioned constant strength. Moreover, the effect of delaying this aging suppresses the occurrence of vertical cracks in the twisting test.

As described above, the effect of adding Si is very large, but when it is less than 1.00%, the above effects, especially the aging suppressing effect, are poor. On the other hand, although Si solid-solution strengthens ferrite and increases lead patenting strength, it has the disadvantage of reducing wire drawability. This is particularly noticeable in steels containing more than 2.00% Si. Therefore, in the present invention, the amount of Si added is 1.00 to 2.
00%, preferably 1.00 to 1.60%.

As described above, in steel to which Si is added in a range of 1.00 to 2.00%, deoxidation with Mn is unnecessary because sufficient deoxidation is performed during the steel manufacturing process. Furthermore, since Si is an element that increases hardenability, there is no need to increase hardenability with Mn. Rather, when Mn is added to further enhance the hardenability, martensite is generated in the wire in the controlled cooling process after hot rolling, which causes wire breakage during the subsequent wire drawing. Furthermore, since Mn is an element that easily segregates, martensite is likely to occur in the segregated portion. Martensite generated in the segregation area generates chevron cracks that cause cubby wire breakage. .

For these reasons, in Si-added steel, the Mn content should be reduced as much as possible, and in the present invention, the upper limit is set to 0.60%.

In addition, in order to prevent the generation of martensite, the amount of Mn added should be reduced as much as possible, but on the other hand, Mn has the effect of fixing S in steel as M n S. . S dissolved in steel reduces the toughness and ductility of the steel wire, so in order to fix it, Mn must be at least 0.
．． It is necessary to add 20%. Therefore, in the present invention, the amount of Mn added is in the range of 0.20 to 0.60%.

As mentioned above, S is an element that reduces the toughness and ductility of steel, and is also an element that tends to segregate.

Therefore, in the present invention, the amount of S in the wire is 0, 0
The content should be 20% or less, preferably 0.010% or less.

Like S, P is an element that reduces the toughness and ductility of steel and is likely to segregate, so the content is set to 0.010% or less.

Non-ductile inclusions mainly composed of AHA such as AHA and Mg0-AlzOi are other major causes of wire breaks that occur during steel cord manufacturing. Moreover, these non-ductile inclusions not only have a detrimental effect on the life of the die in the final wet wire drawing process, but also deteriorate the fatigue properties of the steel cord and the raw material wire therefor. Therefore,
In the present invention, the Aff amount is preferably as small as possible, and is 0.003% or less.

In addition to the above-mentioned elements, the high toughness and high ductility wire rod for ultrafine wire according to the present invention may further contain one or both of Cr and V in a total amount of 0.10 to 0.50%. can.

As shown in Fig. 3, the addition of Cr increases the work hardening rate during wire drawing, so it is effective in obtaining high-strength steel wire at a low processing rate, and C-? ) Like Si, it contributes to improving the toughness and ductility of the final ultra-fine wire, particularly to improving the torsion value. Furthermore, since Cr increases the corrosion resistance of steel, it also effectively acts against corrosion fatigue that steel cords undergo in rubber products such as tires.

On the other hand, (2) does not have the effect of increasing the work hardening rate like Cr, but as shown in FIG. 4, it is more effective than Cr in increasing corrosion resistance.

In order to obtain the above effects by adding Cr and/or
It is necessary to add more than %. On the other hand, Cr and V are elements that significantly improve the hardenability, so when they are added in excess, the hardenability becomes too high and martensitic Mi weave occurs in the hot rolled wire rod. This will interfere with wire drawing. Further, when the hardenability is increased too much in this manner, a perfect pearlite structure cannot be obtained in the patenting treatment during wire processing, and martensite Miffl and bainite structures are generated, making wire processing difficult. For these reasons, in the present invention, C
The upper limit of the total amount of r and/or () added is 0.50%.

Effects of the Invention As described above, the high toughness and high ductility wire rod for ultrafine wire according to the present invention has a high tensile strength of the lead patenting material by setting the Si content to 1.00% or more. By reducing the processing rate and reducing the content of P and S, the toughness and ductility of the final ultra-fine wire can be made higher than that of conventional ultra-fine wires, thus improving the manufacturing process of ultra-fine wires and steel cords. High-strength ultra-fine wires and steel cords can be manufactured without increasing the number of wire breaks. Furthermore, in the present invention, A! As a result of regulating the total amount to a very small amount, the amount of non-spreading inclusions such as Al2O:1 is very small, and therefore there are almost no wire breaks due to these inclusions.

Furthermore, by adding Cr or V, the toughness and ductility of the ultra-fine wire can be further improved, or the corrosion resistance can be improved. Therefore, by using a wire containing these elements, it is possible to produce ultrafine wires, steel cords, etc. that have high strength, high toughness, high ductility, and excellent corrosion resistance.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Examples Table 1 shows the mechanical properties of 0.25 m diameter ultrafine wires produced by wet wire drawing from 5.5 nm diameter ultrafine wire rods having the chemical components shown in Table 1.

The Si-doped ultrafine wire manufactured from the wire according to the present invention has a high strength of about 320 kgf/mm2 or more, and a
It has a high aperture of 0% or more. Furthermore, regarding the twist value, the ultra-fine wire manufactured from conventional wire rods has a twist value of 32 to 35 twists, whereas the high-Si ultra-fine wire according to the present invention has a twist value of 40 twists.
It has a torsion value of more than 2 times.

Furthermore, although the ultra-fine wire steel manufactured from the Cr- and ■-added wire rod according to the present invention has a very high tensile strength of about 350 kgf/mm, it is higher than the conventional tensile strength of 320 to 335 kgf/mm.
This value is higher than the twist value of an ultra-fine wire of kgf/mm2.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the amount of Si and tensile strength in patented materials, and FIG. 2 is a graph showing the relationship between tensile strength and reduction of area in high Si @ and low Si steels.
Figure 3 is a graph showing the relationship between working rate and tensile strength for Cr-added steel and non-additive steel, and Figure 4 is a graph showing the relationship between corrosion period and corrosion j&ffl for Cr-added steel and non-additive steel. be. Patent Applicant: Kobe Steel, Ltd. Representative Patent Attorney: Ittsu Makino Figure 1 Figure 2 3θ0 320 340, fMθ
33θ31 case reduction φ pregnancy, L2) Fig. 3 Fig. 4 Corroded plaque ζ stone) Hand, spontaneous writing of continuation correction) June 24, 1986

Claims (2)

[Claims] (1) C 0.75 to 1.00%, Si 1.00 to 1.60%, Mn 0.20 to 0.60%, P 0.020% or less, S 0.020% or less, in weight%. Consisting of Al 0.003% or less, balance iron and unavoidable impurities, tensile strength 300k
A wire rod for high-toughness, high-ductility ultra-fine wire for producing a high-toughness, high-ductility ultra-fine wire with gf/mm^2 or more and a wire diameter of 0.5 mm or less. (2) In weight% (a) C 0.75-1.00%, Si 1.00-1.60%, Mn 0.20-0.60%, P 0.020% or less, S 0.020 % or less, Al 0.003% or less, (b) one or both of Cr and V in a total amount of 0.10 to
0.50%, balance iron and unavoidable impurities, tensile strength 300k
A wire rod for high-toughness, high-ductility ultra-fine wire for producing a high-toughness, high-ductility ultra-fine wire with gf/mm^2 or more and a wire diameter of 0.5 mm or less.