CN106661687A

CN106661687A - Wire material for steel wire, and steel wire

Info

Publication number: CN106661687A
Application number: CN201580034203.5A
Authority: CN
Inventors: 石田友信; 增田智; 增田智一
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2014-07-01
Filing date: 2015-06-02
Publication date: 2017-05-10
Also published as: EP3165625A4; CA2951799A1; EP3165625A1; KR20170013340A; EP3378964A1; MX2016017005A; JP2016014168A; US20170198375A1; CN109576448A; WO2016002413A1

Abstract

Provided is a wire material for steel wire, the wire material having excellent low cyclic fatigue characteristics and being useful as a raw material for high-strength steel wire for wire rope, PC steel wire, or the like. Also provided is a steel wire that can exhibit said characteristics. A wire material for steel wire according to the present invention contains, by mass%, 0.70%-1.3% of C, 0.1%-1.5% of Si, 0.1%-1.5% of Mn, 0.001%-0.006% of N, 0.001%-0.10% of Al, 0.02%-0.20% of Ti, 0.0005%-0.010% of B, 0%-0.030% of P, and 0%-0.030% of S, the remainder being iron and unavoidable impurities, the main phase being pearlite, the area ratio of proeutectoid ferrite being 1.0% or less, and the average thickness of the proeutectoid ferrite being 5 [mu]m or less.

Description

Steel wire wire rod and steel wire

Technical field

The present invention relates to be used for the former material of the steel wire as high intensity of steel wire rope and PC steel wires etc. steel wire wire rod and Such steel wire.

Background technology

Hoisting line in Riata for elevator and crane etc. is this to be applied in the steel strand wires of alternating bending stress, rope strand Flexural fatigue becomes the design strength and the key factor in life-span for determining rope.In recent years, along with the high speed of elevator With the miniaturization of crane, the lightweight demand of rope increases, it is desirable to realize excellent high-strength of Flexural fatigue of this point The steel wire wire rod of degree.The excellent high-tensile steel wires wire rod of other Flexural fatigue, as PC (Prestressed Concrete) former material of steel wire is also useful.In such steel wire wire rod, specifically, it is desirable to which number of repetition will not occur For 10⁴～10⁵The secondary low-cycle fatigue for just occurring.

As the technology of the characteristic for being used to improve wire rod, up to now it is also proposed that having a variety of.For example, it is public in patent document 1 Be provided with a kind of technology, its by making steel in fine precipitation BN systems field trash improving fatigue strength.

There is a kind of technology disclosed in patent document 2, it is processed by carrying out the direct patenting of fuse salt after hot rolling, So as to be the pearlitic structrure that the area occupation ratio of pro-eutectoid ferrite is less than 3% by the organizational controls of wire rod, high intensity line is obtained Material.

Have a kind of technology disclosed in patent document 3 in addition, its be make wire rod metal structure be more than 95% pearly-lustre Body is organized, and the maximum of the pearlite block particle diameter of the pearlite of the central part in the axially vertical section with wire rod is peaceful Mean control regulation scope, so as to obtain the wire rod of high ductibility.It is also disclosed in the technology in addition, makes wire-drawing workability On the basis of good, the volume fraction of pro-eutectoid ferrite is adjusted to less than 2% useful.

Prior art literature

Patent document

Patent document 1：Japanese Unexamined Patent Publication 2011-225990 publications

Patent document 2：Japanese Unexamined Patent Publication 2007-39800 publications

Patent document 3：International Publication No. 2007/139234

Become the characteristic of problem in the technology of above-mentioned patent document 1, be that number of repetition is 10⁷Secondary close fatigue limit And the high cycle fatigue for occurring, it is different from the mechanism of above-mentioned low-cycle fatigue.So it is exposed for a long time in extraneous air in steel wire rope In product, due to the impact of the friction between the oxidation of skin section, the intrusion of hydrogen and rope strand etc., skin section is caused to be susceptible to tortoise Split, material is possible to break under the life-span more much lower than original fatigue limit, it is therefore desirable to take suppression be cracked into The countermeasure of exhibition.

In addition, in the technology of above-mentioned patent document 2, in order to obtain high-strength wire material, needs after hot rolling can be direct Carry out the special equipment of patenting process, equipment investment increase.In addition such equipment, compares while making wire rod in conveyer Upper conveyance is while so-called stelmor (Stelmor) cooling device of cooling, has in productivity ratio and the such shortcoming of maintainability difference. And, only reduce the area occupation ratio of the pro-eutectoid ferrite in wire rod, it is impossible to play the raising effect of sufficient low cycle fatigue property Really.

