CN106460119B

CN106460119B - Steel wire rod

Info

Publication number: CN106460119B
Application number: CN201580028871.7A
Authority: CN
Inventors: 大藤善弘; 手岛俊彦; 真锅敏之
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2014-06-02
Filing date: 2015-06-02
Publication date: 2019-01-11
Anticipated expiration: 2035-06-02
Also published as: KR101924709B1; EP3150738A4; CN106460119A; EP3150738A1; KR20160147041A; JP6288264B2; WO2015186701A1; JPWO2015186701A1

Abstract

本发明的目的是提供高强度且电阻率低的钢线材。该钢线材作为化学成分含有C、Si、Mn、Cr、Al，限制N、P、S，选择性地含有选自由Mo、V、Ti、Nb及B组成的组中的1种以上，剩余部分包含Fe及杂质。对于钢线材的组织而言，以面积率计85％以上为珠光体，上述珠光体的平均片层间距为50nm～100nm。另外，以质量％计，设上述Si的含量为[％Si]，设珠光体中的渗碳体中包含的Cr的含量为[％Crθ]，设珠光体中的铁素体中包含的Cr的含量为[％Crα]时，钢线材满足([％Crθ]/[％Crα])≥(2.0+[％Si]×10)。An object of the present invention is to provide a steel wire with high strength and low resistivity. The steel wire rod contains C, Si, Mn, Cr, and Al as chemical components, N, P, and S are limited, and optionally at least one selected from the group consisting of Mo, V, Ti, Nb, and B, and the remainder Contains Fe and impurities. The structure of the steel wire rod is pearlite in an area ratio of 85% or more, and the average interlamellar spacing of the pearlite is 50 nm to 100 nm. In addition, let the content of Si described above be [%Si], the content of Cr contained in cementite in pearlite be [%Crθ], and the content of Cr contained in ferrite in pearlite in terms of mass % When the content of α is [%Crα], the steel wire satisfies ([%Crθ]/[%Crα])≥(2.0+[%Si]×10).

Description

Steel wire rod

Technical field

The present invention relates to steel wire rods.

The application based on June 2nd, 2014 in the Patent 2014-114429 CLAIM OF PRIORITY of Japanese publication, and will be in it Appearance is incorporated herein.

Background technique

Aluminum stranded conductor used in power transmission line etc. uses the twisted wire of steel wire to reinforce intensity in internal core material.In this way Twisted wire be commonly referred to as steel-cored aluminium strand (Aluminum conductor STEEL-reinforced cable).Hereinafter, will Steel-cored aluminium strand is denoted as ACSR.

Steel wire most cases used in the core material of ACSR are with the pianos wire rod such as SWRS72B of JIS standard or SWRS82B work For raw material, and manufactured by cold-drawn wire.In the manufacture of ACSR, before cold-drawn wire or the centre of cold-drawn wire, as needed, Implement to be referred to as the heat treatment of patenting or processing of aluminizing.

In ACSR, not only in aluminum steel, but also also there is electric current in the steel wire of steel core.Therefore, if the resistivity of steel wire Greatly, then by ACSR integrally in terms of resistivity also become larger, the fever in transmission of electricity becomes larger.As a result, power transmission efficiency reduces.

In addition, needing to increase the big steel wire of resistivity ratio aluminium when the intensity of steel wire is low to reinforce intensity.However, due to Also have electric current in steel wire, so as a result, by ACSR integrally in terms of resistivity become larger.

For these reasons, it is desirable that the low and high-intensitive steel wire of resistivity and resistivity as its raw material are low simultaneously And high-intensitive steel wire rod.

The resistivity of steel generally rises with the increase of the content of the element in steel.Therefore, it discloses in patent document 1 Steel in, the content by reducing the essential elements such as C, Mn, Cr reduces resistivity.However, in the steel, due to For the purpose of the reduction of resistivity and the raising of cold forgeability, so the content of C and Si in steel are few.Therefore, tensile strength is not filled Point.

In addition, in spring steel plate disclosed in patent document 2, by making the content of C, Si, Mn in steel lower than rule It is worth shown in fixed formula, so that the resistivity of steel reduces.However, in the spring steel plate, due to organizing not by most Optimization, and Cr is not contained, so tensile strength can not be improved.Therefore, the reduced balance of intensity ensured with resistivity is not Sufficiently.

In turn, in patent document 3 in disclosed high-intensity and high-tenacity hypereutectoid steel wire, by C, Si in regulation steel, The content and tissue of Mn etc., so that it is guaranteed that tensile strength or wire drawing degree.However, in the high-intensity and high-tenacity hypereutectoid steel wire In, since Si content is 0.5% or more, and the optimization of tissue is not carried out in order to reduce resistivity, so resistivity It is high.

Patent Document 4 discloses shorten spheroidizing heat treatment time by increasing the Cr content in carbide Carbon steel wire rod with high.However, the carbon steel wire rod with high is due to being set as 6.0 mass % or more for the Cr content in carbide, so nothing Method reaches taking into account for the reduction of resistivity and the raising of tensile strength.

Existing technical literature

Patent document

Patent document 1: Japanese Unexamined Patent Publication 2003-226938 bulletin

Patent document 2: Japanese Unexamined Patent Publication 2004-156120 bulletin

Patent document 3: Japanese Unexamined Patent Publication 6-271937 bulletin

Patent document 4: International Publication No. 2012/144630

Summary of the invention

The technical problems to be solved by the invention

The present invention is given this situation, it is therefore an objective to provide high-intensitive and low resistivity steel wire rod.

Method for solving technical problem

It is following steel wire rods for steel wire rod of the invention: by particularly limiting the Si content for increase resistivity, In turn, increase the Cr content for including in the cementite in pearlite in the range of can take into account resistivity with tensile strength, On the contrary, making the Cr content for including in the ferrite in pearlite reduction, to prevent the rising of resistivity.In addition, passing through simultaneously The average platelet spacing for reducing pearlite, improves tensile strength, has taken into account the reduction of resistivity and the raising of tensile strength.

