CN102264935B - Surface decarburization-restrained steel and manufacturing method thereof - Google Patents
Surface decarburization-restrained steel and manufacturing method thereof Download PDFInfo
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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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- 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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
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Abstract
Decarburization-restrained steel and manufacturing method thereof are disclosed. Steel includes a boron (B)-concentrated layer formed on its surface to prevent carbon of the steel from being in contact with oxygen in atmosphere to thus restrain decarburization of the steel. The steel includes a boron-concentrated layer with a thickness of 3mu m or larger formed on the surface of the steel. The method of manufacturing decarburization-restrained steel includes cooling steel containing 0.001 wt% to 0.02 wt% of boron (B) at a cooling speed of 0.5 /s to 25 /s at an austenite + ferrite two-phase region.
Description
Technical field
The present invention relates to steel and the manufacture method thereof of surface decarburization-restrained, more specifically, relate to following steel, it comprises boron (B) enriched layer forming on its surface, to prevent that carbon contained in steel from contacting with the oxygen in atmosphere, thereby suppress steel decarburization, the invention still further relates to the manufacture method of described steel.
Background technology
Recently, for effectively using the limited mineral fuel energy and guaranteeing that economic benefit leads over the oil price skyrocketing, the intensity of steel need to be in higher level.Provide the steel of high level intensity can reduce the quantity of the required steel constituent of the various products of manufacture and make described various product there are Premium Features, this may be able to make the product that oil consumption is large (for example automobile) the more mileage (fuel efficiency) of travelling, thereby greatly reduce energy expenditure.
For guaranteeing hardness of steel, carbon is one of element the most conventionally adding, and particularly, the steel that trolley part is used contains than the more substantial carbon of certain predeterminated level.But in the manufacture of High Strength Structural Steel that is typically used as trolley part material etc., the upper layer of steel may decarburization.That is, when the high austenite structure of Carbon Solubility is transformed into the low ferritic structure of Carbon Solubility, the activity of carbon increases, and in the case, highly active carbon can contact with oxidisability atmosphere on the surface of steel, thereby reacts and produce decarburization phenomenon.In other words, decarburization phenomenon usually occurs in material while heat-treating under high temperature range, and now carbon can fully spread, thereby makes the carbon existing in steel by diffusion, move quickly into the upper layer of steel, then contacts with the oxidizing gas in atmosphere.In the manufacture of High Strength Structural Steel, the existence that surface imperfection tissue---shows as the Decarburized structure that decarburizating that the upper layer by material brings out produces---causes various problems.That is, the Decarburized structure existing on surface is compared with body material, has quite low hardness and solidity to corrosion, and the function variation of the steel that therefore contains Decarburized structure is not enough to as High Strength Structural Steel.; if High Strength Structural Steel stands continuously fatigue repeatedly and forms this surface decarburization layer, this surface decarburization layer can serve as the starting point that crackle produces and propagates, and causes critical problem; for example material lifetime shortens, i.e. material problem such as rapid inefficacy after manufacturing.
Therefore, it is believed that and material is remained on in high temperature range, to carry out human failure be a kind of method that suppresses steel decarburization in manufacturing processed.But this material must pass through high temperature manufacturing processed, for example rolling or forging, to control the shape of metal and to guarantee the quality of material, therefore, avoids decarburizing reaction by no means easy, and effectively suppressing decarburization is key point.
In addition, because the high intensity level of material will realize unit cost is increased in minimized limit, in the prior art all, in most of the cases, can in High Strength Structural Steel, add silicon (Si), a kind of alloying element of low price.But, the same carbon of silicon (Si) (C), be a kind of tetrels, have and similarly behavior of carbon (C), it not only can increase the activity of carbon (C), but also can stablize ferrite region, make ferritic free in formation, thereby reduce the solubleness of carbon (C).; add silicon (Si) and expanded the so-called two phase region that austenite and ferrite coexist, and in this case, accelerated the escape of carbon that oxidation the causes upper layer from the part of steel surface; thereby through large two phase region, promote decarburizing reaction through long-time.
In making great efforts the process of the described problem of solution, brought into use a kind of cooling mode of controlling to avoid fast the adjacent domain of the two phase region of decarburization strengthening to be introduced into use.But, due to the difference of pile density in material cooled process (piling density), be difficult to temperature deviation in control coil etc., particularly, temperature deviation during coil overlapping portion grades is even more serious, makes to be difficult to fully to suppress the booming decarburization of part.In addition, for for realizing for the high silicon steel that high strength contains a large amount of silicon, the temperature cross section of two phase region is compared with general steel greatly and is expanded, and this can only be avoided by controlling speed of cooling, therefore in the urgent need to exploitation, can substantially suppress the steel of its Decarburization Sensitivity.
