JPH11172332A - High carbon steel wire - Google Patents

Abstract

(57) [Summary] [Problem] It does not peel during handling or coil transport during coil bundling after hot rolling, but easily peels off during descaling by mechanical processing before drawing. Provided is a high carbon steel wire rod having an oxide scale excellent in peelability. The composition contains 0.5 to 1.1% C by weight.
FeO ratio of 80% by volume or less on the surface and thickness of 10 to 10%
High carbon steel wire with 15 μm oxide scale.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-carbon steel wire, and more particularly, to a hot-rolled steel wire which does not peel off due to small deformation strain caused by vibration during coil binding and coil conveyance. The present invention relates to a high carbon steel wire having an oxide scale excellent in adhesion and peelability, which easily peels off at the time of descaling by mechanical treatment before drawing the steel wire.

[0002]

2. Description of the Related Art Generally, high carbon steel wires such as hard steel wires, piano wires, bead wires and steel tire cords, which require high strength, are made of high carbon containing 0.5 to 1.1% by weight of C. After the steel wire is hot rolled, it is manufactured by subjecting it to secondary processing such as wire drawing and surface treatment.

[0003] However, an oxide scale (hereinafter, simply referred to as scale) generated during rolling adheres to the surface of a steel wire (hereinafter, simply referred to as wire) as manufactured by hot rolling. For this reason, the process of removing scale is performed before the above-mentioned secondary processing. However, if scale is not sufficiently removed and scale remains on the surface of the wire, the scale is removed from the surface of the wire in the next wire drawing step. Flaws are generated and the wire is broken, and the life of the wire drawing die is greatly reduced.

Conventionally, pickling has been used for scale removal. However, in recent years, descaling by pickling has often been regarded as a problem in terms of waste acid treatment and work environment, and scale removal by mechanical treatment (hereinafter, also referred to as “mechanical descaling”) has been frequently used. is there. For this reason, the scale of the hot-rolled wire is required to be easily peeled off by a scale removing step performed before drawing, in particular, mechanical descaling.

[0005] On the other hand, a scale having good releasability easily peels off when a small deformation strain is generated due to handling when binding the wire after hot rolling in a coil or vibration when transporting the same. Sometimes. In this case, although the scale remaining after the above-described scale removing step can be extremely reduced, rust is easily generated in a portion where the scale has peeled off when the wire coil is stored or transported for a long period of time. When rust occurs, as in the case where the scale remains, the rust causes wire breakage at the time of wire drawing, and the appearance of the product after the wire drawing is deteriorated and the value of the product is reduced.

For this reason, there is very little peeling due to minute deformation distortion due to handling during coil binding or vibration during coil conveyance, and a scale that easily peels off during mechanical descaling performed before wire drawing. There is a demand for a wire, that is, a wire having a scale excellent in adhesion and peelability.

Japanese Patent Application Laid-Open No. 9-76008 discloses that 0.3
A wire rod containing 5% by weight or less of C, and (a) a wire rod having a thickness of 7 μm or less and a scale having an FeO ratio of 30% by volume or less occupying an area ratio of 50% or more of the entire surface of the wire rod; Alternatively, a wire having 15% by volume or less of pores having a diameter of 100 μm or less in the scale, and (b) 10 or more wedge-shaped scales having a ratio of depth to surface width of 2 or more in the cross section of the wire. Further, a wire having the scale property of the above (A) is disclosed. The technique proposed in this publication relates to a wire rod having an adhesive scale that is difficult to peel and having a C content of 0.35% by weight or less, and performs secondary processing such as drawing without removing the scale in advance. Is what you can do. However, in the case of a high-carbon steel wire as the object of the present invention, if the wire is drawn with the scale attached, the above-described disconnection and a significant reduction in the die life occur. Therefore, since the descaling process must be performed, the technique described in the above publication cannot be applied as it is.