In addition, steel wire rod of the invention be implement cold-drawn wire before raw material, comprising hot rolling wire and to hot rolling wire into Steel obtained from row heat treatment.

The present inventors in order to solve the above problems, obtains high-intensitive and low resistivity steel wire rod, to steel wire rod Chemical component, tissue, alloying element distribution probe and research has been repeated.As a result, having obtained following (a)~(c) opinion.

(a) resistivity at room temperature of steel wire rod is due to less being changed by cold-drawn wire, thus steel wire rod at Point and cold-drawn wire before tissue or alloying element existence to after cold-drawn wire resistivity and tensile strength generate larger shadow It rings.

If (b) increasing Si content and Cr content, risen by the intensity of solution strengthening steel wire rod, but Si content Increase be substantially increased resistivity.On the other hand, the increase of Cr content can also be such that resistivity rises, but if compared with Si its It influences smaller.In addition, increasing resistivity if Cr is solid-solution in ferrite.Therefore, if increasing the Cr content in cementite, And reduce the Cr content in ferrite, then it is able to suppress the rising of resistivity.In other words, by making the carburizing in pearlite The Cr content for including in body, which increases and make the Cr content for including in the ferrite in pearlite, to be reduced, and resistivity is able to suppress Rise.

In addition, by correspondingly controlling the Cr content for including in cementite with the Si content for facilitating solution strengthening, it can It is taken into account with the raising of high efficiency control tensile strength and the reduction of resistivity.

In addition, after which, " the Cr content for including in the cementite in pearlite " is abbreviated as " in cementite sometimes " the Cr content for including in the ferrite in pearlite " is abbreviated as " the Cr content in ferrite " by Cr content ".

(c) in order to which the raising of tensile strength and the reduction of resistivity of reaching steel wire rod take into account, make the tissue of steel wire rod Tissue to be made of pearlite is effective.In turn, there is the case where pearlite of lamellar structure in ferrite and cementite Under, by reducing average platelet spacing, tensile strength can be made to improve.On the other hand, due between the average platelet in pearlite It is less big away from the influence generated to resistivity, so in order to reach taking into account for the reduction of the raising of tensile strength and resistivity, Preferably reduce average platelet spacing.

The present invention is carried out based on above-mentioned opinion, and purport is as described below.

(1) in the steel wire rod of one embodiment of the present invention, as chemical component in terms of quality % containing C:0.8%~ 1.1%, Si:0.02%~0.30%, Mn:0.1%~0.6%, Cr:0.3%~1.5%, Al:0.01%~0.05%, limit Be made as N:0.008% or less, P:0.03% or less, S:0.02% hereinafter, selectively containing selected from by Mo:0.20% or less, 1 kind in V:0.15% or less, Ti:0.050% or less, Nb:0.050% or less and B:0.0030% group consisting of with On, remainder includes Fe and impurity；Tissue includes pearlite, and the area ratio of above-mentioned pearlite is 85% or more；Above-mentioned pearly-lustre The average platelet spacing of body is 50nm~100nm；The content of above-mentioned Si is set in terms of quality % as [%Si], if in above-mentioned pearlite Cementite in include the content of above-mentioned Cr be [%Cr θ], if the above-mentioned Cr for including in ferrite in above-mentioned pearlite When content is [%Cr α], above-mentioned [%Si], above-mentioned [%Cr θ] and above-mentioned [%Cr α] meets following formula (a).

([%Cr θ]/[%Cr α]) >=(2.0+ [%Si] × 10) (a)

(2) in the steel wire rod described in above-mentioned (1), as above-mentioned chemical component, in terms of quality % can containing selected from by Mo:0.02%~0.20%, V:0.02%~0.15%, Ti:0.002%~0.050%, Nb:0.002%~0.050% and One or more of the group that B:0.0003%~0.0030% is formed.

(3) in the steel wire rod described in above-mentioned (1) or (2), the tensile strength TS of above-mentioned steel wire rod can for 1350MPa with On, also, the absolute value of the above-mentioned tensile strength TS of above-mentioned steel wire rod can be the unit of above-mentioned steel wire rod in terms of μ Ω cm 64 times or more of the absolute value of electricalresistivityρ.

Invention effect

According to each mode of above-mentioned (1)~(3), it is capable of providing high-intensitive and low resistivity steel wire rod.On especially The raw material of the few steel wire of the power consumption that the steel wire rod for stating mode reinforces purposes as the intensity for power transmission line are suitable.

In addition, implementing cold-drawn wire to the steel wire rod of aforesaid way and implementing processing of aluminizing as needed after cold-drawn wire Obtained from steel wire be high intensity, and resistivity is low.Therefore, if manufacturing ACSR using the steel wire, can ensure to provide Intensity, and then the small ASCR of resistivity can be obtained.Therefore, the contribution in industry is extremely significant.

Specific embodiment

The steel wire rod of present embodiment is illustrated.

Firstly, being illustrated to the restriction reason of the chemical component of the steel wire rod in present embodiment.In addition, theory below % in bright refers to quality %.

C:0.8%~1.1%

C is to metal structure pearlite, the raising effective element of tensile strength for making steel wire rod.

In the case where C content is lower than 0.8%, for example, steadily assigning tensile strength to steel wire rod is 1350MPa or so High intensity become difficult.It therefore, is 0.8% by the lower limit set of C content.Pearlite in order to obtain more evenly and improve anti- Tensile strength, C content are preferably 0.9% or more, and more preferably 1.0% or more.

On the other hand, if C content is excessive, hardening occurs for steel wire rod, leads to the reduction of wire-drawing workability.If especially C content is more than 1.1%, then due to industrially steadily inhibiting, the cementite being precipitated along old austenite grain boundary, i.e. just analysis is seeped The generation of carbon body becomes difficult, so wire-drawing workability substantially reduces.Therefore, the upper limit of C content is set as 1.1%.

Si:0.02%~0.30%

Si is to the effective element of the intensity for improving steel wire rod by solution strengthening, in addition, being also must as deoxidier The element wanted.

When Si content is lower than 0.02%, these effects are insufficient.It therefore, is 0.02% by the lower limit set of Si content.This Outside, in order to ensure intensity by solution strengthening, in turn, more stably enjoy deoxidation effect, Si content be preferably 0.05% with On.

