CN100535161C - Shaped steel excellent in fire resistance and producing method therefore - Google Patents
Shaped steel excellent in fire resistance and producing method therefore Download PDFInfo
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- CN100535161C CN100535161C CNB2005800249969A CN200580024996A CN100535161C CN 100535161 C CN100535161 C CN 100535161C CN B2005800249969 A CNB2005800249969 A CN B2005800249969A CN 200580024996 A CN200580024996 A CN 200580024996A CN 100535161 C CN100535161 C CN 100535161C
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Abstract
A shaped steel, such as H-shaped steel, excellent in fire resistance, where a flange portion has 50% or more of a ratio of strength, 80 % or less of yield ratio, and 100 J or more of impact strength of Charpy impact test at 0 DEG C, wherein the ratio of strength = (proof stress of 0.2% at 600 DEG C)/(yield strength at room temperature), and a producing method thereof are provided. The shaped steel comprises in mass percent (%): C: 0.03-0.15; Mo: 0.1- 0.6; V <= 0.35; and N: 0.002-0.012, and the balance being iron and residual impurities, wherein (x) a mol fraction of precipitate of alloy carbides and alloy carbonitrides at 600 DEG C is 0.3 % or more, and (y) the ratio of the mol fraction of precipitate of alloy carbides and alloy carbonitrides at 300 DEG C to the mol fraction of precipitate of alloy carbides and alloy carbonitrides at 600 DEG C is 2.0 or less.
Description
Technical field
The present invention relates to a kind of novel shaped steel, for example H-shaped steel, I-shaped steel, angle steel, channel-section steel etc., it is as material of construction, and yield tensile ratio is low and have excellent toughness and resistivity against fire, the invention still further relates to the preparation method of this shaped steel.
Background technology
Japan has formulated legislation about the new legislation of fire resistant building " design " in March, 1987.Afterwards, realized fire-resistant steel, it has guaranteed the high strength under the high temperature, and it does not have or only have the fire-resistant packing of minute quantity.
About shaped steel,, the technology of the resistivity against fire of many assurance steel has been proposed according to this trend.For example, proposed to guarantee in the high temperature for example intensity under 600 ℃, for example intensity and yield tensile ratio by the technology of utilizing Mo base carbonaceous deposits to strengthen.
For example, JP-A-9-104944 proposes to utilize the fire-resistant shaped steel of deposition intensifying technology and oxide compound metallurgical technology.The oxide compound metallurgical technology is a kind of technology of amount that can the controlled oxidation thing, and wherein oxide compound is by using Ti, B and Mg that the dissolved oxygen deoxidation in the steel is obtained.The oxide compound metallurgical technology produces following influence.
In the preparation process of shaped steel, the different piece of shaped steel stands the finish rolling (finish rolling) and different speed of cooling of differing temps respectively, makes on the steel cross section ununiformity that produces shape, causes the uniform defect of steel cross section microtexture.The uniform defect of this microtexture, the ununiformity of particle diameter for example causes the ununiformity defective of the mechanical property in steel cross section.
The fillet part (referring to Fig. 1) that flange portion, particularly flange portion and the soffit of girder partly cross is compared with other parts, and is little through rolling strain, need process under higher temperature.
In shaped steel () cross section for example, H-shaped steel, 150 ℃ the difference of between three parts of fillet part, 1/4 flange and the soffit of girder (referring to Fig. 1), can having an appointment aspect the temperature of processing in the end.Should eliminate because the different mechanical property of the each several part that the difference of each several part on rolling temperature causes.
By transforming core (transformation nuclei), titanium oxide for example is distributed in the ferrite particles and quickens particulate thus and transforms and can be reduced in the dependency of the formation of microtexture in the course of hot rolling to outlet temperature.Obtain the grain refined microtexture of even/homogeneous like this, that is, and the homogeneity of mechanical property.And, the particle of microtexture is homogenized, and grain refined, the toughness that improves obtained like this.
The inventor carries out big quantity research so that a kind of shaped steel to be provided, H-shaped steel for example, and it has low yield tensile ratio and toughness and has excellent fire-resistance, and the preparation method of this shaped steel is provided.During the big quantity research, the inventor recognizes following possible technical problem.