For this reason, studied a kind of method, wherein, Xiang Gangzhong adds oxide skin (scale) and produces element such as chromium (Cr), copper (Cu), nickel (Ni) etc., to be increased in high-temperature heating process the density of the oxide skin inevitably producing and to improve it and the adhesivity of body material, thereby prevent contacting between carbon in steel upper layer and oxidizing gas etc.But the problem that the method exists is that the adhesivity between described body material and oxide skin is less, can not suppress decarburizing reaction completely.
As mentioned above, still need exploitation can effectively suppress the steel of its surface decarburization in manufacturing processed.
Summary of the invention
Technical problem
An aspect of of the present present invention provides a kind of following steel, and it comprises a fine and close enriched layer forming on its surface, thereby prevents that the carbon in steel from contacting with oxidisability atmosphere.
Technical scheme
According to an aspect of the present invention, provide a kind of following steel, described ladle is 3 μ m or larger boron enriched layer containing the thickness forming on its surface.
Described boron enriched layer can be one wherein boron content be 10 times or larger region of steel average composition.
Described steel can contain the boron of 0.001wt%-0.02wt%.
Described steel, except described boron component, also can contain the titanium (Ti) of 0.02wt% or nitrogen still less (N) and 0.005wt%-0.5wt%.
Described steel also can contain the carbon (C) of 0.2wt%-1.0wt%, the manganese (Mn) of the silicon (Si) of 0.1wt%-3.5wt%, 0.3wt%-1.0wt%, 0.1wt% or aluminium still less (Al), 0.02wt% or phosphorus still less (P), and 0.02wt% or sulphur still less (S).
Except described component, described steel also can contain the chromium (Cr) of 0.1wt%-1.5wt%, the vanadium (V) of the copper (Cu) of the nickel (Ni) of 0.01wt%-1.0wt%, 0.01wt%-1.0wt%, 0.0020wt% or oxygen still less (O), 0.005wt%-0.5wt%, and the niobium of 0.005wt%-0.5wt% (Nb).
According to a further aspect in the invention, provide a kind of method of manufacturing the limited steel of decarburization, the method comprises: the steel at austenite+ferrite two phase region with the cooling boron (B) containing 0.001wt%-0.002wt% of speed of cooling of 0.5 ℃/s-25 ℃/s.
Except described component, described steel also can contain the titanium (Ti) of 0.02wt% or nitrogen still less (N) and 0.005wt%-0.5wt%.
Described steel also can contain the carbon (C) of 0.2wt%-1.0wt%, the manganese (Mn) of the silicon (Si) of 0.1wt%-3.5wt%, 0.3wt%-1.0wt%, 0.1wt% or aluminium still less (Al), 0.02wt% or phosphorus still less (P), and 0.02wt% or sulphur still less (S).
Except described component, described steel also can contain the chromium (Cr) of 0.1wt%-1.5wt%, the vanadium (V) of the copper (Cu) of the nickel (Ni) of 0.01wt%-1.0wt%, 0.01wt%-1.0wt%, 0.0020wt% or oxygen still less (O), 0.005wt%-0.5wt%, and the niobium of 0.005wt%-0.5wt% (Nb).
Beneficial effect
According to exemplary of the present invention, because described boron enriched layer is formed at the surface of steel, so can prevent that the carbon in steel from contacting with the oxidizing gas in atmosphere, suppressed decarburization thus effectively.
Accompanying drawing explanation
Fig. 1 is for confirming the PTA photo of the formation result of B enriched layer in comparative example 4, exemplary 3 and exemplary 4.
Fig. 2 is for showing the microphotograph of the relation between boron enriched layer, low temperature tissue and the ferrite Decarburized layer based on speed of cooling.
Embodiment
Now exemplary of the present invention is described in detail.
Present inventor forms Decarburized layer recognizing as preventing on steel surface, must prevent from, on basis that carbon component in steel contacts with oxidizing gas in atmosphere, having made the present invention.Particularly, inventor's discovery, boron component can effectively prevent that the carbon component in steel from contacting with the oxidizing gas in atmosphere.