On the other hand, if Si content increases, resistivity increases.If especially Si content is more than 0.30%, can not be simultaneous Care for the raising of tensile strength and the reduction of resistivity.Therefore, the upper limit of Si content is set as 0.30%.It is lower in order to obtain Resistivity, Si content are preferably 0.20% hereinafter, more preferably 0.10% or less.

Mn:0.1%~0.6%

Mn is to fix with the intensity for improving steel wire rod while as MnS the S in steel wire rod, preventing hot short effect The element of fruit.

When Mn content is lower than 0.1%, these effects are insufficient.It therefore, is 0.1% by the lower limit set of Mn content.In turn, In order to ensure intensity, red brittleness is further prevented, Mn content is preferably 0.2% or more, and more preferably 0.3% or more.

On the other hand, if Mn content increases, resistivity increases.If especially Mn content is more than 0.6%, cannot be considered in terms of The raising of tensile strength and the reduction of resistivity.Therefore, the upper limit of Mn content is set as 0.6%.Lower electricity in order to obtain Resistance rate, Mn content are preferably 0.5% hereinafter, more preferably 0.4% or less.

Cr:0.3%~1.5%

Cr has the effect of the tensile strength for reducing the average platelet spacing of pearlite and improving steel wire rod.In addition, if Cr It is solid-solution in the ferrite in pearlite, then increases resistivity.Therefore, by increasing the Cr content in cementite, and opposite drop Cr content in low ferrite, to have the effect of inhibiting the rising of resistivity.

When Cr content is lower than 0.3%, it is unable to ensure the tensile strength of sufficient steel wire rod, the Cr in cementite can not be made to contain Amount increases.Therefore, the reduction of the raising of tensile strength and resistivity in order to balance needs to make 0.3% or more Cr content.In order to Higher tensile strength is obtained, Cr content is preferably 0.4% or more, and more preferably 0.5% or more.

On the other hand, if Cr content is more than 1.5%, the wire-drawing workability of steel wire rod is reduced.Therefore, by the upper of Cr content Limit is set as 1.5%.In order to further suppress the reduction of wire-drawing workability, Cr content is preferably 1.0% hereinafter, more preferably 0.8% or less.

Al:0.01%~0.05%

Al is the element with deoxidation effect, is element necessary in order to reduce the oxygen amount in steel wire rod.

When Al content is lower than 0.01%, effect is insufficient.It therefore, is 0.01% by the lower limit set of Al content.In order to Deoxidation effect is further obtained, Al content is preferably 0.02% or more.

On the other hand, Al is the element to form the oxide system field trash of hard and deteriorate the ductility of steel wire rod.It is special If not being Al content is more than 0.05%, become easy to form coarse oxide system field trash, so the wire drawing of steel wire rod adds Work significantly reduces.Therefore, the upper limit of Al content is set as 0.05%.In order to not make the wire-drawing workability of steel wire rod further It more reduces, Al content is preferably 0.04% hereinafter, more preferably 0.03% or less.

In the steel wire rod of present embodiment, in turn, N, P and S need following limitation.

N:0.008% or less

N is the dislocation being fixed in steel in cold-drawn wire and the element that reduces wire-drawing workability.If especially N content is super 0.008% is crossed, then the reduction of wire-drawing workability becomes significant.Therefore, N content is limited to 0.008% or less.Preferably 0.005% hereinafter, more preferably 0.004% or less.

In addition, the lower limit of N content includes 0%.However, if considering the refining techniques and manufacturing cost of status, N content Lower limit is preferably 0.0001%.

P:0.03% or less

P is the element for being segregated in crystal boundary and reducing wire-drawing workability.If especially P content is more than 0.03%, draw The reduction of silk processability becomes significant.Therefore, P content is limited to 0.03% or less.Preferably 0.02% hereinafter, more preferably 0.01% or less.

In addition, the lower limit of P content includes 0%.However, if considering current refining techniques and manufacturing cost, P content Lower limit is preferably 0.001%.

S:0.02% or less

S is also the element for reducing wire-drawing workability in the same manner as P.If especially S content is more than 0.02%, wire drawing adds The reduction of work becomes significant.Therefore, S content is limited to 0.02% or less.Preferably 0.01% or less.

In addition, the lower limit of S content includes 0%.However, if considering current refining techniques and manufacturing cost, S content Lower limit is preferably 0.001%.

It is the basic at being grouped as of the steel wire rod of present embodiment above, remainder is iron and impurity.In addition, " surplus Remaining part is divided into Fe and impurity " in " impurity " refer to industrially manufacture steel when as the ore of raw material, waste material or from manufacture ring The inevitably mixed substance such as border.

However, in steel wire rod in present embodiment, other than the basis, instead of one of the Fe of remainder Point, contain selected from by one or more of Mo, V, Ti, Nb and B group formed with also can choose.

Mo:0.20% or less

The addition of Mo is arbitrary, and the lower limit of content is 0%.

However, can steadily enjoy the balance of the tensile strength and resistivity that improve steel wire rod by the addition of Mo Effect.The effect in order to obtain preferably adds 0.02% or more Mo.More preferable Mo content is 0.05% or more.

On the other hand, it if Mo content is more than 0.20%, becomes easy and generates martensitic structure in steel, wire drawing adds sometimes Work reduces.Therefore, the upper limit of Mo content is preferably 0.20%.The upper limit of more preferable Mo content is 0.10%.

V:0.15% or less

The addition of V is arbitrary, and the lower limit of content is 0%.

However, V has the effect of reducing pearlite block size and forming carbide or carbonitride in steel wire rod. Therefore, by the addition of V, wire-drawing workability can be made to improve.The effect in order to obtain preferably adds 0.02% or more V.More It is preferred that V content is 0.05% or more.

On the other hand, it if V content is more than 0.15%, becomes easy and forms coarse carbide or carbon nitrogen in steel wire rod Compound, wire-drawing workability reduces sometimes.Therefore, the upper limit of V content is preferably 0.15%.The upper limit of more preferable V content is 0.08%.

