JPS6277442A - High-tensile steel wire excellent in ductility - Google Patents

Abstract

PURPOSE:To manufacture a high-tensile steel wire excellent in ductility by providing the surface of a steel wire, which has a specific composition and in which the difference of hardness between the center and surface is controlled to a specific value or below, with residual compressive stress according to the strength of the steel wire. CONSTITUTION:The steel wire has a basic composition consisting of, by weight, 0.4-1.0% C, <2.0% Si, 0.2-2% Mn, <0.02% P, <0.02% S, <0.01% N and the balance Fe or further contains 1 or >=2 kinds among 0.05-3% Cr, 0.01-1% Mo, 0.01-1% W, 0.05-3% Cu, 0.1-5% Ni and 0.1-5% Co or 1 or >=2 kinds among 0.001-0.1% Al, Ti, Nb, V and Mg and 0.0003-0.05% B independently or in combination. Furthermore, the difference of hardness between the center and surface of the steel wire is limited to <=100 vickers hardness and the surface is provided with a residual compressive stress of (0.05sigma+13)-(0.35sigma+28)kgf/mm<2> according to the strength (sigma) of the steel wire, so that high-tensile steel wire excellent in ductility can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high tensile strength steel wire with excellent ductility.

(Prior Art) In recent years, there has been an increasing demand for higher strength in hard steel wires such as steel wires for ropes, @ wires for reinforcing tires, steel wires for reinforcing optical fiber cables, and steel powder for long bridges.

Although intensive research has been carried out on increasing the strength of hard steel wires, the lack of established technology to prevent the deterioration of ductility that occurs with increased strength is a constraint. It has not yet reached the point where high strength has been achieved. For example, torsional properties, which are an important measure of ductility, are described in Wire Journal, vol. 16.
44 (1983), p. 50, this can be improved by subjecting the steel wire after drawing to a high-temperature bluing treatment, but such high-temperature treatment not only leads to a decrease in strength; With thin wires such as tire reinforcing steel wires, deterioration in ductility due to surface oxidation cannot be avoided.
There are limits to the application of this method.

On the other hand, instead of using such a heat treatment method, ductility can be improved by applying skin/mother wire drawing to the steel wire after drawing to release the tensile residual stress that exists on the surface of the steel wire after drawing. Efforts are also being made to improve it. But 19
Such measures as described in "Effect of die schedule on mechanical properties and residual stress of steel wire" in the material submitted by the 20th Wire Drawing Technology Subcommittee of the Japan Society for Plasticity Processing, published on November 16, 1984. ductility is hardly improved.

Thus, at present, no sufficient method has been found to improve the ductility of steel wire.

(Problems to be Solved by the Invention) The object of the present invention is to provide a steel wire with excellent ductility that eliminates these drawbacks.

(Means for Solving the Problems) As a result of various studies to provide a steel wire with excellent ductility, the present inventors found that the steel wire has a specific composition and the hardness difference between the center and surface of the steel wire is determined by Vickers hardness. A compressive residual stress is actively applied to the surface of the steel wire, which is regulated to 100 or less, and the compressive residual stress is adjusted to (0.05σ + 13) according to the steel wire strength σ.
It has been found that a hard steel wire with excellent ductility can be obtained by controlling the hardness within the range of 0.35σ+28)42.

That is, the gist of the present invention is as follows.

(1) Contains C004 to 1.0%, Si 2.0% or less, Mn 0.2 to 2% by weight, P 0.02% or less, S 0.02% or less, and N 0.01% or less. limit,
The remainder is free of iron and unavoidable impurities, and the difference in hardness between the center and the surface is 100 or less on Vickers hardness, and
Depending on the steel wire strength σ (0.05σ+13) to (0.35
A high tensile strength steel wire with excellent ductility, characterized by having a surface compressive residual stress of σ+28) kgf/m2.

