JPS60208463A - Galvanized steel wire having superior twisting characteristic and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a high tension galvanized steel wire which is not vertically cracked during twisting by galvanizing a steel wire having a composition obtd. by adding specified percentages of C, Si, Mn, Cr, Al, Mo and B to Fe. CONSTITUTION:A steel wire consisting of, by weight, 0.7-1.0% C, <=2.0% Si, <=2.0% Mn, 0.5-1.5% Cr, <=0.1% Al and the balance Fe with inevitable impurities or further contg. 0.1-0.3% Mo and/or 0.001-0.003% B is galvanized. The preferred Si content is 0.2-2.0% and that of Mn is 0.4-2.0%. A galvanized steel wire having about 220kg/mm.<2> tensile strength and superior twisting strength is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high tensile strength galvanized steel wire and a method of manufacturing the same. More specifically, we provide a new high-tensile galvanized steel wire that has twisting characteristics that are acceptable as a steel core wire for A-stranded wires with a tensile strength of 220 kg/mm2 class, and that does not cause longitudinal cracking during twisting, and its production. Regarding the method.

Conventional technology and its challenges Galvanized steel wires, represented by cored A9 stranded wire (hereinafter referred to as "AC3R") crude steel core wire, have recently become required to have particularly high tensile strength due to changes in their usage conditions. be.

For example, in the case of AC3R steel core wires, usage environments are emerging where higher tensions are applied due to higher transmission voltages.

Figure 1 shows the changes in domestic power transmission voltage by year, and as is clear from this figure, 1000 KV power transmission is planned for the late 1980s.

Currently, 500KV power is being transmitted, and 130kg/mI++
'Copper core a is used, but 100 OKV power transmission technology 180 kg/n+m' class steel core wire is required.

Additionally, some power companies are planning to use 220kg/w2 class copper core wire. Currently, 180 kg/mm2 grade AC3R steel core wires are known, but it is expected that future models will be required to have edges of 220 kg/mm or more. Since it is subjected to tertiary processing, it must not only achieve strength but also have sufficient workability and twisting characteristics.

Furthermore, as a known technique, for example, Japanese Patent Laid-Open No. 50-91517 discloses a high-strength steel wire containing 0.2 to 1.5% Cr, but this steel wire only has a strength of 115 kg/+1lII' class. Therefore, it does not have the strength expected as a steel core wire for AC3R in the future, and furthermore, it does not have the twisting characteristics required as a copper core wire for ACSR, which will be described later.

Furthermore, with the conventional 180 kg/mm2 class steel core wire for AC3R, properties such as torsion value deteriorate in the strength range of 220 kg/mm" or higher, so it was not possible to expect any further increase in strength. In addition, the strength after the lead bath is only about 130 kg / 1 ml' in the pearlite region, and when ordinary continuous drawing is performed, the degree of processing can only be about 85%, which makes it impossible to increase the strength. It was the reason.

In order to deal with such problems, the present applicant filed a patent application in 1983-
Based on JIS 5Wf11182 according to No.:1127fi (:r added 0.5 to 1.5%, P and S each 0.025% or less and f), 015% or less, and P + S fl, We proposed a high-tension Kametsuki steel wire with a limit of 0.03% or less, which resulted in a
Achieved a twist value of 20 times or more at a strength of the same level.

However, although the galvanized steel wire of the prior invention has a high tensile strength and a high twist value, it has the following problems.

Generally, steel wires that have been strengthened by wire drawing are subjected to anti-rust treatment such as hot-dip galvanizing, but there is a problem in that longitudinal cracks occur during twisting due to the effects of heat.

In particular, this phenomenon becomes more pronounced as the strength of the steel wire increases.
"The quality of AC3R steel core wire is trending towards higher strength"
This was the second biggest problem. For example, when a conventional galvanized steel wire is twisted, cracks occur in the radial direction of the cross section of the steel wire and develop in the twisting direction, that is, in a spiral shape, as shown in FIG. This problem is called vertical cracking, and this problem will be explained in more detail with reference to the attached drawings.

Figure 3 shows C=0.80%, 5i=0.30%, M low 0
．． 60%, Cr=O870%, P=0.022%, S=
This graph shows the relationship between the plating time and twist value of a plated steel wire when a steel wire processed with a 0.017% component and a reduction in area of 89% was plated at a zinc bath temperature of 450°C. be.