Ti:0.050% or less

The addition of Ti is arbitrary, and the lower limit of content is 0%.

However, Ti has the effect for reducing pearlite block size and forming carbide or carbonitride in steel wire rod Fruit.Therefore, by the addition of Ti, it can be improved wire-drawing workability.The effect in order to obtain preferably adds 0.002% or more Ti.More preferable Ti content is 0.005% or more.

On the other hand, it if Ti content is more than 0.050%, becomes easy and forms coarse carbide or carbon in steel wire rod Nitride, wire-drawing workability reduces sometimes.Therefore, the upper limit of Ti content is preferably 0.050%.The upper limit of more preferable Ti content is 0.030%.

Nb:0.050% or less

The addition of Nb is arbitrary, and the lower limit of content is 0%.

However, Nb has the effect of forming carbide or carbonitride in steel wire rod and reducing pearlite block size.Cause This can be improved wire-drawing workability by the addition of Nb.The effect in order to obtain preferably adds 0.002% or more Nb.More It is preferred that Nb content is 0.005% or more.

On the other hand, it if Nb content is more than 0.050%, becomes easy and forms coarse carbide or carbon in steel wire rod Nitride, wire-drawing workability reduces sometimes.Therefore, the upper limit of Nb content is preferably 0.050%.The upper limit of more preferable Nb content is 0.020%.

B:0.0030% or less

The addition of B is arbitrary, and the lower limit of content is 0%.

However, B has the effect of forming BN in conjunction with the N being dissolved in steel wire rod and reducing solid solution N.Therefore, pass through B's Addition, can be improved wire-drawing workability.The effect in order to obtain preferably adds 0.0003% or more B.More preferable B content is 0.0007% or more.

On the other hand, it if B content is more than 0.0030%, becomes easy and forms coarse carbide in steel wire rod, have When wire-drawing workability reduce.Therefore, the upper limit of B content is preferably 0.0030%.The upper limit of more preferable B content is 0.0020%.

Then, the tissue of the steel wire rod of present embodiment is illustrated.

The tissue of the steel wire rod of present embodiment becomes the pearlite of the lamellar structure of stratiform comprising ferrite and cementite. The Main Tissues of the steel wire rod of present embodiment are pearlite.Here, " Main Tissues " refer in the length direction with steel wire rod In the vertical section C or in the L section parallel with the length direction of steel wire rod, 85% or more tissue is accounted in terms of the area ratio. The area ratio that the area ratio of pearlite can subtract non-pearlite tissue by 100% and find out.The area ratio of pearlite is 85% More than, preferably 90% or more, more preferably 95% or more.In addition, the area ratio of pearlite may be 100%.

The remainder of the tissue of the steel wire rod of present embodiment, the tissue i.e. in addition to pearlite by just analyse ferrite or Bainite, pseudopearlite, just the non-pearlites organizational composition such as analysis cementite.If not the area ratio of pearlitic structrure is more than 15%, Then wire-drawing workability reduces.Therefore, the area ratio of non-pearlite tissue is 15% or less.The area ratio of non-pearlite tissue is preferred For 10% hereinafter, more preferably 5% or less.In addition, the area ratio of non-pearlite tissue may be 0%.

The area ratio of pearlite can be found out as follows.

For example, shown in embodiment as be described hereinafter like that, in the sample of steel wire rod, by the length direction with steel wire rod After the vertical section C carries out mirror ultrafinish, corrode the section C with nitric acid ethyl alcohol.

Then, to the sample corroded through nitric acid ethyl alcohol, using SEM, with 5000 times of multiplying power, 10 are shot to arbitrary position The visual field.In addition, the area in every 1 visual field is set as 3.6 × 10^-4mm²。

Each visual field can be found out by the method for common image analysis using the SEM photograph in obtained each visual field The area ratio of pearlite.

In turn, it is averaged by the area ratio for the pearlite for measuring obtained 10 visuals field, obtains the pearly-lustre of the steel wire rod The area ratio of body.

The average platelet spacing of pearlite: 50nm~100nm

The tensile strength of steel wire rod can be improved by reducing the average platelet spacing of above explained pearlite.Separately Outside, the influence that average platelet spacing gives resistivity is less big.Therefore, in order to reach steel wire rod tensile strength raising With taking into account for the reduction of resistivity, need to reduce average platelet spacing.If the average platelet spacing of pearlite is more than 100nm, The improvement effect of tensile strength becomes inadequate.Therefore, in the steel wire rod of present embodiment, the effect in order to obtain, by pearly-lustre The average platelet spacing of body is set as 100nm or less.The average platelet spacing of pearlite is preferably 75nm or less.

On the other hand, it in order to make the average platelet spacing of pearlite lower than 50nm, needs to carry out phase transformation with low temperature.However, If carrying out phase transformation with low temperature, the area ratio of the non-pearlites tissue such as bainite is more than 15%, the wire-drawing workability drop of steel wire rod It is low.Therefore, the average platelet spacing of pearlite is set as 50nm or more.The average platelet spacing of pearlite be preferably 55nm with On.

The average platelet spacing of pearlite can be determined as follows.For example, shown in embodiment as be described hereinafter like that, After the section C of the sample of steel wire rod is ground, which is etched, pearlite occurs.Then, pass through scanning Type electron microscope (SEM) is shot the section C of appearance pearlite with multiple visuals field, obtains the macrograph of sample.Pass through The obtained macrograph can measure the average platelet spacing of pearlite.

Specifically, can be measured by following method.Firstly, the tissue for shooting 10 visuals field shines using SEM Piece.It in the consistent range in the direction of lamella, is selected multiple in the visual field in the macrograph in captured each 10 visuals field The position of 5 amount of separation of lamella can be measured.To selected multiple positions, straight line is vertically drawn with lamella, finds out lamella 5 amount of separation length.Then, 2 are selected from the small position of the length of 5 amount of separation in selected multiple positions Position.It then,, can by the length of 5 amount of separation of the lamella that will be measured respectively divided by 5 in selected 2 positions Find out the piece interlamellar spacing at each position.That is, the piece interlamellar spacing at 2 positions can be found out with 1 visual field.It can be by find out in this way 10 " the average platelet spacing of pearlite " of the average value of the piece interlamellar spacing in the visual field, total 20 positions as the sample.