(2) Contains 0.4-1.0% by weight, 2.04 or less Si, 0.2-2% un, 0.02% or less P, 80
．． 02 or less, N 0.011 or less, and Cr
0.05-3%, Mo0.01-1%, W0.01-1
%, Cu 0.05~3%, NI0.1~5chi, Co0
．． Containing one or two or more of the following: 1 to 5, the remaining iron and unavoidable impurities are free, and the difference in hardness between the center and the surface is 100 or less in terms of Vickers hardness, and according to the steel wire strength σ (Q )5σ+13) Pe035σ+28) kgf/■2
A high tensile strength steel wire with excellent ductility, characterized by having zero surface compressive residual stress.

(3) Contains 0.4 to 1.0% by weight, Si 2.0 or less, Mn 0.2 to 2%, P 0.02% or less, 8
0.02% or less, N 0.0001-0.1% or less, At0.001-0.1%, Ti0
．． 001-0.1%, Nb0. ool ~0.1
Chi, V0.001~0.1%, B0.0003~
0.05%, Mg0.001-0.1%, one or two
Contains more than 10% of iron and no residual iron and unavoidable impurities.
And the difference in hardness between the center and the surface is 100 in terms of Vickers hardness.
A high tensile strength steel wire with excellent ductility, characterized in that it has a surface compressive residual stress of (0β5σ+13)da035σ+28)kg f/w2 according to the wire strength σ.

(4) C0.4-1.0% in weight fr%, Si
2.0% or less, Mn0, 2-2%, P0.
024 or less, 80.021 or less, N0.011 or less, and Cr 0.05-3%, M.

0.01~1%, W0.01~1, Cu0.05~3
%, N1011-5T, Co0.1-5T, and further At0.001-0.1T, T
i0.001~0.001~0.1%, Nb 0.00
1-0.1, V0. OOl ~0.1%, B0.000
Contains one or more of Mg0.001 to 0.1, with the balance being iron and unavoidable impurities, and the difference in hardness between the center and surface is 1 in terms of Vickers hardness.
00 or less and depending on the steel wire strength σ (0.OSσ+1
3) A high-tensile steel wire with excellent ductility, characterized by having a surface compressive residual stress of ~(0.35σ+28) kgf/-.

The present invention will be explained in detail below.

(effect) First, the reason for limiting the steel wire composition as described above will be described.

If C is less than 0.4%, the required strength cannot be obtained, and if it exceeds 1.0 inch, the ductility deteriorates significantly, so the content is limited to 0.4 to 1.0 inch.

St is added mainly to take advantage of its solid solution hardening effect, but if the amount added exceeds 2%, the reduction in ductility becomes significant, so the upper limit was set at 2.0%.

Mn is added to ensure hardenability and fix S, but
If it is less than 0.2%, S will not be fixed sufficiently;
Even if it is added in excess of 0%, the hardenability will no longer increase.
．． It was limited to 2 to 2.0 inches.

It is better for P and S to be slightly smaller in order to improve ductility.

If each exceeds 0.02%, it will have a significant negative effect on ductility, so it is limited to 0.02% or less. If N exceeds 0.01%, it will have a negative effect on ductility, so it is limited to 0.01% or less.

The above is the basic component system of the 5IA wire that is the object of the present invention, but in addition, (A) Cr 0.05-3T, M.

0.0 1~1%, W0.0 1~1
%, Cu 0.05-3chi.

One or more of Ni0.1-5%, Co 0.1-5%, or (B) Al0.001-0.1%, T10.
001~0.1%, Nb0.001~0.1
%, V 0.001~0.1%, B0.0O0
3-0805%, Mg0. O0. ~0.001~0.1
% of one or more of (4) and (B).

First, Cr, Mo, W, Cu, Ni
, Co 11 is added for the purpose of increasing strength and corrosion resistance, but less than 0.05% Cr, Mo 0.01
Less than 4, W less than 0.01%, Cu less than 0.05%, Ht
If the content is less than 0.1% and Co is less than 0.001 to 0.1%, the effect on reinforcement and corrosion resistance will not be observed, so Cr is 0.05% and Mo is 0.01%.

W0.01%, Cu0.05%, NI0.1% and Co
The lower limit was set to 0.1.

On the other hand, Cr more than 3%, Mo more than 1%, W more than 1%, Cu 3
%, Nl more than 5% and Co more than 5%, the effects of these elements on strengthening and corrosion resistance are saturated, while the effect of reducing ductility becomes significant, so Cr is 3%.