In addition, simply specifying the important document described in above-mentioned patent document 3, cannot sufficiently imitate for low cycle fatigue property Really.

The content of the invention

The present invention in view of above-mentioned such situation and formed, its object is to, there is provided a kind of low cycle fatigue property is excellent, make For the useful steel wire wire rod of the former material of the high-tensile steel wires of steel wire rope and PC steel wires etc., and the steel that such characteristic can be played Silk.

The steel wire wire rod of the invention of above-mentioned problem is can solve the problem that, what is had will be intended to following main points：With quality % Meter, contains respectively C：0.70～1.3%, Si：0.1～1.5%, Mn：0.1～1.5%, N：0.001～0.006%, Al： 0.001～0.10%, Ti：0.02～0.20%, B：0.0005～0.010%, P：More than 0% and below 0.030%, S： More than 0% and below 0.030%, surplus is iron and inevitable impurity, with pearlite as principal phase, pro-eutectoid ferrite Area occupation ratio is less than 1.0%, and the average thickness of pro-eutectoid ferrite is less than 5 μm.

Further, so-called " with pearlite as principal phase ", more than the 95 area % for meaning metal structure are pearlitic structrures.Separately Outward, the average thickness of so-called pro-eutectoid ferrite, when meaning with observation by light microscope pro-eutectoid ferrite, proeutectoid ferrite The mean value of the thickness of the width of body.

The steel wire wire rod of the present invention, it is also preferred that in terms of quality %, also containing such as inferior：

(a)Cr：Higher than 0% and below 1.0% and V：At least one in higher than 0% and below 0.5%；

(b)Ni：Higher than 0% and below 0.5% and Nb：At least one in higher than 0% and below 0.5%；

(c)Co：Higher than 0% and below 1.0%；

(d)Mo：Higher than 0% and below 0.5% and Cu：At least one in higher than 0% and below 0.5%.

In the steel wire wire rod of the present invention, the content of solid solution B is preferably more than 0.0003%.

The present invention also includes be made up of the chemical composition of above-mentioned steel and constitutes, 100,000 fatigue strength σ and tensile strength TS (Tensile Strength) meets the steel wire of the relation of following (1) formulas.

σ ＞ 0.45TS ... (1)

According to the present invention, by the area occupation ratio of the pro-eutectoid ferrite of the steel wire rod before reduction Wire Drawing, and reduce Its thickness, the bending fatigue strength that can make the steel wire after cold working (Wire Drawing) is improved, and plays excellent fatigue properties. Especially for 10⁴～10⁵The low-cycle fatigue occurred under secondary or so alternate stress load, plays excellent characteristic.

Description of the drawings

Fig. 1 is the outline figure of the status of implementation for representing 4 repeated bend tests.

Fig. 2 is the alternative microphotograph of accompanying drawing of the example for representing the pro-eutectoid ferrite grain observed.

Specific embodiment

The present inventors, in the steel wire rod as metal structure using pearlite as principal phase, for left and right low-cycle fatigue The factor of performance has carried out adjusting Check with keen determination.Its result is verified, in pearlitic structrure it is slight separate out pro-eutectoid ferrite (with Under, sketch as " pro-eutectoid α ") promote fatigue cracking progress.In carbon content is more than 0.70% such high-carbon steel, as after Shown in the Fig. 2 for stating, pro-eutectoid α is found in the plate-like precipitation of old austenite grain boundary, but reach in the area occupation ratio for making pro-eutectoid α On the basis of less than 1.0%, by reducing its thickness, then excellent low cycle fatigue property can be played, so as to complete this It is bright.

In principal phase in the steel wire rod of pearlitic structrure, pro-eutectoid α occurs cavity with the interface of pearlite, promote tired tortoise The progress split.It is therefore important that reducing the area occupation ratio of pro-eutectoid α as far as possible, the amount for making interface is reduced.In addition, by reducing The area occupation ratio of pro-eutectoid α, it is also possible to obtain suppressing the effect of longitudinal crack when twisting is tested.If longitudinal crack occurs, cannot undergo Twisted wire process, therefore occur longitudinal crack steel wire be judged as it is bad.If considering these effects, the face for making pro-eutectoid α is needed Product rate, in less than 1.0% based on the ratio relative to metal structure entirety.The area occupation ratio of pro-eutectoid α be preferably 0.8% with Under, more preferably less than 0.6%.

In order to reduce the area occupation ratio of pro-eutectoid α, B is effective for addition.The area occupation ratio reducing effect of pro-eutectoid α is played, is that B makees For the situation that solid solution B is present, as some lost effect that compound as BN is separated out.Therefore, in the steel wire of the present invention In material, need N amounts, B amount controls in appropriate scope, it is additionally preferred to the manufacturing condition manufacture that BN is difficult to separate out.

