CN102782173A - High-strength seamless steel pipe for mechanical structure which has excellent toughness, and process for production of same - Google Patents
High-strength seamless steel pipe for mechanical structure which has excellent toughness, and process for production of same Download PDFInfo
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- CN102782173A CN102782173A CN2011800123186A CN201180012318A CN102782173A CN 102782173 A CN102782173 A CN 102782173A CN 2011800123186 A CN2011800123186 A CN 2011800123186A CN 201180012318 A CN201180012318 A CN 201180012318A CN 102782173 A CN102782173 A CN 102782173A
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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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C23/00—Extruding metal; Impact extrusion
- B21C23/002—Extruding materials of special alloys so far as the composition of the alloy requires or permits special extruding methods of sequences
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- 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
- C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
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- 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
- C21D9/02—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for springs
-
- 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
- C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
- C21D9/085—Cooling or quenching
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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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
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- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
Disclosed is a seamless steel pipe which can be produced at low cost, is as accelerate-cooled, and has high strength and high toughness. The seamless steel pipe is characterized by comprising, in mass%, 0.03-0.02% of C, 0.01-0.50% of Si, 0.80-3.00% of Mn, 0.020% or less of P, 0.0080% or less of S, 0.050% or less of Al, 0.0080% or less of N and 0.0050% or less, with the remainder being Fe and unavoidable impurities. The seamless steel pipe is also characterized in that ss (= 2.7C+0.4Si+Mn+0.45Ni+Mo (wherein each symbol represents the content [mass%] of an element represented by the symbol)) is 2.50-4.00, Pcm (= C+Si/30+(Mn+Cu)/20+Ni/60+Mo/15+V/10) is 0.15-0.30, the structure is composed of fresh martensite, and prior austenite has an average particle diameter of 50-200 [mu]m.
Description
Technical field
The present invention relates to be particularly suitable for cylinder (cylinder), lining (sleeve, bush), the machinery of the structural member of cantilever (boom) etc. and axle etc. is with the weldless steel tube and the method for manufacture thereof of member.
Background technology
Being used for the majority of the mechanical part of automobile and industrial machine etc., is with after the shape that bar steel forges, cut forms regulation, through modified thermal treatment, gives the mechanical property (mechanical property) of regulation.
In recent years, in order to reduce the manufacturing cost of parts, and for the lightweight of machinery etc., be that blank is made the hollow shape parts with the steel pipe that has the mechanical property of part requirement, shortening forging process is also increasing with the situation of omitting heat treatment step.
But usually, steel pipe is higher than bar steel price, and particularly the weldless steel tube manufacturing cost is high.Therefore, even the blank of steel pipe as the hollow shape parts used, the effect that cost reduces is also insufficient.
Up to now, for the steel pipe that has desired mechanical property and reduced the cheapness of manufacturing cost is provided, various investigations have been carried out.
Patent documentation 1 once disclosed following technology: through the processing of the blank pipe of specific composition being implemented in specific temperature province made up reducing and rolling and tilt rolling; Making microstructure is fine and uniform ferritic, cementite tissue below the 2 μ m for the ferritic particle diameter, makes the steel pipe of HS and ductility, tenacity excellent.
Patent documentation 2 once disclosed following technology: even owing to only quicken cooling from outside surface; Produce the different environment of the speed of cooling of outside, inner face, also can spread all over the tissue that whole ground of thickness of slab direction generates the best that can have HS, H.T. concurrently.
Patent documentation 3 once disclosed: with the addition optimizing of Al and Ti, effectively utilize the intracrystalline phase transformation, and through seamless acceleration cooling steel pipe that make, that have the fine metal tissue that can have HS, H.T. concurrently after rolling.But, in this technology,, needing to reduce Al content in order effectively to utilize the intracrystalline phase transformation, the cost of deoxidation uprises.
Patent documentation 4 uses steel pipe to be purpose with manufacturing machine structural member at an easy rate, and disclosing mainly is the steel that adds Cr, and metal structure is the steel pipe of the mixed structure of self-tempering martensite single organization or itself and lower bainite.So-called self-tempering martensite is that martensitic transformation takes place austenite mutually in quickening cooling, the tissue that fine cementite is separated out in lath in the naturally cooling (air cooling) that quickens after cooling stops.
An urgent demand that enlarges, cuts down corresponding to the exhaust of environmental problem with the purposes of parts with in recent years physical construction together, demand guarantees desired mechanical property and weldless steel tube cheaply.But, in the prior art, have the limit keeping on HS, H.T. and the cost degradation.
In addition,, add Cr usually for the hardenability (hardenability) that makes steel pipe improves, if but add Cr, then there is the problem of the sticking caused surface imperfection of heat of the roller that produces when rolling, axle (plug).
