CN103003462A - Rolled steel bar or wire for hot forging - Google Patents
Rolled steel bar or wire for hot forging Download PDFInfo
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- C—CHEMISTRY; METALLURGY
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
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- 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
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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Abstract
Disclosed is a rolled steel bar or wire for hot forging, which has a chemical composition that contains 0.10-0.20% of C, 0.01-0.30% of Si, 1.00-2.30% of Mn, 0.040% or less of S, 0.10-0.80% of Cr, 0.010-0.080% of Al, 0.0002-0.0050% of B, 0.010-0.080% of Ti and 0.0020-0.0080% of N, with the balance made up of Fe and impurities, while limiting P to 0.040% or less, Cu to less than 0.10%, Ni to less than 0.10%, Mo to less than 0.05% and V to 0.01% or less among the impurities, in said chemical composition [Ti - 3.4N = 0.001] being satisfied, Ceq represented by a specific formula of C, Si, Mn, Ni, Cr, Mo and V being 0.57 or less, and DI represented by a specific formula of C, Si, Mn, P, S, Cr, Ni, Mo and Cu being 70-170. The rolled steel bar or wire for hot forging has 10 or more Ti precipitates having a circle-equivalent diameter of 0.07-1.0 [mu]m and 10 or more Ti precipitates having a circle-equivalent diameter of 0.01-0.05 [mu]m in an area of 100 [mu]m2. Since the rolled steel bar or wire for hot forging is weldable and has excellent strength and toughness of the matrix and excellent toughness of HAZ, the rolled steel bar or wire for hot forging is suitable as a material for underbody components of automobiles such as a spindle.
Description
Technical field
The present invention relates to heat forged with rolling bar steel or wire rod.Specifically, relate to can weld and heat forged that intensity and toughness (particularly at low temperatures toughness) are excellent with bar steel or wire rod.
Background technology
The running gear parts of the automobiles such as axletree need higher intensity and excellent toughness.
The starting material of above-mentioned parts use " the carbon steels for machine structural purposes steel alloy " of the middle carbon such as SCM435H of stipulating among S48C, the JISG4051 (2009) of regulation among the JIS G 4051 (2009) usually.
Usually, for above-mentioned steel, after heat forged, implement the thermal treatment of quenching-tempering, afterwards, utilize machining established practice setting shape.And then, in order to engage with miscellaneous part, implement the processing such as bolt hole processing, the processing of spline (spline) shape, be finish-machined to required parts.
But the machining cost of high-strength parts is very big.Therefore, need to utilize welding to engage with miscellaneous part.
When reducing C content, can prevent welding crack, therefore can weld.
But, when reducing C content, be difficult to make parts to possess high strength.
And then, in the situation that the welding since heat affected zone (below, be called " HAZ ".) coarse grains, therefore be difficult to especially at low temperatures guarantee good toughness.And, be susceptible to the automobile that as axletree, applies thump running gear parts, not only need to suppress the toughness drop of HAZ, but also need to improve the toughness of parts mother metal self.
Therefore, as the starting material of above-mentioned parts, imagination requires HAZ and mother metal can guarantee especially at low temperatures the starting material of excellent toughness in the situation that cold district uses.
" manufacture method of the steel that can weld with high strength and high tenacity and the section's material that uses it " disclosed in the patent documentation 1 for this reason.
[prior art document]
[patent documentation]
[patent documentation 1] TOHKEMY 2007-84909 communique
Summary of the invention
The problem that invention will solve
In the situation that patent documentation 1 disclosed technology, also also insufficient for the consideration of the toughness of HAZ and mother metal and welding crack.And then in order to improve the toughness of mother metal, the Heating temperature in the time of need to be with heat forged is reduced to 1100 ℃ and controls forging to get off.But if the Heating temperature when reducing heat forged, then the resistance to deformation as raw-material steel uprises.Therefore, patent documentation 1 disclosed technology may not be preferred aspect manufacture component.
Steel as requiring weldability has Plate Steel.But different from Plate Steel, the raw-material bar steel and the wire rod that are used for the parts as axletree are that rolled stock is further joined the high temperature about 1200 ℃ and is configured as component shape with heat forged, then implement the material that the thermal treatment of quenching-tempering forms.Therefore, even the high temperature that needs once again starting material integral body to be heated to about 1200 ℃ after rolling also has stable base metal tenacity.
The present invention makes in view of above-mentioned present situation, its purpose is, provide and can weld and intensity and the tenacity excellent of mother metal, and the toughness of HAZ also raw-material, the heat forged of excellent, the running gear parts that are suitable as the automobile such as axletree with rolling bar steel or wire rod.
For the means that address the above problem
The inventor at first in the problems referred to above, prevent welding crack and guarantee that the intensity of mother metal excellence carried out various investigation and research repeatedly.Its result obtains following opinion.
(a) relevant welding crack
(a-1) have or not the maximum hardness that produces welding crack and depend on HAZ (below, be called " Hmax ".)。If Hmax with Vickers' hardness (below, be called " HV hardness ".) meter exceed 400, then easily produce welding crack.
(a-2) as the index of prediction Hmax, often use carbon equivalent (Ceq).For example put down in writing following formula among the JIS G3106 (2008).
Ceq＝C+(Si/24)+(Mn/6)+(Ni/40)+(Cr/5)+(Mo/4)+(V/14)
In the following formula, C, Si, Mn, Ni, Cr, Mo and V represent the content in quality % of each element.
Motion has the relational expression of a lot of Ceq and Hmax, but uses following formula as benchmark Hmax to be predicted for the data inventor shown in the embodiment etc.
Hmax＝583×Ceq+65
(a-3) from above-mentioned (a-1) and (a-2), in order to prevent welding crack, effectively: not only will limit as the content of C, Si, Mn and the Cr of the element that is intended to contain in the mother metal is arranged, also will limit Ni, Mo in the impurity and the content of V.
(b) intensity of relevant mother metal
(b-1) for the Hmax relevant with welding crack, in other words, for Ceq, the C content influence is maximum.Therefore, prevent welding crack and usually replace C to guarantee that intensity is better by containing the unit that is improved hardenability by reducing C content.
(b-2) for quenching-thermal treatment of tempering after, especially guarantee abundant intensity (counting more than the 800MPa with tensile strength) in (particularly after the tempering under 475 ℃) after the tempering under 400～500 ℃, can be the chemical constitution that mode more than 70 is adjusted mother metal according to the ideal critical diameter shown in the following formula (DI) for example.
