KR101316154B1 - High carbon steel wire for aluminium conductor steel reinforced having superior electroconductivity and method of manufacturing the same - Google Patents

Abstract

Preparing a high-strength steel wire for aluminum core wire having excellent electrical conductivity, comprising the step of preparing a steel wire without an aluminum-zinc plated layer, and forming a coating layer of titanium nitride having a thickness of 10 ~ 15㎛ on the surface of the steel wire A manufacturing method and a steel wire produced by the method are provided.
According to the present invention, it is possible to provide a high carbon steel wire for ACSR having excellent electrical conductivity without using expensive Ni almost.

Description

High carbon steel wire for high-strength aluminum stranded wire with excellent electrical conductivity and manufacturing method thereof {HIGH CARBON STEEL WIRE FOR ALUMINIUM CONDUCTOR STEEL REINFORCED HAVING SUPERIOR ELECTROCONDUCTIVITY AND METHOD OF MANUFACTURING THE SAME}

The present invention relates to a high carbon steel wire for aluminum conductor steel reinforced (ACSR) excellent in electrical conductivity and a method of manufacturing the same.

Usually, the transmission voltage ranges from a relatively low voltage below 200 kV to an Ultra High Voltage (UHV) above 1,000 kV.

In general, a high-carbon steel wire having excellent strength is used as a support, and since electrical conductivity is poor according to temperature, Zn and Al are hot-dipped to alleviate this, thereby improving surface electrical conductivity. However, when current flows through the wire, heat is essentially generated, and the generated heat heats the high carbon steel wire, which is an internal support line. The temperature at this time is in the range of 150-200 ° C. and is expected to increase further when UHV is used. Temperatures from 150 ° C. to 200 ° C. deteriorate the high carbon steel wire, causing linear expansion, which lowers the electrical conductivity.

In order to solve this problem, in general, the transmission line uses 35% to 40% of Ni-containing INVAR wire by wire, and more than 50% of the transmission line steel wire has been replaced by INVAR wire in high carbon steel wire. . As is known, the INVAR alloy is a material having excellent electrical conductivity because there is almost no change in length due to temperature changes, but has a disadvantage of high Ni price.

One aspect of the present invention is to propose a wire that improves electrical conductivity by reducing the volume of linear expansion of the steel wire for ACSR (Aluminum Conductor Steel Reinforced).

Another aspect of the present invention is to propose a preferred method for producing the steel wire.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, one aspect of the present invention, the step of preparing a steel wire in which the aluminum-zinc plating layer is not formed, and to form a coating layer of titanium nitride of 10 ~ 15㎛ thickness on the surface of the steel wire It provides a method for producing a high carbon steel wire for a steel core aluminum stranded wire having excellent electrical conductivity comprising the step.

Another aspect of the invention is, by weight, C: 0.6 to 0.9%, Si: 0.2 to 1.5%, Mn: 0.2 to 1.0%, the balance Fe and other unavoidably contained impurities, 10 to 15 on the surface The present invention provides a high carbon steel wire for a high-strength aluminum core strand having excellent electrical conductivity, including a coating layer of titanium nitride having a thickness of μm.

According to one aspect of the present invention, it is possible to provide a high-carbon steel wire for ACSR excellent in electrical conductivity with little use of expensive Ni.

1 is a schematic diagram of equipment for coating titanium nitride on a steel wire exiting the final die according to an embodiment of the present invention.
FIG. 2 is a graph showing a change in linear expansion in the steel wire surface and near the surface according to temperature change in the inventive examples and comparative examples. FIG.

Hereinafter, a method for manufacturing a high-carbon steel wire for steel core aluminum stranded wire having excellent electrical conductivity of the present invention will be described in detail so that a person skilled in the art can easily carry out the present invention.

The present invention provides a manufacturing method of improving the electrical conductivity by reducing the volume of linear expansion (wire expansion) of the aluminum wire for ACSR (Aluminum Conductor Steel Reinforced), in particular a magnetron sputter on the steel wire exiting the final die The present invention relates to a method for manufacturing steel wire which effectively reduces the decrease in electrical conductivity due to the increase in the amount of linear expansion when the temperature is increased by coating titanium nitride on the surface by using a device.