Japanese Patent Application Laid-Open No. 213448/1990 discloses that a steel having a specific chemical composition is formed and has a surface roughness Ra.
Which is 1.5 μm or less, “a high-carbon steel wire rod having both the adhesion of a secondary scale after hot rolling and the mechanical descaling property before wire drawing” is disclosed. But,
Even if the technique described in this publication is used, there is a case where disconnection occurs at the time of wire drawing due to inferior scale releasability, and the die life is shortened. Further, the scale may be peeled off by the minute deformation strain, and the scale adhesion may not be secured.

[0009] This is because the adhesion of the scale, since the scale thickness and the scale composition is greatly influenced, even if the surface roughness Ra of the wire was 1.5μm or less, a strong binding force between Fe Fe ₃ O ₄ This is because, when a scale mainly composed of is generated, the mechanical descaling property before drawing is deteriorated, and the disconnection and the life of the die are deteriorated. In addition, since the scale formed when held at a high temperature or in the scale generation region for a long time has a large thickness, the surface roughness Ra of the wire is set to 1.5 μm.
This is because, even if it is less than m, it is easily peeled off due to minute deformation strain, and it is not possible to secure the scale adhesion.

[0010]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above situation, and does not peel off due to small deformation strain due to handling of a hot-rolled wire at the time of coil binding or vibration at the time of coil transport. , Descaling by mechanical processing before drawing wire (mechanical descaling)
It is an object of the present invention to provide a high carbon steel wire rod having an oxide scale which is sometimes easily peeled and has excellent adhesion and peelability.

[0011]

The gist of the present invention resides in the following high carbon steel wires.

In other words, "the content of C is 0.5 to 1.1% by weight and the ratio of FeO on the surface is 80% by volume or less,
High carbon steel wire rod having an oxide scale with a thickness of 10 to 15 μm ”.

Here, the steel wire (wire) is a steel that is hot-rolled into a rod and is a steel material that is wound in a coil shape, and includes a so-called “bar-in coil”.

[0014]

DETAILED DESCRIPTION OF THE INVENTION
The exfoliation and scale properties of the scale formed on the surface of the high carbon steel wire containing 1.1% of C were examined in detail. As a result, the following items were found.

As shown in FIG. 1, for example, as shown in FIG.
m. In addition, FIG.
% C-0.17% Si-0.65% Mn-0.006%
Hot wire rolling of a steel slab of SAE1080 having a composition of P-0.006% S by changing heating conditions, rolling conditions, and cooling conditions,
After that, a three-point bending test was performed on a wire rod (FeO ratio is approximately 55 to 77% by volume) having a scale thickness changed by variously changing the heat treatment conditions at a span of 300 mm, and a small deformation strain of 1% and a mechanical descaling equivalent. 6 shows the relationship between the scale thickness and scale peelability when a deformation strain of 6% is applied. The scale releasability was determined from the area ratio at which the scale was peeled off, and this was expressed as “scale peeling rate”.

If the scale thicknesses are equal, the scale peeling behavior due to the small deformation strain becomes the same. For this reason, as shown in FIG. 2, for example, even if an element that affects scale generation, such as Si or Cr, is added, there is no effect on the scale peeling behavior due to the small deformation strain. FIG. 2 shows the above-mentioned SAE 1080 steel slab and its composition as a basic composition.
The content of each of r, Si, and S alone is 0.08%,
A wire rod obtained by hot rolling a steel slab with 0.25% or 0.20% slab under different heating conditions, rolling conditions and cooling conditions, and then changing the thickness of the scale by variously changing the heat treatment conditions. (FeO ratio is about 55-77% by volume and span 300
3 shows a relationship between scale thickness and scale peelability when a 3-point bending test is performed at 1 mm and a small deformation strain of 1% is applied.