DI＝25.4×0.311×C
0.5×(1+0.64×Si)×(1+4.10×Mn)×(1+2.83×P)×(1-0.62×S)×(1+2.33×Cr)×(1+0.52×Ni)×(1+3.14×Mo)×(1+0.27×Cu)×{1+1.50×(0.90-C)}
C in the following formula, Si, Mn, P, S, Cr, Ni, Mo and Cu represent the content in quality % of each element.
Even if can prevent as described above welding crack and guarantee that mother metal is high strength, the toughness of HAZ and mother metal also may not be excellent.
For this reason, below, the inventor has carried out various investigation and research repeatedly to the toughness of leaving in the problems referred to above, guarantee HAZ and mother metal excellence.Its result obtains following opinion.
(c) about the toughness of HAZ
(c-1) when welding HAZ be heated to and exceed 1200 ℃ high temperature.As " pinning (pinning) particle " that under high temperature so, suppress the coarse grains of HAZ, because carbide and/or carbonitride can cause solid solution, therefore use the high TiN of solid solubility temperature better.
(c-2) though TiN can solid solution when the heating that is used for heat forged, during the heating that is used for quenching yet in matrix.Therefore, if the stage TiN of the bar steel behind hot rolling or wire rod is in the state of separating out with the size of appropriateness, then when welding, can suppress the coarse grains of HAZ.That is, the TiN that separates out by the stage that is controlled at bar steel behind the hot rolling or wire rod separates out form, can improve the toughness of HAZ.
(d) toughness of relevant mother metal
(d-1) even be the chemical constitution that mode more than 70 is adjusted mother metal according to making above-mentioned DI, if the content of C, Si, Mn and Cr is too much, the hardness that then also can make mother metal becomes too high and reduces the toughness of mother metal.
(d-2) not only the content of above-mentioned C, Si, Mn and Cr can affect the toughness of mother metal, and the content of the P in the impurity, S, Cu, Ni and Mo also can affect the toughness of mother metal.
(d-3) in order to make mother metal guarantee good toughness, adjust the chemical constitution of mother metal and get final product according to making DI not exceed 170 mode.
(d-4) in order to improve the toughness of mother metal, except adjusting above-mentioned DI, also need to prevent thickization of the austenite crystal that when being used for the heating of quenching, produces.
Pinning size of particles when (d-5) above-mentioned TiN is as the heating that is used for quenching is larger, so effect is little.Relative therewith, it is that Ti (C, N) is finer than TiN that TiC and solid solution have the TiC of N, when therefore heating in order to quench to the temperature of 900 ℃ of front and back, works as " pinning particle ", has the effect that suppresses thickization of austenite crystal.
(d-6) in the too little situation of the size of TiC and Ti (C, N), the heating when carrying out heat forged to the temperature of 1200 ℃ of front and back can cause TiC and Ti (C, N) solid solution in matrix.On the other hand, in the thick situation of the size of TiC and Ti (C, N), quantity tails off.
(d-7) above-mentioned during for the heating of quenching, for TiC and Ti (C, N) are fully worked as " pinning particle ", importantly fine TiC and Ti (C, N) greatly mainly with before the heating that is used for quenching, be that state after the heat forged distributes.
(d-8) if the stage TiC of the bar steel behind hot rolling or wire rod and Ti (C, N) are in the state of separating out with the size of appropriateness, then can satisfy the condition of above-mentioned (d-7), thickization of the austenite crystal in the time of therefore, can suppressing for the heating of quenching.That is, the TiC that separates out by the stage that is controlled at bar steel behind the hot rolling or wire rod and Ti (C, N) separate out form, thereby can improve the toughness of mother metal.Therefore, can under low temperature environment, use parts.
(d-9) Ti is combined with N than C is preferential.Therefore, the two need to contain the Ti of the amount of being combined with N and C both sides as " pinning particle " in order to use (TiN) and (TiC and Ti (C, N)).
The present invention is based on above-mentioned opinion and finish, its purport is that the heat forged shown in following (1) is with the manufacture method of the heat forged shown in rolling bar steel or wire rod and (2) with rolling bar steel or wire rod.
(1) a kind of heat forged is characterized in that with rolling bar steel or wire rod, and have following chemical constitution: % contains in quality
C：0.10～0.20％、
Si：0.01～0.30％、
Mn：1.00～2.30％、
Below the S:0.040%,
Cr：0.10～0.80％、
Al：0.010～0.080％、
B：0.0002～0.0050％、
Ti:0.010～0.080% and
N：0.0020～0.0080％，
Surplus is made of Fe and impurity,
P in the impurity, Cu, Ni, Mo and V are restricted to
Below the P:0.040%,
Cu: less than 0.10%,
Ni: less than 0.10%,
Mo: less than 0.05% and
Below the V:0.01%,
And the fn1 shown in the following formula (1) is more than 0.001, the Ceq shown in the formula (2) is below 0.57, the DI shown in the formula (3) is 70～170;
And, at 100 μ m
2Area in to separate out Ti precipitate and the diameter of equivalent circle more than 10 that 10 above diameter of equivalent circle are 0.07～1.0 μ m be the Ti precipitate of 0.01～0.05 μ m.
fn1＝Ti-3.4N…(1)
Ceq＝C+(Si/24)+(Mn/6)+(Ni/40)+(Cr/5)+(Mo/4)+(V/14)…(2)
DI＝25.4×0.311×C
0.5×(1+0.64×Si)×(1+4.10×Mn)×(1+2.83×P)×(1-0.62×S)×(1+2.33×Cr)×(1+0.52×Ni)×(1+3.14×Mo)×(1+0.27×Cu)×{1+1.50×(0.90-C)}…(3)
Above-mentioned Ti, N, C, Si, Mn, Ni, Cr, Mo, V, P, S and Cu in various represents the content in quality % of each element.
Above-mentioned Ti precipitate refers to TiN, TiC and Ti (C, N).In addition, below, it is that Ti (C, N) is also referred to as TiC sometimes that solid solution has the TiC of N.
In addition, refer to the material from sneaking into as ore, waste material (scrap) or the manufacturing environment etc. of raw material when the industrial manufacturing iron steel as " impurity " in " Fe and the impurity " of surplus.
(2) a kind of heat forged is characterized in that with the manufacture method of rolling bar steel or wire rod, speed of cooling be under 2.0 ℃/ the condition more than the min in above-mentioned to having (1) the molten steel of the chemical constitution of record cast continuously,
This slab is heated to the temperature range more than 1100 ℃ and keeps more than the 30min, and under the condition that satisfies following formula (4), carry out breaking down and bar steel is rolling or rod rolling, and be cooled to 800～600 ℃ temperature range after the rolling or rod rolling with the speed of cooling of 5～100 ℃/min at bar steel.