A typical manufacturing process for steel wire for ACSR is as follows. The rolled billet is heated at 1000-1200 ° C. for about 2 hours or less and then wire rolled at a temperature between 900-1100 ° C. to form a 13 mmf diameter wire rod. It is then cooled to 800-900 ° C. and then wound up in a ring to cool on a Stallmore cooling stand. Subsequently, the cooled wire is lead patterned (LP; Lead Patenting) at 550-600 ° C., dried and freshly pickled, and manufactured to a diameter of 5 mmf or less (the actual product diameter is 4 to 6 mmf). Galvanizing for tens of seconds at 400-500 ° C. forms a Zn and Al hot dip layer of 30-40 mm on the surface. After forming the plating layer on the surface it is finally stranded.

Zn and Al plated layers show higher electrical conductivity than general high carbon steel wires, but have limitations. In other words, heat is necessarily generated when current flows through the wire, and the generated heat degrades the high carbon steel wire, which is an internal support line, thereby causing a change in linear expansion, thereby lowering electrical conductivity. For this reason, the INVAR wire rod in which 35-40% of Ni is added by weight is used freshly. The INVAR alloy is a material with excellent electrical conductivity because it has almost no change in length due to temperature change, but has a disadvantage in that the flow width is large and the price per ton is high depending on the Ni price.

In order to overcome this disadvantage, one aspect of the present invention, the step of preparing a steel wire in which the aluminum-zinc plating layer is not formed, and forming a coating layer of titanium nitride having a thickness of 10 ~ 15㎛ on the surface of the steel wire It provides a method for producing a high-carbon steel wire for a steel core aluminum stranded wire having excellent electrical conductivity.

The present invention omits the Zn and Al hot-dip plating process in the manufacturing process of the conventional ACSR steel wire, and directly coated titanium nitride on the fresh steel wire. That is, the steel wire means a steel wire in which Zn and Al plating layers are not formed.

In order to suppress the linear expansion change according to the temperature of the high-carbon steel wire used universally, it was designed to form a separate coating layer on the steel wire. However, titanium nitride (TiN) was used as the material of the coating layer.

Titanium nitride has the following properties.

(1) electrical conductivity

Titanium nitride, for example, can be effectively added to the alumina matrix to lower the electrical resistance, and in the case of nano powder, this effect is even better. Increasing the amount of nano powder gradually decreases the electrical resistance, and if the volume content exceeds 20%, the electrical resistance remains stable.

(2) coating material

Applying titanium nitride to the coating improves antiwear and oxidative stability. Silicon carbide, zirconium carbide, etc., including commonly known titanium nitride, are known to have super abrasion resistance and self-lubrication when applied to metal coatings. The wear resistance is more than 100 times of the bearing metal, the coefficient of friction is 0.06-0.1 and the high thermal stability and damage protection.

As described above, when titanium nitride is used as the coating material, it can be seen that the wear resistance is effective in addition to the electrical conductivity.

The thickness of the titanium nitride coating layer was set to 10-15 μm.

If the thickness of the coating layer is less than 10 μm, there is a problem of volume expansion due to temperature change, and if the thickness of the coating layer is more than 15 μm, there is a problem such as a slight increase or saturation as compared to when deposited to a thickness less than that, such as manufacturing cost and unit cost.

Data of the linear expansion change characteristics according to the thickness of each coating layer can be confirmed through Table 2.

In an exemplary embodiment, the steel wire may include, by weight, C: 0.6-0.9%, Si: 0.2-1.5%, Mn: 0.2-1.0%, balance Fe and other inevitable impurities. However, the present invention is not limited thereto.

The reason for limiting the numerical values of the above components will be described as follows. Hereinafter, it is necessary to pay attention that the content unit of each component is weight% unless otherwise stated.

Generally, the steel wire used for ACSR has a C range of 0.6 to 0.9%, but the present invention can be used without limitation in addition to high carbon steel.

Si : 0.2 ~ 1.5 wt%

Si is dissolved in the ferrite base to increase the strength by the effect of strengthening the solid solution, is present in the ferrite grains, ferrite / cementite grain boundary, and with the Fe atoms of the general site or specific site in the cementite The solid solubility in cementite is extremely low because it cannot be substituted. It also suppresses the formation of cornerstone cementite in the roughened steel. Compared with C, V, Cr, etc. after the intermediate heat treatment, the effect of increasing the strength is small, but when the same content is added, it is known to be about 2 to 2.5 times (14kg / mm ² ) larger than Mn. It is one of the elements that inhibits cementite decomposition that occurs during wet or dry freshness. In order to achieve the target strength in the present invention, the addition of 0.2% or more is difficult to secure the strength when the addition is less than 0.2%. Therefore, it is desirable to limit it to 1.5% or less.