At first, when utilizing the oxide compound metallurgical technology to prepare the shaped steel that has excellent fire-resistance,, particularly for cast sheet, steel billet, steel ingot, approaching netted sheet, ingot iron etc., need complicated step to this method.These complicated steps comprise before the adding Ti and add Ti Control for Oxygen Content afterwards.These steps can make productive rate reduce and the production cost of shaped steel is increased.
Further, the deposition intensifying technology helps the fire prevention of shaped steel, for example intensity under the high temperature and yield tensile ratio.Yet, mainly contain Mo in use
2Under the situation of the Mo of C base carbide, if these components in specified range, this carbide can be dissolved in the steel by solid in 600-650 ℃ temperature range.Therefore may disappear by the contribution that provides with alloy carbide and the reinforcement of alloy carbonitride deposition to the intensity of steel.
The effect that deposition is strengthened depends on the deposition of alloy carbonitride.The alloy carbonitride comprises alloy carbide and alloy carbonitride.Notice that one or more metals may exist with carbide or carbonitride.Promptly at this, alloy carbide is meant the metallic carbide except that cementite.This paper back is represented deposition with sedimental molar fraction, also can abbreviate " sedimental molar fraction " as.Deposition depends on temperature.And this temperature dependency can be subjected to the influence of other factors, for example the carbon content of steel and based on thermodynamic behaviour of the kind of alloy carbide and alloy carbonitride or the like.
About carbon content, if C content and metallic element in the steel, for example the content of Mo, Ti, V, Nb, Cr is compared enough, and can form the alloy carbonitride, and the deposition of alloy carbonitride can increase with the reduction of temperature.This is because when the temperature of steel reduced, can form sedimentary C content increased with the reduction that solid dissolves (existing with solid solution) carbon content in ferrite.
Therefore, if the sedimental molar fraction of C content height and alloy carbide and alloy carbonitride excessively increases, even under for example identical temperature of identical heat condition reduces, intensity under the room temperature and yield tensile ratio can excessively increase.
EP-A-0347156 discloses the production method of the structure iron with excellent resistivity against fire and low yielding ratio, and described ladle is drawn together the V of 0.005-0.10% as optional elements.EP-A-1026275 discloses the rolled section steel of the high-intensity high-tenacity of the V that comprises 0.04-0.10%.
Summary of the invention
This analysis technically, the inventor recognizes: i) preferred alloy carbide and alloy carbonitride not only have thermodynamic stability, and have under the reheat temperature that solid is dissolved in the steel but in temperature solid dissolved characteristic not under 600-650 ℃ for example, ii) alloy carbide and alloy carbonitride, it can disposable dissolving in the reheat process and then can deposit in the hot rolled process of cooling, can be used for deposition so effectively and strengthen.
After further investigation, the inventor recognizes the preferred sedimental molar fraction of suitably controlling alloy carbide and alloy carbonitride under high temperature range and room temperature range, and the problem below preferably considering is determined the component of steel.
(i) the sedimental molar fraction of inhibition alloy carbide and alloy carbonitride excessively increases to prevent intensity and yield tensile ratio under the room temperature in room temperature range; (ii) obtain the sedimental specific molar fraction of alloy carbide and alloy carbonitride so that in high temperature range, obtain enough intensity.
Consider top problem, the inventor has designed various alloy carbides and alloy carbonitride and has found alloy carbide and the sedimental amount of alloy carbonitride can be by making at the metallic element that can form alloy carbide and alloy carbonitride, and for example the amount between Mo, Ti, V, Nb, Cr and C and the N (content) proper equilibrium is controlled.Discovery can be controlled thermodynamic behaviour by making amount (content) proper equilibrium between the metallic element.