Y＝(T
1+273)×log(t
1+t
2 T(2))≤7.5×10
3…(4)
T in the above-mentioned formula (4) represent take " ℃ " as the Heating temperature of unit, the hold-time take " s " as unit when t is illustrated in Heating temperature T, subscript 1 expression breaking down operation, subscript 2 expression bar steel rolling process or rod rolling operations, T (2)=(T
2+ 273)/(T
1+ 273).
That is, T
1For the Heating temperature in the breaking down operation (℃), T
2The Heating temperature of or rod rolling operation rolling for bar steel (℃), t
1For in the breaking down operation at T
1Hold-time under ℃ (s), t
2For bar steel in the rolling or rod rolling operation at T
2Hold-time under ℃ (s).
Temperature during above-mentioned each processed and speed of cooling all refer to be take the surface temperature and the speed of cooling of benchmark.
The invention effect
Heat forged of the present invention can be welded with rolling bar steel or wire rod and intensity and the tenacity excellent of mother metal, and the toughness of HAZ is also excellent, and the starting material that therefore can be suitable as the running gear parts of the automobile such as axletree use.
Description of drawings
Fig. 1 is that (" R " represents radius to the R/2 section in the pole of the test film of the lap joint of the wide 25mm that uses among embodiment welding usefulness and the diameter 36mm that takes it.) the figure that describes of position relationship.In the figure, the side that the size of test film is long is called " width " of test film.
Fig. 2 is the figure of size shape of the test film of the lap joint welding usefulness used among the embodiment of expression.Dimensional units among the figure is " mm ".
Fig. 3 carries out the figure that the situation of lap joint welding schematically illustrates to the test film that uses 2 oblique cut grafting joints welding usefulness among the embodiment.
Fig. 4 is to using the test materials will carry out the lap joint welding to measure the figure that the position of the grain size number of HAZ describes at width central position rip cutting 2 five equilibriums and in the vertical section so that welding metal becomes test film that the mode of the central part of length direction is cut into 30mm among the embodiment.Dimensional units among the figure is " mm ".
Fig. 5 is to using the test materials will carry out the lap joint welding to measure the figure that the situation of HV hardness describes at width central position rip cutting 2 five equilibriums and in the vertical section so that welding metal becomes test film that the mode of the central part of length direction is cut into 30mm among the embodiment.Dimensional units among the figure is " mm ".
Embodiment
Below, each important document of the present invention is elaborated.In addition, " % " of the content of each element refers to " quality % ".
(A) chemical constitution of bar steel or wire rod
C：0.10～0.20％
C has the effect of the martensite hardness after the quenching that improves steel, and, the effect of the coarse grains when having the heating that suppresses to be used for to quench by form TiC with Ti.For fully guaranteeing this effect, need to contain the C more than 0.10%.On the other hand, C increases the hardness of HAZ, and its result can cause producing welding crack.Therefore, capping is set as 0.10～0.20% with the content of C.The content of C is preferably more than 0.12% and below 0.18%.
Si：0.01～0.30％
Si is to the effective element of the depickling of steel, also helps to improve hardenability.In order to ensure these effects, need to contain the Si more than 0.01%.On the other hand, if the content of Si exceeds 0.30%, then not only above-mentioned effect is saturated, and can cause the low of high-temperature ductility.Therefore, the content with Si is set as 0.01～0.30%.The content of Si is preferably below 0.25%.
Mn：1.00～2.30％
Mn has the effect that improves tensile strength by improving hardenability.In order to obtain this effect, the content that need to make Mn is more than 1.00%.On the other hand, if the content of Mn is excessive, the hardness of HAZ is increased, its result can cause producing welding crack.Therefore, capping is set as 1.00～2.30% with the content of Mn.The content of Mn is preferably more than 1.50% and below 2.00%.
Below the S:0.040%
S is the element that contains as impurity in the steel.In addition, if contain energetically S.Then be combined with Mn and form MnS, have the effect that improves machinability.But, S contain quantitative change many, when particularly exceeding 0.040%, grain boundary segregation and make the toughness drop of mother metal.Therefore, the content with S is set as below 0.040%.In the situation of the toughness of paying attention to mother metal, the expectation of the content of S is below 0.020%, and lowlyer unreasonablely thinks.On the other hand, in the situation that pay attention to machinability, expectation contains the S of 0.020% the amount of exceeding energetically.
Cr：0.10～0.80％
Cr is to improving the effective element of hardenability.In order to obtain this effect, need to contain the Cr more than 0.10%.On the other hand, when the content of Cr is excessive, the hardness of HAZ is increased, its result can cause producing welding crack.Therefore, capping is set as 0.10～0.80% with the content of Cr.The content of Cr is preferably more than 0.20% and below 0.60%.
Al：0.010～0.080％
Al is added as de-acidying agent.In order to obtain this effect, need to contain the Al more than 0.010%.But, exceeding 0.080% Al even contain, its effect also can be saturated, also can increase cost of alloy.Therefore, the content with Al is set as 0.010～0.080%.
B：0.0002～0.0050％
B is to improving the very important element of hardenability.In order to obtain this effect, need to contain the B more than 0.0002%.On the other hand, when the content of B exceeds 0.0050%, not only can make hardenability improve effect saturated, but also cost is uprised.Therefore, capping is set as 0.0002～0.0050% with the content of B.The content of B is preferably below 0.0030%.
Ti：0.010～0.080％
Ti is the important element among the present invention.That is, Ti preferentially is combined with free N and is formed TiN, can prevent from thus the effective B of hardenability is combined with N.In addition, above-mentioned TiN works as the pinning particle, has the coarse grains of the HAZ when suppressing welding, the effect of raising toughness.And then Ti is combined with C and is formed TiC.Above-mentioned TiC also works as the pinning particle, when being used for the heating of quenching to the temperature of 900 ℃ of front and back, have the austenite crystal that suppresses mother metal thickization, improve the effect of toughness.In order to obtain these effects, need to contain the Ti more than 0.010%.But, when the content of Ti too much exceeds 0.080%, form thick TiN, make the toughness drop of mother metal.Therefore, the content with Ti is set as 0.010～0.080%.The content of Ti is preferably more than 0.020% and below 0.060%.
N：0.0020～0.0080％
N is the important element among the present invention.That is, as mentioned above, N is combined with Ti and the TiN that forms works as the pinning particle, and the coarse grains of the HAZ when suppressing welding improves toughness.In order to obtain this effect, need to contain the N content more than 0.0020%.On the other hand, N contain quantitative change when many, form BN and make the hardenability of B improve effect to reduce.And then excessive N forms thick TiN, makes the toughness drop of mother metal.Therefore, capping is set as 0.0020～0.0080% with the content of N.