As described above, in order to improve the tensile strength of steel wire rod, the average platelet spacing for reducing pearlite is Effectively.Like this, in order to reduce the average platelet spacing of pearlite, preferably: by the cooling speed in the cooling process after hot rolling Degree is set as 50 DEG C/sec or more, later, makes its pearlitic transformation with 600 DEG C or so of low temperature.

Electricity flows mainly through ferritic portion in pearlite.In addition, having if Cr is solid-solution in the ferrite in pearlite Play the role of increasing resistivity.Therefore, if can reduce the Cr content for including in the ferrite in pearlite, electricity can be reduced Resistance rate.That is, keeping the Cr content for including in the ferrite in pearlite opposite by being enriched with Cr in the cementite in pearlite It reduces, is able to suppress the rising of the resistivity of steel wire rod.In addition, Cr is the member being enriched in the cementite being easy in pearlite Element.Therefore, it by the control of heat treatment condition, can be improved the Cr content for including in the cementite in pearlite, reduce pearly-lustre The Cr content for including in ferrite in body.

In addition, Si contributes to the element of solution strengthening.Therefore, it if the Si content in steel wire rod increases, can be improved The intensity of steel wire rod.But another aspect, if the Si content in steel wire rod increases, resistivity becomes larger.Therefore, with Si Content increases, and by improving the Cr content for including in the cementite in pearlite, can take into account high tensile strength and low electricity Resistance rate.

In the steel wire rod of present embodiment, these effects in order to obtain, Si content, the infiltration in pearlite in terms of quality % The Cr content for including in the ferrite in Cr content and pearlite for including in carbon body meets following formula (1) and is important.Wherein, In following formula (1), in terms of quality %, Si content is [%Si], and the Cr content for including in the cementite in pearlite is [%Cr θ], the Cr content for including in the ferrite in pearlite is [%Cr α].

([%Cr θ]/[%Cr α]) >=(2.0+ [%Si] × 10) (1)

In steel wire rod in the present embodiment, in the way of meeting above-mentioned formula (1), by with facilitate solution strengthening The content of Si correspondingly control the Cr content for including in the cementite in pearlite, can be according to the raising for taking into account tensile strength It is controlled with the reduced mode of resistivity.

[%Cr θ] in the Cr content that includes in cementite in pearlite, i.e. above-mentioned formula (1) for example can be to passing through electricity The residue for solving and extracting carries out chemical analysis and finds out.Specifically, can be found out by following method.Firstly, incite somebody to action this After the steel wire rod of embodiment is cut into the size suitable for electrolysis, general condition, that is, 10%AA system electricity of electrolytic polishing is used Liquid is solved, current density is set as 250~350A/m²It is electrolysed, solution is extracted.Then, by extracted solution It is filtered with the filter that screen size is 0.2 μm, obtains residue.It, can be by carrying out general chemistry to filtrate, i.e. residue It analyzes and finds out.Wherein, as general chemical analysis, such as it can enumerate and be dissolved residue by acid solution, and this is molten The method that liquid is analyzed by ICP luminescence spectrometer method.In the steel wire rod of present embodiment, due in the cementite in pearlite The metallic element for including is essentially Fe, Mn and Cr, Fe and Cr therein from low a possibility that extraction in addition to cementite, into And MnS is more readily formed than cementite in Mn, so Cr content, i.e. [the %Cr θ] for including in cementite in pearlite can make It is calculated with following formula (2).Wherein, in following formula (2), in terms of quality %, by the Cr content for including in residue, Fe content and Mn content is set to [% residue Cr], [% residue Fe] and [% residue Mn], is furthermore set as the S content for including in steel wire rod [%S].

[%Cr θ]=100 × [% residue Cr]/[% residue Fe]+[% residue Mn]+[% residue Cr]-[%S] × (55/32)} (2)

In addition, in order to reach the reduction of the raising of tensile strength and resistivity, the Cr for including in the cementite in pearlite Content is preferably 0.80%~5.80% in terms of quality %.

Furthermore the Cr content for including in the ferrite in pearlite can premised on C is not dissolved substantially in ferrite, Such as it is [%Cr], Cr content i.e. [the %Cr θ] for including in the cementite in pearlite by the Cr content of steel wire rod entirety and is led to Volume fraction i.e. [the φ θ] for crossing the cementite that C content is found out is calculated.It is known that since C is not substantially solid in ferrite It is molten, so the volume fraction of the cementite in pearlite is generally found out by following formula (3).In following formula (3), with matter Amount % meter sets C content as [%C], if the volume fraction of the cementite in pearlite is [φ θ].

In addition, 0.149 of the coefficient in following formula (3) can be by the 6.69 mass %C formed and cementite of cementite Density 7.68g/cm³It obtains.

[φ θ]=[%C] × 0.149 (3)

Then, the ferritic volume fraction in pearlite, i.e. [φ α] can be found out by following formula (4).

[φ α]=1.0- [φ θ] (4)

According to above content, following formula is can be used in Cr content, i.e. [the %Cr α] for including in the ferrite in pearlite (5) it calculates.

[%Cr α]={ [%Cr]-([%Cr θ] × [φ θ]) }/[φ α] (5)

As described above, in order to inhibit steel wire rod resistivity rising, being enriched with Cr in cementite is to have Effect.Like this, in order to be enriched with Cr in cementite, preferably: after completing the pearlitic transformation from austenite, in the temperature It is kept in region and is enriched with Cr in cementite.However, if being kept in the temperature region after the completion of pearlitic transformation Time is elongated, then spheroidizing, the strength reduction of steel wire rod occur for the cementite in pearlite sometimes.

The tensile strength TS of the steel wire rod of present embodiment is preferably 1350MPa or more.In addition, also, steel wire rod it is anti- The absolute value of tensile strength TS is preferably 64 times or more of the absolute value of electricalresistivityρ of the unit in terms of μ Ω cm.