The prior art document
Patent documentation 1: TOHKEMY 2000-312907 communique
Patent documentation 2: TOHKEMY 2008-266700 communique
Patent documentation 3: TOHKEMY 2009-52106 communique
Patent documentation 4: TOHKEMY 2007-262468 communique
Summary of the invention
The present invention accomplishes in view of the existing situation as above-mentioned; Its problem is; HS, the H.T. of the machinery of the structural member that is particularly suitable for cylinder, lining, cantilever etc. and axle etc. with member are provided; And weldability is excellent, and the physical construction that can suppress the generation of surface imperfection uses weldless steel tube, and through suitable thermal treatment at an easy rate the manufacturing machine structure with the method for weldless steel tube.
Present inventors are in order to prevent the generation of surface imperfection, and the steel pipe that is grouped into for the one-tenth that does not add Cr has carried out the investigation that reduces cost through the heat treatment step that omits steel pipe.Specifically, be conceived to quicken cooling attitude steel pipe (after quickening cooling, not implementing thermal treatment and the steel pipe made), discuss.
The particle diameter of original austenite that quickens the tissue of cooling attitude steel pipe is about 100 μ m, and for the steel pipe of having implemented quenching, temper (below be called " QT processing ") (below be called " QT steel pipe "), is about 20～30 μ m.
Moreover, if will be reduced to below 0.010%, and add Ti as the Al amount of deoxidant element, then can effectively utilize the intracrystalline phase transformation, make particle diameter fine.But, in the present invention,, add the Al that surpasses deoxidation needed 0.010% usually in order to reduce manufacturing cost.
Therefore, in the past, quickened the particle diameter of the tissue of cooling attitude steel pipe, compared thickly with the particle diameter of the tissue of QT steel pipe, and thought and to guarantee and QT steel pipe equal or equal above intensity and toughness.
Think that in addition if do not add Cr for the generation that prevents surface imperfection, then hardenability reduces, therefore guarantee intensity difficulty more, if add the metal beyond the Cr in order to ensure intensity, then cost rises.
But; The result of the wholwe-hearted investigation of present inventors finds; Be grouped into suitably through the one-tenth that makes steel pipe; The generation of conduct can be suppressed,, also intensity and the toughness equal can be obtained with not damaging weldability with the QT steel pipe even do not add the acceleration cooling attitude steel pipe of Cr to the upper bainite of the deleterious tissue of toughness.
The present invention is based on the invention that above-mentioned opinion is accomplished, and its main idea is following.
(1) a kind of high-strength seamless steel pipe for mechanical structure of tenacity excellent is characterized in that, in quality %, contains:
C：0.03～0.20%、
Si：0.01～0.50%、
Mn：0.80～3.00%、
Al: surpass 0.010% and be below 0.050%,
And be restricted to:
Below the P:0.020%,
Below the S:0.0080%,
Below the N:0.0080%,
Below the O:0.0050%,
Its surplus is made up of Fe and unavoidable impurities; The β that is obtained by following formula (1) is 2.50～4.00; The Pcm that is obtained by following formula (2) is 0.15～0.30, and tissue is made up of nascent martensite (fresh martensite, fresh martensite); The particle diameter of original austenite is 50～200 μ m
β＝2.7C+0.4Si+Mn+0.45Ni+Mo …（1）
Pcm＝C+Si/30+（Mn+Cu）/20
+Ni/60+Mo/15+V/10 …（2）
Wherein, C, Si, Mn, Ni, Cu, Mo, V are the content [quality %] of each element.
(2) according to the high-strength seamless steel pipe for mechanical structure of above-mentioned (1) described tenacity excellent; It is characterized in that; Above-mentioned steel pipe also contains B:0.0001～0.0030% in quality %; Replace above-mentioned formula (1) and be 2.50～4.00, replace above-mentioned formula (2) and be 0.15～0.30 by the Pcm that following formula (4) is obtained by the β that following formula (3) is obtained
β＝2.7C+0.4Si+Mn+0.45Ni+2Mo …（3）
Pcm＝C+Si/30+（Mn+Cu）/20
+Ni/60+Mo/15+V/10+5B …（4）
Wherein, C, Si, Mn, Ni, Cu, Mo, V, B are the content [quality %] of each element.
(3) according to the high-strength seamless steel pipe for mechanical structure of above-mentioned (1) or (2) described tenacity excellent, it is characterized in that above-mentioned steel pipe also contains in quality %:
Below the Ni:1.00%,
Below the Cu:1.00%,
Below the Mo:1.50%
One or more.