Heat forged of the present invention is with having following chemical constitution in rolling bar steel or the wire rod: except above-mentioned element, surplus is made of Fe and impurity, the content of P in the impurity, Cu, Ni, Mo and V is controlled as described below, and the fn1 shown in the above-mentioned formula (1) is more than 0.001, the Ceq shown in the formula (2) is below 0.57, the DI shown in the formula (3) is 70～170.
Below the P:0.040%
P is the element that contains as impurity in the steel, its contain quantitative change many, when particularly exceeding 0.040%, grain boundary segregation and make the toughness drop of mother metal.Therefore, the content with the P in the impurity is set as below 0.040%.The content of P in the impurity is preferably below 0.030%.
Cu: less than 0.10%
Cu is included in the steel with the form of trace with impurity sometimes, similarly affects hardenability with C, Si, Mn and Cr, improves hardenability.When hardenability was superfluous, therefore the toughness drop of mother metal need to make the content of Cu few as much as possible.Therefore, the content with the Cu in the impurity is set as less than 0.10%.
Ni: less than 0.10%
Ni is included in the steel with the form of trace with impurity sometimes, similarly affects hardenability with C, Si, Mn and Cr, improves hardness and the hardenability of HAZ.When the hardness of HAZ uprised, the danger that produces welding crack became large, when hardenability is superfluous, and the toughness drop of mother metal.Therefore, need to make the content of the Ni in the impurity few as much as possible, be set as less than 0.10%.
Mo: less than 0.05%
Mo is included in the steel with the form of trace with impurity sometimes, similarly affects hardness and the hardenability of HAZ with C, Si, Mn and Cr, improves hardness and the hardenability of HAZ.When the hardness of HAZ uprised, the danger that produces welding crack became large, when hardenability is superfluous, and the toughness drop of mother metal.Therefore, need to make the content of the Mo in the impurity few as much as possible, be set as less than 0.05%.
Below the V:0.01%
V is included in the steel with the form of trace with impurity sometimes, similarly affects the hardness of HAZ with C, Si, Mn and Cr, improves the hardness of HAZ.When the hardness of HAZ uprised, the danger that produces welding crack uprised.Therefore, need to make the content of the V in the impurity few as much as possible, be set as below 0.01%.
More than the fn1:0.001
Ti is combined with N than C is preferential.Therefore, in using TiN and the two the present invention as the pinning particle of TiC, need to contain the Ti of the amount of being combined with N and C both sides.
Fn1, namely,
fn1＝Ti-3.4N…(1)
The value shown in the following formula less than 0.001 situation under, can't guarantee the Ti of the abundant amount of being combined with C, so the pinning effect of TiC becomes insufficient.Therefore, the fn1 shown in the above-mentioned formula (1) is set as more than 0.001.At the content of Ti be the content of set upper limit 0.080% of the present invention, N in 0.0020% situation of this lower limit, fn1 can be 0.073.
Below the Ceq:0.57
Have or not the generation welding crack to depend on Hmax (maximum hardness of HAZ), exceed at Hmax at 400 o'clock with the HV sclerometer, easily produce welding crack.And the Ceq shown in Hmax and the following formula (2) has dependency.
Hmax＝583×Ceq+65
Ceq＝C+(Si/24)+(Mn/6)+(Ni/40)+(Cr/5)+(Mo/4)+(V/14)…(2)。
Therefore, in order to suppress the generation of welding crack, as long as make Hmax=583 * Ceq+65≤400.
Therefore, according to Ceq≤335/583=0.57, the Ceq shown in the above-mentioned formula (2) is set as below 0.57.Be that Ceq can be 0.29 in the situation of the lower value stipulated among the present invention at the content of each element.
DI：70～170
Quenching-thermal treatment of tempering after, especially in (particularly after the tempering under 475 ℃) after the tempering under 400～500 ℃, DI, namely
DI＝25.4×0.311×C
0.5×(1+0.64×Si)×(1+4.10×Mn)×(1+2.83×P)×(1-0.62×S)×(1+2.33×Cr)×(1+0.52×Ni)×(1+3.14×Mo)×(1+0.27×Cu)×{1+1.50×(0.90-C)}…(3)
Value shown in the following formula can't be guaranteed sufficient intensity (tensile strength is more than the 800MPa) less than 70 o'clock.On the other hand, become large and exceed at 170 o'clock at above-mentioned DI, the hardness of mother metal becomes too high, the toughness drop of mother metal.Therefore, the DI shown in the above-mentioned formula (3) is set as 70～170.
(B) size of Ti precipitate and separate out density:
Ti precipitate among the present invention is TiN, TiC and Ti (C, N).TiN is the precipitate of separating out at high temperature, and on the other hand, TiC and Ti (C, N) are the precipitates of separating out at low temperature.When high temperature is separated out TiN, by having the crystalline structure identical with the TiC that separates out at low temperature and Ti (C, N) etc., be difficult to obtain the density of separating out separately.But the TiN in known these Ti precipitates takes hexahedral form.Therefore, the inventor observes form and the size of the bar steel behind the hot rolling having been investigated the Ti precipitate by transmission electron microscope.Its result is: in the situation that diameter of equivalent circle is more than the 0.07 μ m, most Ti precipitate has corner angle, in the situation that diameter of equivalent circle is below the 0.05 μ m, almost not observing the Ti precipitate has corner angle.Therefore, consider to separate out TiN that diameter of equivalent circle is the Ti precipitate more than the 0.07 μ m, to separate out TiC or the Ti (C, N) that diameter of equivalent circle is the Ti precipitate below the 0.05 μ m at low temperature at high temperature, both density of separating out is stipulated.
(B-1) diameter of equivalent circle be 0.07～1.0 μ m the Ti precipitate size and separate out density:
Even TiN can solid solution when the heating that is used for heat forged, during the heating that is used for quenching yet in matrix.Therefore, the bar steel behind hot rolling or the stage of wire rod, adjust the size of TiN and separate out density, when welding, utilize the pinning effect of TiN to suppress the coarse grains of HAZ.
If bar steel behind hot rolling or the stage of wire rod are at 100 μ m
2Area in separate out the Ti precipitate that 10 above diameter of equivalent circle are 0.07～1.0 μ m, then the coarse grains of HAZ is inhibited, and easily makes HAZ guarantee good toughness.
That is, when welding, HAZ is heated to and exceeds 1200 ℃ high temperature.But, even under high temperature so, diameter of equivalent circle be the above Ti precipitate of 0.07 μ m can solid solution yet in matrix, therefore, work as the pinning particle.On the other hand, in the situation that diameter of equivalent circle exceeds 1.0 μ m, excessive and do not have pinning effect.