Mo 1%, W1%, Cu 3%, Nl 5%
and Co5% as the upper limit. From the viewpoint of ductility, it is desirable to suppress the total amount of these alloying elements to 7 or less.

Then kA, TI, Nb, V, B and M
g is added for the purpose of fixing N and S to improve ductility, but Al is less than 0.001%, Tl is 0. O0.
Less than 1%, Nb less than 0.001%, V less than 0.001%,
If B is less than 0.0003% and Mg is less than 0.0014%, N and S cannot be fixed, so Al0.
001%, Nb 0.001%.

V 0.001%, B U, 0003% and Mg0
．． The lower limit was set at 0.001%.

On the other hand, AA exceeds 0.1%, TI0.1. %, Nb 0.
More than 1%, V0.1%, more than 80.05% and Mgo:x
At more than 0.001% to 0.1%, the N and S fixing effects of these elements become saturated, while the ductility deterioration effect due to nitrides and sulfides of these elements becomes significant.
T10.1%.

Nb 0.1%, V0.1%, B0.05% and Mg
The upper limit was set to 0.1%. Note that the total amount of these elements is 0
．． From the viewpoint of ductility, it is desirable to keep it to 2- or less.

Next, for the maximum vf@ of the present invention, the hardness difference between the center and the surface is regulated to 100 or less on the Pinkers hardness, and the steel gauze is applied to the surface according to the steel wire strength σ (0.05σ + 13
) to (0.35σ1,28) kgf/2. The reason why the hardness difference between the center and surface of the steel wire and the compressive residual stress of the steel wire were determined in this way will be described below.

', (j) The ductility of a wire is usually determined by the elongation in a tensile test, the reduction of area, the number of rotations until breakage in a twisting test (twisting value), the form of breakage at that time, or a bending test.

Among these ductility evaluation criteria, the one that deteriorates most significantly as the strength of the steel wire increases is the fracture mode in the twisting test.

Figure 1 shows the torsion test! This diagram schematically shows the fracture mode of IJml, and ta) shows a normal rupture situation, but as the strength increases, the fracture n2 shown in the same figure (b) also occurs. The frequency of abnormal breaks increases.

This is done by gripping jig 3 as shown schematically in Figure 2.
This is due to the occurrence of cracks 2 in the longitudinal direction on the surface of the wire gauze 1 during the twisting test conducted by gripping the steel wire. It is possible to think that it is true.

The ductility of steel wire in the circumferential direction is most likely to deteriorate as the strength increases.In fact, during bending of steel wire, vertical cracks may occur in the longitudinal direction even though bending does not break. This can also be understood from the fact that when stranded wires are processed, vertical cracks may occur even though the strands do not break.

In this way, the fracture mode of the twisting test is! It can be said that this is the most important ductility evaluation scale for i14 wire.

The present inventors have found that - regulating the hardness difference between the center and surface of the wire and having the main wire have compressive residual stress on its surface is extremely effective in improving the circumferential ductility of the copper wire. We found this and investigated the appropriate range of hardness difference and compressive residual stress. In other words, with the goal of suppressing the incidence of abnormal fractures in torsion tests to 10% or less,
220kgf/m”.

The residual stress and We investigated the relationship between hardness differences and the incidence of abnormal fractures in torsion tests.

As a result, a steel wire with a tensile strength of 152 yf/w" has a tensile strength of 20
Yuf/un”, 235 and 9f/-2 steel wire
5 Yuf/lel.

316 to 9fi steel wire is 29 to 9f/amount", 377
The torsion test requires that a single wire of Yuru has a compressive residual stress of 31 kgf/wJ or more, and that the difference in hardness between the center and surface of the copper wire is limited to 100 or less, preferably 60 or less in terms of Vickers hardness. It has become clear that this is necessary in order to suppress the incidence of abnormal fractures to 10% or less. Organizing the compressive residual stress n obtained here with respect to the tensile strength σ of the copper wire, (0.05σ + 13)kl? f/1rr
The relationship r2 was obtained experimentally. Here, the hardness difference is 10
If it exceeds 0, (0.05σ+13)kgf/vr
Even if a compressive residual stress of rn2 is applied, it is not possible to overcome the negative effects of the internal non-uniformity of the structure due to the difference in hardness of the steel wire itself, so the abnormal rupture rate in the torsion test is kept below 10%9. I couldn't do that. It has also been found that when the hardness difference exceeds 100, cracks may occur inside the steel wire when compressive residual stress is mechanically applied.