On the other hand, if the thickness of pro-eutectoid α becomes big, because stress is concentrated to the cavity that interface occurs cavity is caused Expand, encourage the progress of fatigue cracking and reduce fatigue strength.The little pro-eutectoid α Jing Wire Drawings of thickness and deform, have no Evilization, even if but the big pro-eutectoid α of thickness is still remaining after Wire Drawing, and make bending fatigue strength (hereinafter simply referred to as " tired Intensity ") reduce.In particular it is necessary to the average thickness for making pro-eutectoid α is in less than 5 μm.The average thickness of pro-eutectoid α is preferred For less than 4 μm, more preferably less than 3 μm.

In order to reduce the average thickness of pro-eutectoid α, the Ti systems field trash fine dispersion headed by TiC is effectively made in steel In, in crystal boundary neighborhood, the precipitation core for making pro-eutectoid α is generated in a large number particularly fine dispersion, and suppresses its nucleus growth effective.For This, needs the Ti amount controls in steel wire rod in appropriate scope, it is then preferred that with the easily fine precipitation of the Ti such as TiC systems field trash Manufacturing condition manufactured.

The steel wire rod of the present invention, from the characteristic suitable for making its basic when steel wire etc. on the basis of is played, and is also needed Rightly to adjust its chemical composition composition.Also including the amount including above-mentioned B, N, Ti, its chemical composition composition is as follows.Also Have, " % " in chemical composition composition is " quality % ".

(C：0.70～1.3%)

C is effective element for the rising of intensity, the increase of adjoint C amounts, the wire rod (steel wire rod) before cold working, and cold The intensity of the steel wire after processing is improved.In addition amount of precipitation of the C amounts for pro-eutectoid α also results in impact, if C amounts are few, can not fill Divide the precipitation for suppressing pro-eutectoid α.Therefore, C amounts are set to more than 0.70%.C amounts are preferably more than 0.74%, more preferably 0.78% More than.But, if C amounts are too remained, proeutectoid cementite (below, sketching as " pro-eutectoid θ ") is separated out, and is drawn in Wire Drawing Play broken string.Therefore, C amounts are set to less than 1.3%.C amounts are preferably less than 1.2%, more preferably less than 1.1%.

(Si：0.1～1.5%)

Si has the effect as deoxidier, also plays the role of to improve the intensity of wire rod in addition.In order to effectively play These effects, by Si amounts more than 0.1% is set to.Si amounts are preferably more than 0.15%, more preferably more than 0.20%.The opposing party Face, if Si amounts are too remained, deteriorates cold-drawn wire, causes the increase of outage.Therefore, Si amounts are set to into less than 1.5%.Si Amount は is preferably less than 1.4%, more preferably less than 1.3%.

(Mn：0.1～1.5%)

Mn and Si equally also has deoxidation, but particularly with the S in steel is fixed as MnS, so as to improve steel Toughness and ductility effect.In order to effectively play these effects, Mn amounts are more than 0.1%.Mn amounts are preferably 0.15% More than, more preferably more than 0.20%.But, Mn is the element of easy segregation, if add superfluously, the quenching in Mn segregations portion Property excessively increases, it is possible to which the over-cooling structure for making martensite etc. is generated.Therefore, Mn amounts are set to less than 1.5%.Mn amounts are preferably Less than 1.4%, more preferably less than 1.3%.

(N：0.001～0.006%)

N is combined chemically to form BN with the B in steel, loses the effect that B is brought.In addition, the N of solid solution condition draws in wire drawing The reduction of the twisting property that cause strain-aging is caused, can cause longitudinal crack when notable.In order to prevent these drawbacks, N amounts from being Less than 0.006%.N amounts are preferably less than 0.005%, more preferably less than 0.004%.On the other hand, if on a small quantity, then The nitride of TiN and AlN etc. makes crystal grain miniaturization, the effect with the ductility for improving wire rod.In order to play such effect, N amounts are more than 0.001%.N amounts are preferably more than 0.0015%, more preferably more than 0.0020%.

(Al：0.001～0.10%)

Al is effective deoxidant element.In addition, also having to form nitride as AlN and make the effect of crystal grain miniaturization. In order to effectively play such effect, Al amounts are more than 0.001%.Al amounts are preferably more than 0.002%, more preferably More than 0.003%.On the other hand, if adding Al superfluously, Al is formed₂O₃Such oxide, increases broken string during wire drawing Plus.From this viewpoint, Al amounts are less than 0.10%.Al amounts are preferably less than 0.09%, more preferably less than 0.08%.