That is, because boron component forms fine and close enriched layer at the upper layer of steel, so its effectively anti-blocking component contact with the oxidizing gas in atmosphere.Especially, compare with conventional oxide skin forming element such as chromium (Cr), copper (Cu), nickel (Ni) etc., even if the boron of less content also can obtain enough effects, and effectively prevent decarburization.In an exemplary of the present invention, boron enriched layer refers to the region forming on wire rod (wire rod) upper layer, and the boron in this region (B) content is greater than boron (B) content in other regions.Described boron enriched layer mainly comprises the outermost oxidation cortex that is positioned at wire rod, and can form certain degree of depth by the wire internal under oxidation cortex depending on situation.Therefore,, in an exemplary of the present invention, it is ten times or the surface region layer that reaches a degree of depth of more times of the average composition of steel that described boron enriched layer is defined as wherein boron (B) content.
According to the result of the research of being undertaken by inventor, described boron enriched layer must have 3 μ m or larger thickness.If described boron enriched layer is too thin, will be easy to segmentation, the infiltration of Sauerstoffatom can not be suitably stoped, thereby the object of the invention cannot be realized.Because described boron enriched layer is generally used for suppressing carbon, contact with oxidizing gas, therefore the upper limit of described boron enriched layer thickness is without special restriction.But, in the case, consider the general content of boron (B), described boron enriched layer is difficult to form the thickness that surpasses 120 μ m.
Therefore according to the ladle of an exemplary of the present invention, containing the thickness forming on described steel surface, be, 3 μ m or larger boron enriched layer.Described boron enriched layer is not only conducive to be suppressed at the decarburization that may occur in follow-up heating and cooling process, and has been advantageously used in the decarburization being suppressed in steel making processes.That is, described enriched layer is easy to form under the temperature range of decarburization or higher temperature at steel, and suppresses steel decarburization in cooling operation.
In addition, any steel is all considered to belong to the category of the steel that an exemplary according to the present invention provides, as long as its surface decarburization is suppressed, therefore, without being particularly limited other components.But, for forming described boron enriched layer, in steel, must contain the boron component of q.s, therefore preferably boron content is limited to certain limit, as described below:
Boron (B): 0.001wt%-0.02wt%
As mentioned above, because boron (B) is the source of described boron enriched layer, therefore, its content is necessary for 0.001wt% or larger.But except forming the effect of enriched layer, boron is also for improvement of the hardening capacity of steel.According to the steel for mechanical structure of an exemplary of the present invention, be required to be soft, thereby implement to forge or upset first being processed has enough workabilitys.Therefore,, if contain excessive boron (B), even if steel is manufactured by annealing (being Slow cooling), also can in steel, disadvantageously form a large amount of low temperature tissues, for example bainite or martensite.Therefore,, in an exemplary of the present invention, the upper limit of boron (B) content is set as 0.02wt%.
The effect that the present invention wishes can obtain by suitably controlling boron (B) content.Therefore, preferably, the ladle of an exemplary of the present invention is 3 μ m or larger boron enriched layer containing a thickness, contains the boron (B) of 0.001wt%-0.02wt% in this layer.
In boron and steel, exist nitrogen component reaction time, generate such as throw outs such as BN.This throw out is used for fixedly boron, prevents that boron diffusion is to the surface of steel.That is, described throw out can prevent from forming boron enriched layer.Therefore, preferably, boron (B) is not to be existed by the state of the fixing so-called effective boron of nitrogen (N) (or free boron).For this reason, for following reason, titanium (Ti) and nitrogen (N) are controlled in following scope comparatively effective.
Nitrogen (N): 0.02wt% or still less
Nitrogen (N) is a kind of gas containing in a large number in atmosphere, accounts for approximately 80% of atmosphere.When nitrogen (N) contacts with molten steel, it can be included in molten steel in large quantities.While containing nitrogen (N) in steel, nitrogen reacts and forms BN with the boron existing in steel, and in the case, and the suppressed and boron (B) of the diffusion of boron (B) is fixed, and is therefore difficult to form enriched layer on steel surface.Therefore, need to limit the content of nitrogen (N).The processing load of considering steelmaking process etc., is limited in the content of nitrogen (N) below 0.02wt%.Preferably, the content of nitrogen (N) is limited in below 0.01wt%.
