CN108368583A - Micro Alloying mechanical part steel wire and Micro Alloying mechanical part - Google Patents

Micro Alloying mechanical part steel wire and Micro Alloying mechanical part Download PDF

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Publication number
CN108368583A
CN108368583A CN201780004566.3A CN201780004566A CN108368583A CN 108368583 A CN108368583 A CN 108368583A CN 201780004566 A CN201780004566 A CN 201780004566A CN 108368583 A CN108368583 A CN 108368583A
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China
Prior art keywords
steel wire
mechanical part
sections
less
pearlite
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Granted
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CN201780004566.3A
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CN108368583B (en
Inventor
小此木真
平上大辅
多田达诚
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Nippon Steel Corp
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Nippon Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor

Abstract

A kind of Micro Alloying mechanical part steel wire, meets following the description：Contained in terms of quality %：C：0.40~0.65%, Si：0.05~0.50%, Mn：0.20~1.00% and Al：0.005~0.050%, remainder contains Fe and impurity, wherein, metal structure contains the pearlite of (35 × [C%]+65) % or more, diameter is being set as D, the mean aspect ratio that depth on L sections is the pearlite block at 50 μm of positions is set as AR, in the case that the average block grain size that depth on C sections is the pearlite block at 50 μm of positions is set as GD, AR is 1.4 or more, (AR)/(depth on L sections is the mean aspect ratio of the pearlite block at the positions 0.25D) is 1.1 or more, GD is (15/AR) μm or less, (GD)/(depth on C sections is the average block grain size of the pearlite block at the positions 0.25D) is less than 1.0.

Description

Micro Alloying mechanical part steel wire and Micro Alloying mechanical part
Technical field
This application involves Micro Alloying mechanical part steel wire and Micro Alloying mechanical parts.
Background technology
In recent years, right from the viewpoint of lightweight or space saving in the fields such as the various machineries such as automobile, building The demand of high strength machine parts is improving.
But the increase of the intensity with high strength machine parts, especially in the tensile strength of high strength machine parts In the case of for 1100MPa or more, generation is become easy by the fracture caused by hydrogen embrittlement (that is, hydrogen embrittlement resistance becomes easy down Drop).
Method as the hydrogen embrittlement resistance for improving high strength machine parts, it is known that pearlite group is made in tissue Knit, strengthen the method for tissue by wire drawing, have proposed up to now a large amount of methods (for example, referring to patent document 1~ 11)。
For example, disclose the high-strength bolt that a kind of tensile strength is 1200MPa or more in patent document 11, be by Pearlitic structrure is made in tissue, then implements wire drawing.
In addition, Patent Document 3 discloses a kind of pearly-lustres for the high-strength bolt that tensile strength is 1200MPa or more The wire rod of body tissue.
Existing technical literature
Patent document
Patent document 1：Japanese Unexamined Patent Application 54-101743 bulletins
Patent document 2：Japanese Unexamined Patent Publication 11-315348 bulletins
Patent document 3：Japanese Unexamined Patent Publication 11-315349 bulletins
Patent document 4：Japanese Unexamined Patent Publication 2000-144306 bulletins
Patent document 5：Japanese Unexamined Patent Publication 2000-337332 bulletins
Patent document 6：Japanese Unexamined Patent Publication 2001-348618 bulletins
Patent document 7：Japanese Unexamined Patent Publication 2002-069579 bulletins
Patent document 8：Japanese Unexamined Patent Publication 2003-193183 bulletins
Patent document 9：Japanese Unexamined Patent Publication 2004-307929 bulletins
Patent document 10：Japanese Unexamined Patent Publication 2005-281860 bulletins
Patent document 11：Japanese Unexamined Patent Publication 2008-261027 bulletins
Invention content
Problems to be solved by the invention
It is the method for the high strength machine parts (such as high-strength bolt) of 1100MPa or more as manufacture tensile strength, Such as there are following methods：The steel wire shaping of the steel alloy of the alloying elements such as Cr, Mo, V will be added to after defined shape, to lead to Implementation Q-tempering is crossed to manufacture mechanical part.On the other hand, in order to reduce manufacturing cost, it is known to following technologies：It omits into Q-tempering after type, to by being quickly cooled down, precipitation strength etc. bys improve the wire rod of intensity and implement wire drawing, thus come Assign prescribed strength.It is (such as non-to be referred to as Micro Alloying mechanical part using the mechanical part (such as bolt) manufactured by the technology Quenched bolt).
The Micro Alloying mechanical part that tensile strength is 1100MPa or more can be by being 900MPa's or more to tensile strength Steel wire is cold worked to manufacture.
It is believed that：For example, (such as non-in the Micro Alloying mechanical part for carrying out wire drawing to pearlitic structrure and enhancing Quenched bolt) in, since pearlitic structrure can capture hydrogen at cementite and ferrite interface, hydrogen is to the invasion inside steel Inhibited, hydrogen embrittlement resistance improves.In Micro Alloying mechanical part (such as the Micro Alloying that tensile strength is 1100MPa or more Bolt) in, by the technology for carrying out wire drawing to pearlitic structrure so that hydrogen embrittlement resistance can also improve to some extent. But fully to improve hydrogen embrittlement resistance to be very difficult simply by virtue of the technology, it is desirable to have further to improve.
In addition, it is above-mentioned these in the prior art, with the steel for obtaining high strength machine parts by cold working The increase of the intensity of silk, especially in the case that the tensile strength of steel wire is 900MPa or more, steel wire is cold worked and Cold-workability when obtaining high strength machine parts is possible to decline.Therefore, improve hydrogen embrittlement resistance and cold-workability this two Person is very difficult.
Accordingly, just strong for obtaining the tension for the high strength machine parts that tensile strength is 1100MPa or more For degree is the steel wire of 900MPa or more, makes to manufacture cold-workability when Micro Alloying mechanical part by being cold worked and be made Hydrogen embrittlement resistance in the case of Micro Alloying mechanical part is able to take into account and be difficult sometimes.
Therefore, the project of the application is, provides the steel wire for being both tensile strength for 900MPa or more, and be by cold Processing is also excellent and in the case where Micro Alloying mechanical part is made to manufacture cold-workability when Micro Alloying mechanical part Hydrogen embrittlement resistance also excellent Micro Alloying mechanical part steel wire.
In addition, the project of the application is, providing can be manufactured and tension using the excellent steel wire of cold-workability Intensity and the excellent Micro Alloying mechanical part of hydrogen embrittlement resistance.
Means for solving the problems
Means for solving the problem includes scheme below.
<1>A kind of Micro Alloying mechanical part steel wire, chemical composition are contained in terms of quality %：
C：0.40~0.65%,
Si：0.05~0.50%,
Mn：0.20~1.00%,
Al：0.005~0.050%,
P：0~0.030%,
S：0~0.030%,
N：0~0.0050%,
Cr：0~1.00%,
Ti：0~0.050%,
Nb：0~0.050%,
V：0~0.10%,
B：0~0.0050%,
O：0~0.0030% and
Remainder：Fe and impurity,
Wherein, in the case where the quality % of C is set as [C%], metal structure by area occupation ratio be (35 × [C%]+ 65) pearlite of % or more and the remainder as at least one of pro-eutectoid ferrite and bainite are constituted,
Section that is parallel with the axis direction of steel wire and including central shaft is being set as L sections, by the axis direction with steel wire Vertical section is set as C sections, gauge of wire is set as to D, being 50 by the depth apart from steel wire surface on L sections μm position at the mean aspect ratio of pearlite block (Perlite block) that is measured be set as AR, by C sections away from In the case that depth from steel wire surface is set as GD by the average block grain size of the pearlite block measured at 50 μm of position, AR It is 1.4 or more, (AR)/(depth apart from steel wire surface on L sections is by the pearlite block that is measured at the position of 0.25D Mean aspect ratio) be 1.1 or more, GD be (15/AR) μm hereinafter, (GD)/(depth apart from steel wire surface on C sections Average block grain size by the pearlite block measured at the position of 0.25D) it is less than 1.0,
Tensile strength is 900~1500MPa.