More particularly, at Mo base alloy carbide Mo for example
2C is under the situation of sedimental main component, and it is solid dissolving fully in 600-650 ℃ temperature range, and the contribution of strengthening hardness of steel by the deposition of alloy carbide and alloy carbonitride can disappear.Yet, find to use at high temperature range internal ratio M
2The more stable MCN type alloy carbonitride of C type alloy carbide partly replaces Mo base alloy carbide (that is, MCN type alloy carbonitride and M
2C type alloy carbide is compared deposition to be increased, and " M " represent the metal outside the deironing here) solved top problem very effectively.
That is, add V and replace Mo with part and form alloy carbonitride rather than Mo base alloy carbide, and by making the add-on proper equilibrium of V, Nb and Mo, can control mainly generation based on the useful alloy carbonitride of V, Nb and Mo.
When mentioning wording for example when " room temperature ", this typically refers to the temperature in about 0 ℃-Yue 30 ℃ scope.Yet, note in the data under 300 ℃ it may being the representative of the data under the room temperature.This be since between room temperature and 300 ℃ the sedimental amount of alloy carbide and alloy carbonitride increase very for a short time.And, at these alloy carbides of the present invention's mensuration and the settling of alloy carbonitride, mainly between 300 ℃-600 ℃, produce.This is owing to the following fact, and along with temperature approaches room temperature, for example metallic element, carbon and the nitrogen diffusion in steel of solid dissolving element is extremely reducing aspect the deposition behavior.More particularly, sedimentary equilibrium state keeps almost constant between room temperature and 300 ℃.Therefore, in description of the invention, also can be representative under the room temperature at the sedimentation state under 300 ℃ the temperature.And the inventor has selected 600 ℃ temperature to measure or estimate specific mechanical properties as being used for, and suitable " high temperature " of the sedimental amount of alloy carbide and alloy carbonitride.Yet, should " high temperature " be not limited to 600 ℃ and can comprise the temperature that other is suitable.
The object of the present invention is to provide a kind of novel shaped steel, H-shaped steel for example, it has low yield tensile ratio and excellent toughness and resistivity against fire as material of construction, and the preparation method of this shaped steel is provided.This purpose can realize by following shaped steel and preparation method thereof.
According to the present invention, by special process for example the hot rolling cast steel that contains specific components mainly contain alloy carbide and the alloy carbonitride of V and Mo with an amount of formation, the shaped steel that can obtain at high temperature have excellent in strength and at room temperature have very good mechanical properties, for example H-shaped steel.According to the present invention, " cast steel " comprises sheet, ingot iron of sheet, steel ingot, steel billet, near net or the like.
Description of drawings
Fig. 1 shows from the position that H-shaped steel 1 is got testing plate (sample).First location is that flange 2 is at the central section of thickness direction (1/2 t
2) and be 1/4th (1/4B) position of 1/4 total flange width (B) in the flange width direction apart from the end of flange 2.The second position is that flange 2 is at the central section of thickness direction (1/2 t
2) and be half (1/2B) position (fillet part 4) of total flange width (B) in the flange width direction.The 3rd position is that the soffit of girder 3 is at the central section of thickness direction (1/2 t
1) and in half (1/2H) position of the total soffit of girder height of flange width direction (H).
Fig. 2 (a) is an example that contains 0.35% V at of the present invention, shows that sedimental total molar fraction (is M
2C type alloy carbide molar fraction and MCN type alloy carbonitride molar fraction sum) and temperature between the figure of relation, M wherein
2C type alloy carbide comprises that partly V and Nb comprise V and Nb as main component as solid solution and MCN type alloy carbonitride, and comprises that partly Mo is as solid solution.The longitudinal axis of Fig. 2 (a), Fig. 2 (b) and Fig. 3 is the sedimental molar fraction of alloy carbide, alloy carbonitride and alloy carbide and alloy carbonitride sum.
Fig. 2 (b) is the figure that shows the relation between sedimental total molar fraction and the temperature, and similar to Fig. 2 (a), wherein V content is 0.22%.