On the other hand, even if the hardness difference was within 100, it was not possible to suppress the abnormal rupture rate to 10% or less when the compressive residual stress was less than (0.05σ+13) kgf/ha2.

In addition, if the incidence of abnormal rupture in the twisting test is 10% or less, then
For example, when actually processing steel wire, there is no need to worry about the occurrence of vertical splits.

For these reasons, the lower limit of the difference in hardness between the center and surface of the steel wire and the compressive residual stress imparted to the surface of the steel wire was determined.

On the other hand, the larger the compressive residual stress on the surface of the steel wire, the better it is for improving the ductility in the circumferential direction, but as is well known, the tensile residual stress at the center of the steel wire increases in proportion to the compressive residual stress on the surface. do. When the tensile residual stress at the center of the steel wire increases, a split n occurs at the center, leading to abnormal fracture during the twisting test. Therefore, w41f! The upper limit of the compressive residual stress n allowed on the surface of the steel wire is naturally determined by the relationship between j and the center division n. Therefore, the present inventors investigated the relationship between the occurrence of abnormal fracture in a twisting test due to a crack at the center of the steel wire and compressive residual stress using one of the four types of steel described above.

As a result, for steel wire with a tensile strength of 152 and 9f/■2,
80 kgf/m", 235kl?f/+m" chain line, 113 has 9f/wr2.316 has 9f/wn
” steel wire is 136 XJ f/lrt+” +377
It has become clear that abnormal fracture occurs in K17m2 steel wire when the surface compressive residual stress exceeds 160 kgf/m2. This compressive residual stress is proportional to the steel wire strength σ, (0.35σ+28) kgf/m”
It is given experimentally. Upper limit of compressive residual stress (0.
35σ+28)kgf/τ2 was determined in this way.

In addition, as a means to suppress the hardness difference between the center and the surface of the steel wire to 100 or less, preferably 60 or less, for example, low-temperature casting in the continuous casting process, electromagnetic stirring, or It is effective to soak the pieces at high temperatures.

Note that the compressive residual stress may be applied mechanically by any means, but as a means for applying the compressive residual stress within the range limited in the present invention to the surface of the steel wire after wire drawing, for example, roller rolling or shot processing may be used. Peening processing can be used.

Such compressive residual stress may be applied in any process after wire drawing until the steel wire is used as a product, but if it is applied after bluing or plating, It is preferable to perform the bluing treatment again at a temperature of 250° C. or lower in order to improve the stress relaxation properties of the steel wire.

Note that the strength of the steel wire is not particularly limited, but the tensile strength is 130
The present invention is highly effective when applied to a w4 line of 9 f/lxm'' or higher.

The steel wire of the present invention also has excellent fatigue properties, corrosion fatigue properties, slow n-fracture properties, stress cracking properties, and setting properties.

The steel wire of the present invention is also effective in improving the durability and fatigue properties of products made using the steel wire, such as ropes, S-section knotted tires, and steel wire-reinforced plastics.

Next, the effects of the present invention will be explained in more detail with reference to Examples.

(Example) Composition, wire diameter, and tensile strength of the wire used in the examples.

Center hardness 9 of Ryo Kasuri, surface hardness and hardness difference between them, lower limit of compressive residual stress on steel wire surface limited in the present invention (0.05
σ+13) and upper limit value (035σ+28), residual stress existing on the surface of the steel wire used in the example, and twisting test and fatigue test for these steel wires.

The results of corrosion fatigue tests, delayed fracture tests, fatigue tests, etc., and the results of fatigue tests of products manufactured using these gA healds are also listed in Table 1.

In addition, in the same table, the criteria or means for judging various test legs are as follows.