<2>According to<1>The Micro Alloying mechanical part steel wire contains a kind in following elements in terms of quality % Or two or more：
Cr：More than 0% and for 1.00% or less,
Ti：More than 0% and for 0.050% or less,
Nb：More than 0% and for 0.050% or less,
V：More than 0% and for 0.10% or less and
B：More than 0% and it is 0.0050% or less.
<3>According to<1>Or<2>The Micro Alloying mechanical part steel wire, wherein the D is 3~30mm.
<4>A kind of Micro Alloying mechanical part, containing columned axle portion,
Its chemical composition is contained in terms of quality %：
C：0.40~0.65%,
Si：0.05~0.50%,
Mn：0.20~1.00%,
Al：0.005~0.050%,
P：0~0.030%,
S：0~0.030%,
N：0~0.0050%,
Cr：0~1.00%,
Ti：0~0.050%,
Nb：0~0.050%,
V：0~0.10%,
B：0~0.0050%,
O：0~0.0030% and
Remainder：Fe and impurity,
Wherein, in the case where the quality % of C is set as [C%], metal structure by area occupation ratio be (35 × [C%]+ 65) pearlite of % or more and the remainder as at least one of pro-eutectoid ferrite and bainite are constituted,
By it is parallel with the axis direction of columned axle portion and include the section of central shaft be set as L sections, will be with The section that the axis direction of the columned axle portion is vertical is set as C sections, is set as the diameter of the columned axle portion D, by the depth on the surface of columned axle portion described in the distance on L sections by the pearlite block that is measured at 50 μm of position Mean aspect ratio be set as AR, be 50 μm of position by the depth on the surface of columned axle portion described in the distance on C sections Set the pearlite block of place measurement average block grain size be set as GD in the case of, AR is 1.4 or more, (AR)/(on L sections Distance described in columned axle portion surface depth by the average length and width of the pearlite block measured at the position of 0.25D Than) be 1.1 or more, GD it is (15/AR) μm hereinafter, (GD)/(surface of columned axle portion described in the distance on C sections Depth is by the average block grain size of the pearlite block measured at the position of 0.25D) it is less than 1.0,
The tensile strength of the columned axle portion is 1100~1500MPa.
<5>According to<4>The Micro Alloying mechanical part, in terms of quality % containing a kind or 2 kinds in following elements with On：
Cr：More than 0% and for 1.00% or less,
Ti：More than 0% and for 0.050% or less,
Nb：More than 0% and for 0.050% or less,
V：More than 0% and for 0.10% or less and
B：More than 0% and it is 0.0050% or less.
<6>A kind of Micro Alloying mechanical part is<1>~<3>Any one of described in Micro Alloying mechanical part steel wire Cold working product, it includes columned axle portion, the tensile strength of the columned axle portion is 1100~1500MPa.
<7>According to<4>~<6>Any one of described in Micro Alloying mechanical part, be Micro Alloying bolt.
Invention effect
According to the application, can provide be both tensile strength be 900MPa or more steel wire, and be by be cold worked come Cold-workability when manufacturing Micro Alloying mechanical part is also excellent and resistance to hydrogen embrittlement in the case where Micro Alloying mechanical part is made Characteristic also excellent Micro Alloying mechanical part steel wire.
In addition, according to the application, can provide can be manufactured and tension is strong using the excellent steel wire of cold-workability Degree and the excellent Micro Alloying mechanical part of hydrogen embrittlement resistance.
Description of the drawings
Fig. 1 is the concept map of an example of the pearlite block on the L sections for indicate the steel wire of the application.
Specific implementation mode
It refers under the front and back recorded numerical value comprising "~" is used as in this specification, to use the numberical range that "~" indicates The range of limit value and upper limit value.
In this specification, " % " of the content of expression composition (element) refers to " quality % ".
In this specification, the content of C (carbon) is denoted as " C content " sometimes.Sometimes the content of other elements is also carried out same Sample marks.
In this specification, " process " this term is not only independent process, even if can not be carried out with other process In the case of clearly distinguishing, as long as the desired purpose of the process can be realized, then it is also included in this term.
(Micro Alloying mechanical part steel wire)
The Micro Alloying mechanical part of the application is with the chemical composition of steel wire (hereinafter also referred to as " steel wire ") in terms of quality % Contain：C：0.40~0.65%, Si：0.05~0.50%, Mn：0.20~1.00%, Al：0.005~0.050%, P：0~ 0.030%, S：0~0.030%, N：0~0.0050%, Cr：0~1.00%, Ti：0~0.050%, Nb：0~0.050%, V：0~0.10%, B：0~0.0050%, O：0~0.0030% and remainder：Fe and impurity,
Wherein, in the case where the quality % of C is set as [C%], metal structure by area occupation ratio be (35 × [C%]+ 65) pearlite of % or more and the remainder as at least one of pro-eutectoid ferrite and bainite are constituted,
Section that is parallel with the axis direction of steel wire and including central shaft is being set as L sections, by the axis direction with steel wire Vertical section is set as C sections, gauge of wire is set as to D, being 50 by the depth apart from steel wire surface on L sections μm position at the mean aspect ratio of pearlite block that is measured be set as AR, by the depth apart from steel wire surface on C sections In the case that degree is set as GD by the average block grain size of the pearlite block measured at 50 μm of position, AR is 1.4 or more, (AR)/(depth apart from steel wire surface on L sections is by the average length and width of the pearlite block measured at the position of 0.25D Than) be 1.1 or more, GD it is (15/AR) μm hereinafter, (GD)/(position that the depth apart from steel wire surface on C sections is 0.25D Set the average block grain size of the pearlite block of place measurement) it is less than 1.0,
Tensile strength is 900~1500MPa.
The steel wire of the application is both the steel wire that tensile strength is 900MPa or more, and manufactures Micro Alloying by being cold worked Cold-workability (hereinafter also referred to as " cold-workability ") when mechanical part is also excellent.
In turn, the steel wire of the application in the case where Micro Alloying mechanical part is made hydrogen embrittlement resistance (below also referred to as For " hydrogen embrittlement resistance ") it is excellent.In other words, it is cold worked by the steel wire to the application, it is special so as to manufacture resistance to hydrogen embrittlement The excellent Micro Alloying mechanical part of property.
In the steel wire of the application, above-mentioned chemical composition contributes to both cold-workability and hydrogen embrittlement resistance.For The details of chemical composition can be described below.
In general, such as the change of C content above-mentioned chemical composition low (specifically, C content is 0.65 mass % or less) Learning the steel wire of composition can be also improved by softening and ductility, and good cold-workability can be obtained.
But along with the reduction of C content, it is easy to generate the two-phase structure of pro-eutectoid ferrite and pearlite.Especially On the surface layer of wire rod, by decarburization so that C content is easy further to decline, it is easy to generate pro-eutectoid ferrite.In addition, in wire rod Surface layer be also easy bainite tissue since cooling velocity is big.With regard to the two-phase group of pro-eutectoid ferrite and pearlite Knit and bainite for, compared with pearlite, usual hydrogen embrittlement resistance is low.C content is being reduced (specifically, C is contained Amount is set as 0.65 mass % or less) in the case of, it becomes easy and generates the tissues such as pro-eutectoid ferrite, bainite, therefore machinery The hydrogen embrittlement resistance of the surface section of component (such as bolt) is lower.
Related this point, the metal structure of the steel wire of the application are the metal structures based on pearlite, in more detail and Speech, it is the metal structure of (35 × [C%]+65) % or more that the metal structure of the steel wire of the application, which is the area occupation ratio of pearlite,.Pearl Body of light tissue has the layer (being also referred to as sometimes below " cementite lamella ") being mainly mutually made of cementite and mainly by ferrite The layer (being also referred to as sometimes below " ferrite lamellae ") mutually constituted is formed by stepped construction.It is believed that：The stepped construction becomes To the resistance (hydrogen embrittlement resistance) of the development of crackle.Cold-workability and hydrogen embrittlement resistance can improve as a result,.