(Ti：0.02～0.20%)

Ti forms carbide as TiC, the effect with the particle diameter (thickness) for reducing pro-eutectoid α.In addition, also have Effect is to be combined chemically to form nitride as TiN with the N in steel, prevents the reduction of twisting property caused because of N.In order to have Effect ground plays these effects, and Ti amounts are more than 0.02%.Ti amounts are preferably more than 0.03%, more preferably more than 0.04%.Separately On the one hand, if Ti amounts become superfluous, the Ti systems field trash of TiC and TiN etc. is separated out in a large number, increases broken string during wire drawing.Cause This, Ti amounts are less than 0.20%.Ti amounts are preferably less than 0.15%, more preferably less than 0.10%.

(B：0.0005～0.010%, be more than 0.0003% preferably as solid solution B)

B has the generation for hindering pro-eutectoid α, reduces the effect of its area occupation ratio.But, if forming chemical combination as BN Thing, then cannot play such effect.In order to effectively play the effect of B, B amounts are needed for more than 0.0005%.Preferred B amounts Lower limit be more than 0.0007%, more preferably more than 0.001%.On the other hand, if B amounts become superfluous, as with Fe's The Fe-B based compounds of compound are separated out, such as FeB₂Separate out, cause crackle during hot rolling, therefore B amount needs to be in Less than 0.010%.B amounts are preferably less than 0.008%, more preferably less than 0.006%.Additionally, it is preferred that making steel as solid solution B In contain more than 0.0003%, more preferably more than 0.0005%.

(P：More than 0% and below 0.030%)

P makes embrittlement of grain boundaries in old austenite grain boundary segregation, reduces fatigue strength, therefore its content is more few more excellent Choosing.Therefore, P amounts are less than 0.030%.P amounts are preferably less than 0.025%, more preferably less than 0.020%.P is measured 0%, but usually contain more than 0.001%.

(S：More than 0% and below 0.030%)

S and P is same, and in old austenite grain boundary segregation embrittlement of grain boundaries is made, and reduces fatigue strength, therefore its content is fewer It is more preferred.Therefore, S amounts are less than 0.030%.S amounts are preferably less than 0.025%, more preferably less than 0.020%.S amounts also may be used Think 0%, but usually contain more than 0.001%.

As described above, surplus is substantially iron to the basis of the wire rod of the present invention.But, allow certainly because raw material, goods and materials, The situation of manufacturing equipment etc. and the inevitable impurity that is mixed into are included in steel.

In addition in the wire rod of the present invention, in order that the characteristic of intensity, toughness, ductility etc. is further improved, therefore basis Need, preferably also contain following element：

(c)Co：Higher than 0% and below 1.0%；

Cr：Higher than 0% and below 1.0% and V：At least one in higher than 0% and below 0.5%)

Cr and V is useful element in the intensity (tensile strength) for improving wire rod, it is also possible to be allowed to containing one kind or two Plant and be used in combination.

Particularly Cr has the sheet gap miniaturization for making pearlite, improves the intensity of wire rod and the effect of toughness.In order to Such effect is effectively played, Cr amounts are preferably more than 0.05%.Cr amounts more preferably more than 0.10%, more preferably More than 0.15%.On the other hand, if Cr amounts are too remained, hardenability is improved, the dangerous raising that over-cooling structure occurs in hot rolling, Therefore Cr amounts are preferably less than 1.0%.Cr amounts more preferably less than 0.8%, more preferably less than 0.6%.

V-arrangement into carbonitride, with the effect for improving the intensity of wire rod.In addition, it is same with Nb, after separating out with AlN Remaining solid solution N form nitride, contribute to crystal grain miniaturization, in addition, also suppress timeliness crisp with fixed solid solution N The effect of change.In order to effectively play such effect, V amounts are preferably more than 0.01%, more preferably more than 0.02%, enter one Step is preferably more than 0.03%.But, V is the element of high price, even if add superfluously, its effect is also saturation, economically Cause to waste, therefore V amounts are preferably less than 0.5%, more preferably less than 0.4%, more preferably less than 0.2%.

(Ni：Higher than 0% and below 0.5% and Nb：At least one in higher than 0% and below 0.5%)

Ni and Nb is useful element in the toughness for improving steel wire, it is also possible to be allowed to be used in combination containing one or two.

Particularly Ni is the element of the toughness for improving the steel wire after wire drawing.In order to effectively play such effect, Ni amounts Preferably more than 0.05%, more preferably more than 0.1%, more preferably more than 0.2%.But, even if the superfluous additions of Ni, Its effect is also saturation, economically causes to waste.Therefore, Ni amounts are preferably less than 0.5%, more preferably less than 0.4%, enter One step is preferably less than 0.3%.