Titanium (Ti): 0.005wt%-0.5wt%
As mentioned above, preferably nitrogen (N) is restricted to less as much as possible, but considers and process load, can not remove completely.Therefore,, for making in steel the inevitably disadvantageous effect of contained nitrogen (N) minimize, preferably add titanium (Ti).That is, titanium (Ti) can form prior to boron nitride (TiN, Ti (C, N) etc.), so it can suppress the formation of BN, thereby keeps more effectively boron.Consider amount nitrogenous in steel, must comprise 0.005wt% or more titanium (Ti) effectively to guarantee effective boron (B).Content is that the titanium of maximum 0.5wt% can fully play its effect, higher than the titanium (Ti) of the residual content of described content, will cause the increase of unit manufacturing cost etc.
Therefore, according to an exemplary of the present invention, can provide a kind of following steel, wherein the thickness of boron enriched layer and the content of boron are controlled (being conditioned) and contained titanium (Ti) and nitrogen (N) in above-mentioned ratio.Therefore, by meeting described condition, can obtain beneficial effect of the present invention, and irrelevant with other remaining ingredients in steel.
Now to being suitable for realizing the limiting examples of composition of the steel of beneficial effect of the present invention, be described to embody the present invention.; an example of composition that is suitable for obtaining the steel of effect of the present invention can be such composition, wherein boron (B), titanium (Ti) and nitrogen (N) be controlled in above-mentioned scope and carbon (C), silicon (Si), manganese (Mn), aluminium (Al), phosphorus (P), sulphur (S) etc. to form the content range of basic components of steel as follows.
Carbon (C): 0.2wt%-1.0wt%
Carbon (C) is a kind of element for guaranteeing that the intensity of high-strength steel is added.If the content of carbon (C) is less than 0.2wt%, undercapacity has required strength level to guarantee steel.On the contrary, if the content of carbon (C) surpasses 1.0wt%, along crystal boundary, form proeutectoid cementite tissue, cause material crack, significantly reduce fatigue strength.In addition, due to the material decarburization that is difficult to guarantee with the corresponding enough toughness of high strength and is difficult to suppress cause owing to adding silicon (Si), so the content of carbon (C) is preferably restricted to 0.2wt%-1.0wt%.
Silicon (Si): 0.1wt%-3.5wt%
Silicon (Si) is the effect with generation strengthening body material intensity for ferrite.If the content of silicon (Si) is less than 0.1wt%, it cannot bring into play the effect of strengthening body material after for ferrite.Therefore, the lower limit of silicon (Si) need be restricted to 0.1wt%.Meanwhile, if the content of silicon (Si) surpasses 3.5wt%, the possibility that produces center segregation in heat treatment process increases, and the increase of the activity of carbon, thereby has promoted surface decarburization.Therefore the content of silicon (Si) is preferably restricted to 0.1wt%-3.5wt%.
Manganese (Mn): 0.3wt%-1.0wt%
Manganese (Mn) for can be used for guaranteeing a kind of element of hardness of steel when it is included in steel.Therefore,, if the content of manganese (Mn) is less than 0.3wt%, can not realize the intensity that sufficient to guarantee steel has desirable strength level.On the contrary, if the content of manganese (Mn) surpasses 1.0wt%, toughness variation.Therefore, the content of manganese (Mn) is preferably restricted to 0.3wt%-1.0wt%.
Aluminium (Al): 0.1wt% or still less
Adding aluminium (Al) can reduce grain fineness number and improve toughness.But if the content of aluminium (Al) surpasses 0.1wt%, the sedimentary amount of oxide-base of generation increases, and grain fineness number chap, adversely affects fatigue characteristic.In an exemplary of the present invention, aluminium is not the necessary component of steel, therefore the lower limit of aluminium (Al) is set.
Phosphorus (P): 0.02wt% or still less
Phosphorus (P) is separated out and can be reduced toughness in crystal boundary, and therefore, preferably, its content should be the least possible.But, for removing the phosphorus from multiple source contained in steel completely, will inevitably to refining (or tempering) process, apply huge load.Therefore, the level that can make phosphorus is 0.02wt%, and wherein phosphorus can not cause large problem.If refining load is heavy, phosphorus is preferably restricted to 0.01wt% or still less.
Sulphur (S): 0.02wt% or still less
Sulphur (S), a kind of low melting point element, can reduce toughness and produce emulsion at grain boundary segregation, thereby adversely affects the characteristic of high-strength steel.Therefore, preferably, the content of sulphur (S) should be the least possible, but consider treating process load, by the ceiling restriction of sulphur (S), is 0.02wt%.