In this application, the area occupation ratio of pearlite depend on [C%] (i.e. C content) the reasons why be because of：It is in C content In the range of 0.40~0.65%, that there are C contents is lower, then easier generation pro-eutectoid ferrite and bainite and is more difficult to Generate the tendency of pearlite.
For the steel wire of the application, depth on L sections is flat by the pearlite block that is measured at 50 μm of position Equal length-width ratio (that is, " AR " in this specification) is 1.4 or more, and (AR)/(depth apart from steel wire surface on L sections Degree is by the mean aspect ratio of the pearlite block measured at the position of 0.25D) it is 1.1 or more.
In this specification, " position that depth is 50 μm " will be known as apart from the position that the depth of steel wire surface is 50 μm sometimes Or " surface layer ".In other words, " surface layer " in this specification refers to the position that the depth apart from steel wire surface is 50 μm.
In this specification, sometimes by apart from the depth of steel wire surface be 0.25D position (that is, the depth apart from steel wire surface Degree is 0.25 times of position of gauge of wire (i.e. D)) it is referred to as " depth is the position of 0.25D " or " 0.25D ".
In this specification, sometimes by (AR)/(position place that the depth apart from steel wire surface on L sections is 0.25D The mean aspect ratio of the pearlite block of measurement) it is referred to as " ratio (surface layer/0.25D) of length-width ratio " of pearlite block.
The ratio (surface layer/0.25D) of the length-width ratio of the steel wire of the application is 1.1 or more.That is, the L of the steel wire in the application On section, (i.e. depth is the position of 0.25D than the inside of steel wire for the pearlite block on the surface layer (position that i.e. depth is 50 μm) of steel wire Set) pearlite block be more stretched.
In addition, on the L sections of the steel wire of the application, the mean aspect ratio (i.e. AR) of the pearlite block on surface layer be 1.4 with On.
The steel wire of the application is by meeting these above-mentioned conditions so that hydrogen embrittlement resistance by cold working (that is, be made Hydrogen embrittlement resistance in the case of Micro Alloying mechanical part) it improves.Its reason be presently considered to be because：By making pearlite on surface layer Block extends so that the direction of the layer structure of the pearlitic structrure in surface layer becomes more uniformly, to become to coming from steel wire surface Hydrogen intrusion resistance and/or resistance as the development to crackle.Therefore, for the steel wire of the application, even if metal group It knits containing pro-eutectoid ferrite and bainite, hydrogen embrittlement resistance can also improve.
For the steel wire of the application, depth on C sections is flat by the pearlite block that is measured at 50 μm of position Equal block grain size (GD) is for (15/AR) μm hereinafter, and (GD)/(depth on C sections at the position of 0.25D by measuring The average block grain size of pearlite block) it is less than 1.0.
In this specification, sometimes by (GD)/(depth on C sections is by the pearlite block that is measured at the position of 0.25D Average block grain size) be referred to as " ratio (surface layer/0.25D) of block grain size " of pearlite block.
The ratio (surface layer/0.25D) of the block grain size of the pearlite block of the steel wire of the application is less than 1.0.That is, the application's On the C sections of steel wire, (i.e. depth is than the inside of steel wire for the pearlite block of the surface layer of steel wire (position that i.e. depth is 50 μm) The position of 0.25D) pearlite block be more micronized.
In addition, on the C sections of the steel wire of the application, the average block grain size (i.e. GD) of the pearlite block on surface layer reaches (15/ AR) μm or less.
The steel wire of the application is by meeting these above-mentioned conditions so that the cold-workability of steel wire improves, and resistance to hydrogen embrittlement is special Property (that is, in hydrogen embrittlement resistance in the case that Micro Alloying mechanical part is made in cold working) improve.
By meet above-mentioned condition so that the reasons why cold-workability of steel wire is improved be presently considered to be because：Pass through surface layer Pearlite block be fine (i.e. (15/AR) μm or less) so that the ductility raising of steel wire.
In addition, by meeting above-mentioned condition so that the reasons why hydrogen embrittlement resistance is improved is it is believed that pearlite with surface layer Block is fine related with the tendency in cyrystal boundary segregation with hydrogen.That is, be presently considered to be because：Since the pearlite block on surface layer is micro- Carefully so that the gross area of the crystal boundary on surface layer increases, as a result, the hydrogen capturing ability on surface layer is (that is, prevent hydrogen from invading into steel wire The ability in portion) it improves.
The tensile strength of the steel wire of the application is 900~1500MPa.
Tensile strength is that the steel wire (that is, Micro Alloying mechanical part steel wire) of the application of 900~1500MPa is suitable for leading to Cold working is crossed to manufacture the purposes for the Micro Alloying mechanical part that tensile strength is 1100~1500MPa.
As the cold working in the application, be not particularly limited, can enumerate cold forging make, roll forming, cutting, drawing Deng.
Cold working in the application can only be a kind of processing, can also be a variety of process (for example, cold forging is made and is rolled into Type).
In addition, the Micro Alloying mechanical part that above-mentioned tensile strength is 1100~1500MPa can also be by the application's Steel wire is cold worked and then is maintained to be manufactured within the temperature range of 100~400 DEG C.
The steel wire of the application meets above-mentioned condition due to based on pearlite, therefore is both that tensile strength is The steel wire of 900MPa or more, and it is also excellent come cold-workability when obtaining Micro Alloying mechanical part by being cold worked.
Relative to the steel wire of the application, tensile strength is 900MPa or more and with pro-eutectoid ferrite-pearlite two-phase The tendency that steel wire based on tissue has cold-workability low.
<Chemical composition>
In the following, being illustrated to the chemical composition of the steel wire of the application.
It should be noted that the chemical composition of the Micro Alloying mechanical part of aftermentioned the application also with the steel wire of the application Chemical composition is identical.
Hereinafter, the chemical composition of the steel wire of the application or Micro Alloying mechanical part is known as the " chemistry in the application sometimes Composition ".
·C：0.40~0.65%
C is to ensuring the element needed for tensile strength.
In the case where C content is less than 0.40%, it is difficult to obtain desired tensile strength.Therefore, the change in the application It is 0.40% or more, preferably 0.45% or more to learn the C content in composition.
On the other hand, in the case where C content is more than 0.65%, cold-workability can deteriorate.Therefore, the chemistry in the application C content in composition is 0.65% hereinafter, preferably 0.60% or less.
·Si：0.05~0.50%
Si is deoxidant element, while being also the element that tensile strength is improved by solution strengthening.
In the case where Si contents are less than 0.05%, additive effect will not fully show.Therefore, the chemical group in the application Si contents in are 0.05% or more, preferably 0.15% or more.
On the other hand, in the case where Si contents are more than 0.50%, additive effect reaches saturation, and extension when hot rolling Property deterioration and easy to produce flaw.Therefore, the Si contents in the chemical composition in the application are 0.50% hereinafter, preferably 0.30% or less.
·Mn：0.20~1.00%
Mn is the element for the tensile strength for improving the steel after pearlitic transformation.
In the case where Mn contents are less than 0.20%, additive effect will not fully show.Therefore, the chemical group in the application Mn contents in are 0.20% or more, preferably 0.40% or more.
On the other hand, in the case where Mn contents are more than 1.00%, additive effect reaches saturation, and the constant temperature phase of wire rod Phase transformation deadline when becoming processing is elongated.The phase transformation deadline is elongated can cause wire rod surface section pearlitic structrure face Product rate is less than (35 × [C%]+65) area %, and thus hydrogen embrittlement resistance and cold-workability are possible to deteriorate.In addition, addition effect The saturation of fruit can cause manufacturing cost to increase.Therefore, the Mn contents in the chemical composition in the application be 1.00% hereinafter, it is preferred that It is 0.80% or less.