In FIG. 3, the horizontal axis shows the plating time, and the vertical axis shows the number of twists.

On the other hand, FIG. 4 shows the relationship between the tensile strength and torsion value of the plated steel wire having a relatively high content of P and S.

In Figures 3 and 4, white circles indicate torsion values without vertical cracks, black circles indicate torsion values with vertical cracks, and the right half of the white circles is filled in black. It shows the maximum number of twists, that is, the twist value, in a state where vertical cracks occur but no breakage occurs.

As shown in Figure 3, when the above-mentioned steel wire is galvanized as an anti-rust treatment, vertical cracking occurs during twisting due to the heat effect, and if the plating time is less than 80 seconds, vertical cracking will occur. It has occurred. Special feature 1: This effect becomes more pronounced as the strength of the steel wire increases. For this reason, as shown in Fig. 4, < 220 kg/m
M2 class tensile strength shows a twisting value of about 20 times, but
A vertical crack occurs after three twists.

When such longitudinal cracks occur, the strength of the galvanized steel wire during twisting decreases. This decrease in strength will be explained with reference to FIG. FIG. 5 shows the occurrence of vertical cracking during twisting of a galvanized steel wire with relatively high P and S values. That is, once vertical cracks occur, the strength of the steel wire decreases significantly. Therefore, A
When used as a C3R steel core wire and installed as an overhead wire, if this vertical crack occurs, there is a high risk of breakage, which poses a safety problem.

As a quality control problem for the drawn-strengthened high-strength Kametsuki steel wire that will be used as the steel core wire for future high-voltage power transmission AC3R,
This problem of vertical cracking is a problem that must be solved.

Purpose of the Invention The present invention addresses the above-mentioned future requirements for high-voltage power transmission.
Achieved the desired usage requirements for the steel core wire for 3R, with a strength of 220kg/mm' class that could not be achieved with conventional technology and good twisting properties.In particular, no vertical cracks occur during twisting, and the twisting strength is improved. The purpose of the present invention is to provide a new high-tensile galvanized steel wire that does not deteriorate and a method for manufacturing the same.

Structure of the Invention Thus, in order to achieve the above object of the present invention, as a result of long-term experiments and research, the present invention has disclosed that C: 0.7 to 1.0.
%, Si: 2.0% or less, Mn: 2. 0% or less, Cr: 0.5-1.5%, A9! : 0.1% or less, further contains Mo: O, 1 to 0.3% and B
:0.001 to 0.003% of either or both, the balance being Fe and unavoidable impurities, galvanized, and having good twisting properties. provided.

Furthermore, according to a preferred embodiment of the invention, Sl and M
n is limited to 0.2-20% and 0.4-2.0%, respectively.

Further, according to the present invention, the steel wire having the above-mentioned composition of the present invention is heated to 900 to 950°C and held for 5 minutes or more, and then heated to 57°C.
It is characterized by being immersed in a lead bath at 0 to 610°C for 5 minutes or more, pickling and lubricating it, then applying 87% or more wire drawing oil 1'11 and then hot-dip galvanizing. A patented manufacturing method is provided.

Hereinafter, the reason for limiting the components of the high-tensile galvanized steel wire of the present invention and the reason for limiting the conditions of the manufacturing method will be explained in detail.

C is the most important component for ensuring strength; if it is less than 0.7%, the target strength of 220 kg/+nm2 cannot be achieved, and if it exceeds 1.0%, the ductility will be significantly reduced due to the precipitation of pro-eutectoid cementite. It was set at 0.7% to 1.0% to avoid a decrease in the content.

Si is effective in increasing the fatigue properties and high-temperature strength of high-carbon high-tensile steel wires, but if it exceeds 2.0%, the ductility decreases significantly, so it is limited to 2.0% or less. On the other hand, if it is less than 0.2%, the fatigue properties and high-temperature strength increasing effect described in item 1 are not effective, so 0.2 to 2.0% is set as a preferable range.

Mn is effective in improving tensile strength in large diameter sizes by improving hardenability, but if it exceeds 2.0%, pearlite becomes coarse and the strength decreases, so 2.0%
Limited to the following. Furthermore, if it is less than 0.4%, the above strength increasing effect will be insufficient, so Mn: 0, 4 to 2.0%.
% was set as a preferable range.