First, the residual stress symbol (+) indicates tensile residual stress, and the - symbol (-) indicates compressive residual stress.

Next, the abnormal rupture rate in the twisting test is shown in Figure 1 (b).
The ratio of occurrence of abnormal fracture shown in 1 is shown.

Fatigue limit indicates the fatigue limit stress in a rotating bending fatigue test of steel wire.

Cord breakage rate in tires is 100,000 kn at a load of 500 yu
+ Indicates the damage rate of the cord in the tire after driving.

The shear modulus indicates the residual shear strain after applying a thread stress of 60 degrees of tensile strength to the steel wire and leaving it for 96 hours.

Delayed destruction time is 0. 80 to 9 f/m2 in IN hydrochloric acid solution
It shows the time until rupture when a tensile stress of .

The fatigue limit ratio of a plastic plate is 1+"5I. The fatigue limit of a plastic plate reinforced with 100 steel wires of 1+W+thickness x 10mm width is compared with the fatigue limit of a comparison example, test number 37, as 1.

Corrosion fatigue life indicates the number of rotations of a steel wire until it breaks under a load of 20 kg7/wm2 in a fatigue test.

The stress corrosion cracking time indicates the time until rupture when a tensile stress of 70 kgf/wn'' is applied in a 0.5 thiacetic acid + 5% saline solution.

Rope fatigue limit ratio is JIS No. 1 rope's fatigue limit,
Assuming that the fatigue limit of the rope manufactured using the single wire of Comparative Example 51 is 1, the fatigue limit of the rope manufactured using the copper wire of Invention Example 50 is shown in comparison.

Next, in Table 1, Testers 1 to 9 are related to Invention 1, among which A 1 , 3, and 5 are examples of the present invention, and the others are comparative examples.

A1 and 2 have a θ diameter of 0.25 and a tensile strength of 344 f/m?
These are the results for steel wires with the same composition, and the difference in hardness between the center and surface is 32, which is 103 kgf/M.
The abnormal fracture rate in the twisting test of A1 copper wire having a compressive residual stress of 2 is O. Note that the compressive residual stress is imparted by roller rolling.

On the other hand, the difference in hardness between the center and the surface is 112, which is 40 kgf/w2
The abnormal rupture rate of the second wire with tensile residual stress is 90
It can be seen that the steel wire of the present invention exhibits excellent ductility. The steel wire of the present invention also has excellent fatigue properties and durability in tires.

A3 and 4 have a wire diameter of 2.6 mm and a tensile strength of 170 kll.
The results are for steel wires with the same composition of f/wm, and the difference in hardness between the center and the surface is 45, and it is 50k.
The chain line of flat 3, which has a compressive residual stress of lil f / m'', has an abnormal rupture rate of 0 and is excellent in ductility, but the steel wire of 4, which has a hardness difference of 120, has an abnormal rupture rate of 75 and has excellent ductility. The residual stress is given by shot peening and the shaft 1 A5 has a wire diameter of 1.2 m and a tensile strength of 221' to 9 f.
/lt,'' The results are for a steel wire with a hardness difference of 50 between the center and the surface, the abnormal rupture rate is 0, and the ductility is excellent.The compressive residual stress was given by shot peening.

It is clear that A 6 , 7 , 8 , and 9 all have abnormal rupture rates of less than the sieve and lack ductility because the composition, hardness difference between the center and surface, or residual stress are outside the scope of the present invention.

Next, A18 to A20 are related to invention 2, and this butcher 1
0.12.13, 15, 17, 18°21.22 are examples of the present invention, and the others are comparative examples.

Base 10.1iIfi wire diameter 0.25 m, tensile strength 284
The results are for steel wires with the same composition of 9 f/m'', and the difference in hardness between the center and surface is 38 and 80 kl?,?
An A10 steel wire with a compressive residual stress of ``/wn2'' has an abnormal rupture rate of tci5 in a torsion test, while the hardness difference between the center and the surface is 109, and an All steel wire with a tensile residual stress of 40 kgf/m''. It can be seen that the steel wire according to the present invention has an abnormal rupture rate f'i of 95%, which shows that the ductility of the steel wire decreases extremely quickly.