Therefore, for realizing the example of composition of the steel of beneficial effect of the present invention, it is so a kind of composition, its except by the gauge control of boron enriched layer in above-mentioned scope and the element that comprises OK range for example boron (B), titanium (Ti) and nitrogen (N), also contain the carbon (C) of 0.2wt%-1.0wt%, the manganese (Mn) of the silicon (Si) of 0.1wt%-3.5wt%, 0.3wt%-1.0wt%, 0.1wt% or aluminium still less (Al), 0.02wt% or phosphorus still less (P), and 0.02wt% or sulphur still less (S).
Except said components, an example that is applicable to the composition of steel of the present invention can comprise one or more in the chromium (Cr) of following ranges, nickel (Ni), copper (Cu), oxygen (O), vanadium (V), niobium (Nb) etc., to guarantee the physicals of steel.
Chromium (Cr): 0.1wt%-1.5wt%
Chromium is for preventing a kind of element of surface decarburization and acquisition oxidation-resistance and tempering and softening properties.If the content of chromium (Cr) is less than 0.1wt%, be difficult to obtain enough oxidation-resistances, tempering and softening properties, surface decarburization preventive effect etc.Meanwhile, if the content of chromium (Cr) surpasses 1.5wt%, deformation resistance variation, thus may cause strength decreased.Therefore, the content of preferred chromium (Cr) is 0.1wt%-1.5wt%.
Nickel (Ni): 0.01wt%-1.0wt%
Nickel (Ni) is a kind of for effectively suppressing by forming the oxidation cortex that has a high-adhesiveness with body material the element that surface decarburization is added.In addition, nickel (Ni) can effectively improve the toughness of steel.If the content of nickel (Ni) is less than 0.01wt%, the effect of nickel (Ni) is not enough, and if the content of nickel (Ni) is 1.0wt% or larger, residual austenitic amount increases, thereby has reduced fatigue lifetime.In addition, because nickel (Ni) price is high, so it causes unit manufacturing cost sharply to increase.Therefore, the content of nickel (Ni) need be restricted to 0.1wt%-1.0wt%.
Copper (Cu): 0.01wt%-1.0wt%
Adding copper (Cu) can produce oxidation cortex body material to high-adhesiveness together with nickel (Ni), and this can effectively prevent decarburization and improve corrosion stability.When the content of copper (Cu) is less than 0.01wt%, this effect reduces.Meanwhile, if the content of copper (Cu) surpasses 1.0wt%, can be because embrittlement causes rolling defect.
Oxygen (O): 0.0020wt% or still less
Oxygen (O) is limited in 0.0020wt% or still less.If the content of oxygen (O) surpasses 0.0020wt%, form the nonmetal inclusion compound of thick oxide-base, thereby sharply reduce fatigue lifetime.
Vanadium (V): 0.005wt%-0.5wt%, and niobium (Nb): 0.005wt%-0.5wt%
Vanadium (V) and niobium (Nb) add separately or add together, in order to form carbide/nitride, make throw out sclerosis, thereby improve the strength characteristics of high-strength steel.The content of vanadium (V) and niobium (Nb) is restricted to respectively 0.005wt%-0.5wt%.If the content of vanadium (V) and niobium (Nb) is less, can reduce the precipitation of vanadium (V) and niobium (Nb) base carbide/nitride, grain-boundary strengthening effect and fatigue characteristic can not be substantially improved.If the content of vanadium (V) and niobium (Nb) is larger, unit manufacturing cost sharply increases, the improvement that precipitates caused spring characteristic reaches capacity, and the amount that is not dissolved in the thick alloy carbide of body material in austenite heat treatment process increases, thereby as a kind of nonmetal inclusion compound, reduce fatigue characteristic and precipitation strengthening effect.
The steel that meets above-mentioned condition can be manufactured by conventional hot rolling method.But, the invention provides an example of more effectively manufacturing steel.A kind of effective steel making method now will be described.
Cooling conditions: austenite+ferritic two phase region is cooling with the speed of cooling of 0.5 ℃/s-25 ℃/s.