A9. is necessary for deoxidizing treatment, but if it exceeds 0.1%, the workability deteriorates, so it was limited to 0.1% or less.

By adding Cr to steel types containing the above-mentioned components, hardenability is improved, lead patenting close to isothermal transformation is realized, and fine pearlite transformation necessary to achieve a predetermined strength is introduced. Moreover, the present inventor was able to make the first finding as a result of experiments that solid solution strengthening of ferrite can be expected by adding Cr.

The attached Figure 6 shows steel wires with varying Cr content.
It is a graph showing the tensile strength (indicated by x) and the area of area (indicated by ◯) of a sample that was heated to 0°C, held for 10 minutes, and subjected to lead patenting treatment for 5 minutes in a 600°C lead bath. As is clear from Fig. 6, good tensile strength and reduction of area can be obtained at the same time when the C content is in the range of 0.5% to 1.5%.
If it is less than 1.5%, the effect of improving hardenability is small and 1-min strength cannot be obtained, L segregation of more than 1.5% is likely to occur, bainite is generated locally, and the reduction of area is significantly reduced.

Therefore, the Cr content was limited to 0.5% to 1.5%.

Furthermore, Fig. 7 shows a curved lead-plated steel wire that has been heated and held with a different C content and subjected to lead patenting, then drawn using a high degree of processing, and then galvanized into a bent lead-plated steel wire. It is a graph showing the torsion value, reduction of area, tensile strength, and tensile strength immediately after lead patenting.

As is clear from Fig. 7, in order to have a tensile strength of 220 kg/ll1m2 or more, and also to have good twisting value, narrowing, and tensile strength14), it is optimal for C' to be in the range of 0.5 to 1.5%. It can be seen that the mechanical properties of the galvanized steel wire improve dramatically within this range.

Both Mo and B are elements that improve hardenability, but they also have the effect of suppressing grain boundary embrittlement caused by P.

Steel wires containing P at the usual level of 0, 02 (approximately 1%) are t-
As shown below, when the plated wire strength is 220 kg/mm" class,
Vertical cracks occur during twisting. The present inventors hypothesized that this longitudinal cracking was caused by grain boundary embrittlement due to P, and conducted experiments to determine the effect of Mo and B on suppressing grain boundary embrittlement.
It was discovered that the addition of B causes vertical cracking.

That is, by adding 0.1 to 0.3% of Mo, the occurrence of the above-mentioned vertical cracks is suppressed. However, if it is less than 0.1%, this effect is insufficient, and if it exceeds 0.3%, the effect of addition is saturated, so it is set in the range of 0.1 to 0.3%.

! , B by 0.001 to 0.003% also suppresses vertical cracking. However, if it is less than 0.001%, this effect will be insufficient, and if it exceeds 0.003%, it will cause hot brittleness, which may cause trouble during rolling, so it should be in the range of 0.001-0.003%. did.

FIG. 8 shows an example of improvement in twisting characteristics by adding Mo and B. As shown in the figure, 210k when no Mo or H is added.
With a tensile strength of g/mm', vertical cracking occurs after twisting 2 to 4 times,
At 230 kg/mm2 grade, the twist value becomes extremely low F, but when Mo5B is added, a twist value of 20 times or more is obtained without vertical cracking even at a strength level of 220 kg/mm2, and even at 230 kg/7 mm2, the twist value is 20 times or more. It is possible to achieve a twist value of more than 3 times.

Next, the reason for limiting the conditions of the manufacturing method of the present invention will be explained.
The conditions for the lead punting treatment and wire drawing oil 1- of the present invention are the following three indicators: (1) workability of 85% or more.
(2) maintain good twisting characteristics with a stiffness of 85% or more; (3) after lead patenting, 140 to 145 kg /
This was determined in order to secure the strength of w2 and maintain the ductility of 40% or more.