The compressive residual stress was applied by roller rolling.

A12 has a wire diameter of 2.5 mm and a tensile strength of 205 yuf/snow 2.
The result is a steel wire with a compressive residual stress of 28 kgf/m" and excellent ductility with an abnormal rupture rate of UO. In this case,
Compressive residual stress is given by shot peening.

A13 and 14 shore wire diameter 0.6 m, tensile strength 254 to 9
This is an example regarding the chain line having the same component composition of f/1an2, and the abnormal rupture rate is 5% for the steel wire of Ya 13 which has a hardness difference of 70 and a compressive residual stress of 68 kgf/■2. The abnormal rupture rate of the copper wire of No. 14 with a hardness difference of 108 and a tensile residual stress of 9 f/mF at 50 is 10.
It is clear that at 0%, the ductility of the steel wire of the present invention is very low. In this case, the compressive residual stress 1-i was given by the roller rolling process.

A15 and 16 have a wire diameter of 4.5 m and a tensile strength of 195 to 9
The results are for copper wires with the same composition of f/vm'', and the hardness difference between the center and surface is 43 and 45kli.
A flat 15 steel wire with a compressive residual stress of 'f/m'' has an abnormal rupture rate of O and excellent ductility, but the difference in hardness between the center and the surface is 131 and 110, which is as much as 9 f/m''. The abnormal rupture rate of the A16 steel wire having the following properties is 60 inches, indicating poor ductility. Compressive residual stress was applied by roller rolling.

Ya 17 has a wire diameter of 2.5 wa and a tensile strength of 171 ko f.
/m2 hardness difference 58 and compressive residual stress of 44 kgf/m'' galvanized W4 wire, abnormal rupture rate is O
It has excellent ductility. Compressive residual stress was imparted by shot peening.

A18-20 has a wire diameter of 8m and a tensile strength of 180ff/van.
2, the difference in hardness between the center and the surface is 50 and the compressive residual stress of 35 kgf/wm2 is 418, the abnormal rupture rate is O, and the difference in hardness between the center and the surface is 113. A19 with a tensile residual stress of 20 kgf/m2 and a hardness difference of 119 between the center and the surface of 1
A with only a compressive residual stress of 5 kyf/1 type
The abnormal breakage rate for the steel wire of 20% is 960%, which is 40%.
It can be seen that the ductility of the steel wire according to the present invention is just n. Here, on the front line of A18, shot peening, A20
A compressive residual stress was applied to the steel wire by roller rolling.

The steel wire according to the present invention also has poor p-ability and slow-n fracture properties.

Ya 21 has a wire diameter of 1.2" and a tensile strength of 220 kg f/
am'' hardness difference between center and surface is 26, 72 klf/m2
Ifx 22 has a compressive residual stress of
．． 6 simple, tensile strength 186 kgf/m2, hardness difference 56
The results are for i# gauze having a compressive residual stress of 9f/WrM2 at 1', the abnormal rupture rate is 5% and 0, respectively, and the ductility is close to n. This material was also given compressive residual stress by roller rolling.

Since steel wire compositions, differences in hardness between the center and surface, or residual stress of steel wires 23 to 29 are outside the scope of the present invention, all of them have high abnormal rupture rates and poor ductility.

Items 30 to 45 relate to invention 3, of which item 430.
31, 32, 34, 36, and 38.39 are examples of the present invention, and the others are comparative examples.

First, the flat plate 30 has a wire diameter of 2. Ofi, tensile strength 195 to 9f
/m”, hardness difference between center and surface 25 te 30 kgf/m
The result is a steel wire with a compressive residual stress of "A 3114 wire diameter of 0.8 mm, a tensile strength of 260 to 9 f/m", a pot gauze with a hardness difference of 55 and a compressive residual stress of 69 to 9 f/τ2, The abnormal rupture rate of A-5f'LQ and 5% dezn is also close to the ductility.

Ya 32 has a wire diameter of 0.06 m, a tensile strength of 408, and 9 f/1 p.
p2, a hardness difference of 43, and a residual stress of 102 to 9f/■2, which shows an abnormal rupture rate of 5% and good ductility. A 30, 31.