When the steel wire rod of present embodiment to be suitable for the core material of ACSR, if the intensity of steel wire rod is low, become sometimes Need to increase steel wire rod to reinforce intensity.In this case, be contemplated to by ACSR integrally in terms of resistivity become larger.Therefore, this implementation The tensile strength TS of the steel wire rod of mode is preferably 1350MPa or more, more preferably 1400MPa or more, further preferably 1500MPa or more.In addition, the tensile strength TS 1350MPa or more by making steel wire rod, such as arrived in gauge or diameter of wire for 11mm When 5mm, with general wire drawing amount, that is, true strain for 1.6, the tensile strength 1900MPa of the steel wire after cold-drawn wire can be made More than.

Furthermore in the steel wire rod of present embodiment, from the viewpoint of the high intensity and low-resistivity of taking into account steel wire rod, In the relationship of the absolute value of the electricalresistivityρ in terms of μ Ω cm of absolute value and unit of tensile strength TS, it is preferably set to following Numberical range.

The use generally used in the core material of ACSR has the change of SWRS72B, SWRS82B specified in JIS G 3502 The absolute value of the tensile strength TS for the wire rod that the steel studied point is manufactured with general hot-rolled condition is the absolute value of its electricalresistivityρ About 55 times.In addition, the unit of the tensile strength of wire rod is MPa, the unit of resistivity is μ Ω cm.

Therefore, as described above, if resistivity as unit of the absolute value of the tensile strength TS of wire rod in terms of μ Ω cm On the basis of 55 times of the absolute value of ρ, be even worth on the basis of 55 times, then in the steel wire rod of present embodiment, preferably: according at On the basis of 15% or more the mode that is worth, the absolute value of tensile strength TS reaches the absolute of electricalresistivityρ of the unit in terms of μ Ω cm 64 times or more of value.In addition, more preferably: in the way of becoming 20% or more of a reference value, the absolute value of tensile strength TS reaches To 67 times or more of the absolute value of electricalresistivityρ of the unit in terms of μ Ω cm.

Like this, by the way that the tensile strength TS of steel wire rod is set as 1350MPa or more, and the tension of steel wire rod is strong The absolute value for spending TS sets 64 times or more of the absolute value for electricalresistivityρ of the unit in terms of μ Ω cm, can be improved steel wire rod Intensity reduces resistivity.As a result, reinforcement radical when steel wire rod to be suitable for the core material of ACSR can be reduced.In turn, Be able to suppress by ACSR integrally in terms of resistivity rising, the fever being able to suppress in transmission of electricity, it can be ensured that stable transmission of electricity effect Rate.

In addition, for the absolute value of electricalresistivityρ of the unit in terms of μ Ω cm, not having in the steel wire rod of present embodiment It is particularly limited to.That is, the electricity of the absolute value and unit of the preferably above-mentioned tensile strength TS of the steel wire rod of present embodiment in terms of μ Ω cm The absolute value of resistance rate ρ meets following formula (6).

Absolute value >=electricalresistivityρ absolute value × 64 (6) of tensile strength TS

Meet the steel wire rod of above-mentioned formula (6) by being made, it can be ensured that especially big tensile strength compared with the past.It is tied Fruit is the reinforcement radical that can be reduced by such steel wire rod suitable for the core material of ACSR and when being reinforced, be able to suppress with The rising for the resistivity that ACSR is integrally counted.

In addition, the electricalresistivityρ of the steel wire rod in present embodiment the low the more preferred, and then the bigger tensile strength TS the more excellent Choosing.

By meeting above-mentioned chemical composition and tissue, the reduction of the raising and resistivity that have taken into account intensity can be obtained Steel wire rod.Above-mentioned steel wire rod in order to obtain, as long as manufacturing steel wire rod by aftermentioned manufacturing method.Then, to this The preferred manufacturing method of the steel wire rod of embodiment is illustrated.

The steel wire rod of present embodiment can manufacture as described below.In addition, the manufacturer of steel wire rod described below Method is an example for obtaining the steel wire rod of present embodiment, is not limited with following step and method, as long as The method that can be realized composition of the invention can then use any method.

Firstly, by become above-mentioned chemical component in the way of by steel melting after, pass through continuously casting manufacture steel billet, carry out Hot rolling.In addition, split rolling method can also be carried out after continuously casting.When obtained steel billet is carried out hot rolling, according to steel billet Central part become 1000 DEG C~1100 DEG C of mode, heated by general method, final rolling temperature be set as 900 DEG C ~1000 DEG C of progress hot rollings.After finish rolling, by water cooling and using the air-cooled combination of atmosphere, the wire rod of hot rolling is once cooled to 700 DEG C or less.Average cooling rate in the primary cooling is preferably 50 DEG C/sec or more.After primary cooling, in order to make its pearl Wire rod is impregnated in the fuse salt of 500 DEG C~530 DEG C nitrate systems by body of light phase transformation, and secondary cooling is to 590 DEG C~620 DEG C.So It afterwards, can by being kept for 30 seconds~50 seconds the wire rod after secondary cooling in the fuse salt that bath temperature is 550 DEG C~570 DEG C It is enriched with Cr in cementite.Later, fuse salt is removed by spray water, is cooled to room temperature, is then batched three times. In addition, batching can also carry out immediately after primary cooling or secondary cooling.

In addition, average cooling rate is preferably 30 DEG C/sec or more in above-mentioned secondary cooling.In addition, in secondary cooling In holding afterwards, preferably kept for 30 seconds~50 seconds in the range of the temperature of wire rod reaches 600 DEG C~550 DEG C.For example, it is also possible to Use lead bath or fluosolids furnace.Using lead bath, in primary cool down, 700 DEG C can not also be reduced to, it can also be with Secondary cooling and holding are carried out with same lead bath.In this case, it is preferred that kept in 550 DEG C~600 DEG C of lead bath 35 seconds~ 60 seconds.

As after finish rolling cooling and keeping method, only can also be cooled down and kept with lead bath.For example, in finish rolling In the range of the temperature of wire rod afterwards is 900 DEG C~700 DEG C, when in the lead bath that the temperature for being impregnated in lead bath is 640 DEG C~500 DEG C Wire rod average cooling rate be 100 DEG C/sec~200 DEG C/sec.