(3) In order to secure a strength of 140 to 145 kg/am" after the lead bath and a ductility of 40% or more, it is necessary to completely decompose chromium carbides, complete pearlite transformation,
It is necessary to process the steel wire under patenting conditions that satisfy three points: prevention of coarsening of T grains;

Figure 9 shows the heating temperature of the steel wire having the above composition range of the present invention.
In the range of 50 to 1000℃, the lead bath temperature is 500 to 700℃.
The tensile strength (not shown by the upper line in the figure) and the area of area (not shown by the lower line in the figure) of the steel wires obtained by processing the steel wires at varying temperatures in the range of °C are shown.

As is clear from Fig. 9, the desired strength and ductility can be obtained in the range of 900 to 950°C, and the temperature of the lead bath is 570°C.
Maximum strength is obtained in the range of 610°C to 610°C.

Referring again to FIG. 7 described above. This figure 7 is
The torsion value of a galvanized steel wire in which steel wires with different Cr contents are heated and held and lead patented according to the method of the present invention, drawn with different working degrees, and then galvanized, Drawing, tensile strength, and tensile strength immediately after lead patenting are shown.

As shown in Figure 7, 220kg/mm” 1211
In order to have a tensile strength of : and obtain a good twist value, reduction of area, and tensile strength, a working ratio of 87% or more is required.

As detailed above, according to the present invention, 220 kg/mm
The first high-tensile curved lead plated steel wire for ΔCSR has a tensile strength of 2 or more and has good twisting properties, especially no vertical cracking during twisting and no decrease in twisting strength.

Hereinafter, the present invention will be explained with reference to Examples, but these Examples are merely illustrative of the present invention, and of course do not limit the scope of the present invention.

Example: A steel wire of test steel having the composition shown in Table 1 was prepared from 900 to 1)
After heating to 50℃ and holding for 5 minutes or more, 570-610℃
The wire was immersed in a lead bath for 5 minutes or more, subjected to pickling and lubrication treatment, then wire-drawn to 87% or more, and then hot-dipped Inr lead plated. Article 171il of the manufacturing method of the present invention
lt! Specific conditions were adopted to achieve the highest strength (i%) while ensuring a reduction of 40% or more in the pearlite region corresponding to each test steel.

In the test steel with Δ1)1, the influence of the C content was investigated.

In the B Jii test steel, the influence of Mo and B contents was investigated.

In the test steels of Group C, the influence of the Cr content was investigated.

In the (Jli test steel) of group l), the influence of the Si content was investigated.

E I! In the T test steel, the influence of Mn content was investigated.

In the test steels of Group F, the influence of the A9 content was investigated.

Note that all conditions other than the material components and heat treatment conditions were the same except for the degree of wire drawing.

In each case, the galvanizing was carried out by passing the wire through a zinc bath at 450° C., and the wire passing time was set to a condition where the highest strength was obtained in a region where no vertical cracking occurred during twisting.

The obtained galvanized steel wire was subjected to various -C mechanical tests, and the results are shown in Table 2.

/' / / / To explain the results shown in Table 2, the A1 test steel, which has a high C content beyond the scope of the present invention, has a higher strength after the lead bath and after plating than the A2 and A3 test steels. is low, 220
There is no mention of tensile strength in the kg/mm" class.

The Mo and B contents of the test steels B1, B2, and B3 are outside the range of the present invention. That is, the test steel of B1 is M
Contains no O or B, resulting in vertical cracking,
Torsion value is also low. The B2 test steel had a low Mo content;
This also causes vertical cracking and has a low torsion value. The sample steel B3 has too high a content of both MO and B and is hot brittle, resulting in poor workability, and as a result, its strength and torsion value are also insufficient.

The test steels of group 0 are for examining the influence of Cr, and C1 has a low Cr content, a low torsion value, and a significantly lower tensile strength and reduction of area than the steel of the present invention. On the other hand, in the case of C2 test steel, the Cr content was as high as 2.1%, so the ductility deteriorated and the torsion value also decreased significantly.

The sample steel of Dl is within the scope of the present invention, but due to the low S1 content, B2 and B3 according to the preferred embodiment of the present invention.
The tensile strength is slightly lower than that of the sample steel. On the other hand, B
Test steel No. 4 has a high Si content of 2.22%, so its ductility is reduced and its twisting properties are also significantly deteriorated. A similar tendency was observed in the test steels El (low Mn) and B4 (too high Mn), which were investigated for the influence of Mn.