·Al：0.005~0.050%
Al is deoxidant element, and is to form the element that the AlN that particle works is pricked as needle.AlN makes crystal grain grain refined, Thus cold-workability is improved.In addition, Al is that have the function of reducing solid solution N to inhibit dynamic strain aging and have to improve hydrogen resistance The element of the effect of crisp characteristic.
In the case where Al content is less than 0.005%, above-mentioned effect can not be obtained.Therefore, the chemical group in the application Al content in is 0.005% or more, preferably 0.020% or more.
In the case where Al content is more than 0.050%, above-mentioned effect reaches saturation, while the flaw is easy tod produce when hot rolling Defect.Therefore, the Al content in the chemical composition in the application is 0.050% hereinafter, preferably 0.040% or less.
·P：0~0.030%
P is the element for making hydrogen embrittlement resistance deteriorate in cyrystal boundary segregation and cold-workability being made to deteriorate.
In the case where P content is more than 0.030%, the deterioration of hydrogen embrittlement resistance and the deterioration of cold-workability become notable. Therefore, the P content in the chemical composition in the application is 0.030% hereinafter, preferably 0.015% or less.
Since the steel wire of the application need not contain P, the lower limiting value of P content is 0%.But it is manufactured into from reduction From the perspective of this (dephosphorization cost), P content can also be more than 0%, or 0.002% or more, or 0.005% More than.
·S：0~0.030%
S and P is again it is the element for making hydrogen embrittlement resistance deteriorate in cyrystal boundary segregation and cold-workability being made to deteriorate.
In the case where S contents are more than 0.030%, the deterioration of hydrogen embrittlement resistance and the deterioration of cold-workability become notable. Therefore, S contents are 0.030% hereinafter, preferably 0.015% hereinafter, more preferably 0.010% or less.
Since the steel wire of the application need not contain S, the lower limiting value of S contents is 0%.But it is manufactured into from reduction From the perspective of this (desulphurization cost), S contents can also be more than 0%, or 0.002% or more, or 0.005% More than.
·N：0~0.0050%
N is due to dynamic strain aging there is a possibility that the element that cold-workability deteriorates and then hydrogen embrittlement resistance is made also to deteriorate. In order to avoid above-mentioned such harmful effect, in the chemical composition in the application, N content is set as 0.0050% or less.N contains Amount preferably 0.0040% or less.
The lower limiting value of N content is 0%.But from the viewpoint of reducing manufacturing cost (denitrogenation cost), N content also may be used With more than 0%, or 0.0010% or more, or 0.0020% or more, or 0.0030% or more.
·Cr：0~1.00%
Cr is optional element.That is, the lower limiting value of the Cr contents in chemical composition in the application is 0%.
Cr is the element for the tensile strength for improving the steel after pearlitic transformation.From the viewpoint of obtaining the effect, Cr contains Amount preferably greater than 0%, more preferably 0.01% or more, further preferably 0.03% or more are still more preferably 0.05% More than, particularly preferably 0.10% or more.
On the other hand, in the case where Cr contents are more than 1.00%, generation martensite is become easy, cold-workability is thus made Deterioration.Therefore, the Cr contents in the chemical composition in the application be 1.00% hereinafter, preferably 0.70% hereinafter, more preferably 0.50% or less.
·Ti：0~0.050%
Ti is optional element.That is, the lower limiting value of the Ti contents in chemical composition in the application is 0%.
Ti is deoxidant element, and is to form TiN and have the function of reducing solid solution N to inhibit dynamic strain aging and tool It is improved the element of the effect of hydrogen embrittlement resistance.From the viewpoint of obtaining these above-mentioned effects, Ti contents are preferably greater than 0%, More preferably 0.005% or more, further preferably 0.015% or more.
On the other hand, in the case where Ti contents are more than 0.050%, above-mentioned effect reaches saturation, and hot rolling time-varying Flaw must be easy tod produce.Therefore, the Ti contents in the chemical composition in the application be 0.050% hereinafter, preferably 0.035% with Under.
·Nb：0~0.050%
Nb is optional element.That is, the lower limiting value of the Nb contents in chemical composition in the application is 0%.
Nb is to form NbN and have the function of reducing solid solution N to inhibit dynamic strain aging and have to improve resistance to hydrogen embrittlement spy The element of the effect of property.From the viewpoint of obtaining these above-mentioned effects, Nb contents are preferably greater than 0%, more preferably 0.005% More than, further preferably 0.015% or more.
On the other hand, in the case where Nb contents are more than 0.05%, above-mentioned effect reaches saturation, and becomes when hot rolling Easy to produce flaw.Therefore, the Nb contents in the chemical composition in the application be 0.050% hereinafter, preferably 0.035% with Under.
·V：0~0.10%
V is optional element.That is, the lower limiting value of the V content in chemical composition in the application is 0%.
V is to form VN and have the function of reducing solid solution N to inhibit dynamic strain aging and have to improve hydrogen embrittlement resistance Effect element.From the viewpoint of obtaining these above-mentioned effects, V content is preferably greater than 0%, more preferably 0.02% with On.
On the other hand, in the case where V content is more than 0.10%, above-mentioned effect reaches saturation, and becomes when hot rolling Easy to produce flaw.Therefore, the V content in the chemical composition in the application is 0.10% hereinafter, preferably 0.05% or less.
·B：0~0.0050%
B is optional element.That is, the lower limiting value of the B content in chemical composition in the application is 0%.
B inhibits grain boundary ferrite, crystal boundary bainite, has the effect of improving cold-workability and hydrogen embrittlement resistance, improves pearl The effect of tensile strength after body of light phase transformation.From the viewpoint of obtaining these above-mentioned effects, B content is preferably greater than 0%, more excellent It is selected as 0.0003% or more.
On the other hand, if B content is more than 0.0050%, above-mentioned effect reaches saturation.Therefore, the change in the application It is 0.0050% or less to learn the B content in composition.
From the viewpoint of the respective effect for obtaining above-mentioned optional element, the chemical composition in the application is with quality % Meter can also contain one kind or two or more in following elements：Cr：More than 0% and it is 1.00% or less, Ti：More than 0% and it is 0.050% or less, Nb：More than 0% and it is 0.050% or less, V：More than 0% and it is 0.10% or less and B：More than 0% and It is 0.0050% or less.
·O：0~0.0030%
O exists in steel wire in the form of the oxide of Al and Ti etc..
In the case where O content is more than 0.0030%, coarse oxide can be generated in steel, easy tos produce fatigue fracture. Therefore, the O content in the chemical composition in the application is 0.0030% hereinafter, preferably 0.0020% or less.
Since the steel wire of the application need not contain O, the lower limiting value of O content is 0%.But it is manufactured into from reduction From the perspective of this (deoxidation cost), O content can also be more than 0%, or 0.0002% or more, or 0.0005% or more.
Remainder：Fe and impurity
In chemical composition in this application, the remainder other than above-mentioned each element is Fe and impurity.
Here, impurity refers to ingredient contained in raw material or the mixed ingredient in the process of manufacture, and is not to have Meaning ground makes the ingredient contained in steel.
As impurity, all elements other than above-mentioned element can be enumerated.Element as impurity can only be a kind, Can also be two or more.
<Metal structure>
In the following, being illustrated to the metal structure of the steel wire of the application.
(area occupation ratio of pearlite)
In the case where the quality % of C is set as [C%], the metal structure of the steel wire of the application is (35 by area occupation ratio × [C%]+65) % or more pearlite and remainder structure as at least one of pro-eutectoid ferrite and bainite At.
Cold-workability and hydrogen embrittlement resistance can improve as a result,.
In the case that the area occupation ratio of pearlite in the metal structure of steel wire is less than (35 × [C%]+65) %, steel wire Intensity (tensile strength, hardness etc.) becomes uneven, therefore can be become easy when Micro Alloying mechanical part is cold worked It cracks (that is, cold-workability decline).
In addition, in the case that the area occupation ratio of the pearlite in the metal structure of steel wire is less than (35 × [C%]+65) %, In the Micro Alloying mechanical part obtained from the steel wire is cold worked, the area occupation ratio of the pearlite of metal structure can also become Less than (35 × [C%]+65) %.As a result, the hydrogen embrittlement resistance deterioration of Micro Alloying mechanical part.