Nb and Ti and Al is similarly formed nitride, makes crystal grain miniaturization and contributes to the toughness raising of steel wire, in addition, Also fix solid solution N and suppress the effect of initial aging stage.In order to effectively play such effect, Nb amounts be preferably 0.01% with On, more preferably more than 0.03%, more preferably more than 0.05%.But, Nb is the element of high price, even if add superfluously Plus, its effect is also saturation, economically causes to waste, therefore Nb amounts are preferably less than 0.5%, more preferably less than 0.4%, More preferably less than 0.3%.

(Co：Higher than 0% and below 1.0%)

Co particularly reduces the generation of proeutectoid cementite when C amounts are high, and with tissue is made uniform pearlite group is become Knit such effect.In order to effectively play this effect, Co amounts are preferably more than 0.05%, more preferably more than 0.1%, enter One step is preferably more than 0.2%.But, even if Co adds superfluously, its effect is also saturation, economically causes to waste.Cause This, Co amounts are preferably less than 1.0%, more preferably less than 0.8%, more preferably less than 0.6%.

(Mo：Higher than 0% and below 0.5% and Cu：At least one higher than 0% and below 0.5%)

Mo is the element for improving the corrosion resistance of steel wire.In order to effectively play such effect, Mo amounts are preferably More than 0.05%, more preferably more than 0.1%, more preferably more than 0.2%.But, if Mo amounts are superfluous, hold during hot rolling Easily there is over-cooling structure, in addition deteriorate also ductility.Therefore Mo amounts are preferably less than 0.5%, more preferably less than 0.4%, More preferably less than 0.3%.

Cu and Mo is equally the element for improving the corrosion resistance of steel wire.In order to effectively play such effect, Cu amounts Preferably more than 0.05%, more preferably more than 0.08%, more preferably more than 0.10%.But, if Cu amounts are superfluous, React with S and make CuS segregations in crystal boundary portion, flaw occurs in wire rod manufacture process.In order to avoid such impact, Cu amounts are preferred For less than 0.5%, more preferably less than 0.4%, more preferably less than 0.3%.

Mo and Cu can also be allowed to be used in combination containing one or two.

Next, for the method for the steel wire wire rod that can manufacture the present invention is illustrated.

Wire rod before cold-drawn wire, typically by for the steel for appropriately controlling chemical composition melting, split rolling method are carried out And hot rolling, manufacture further according to needing to carry out patenting process.One side meet important document given to this invention (metal structure, Pro-eutectoid α area occupation ratios, the average thickness of pro-eutectoid α) while when manufacturing the wire rod of the present invention, it is important that containing Ti, B and N After amount is appropriately controlled in above-mentioned scope, then the precipitation movement of suitable control TiC and BN.

First, in split rolling method, preferably slab is heated to into more than 1200 DEG C, what is separated out during decomposition casting is thick TiC.If heating-up temperature is lower than 1200 DEG C, the thick TiC of remaining in wire rod, it is impossible to fully reduce the thickness of pro-eutectoid α, therefore Fatigue strength is reduced.The heating-up temperature is more preferably more than 1250 DEG C, more preferably more than 1300 DEG C.But, if heating Temperature is too high, then the melting of wire rod occurs, therefore is normally set to 1400 DEG C or so.

When then carrying out hot rolling, preferably by being heated to more than 1000 DEG C of temperature range, fully decompose thick in steel billet After big BN, Jing rolling after water-cooled carry out it is sufficiently cool, by the mounting temperature control on the Laying head of rolled stock (wire rod) At 800～1000 DEG C.If mounting temperature is higher than 1000 DEG C, in the cooling on conveyer after mounting, separate out in wire rod big The BN of amount, it is possible to solid solution B can not be substantially ensured that.Mounting temperature is more preferably less than 980 DEG C, more preferably less than 950 DEG C.Separately Outward, if mounting temperature is less than 800 DEG C, the deformation drag of wire rod increases, for example, it is possible to occur to wind etc. on Laying head Mounting it is bad.Therefore mounting temperature is preferably more than 800 DEG C.Mounting temperature is more preferably more than 820 DEG C, more preferably More than 850 DEG C.