The residual stress in the steel wire of 32 was added by shot peening.

Mu33 has a wire diameter of 5.5cm and a tensile strength of 186ki? f/m+
The results for the steel wire shown in ``The difference in hardness between the center and the surface is as much as 110, and the compressive residual stress is small at 10 yf/m, so the abnormal rupture rate is 50 yf/m, which indicates that the ductility is poor. .

Flats 34 and 35 have a wire diameter of 3.2 fins and a tensile strength of 145 to 9 f.
/w'' steel wire, the hardness difference between the center and the surface is 26, and the A34 has a compressive residual stress of 9f/- at 46.
The m-wire has an abnormal breakage rate of 0 and excellent ductility, but the abnormal breakage rate of the flat 35 steel wire, which has a hardness difference of 107 and a tensile residual stress of 40 kgf/m'', is 40 inches and has poor ductility.

Residual stress was applied by shot peening.

A36 and 37 have a wire diameter of 0.04 cm and a tensile strength of 421 to 9
The results for steel wires with the same composition of f/sa="
The abnormal rupture rate of a flat 36 steel wire with a compressive residual stress of 68 kgf/m" with a hardness difference of 18 between the center and the surface is 5 cm, whereas it is 35 kg with a hardness difference of 109 between the center and the surface.
It can be seen that the abnormal breakage rate of the flat copper wire 37 having a tensile residual stress of f/w2 is 80%, indicating that the m-wire according to the present invention has excellent ductility. It is also clear that the composite reinforced plastic plate according to the invention exhibits excellent fatigue properties. Note that the compressive residual stress was given by roller rolling.

A38 has a wire diameter of 3.2", tensile strength of 172 and 9f/2,
GLI wire with a hardness difference of 35 and a compressive residual stress of 59 #f/wm", and A39 has a wire diameter of 0.3 cm and a tensile strength of 2
In the example of a silver wire with a compressive residual stress of 9 f/2 for 38 and 9 f/2 for 82 with a hardness difference of 40, the abnormal rupture rate is f.
Both lQ and 5chi exhibit very high ductility. In addition,
The compressive residual stress of the steel wire of 438.39 was applied by shot peening.

On the other hand, steel wires 40 to 45 have a composition of the steel wire, a difference in hardness between the center and the surface, or a residual stress that is outside the scope of the present invention, so all of them have a high abnormal rupture rate and lack ductility.

Finally, flats 46 to 58 relate to invention 4, and the butchers 46, 47, 48, 49, and 51 are examples of the invention, and the others are comparative examples.

A46 has a wire diameter of 2. Ovm, tensile strength 193klJ
f/m2, hardness difference between center and surface is 20, compression residual stress cuff
5 kgf%o+n2 steel wire, Ya 47 has a wire diameter of 3.
5 m, tensile strength 186 kgf/m", hardness difference 34
t1 with a compressive residual stress of 60 kllf/r”
3 wire, Mu48 has a wire diameter of 1.3 and a tensile strength of 220 kgf.
/wa”, hardness difference 50, compressive residual stress 68 kgf/
In the results for the steel wire with wa'', the abnormal rupture rate was 0 in all cases.
It is extremely ductile.

Note that compressive residual stress was applied to the steel wires A 46 , 47 , and 48 by roller rolling.

&49 and 50id, wire diameter 045fi, tensile strength 285k
i? The results are for steel wires with the same composition of f/m'', which have a compressive residual stress of 91 kgf/TEA2 with a hardness difference of 2ρ between the center and the surface.

&49 steel wire has an abnormal rupture rate of 0 and has excellent ductility. -The difference in hardness between the male center and the surface is 108 and 42 ky f
A50 steel with a tensile residual stress of 90%
It is clear that the ductility is poor, with an abnormal rupture rate of up to 100%. This steel wire also has excellent corrosion fatigue properties. Note that the compressive residual stress of 1 line &49 was given by shot peening.