From the viewpoint of further increasing cold-workability and hydrogen embrittlement resistance, the area occupation ratio of pearlite be preferably (35 × [C%]+70) % or more, more preferably (35 × [C%]+75) % or more.
From the viewpoint of manufacturing adaptability, the area occupation ratio of pearlite be preferably 99% hereinafter, more preferably 97% hereinafter, Further preferably 95% or less.
In the metal structure of the steel wire of the application, the specific preferred scope of the area occupation ratio of pearlite is although also depend on [C%], but preferably 80~99%, more preferably 83~97%, particularly preferably 85~95%.
Remainder in the metal structure of the steel wire of the application is at least one of pro-eutectoid ferrite and bainite.
In the case where remainder contains martensite, cold-workability and in the case where Micro Alloying mechanical part is made Hydrogen embrittlement resistance can decline.
In this specification, the area occupation ratio (%) of pearlite refers to the value found out according to following step.
First, the C sections of steel wire are etched using bitter taste alcohol, metal structure is made to display.
Then, from the position (that is, circle-shaped position) that the depth on the C sections after etching is 50 μm, circumferentially 4 observation positions are selected in direction every 90 °, and FE-SEM (Field Emission-Scanning are used to each observation position Electron Microscope) shoot the SEM photograph that multiplying power is 1000 times.
Equally, from the position (that is, circle-shaped position) that the depth on the C sections after etching is 0.25D, circumferentially 4 observation positions are selected in direction every 90 °, the SEM photograph for the use of FE-SEM shooting multiplying powers being 1000 times to each observation position.
In 8 obtained SEM photographs, tissue (pro-eutectoid ferrite, the bainite other than pearlite are gone out with visual label Deng), area occupation ratio (%) of the tissue other than pearlite relative to metal structure entirety is found out by image analysis.By by 100% subtracts the area occupation ratio (%) of the tissue other than obtained pearlite, to which the area occupation ratio (%) of pearlite can be obtained.
(AR)
The AR of the steel wire of the application is (that is, depth on L sections is by the flat of the pearlite block that is measured at 50 μm of position Equal length-width ratio) it is 1.4 or more.Thus hydrogen embrittlement characteristic can improve.Its reason considers as follows.As previously mentioned, pearlitic structrure has Cementite lamella and ferrite lamellae are formed by stepped construction, and the pearlite block of the elongation in surface layer is (that is, AR is 1.4 or more Pearlite block) pearlitic structrure layer structure direction become more uniformly.It is believed that：The layer structure of the homogenization at For the resistance invaded the hydrogen from steel wire surface and/or as the resistance of the development to crackle.
In the case where the AR of steel wire is less than 1.4, the AR of Micro Alloying mechanical part obtained from steel wire is cold worked Also 1.4 are got lower than.In the case, due to be difficult to obtain said effect (become the resistance that hydrogen is invaded effect and/or at For the effect of the resistance of the development to crackle), therefore the hydrogen embrittlement resistance of Micro Alloying mechanical part will not improve.
From the viewpoint of further increasing hydrogen embrittlement resistance, AR is preferably 1.5 or more, and more preferably 1.6 or more.
From the viewpoint of the manufacture adaptability of steel wire, AR is preferably 2.5 hereinafter, more preferably 2.0 or less.
In this specification, pearlite block refers to：From using EBSD (electron backscatter diffraction, electron back Scattering diffraction) from the point of view of ferritic crystal orientation figure obtained from method, misorientation is within 15 degree The organization unit of the consistent pearlite of ferritic orientation.That is, the boundary that above-mentioned misorientation reaches 15 ° or more is pearlite block Block crystal boundary.
In this specification, AR refers to the value measured according to following step.
First, from the straight line for the position that the depth on the L sections for indicating steel wire is 50 μm, 4 sights are selected every 2.0mm Position is examined, obtains that the depth direction centered on each observation position is 50 μm and axis direction is 250 μ respectively using EBSD devices Ferritic crystal orientation figure in the region of m.
In obtained all 4 crystal orientation figures, from the pearly-lustre for indicating that depth is crossed by the straight line of 50 μm of position In the group of body block, 10 pearlite blocks are selected successively from the maximum pearlite BOB(beginning of block) of equivalent circle diameter.
Then, the respective length-width ratio for finding out selected 10 pearlite blocks, by the length-width ratio of 10 pearlite blocks The average value of (that is, 10 values) is set as AR (that is, depth on L sections is by the pearlite block that is measured at 50 μm of position Mean aspect ratio).
In this specification, the length-width ratio of pearlite block refer to value obtained from major diameter divided by minor axis with pearlite block (i.e. Major diameter/minor axis).Here, the major diameter of pearlite block refers to the maximum length of pearlite block, and the minor axis of pearlite block refers to and major diameter The maximum value of the length in the orthogonal direction in direction.
Fig. 1 is the concept map of an example of the pearlite block on the L sections for the steel wire for indicating the example of the application.
In Fig. 1, do not illustrate only the crystal boundary of pearlite block, also illustrate the pearlite block major diameter (Major axis) and Minor axis (Minor axis).
The shape of pearlite block can be such multilateral shape shown in Fig. 1, can also be elliptical shape, can also be Shape (such as indefinite shape) other than multilateral shape and elliptical shape.
In short, as long as pearlite block AR is 1.4 or more, there is no particular restriction for shape.
(ratio (surface layer/0.25D) of length-width ratio)
The length-width ratio of the steel wire of the application ratio (surface layer/0.25D) (that is, (AR)/(depth on L sections is The mean aspect ratio of the pearlite block measured at the position of 0.25D)) it is 1.1 or more.
Ratio (surface layer/0.25D) by the length-width ratio of the steel wire of the application is 1.1 or more, to as previously mentioned, hydrogen resistance Crisp characteristic can improve.Its reason be presently considered to be because：In the stratiform for the pearlite pearlitic structrure in the block that surface layer has been stretched The direction of structure is more homogenized, the layer structure become to from steel wire surface hydrogen intrusion resistance and/or as pair The resistance of the development of crackle.
In addition, the ratio (surface layer/0.25D) of the length-width ratio by the steel wire of the application is 1.1 or more so that in deformed set In the surface layer of steel wire, therefore hydrogen embrittlement resistance can be effectively improved.
If the ratio (surface layer/0.25D) of length-width ratio is less than 1.1, the deformation for improving the surface layer of steel wire is not only needed, also It needs to improve the deformation inside steel wire, it is therefore possible to can not effectively improve the productivity of hydrogen embrittlement resistance, steel wire to be possible to It can decline.
From the viewpoint of improving hydrogen embrittlement resistance, the ratio (surface layer/0.25D) of length-width ratio is preferably 1.2 or more.
From the viewpoint of the manufacture adaptability of steel wire, the ratio (surface layer/0.25D) of length-width ratio is preferably 2.0 hereinafter, more Preferably 1.8 hereinafter, particularly preferably 1.6 or less.
In this specification, the depth on L sections is changed to from the position that the depth on L sections is 50 μm in addition to position will be observed Degree is other than the position of 0.25D, and the depth on L sections is by the average length and width of the pearlite block measured at the position of 0.25D Than being measured by method same as the assay method of AR above-mentioned.
(GD)
The GD of the steel wire of the application is (that is, depth on C sections is by the flat of the pearlite block that is measured at 50 μm of position Equal block grain size) it is (15/AR) μm or less.When by pearlite block being fine (that is, GD be (15/AR) μm following), thus as above Described, cold-workability and hydrogen embrittlement resistance can improve.