In addition, the temperature of the wire rod after finish rolling be 700 DEG C~620 DEG C in the range of, lead bath temperature be 590 DEG C~ At 600 DEG C, the average cooling rate of wire rod is 40 DEG C/sec~50 DEG C/sec, when the temperature of lead bath is 550 DEG C~560 DEG C, line The average cooling rate of material is 60 DEG C/sec~70 DEG C/sec, and when the temperature of lead bath is 490 DEG C~500 DEG C, being averaged for wire rod is cold But speed is 90 DEG C/sec~100 DEG C/sec.

In addition, the final rolling temperature in above-mentioned hot rolling refers to the surface temperature of the steel wire rod after rigid finish rolling.In turn, after finish rolling Cooling in average cooling rate refer to steel wire rod surface cooling velocity.

Embodiment

Hereinafter, enumerate the embodiment of steel wire rod of the invention, more specifically to the effect of the steel wire rod of present embodiment It is illustrated.But the condition in embodiment is the condition used to confirm exploitativeness and effect of the invention Example, the present invention is not limited to following embodiments.Without departing from purport of the invention, and reach the purpose of the present invention, It can suitably be changed and be implemented in the range of being suitably adapted for purport.Thus, the present invention can use various conditions, they It is both contained in technical characteristic of the invention.

After steel A~Y with chemical composition shown in table 1 is melted with 50kg vacuum fusion furnace, it is cast as ingot bar.Separately Outside, the chemical component of steel V meets the SWRS82B of JIS standard.

After above-mentioned each ingot bar is heated 1 hour at 1250 DEG C, in such a way that final rolling temperature reaches 950 DEG C or more, Warm and hot forging to diameter is that 15mm is let cool to room temperature later, obtains warm and hot forging material.The warm and hot forging material is passed through into machining And cutting obtains the machining material that diameter is 10mm, length is 1000mm.

Then, obtained each machining material is carried out heating for 15 minutes in 1050 DEG C of nitrogen atmosphere, will be cut The central temperature of rapidoprint is set as 1000 DEG C or more.Later, reach 950 DEG C or more and 1000 DEG C or less according to final rolling temperature In the range of mode, the diameter of machining material is hot-rolled down to 7mm, obtains wire rod.In turn, with the temperature of wire rod for 900 DEG C or more state, be impregnated in lead bath and keep under the conditions of shown in the table 2.Later, wire rod is taken out from lead bath, is put It is cooled to room temperature, obtains steel wire rod.

It is 640 DEG C~500 DEG C in the temperature of lead bath in the range of the temperature of wire rod after finish rolling is 900 DEG C~700 DEG C When, the average cooling rate of wire rod is 100 DEG C/sec~200 DEG C/sec.

In addition, to a part of obtained machining material, being hot-rolled down to diameter in order to compare as 7mm and obtaining line It after material, does not impregnate in fuse salt or lead bath, is cooled to room temperature by letting cool in atmosphere or using the air-cooled of ventilating fan, Obtain steel wire rod.About the average cooling rate of wire rod when letting cool in an atmosphere, the temperature of the wire rod after finish rolling is 900 DEG C It is 7 DEG C/sec~8 DEG C/sec when~700 DEG C of range, in addition, the range that the temperature of the wire rod after finish rolling is 700 DEG C~620 DEG C When be 4 DEG C/sec~5 DEG C/sec.Line about the average cooling rate of wire rod when carrying out air-cooled by ventilating fan, after finish rolling It is 12 DEG C/sec~14 DEG C/sec when the range that the temperature of material is 900 DEG C~700 DEG C, in addition, the temperature of the wire rod after finish rolling is It is 6 DEG C/sec~7 DEG C/sec when 700 DEG C~620 DEG C of range.

To with the steel wire rod of the test number 1~48 of above-mentioned each condition manufacture, implements each test as shown below and go forward side by side Row evaluation.

To each steel wire rod, after the section C vertical with the length direction of steel wire rod is carried out mirror ultrafinish, with nitric acid ethyl alcohol into Row corrosion.

It is right with 5000 times of multiplying power using SEM to the sample corroded through nitric acid ethyl alcohol in order to find out the area ratio of pearlite Arbitrary position shoots 10 visuals field.In addition, the area in every 1 visual field is 3.6 × 10^-4mm²。

Then, in the photo in each visual field, the area of the part of pearlite is found out by the method for common image analysis Rate.Using the average value of the area ratio of the pearlite of 10 visuals field amount as the area ratio of the pearlite of the steel wire rod.

In addition, in order to find out the average platelet spacing of pearlite, to the sample corroded through nitric acid ethyl alcohol, using SEM, with again 10000 times of rate, 10 visuals field are shot to arbitrary position.In addition, the area in every 1 visual field is 9.0 × 10^-5mm²。

Then, in the photo in each visual field, the consistent range in the direction of the lamella of pearlite is selected.Then, to can survey 5 amount of separation of stator layer and the smallest position of piece interlamellar spacing and the small position of piece interlamellar spacing the 2nd, vertically draw with lamella Straight line finds out the length of 5 amount of separation of lamella.In turn, by by the length of 5 amount of separation of obtained lamella divided by 5, Find out the piece interlamellar spacing of the pearlite at each position.Find out in this way 10 visuals field are measured to, are added up to the piece interlamellar spacing at 20 positions Average platelet spacing of the average value as the pearlite of the steel wire rod.