According to the high-strength seamless steel pipe for mechanical structure of the described tenacity excellent in above-mentioned (1)～(3), it is characterized in that (4) above-mentioned steel pipe also contains in quality %:
Below the Ti:0.050%,
Below the Nb:0.050%,
Below the V:0.050%
One or more.
According to the high-strength seamless steel pipe for mechanical structure of the described tenacity excellent in above-mentioned (1)～(4), it is characterized in that (5) above-mentioned steel pipe also contains in quality %:
Below the Ca:0.0040%,
Below the Mg:0.0010%,
Below the REM:0.005%
One or more.
(6) a kind of method of manufacture of high-strength seamless steel pipe for mechanical structure of tenacity excellent; It is the method for making each described high-strength seamless steel pipe for mechanical structure of above-mentioned (1)～(5); It is characterized in that; The steel that will have a composition in each of above-mentioned (1)～(5) carries out seamless rolling, thereafter, under 750～950 ℃ beginning temperature, implements speed of cooling and be 10～50 ℃/second acceleration cooling.
According to the present invention, in quickening cooling attitude steel pipe, can when quickening cooling, suppress the generation of upper bainite.Its result can not implement QT and handle, and has the flexible acceleration cooling attitude steel pipe equal with the QT steel pipe with the low cost manufacturing.
Embodiment
Weldless steel tube of the present invention in the generation of quickening to suppress under the cooling attitude upper bainite, improves toughness; To be controlled at suitable scope as the β of the index of hardenability; And,, will be controlled at suitable scope as the Pcm of the index of weldability in order to ensure weldability.Below, the present invention is at length explained.
At first, narration defines the reason of the chemical ingredients of steel pipe in the present invention.Below, " % " means " quality % ".
C improves extremely effective elements to intensity.In order to obtain the intensity of target, need to add the C more than 0.03%.On the other hand, surpass 0.20% C if add, then low-temperature flexibility reduces, and when welding, cracks.Therefore, C content is defined as 0.03～0.20%.In order to improve intensity, C content is preferably more than 0.07%.On the other hand, in order to ensure toughness, C content is preferably below 0.15%.
Si is a deoxidant element, is the element that helps the raising of intensity.For the effect that obtains adding, need to add the Si more than 0.01%.For intensity is improved, the Si amount is preferably more than 0.10%.On the other hand, add Si, then generate upper bainite if surpass 0.50% ground, the infringement low-temperature flexibility, so the ceiling restriction of Si content is 0.50%.Be limited to 0.25% on Si content preferred.
Mn is the element that promotes the generation of low temperature phase change tissue, for the balance that makes intensity and low-temperature flexibility improves more effective.In order to obtain its effect, need to add the Mn more than 0.80%.But,, be the upper limit therefore with 3.00% if Mn content more than 3.00%, then damages low-temperature flexibility sometimes.For the balance that makes intensity and low-temperature flexibility improves, the scope of preferred L n content is 1.50～2.40%.
P and S are impurity, if excessively contain then the toughness reduction, weldability reduces.Therefore, the upper limit of the content of P and S is set at 0.020% and 0.0080% respectively.The content of P and S, in order to ensure toughness, preferred addition is less, more preferably is respectively below 0.015% and below 0.0050%.Preferably do not contain P and S, therefore do not stipulate lower value.But, be lower than 0.0010% if the content of P and S is made as, then manufacturing cost increases, and is lower limit with 0.0010% preferably therefore.
Al is powerful deoxidant element, from the viewpoint of deoxidation cost, adds above 0.010%.If excessively add Al, then generate thick Al oxide compound, therefore the low-temperature flexibility deterioration is 0.050% with ceiling restriction.In order to improve toughness, more preferably the upper limit with the Al amount is made as 0.035%.
N is an impurity, if surpass 0.0080%, then generates thick TiN, and toughness reduces, and is 0.0080% with ceiling restriction therefore.The content of N preferably is lower than 0.0060%, if 0.0050% with more preferably next.Preferably do not contain N, so not special stipulation of lower value.But, be lower than 0.0010% if the content of N is made as, then manufacturing cost increases, and is lower limit with 0.0010% preferably therefore.
If O surpasses 0.0050% ground and contains, then generate thick acidulants, therefore the infringement low-temperature flexibility is made as 0.0050% with the upper limit.Preferably do not contain O, so not special stipulation of lower limit.But, be lower than 0.0010% if the content of O is made as, then manufacturing cost increases, and is lower limit with 0.0010% preferably therefore.
In steel of the present invention, can also add B.B improves hardenability, helps the element of the highly malleablized of steel.In order to obtain its effect, preferably add the B more than 0.0001%.On the other hand, if the addition of B, then produces the precipitate of BN etc. more than 0.0030%, hardenability reduces sometimes.The scope of preferred B content is 0.0010～0.0020%.