In order to suppress scale peeling due to minute deformation strain, for example, as shown in FIG. 3, the scale composition may be adjusted so that the ratio of FeO is 80% by volume or less. FIG. 3 shows hot wire rolling of the above slab of SAE1080 under different heating conditions, rolling conditions, and cooling conditions.
After that, the wire rod with the composition and thickness of the scale changed by variously changing the heat treatment conditions was subjected to a three-point bending test with a span of 300 mm, and the relationship between the scale thickness and the scale releasability when 1% small deformation strain was applied was determined. It is shown.

When the thickness of the scale is 8 μm or more, as shown in FIG. 1 described above, the scale releasability at a deformation strain of, for example, 6% corresponding to mechanical descaling is good.

The chemical composition of the wire to which the present invention is applied is not particularly limited except for C, and the properties (eg, strength and corrosion resistance) required for a product manufactured using the wire as a material are not required. What is necessary is just a component composition which can be ensured.

More specifically, for example, as an element other than C, by weight%, Si: 0.01-1.5%, Mn: 0.01
To 2.0%, Cr: 0 to 2.0%, Mo: 0 to 0.6
%, Cu: 0 to 2.0%, Ni: 0 to 4.0%, Ti:
0 to 0.10%, Al: 0.001 to 0.10%, N:
0-0.03%, V: 0-0.40%, Nb: 0-0-0.
15%, B: 0 to 0.005%, S: 0 to 0.10%,
Pb: 0 to 0.35%, Ca: 0 to 0.01%, the balance being Fe and inevitable impurities, and P as an impurity may be 0.05% or less.

The present invention has been completed based on the above findings.

Hereinafter, each requirement of the present invention will be described in detail.

(A) Chemical composition of wire C: 0.5 to 1.1% by weight C is contained at least 0.5% by weight in order to secure strength required for a product manufactured using the wire as a raw material. Need to be done. However, if it is contained in excess of 1.1% by weight, ductility is deteriorated and disconnection frequently occurs during wire drawing. Therefore, the content of C is set to 0.5 to 1.1% by weight.

(B) Scale Composition and Thickness As shown in FIG. 3, the scale exfoliation rate when a small deformation strain is applied is small when the proportion of FeO in the scale is 80% by volume or less. Therefore, in order to prevent the scale from peeling due to minute deformation strain due to vibration during handling or coil conveyance during coil binding, that is, to increase the adhesion of the scale, the ratio of FeO in the scale is set to 80%. % By volume or less. If the ratio of FeO is too small, the mechanical descaling property is reduced. Therefore, the lower limit is preferably set to 50% by volume.

As shown in FIG. 1 and FIG. 2, the scale peeling rate when a small deformation strain is applied is 5%.
When the thickness exceeds μm, the thickness increases as the thickness increases, and reaches a maximum at about 8 μm. As the scale thickness further increases, the scale exfoliation rate decreases, and reaches a minimum at a thickness of 10 to 15 μm. 15μ scale thickness
Above m, the scale exfoliation rate increases again with increasing scale thickness. Therefore, in order to prevent the scale from peeling due to minute deformation distortion due to handling during coil binding and vibration during coil conveyance, in other words, to increase the adhesion of the scale, the thickness of the scale must be increased. Must be 5 μm or less or 10 to 15 μm. On the other hand, as shown in FIG. 1, the scale peeling rate when a deformation strain of 6% corresponding to mechanical descaling is applied increases with the scale thickness,
Above μm, the peel rate is almost 100% regardless of the scale thickness. Therefore, in order to easily peel off the scale at the time of mechanical descaling before drawing the wire, the thickness of the scale needs to be 8 μm or more. From the above, in the present invention, the thickness of the scale is set to 10 to 15 μm in order to obtain a scale excellent in adhesion and peelability.

The high-carbon steel wire of the present invention is prepared, for example, by melting a steel having the above-mentioned chemical composition by an ordinary method, forming a slab by an ordinary method, and heating the slab to 900 to 1250 ° C. It is easily obtained by hot rolling into a wire at a finishing temperature of 1150 to 750 ° C by a usual method, cooling from 1000 to 700 ° C to 500 ° C at a cooling rate of 3 to 12 ° C / sec, and then winding up. .