Fig. 3 utilizes ordinary method displays temperature and M
2C type alloy carbide, MCN type alloy carbonitride and M
2The sedimental figure of the relation between the molar fraction separately of C type alloy carbide and MCN type alloy carbonitride sum.Notice that ordinary method is both not considered alloy carbide and the alloy carbonitride sedimental molar fraction under 600 ℃, do not consider that also alloy carbide and alloy carbonitride are 2.0 or littler any means at the ratio of the sedimental molar fraction under 600 ℃ with alloy carbide and alloy carbonitride of the sedimental molar fraction under 300 ℃.
Embodiment
The present invention is more specifically described below.The element that comprises in the shaped steel of the present invention is below described.In this manual, per-cent " % " representative " weight % ".
C is the element that can improve the intensity of steel.From the angle of the sufficient intensity of structure iron, the content of C is 0.03% or bigger.C to the toughness of the steel of base material, in the heat affected zone (HAZ) the welding splitting resistance and toughness also influential.From the angle of these performances, the content of C is 0.15% or littler.Therefore, the content of C is 0.03-0.15%.
Si plays reductor (or oxygen scavenqer) and also influences the intensity of steel in system steel process.From the angle of the sufficient intensity of structure iron, the content of Si is 0.05% or bigger.Because excessive Si can produce M-A (martensite-austenite) composition of hardening structure, it can destroy the toughness at HAZ, so Si also influences the toughness at HAZ.Based on this, the content of Si is 0.5% or littler.Therefore, the content of Si is 0.05-0.50%.
Mn is the intensity and the flexible element that can improve parent phase (mother phase).Based on this viewpoint, the content of Mn is 0.4% or bigger.Mn is also influential to splitting resistance and toughness at HAZ.From the angle of these performances, the content of Mn is 2.0% or littler.Therefore, the content of Mn 0.4-2.0% preferably.
Mo is the element that can form Mo base alloy carbide.In the present invention, consider because the alloy carbide of Mo deposits, so shaped steel has excellent intensity under room temperature and high temperature.For shaped steel at high temperature has enough intensity, the content of Mo is 0.1% or bigger.Mo also improves the hardenability of steel.Because hardenability can excessively rise, therefore excessive Mo can damage the toughness of steel and HAZ.From the angle of these performances, the content of Mo is 0.6% or littler. therefore, the content of Mo is 0.1-0.6%, preferred 0.2-0.4%, more preferably 0.2-0.3%.
V is the element that can form the alloy carbonitride, and helps the deposition reinforcement of steel.In the present invention, when V used with Mo, V can be dissolved in the M that mainly contains Mo by solid
2In the alloy carbide of C, form ((Mo, V)
2C).And (C in alloy carbonitride N), forms ((Mo, V) (C, N)) to the M that V can make the Mo solid be dissolved in mainly to contain V.
By the content of adjusting V and Mo alloy carbide changed into and to have M
2The alloy carbide of the structure of C and have M (C, one of alloy carbonitride of structure N) or the two can suitably be adjusted based on thermodynamic (al) sedimental performance.For this conversion is carried out effectively, the content of V is 0.04% or bigger.
When adding excessive V, the toughness of the excessive increase of meeting of the amount of alloy carbonitride and steel and HAZ can be impaired.Therefore the content of V is 0.35% or littler.
On the other hand, in order to guarantee the sufficient intensity of shaped steel, for example, can preferably have the alloy carbonitride in the steel of being deposited on of capacity 600 ℃ of following resistivity against fires.For this purpose, the content of V is 0.20% or bigger.Therefore, the content of V is 0.20-0.35%.
In order to obtain resistivity against fire, major control has M
2The deposition of the V base alloy carbide of the structure of C.Yet more preferably major control forms and to have M (C, the alloy carbonitride of structure N) is so that improve resistivity against fire effectively.From this angle, the content of V is 0.20% or bigger.
N is the element that can form the alloy carbonitride.In order to obtain enough settlings, the content of N is 0.002% or bigger.And because excessive N can make the toughness of steel reduce, so the content of N is 0.012% or littler.Therefore, the content of N is 0.002-0.012%.
Al is equipped with at steel and plays strong reductor (oxygen scavenqer) in the process.Yet Al can be combined to form AlN with N, causes the amount of alloy carbonitride (settling) to reduce like this.Therefore, Al content preferably 0.01% or littler.