In addition, also can add one or more of Ni, Cu, Mo.These elements are the elements that improve hardenability, help the highly malleablized of steel of the present invention.
Ni does not make the low-temperature flexibility deterioration and element that intensity is improved, for the effect that obtains adding is preferably added more than 0.05%.Add Ni if surpass 1.00% ground, segregation then takes place, tissue becomes inhomogeneous, and the toughness deterioration is limited to 1.00% on the therefore preferred Ni content sometimes.The addition of Ni preferably is lower than 0.80%, more preferably below 0.50%.Further preferred range is 0.25～0.45%.
Cu and the Mo effect in order to obtain intensity is improved is preferably added more than 0.05% respectively.If Cu and Mo addition surpass 1.00% and 1.50% respectively, then damage weldability sometimes.In addition, if add Cu separately then produce surface imperfection sometimes, therefore preferred Cu and Ni side by side add.
And then, also can add one or more of Ti, Nb, V.They are the elements that the intensity of steel improved through precipitation strength.
Ti preferably contains more than 0.005% in order to make the steel precipitation strength.In addition, for fixing N, raising toughness, preferably add the Ti more than 0.010% as impurity.If Ti content surpasses 0.050%, then toughness reduces because of thick separating out of Ti oxide compound sometimes, so preferred upper limit is 0.050%.In addition,, low-temperature flexibility is improved, be limited to below 0.035% on the preferred Ti content in order to prevent thickization of TiN.
Nb is the precipitate that not only generates carbide, nitride etc., and the austenitic recrystallize when suppressing rolling will be organized miniaturization, hardenability is increased, to the highly malleablized effective elements of steel.If Nb content surpasses 0.050%, then generate the precipitate of thick Nb, therefore the toughness deterioration is made as 0.050% with the upper limit sometimes.In order to obtain the effect that Nb adds, preferably add more than 0.005%.
V generates carbide, nitride, and the element through precipitation strength improves the intensity of steel also has the effect that improves hardenability.If V content surpasses 0.050%, then carbide, thickization of nitride are damaged toughness sometimes, are limited to 0.050% on the therefore preferred V content.In order to obtain the effect that V adds, preferably add more than 0.005%.
And then, also can add one or more of Ca, Mg, REM.They are elements that the shape of adjustment inclusion improves workability, and, separate out as sulfide, oxide compound or oxysulfide, have the hardened effect at the junction surface that prevents steel pipe.
If the content of Ca, Mg and REM surpasses 0.0040%, 0.0010% and 0.005% respectively, then inclusion becomes too much, and therefore the ductility deterioration is set at 0.0040%, 0.0010% and 0.005% respectively with the upper limit.In order to improve hot workability, the lower limit of the content of preferred Ca, Mg and REM is respectively 0.0005%, 0.0005% and 0.0001%.
Its surplus beyond the above-mentioned element is Fe and unavoidable impurities.As unavoidable impurities, can enumerate the Sn that sneaks into from waste material, Bi etc.In addition, also can be in the scope of not damaging characteristic of the present invention, contain the Zr that when deoxidation, adds as required, Ta etc.
Weldless steel tube of the present invention is characterized in that suppressing the generation of upper bainite, has improved toughness.In order to suppress the generation of upper bainite, need to improve the hardenability of steel.Therefore, in the present invention, except the composition that limits each element, also will be limited to 2.50～4.00 scope by the β that following formula (1) is obtained.β is the index of the hardenability of steel, and the symbol of element of formula (1) is represented the content (quality %) of each element.
β＝2.7C+0.4Si+Mn+0.45Ni+Mo …（1）
If β is less than 2.50, low-temperature flexibility deterioration then.In addition, if β surpasses 4.00, then HAZ toughness, weldability worsen.
And, will be defined as 0.15～0.30 by the Pcm that following formula (2) are obtained.The symbol of element of formula (2) is represented the content (quality %) of each element.
Pcm＝C+Si/30+（Mn+Cu）/20
+Ni/60+Mo/15+V/10 …（2）
If Pcm less than 0.15, then can not get needed intensity, and weldability worsens.If Pcm surpasses 0.30, then low-temperature flexibility deterioration, and weldability worsens.The scope of preferred Pcm is above 0.20 and below 0.30.
During the selection element that in not adding type (1), formula (2), contained, the content of this element calculates as 0.
When steel pipe contains B, replace above-mentioned formula (1), formula (2), use following formula (3), formula (4) to obtain β and Pcm.The symbol of element in formula (3) and the formula (4) is represented the content (quality %) of each element.