Its reason considers as described below.Pearlite block in the surface layer of steel wire is coarsening (that is, pearly-lustre In the case that the average block grain size of body block is more than (15/AR) μm), the ductility of steel wire can be lower, thus the cold-workability of steel wire It can decline.In turn, the block grain size of the pearlite block on the surface layer of mechanical part obtained from which being cold worked occurs thick Bigization.In pearlite block crystal boundary, there are the tendencies that hydrogen is segregated.Pearlite block on the surface layer of steel wire is coarsening situation Under, since the gross area of the block crystal boundary of pearlite block is reduced, the hydrogen capturing ability on surface layer is (that is, prevent hydrogen from invading into wire rod Internal ability) it reduces.Thus, it is believed that：In the case that surface layer pearlite block be it is coarsening, hydrogen embrittlement resistance can under Drop.
From the viewpoint of further increasing cold-workability and hydrogen embrittlement resistance, GD is preferably 11.0 μm hereinafter, more preferably It is 10.0 μm or less.
From the viewpoint of the manufacture adaptability of steel wire, GD is preferably 7.0 μm or more, more preferably 8.0 μm or more.
In the present specification, GD refers to the value measured according to following step.
First, indicate steel wire C sections on depth be 50 μm position circumference on, circumferentially every 45 ° are selected 8 observation positions, obtain the region of 50 μm of 50 μ m centered on each observation position respectively using EBSD devices In ferritic crystal orientation figure.
The equivalent circle diameter of whole pearlite block contained in 8 crystal orientation figures of obtained whole is measured respectively. The average value of obtained measured value is set as GD (that is, depth on C sections is by the pearlite that is measured at 50 μm of position The average block grain size of block).
(ratio (surface layer/0.25D) of grain size)
The grain size of the steel wire of the application ratio (surface layer/0.25D) (that is, (GD)/(depth on C sections is 0.25D Position at the average block grain size of pearlite block that is measured)) be less than 1.0.
It is less than 1.0 by the ratio (GD/0.25D) of the grain size of the steel wire of the application so that cold-workability and resistance to hydrogen embrittlement are special Property improve.
From the viewpoint of further increasing cold-workability and hydrogen embrittlement resistance, the ratio (GD/0.25D) of grain size is preferably 0.98 hereinafter, more preferably 0.96 hereinafter, particularly preferably 0.94 or less.
From the viewpoint of the manufacture adaptability of steel wire, the ratio (GD/0.25D) of grain size is preferably 0.80 or more, more excellent It is selected as 0.85 or more, particularly preferably 0.90 or more.
In this specification, the depth on C sections is changed to from the position that the depth on C sections is 50 μm in addition to position will be observed Degree is other than the position of 0.25D, and the depth on C sections is by the average block grain of the pearlite block measured at the position of 0.25D Diameter is measured by method same as the assay method of above-mentioned GD.
Tensile strength (the Tensile Strength of the steel wire of the application；TS) it is 900~1500MPa.
TS by the steel wire of the application is 900MPa or more, to easily fabricated by the steel wire is cold worked TS is the Micro Alloying mechanical part of 1100MPa or more.
In addition, for previous steel wire, if the TS of steel wire is 900MPa or more, cold-workability has inclining for decline To.
But for the steel wire of the application, by with above-mentioned chemical composition and metal structure so that it is both TS For the steel wire of 900MPa or more, and cold-workability is also excellent.
In addition, being 1500MPa or less by the TS of the steel wire of the application so that the manufacture adaptability and cold-workability of steel wire It is excellent.
In this specification, the tensile strength (TS) of steel wire and the tensile strength (TS) of Micro Alloying mechanical part all refer to using The 9A test films of JIS Z 2201 (2011) are measured according to the test method described in JIS Z 2201 (2011) Value.
From the viewpoint of the manufacture adaptability and cold-workability that further increase steel wire, the TS of the steel wire of the application is preferred For 900~1300MPa, more preferably 900~1200MPa.
In the steel wire of the application, D (that is, gauge of wire) is preferably 3~30mm, more preferably 5~25mm, particularly preferably For 5~20mm.
From the viewpoint of cold-workability, the limited compression rate of the steel wire of the application is preferably 75% or more.Limited compression Shown in the assay method of rate embodiment as be described hereinafter.
One example of the method for the steel wire as manufacture the application, can enumerate preparation method A below.
Preparation method A is included the following process：
By that there will be the heating steel billet of the chemical composition in the application to 1000~1150 DEG C, finishing temperature is set as 800~950 DEG C are implemented hot rolling, process to obtain wire rod；
By the way that temperature is impregnated 50 seconds or more for 800~950 DEG C of above-mentioned wire rod in 400~550 DEG C of molten salt bath, Process to carry out constant temperature phase transformation processing；
By the process of the processed wire water-cooled of constant temperature phase transformation to 300 DEG C of temperature below；With
By the wire drawing for the wire rod after water cooling implementing that total contraction percentage of area is made to reach 15~25%, to obtain steel The process of silk.
The chemical composition of steel wire (object) as obtained from preparation method A can be considered and the steel billet (raw material) in preparation method A Chemical composition is identical.The reason for this is that because：Above-mentioned hot rolling, above-mentioned constant temperature phase transformation processing, above-mentioned water cooling and above-mentioned wire drawing are all The chemical composition of steel will not be had an impact.
Preparation method A is by the process of the process and above-mentioned water cooling that are handled containing above-mentioned constant temperature phase transformation, to easy to manufacture pearly-lustre The area occupation ratio and remainder of body meet the steel wire of the application of above-mentioned condition respectively.
For example, passing through the dip time being impregnated in the process that above-mentioned constant temperature phase transformation is handled, by wire rod in molten salt bath It it is 50 seconds or more so that the area occupation ratio and remainder of pearlite are easy to meet above-mentioned condition respectively.
The upper limit of dip time is not particularly limited.From the viewpoint of the productivity of steel wire, dip time is preferably 100 Second is hereinafter, more preferably 80 seconds or less.
In addition, by obtaining the process of above-mentioned steel (that is, the process comprising wire drawing；It is also referred to as that " wire drawing adds below Work process ") in, total contraction percentage of area be 15% or more, to easy to manufacture tensile strength be 900MPa or more steel.
In addition, by wire drawing process, total contraction percentage of area be 25% hereinafter, to which easy to manufacture AR is 1.4 Steel that above, the ratio (surface layer/0.25D) of length-width ratio is 1.1 or more (that is, compared with the pearlite block inside steel, steel The steel that the pearlite block on surface layer has been stretched).
Wire drawing process can only include the process of a wire drawing, can also be comprising multiple wire drawing Process.
That is, total contraction percentage of area 15~25% in wire drawing process can be realized by a wire drawing, It can be realized by multiple wire drawing.
In the case where wire drawing process only includes a wire drawing, as the drawing-die used in wire drawing, It is preferable to use the drawing-die that Drawing cone half-angle is more than 10 °.As a result, the ratio (surface layer/0.25D) of easy to manufacture length-width ratio be 1.1 with On steel.
In addition, in the case where wire drawing process includes multiple wire drawing, the preferred section shrinkage in final passage Rate reach 10% it is below under the conditions of carry out multiple wire drawing.The ratio (surface layer/0.25D) of easy to manufacture length-width ratio as a result, For 1.1 or more steel.
The contraction percentage of area of final passage in the case where wire drawing process includes multiple wire drawing is more preferably 5 ~10%, further preferably 5~9%, particularly preferably 5~8%.
The steel wire of the application particularly suitable as manufacture containing tensile strength be 1100~1500MPa it is columned The steel wire of the Micro Alloying mechanical part of axle portion.
That is, be cold worked by the steel wire to the application (and 100~400 are preferably maintained at after cold working DEG C), to which easy to manufacture contains the Micro Alloying mechanical part for the columned axle portion that tensile strength is 1100~1500MPa.
Here, be cold worked by the steel wire to the application (and preferably it is maintained at 100 after cold working~ 400 DEG C) obtained from the chemical composition of Micro Alloying mechanical part can be considered identical as the chemical composition of the steel wire of the application.It is managed By being because：Cold working and heat treatment will not have an impact the chemical composition of steel.