But the bar steel behind hot rolling or the stage of wire rod are even the size of Ti precipitate is counted 0.07～1.0 μ m with diameter of equivalent circle, if 100 μ m
2Area in do not separate out more than 10, then also make inevitably coarse grains among the HAZ in when welding.
Therefore, heat forged of the present invention is set as at 100 μ m with rolling bar steel or wire rod
2Area in separate out the Ti precipitate that 10 above diameter of equivalent circle are 0.07～1.0 μ m.Even diameter of equivalent circle be 0.07～1.0 μ m the Ti precipitate to separate out density too high, the pinning effect also can be saturated, is better below 1000 therefore.
(B-2) diameter of equivalent circle be 0.01～0.05 μ m the Ti precipitate size and separate out density
TiC works as the pinning particle when being used for the heating of quenching to the temperature of 900 ℃ of front and back, suppresses thickization of austenite crystal.Therefore, help to improve the toughness of mother metal.
In order to give full play to above-mentioned effect, when importantly making fine TiC greatly mainly with the heating of be used for quenching before, the state after the heat forged distributes.
That is, as long as fine TiC is separated out after the front operation of quenching is heat forged mostly.And, for this reason, the starting material before heat forged, be bar steel behind the hot rolling or the stage of wire rod, at 100 μ m
2Area in must separate out the Ti precipitate that 10 above diameter of equivalent circle are 0.01～0.05 μ m.
The Ti precipitate in the bar steel behind hot rolling or the stage of wire rod, diameter of equivalent circle is less than 0.01 μ m if its size is too little, and then the heating when carrying out heat forged to the temperature of 1200 ℃ of front and back can make this Ti precipitate solid solution in matrix.Therefore, can't when being used for the heating of quenching, guarantee pinning effect.On the other hand, in the above-mentioned stage, if the size of Ti precipitate exceeds 0.05 μ m in diameter of equivalent circle, residual thick Ti precipitate when the heating of be used for quenching then, the quantity of fine Ti precipitate reduces, so the pinning effect is not enough.Therefore, bring into play effect as the pinning particle in order to make the Ti precipitate when being used for the heating of quenching, the bar steel behind hot rolling or the stage of wire rod, this size must be as 0.01～0.05 μ m take diameter of equivalent circle.
But the bar steel behind hot rolling or the stage of wire rod are even the size of Ti precipitate is counted 0.01～0.05 μ m with diameter of equivalent circle, if at 100 μ m
2Area in do not separate out more than 10, then can't when the heating of be used for quenching, suppress thickization of austenite crystal.
Therefore, heat forged of the present invention is set as at 100 μ m with rolling bar steel or wire rod
2Area in separate out the Ti precipitate that 10 above diameter of equivalent circle are 0.01～0.05 μ m.Even diameter of equivalent circle be 0.01～0.05 μ m the Ti precipitate to separate out density too high, the pinning effect also can be saturated, is better below 1000 therefore.
(C) heat forged is with the manufacture method of rolling bar steel or wire rod
Heat forged of the present invention shown in above-mentioned (1) for example can be made with the manufacture method of rolling bar steel or wire rod by the heat forged shown in above-mentioned (2) with rolling bar steel or wire rod.
Particularly, be that the molten steel of above-mentioned to having (A) described chemical constitution under 2.0 ℃/ the condition more than the min casts continuously in speed of cooling,
This slab is heated to the temperature range more than 1100 ℃ and keeps more than the 30min, and under the condition that satisfies following formula (4), carry out breaking down and bar steel is rolling or rod rolling, and be cooled to 800～600 ℃ temperature range after the rolling or rod rolling with the speed of cooling of 5～100 ℃/min at bar steel, can make thus heat forged with rolling bar steel or wire rod.
Y＝(T
1+273)×log(t
1+t
2T
(2))≤7.5×10
3…(4)。
T in the above-mentioned formula (4) represent take " ℃ " as the Heating temperature of unit, the hold-time take " s " as unit when t is illustrated in Heating temperature T, subscript 1 expression breaking down operation, subscript 2 expression bar steel rolling process or rod rolling operations, T (2)=(T
2+ 273)/(T
1+ 273).
As mentioned above, the temperature during above-mentioned each processed and speed of cooling all refer to be take the surface temperature and the speed of cooling of benchmark.
Speed of cooling during (C-1) about the continuous casting of molten steel
TiN separates out when the cooling of continuous casting.And, bar steel behind hot rolling or the stage of wire rod, for set for the diameter of equivalent circle with above-mentioned (B-1) described pinning effect be 0.07～1.0 μ m the Ti precipitate separate out density, be to cast continuously melting steel under 2.0 ℃/ condition min more than in speed of cooling preferably.Owing to when increasing speed of cooling, having limit, therefore preferred scope be 50 ℃/below the min.
If speed of cooling is slower, the TiN that then separates out when the cooling of continuous casting grows in its process of cooling, is difficult at 100 μ m
2Area in separate out the Ti precipitate that 10 above diameter of equivalent circle are 0.07～1.0 μ m.
Speed of cooling during continuous casting refers to after the temperature range that TiN separates out, steel solidify the speed of cooling to 1000 ℃.
(C-2) about breaking down, hot pin steel rolling, rod rolling
In order to alleviate the segregation of slab, expectation improves the Heating temperature when rolling slab and prolongs hold-time under this Heating temperature usually.
But in the situation that prolong the above-mentioned hold-time, thickization of TiN aggegation is difficult at 100 μ m
2Area in separate out the Ti precipitate that 10 above diameter of equivalent circle are 0.07～1.0 μ m.Therefore, the effect that causes utilizing the pinning effect of TiN to suppress the coarse grains of HAZ in when welding disappears.
The Heating temperature of slab is set as more than 1100 ℃, and for until central part thermally equivalent and the hold-time under this Heating temperature is set as more than the 30min, if under the condition of above-mentioned formula (4), carry out on this basis breaking down and bar steel is rolling or rod rolling, thickization of aggegation that then can suppress TiN, the coarse grains of the HAZ in the time of can easily suppressing to weld thus.
Below, formula (4) is described.
The degree of the Ostwald ripening of TiN (Ostwald ripening) can affect Heating temperature T (℃) and t heat-up time (s).For this reason, consider the Ostwald ripening degree of TiN is put in order with tempering parameter " (T+273) * log (t) ".
Bar steel or wire rod are usually with breaking down and bar steel is rolling or the rolling process in these two stages of rod rolling is made slab.
Below, be elaborated with the example that is fabricated to of bar steel.