In addition when hot rolling is implemented, the rate of straining for preferably making final 4 passages of rolling is 0.5 second^-1More than, by dynamic The recrystallization of state makes crystal grain miniaturization, and separates out fine TiC.If above-mentioned rate of straining was than 0.5 second^-1It is little, then can not make TiC fully miniaturizations, it is impossible to fully reduce the average thickness of pro-eutectoid α.At this moment rate of straining is more preferably 0.8 second^-1With On, more preferably 1.0 seconds^-1More than.But, consider that above-mentioned rate of straining is preferably generally 5 from the problem of machine utilization Second^-1Below.Further, rate of straining V ε, before first roller reached the standard grade from final passage as the roller in front of 4 passages Basal area S₀(m²), and basal area S after final passage₄(m²), and pass through time (rolling time) t adding up to for 4 passages (second), represented by following (2) formulas.

V ε={ ln (S0/S4) }/t ... (2)

After mounting, wire rod is cooled down on coolconveyer, occur pearlitic transformation in cooling, but preferably to pearly-lustre body phase Become the average cooling rate for starting carries out chilling into more than 5 DEG C/sec.If average cooling rate at this moment is slow, pro-eutectoid α holds Easily separate out and coarsening at high temperature, it is possible to be not sufficiently reduced the thickness of pro-eutectoid α.If in addition, average cooling rate compares 5 DEG C/sec little, then locally have and be referred to as coarse pearlite (コーズパーライト) the extremely thick tissue analysis of sheet gap Go out, stringiness can also reduced.Further, in the beginning of pearlitic transformation, the temperature of wire rod is measured, is tried to achieve according to phase transformation heat release cold But the point (flex point) of curvilinear motion.The average cooling rate is more preferably more than 10 DEG C/sec, more preferably 15 DEG C/ More than second.The preferred upper limit of average cooling rate is less than 100 DEG C/sec, more preferably less than 50 DEG C/sec.

The wire rod for obtaining as described so, directly Jing Wire Drawings (cold working) can use as steel wire, but it is also possible to Implement patenting before Wire Drawing to process.Patenting before by implementing such Wire Drawing is processed, it is possible to increase wire rod Intensity, and reduce strength variance.

In addition, as manufacture minor diameter steel wire when be contemplated to Wire Drawing degree it is big when, carried out necessarily by rolled stock Implement patenting after degree wire drawing to process, wire rod tissue is revert to after unprocessed pearlitic structrure, then carry out wire drawing and add Work is also useful.At this moment, processed by implementing patenting, pro-eutectoid α resulting during hot rolling disappears, if can ensure that fine precipitation TiC and q.s solid solution B, then borrowing general patenting treatment conditions can just obtain the area of appropriate pro-eutectoid α Rate and average thickness.

Implement the heating-up temperature (below, by the temperature be referred to as " relation reheating temperature ") when patenting is processed be preferably 900～ 1000 DEG C or so, more preferably more than 920 DEG C and less than 980 DEG C.From non-solid solution carbides remaining is prevented, the complete Ovshinsky of tissue is made From the viewpoint of body, relation reheating temperature is preferably more than 900 DEG C, if but excessively high temperature, TiC is thick, or solid solution B and N anti- Answer and reduce, it is impossible to obtain area occupation ratio, the average thickness of the pro-eutectoid α of regulation.In addition, the keeping temperature that patenting is processed is preferred For 530～600 DEG C or so, more preferably more than 550 DEG C and less than 580 DEG C.

The wire rod of the present invention, because encourage the generation of fatigue cracking, the amount of the pro-eutectoid α of progress be decreased sufficiently, and its THICKNESS CONTROL obtains little, so having carried out cold worked steel wire to it, and has completely or partially used the steel wire rope and PC of the steel wire The product of steel wire etc., than the excellent in fatigue characteristics of common product.In general, tensile strength and fatigue strength pass in direct ratio System, but by the steel wire of the wire rod manufacture of the present invention characterized in that, under 100,000 fatigue strength σ, with tensile strength TS satisfaction The relation of (1) formula is stated, the present invention also includes such steel wire.In addition, the present invention also includes completely or partially using such steel The product of the steel wire rope of silk manufacture etc..

σ ＞ 0.45TS ... (1)

The application is based on Japan's patent application 2014-136222 main line priority filed in 1 day July in 2014 Interests.The full content of the specification that Japan's patent application the 2014-136222nd is helped in this application to refer to Draw.

Embodiment

Hereinafter, enumerate embodiment and further illustrate the present invention.The present invention is not limited by the examples below, and can accord with Close and can certainly suitably be changed enforcement in the range of objective aforementioned, described later, these are all contained in the technology of the present invention In the range of.

For the steel ingot of the chemical composition composition shown in table 1 below, cogging is carried out with the condition shown in table 2 below, Jing is warm Roll and be processed into wire rod coiled material, a part carries out patenting process with the condition shown in Table 3 below again.Rolling shown in table 2 below Line footpath and the lead shown in Table 3 below are quenched the different coiled material of line footpath, represent that folder is heat-treated every middle wire drawing.