&51-53 have a wire diameter of 2.0m and a tensile strength of 235kl?
The results are for a steel wire with the same composition of f/m2, and the hardness difference between the center and surface is 75, and the A51 steel lfN, which has a compressive residual stress of 70 Kf/wa2, has an abnormal rupture rate of 5 cm and quickly becomes ductile. There is. On the other hand, the hardness difference is 123 and 37 kI? f
An A52 steel wire with a tensile residual stress of 25 mm/m'' has an abnormal breakage rate of 75 mm and lacks ductility. 53
The copper wire also has a high abnormal breakage rate and lacks ductility.

The A51 steel wire of the present invention also has excellent stress corrosion cracking properties,
Loafs made from this steel wire also exhibit good fatigue properties. Compressive residual stress is imparted by roller rolling.

The structures 54 to 58 each have a composition or residual stress outside the scope of the present invention, and thus have a high abnormal rupture rate and poor ductility.

(Effects of the Invention) As is clear from the above examples, the iron wire of the present invention has high strength and excellent ductility, and is extremely useful in industry.

[Brief explanation of drawings]

Figures 1 (a) and (b) show the fracture morphology of the torsional test material.
(a) is a diagram showing a normal fracture, (b) is a diagram showing an abnormal fracture, and Figure 2 is a diagram showing a crack that occurs on the surface of a steel wire during a twisting test. 1...Steel wire, 2...Crack, 3 ...Gripping jig. Figure 1

Claims (4)

[Claims] (1) Contains C0.4-1.0%, Si2.0% or less, Mn0.2-2%, P0.02% or less, SO
．． 02% or less, N0.01% or less, the remainder consists of iron and unavoidable impurities, and the hardness difference between the center and the surface is 100 or less in terms of Vickers hardness, and according to the steel wire strength σ (0.05σ + 13 ) ~ (0.35σ+28)k
A high tensile strength steel wire with excellent ductility, characterized by having a surface compressive residual stress of gf/mm^2. (2) Contains C0.4-1.0%, Si2.0% or less, Mn0.2-2%, P0.02% or less, SO
．． 0.02% or less, N0.01% or less, and Cr0.
．． 05~3%, Mo0.01~1%, W0.01~1%
, Cu0.05-3%, Ni0.1-5%, Co0.1
-5% of one or more kinds, the balance is iron and unavoidable impurities, and the difference in hardness between the center and the surface is 100 or less in terms of Vickers hardness, and according to the steel wire strength σ (0. 05σ+13)～(0.35σ+28)kgf/
A high tensile strength steel wire with excellent ductility, characterized by having a surface compressive residual stress of mm^2. (3) Contains C0.4-1.0%, Si2.0% or less, Mn0.2-2%, P0.02% or less, SO
．． 0.02% or less, N0.01% or less, and Al0
．． 001~0.1%, Ti0.001~0.1%, Nb
0.001-0.1%, V0.001-0.1%, B0
．． 0003 to 0.05%, Mg 0.001 to 0.1%, the remainder consists of iron and unavoidable impurities, and the difference in hardness between the center and the surface is 100 or less in terms of Vickers hardness. , depending on the steel wire strength σ (0.0
5σ+13) ~ (0.35σ+28) kgf/mm^2
A high tensile strength steel wire with excellent ductility, characterized by having a surface compressive residual stress of . (4) Contains C0.4-1.0%, Si2.0% or less, Mn0.2-2%, P0.02% or less, SO
．． 0.02% or less, N0.01% or less, and Cr0.
．． 05~3%, Mo0.01~1%, W0.01~1%
, Cu0.05-3%, Ni0.1-5%, Co0.1
Contains ~5% of one or more types, and further contains Al0.0
01-0.1%, Ti0.001-0.1%, Nb0.
001~0.1%, V0.001~0.1%, B0.0
003 to 0.05%, Mg 0.001 to 0.1%, the remainder consists of iron and unavoidable impurities, and the difference in hardness between the center and the surface is 100 or less in terms of Vickers hardness. Depending on the steel wire strength σ (0.05σ+
13) A high tensile strength steel wire with excellent ductility, characterized by having a surface compressive residual stress of ~(0.35σ+28) kgf/mm^2.