β＝2.7C+0.4Si+Mn+0.45Ni+2Mo …（3）
Pcm＝C+Si/30+（Mn+Cu）/20
+Ni/60+Mo/15+V/10+5B …（4）
During the selection element that in not adding type (3), formula (4), contained, with the situation of formula (1), formula (2) likewise, the content of this element calculates as 0.
β by formula (1) and formula (3) definition is to the synergetic empirical formula of the influence of the hardenability of steel with each element.The difference of formula (1) and formula (3) is the coefficient of Mo.This means, compare, contain at the same time under the situation of Mo and B that because synergistic effect, the effect that improves the Mo of hardenability improves with the situation that contains Mo separately.
The metal structure of weldless steel tube of the present invention is made up of nascent martensite.Nascent martensite is the tissue of lath-shaped, in the observation of opticmicroscope, can't see cementite, and this point is different with tempered martensite and bainite.Weldless steel tube of the present invention owing under the state of cooling, make, does not therefore contain tempered martensite.In addition, weldless steel tube of the present invention is the weldless steel tube that has suppressed to make the generation of the phase that toughness reduces, and does not also contain upper bainite.
Nascent martensite is through cooling, the tissue that austenite phase transformation forms, and the particle diameter of original austenite is big more, and toughness is just low more.But under the situation of making weldless steel tube, usually the Heating temperature of steel billet is high, can not guarantee because of perforation and the rolling cumulative deformation that imports, and therefore is difficult to make original austenite to become fine.
In the present invention, the particle diameter with original austenite is set at more than the 50 μ m.This be because, make the particle diameter of original austenite be lower than 50 μ m in order not implement QT to handle, need bore a hole with rolling the cause that manufacturing cost uprises at low temperatures.
On the other hand, toughness reduces if the particle diameter of original austenite is thick, therefore in the present invention, in order to ensure toughness, the particle diameter of original austenite is set at below the 200 μ m.
The particle diameter of original austenite can be measured based on JIS G 0551 standard.
Weldless steel tube of the present invention is through composition, particularly hardenability index β and weldability index Pcm are made as suitable scope, and making metal structure is nascent martensite, and the particle diameter that makes original austenite is the steel pipe of 50～200 μ m.And, according to the present invention, can provide particularly that manufacturing cost does not rise, the weldless steel tube that intensity and flexible balance are excellent.Moreover physical construction of the present invention is that for example tensile strength is more than the 780MPa with the preferred characteristic of weldless steel tube, more preferably more than the 980MPa, and the summer under-20 ℃ than impact absorb can be for 100J more than.
Then, the method for manufacture for weldless steel tube of the present invention describes.
Steel pipe of the present invention, be hot down will be at about 1100～1300 ℃ of warmed-up perforated steel billits, the rolling and weldless steel tube made, also sometimes seamless rolling after by extension process.From viewpoint, preferably increase through perforation, the rolling cumulative deformation that makes by the caused H.T.ization of crystal grain miniaturization.
Seamless rolling after, as required,, carry out the temperature of reheat thereafter to regulation via mill pipe, shaping process.Moreover, before reheat,, then partly undergo phase transition, behind the reheat, because exaggerated grain growth produces thick crystal grain sometimes partly if the temperature of steel pipe is lower than 600 ℃.In addition, produce precipitate during the cooling before reheat sometimes, the solid solution capacity that improves the element of hardenability reduces, and hardenability reduces, and does not therefore preferably make the temperature of steel pipe be lower than 600 ℃ and carry out reheat.
Behind the reheat, implement reducing and rolling as required, steel pipe is quickened cooling.The temperature of the steel pipe when beginning to quicken to cool off, if too high, thickization of austenite crystal then, toughness reduces sometimes, therefore is set at below 950 ℃, is preferably below 900 ℃.In addition, in order to suppress the ferrite transformation from crystal boundary, the temperature of the steel pipe when beginning to quicken to cool off is set at more than 750 ℃.
If it is slow excessively to quicken the refrigerative speed of cooling, then generate upper bainite.Upper bainite is the bainite that produces under than higher temperature, contains the island martensite body as partial embrittlement phase morely, therefore causes flexible and reduces.In addition, if speed of cooling is too fast, the difficulty that becomes of cooling uniformly then, become cooling after, steel pipe is deformation reason significantly.Therefore, quicken refrigerative speed and be made as 10～50 ℃/second.The so-called refrigerative speed of quickening is meant from quickening refrigerative to begin the average speed of cooling that stops to cooling.
Even cooling stops the too high upper bainite that also generates of temperature sometimes, preferably stopping to quicken cooling below 400 ℃, more preferably stopping to quicken cooling below 250 ℃.