[table 1]

[table 2]

[table 3]

Using the sample extracted on the wire rod from before finish draw silk, according to following methods, implement tension test, metal structure The evaluation of (area occupation ratio of pro-eutectoid α, pearlite area occupation ratio, the average thickness of pro-eutectoid α), the measurement of solid solution B amounts.

(tension test)

Tensile strength TS (Tensile Strength) of the sample of extraction, is surveyed according to JIS Z 2241 (2011) Amount.As a result it is displayed in table 4 below.

(evaluation of the area occupation ratio of pro-eutectoid α)

The area occupation ratio of pro-eutectoid α, by the way that the sample of extraction is embedded among resin etc. mirror ultrafinish is carried out, and corrosive liquid makes With trinitrophenol and the mixed liquor of ethanol, observed with light microscope, its area occupation ratio is measured by graphical analysis.Upper State that corrosive liquid effect is lower and the part for floating of turning white is pro-eutectoid α.If during a diameter of D of wire rod, the D/4 portions in cross section are considered as Tissue is represented, is shot again with multiplying power 400, added up to and evaluate 5 visuals field." area occupation ratio of pro-eutectoid α " table shown in table 4 below Show its mean value.Further, institute cross section is referred to relative to the vertical face of wire rod longitudinally.

In addition, also measuring the area occupation ratio of pearlite by the method.Further, table 4 below metal structure project In, it is shown as " P ", expression pearlitic structrure is more than 95 area %, i.e. pearlite is principal phase.In addition, being shown as " P+ α " " P+ θ's ", represent that pearlitic structrure is less than 95 area %, in addition to pearlitic structrure, it is also represented by ferrite (α) and carburizing The tissue of body (θ) mixing.

(evaluation of the average thickness of pro-eutectoid α)

For the test portion of mirror ultrafinish has been carried out as described above, with SEM (Scanning Erectron Microscope structure observation) is carried out, the thickness of the 10 pro-eutectoid α crystal grain observed is measured, its mean value is sought, is calculated per 1 Individual thickness.Measurement is carried out as described above in the D/4 portions in cross section.As a result it is displayed in table 4 below.

(measurement of solid solution B amounts)

Solid solution B amounts are evaluated with electrolytic extraction residue measurement.Carry out having used the electrolysis of 10% acetylacetone,2,4-pentanedione solution to extract Residue measurement is taken, using mesh：0.1 μm of screen cloth, with bromo-ester (Block ロ system エステ Le) method the compound type B in residue is measured Amount.Compound type B amounts are deducted in total B amounts from steel, so as to try to achieve solid solution B amounts.As a result it is displayed in table 4 below.Further, use In bromo-ester method test portion be 3g.In addition if solid solution B amounts would not change without undergoing more than 900 DEG C of thermal process, therefore Tune Check can also be carried out to the steel wire after cold working.

Then, Wire Drawing is carried out to resulting wire rod coiled material and makes steel wire (steel wire), implement tension test, twisting The evaluation of characteristic, the evaluation of fatigue properties.In table 5 below, contraction percentage of area during Wire Drawing is shown, and by Wire Drawing The line footpath of the steel wire for obtaining.

(tension test)

Tensile strength TS and yield point YP (Yield Point) of steel wire is measured according to JIS Z 2241 (2011).As a result In being displayed in table 5 below.In addition, tensile strength TS is multiplied by 0.45 value being displayed in table 5 below.

(evaluation of twisting property)

With regard to twisting property, based on twisting test is carried out, the twisting value (fracture twist number) to required for rupturing is commented Valency.Twisting value in table 5 below is the mean value of N=5 roots.At this moment, reverse speed is 52 beats/min, and tension force is 500gf (4.9N).Further, twisting value is that distance between chuck (test line length) is converted into into 100 times (100d) of line footpath d and standard is allowed to Change.In addition, observing by section, normal section and longitudinal crack are differentiated, even if there is 1 longitudinal crack occurs in 5, in aftermentioned table It is " having longitudinal crack " also to describe in 5.

(evaluations of fatigue properties)

With regard to fatigue properties, by the use of the fixture as 4 dot points, implement four-point bending fatigue test repeatedly and commented Valency.In FIG, 1 test film (wire rod) is represented, 2 represent the direction for applying alternate stress, and zero represents supporting-point.Test is with unidirectional Bending (piece song げ) is carried out, and the difference of maximum stress and minimum stress is defined as into stress amplitude.10 are carried out with various stress amplitudes The repeated flex of ten thousand times, the judgement of complete unbroken (broken string) in the test of N=3 roots is qualified, even if there is 1 to rupture Also it is judged to unqualified.The maximum stress amplitude of qualified test portion is defined as 100,000 fatigue strength σ.100000 fatigue strength σ is displayed in table 5 below.Further, stress wave is sine wave, frequency 10Hz.