Heating temperature in breaking down operation and the bar steel rolling process is being made as respectively T
1(℃) and T
2(℃), the hold-time under above-mentioned Heating temperature is set as respectively t
1(s) and t
2(s) time, the tempering parameter in rolling process separately is " (T
1+ 273) * logt
1" reach " (T
2+ 273) * logt
2".
The Heating temperature T in the breaking down operation is obtained in trial
1(℃) required time x (s) during the Ostwald ripening of the TiN that equates of the Ostwald ripening of the TiN that occurs during the lower heating that occurs with the bar steel rolling process.
Tempering parameter (the T of the Ostwald ripening of the TiN in the bar steel rolling process
2+ 273) * logt
2Can use the Heating temperature T of breaking down operation
1(℃) represent like that suc as formula (a).
(T
2+273)logt
2＝(T
1+273)logx…(a)。
If T (2)=(T
2+ 273)/(T
1+ 273), then at the Heating temperature T of breaking down operation
1(℃) required time x (s) can represent like that suc as formula (b) during the Ostwald ripening of the TiN that equates of the Ostwald ripening of the TiN that occurs during the lower heating that occurs with the bar steel rolling process.
x＝t
2 T(2)…(b)。
By with the Heating temperature T in the breaking down operation
1(℃) and temperature T
1(℃) under hold-time x (s) be illustrated in Heating temperature T
2(℃), the heating hold-time t
2(s) the Ostwald ripening degree of the TiN that occurs in the bar steel rolling process, thereby the Ostwald ripening degree Y of the TiN of this twice rolling process of breaking down operation and bar steel rolling process can be represented shown in formula (c) like that by the parameter of 1 breaking down operation, and with in formula (b) the substitution formula (c), can obtain thus formula (d).
Y＝(T
1+273)×log(t
1+x)…(c)、
Y＝(T
1+273)×log(t
1+t
2 T(2))…(d)。
The size of parameter Y, the TiN of the formula (d) of so trying to achieve and the relation of separating out number have been carried out probe, and the result is: if the value of Y is 7.5 * 10
3Below, then can obtain the rolling bar steel of the heat forged that the present invention relates to shown in above-mentioned (1).
In sum, stipulated the parameter of formula (4) as the Ostwald ripening degree of expression TiN.
Y＝(T
1+273)×log(t
1+t
2 T(2))≤7.5×10
3…(4)。
Even the value of Y is in the specialized range, from energy-conservation viewpoint, the Heating temperature of breaking down operation and bar steel rolling process also is preferably set to below 1300 ℃, more preferably is set as below 1270 ℃.In addition, even the value of Y is in the specialized range, from energy-conservation viewpoint, also be preferably set to below the 18000s (300min) in the hold-time under the above-mentioned Heating temperature of breaking down operation and bar steel rolling process, more preferably be set as below the 14400s (240min).From the viewpoint of productivity, the value of Y is preferably 4.0 * 10
3Above.
The parameter Y of the Ostwald ripening degree of the expression TiN shown in the above-mentioned formula (d) is the general situation of making bar steel with breaking down and the rolling process in rolling two stages of bar steel.
The parameter Y ' of the Ostwald ripening degree of the TiN when expression is rolled the number of times of operation with i stage can represent like that suc as formula (e), at this moment, if the value of Y ' is 7.5 * 10
3Below, then can obtain the rolling bar steel of the heat forged that the present invention relates to shown in above-mentioned (1).
Y’＝(T
1+273)×log{∑(t
i T(i))}…(e)。
At this, T (i)=(T
i+ 273)/(T
1+ 273).
Making in the situation of slab with breaking down and the rolling process in two stages of rod rolling, the situation of number of times that is rolled operation with i stage is same as described above.
(C-3) cooling after or the rod rolling rolling about bar steel
Bar steel behind hot rolling or the stage of wire rod, the Ti precipitate that above-mentioned in order to be set as (B-2) described diameter of equivalent circle with pinning effect is 0.01～0.05 μ m separate out density, preferably be cooled to 800～600 ℃ temperature range after or the rod rolling rolling at bar steel with the speed of cooling of 5～100 ℃/min.
When speed of cooling was too fast, TiC did not all separate out, and on the other hand, crossed when slow in speed of cooling, and therefore the TiC aggegation of separating out and growth all are difficult in either case at 100 μ m
2Area in separate out the Ti precipitate that 10 above diameter of equivalent circle are 0.01～0.05 μ m.
Below, utilize embodiment that the present invention is described more specifically, but the present invention is not limited to these embodiment.
[embodiment]
Utilize 70 tons of steel 1～14 shown in the converter melting table 1, utilize under the conditions shown in Table 2 continuous casting to make slab after, the steel disc of 180mm * 180mm is carried out breaking down, carry out again afterwards bar steel rolling, make the bar steel of diameter 54mm.
Steel 1～7 in the table 1 and steel 12～14th, the steel of the inventive example of chemical constitution in the scope of the present invention's regulation.On the other hand, steel 8～11st, the steel of the comparative example of chemical constitution beyond defined terms of the present invention.
Be the density of separating out that the bar steel of 54mm has been investigated TiN and TiC to the diameter of making as described above.
That is (" R " represents radius from the R/2 section of the bar steel of diameter 54mm, to utilize replication (extraction replica method).) the vertical section take sample, utilize and to observe with the transmission electron microscope of energy dispersion type x-ray analysis equipment (EDX), thereby the density of separating out of Ti precipitate is investigated.
Particularly, observe 20 visuals field with 40000 times multiplying powers, calculate the area of Ti precipitate by image analysis, and it is converted into round area, obtain diameter of equivalent circle.
Then, it is the number of the Ti precipitate of 0.07～1.0 μ m that number goes out diameter of equivalent circle, and it is converted into per 100 μ m
2The number of area.Similarly, it is the number of the Ti precipitate of 0.01～0.05 μ m that number goes out diameter of equivalent circle, and it is converted into per 100 μ m
2The number of area.
And then, the bar steel of above-mentioned diameter 54mm at 1200 ℃ of heating 30min, is carried out heat forged and makes the pole of diameter 36mm.Then, the pole of this diameter 36mm in 900 ℃ of heating 1h heating, is carried out water quenching, afterwards, 475 ℃ of tempering of carrying out 1h.
The pole of the heat treated diameter 36mm of above-mentioned quenching-tempering has been carried out in use, implements tension test, shock test and HRC measurement of hardness.
With regard to tension test, the 14A test film of taking JIS Z2201 (1998) regulation from the R/2 section of the pole of diameter 36mm (wherein, parallel portion diameter: 5mm), utilize usual method to carry out tension test at 25 ℃, measure tensile strength (TS).Target TS is set as more than the 800MPa.