Now, the present invention will be described in further detail with reference to Examples.

[0028]

EXAMPLES Steel having the chemical composition shown in Table 1 was melted and slab-rolled by ordinary methods into 1-ton billets.

[0029]

[Table 1]

Next, the above billet was 5.5 m in diameter.
m was hot rolled. In addition, the heating temperature of hot rolling is 900 to 1250 ° C, and the finishing temperature is 1000 to 750 ° C.
From 1100 to 700 ° C to 500 ° C for 3 to 20
The composition and thickness of the scale were changed by cooling at a cooling rate of ° C./sec and then winding.

With respect to each of the wires obtained as described above, the scale thickness, the ratio (volume%) of FeO in the scale, and the scale releasability were examined.

The scale thickness was measured by cutting the wire at a right angle to the rolling direction, polishing the mirror surface, and then observing the wire with an optical microscope at a magnification of 500 times.

The FeO ratio in the scale is determined by applying a stress to the wire to completely separate the scale, and performing X-ray diffraction on the separated scale to obtain a peak intensity ratio of FeO, Fe ₂ O ₃ , and Fe ₃ O _4. Asked from.

The scale releasability was measured by cutting a wire into a length of 500 mm, performing a three-point bending test at a span of 300 mm, and measuring the area ratio at which the scale was peeled when the deformation strain became 1% and 6% (scale peeling ratio). ).

Table 2 shows the results of various investigations.

[0036]

[Table 2]

From Table 2, in the case of a high carbon steel wire having a scale whose FeO ratio and thickness are in the ranges specified in the present invention, when the deformation strain is small, the scale is in close contact, which corresponds to mechanical descaling. It is clear that the scale peels off almost completely when a large deformation strain is applied.

[0038]

The high carbon steel wire of the present invention does not rust on the wire since the scale does not peel off during handling or coil transport after bundling the coil after hot rolling, so that the wire does not rust, and the mechanical material before drawing is used. At the time of descaling, the scale easily peels off. For this reason, breakage at the time of wire drawing due to rust or residual scale can be prevented, and the life of the wire drawing die can be greatly increased. Further, the appearance of the product after wire drawing does not deteriorate and the value of the product does not decrease.

[Brief description of the drawings]

FIG. 1 shows a heating condition, a rolling condition, and a slab of SAE1080.
A three-point bending test was performed on a wire manufactured under different cooling and heat treatment conditions, and the relationship between the scale thickness and the scale peeling ratio when a 1% minute deformation strain and a 6% deformation strain equivalent to mechanical descaling were applied was determined. FIG.

[FIG. 2] A steel slab of SAE1080 and a steel slab whose composition is the basic composition and in which the contents of Cr, Si, and S are individually changed are manufactured by changing heating conditions, rolling conditions, cooling conditions, and heat treatment conditions. FIG. 3 is a diagram showing the relationship between scale thickness and scale peelability when a three-point bending test is performed on a prepared wire (the FeO ratio is 55 to 77% by volume) and a small deformation strain of 1% is applied.

FIG. 3 shows heating conditions, rolling conditions,
It is a figure which shows the relationship between scale thickness and scale peeling when the wire rod manufactured by changing cooling conditions and heat treatment conditions is subjected to a three-point bending test and applying a small deformation strain of 1%.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Kakizaki 1 Konomi-cho, Kokura-Kita-ku, Kitakyushu-shi, Fukuoka Sumitomo Metal Industries, Ltd. Kokura Works

Claims (1)

[Claims] (1) containing 0.5 to 1.1% by weight of C;
FeO ratio of 80% by volume or less on the surface and thickness of 10 to 10%
High carbon steel wire with 15 μm oxide scale.