Method of cooling, can from make water directly touch the method for the outside surface of steel pipe, along at random selected the method for the tangential direction of steel pipe periphery touching, the spray cooling etc.
Under suitable speed of cooling, quicken cooling through having the steel pipe that one-tenth of the present invention is grouped into, the metal structure that constitutes by nascent martensite that the generation that can obtain upper bainite has been suppressed.In addition, have the steel pipe that one-tenth of the present invention is grouped into, the particle diameter of original austenite is 50～200 μ m, therefore need not reduce rolling temperature or make full use of the intracrystalline phase transformation.Therefore, according to the present invention, cost is risen and the steel pipe of manufacturing intensity and tenacity excellent.
Embodiment
Melting has in the table 1 steel that the one-tenth of record is grouped into, and casts out the steel billet that diameter is 100～170mm through converter, continuous casting process.These steel billets are heated to 1100～1250 ℃, through completely be this graceful axle tube rolling (Mannesmann plug mill) mode bore a hole, rolling, behind reheat to 900～1000 ℃, under the condition shown in the table 2, quicken cooling.Quickening cooling is to adopt the method that makes water directly touch the outside surface of steel pipe to carry out.After the manufacturing, the having or not of the surface imperfection of Visual Confirmation steel pipe.
Table 2
The size of the steel pipe that produces is as shown in table 2.From the steel pipe that produces vertically and near the central part of wall thickness direction produce sample, utilize the observation by light microscope metal structure, metal structure is categorized as nascent martensite, upper bainite, lower bainite, perlite, ferritic.In addition, the particle diameter of original austenite is based on JIS G 0551 standard test.
The particle diameter of so-called original austenite is meant the particle diameter that becomes martensite tissue (tissue under the high temperature) before mutually.Because the particle diameter of original austenite does not change after becoming martensite mutually yet, even therefore can measure after the phase transformation yet.
Tension test uses circular-arc No. 12 tensile test specimens of JIS to carry out, and has measured ys and tensile strength.The flexible evaluation is according to JIS Z 2242 standards, uses the full-scale test specimen of 2mmV breach, implements Charpy impact test down at-20 ℃, has measured the absorption ability.
Table 3 illustrates the result.
Table 3
Zero: do not have surface imperfection *: surface imperfection is arranged
M: nascent martensite, BL: lower bainite, BU: upper bainite,
P: perlite, F: ferritic
Underscore means outside scope of the present invention.
Use to satisfy that the one-tenth of having stipulated in the present invention is grouped into, steel A～I of β and Pcm, the steel pipe that adopts the method for manufacture stipulated among the present invention to produce is organized as nascent martensite, the particle diameter of original austenite is 50～200 μ m.
Its result has as the needed intensity of steel for mechanical structure pipe, and the absorption under-20 ℃ of Charpy impact test can (vE-20) be more than the 115J, demonstrates high value, and toughness is excellence also.
Use steel G, change cooling beginning temperature, speed of cooling within the scope of the invention and the steel pipe (No.7,10～13) that produces, all have the proper metal tissue, and, have as the needed intensity of steel for mechanical structure pipe.And the absorption under-20 ℃ of Charpy impact test can (vE-20) be more than the 115J, shows high value, and toughness is excellence also.
No.14 is owing to contain Cr, and therefore through seamless rolling, steel pipe has produced surface imperfection.
The C of No.15 is lower than the lower limit of stipulating among the present invention, and β is 2.29, and hardenability is poor.Therefore, quicken cooled metal structure and become upper bainite and lower bainite, its result, intensity is low, and toughness is also poor.
The B ultrasonic of No.16 is crossed set upper limit among the present invention, and β is 2.11, and hardenability is poor.Quicken cooled metal structure and become upper bainite and perlite, its result, intensity is low, and toughness is also poor.
The C of No.17 surpasses set upper limit among the present invention, is nascent martensite though therefore quicken cooled metal structure, and it is too high that intensity becomes, and toughness reduces.
Though the composition of each element of No.18 within the scope of the invention, β is 4.01, bigger.Its result is nascent martensite though quicken cooled metal structure, and it is too high that intensity becomes, and toughness reduces.
The steel pipe that No.19 is to use to become to be grouped into, β and Pcm steel G within the scope of the invention produce, but cooling beginning temperature is high, so metal structure becomes upper bainite and ferritic, intensity is low, and toughness is also poor.
The steel pipe that No.20 is to use steel G to produce, but cooling beginning temperature is high, so the change of the median size of original austenite is big, and its result, toughness reduces.
The steel pipe that No.21 is to use steel G to produce, but speed of cooling is slow, so metal structure becomes perlite and ferritic, and also the median size of original austenite diminishes, its result, and intensity is low, and toughness is also weaker.