As mentioned above, decarburizing reaction is conventionally higher by temperature and start to generate ferritic two phase region and occur.Therefore, should generate and can prevent the boron enriched layer that decarburization occurs in described temperature range, to suppress decarburization.Inventor's result of study shows, for obtaining above-mentioned effect, should form the boron enriched layer that is greater than certain thickness and any segmentation does not occur, for this reason, cooling need to be at 0.5 ℃/s or under speed of cooling, implement faster.If cooling, lower than this speed of cooling, implement, even if formed boron enriched layer, its thickness also may be too thin and segmentation, and not enough with the adhesivity of body material, is therefore easy to separated with body material.On the contrary, if speed of cooling is higher, the boron enriched layer forming has enough thickness, but under this high speed of cooling, has formed low temperature tissue in steel, and this is undesirable for the following process of steel.This is because the bainite of delicate tissues or the face integration rate of martensite low temperature tissue are preferably 5% or still less in steel.Therefore, the upper limit of described speed of cooling is set as to 25 ℃/s.More preferably, the upper limit of described speed of cooling is set as to 20 ℃/s.
Before or after cooling operation, can manufacture steel by general steel making method.That is, should notice and it should be understood that those skilled in the art can easily select to increase the course of hot rolling that pressed-steel is controlled steel shape that passes through after cooling operation, or any other course of hot rolling, or other heat treatment processes etc.
embodiment
---wherein show embodiment of the present invention---now with reference to the accompanying drawings and described more fully embodiment of the present invention.But the present invention can multiple different mode realize, and should not be construed as and be limited to embodiment as herein described.Therefore, embodiment of the present invention are not limited to above-mentioned embodiment, and are limited by the four corner of the claims of enclosing and equivalent thereof.
Exemplary
(each component concentration in table 1 represents with weight percent (wt%) will to have separately composition shown in following table 1, but nitrogen (N) and oxygen (O) represent with ppm) each batch of steel cast to manufacture steel billet (forging piece), by steel billet at 700 ℃-1, under the final rolling temperature of 000 ℃ with 60% or the larger draft mode by rod rolling be rolled, then at room temperature by multiple cooling mode as shown in table 2 below, undertaken cooling, thereby make steel.Observe the delicate tissues of the steel of manufacturing under the described conditions.In the case, be quantitative measurment low temperature tissue and decarburized layer deepness, for simplicity, from 30 visuals field, carried out random observation.The detailed value of the low temperature tissue minute rate recording and average ferrite decarburizaed depth is shown in Table 2.
From the visual field more than five to the ferrite Decarburized layer in the carbon cross section of wire rod, measure, and determined mean value.
In addition,, for observe the oxidation cortex of boron in the wire rod of manufacturing under table 1 condition, use particle track radioautograph (PTA) method, by the boron distributional analysis of neutron radiation, test.This method of testing is that, when thermal neutron is radiated through the material of boracic, the heavy ion light producing by nuclear reaction is exposed to secure adhesion in the film of specimen surface.By implementing the method, measure boron enriched layer whether segmentation and under each chemical composition and cooling conditions the mean thickness of this boron enriched layer, and detailed results is shown in table 2 and Fig. 1 and 2.In the case, the low temperature tissue minute rate in table 2 refers to the summation of the face integration rate of bainite and martensite.
Table 1
Table 2
As shown in table 1, comparative example 1-3 is illustrated in due to the composition that lacks boron and be difficult to form each steel under the condition of boron enriched layer.Comparative example 4 and 5 and each exemplary represent to meet the steel of favourable composition proposed by the invention.But, in the case, as shown in table 2, in comparative example 4 and 5, in the desirable scope that the speed of cooling after heating does not limit in the present invention.
As shown in result in table 2, compare with the situation of adding boron, in comparative example 1-3, owing to not adding boron, in cooling operation process, do not form boron enriched layer.Therefore, can not effectively suppress ferrite decarburization, cause producing ferrite decarburization from surface to the darker region of ferritic steel.Especially, in comparative example 3, as the prior art, add components such as copper (Cu), nickel (Ni) to form enriched layer by this component.But can not be prevented the effect that ferrite decarburization occurs.In addition,, in comparative example 4, the composition of steel meets scope of the present invention; But speed of cooling is low reaches 0.3 ℃/s.Because cooling enforcement is slow, boron enriched layer is thinner, and the adhesivity of oxidation cortex and body material reduces, and occurs disjunction everywhere, oxidizing gas element is contacted with carbon by the gap between part, thereby promoted decarburization.In the situation that implement cooling comparative example 5 with the speed of cooling of 30 ℃/s, form the boron enriched layer of approximately 70 μ m, thereby can effectively prevent decarburization by the utmost point.But the face integration rate of low temperature tissue has adversely reached 82%.