Steel wire rod is cut into after diameter is 6mm, using general condition, that is, 10%AA system electrolyte of electrolytic polishing, Current density is set as 250~350A/m²And be electrolysed, solution is extracted.In addition, above-mentioned 10%AA system is electrolysed Liquid is -1 quality % tetramethyl ammonium chloride of 10 volume % acetylacetone,2,4-pentanedione-methanol solution.Then, by extracted solution sieve pore ruler The very little filter filtering for being 0.2 μm, is obtained residue, is dissolved residue using acid solution, which is passed through ICP luminescence spectrometer method It is analyzed, obtains Cr content [% residue Cr], Fe content [% residue Fe] and the Mn content [% residue Mn] in residue.Into And Cr content, i.e. [the %Cr θ] for including in the cementite in pearlite is calculated using following formula (A).In addition, with " cementite In metallic element be substantially made of Fe, Mn and Cr ", " Fe and Cr are not extracted from other than cementite " and " comprising S in steel When, Mn is initially formed MnS " as precondition than cementite.Wherein, it in following formula (A), in terms of quality %, will be wrapped in residue Cr content, Fe content and the Mn content contained is set to [% residue Cr], [% residue Fe] and [% residue Mn], furthermore by steel wire The S content for including in material is set as [%S].

[%Cr θ]=100 × [% residue Cr]/[% residue Fe]+[% residue Mn]+[% residue Cr]-[%S] × (55/32)} (A)

Furthermore the Cr content in ferrite calculates as follows.Firstly, finding out the cementite in pearlite by following formula (B) After volume fraction [φ θ], the ferritic volume fraction [φ α] in pearlite is found out by following formula (C).Later, under It states formula (D), calculates the Cr content [%Cr α] in ferrite.

In addition, in terms of quality %, the C content of steel wire rod entirety is set as [%C], in following formula in following formula (B) (D) in, in terms of quality %, the Cr content of steel wire rod entirety is set as [%Cr].

[φ θ]=[%C] × 0.153 (B)

[φ α]=1.0- [φ θ] (C)

[%Cr α]={ [%Cr]-([%Cr θ] × [φ θ]) }/[φ α] (D)

By machining, the diameter for respectively acquiring 2 parallel portions from the central part in the section C of each steel wire rod be 3.2mm (with The circle that radius centered on the center in the section C is 1.6mm), the tension test sheet that length is 18mm, pass through according to JIS Z 2241 Method, carry out room temperature under tension test, measure tensile strength TS.In turn, using the average value measured as the steel wire rod Tensile strength TS.In addition, the unit of tensile strength TS is MPa.

As the test film for measuring electricalresistivityρ, 3.0mm × 4.0mm × 60mm is acquired from the central part of each steel wire rod Cuboid test film, at 20 DEG C of temperature pass through common 4 terminal method, measure resistivity.The list of obtained electricalresistivityρ Position is μ Ω cm.

Will be obtained evaluation result is shown in table in 3 and table 4.In addition, [%Cr θ] and [%Cr α] point in table 3 and table 4 " the Cr content for including in the cementite in pearlite ", " Cr for including in the ferrite in pearlite are not indicated in terms of quality % Content ".

In addition, in table 3 and table 4, the case where meeting above-mentioned formula (1), is set as qualified and is indicated with " 〇 ", will be unsatisfactory for The case where above-mentioned formula (1), is set as unqualified and is indicated with "×".

In addition, electricalresistivityρ's by unit by the tensile strength TS of the MPa steel wire rod indicated, unit in terms of μ Ω cm is exhausted 64 times of value of the absolute value of value and electricalresistivityρ is shown in table 3 and table 4.

In addition, being the exhausted of electricalresistivityρ of the unit in terms of μ Ω cm by the absolute value of tensile strength TS in table 3 and table 4 " good " is judged as to 64 times or more of situation of value and be judged as the case where indicating with " 〇 ", will be less than 64 times " bad " and with "×" indicates.

By table 3 and table 4, test number 1,3,6,7,9~11,14,17,18,20~22,24,26,27,30,33,34, In the case where 36 and 44~47, it is unsatisfactory for chemical composition, tissue specified in the present invention, the average platelet spacing of pearlite, Si In the relationship for the Cr content for including in the ferrite in Cr content and pearlite for including in cementite in content and pearlite At least one technical characteristic.In addition, the wire-drawing workability of test number 45 and 47 reduces.

It is opposite with them, test number 2,4,5,8,12,13,15,16,19,23,25,28,29,31,32,35,37~43 And 48 meet chemical composition specified in the present invention, tissue, the average platelet spacing of pearlite, the infiltration in Si content and pearlite The whole of the relationship for the Cr content for including in the ferrite in Cr content and pearlite for including in carbon body.

Table 2

Industrial availability

In accordance with the invention it is possible to obtain high-intensitive and low resistivity steel wire rod, the contribution in industry is extremely significant.

Claims

1. A steel wire rod, characterized in that, as a chemical component, it contains in mass %:

C: 0.8% to 1.1%,

Si: 0.02% to 0.30%,

Mn: 0.1% to 0.6%,

Cr: 0.3% to 1.5%,

Al: 0.01% to 0.05%,

limited to

N: 0.008% or less,

P: 0.03% or less,

S: 0.02% or less,

optionally contains the freedom to choose

Mo: 0.20% or less,

V: 0.15% or less,

Ti: 0.050% or less,

Nb: 0.050% or less, and

B: 0.0030% or less

1 or more of the group consisting of,

The remaining part contains Fe and impurities;

The tissue contains pearlite, and the area ratio of the pearlite is more than 85%;

The average interlamellar spacing of the pearlite is 50nm-100nm,

In mass %, let the content of Si be [%Si], let the content of Cr contained in cementite in the pearlite be [%Crθ], let the ferrite in the pearlite be When the content of the Cr contained in the body is [%Crα], the [%Si], the [%Crθ] and the [%Crα] satisfy the following formula (1),

([%Crθ]/[%Crα])≥(2.0+[%Si]×10) (1).

2 . The steel wire rod according to claim 1 , wherein, as the chemical component, in % by mass, a group selected from

Mo: 0.02% to 0.20%,

V: 0.02% to 0.15%,

Ti: 0.002% to 0.050%,

Nb: 0.002% to 0.050%, and

B: 0.0003% to 0.0030%

1 or more of the group consisting of.

3 . The steel wire rod according to claim 1 , wherein the tensile strength TS of the steel wire rod is 1350 MPa or more, and the absolute value of the tensile strength TS of the steel wire rod is the The unit of the steel wire rod is 64 times or more the absolute value of the resistivity ρ in μΩ·cm.