Group F investigated the influence of the content of A, and in the case of test steel B3, which contains A9 beyond the scope of the present invention, all of the strength, ductility, and torsional properties were significantly deteriorated. There is.

When the test steels of the present invention were used in contrast to these comparative steels, all had the desired tensile strength, high torsion values, and no longitudinal cracks occurred.

Effects of the Invention As detailed above, the present invention has succeeded in providing a high-tensile galvanized steel wire that has a tensile strength of 220 kg 7 mm2 grade and excellent twisting characteristics and does not cause vertical cracking during twisting, and a method for manufacturing the same. This is what I did. Such a high tensile strength galvanized steel wire of the present invention can be suitably used as a steel core wire for AC3R for high voltage power transmission.

In the present invention, C5Si, MnXCr, and A9 are used so that the tensile strength, reduction of area, workability, and twisting properties are within the range suitable for a 220 kg/mm'' class AC3R steel core wire.
, B), and the B content has been determined experimentally. Therefore, the high tensile strength galvanized steel wire according to the present invention does not generate vertical cracks when twisted, and does not lose strength in the twisted state.

Although the use of the galvanized steel wire of the present invention has been described above as a steel core wire for AC3R, it goes without saying that the galvanized steel wire of the present invention can also be used for other uses.

[Brief explanation of drawings]

Figure 1 shows the changes in domestic power transmission voltage by year. FIG. 2 is a perspective view of a vertical crack that occurred during twisting of the steel wire. Figure 53 is a graph showing the relationship between the thermal influence due to galvanizing and the twist value for a galvanized steel wire containing P and S in the normal range. FIG. 4 is a graph showing the relationship between tensile strength and twist value for the plated steel wire. In Figures 3 and 4, white circles indicate torsion values without vertical cracks, black circles indicate torsion values with vertical cracks, and the right half of the white circles is filled in black. It shows the maximum number of twists, that is, the twist value, in a state where vertical cracks occur but no breakage occurs. FIG. 5 shows changes in twisting torque in a twisting test of a galvanized steel wire containing P and S in a normal range, with the horizontal axis showing the number of twists and the vertical axis showing the twisting torque. Figure 6 shows the tensile strength (indicated by x) and reduction of area ( (indicated by ○). FIG. 7 shows a galvanized steel wire that has been subjected to heat holding and lead patenting according to the above method of the present invention, and then drawn to different working degrees, and galvanized steel wire with a different content of C. It is a graph showing the twist value of the wire, the aperture, the tensile horn, and the tensile strength immediately after lead patenting. FIG. 8 is a graph showing the effect of improving twisting characteristics by adding MO and B. FIG. 9 shows the tensile strength (indicated by the upper line in the figure) and the area of area (indicated by the lower line in the figure) of steel wires having the composition range of the present invention treated at different heating temperatures and lead bath temperatures. Patent Applicant Sumitomo Metal Industries Co., Ltd. Representative Patent Attorney Masahiko Arai Figure 7 0 1.0 2.0 Cr (%) Figure 8 Figure 9

Claims (1)

[Claims] (+) C: 0.7 to 1.0%, Si: 2.0% or less, Mn: 2.0% or less, ([r・(), 5 to 1.5%, A father: 01% or less, further contains Mo: 0.1 to 0.3% and B
: 0.001-tl, Ofl: 1% or both, the balance consists of Fc and non-FiJ impurities, galvanized lt, high tensile strength characterized by good twisting properties Galvanized steel wire. (2) The high tensile strength galvanized steel wire according to claim 1, characterized in that: Si: 0.2 to 2.0%, Mn: 0.4 to 2.0%. (3) Contains: C: 0.7 to 160%, Si: 2.0% or less, Mn: 2.0% or less, Cr: 0.5 to 1.5%, A father: 0.1% or less Further, a steel wire containing one or both of Mo:O,l~0.3% and B:0.00]~0.003%, with the balance consisting of Fe and inevitable impurities, was After heating to ℃ and holding for more than 5 minutes, 57
The patented method is characterized in that it is immersed in a lead bath at 0 to 610°C for 5 minutes or more, pickled and lubricated, then subjected to 87% or more wire drawing oil]2, and then hot-dip galvanized. A method for manufacturing high-tensile galvanized steel wire.