Shown in above, method of manufacture manufacturing of the present invention satisfies that the one-tenth of stipulating among the present invention is grouped into through adopting, the steel of β and Pcm, can make to have the flexible equal with the QT steel pipe, do not implement the acceleration cooling attitude steel pipe that QT handles.
Utilize possibility on the industry
According to the present invention; Can with the low cost manufacturing be particularly suitable for cylinder, lining, cantilever etc. structural member and axle etc. machinery with member, have and the QT steel pipe is equal or equal above flexible weldless steel tube, so big to the contribution of automobile industry, mechanical industry etc.
Claims (6)
1. the high-strength seamless steel pipe for mechanical structure of a tenacity excellent is characterized in that, in quality %, contains:
C：0.03～0.20%、
Si：0.01～0.50%、
Mn：0.80～3.00%、
Al: surpass 0.010% and be below 0.050%,
And be restricted to:
Below the P:0.020%,
Below the S:0.0080%,
Below the N:0.0080%,
Below the O:0.0050%,
Its surplus is made up of Fe and unavoidable impurities, and the β that is obtained by following formula (1) is 2.50～4.00, and the Pcm that is obtained by following formula (2) is 0.15～0.30, and tissue is made up of nascent martensite, and the particle diameter of original austenite is 50～200 μ m,
β＝2.7C+0.4Si+Mn+0.45Ni+Mo …（1）
Pcm＝C+Si/30+（Mn+Cu）/20
+Ni/60+Mo/15+V/10 …（2）
Wherein, C, Si, Mn, Ni, Cu, Mo, V are the content [quality %] of each element.
2. the high-strength seamless steel pipe for mechanical structure of tenacity excellent according to claim 1; It is characterized in that; Said steel pipe also contains B:0.0001～0.0030% in quality %; Replace said formula (1) and be 2.50～4.00, replace said formula (2) and be 0.15～0.30 by the Pcm that following formula (4) is obtained by the β that following formula (3) is obtained
β＝2.7C+0.4Si+Mn+0.45Ni+2Mo …（3）
Pcm＝C+Si/30+（Mn+Cu）/20
+Ni/60+Mo/15+V/10+5B …（4）
Wherein, C, Si, Mn, Ni, Cu, Mo, V, B are the content [quality %] of each element.
3. the high-strength seamless steel pipe for mechanical structure of tenacity excellent according to claim 1 and 2 is characterized in that, said steel pipe also contains in quality %:
Below the Ni:1.00%,
Below the Cu:1.00%,
Below the Mo:1.50%
One or more.
4. according to the high-strength seamless steel pipe for mechanical structure of each described tenacity excellent of claim 1～3, it is characterized in that said steel pipe also contains in quality %:
Below the Ti:0.050%,
Below the Nb:0.050%,
Below the V:0.050%
One or more.
5. according to the high-strength seamless steel pipe for mechanical structure of each described tenacity excellent of claim 1～4, it is characterized in that said steel pipe also contains in quality %:
Below the Ca:0.0040%,
Below the Mg:0.0010%,
Below the REM:0.005%
One or more.
6. the method for manufacture of the high-strength seamless steel pipe for mechanical structure of a tenacity excellent; It is the method for making each described high-strength seamless steel pipe for mechanical structure of claim 1～5; It is characterized in that; The steel that will have a composition of putting down in writing in each of claim 1～5 carries out seamless rolling, thereafter, under 750～950 ℃ beginning temperature, implements speed of cooling and be 10～50 ℃/second acceleration cooling.