Mn : 0.2 ~ 1.0 wt%

Mn is a very useful element that forms a solid solution in the matrix structure, and is a very useful element or delays pearlite transformation. Therefore, the amount of Mn must be determined to form fine pearlite even at a slow cooling rate. When less than 0.2% is added, the strength effect is insignificant, and when it exceeds 1.0%, Mn segregation occurs and low temperature tissue is generated, which leads to rupture during freshness.

In an exemplary embodiment, the forming of the coating layer of titanium nitride may be performed using a magnetron sputter, but is not limited thereto.

Coating equipments include Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD), but it takes a long time in the chamber and a thin coating thickness. The coating can be several micrometers thick in a short time. The characteristics of the magnetron sputter are as follows.

Figure 1 includes a magnetron sputter used in the present invention.

Three magnetron sputter guns 2 are mounted in the chamber 3, and the magnetron sputter guns are provided with magnets and targets. When electric power is applied to the magnetron sputter, a magnetic field 5 is generated, and a mixture of argon and helium is injected to vaporize TiN from the target while maintaining an inert atmosphere, thereby depositing titanium nitride on the surface of the steel wire located in the center of the plating layer. 1) is formed.

Magnetron sputters are basically no major difference from ordinary ion sputters, except that they form a magnet or magnetic field around the target.

The disadvantage of the conventional two-pole sputtering method is that the deposition rate is relatively low. This is a big problem when mass production is required because it is related to production efficiency. In sputtering, the deposition rate is directly related to the ionization rate in the plasma. When the ionization rate of the discharge gas is low, the sputtering efficiency is low because the number of ions that must collide with the target which is the cathode is low, and the low sputtering rate is low. Because it imports. The sputtering rate here refers to the ratio of how many target atoms a cation can collide with the target to release.

Magnetron sputters are designed to solve this problem, with the addition of a permanent magnet or a magnetic field under the target to the base unit. In this case, the magnetic field (5) is applied around the target, which prevents electrons from escaping near the target and orbits around it, thereby increasing the density of electrons in the plasma directly above the target, and thus a mixture of electrons and Ar and He. The number of collisions of is rapidly increased. Therefore, since the generation of Ar cations that can collide with the target increases, the ionization rate increases, the final sputtering rate increases, and the deposition rate is improved. In addition, since the number of electrons colliding with the substrate is significantly reduced by trapping electrons around the target, heat is applied to the coating layer deposited on the substrate or steel wire, crack formation due to this, and the ionization rate is increased. Sputtering may occur at lower pressures.

The magnetron sputtering device illustrated in FIG. 1 may be installed in an inline or batch type after final drawing, but when installed inline, a coating layer may be uniformly formed on the surface of the steel wire. Since sputtering is performed at low or normal temperature, the electrical conductivity can be improved without affecting the tensile strength, so that the magnetron sputter is an effective device.

That is, the steel wire produced by the manufacturing method of the present invention is coated with titanium nitride on the surface does not change the tensile strength even at a temperature of 200 ℃ and the electrical conductivity does not decrease compared to room temperature.

In an exemplary embodiment, the forming of the coating layer of titanium nitride may include pressure: 10 ⁻³ to 10 ⁻⁶ torr, temperature: −40 ° C. to 25 ° C., gas: mixed gas of argon and helium, power: 10 To 1000 W, the substrate: may be performed under a TiN condition, but is not limited thereto.

If the pressure is other than 10 ^-3 to 10 ^-6 torr, the state of TiN in the coating, leading to a decrease in adhesion to the steel wire surface. The reason for limiting the temperature to −40 ° C. to 25 ° C. is not only the same as the reason for limiting the pressure, but there is a problem that the deposition time increases in other ranges. The reason for limiting the power to 10 to 1000 W is also the same as above. The reason for using a mixed gas of argon and helium is that it is advantageous to maintain an inert gas atmosphere than when used alone. When the deposition is performed under inappropriate conditions, the bonding strength of the coating layer may be reduced, and problems such as bubbles may be formed in the coating layer.