And, in the present invention, can add other optional components.
Nb is and V and the similar element of Ti, and it can form the alloy carbonitride, and for example (C N), and helps deposition and strengthens M.Yet, when the content of Nb greater than 0.06% the time since before the hot rolling under 1100-1300 ℃ Heating temperature the amount of undissolved alloy carbonitride increase, so it can not strengthen the intensity that further improves steel by deposition.
From improving the angle of intensity by the deposit alloy carbonitride, Nb content preferably 0.02% or bigger.Therefore, the content of Nb 0.02-0.06% preferably.
Ti is and Nb and the similar element of V, it can form the alloy carbonitride for example M (C, N) and help deposition and strengthen.In the present invention, Ti alloy carbonitride such as M (C is the solid dissolved in N), and it is by adding being combined to form of V or V and Nb, thus formation alloy carbonitride for example (V, Ti) (C, N) or (V, Ti, Nb) (C, N).Therefore, Ti influences alloy carbonitride stability at high temperature.
More particularly, when having Ti, the alloy carbonitride for example M (C N) can extend to comparatively high temps with thermostability.Yet, when the content of Ti surpasses 0.02% because the Heating temperature that before hot rolling, applies, for example 1100-1300 ℃ down can not solid dissolved alloy carbonitride amount increase, so it is unfavorable for that deposition strengthens.Therefore, the content of Ti preferably 0.02% or littler.
Cr is not only a kind of by hardenability that increases steel and the element that PH can improve the intensity under room temperature and the high temperature, and be a kind ofly can prevent crystal boundary on the steel surface (grainboudary) oxidized (intercrystalline oxidation (intergranular oxidation)), therefore and improve the performance on steel surface, for example element of slickness and uniformity coefficient.Yet, when having excessive Cr, the toughness of parent phase and can be damaged in the toughness of HAZ.From this angle, the content of Cr preferably 0.7% or littler.
Ni is a kind of flexible element that can improve parent phase.Yet, from the angle of cost, the content of Ni preferably 1.0% or littler.
Cu is a kind of element that can improve the intensity of steel.Yet when having excessive Cu, the hardenability of steel can excessively increase, so the toughness of steel and can reduce in the toughness of HAZ.From this angle, the content of Cu preferably 1.0% or littler.
The sedimental molar fraction of the structure of alloy carbide and alloy carbonitride and alloy carbide and alloy carbonitride can be by electron microscope observation and assay determination.As a simple method, can use a kind of software program that is used to calculate thermodynamic(al)equilibrium.
About can be used for software of the present invention, for example, can use " Thermo-Calc " (by " Thermo Calc Software, USA makes) calculate thermodynamic(al)equilibrium.As database, for example, also can use " SSOL " to analyze.Yet, to can be used for software among the present invention and database without limits, as long as this software and database are reliable.
In the present invention, when calculating the sedimental molar fraction of alloy carbonitride, with two types of alloy carbides and alloy carbonitride, promptly have the sedimental molar fraction and the representative M of alloy carbonitride of the representative MCN type alloy carbonitride of face-centerd cubic structure at this with six side's closed packings (Hexagonal Closed-Packed) structure
2The sedimental molar fraction sedimental molar fraction of the alloy carbide of C type alloy carbide and that be defined as alloy carbide and alloy carbonitride.Therefore, the inventor calculates the sediment yield of alloy carbide and alloy carbonitride, and calculates their sums, and total sediment yield of alloy carbide and alloy carbonitride is used for sedimental molar fraction.Under these design conditions, at the sedimental specific molar fraction of different elements and differing temps evaluation alloy carbide and alloy carbonitride.
Necessary words add V and come part to replace Mo, and this is because Mo is tending towards forming Mo base alloy carbide, it in 600-650 ℃ temperature range fully solid be dissolved in the steel, thereby under high like this temperature, be unfavorable for the deposition reinforcement.In the scope of the V of 0.20-0.35% of the present invention content, at the sedimental different molar fraction evaluations under different types of alloy carbide and alloy carbonitride and the differing temps in several temperature, the mechanical features under room temperature and the high temperature for example.Doing like this is proper equilibrium for the content of the content of studying C and N, simultaneously Mo and the V that comprises in special concern alloy carbide and the alloy carbonitride.