With regard to shock test, the U breach standard shock test sheet of taking JIS Z 2242 (2005) regulations from the R/2 section of the pole of diameter 36mm (wherein, notch depth is that 2mm and breach bottom radius are 1mm), under 25 ℃ and-40 ℃, carry out Charpy impact test, measure impact value.The target impact value is set as 160J/cm under 25 ℃
2Above, under-40 ℃, be set as 135J/cm
2Above.
With regard to the HRC measurement of hardness, the pole of cross-section above-mentioned diameter 36mm grinds and makes it become plane was seized cutting the cross section, and 4 in R/2 section and 1 of central part are carried out the HRC measurement of hardness, and above-mentioned 5 arithmetical av is set as HRC hardness.
And then the R/2 section of the pole of the diameter 36mm after the thermal treatment of carrying out above-mentioned quenching-tempering takes the test film of the lap joint welding usefulness put down in writing among Fig. 2 according to position relationship shown in Figure 1, carry out as shown in Figure 3 the lap joint welding.
Relevant welding conditions is set as voltage 20V, electric current 180A, welding speed 40cm/min under the MAG welding, welding line uses can 800MPa level (ER110S-G of AWS A5.28 (2005)).And at first investigation has or not welding crack, then, and the grain size number of investigation HAZ.And then the HV hardness of mensuration HAZ is estimated Hmax (maximum hardness of HAZ).
Have or not welding crack to judge by soaking into defect detecting test.
With regard to the evaluation method of the grain size number of HAZ, at first, the test material that will carry out the lap joint welding vertical disconnected 2 is divided into 12.5mm in the width central position, so that becoming the mode of the central part of length direction, welding metal cuts into 30mm in the vertical section again, imbed in the resin, carry out mirror ultrafinish.Then, corrode with the picric acid saturated aqueous solution that has added tensio-active agent, as shown in Figure 4, for the epimere of overlapping 2 test film, be that the position finding of 1.5mm is apart from the old austinite grain size in the place of welding metal 0.3mm in the central authorities of thickness 3mm.Old austenite crystal take grain size number as more than 3.0 as target.
With regard to the evaluation method of the HV hardness of HAZ, the sample of imbedding resin that uses in the grain size number mensuration is ground once again, as shown in Figure 5, epimere for overlapping 2 test film, measure from the end to end of the cut-out product of 30mm take the spacing of 0.5mm thickness as the central authorities of 3mm be the HV hardness of the position of 1.5mm, for the hypomere of overlapping 2 test film, measure the HV hardness of the position of 1.0mm above the distance test (DT) sheet with the spacing of 0.5mm from the end to end of the cut-out product of 30mm.The target of Hmax is set as below 400 with the HV sclerometer.
Conclude in the table 3 each above-mentioned investigation result is shown.
As shown in Table 3, the steel 1～7 in the scope of using chemical constitution to stipulate in the present invention and at 100 μ m
2Area in separate out respectively in the situation of test number 1～7 of Ti precipitate of two kinds of diameter of equivalent circle stipulating among the present invention more than 10, Hmax all is lower than 400 with the HV sclerometer, therefore produces welding crack, and the intensity of mother metal and tenacity excellent.And then in the situation that above-mentioned test number, the old austinite grain size of HAZ number increases to 3.6～4.1 (in other words, old austenite crystal is little), and therefore, the toughness of inferring HAZ is also excellent.
Relative therewith, in the situation of the test number 8～14 of " comparative example " that do not satisfy simultaneously the full terms of stipulating among the present invention, have problems in any one of the toughness of the toughness of the intensity of welding crack, mother metal, mother metal, HAZ at least.
That is, in the situation that test number 8, the fn1 of used steel 8 is " 0.015 ", in the present invention outside the defined terms.Therefore, diameter of equivalent circle be 0.01～0.05 μ m the Ti precipitate separate out density in the present invention beyond the defined terms, the toughness variation of mother metal.
In the situation that test number 9, the Ceq of used steel 9 increases to 0.59, in the present invention beyond the defined terms.Therefore, Hmax increases to 419 with the HV sclerometer, exceeds 400.Therefore, produce welding crack.
In the situation that test number 10, the DI of used steel 10 increases to 172, in the present invention beyond the defined terms.Therefore, the toughness variation of mother metal.
In the situation that test number 11, the DI of used steel 11 is reduced to 66, in the present invention beyond the defined terms.Therefore, the tensile strength of mother metal is low.
In the situation that test number 12 and test number 13, used steel 12 and the chemical constitution of steel 13 be all in the present invention in the scope of regulation, but diameter of equivalent circle be 0.07～1.0 μ m the Ti precipitate separate out density in the present invention beyond the defined terms.Therefore, the old austinite grain size of HAZ number is reduced to respectively 2.3 and 2.2 (in other words, old austenite crystal is large), the toughness variation of inferring HAZ.
In the situation that test number 14, in the scope that the chemical constitution of used steel 12 is stipulated in the present invention, diameter of equivalent circle be 0.01～0.05 μ m the Ti precipitate separate out density in the present invention outside the defined terms.Therefore, the toughness variation of mother metal.
Utilizability on the industry
Heat forged of the present invention can be welded with rolling bar steel or wire rod, and the intensity of mother metal and tenacity excellent, and the toughness of HAZ is also excellent, therefore can be suitable as the starting material of the running gear parts of the automobile such as axletree.
Claims (2)
1. a heat forged is characterized in that with rolling bar steel or wire rod,
Have following chemical constitution: % contains in quality
C：0.10～0.20％、
Si：0.01～0.30％、
Mn：1.00～2.30％、
Below the S:0.040%,
Cr：0.10～0.80％、
Al：0.010～0.080％、
B：0.0002～0.0050％、
Ti:0.010～0.080% and
N：0.0020～0.0080％，
Surplus is made of Fe and impurity,
P in the impurity, Cu, Ni, Mo and V are restricted to
Below the P:0.040%,
Cu: less than 0.10%,
Ni: less than 0.10%,
Mo: less than 0.05% and
Below the V:0.01%,
And the fn1 shown in the following formula (1) is more than 0.001, the Ceq shown in the formula (2) is below 0.57, the DI shown in the formula (3) is 70～170;
And, for heat forged for rolling bar steel or wire rod, at 100 μ m
2Area in separate out Ti precipitate and 10 Ti precipitates that above diameter of equivalent circle is 0.01～0.05 μ m that 10 above diameter of equivalent circle are 0.07～1.0 μ m;
fn1＝Ti-3.4N…(1)
Ceq＝C+(Si/24)+(Mn/6)+(Ni/40)+(Cr/5)+(Mo/4)+(V/14)…(2)
DI＝25.4×0.311×C
0.5×(1+0.64×Si)×(1+4.10×Mn)×(1+2.83×P)×(1-0.62×S)×(1+2.33×Cr)×(1+0.52×Ni)×(1+3.14×Mo)×(1+0.27×Cu)×{1+1.50×(0.90-C)}...(3)
Above-mentioned Ti, N, C, Si, Mn, Ni, Cr, Mo, V, P, S and Cu in various represents the content in quality % of each element;
Above-mentioned Ti precipitate refers to TiN, TiC and Ti (C, N).