The substrate of the sputtering apparatus is replaceable. When TiN is used and power is applied, TiN is ionized and deposited on the surface of the wire.

Another aspect of the invention is, by weight, C: 0.6 to 0.9%, Si: 0.2 to 1.5%, Mn: 0.2 to 1.0%, the balance Fe and other unavoidably contained impurities, 10 to 15 on the surface The present invention provides a high carbon steel wire for a high-strength aluminum core strand having excellent electrical conductivity, including a coating layer of titanium nitride having a thickness of μm.

Hereinafter, the present invention will be described in detail with reference to Examples. However, the following examples are only for illustrating the present invention in more detail and do not limit the scope of the present invention.

[ Example ]

Invention material  One, Invention material  2 and Invention material  3 Preparation of

After ingot processing of high carbon steel with 0.82 wt% carbon and billet welding, it is reheated at 1000-1200 ℃ for 2 hours and then rolled with 13mmf wire. At this time, finish rolling temperature is 1000 ℃ and cooling rate for pearlite formation Was 8-10 ° C / sec. Subsequently, the wire rod was LP treated at 550-600 ° C. and manufactured to 5 mmf through dry drawing. Thereafter, titanium nitride was formed on the surface of the steel wire by using a magnetron sputter to form a thickness of 10 mm, 12.5 mm, and 15 mm, respectively.

Comparative material  1

After ingot processing of high carbon steel with 0.82 wt% carbon and billet welding, it is reheated at 1000-1200 ℃ for 2 hours and then rolled with 13mmf wire. At this time, finish rolling temperature is 1000 ℃ and cooling rate for pearlite formation Was 8-10 ° C / sec. Subsequently, the wire rod was LP-treated at 550-600 ° C. and hot-dipped at 400-500 ° C. to form an Al-Zn plated layer 40 mm, and was then manufactured to 5 mmf through dry drawing. The titanium nitride coating process is omitted.

Comparative material  2, Comparative material  3 and Comparative material  4, Manufacture

After ingot processing of high carbon steel with 0.82 wt% carbon and billet welding, it is reheated at 1000-1200 ℃ for 2 hours and then rolled with 13mmf wire. At this time, finish rolling temperature is 1000 ℃ and cooling rate for pearlite formation Was 8-10 ° C / sec. Subsequently, the wire rod was LP treated at 550-600 ° C. and manufactured to 5 mmf through dry drawing. Thereafter, titanium nitride was formed on the surface of the steel wire by using a magnetron sputter to form a thickness of 1 mm, 5 mm, and 7.5 mm, respectively.

Table 1 shows the change in tensile strength after maintaining the magnetron sputtered steel wire at 100 ° C. and 200 ° C. for 5 minutes. Here, the comparative material 1 is a steel wire formed by Zn and Al plating layer 40 mm after hot-dip plating, the titanium nitride coating layer thickness is 0mm, the comparative material 2 is a titanium nitride coating layer thickness of 1mm without forming Zn and Al plating layer, Comparative material 3 Titanium nitride coating layer thickness of 5 mm without forming a silver Zn and Al plating layer, Inventive material 1 is a steel wire formed with a titanium nitride coating layer thickness of 10 mm without forming a Zn and Al plating layer. In the case of the non-heat treated comparative material, the tensile strength value was about 1770 MPa at room temperature, and when the heat treatment temperature was increased to 200 ° C., the strength was increased by about 10 MPa, but it was confirmed that there was no significant difference from the material without heat treatment.

This is due to the increase in strength due to the adhesion of carbon, which was present in cementite, to the dislocation with increasing temperature. This slight increase in strength does not appear to be affected by the coating thickness of titanium nitride.

Tensile Strength (MPa) TiN coating thickness (㎛) As-drawn 100 ℃ 200 ℃ Inventory 1 10 1769 1771 1772 Comparison 1 0 1771 1775 1778 Comparative material 2 One 1773 1761 1767 Comparative material 3 5 1775 1772 1770

Specimens were taken from the surface and near the surface of the steel wire and the change in the linear expansion volume was measured and shown in Table 2 and FIG. 2.