In addition, be cold worked by the steel wire to the application (and implement 100~400 after cold working as needed DEG C heat treatment) obtained from the metal structure of Micro Alloying mechanical part can be considered the metal structure phase with the steel wire of the application Together.The reason for this is that because：The amount of cold working for obtaining the Micro Alloying mechanical part with columned axle portion is small.
(Micro Alloying mechanical part)
Hereinafter, the 1st embodiment to the Micro Alloying mechanical part (hereinafter also referred to as " mechanical part ") of the application and 2nd embodiment illustrates.
The mechanical part of the 1st embodiment of the application includes columned axle portion,
Chemical composition is the chemical composition in above-mentioned the application,
In the case where the quality % of C is set as [C%], metal structure by area occupation ratio be (35 × [C%]+65) % with On pearlite and as at least one of pro-eutectoid ferrite and bainite remainder constitute,
Section that is parallel with the axis direction of columned axle portion and including central shaft is set as L sections, will be with cylinder The section that the axis direction of the axle portion of shape is vertical is set as C sections, the diameter of columned axle portion is set as to D, will be on L sections The depth on surface of the columned axle portion of distance set by the mean aspect ratio of pearlite block measured at 50 μm of position By AR, the pearlite block that will be measured at position that the depth on the surface of the columned axle portion of distance on C sections is 50 μm Average block grain size be set as GD in the case of, AR is 1.4 or more, (AR)/(the columned axle portion of distance on L sections The depth on surface is by the mean aspect ratio of the pearlite block measured at the position of 0.25D) be 1.1 or more, GD be (15/AR) μm Hereinafter, (GD)/(depth on the surface of the columned axle portion of distance on C sections is by the pearly-lustre that is measured at the position of 0.25D The average block grain size of body block) it is less than 1.0,
The tensile strength (TS) of columned axle portion is 1100~1500MPa.
The metal structure of chemical composition and columned axle portion in the mechanical part of 1st embodiment is (that is, pearly-lustre is honorable Product rate, the ratio (surface layer/0.25D) of AR, the ratio (surface layer/0.25D) of length-width ratio, GD and average block grain size.It is same as below.) Respectively in the steel wire of the application chemical composition and metal structure it is identical.
Therefore, the hydrogen embrittlement resistance of the mechanical part of the 1st embodiment is excellent.
The mechanical part of 1st embodiment can be come using the excellent steel wire of cold-workability (for example, steel wire of the application) Manufacture.
The preferred configuration of the metal structure of chemical composition and columned axle portion in the mechanical part of 1st embodiment point It is not identical as the preferred configuration of chemical composition and metal structure in the steel wire of the application.
The mechanical part of the 2nd embodiment of the application is the cold working product of the steel wire of the application (that is, by the application Steel wire be cold worked obtained from mechanical part), the tensile strength of columned axle portion is 1100~1500MPa.
Therefore, the hydrogen embrittlement resistance of the mechanical part of the 2nd embodiment is excellent.
The preferred configuration of the metal structure of chemical composition and columned axle portion in the mechanical part of 2nd embodiment point It is not identical as the preferred configuration of chemical composition and metal structure in the steel wire of the application.
In the mechanical part of the application, the 1st embodiment and the 2nd embodiment can also have repeating part.
That is, the mechanical part for not only meeting any one of the 1st embodiment and the 2nd embodiment is included in the application Mechanical part in the range of, meet the mechanical part of both the 1st embodiment and the 2nd embodiment and be also included in this certainly In the range of the mechanical part of application.
As the mechanical part of the application, as long as the Micro Alloying mechanical part comprising columned axle portion, then have no spy It does not limit, but wherein particularly preferred Micro Alloying bolt.
One example of the method for the mechanical part as manufacture the application, can enumerate preparation method X below.
Preparation method X includes the process being cold worked by the steel wire to the application to obtain mechanical part.
Preparation method X, which is preferably comprised, is maintained at the mechanical part as obtained from cold working within the temperature range of 100~400 DEG C Process (following also referred to as " to keep process ").
By comprising keep process, to be more prone to manufacture tensile strength be 1100~1500MPa mechanical part.
It is 100~400 DEG C to keep the holding temperature in process, preferably 200~400 DEG C, more preferably 300~400 DEG C.
It is preferably 10 to be kept for the retention time (that is, time by mechanical part holding within the said temperature range) in process ~120 minutes, more preferably 10~60 minutes.
The Micro Alloying mechanical part steel wire and Micro Alloying mechanical part of the application discussed above can be used in vapour In the various machineries such as vehicle, building etc..
Embodiment
Embodiments herein described below, but the application embodiment not limited to the following.
(level (condition) 1~28)
<The manufacture of steel wire>
Using the steel billet (billet) of chemical composition shown in table 1, the steel wire of diameter (D) shown in table 3 has been manufactured.
In the chemical composition of each steel grade in table 1, the remainder other than element shown in table 1 is Fe and impurity.
For level 1~6,8~9,11~13,15~24 and 27~28, by implementing item shown in table 2 successively to steel billet Hot rolling, constant temperature phase transformation processing, water cooling and the wire drawing of part, to obtain diameter (D) steel wire as shown in table 3.
For level 14,25 and 26, by the hot rolling of condition shown in steel billet implementation table 2 then implement successively it is air-cooled, Heating temperature is patenting under conditions of reheating, the lead bath temperature at 950 DEG C are 580 DEG C and natural cooling and then real The wire drawing for applying condition shown in table 2, to obtain diameter (D) steel wire as shown in table 3.
For level 7 and 10, by implementing the hot rolling of condition shown in table 2 to steel billet and then carrying out air-cooled and then implementation The wire drawing of condition shown in table 2, to obtain diameter (D) steel wire as shown in table 3.
<The measurement of steel wire>
The steel wire of each level is carried out respectively by above-mentioned method：The measurement of the area occupation ratio of pearlite, remainder Confirmation, AR (that is, mean aspect ratio of the pearlite block at the position that depth on L sections is 50 μm) measurement, length and width Ratio ratio (surface layer/0.25D) (that is, (AR)/(depth on L sections is by the pearlite block that is measured at the position of 0.25D Mean aspect ratio)) measure, GD (that is, average block grain size of the pearlite block at the position that depth on C sections is 50 μm) Measurement, the ratio of grain size (surface layer/0.25D) (that is, (GD)/(depth on C sections at the position of 0.25D by measuring The average block grain size of pearlite block)) measurement and tensile strength (TS) measurement.
Each measurement result is shown in Table 3.
<The cold-workability (measurement of limited compression rate) of steel wire>
To the steel wire of each level, by measuring following limited compression rates, to have rated cold-workability.
First, by being machined to steel wire, to make a diameter of D (that is, gauge of wire), length has been The sample of 1.5 × D.
Two end faces of obtained sample are fettered using a pair of of mold.As a pair of of mold, use respectively In the mold with the slot with concentric circles on the contact surface of sample end face.In this state, sample is carried out along its length Compression.It is made various changes by the compression ratio to the sample in the compression to test, so as to find out not will produce The maximum compression ratio of the crackle of sample.
The maximum compression ratio that the crackle of sample will not be generated is set as limited compression rate (%).
As a result, the situation that limited compression rate is 70% or more is judged as that cold-workability is good (G), by limited compression The case where rate is less than 70% is judged as that cold-workability is bad (NG).
Above result is shown in Table 3.
<The manufacture of mechanical part>
(cold forging is made) is cold worked by the steel wire to each level, to be processed into the shape of flanged bolt.It is logical It crosses the steel wire heating after processing to 350 DEG C and is kept for 30 minutes at such a temperature, to obtain as the non-of mechanical part Quenched bolt.
<The measurement of the tensile strength (TS) of mechanical part>
The TS of the axle portion of obtained mechanical part (Micro Alloying bolt) is determined using above-mentioned assay method.
As a result it is shown in Table 3.
<The evaluation of the hydrogen embrittlement resistance of mechanical part>
Hydrogen embrittlement resistance is determined using the following method to obtained mechanical part (Micro Alloying bolt).