Comparatively speaking, in the situation that exemplary 1-4---wherein the addition of boron is that 20ppm to 60ppm and cooling conditions meet the framework of the present definition---, as confirmed in Fig. 1 and table 2 (this figure has only shown the result of exemplary 3 and 4), boron oxidation cortex does not observe any disjunction, and the mean thickness of this oxidation cortex is 3 μ m-120 μ m.In addition, there is Decarburized layer seldom, confirmed that boron enriched layer significantly suppresses ferrite decarburization.
Fig. 2 has shown by observation ferrite Decarburized layer and whether with the formation of boron enriched layer, has produced the microphotograph obtaining.As shown, in the situation that do not form the comparative example 3 of enriched layer, notice, formed the ferrite Decarburized layer of about 50mm having an even surface.The in the situation that of comparative example 5, the boron enriched layer of approximately 70 μ m almost can prevent decarburization, but notices and formed a large amount of low temperature tissues, for example martensite.But Comparatively speaking, in the situation that the exemplary 4 of manufacturing under condition of the present invention prevented ferrite decarburization and almost do not formed low temperature tissue, this has confirmed that this steel is applicable to carrying out post-treatment.
Therefore, can determine that condition of the present invention is favourable.
Claims (9)
1. surface decarburization-restrained steel, it is the boron enriched layer of 3-120 μ m that described steel contains the thickness forming on its surface,
Wherein said boron enriched layer moves to diffuseing to form of steel surface by the boron in steel wherein,
The boron that wherein said steel contains 0.006wt%-0.02wt%, and
Wherein said ladle draws together 5% or bainite or the martensite of face integration rate still less.
2. the steel of claim 1, wherein said boron enriched layer be one wherein boron content be 10 times or larger region of steel average composition.
3. the steel of claim 1, wherein said steel also contains the titanium (Ti) of 0.02wt% or nitrogen still less (N) and 0.005wt%-0.5wt%.
4. the steel of claim 3, wherein said steel also contains the carbon (C) of 0.2wt%-1.0wt%, the manganese (Mn) of the silicon (Si) of 0.1wt%-3.5wt%, 0.3wt%-1.0wt%, 0.1wt% or aluminium still less (Al), 0.02wt% or phosphorus still less (P), and 0.02wt% or sulphur still less (S).
5. the steel of claim 4, wherein said steel also contains the chromium (Cr) of 0.1wt%-1.5wt%, the vanadium (V) of the copper (Cu) of the nickel (Ni) of 0.01wt%-1.0wt%, 0.01wt%-1.0wt%, 0.0020wt% or oxygen still less (O), 0.005wt%-0.5wt%, and the niobium of 0.005wt%-0.5wt% (Nb).
6. manufacture a method for surface decarburization-restrained steel, described method comprises:
Steel at austenite+ferrite two phase region with the cooling boron that contains 0.006wt%-0.02wt% of speed of cooling (B) of 0.5 ℃/s-25 ℃/s, and
Wherein said ladle draws together 5% or bainite or the martensite of face integration rate still less.
7. the method for claim 6, wherein said steel also contains the titanium (Ti) of 0.02wt% or nitrogen still less (N) and 0.005wt%-0.5wt%.
8. the method for claim 7, wherein said steel also contains the carbon (C) of 0.2wt%-1.0wt%, the manganese (Mn) of the silicon (Si) of 0.1wt%-3.5wt%, 0.3wt%-1.0wt%, 0.1wt% or aluminium still less (Al), 0.02wt% or phosphorus still less (P), and 0.02wt% or sulphur still less (S).
9. the method for claim 8, wherein said steel also contains the chromium (Cr) of 0.1wt%-1.5wt%, the vanadium (V) of the copper (Cu) of the nickel (Ni) of 0.01wt%-1.0wt%, 0.01wt%-1.0wt%, 0.0020wt% or oxygen still less (O), 0.005wt%-0.5wt%, and the niobium of 0.005wt%-0.5wt% (Nb).