Preferably hypothesis mainly contains Mo and wherein V and/or Nb can solid dissolved alloy carbide be " M also
2C type alloy carbide " and mainly contain V and Nb and wherein Mo can solid dissolved alloy carbonitride be " MCN type alloy carbonitride ", estimate the sedimental molar fraction of alloy carbide and alloy carbonitride by calculating this thermodynamic(al)equilibrium.Because the sedimental molar fraction in using continuous refrigerative actual procedure is slightly different with the molar fraction of calculating above, therefore preferably carry out certain correction.
Mechanical property under preferred 600 ℃, particularly 0.2% proof stress are to obtain excellent resistivity against fire.0.2% proof stress is 157MPa or bigger preferably.
Change and to be used for the present invention's Elements C and the balance of N, in the performance of the scope inner evaluation shaped steel of the sedimental molar fraction of the alloy carbide of 0-1.0% and alloy carbonitride.The sedimental molar fraction of finding alloy carbide and alloy carbonitride is 0.3% or bigger 600 ℃ of necessity.
And, in order to solve intensity and the excessive problem that increases of yield tensile ratio under the room temperature, studied the proper ratio of the sedimental molar fraction of alloy carbide and alloy carbonitride, the sedimental molar fraction that is alloy carbide and alloy carbonitride is 300 ℃ and ratio under 600 ℃, and the suitable mechanical under several high temperature and the room temperature.For the inhibition and the excellent resistivity against fire that obtain simultaneously intensity under the room temperature is excessively raise, discovery must meet the following conditions: i) shock strength of Charpy impact test is 100J or bigger under 0 ℃; And satisfy condition preferably ii) that the tensile strength of flange portion is 400MPa or bigger; Iii) 0.2% proof stress under 600 ℃ is 157MPa or bigger.Condition i) and ii) be mainly used in the performance of room temperature, condition iii) is mainly used in resistivity against fire.
Exist V partly to replace under the situation of Mo,, estimating the performance of shaped steel in the scope of the sedimental molar fraction of the alloy carbide of 0-5.0% and alloy carbonitride by changing used Elements C of the present invention and the balance of N.Find that necessary is that the sedimental molar fraction of alloy carbide and alloy carbonitride is at 300 ℃ be 2.0 or littler at 600 ℃ ratio.
From top research, can up-to-date acquisition have the alloy carbide of excellent properties and the settling of alloy carbonitride, as Fig. 2 (a) with (b).At Fig. 2 (a) with (b), shown and partly contained V and Nb M as solid solution
2The sedimental amount of the alloy carbide of C type, mainly contain V, Nb and part contains sedimental amount and the M of Mo as the alloy carbonitride of the MCN type of solid solution
2The summation of C type alloy carbide and MCN type alloy carbonitride.
Fig. 2 (a) shows that the content of V is 0.35% situation.The sedimental molar fraction of alloy carbide and alloy carbonitride is 0.52% under 600 ℃ temperature, and it is (0.3 or bigger) within the scope of the invention.When temperature when 600 ℃ move to 300 ℃, the sedimental molar fraction of alloy carbide and alloy carbonitride increases to about 0.54% from about 0.52%.Their ratio is about 1.03, satisfies of the present invention 2.0% or littler condition.
Fig. 2 (b) shows that the content of V is 0.22% situation.The sedimental molar fraction of alloy carbide and alloy carbonitride is 0.52% under 600 ℃ temperature, and it is (0.3% or bigger) within the scope of the invention.When this temperature when 600 ℃ move to 300 ℃, the sedimental molar fraction of alloy carbide and alloy carbonitride increases to about 0.59% from about 0.52%.Their ratio is about 1.14, satisfies condition 2.0%.
Therefore, find that above-mentioned composition design can obtain inhibition and 600 ℃ of excellent down resistivity against fires that intensity under the room temperature is excessively raise simultaneously.