First, it is flushed with hydrogen by carrying out electrolysis to mechanical part, the diffusible hydrogen for making mechanical part contain 0.5ppm.
Then, hydrogen is discharged into from mechanical part in air in testing in order to prevent, and plating Cd is implemented to sample.
Then, in an atmosphere, 90% load for applying the maximum tension load of the mechanical part to mechanical part, at this It is kept for 100 hours or more under state.
It, will be through as a result, not there is a situation where being broken to be judged as that hydrogen embrittlement resistance is good (G) when will pass through 100 hours The case where fracture has occurred when spending 100 hours is judged as that hydrogen embrittlement resistance is bad (NG).
Above result is shown in Table 3.
Table 1
Table 2
Table 3
The explanation-of table 3
In remainder tissue column, F and B refer respectively to pro-eutectoid ferrite and bainite.
As shown in table 3, with the chemical composition in the application, pearlite area occupation ratio be (35 × [C%]+65) % or more, The ratio that remainder is organized as at least one of pro-eutectoid ferrite (F) and bainite (B), AR is 1.4 or more, length-width ratio (surface layer/0.25D) be 1.1 or more, GD be (15/AR) μm or less, the ratio (GD/0.25D) of grain size less than 1.0, TS be 900~ The steel wire of each level of the embodiment of 1500MPa is both the steel wire that TS is 900MPa or more, and cold-workability is also excellent, is made Hydrogen embrittlement resistance in the case of mechanical part is also excellent.
It is 1100MPa or more so as to manufacture TS in addition, being cold worked by the steel wire of each level to embodiment Mechanical part.
Relative to embodiment, level 7 of the pearlite area occupation ratio less than (35 × [C%]+65) % and 10 (they being comparative example) Steel wire the hydrogen embrittlement resistance being made in the case of mechanical part it is poor.
In addition, the case where mechanical part is made of steel wire of levels 3,5,12 and 27 (be comparative example) of the AR less than 1.4 Under hydrogen embrittlement resistance it is poor.
In addition, the steel of level 9,21,22 and 27 (be comparative example) of the ratio (surface layer/0.25D) of length-width ratio less than 1.1 The hydrogen embrittlement resistance of silk being made in the case of mechanical part is poor.
In addition, GD be more than the level 14 of (15/AR) μm and the steel wire of 25 (they being comparative example) and steel wire cold-workability it is poor.
In addition, the steel of the steel wire of level 14 and 26 (being comparative example) that the ratio (GD/0.25D) of grain size is 1.0 or more Silk cold-workability is poor.
In addition, TS less than 900MPa level 23 and 24 (they being comparative example) and steel wire cannot manufacture TS be 1100MPa with On mechanical part.
The undesirable steel wire of cold-workability (limited compression rate is less than 70%) processes the generation of crackle when manufacturing mechanical part Frequency is high.In turn, using the size of the mechanical part manufactured by the undesirable steel wire of cold-workability (limited compression rate is less than 70%) Low precision.
The entire disclosure of Japanese patent application 2016-008708 by referring to and be introduced into this specification.
All documents, patent application and technical standard described in this specification with it is specific and respectively describe " each Document, patent application and technical standard by referring to and be introduced into " the case where to same extent by referring to and be introduced in this In specification.

Claims (7)

1. a kind of Micro Alloying mechanical part steel wire, chemical composition are contained in terms of quality %：
C：0.40~0.65%,
Si：0.05~0.50%,
Mn：0.20~1.00%,
Al：0.005~0.050%,
P：0~0.030%,
S：0~0.030%,
N：0~0.0050%,
Cr：0~1.00%,
Ti：0~0.050%,
Nb：0~0.050%,
V：0~0.10%,
B：0~0.0050%,
O：0~0.0030% and
Remainder：Fe and impurity,
Wherein, in the case where the quality % of C is set as [C%], metal structure is (35 × [C%]+65) % by area occupation ratio Above pearlite and the remainder as at least one of pro-eutectoid ferrite and bainite are constituted,
Section that is parallel with the axis direction of steel wire and including central shaft is set as L sections, will be vertical with the axis direction of steel wire Section be set as C sections, gauge of wire be set as to D, being 50 μm by the depth apart from steel wire surface on L sections The mean aspect ratio of the pearlite block measured at position is set as AR, will be apart from the depth of steel wire surface on C sections In the case that the average block grain size of the pearlite block measured at 50 μm of position is set as GD, AR is 1.4 or more, (AR)/( The depth apart from steel wire surface on L sections is by the mean aspect ratio of the pearlite block measured at the position of 0.25D) it is 1.1 More than, GD for (15/AR) μm hereinafter, (GD)/(depth apart from steel wire surface on C sections at the position of 0.25D by surveying The average block grain size of fixed pearlite block) it is less than 1.0,
Tensile strength is 900~1500MPa.
2. Micro Alloying mechanical part steel wire according to claim 1 contains a kind in following elements in terms of quality % Or two or more：
Cr：More than 0% and for 1.00% or less,
Ti：More than 0% and for 0.050% or less,
Nb：More than 0% and for 0.050% or less,
V：More than 0% and for 0.10% or less and
B：More than 0% and it is 0.0050% or less.
3. Micro Alloying mechanical part steel wire according to claim 1 or 2, wherein the D is 3~30mm.
4. a kind of Micro Alloying mechanical part, containing columned axle portion,
Its chemical composition is contained in terms of quality %：
C：0.40~0.65%,
Si：0.05~0.50%,
Mn：0.20~1.00%,
Al：0.005~0.050%,
P：0~0.030%,
S：0~0.030%,
N：0~0.0050%,
Cr：0~1.00%,
Ti：0~0.050%,
Nb：0~0.050%,
V：0~0.10%,
B：0~0.0050%,
O：0~0.0030% and
Remainder：Fe and impurity,
Wherein, in the case where the quality % of C is set as [C%], metal structure is (35 × [C%]+65) % by area occupation ratio Above pearlite and the remainder as at least one of pro-eutectoid ferrite and bainite are constituted,
By it is parallel with the axis direction of columned axle portion and include the section of central shaft be set as L sections, will with it is described The section that the axis direction of columned axle portion is vertical is set as C sections, the diameter of the columned axle portion is set as to D, inciting somebody to action The depth on the surface of columned axle portion described in distance on L sections is by the flat of the pearlite block that is measured at 50 μm of position At the position that equal length-width ratio is set as AR, is 50 μm by the depth on the surface of columned axle portion described in the distance on C sections In the case that the average block grain size of the pearlite block measured is set as GD, AR be 1.4 or more, (AR)/(on L sections away from Mean aspect ratio of the depth on the surface from the columned axle portion by the pearlite block measured at the position of 0.25D) be 1.1 or more, GD are (15/AR) μm hereinafter, (GD)/and (depth on the surface of columned axle portion described in the distance on C sections is The average block grain size of the pearlite block measured at the position of 0.25D) it is less than 1.0,
The tensile strength of the columned axle portion is 1100~1500MPa.
5. Micro Alloying mechanical part according to claim 4 contains a kind or 2 kinds in following elements in terms of quality % More than：
Cr：More than 0% and for 1.00% or less,
Ti：More than 0% and for 0.050% or less,
Nb：More than 0% and for 0.050% or less,
V：More than 0% and for 0.10% or less and
B：More than 0% and it is 0.0050% or less.
6. a kind of Micro Alloying mechanical part is Micro Alloying mechanical part steel wire according to any one of claims 1 to 3 Cold working product, it includes columned axle portion, the tensile strength of the columned axle portion is 1100~1500MPa.
7. the Micro Alloying mechanical part according to any one of claim 4~6 is Micro Alloying bolt.
CN201780004566.3A 2016-01-20 2017-01-20 Steel wire for non-heat-treated machine part and non-heat-treated machine part Active CN108368583B (en)

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WO2017126695A1 (en) 2017-07-27
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KR102037089B1 (en) 2019-10-29
KR20180082553A (en) 2018-07-18

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