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| KR10-2008-0134348 | 2008-12-26 | ||
| KR1020080134348A KR101115761B1 (en) | 2008-12-26 | 2008-12-26 | Steel restrained from surface decarborization and manufacturing method for the same |
| PCT/KR2009/007846 WO2010074544A2 (en) | 2008-12-26 | 2009-12-28 | Surface decarburization-restrained steel and manufacturing method thereof |
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| CN102264935A CN102264935A (en) | 2011-11-30 |
| CN102264935B true CN102264935B (en) | 2014-09-03 |
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| US (1) | US20110247734A1 (en) |
| EP (1) | EP2376666A4 (en) |
| JP (1) | JP5581335B2 (en) |
| KR (1) | KR101115761B1 (en) |
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| CN102221352A (en) * | 2011-03-21 | 2011-10-19 | 哈尔滨飞机工业集团有限责任公司 | Method for measuring depth of alloy steel decarbonized layer |
| CN107779751B (en) * | 2017-10-31 | 2020-08-11 | 攀钢集团攀枝花钢铁研究院有限公司 | Corrosion-resistant steel rail for high-speed railway and production method thereof |
| KR102326047B1 (en) * | 2019-12-20 | 2021-11-15 | 주식회사 포스코 | B-containing steel wire rod with excellent hardenability and corrosion resistance and manufacturing method of the same |
| WO2023190867A1 (en) * | 2022-03-30 | 2023-10-05 | 日本製鉄株式会社 | Steel member and steel sheet |
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| JP2004250768A (en) * | 2003-02-21 | 2004-09-09 | Nippon Steel Corp | Steel for machine structural having excellent cold workability and low decarburizing property, and production method therefor |
| CN101163862A (en) * | 2005-04-21 | 2008-04-16 | 西门子公司 | Turbine blade with a cover plate and a protective layer applied to the cover plate |
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| JPS5927370B2 (en) * | 1980-07-05 | 1984-07-05 | 新日本製鐵株式会社 | High strength cold rolled steel plate for press working |
| JPH03197642A (en) * | 1989-12-26 | 1991-08-29 | Kawasaki Steel Corp | Steel sheet for working having excellent slidability |
| JPH03232953A (en) * | 1990-02-09 | 1991-10-16 | Kawasaki Steel Corp | Zinc-series coated steel sheet for working excellent in spot weldability |
| JPH07286254A (en) * | 1994-04-21 | 1995-10-31 | Sumitomo Metal Ind Ltd | Steel sheet excellent in secondary working brittleness resistance and its production |
| JP3226737B2 (en) * | 1994-12-21 | 2001-11-05 | 三菱製鋼株式会社 | Low decarburized spring steel |
| US6503344B2 (en) * | 1999-02-05 | 2003-01-07 | Houghton Durferrit Gmbh | Boronizing agent in paste form |
| JP4681290B2 (en) * | 2004-12-03 | 2011-05-11 | 本田技研工業株式会社 | High strength steel plate and manufacturing method thereof |
| US8430974B2 (en) * | 2005-04-28 | 2013-04-30 | Aisin Aw Co., Ltd. | Carburized and induction-hardened component |
| JP4473786B2 (en) * | 2005-06-08 | 2010-06-02 | 株式会社神戸製鋼所 | High strength steel with excellent delayed fracture resistance |
| JP2007009300A (en) * | 2005-07-01 | 2007-01-18 | Daido Steel Co Ltd | Method for manufacturing cold-coiled wire rod for spring |
| KR101253790B1 (en) * | 2005-12-27 | 2013-04-12 | 주식회사 포스코 | High-strength steel part having excellent resistance for delayed fracture and method for producing the same |
| JP4310359B2 (en) * | 2006-10-31 | 2009-08-05 | 株式会社神戸製鋼所 | Steel wire for hard springs with excellent fatigue characteristics and wire drawability |
| JP4847988B2 (en) * | 2007-07-20 | 2011-12-28 | 株式会社神戸製鋼所 | Spring wire with excellent corrosion fatigue characteristics |
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- 2009-12-28 WO PCT/KR2009/007846 patent/WO2010074544A2/en active Application Filing
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004250768A (en) * | 2003-02-21 | 2004-09-09 | Nippon Steel Corp | Steel for machine structural having excellent cold workability and low decarburizing property, and production method therefor |
| CN101163862A (en) * | 2005-04-21 | 2008-04-16 | 西门子公司 | Turbine blade with a cover plate and a protective layer applied to the cover plate |
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| Publication number | Publication date |
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| US20110247734A1 (en) | 2011-10-13 |
| KR20100076336A (en) | 2010-07-06 |
| EP2376666A4 (en) | 2014-03-26 |
| WO2010074544A3 (en) | 2010-09-23 |
| EP2376666A2 (en) | 2011-10-19 |
| JP2012514133A (en) | 2012-06-21 |
| KR101115761B1 (en) | 2012-06-12 |
| JP5581335B2 (en) | 2014-08-27 |
| CN102264935A (en) | 2011-11-30 |
| WO2010074544A2 (en) | 2010-07-01 |
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