[table 4]

[table 5]

By these as a result, it is possible to be investigated as follows.

First, No.1～3,10～21 its chemical composition composition, metal structure (area occupation ratio of pearlite, pro-eutectoid α are tested Area occupation ratio, the average thickness of pro-eutectoid α) be in the range of the defined of the present invention, therefore obtained higher than JIS G " piano wire B classes " described in 3522 (1991) tensile strength (in specification, for example line footpath be 7.0mm, 1620～ 1770MPa), and the steel wire (steel wire) of fatigue strength that can obtain reaching the relation for meeting above-mentioned (1) formula.

In contrast, test No.4～9,22～27 be unsatisfactory for the present invention a certain important document example.Wherein test No.4, as shown in table 2, because heating-up temperature during split rolling method is low, thick TiC is separated out, pro-eutectoid α as shown in table 4 Average thickness become big, fatigue strength is reduced.

Test No.5, as shown in table 2, because heating-up temperature during hot rolling is low, so pro-eutectoid α's as shown in table 4 Area occupation ratio increases, and in addition solid solution B is also few, and fatigue strength is reduced.

Test No.6, as shown in table 2, rate of straining during finish to gauge is little, therefore thick TiC is separated out, as shown in table 4, The average thickness of pro-eutectoid α becomes big, and fatigue strength is reduced.

Test No.7, as shown in table 2, the mounting temperature after hot rolling is low, therefore generation mounting is bad, cannot get test portion.

Test No.8, as shown in table 2, the mounting temperature after hot rolling is high, TiC coarsenings, therefore as shown in table 4, pro-eutectoid α Average thickness become big, fatigue strength is reduced.

Test No.9, as shown in table 2, the average cooling rate after mounting is slow, as shown in table 4, the average thickness of pro-eutectoid α Greatly, fatigue strength is reduced.

The example that C measures few steel grade P is the use of and tests No.22, as shown in table 4, the area occupation ratio of pro-eutectoid α and average thickness Degree is all big, and twisting property and fatigue strength are reduced.

Test No.23 is the use of the example of many steel grade Q of C amounts, and substantial amounts of proeutectoid cementite is separated out, therefore in wire drawing There occurs broken string.

Test No.24 is the use of the example that Ti measures few steel grade R, and TiC amounts are few, and the average thickness of pro-eutectoid α is big, fatigue Intensity decreases.

Test No.25 is the use of the example of many steel grade S of Ti amounts, the Ti systems Inclusion Precipitation of volume and send out in wire drawing Raw broken string.

Test No.26 is the use of the example of many steel grade T of B amounts, broken string occurs during hot rolling and cannot get test portion.

Test No.27 is the use of the example that B measures few steel grade U, and the area occupation ratio of pro-eutectoid α is big, twisting property and fatigue Intensity decreases.

Fig. 2 is that the alternative microscope of EXAMPLEFigure of the test pro-eutectoid α observed by No.3 for being denoted as embodiment shines Piece.Ellipse 3 shown in Fig. 2 represents the precipitation position of pro-eutectoid α.As shown in Figure 2, the plate-like precipitations of pro-eutectoid α, can be easy to Ground differentiates " width " and " length direction " of crystal grain.

Claims

1. a kind of steel wire wire rod, wherein, in terms of quality %, contain respectively

C：0.70～1.3%,

Si：0.1～1.5%,

Mn：0.1～1.5%,

N：0.001～0.006%,

Al：0.001～0.10%,

Ti：0.02～0.20%,

B：0.0005～0.010%,

P：More than 0% and below 0.030%,

S：More than 0% and below 0.030%,

Surplus is iron and inevitable impurity,

With pearlite as principal phase, the area occupation ratio of pro-eutectoid ferrite is less than 1.0%, and the average thickness of pro-eutectoid ferrite For less than 5 μm.

2. steel wire wire rod according to claim 1, wherein, in terms of quality %, also containing belonging to following (a)～(d) Any one of more than one：

(c)Co：Higher than 0% and below 1.0%；

3. steel wire wire rod according to claim 1 and 2, wherein, the content of solid solution B is more than 0.0003%.

4. a kind of steel wire, wherein, the chemical composition of the steel described in claim 1 or 2 is constituted and constituted, 100,000 fatigue strength σ With the relation that tensile strength TS meets following (1) formulas,

σ ＞ 0.45TS ... (1).