2. a heat forged is characterized in that with the manufacture method of rolling bar steel or wire rod,
Be under 2.0 ℃/ the condition more than the min the molten steel with chemical constitution claimed in claim 1 to be cast continuously in speed of cooling,
Be heated to this slab in the temperature range more than 1100 ℃ and keep more than 30 minutes, and under the condition that satisfies following formula (4), carry out breaking down, and carry out the rolling or rod rolling of bar steel, and after carrying out the rolling or rod rolling of bar steel, be cooled to the speed of cooling of 5～100 ℃/min in 800～600 ℃ the temperature range ,≤
Y＝(T
1+273)×log(t
1+t
2 T(2))≤7.5×10
3…(4)
T in the above-mentioned formula (4) represent take " ℃ " as the Heating temperature of unit, the hold-time take " s " as unit when t is illustrated in Heating temperature T, subscript 1 expression breaking down operation, subscript 2 expression bar steel rolling process or rod rolling operations, T (2)=(T
2+ 273)/(T
1+ 273).
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| PCT/JP2011/066365 WO2012011469A1 (en) | 2010-07-20 | 2011-07-19 | Rolled steel bar or wire for hot forging |
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| CN105121685A (en) * | 2013-04-10 | 2015-12-02 | 新日铁住金株式会社 | Case-hardening steel material and case-hardening steel member |
| CN106991280A (en) * | 2017-03-30 | 2017-07-28 | 江阴兴澄特种钢铁有限公司 | A kind of computational methods of boron-containing steel ideal critical diameter |
| CN107723605A (en) * | 2017-11-30 | 2018-02-23 | 攀钢集团攀枝花钢铁研究院有限公司 | Steel Bar and its LF stove production methods are built containing Ti, Cr microalloy |
| CN109182910A (en) * | 2018-10-20 | 2019-01-11 | 江苏铸鸿锻造有限公司 | A kind of carbon manganese steel forging circle of low-temperature impact-resistant and preparation method thereof |
| CN110337504A (en) * | 2017-02-24 | 2019-10-15 | 日本制铁株式会社 | Bar steel is used in hot forging |
| CN112983968A (en) * | 2014-02-26 | 2021-06-18 | 日本制铁株式会社 | Axle for railway |
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| CN102796950A (en) * | 2012-08-08 | 2012-11-28 | 内蒙古包钢钢联股份有限公司 | Production method of large-scale high strength 82B high-carbon hard wire rod |
| CN103334049A (en) * | 2013-04-11 | 2013-10-02 | 内蒙古包钢钢联股份有限公司 | High carbon hard wire rod production method |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH1143737A (en) * | 1997-07-23 | 1999-02-16 | Nippon Steel Corp | Cold forging steel excellent in grain coarsening preventing property and cold forgeability, and its production |
| JP2001098340A (en) * | 1999-09-29 | 2001-04-10 | Nippon Steel Corp | Steel for welding structure excellent in heat-affected zone |
| CN101724780A (en) * | 2008-10-20 | 2010-06-09 | 株式会社神户制钢所 | Thick steel plate |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4347763B2 (en) * | 2004-07-14 | 2009-10-21 | 株式会社神戸製鋼所 | High temperature carburizing steel and method for producing the same |
| JP4699341B2 (en) * | 2006-11-17 | 2011-06-08 | 株式会社神戸製鋼所 | High strength hot forged non-tempered steel parts with excellent fatigue limit ratio |
-
2010
- 2010-07-20 JP JP2010162442A patent/JP5419820B2/en active Active
-
2011
- 2011-07-19 CN CN201180035245.2A patent/CN103003462B/en active Active
- 2011-07-19 WO PCT/JP2011/066365 patent/WO2012011469A1/en active Application Filing
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH1143737A (en) * | 1997-07-23 | 1999-02-16 | Nippon Steel Corp | Cold forging steel excellent in grain coarsening preventing property and cold forgeability, and its production |
| JP2001098340A (en) * | 1999-09-29 | 2001-04-10 | Nippon Steel Corp | Steel for welding structure excellent in heat-affected zone |
| CN101724780A (en) * | 2008-10-20 | 2010-06-09 | 株式会社神户制钢所 | Thick steel plate |
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|---|---|---|---|---|
| CN105121685A (en) * | 2013-04-10 | 2015-12-02 | 新日铁住金株式会社 | Case-hardening steel material and case-hardening steel member |
| CN105121685B (en) * | 2013-04-10 | 2017-03-08 | 新日铁住金株式会社 | Turn to ratch milling round steel material and turn to ratch |
| US9840759B2 (en) | 2013-04-10 | 2017-12-12 | Nippon Steel & Sumitomo Metal Corporation | Rolled round steel material for steering rack bar and steering rack bar |
| CN112983968A (en) * | 2014-02-26 | 2021-06-18 | 日本制铁株式会社 | Axle for railway |
| CN110337504A (en) * | 2017-02-24 | 2019-10-15 | 日本制铁株式会社 | Bar steel is used in hot forging |
| CN110337504B (en) * | 2017-02-24 | 2021-06-15 | 日本制铁株式会社 | Steel bar for hot forging |
| CN106991280A (en) * | 2017-03-30 | 2017-07-28 | 江阴兴澄特种钢铁有限公司 | A kind of computational methods of boron-containing steel ideal critical diameter |
| CN106991280B (en) * | 2017-03-30 | 2020-08-14 | 江阴兴澄特种钢铁有限公司 | Method for calculating ideal critical diameter of boron-containing steel |
| CN107723605A (en) * | 2017-11-30 | 2018-02-23 | 攀钢集团攀枝花钢铁研究院有限公司 | Steel Bar and its LF stove production methods are built containing Ti, Cr microalloy |
| CN109182910A (en) * | 2018-10-20 | 2019-01-11 | 江苏铸鸿锻造有限公司 | A kind of carbon manganese steel forging circle of low-temperature impact-resistant and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2012011469A1 (en) | 2012-01-26 |
| JP2012025972A (en) | 2012-02-09 |
| CN103003462B (en) | 2014-12-31 |
| JP5419820B2 (en) | 2014-02-19 |
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