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| CN201410152807.7A CN103924155B (en) | 2010-03-05 | 2011-03-03 | The high-strength seamless steel pipe for mechanical structure and its manufacturing method of excellent tenacity |
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| JP049298/2010 | 2010-03-05 | ||
| JP2010049298 | 2010-03-05 | ||
| PCT/JP2011/055562 WO2011108764A1 (en) | 2010-03-05 | 2011-03-03 | High-strength seamless steel pipe for mechanical structure which has excellent toughness, and process for production of same |
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Cited By (4)
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| CN104911475A (en) * | 2015-06-25 | 2015-09-16 | 东北大学 | Low-carbon medium-manganese high-toughness super-thick steel plate and preparation method thereof |
| CN108393355A (en) * | 2018-03-26 | 2018-08-14 | 天津商业大学 | A kind of manufacturing method of oil/gas well novel seamless steel tube |
| CN110144444A (en) * | 2015-07-09 | 2019-08-20 | 安赛乐米塔尔公司 | For suppressing the steel of hardening and the component of the compacting hardening by such steel making |
| CN114318128A (en) * | 2020-09-30 | 2022-04-12 | 宝山钢铁股份有限公司 | Self-tempering martensite type high-strength and high-toughness seamless steel pipe and manufacturing method thereof |
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| CN114107794B (en) * | 2020-08-31 | 2023-08-11 | 宝山钢铁股份有限公司 | 980 MPa-grade ultra-low carbon martensite and residual austenite ultra-high hole-enlarging steel and manufacturing method thereof |
| CN113528954B (en) * | 2021-06-29 | 2022-06-14 | 鞍钢股份有限公司 | Seamless steel tube for cold-drawing hydraulic cylinder and manufacturing method thereof |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1388835A (en) * | 2000-06-14 | 2003-01-01 | 川崎制铁株式会社 | Steel pipe for use in reinforcement of automobile and method for production thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH10140250A (en) * | 1996-11-12 | 1998-05-26 | Sumitomo Metal Ind Ltd | Production of steel tube for air bag, having high strength and high toughness |
| JPH10140238A (en) * | 1996-11-12 | 1998-05-26 | Sumitomo Metal Ind Ltd | Production of steel tube for air bag, having high strength and high toughness |
| JP3975852B2 (en) * | 2001-10-25 | 2007-09-12 | Ｊｆｅスチール株式会社 | Steel pipe excellent in workability and manufacturing method thereof |
| JP4751224B2 (en) * | 2006-03-28 | 2011-08-17 | 新日本製鐵株式会社 | High strength seamless steel pipe for machine structure with excellent toughness and weldability and method for producing the same |
| JP5020690B2 (en) * | 2007-04-18 | 2012-09-05 | 新日本製鐵株式会社 | High strength steel pipe for machine structure and manufacturing method thereof |
| JP4959471B2 (en) * | 2007-08-28 | 2012-06-20 | 新日本製鐵株式会社 | High strength seamless steel pipe with excellent toughness for machine structure and manufacturing method thereof |
-
2011
- 2011-03-03 CN CN201410152807.7A patent/CN103924155B/en not_active Expired - Fee Related
- 2011-03-03 WO PCT/JP2011/055562 patent/WO2011108764A1/en active Application Filing
- 2011-03-03 JP JP2011532386A patent/JP4860786B2/en not_active Expired - Fee Related
- 2011-03-03 CN CN2011800123186A patent/CN102782173A/en active Pending
- 2011-03-03 KR KR1020127022016A patent/KR101471730B1/en active IP Right Grant
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1388835A (en) * | 2000-06-14 | 2003-01-01 | 川崎制铁株式会社 | Steel pipe for use in reinforcement of automobile and method for production thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104911475A (en) * | 2015-06-25 | 2015-09-16 | 东北大学 | Low-carbon medium-manganese high-toughness super-thick steel plate and preparation method thereof |
| CN104911475B (en) * | 2015-06-25 | 2017-05-10 | 东北大学 | Preparation method for low-carbon medium-manganese high-toughness super-thick steel plate |
| CN110144444A (en) * | 2015-07-09 | 2019-08-20 | 安赛乐米塔尔公司 | For suppressing the steel of hardening and the component of the compacting hardening by such steel making |
| CN110144443A (en) * | 2015-07-09 | 2019-08-20 | 安赛乐米塔尔公司 | For suppressing the steel of hardening and the component of the compacting hardening by such steel making |
| CN110144444B (en) * | 2015-07-09 | 2021-05-25 | 安赛乐米塔尔公司 | Steel for press hardening and press hardened component made of such steel |
| CN110144443B (en) * | 2015-07-09 | 2021-05-25 | 安赛乐米塔尔公司 | Steel for press hardening and press hardened component made of such steel |
| US11319610B2 (en) | 2015-07-09 | 2022-05-03 | Arcelormittal | Steel for press hardening and press hardened part manufactured from such steel |
| US11814696B2 (en) | 2015-07-09 | 2023-11-14 | Arcelormittal | Steel for press hardening and press hardened part manufactured from such steel |
| CN108393355A (en) * | 2018-03-26 | 2018-08-14 | 天津商业大学 | A kind of manufacturing method of oil/gas well novel seamless steel tube |
| CN114318128A (en) * | 2020-09-30 | 2022-04-12 | 宝山钢铁股份有限公司 | Self-tempering martensite type high-strength and high-toughness seamless steel pipe and manufacturing method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| CN103924155A (en) | 2014-07-16 |
| KR20120107522A (en) | 2012-10-02 |
| CN103924155B (en) | 2018-10-26 |
| JPWO2011108764A1 (en) | 2013-06-27 |
| KR101471730B1 (en) | 2014-12-10 |
| JP4860786B2 (en) | 2012-01-25 |
| WO2011108764A1 (en) | 2011-09-09 |
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