On the other hand, Fig. 3 has shown the result who composition steel is within the scope of the invention applied ordinary method.As shown in Figure 3, the sedimental molar fraction of alloy carbide and alloy carbonitride (0.30% or bigger) within the scope of the invention under 600 ℃.Yet, when temperature when 600 ℃ move to 300 ℃, the sedimental molar fraction of alloy carbide and alloy carbonitride obviously increases to about 1.42% from about 0.61%.The ratio of the sedimental molar fraction under 300 ℃ and 600 ℃ is (2.0 or littler) not within the scope of the invention.Fig. 3 shows that the problem of ordinary method is that the intensity under 300 ℃ is too high.Note, ordinary method is both not considered alloy carbide and the alloy carbonitride sedimental molar fraction under 600 ℃, does not consider that again alloy carbide and alloy carbonitride are 2.0 or littler any means at the ratio of the sedimental molar fraction under 600 ℃ with alloy carbide and alloy carbonitride of the sedimental molar fraction under 300 ℃.
The settling for example size of alloy carbide and alloy carbonitride is influential to intensity.According to desirable strength, preferably make the settling grain refined, for example, to the size of 10-1000nm.Preferably, perhaps be maintained at about 600 ℃ and form settling by temperature with steel carrying out solution-treated and the cooling period after hot rolling formation settling before the hot rolling.
In the present invention, to MCN type alloy carbonitride with temperature (only 300 ℃-600 ℃ temperature range) the dependency sediment yield that hangs down stability and M with temperature dependency sediment yield
2The ratio of the sediment yield between the C type alloy carbide has no particular limits.Yet, we can say promptly the settling/M of MCN type alloy carbonitride
2(this paper back is referred to as MCN/M to the ratio of the settling of C type alloy carbide
2The ratio of C), greater than the ratio of the settling that obtains by ordinary method.For example, 0.7 or bigger MCN/M
2The ratio of C provides enough effects at high temperature under as 600 ℃.Yet, work as M
2When the total amount of C reduces, MCN/M
2The ratio of C is not a deciding factor.In other words, 0.7 or bigger MCN/M
2The ratio of C is not a condition required for the present invention.
To the reasons are as follows that course of hot rolling limits.At first with cast steel, for example reheat such as sheet, steel billet, steel ingot, subreticulate sheet, ingot iron are to 1100-1300 ℃ scope.The reason that temperature is limited is to guarantee that enough temperature make cast steel can be in austenitic range processed and deposit reinforcement by the disposable solid dissolving of alloy carbide and alloy carbonitride is fully developed.
After the reheat, cast steel is through course of hot rolling.This course of hot rolling consists essentially of by the rolling fragmentation of groove (break-down) process, intermediate rolling and finish rolling.The intermediate rolling process can be undertaken by the general roller mill in centre that comprises edger (edger rolling machine) and general roller mill, and the finish rolling process can be undertaken by general roller mill.Said process also comprises the operation of rolling of the soffit of girder height partly of the oblique milling system of use (skew roll) control shaped steel.
In the shattering process of the rolling process, by a plurality of rolling systems, each roller has groove and the bottom centre at the bottom of groove that bottom width differs from one another and has convex part cast steel at width.Guarantee suitable flange width and soffit of girder height like this.
In the intermediate rolling process, obtain suitable flange width and obtain suitable soffit of girder thickness and thickness of flange by general roller mill by edger.And in the finish rolling process, forming shaped steel with pre-sizing, the surface temperature with flange portion remains on for example 800 ℃ or bigger simultaneously.
The present invention preferably can be used for soffit of girder thickness wherein in the scope of 9mm-40mm, thickness of flange in the scope of 12mm-60mm, soffit of girder height is the shaped steel in about 500mm and the scope of flange width at 200mm-500mm.
In the course of hot rolling after reheat, preferred shaped steel water cooling is at least once to 700 ℃ or littler, and is rolling in temperature recovery process (heat returning process) then, and described temperature is in the surface measurements of flange portion.