Temperature (℃) Linear Expansion Volume (× 10 ^-6 ) Comparison 1 Comparative material 2 Comparative material 3 Comparison 4 Inventory 1 Inventory 2 Inventory 3 50 0.43 0.38 0.38 0.34 0.28 0.27 0.27 75 3.8 3.6 3.4 3.2 2.1 2.05 2.03 100 7.9 7.1 6.5 6.1 4.1 3.8 3.9 125 10.8 10.1 9.1 8.4 6.5 6.3 6.2 150 14.9 13.2 10.3 9.4 7 6.8 6.7 175 18.2 17.2 12 9.2 6.8 6.4 6.3 200 22.3 21 15 13.1 10.2 9.7 9.5 225 26 25 18 16.5 14 13.5 13.4 250 29.4 27 21.8 19.5 17 16.8 16.5

The linear expansion volume change is inversely proportional to the electrical conductivity. That is, the material having a small change in the volume of linear expansion has excellent electrical conductivity. In the case of Comparative Material 1, which was only hot-dip galvanized and not coated with TiN, the linear expansion volume was linearly increased as the temperature was increased from 50 ° C. to 250 ° C., thereby expanding up to 29.4 × 10 ⁻⁶ at 250 ° C. This temperature expansion makes them unsuitable for use in transmission lines.

In the case of Comparative Material 2, it was slightly decreased or it was determined to be within an experimental error range. On the contrary, the comparative material 3 showed little difference with the comparative materials 1 and 2 up to 125 ° C., but it was confirmed that the linear expansion change was much smaller at the temperature higher than that. Comparative Material 4 exhibits similar behavior as Comparative Material 3 in the graph. Invention material 1, invention material 2, and invention material 3, regardless of the temperature range, it was confirmed that the sensitivity with the increase in temperature is greatly reduced. Therefore, compared to the existing Al-Zn hot-dip galvanized material, it is determined that the present invention materials 1, 2, and 3 coated with TiN having a thickness of 10 to 15 μm are suitable for use in power transmission lines.

By coating titanium nitride on the surface, the linear expansion volume changes, and as the coating thickness increases from 1 to 15 mm, the temperature sensitivity of the linear expansion volume decreases, and as a result, it is judged that the electrical conductivity is improved. Can be.

ACSR generates significant heat because it is used as a high voltage cable. At this time, the temperature rises up to 200 ° C. Increasing the temperature inevitably increases the local lattice size due to the diffusion of C, N, etc., thereby increasing the linear expansion volume and disturbing the flow of current, thereby lowering the electrical conductivity. The TiN-deposited material with low temperature sensitivity is improved in electrical conductivity because there is almost no linear expansion volume change.

1: Titanium nitride plating layer deposited on the steel wire surface
2: magnetron sputter gun, titanium nitride target and magnet
3: chamber
4: argon and helium gas ion
5: magnetic field

Claims (5)

Preparing a steel wire in which no aluminum-zinc plating layer is formed; And
The method of manufacturing a high carbon steel wire for a high-strength conductive aluminum core wire comprising the step of forming a coating layer of titanium nitride having a thickness of 10 ~ 15㎛ on the surface of the steel wire. The method of claim 1,
The wire is in weight percent, C: 0.6-0.9%, Si: 0.2-1.5%, Mn: 0.2-1.0%, remainder Fe and other unavoidably contained impurities, high conductivity for high-strength aluminum stranded wire Method of manufacturing carbon steel wire. The method of claim 1,
Forming the coating layer of the titanium nitride is to be carried out using a magnetron sputter, a method of manufacturing a high carbon steel wire for a high-strength aluminum stranded wire having excellent electrical conductivity. The method of claim 3, wherein
Forming the coating layer of the titanium nitride is pressure: 10 ^-3 to 10 ^-6 torr, temperature: -40 ℃ to 25 ℃, gas: mixed gas of argon and helium, power: 10 to 1000 W, substrate: TiN The method for producing a high carbon steel wire for steel core aluminum stranded wire having excellent electrical conductivity, which is carried out under the conditions. By weight%, C: 0.6-0.9%, Si: 0.2-1.5%, Mn: 0.2-1.0%, balance Fe and other unavoidably contained impurities, the surface of the titanium nitride of 10-15㎛ thickness A high carbon steel wire for steel core aluminum stranded wire having excellent electrical conductivity, including a coating layer.

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