As mentioned above, owing to the shape of shaped steel, the temperature of fillet and flange portion is usually above the temperature of soffit of girder part.In order to reduce the ununiformity of temperature, with the water cooling flange portion and in heat supply process, carry out at least once rolling.Preferably should can repeat according to the size of shaped steel and the quantity of the operation of rolling with water cooling and rolling working cycle.
In the present invention, after course of hot rolling is finished, with the shaped steel naturally cooling, perhaps cooling fast, for example at least once, naturally cooling then.The microtexture of steel is made like this that by grain refined intensity, the toughness under the high temperature and the intensity under the room temperature improves in this process of cooling.
Carrying out before the naturally cooling under the quick refrigerative situation, average cooling rate preferably between 0.5-5.0 ℃/s so that further grain refined microtexture.
In the present invention, carry out after the above-mentioned process of cooling, can produce the shaped steel that has excellent fire-resistance with following mechanical property.Promptly, for example: by the strength ratio of (0.2% proof stresss under 600 ℃)/(yield strength under the room temperature) definition be 50% or bigger, room temperature under yield tensile ratio be 80% or littler and 0 ℃ of charpy impact absorption down can be 100J or bigger mechanical property; Flange portion tensile strength under the room temperature be 400MPa class (level), 600 ℃ down 0.2% proof stress be that 157MPa or bigger and 0 ℃ of following charpy impact absorb can be 100J or bigger mechanical property; With room temperature lower flange part tensile strength be 490MPa class, 600 ℃ down 0.2% proof stress be that 217MPa or bigger and 0 ℃ of following charpy impact absorb can be 100J or bigger mechanical property.
Embodiment
Embodiments of the invention are described below.Yet the condition described in these embodiment only is descriptive, and the present invention is not limited to these conditions.Without prejudice to main points of the present invention with the situation that realizes purpose of the present invention under, the present invention can implement under other various conditions.
The steel ingot and the steel billet that are used for these embodiment, have the component/composition shown in the table 1 and pre-determine sedimental molar fraction by " Thermo-Calc " EQUILIBRIUM CALCULATION FOR PROCESS under 600 ℃ and 300 ℃, with its fusion in steel melting furnace, and cast thickness is steel ingot and the steel billet of about 240-300mm in the continuous pouring process.In table 1, " tr " is meant " can not detect " or " unavoidable impurities ".
The condition of the embodiment of compared steel " a-g " is not within the scope of the invention.The condition of the component of embodiment " a-c " within the scope of the invention, but alloy carbide and the alloy carbonitride sedimental molar fraction under 600 ℃ (0.3% and bigger) not within the scope of the invention.As for embodiment " d-g ", alloy carbide separately and alloy carbonitride are at the ratio of the sedimental molar fraction under 600 ℃ with alloy carbide and alloy carbonitride of the sedimental molar fraction under 300 ℃, i.e. (molar fractions under 300 ℃)/(molar fractions under 600 ℃) are (2.0 and littler) not within the scope of the invention.
In table 1, alloy carbide that shows on the rightest hurdle and alloy carbonitride the sedimental molar fraction 300 ℃ under be not identical at the ratio of the sedimental molar fraction 600 ℃ under and by the value of separately alloy carbide and the alloy carbonitride sedimental molar fraction calculating under the sedimental molar fraction under 300 ℃ and 600 ℃.This not being both by significant figure causes that this is because alloy carbide and alloy carbonitride sedimental molar fraction separately are calculated to three decimal places that rounded up.
Each cast steel reheat to 1100-1300 ℃, is passed through course of hot rolling then, comprise following process of carrying out, by the shattering process of the groove operation of rolling; The intermediate rolling process, wherein, middle general roller mill comprises edger and general roller mill and the finish rolling process of being undertaken by general roller mill, thereby forms the H-shaped steel of predetermined size.
In the superincumbent course of hot rolling, use the soffit of girder height of oblique milling system by operation of rolling control H-shaped steel.
The H-shaped steel of producing, its soffit of girder thickness in the scope of 9mm-40mm, thickness of flange in the scope of 12mm-60mm, soffit of girder height is that about 500mm and flange width are in the scope of 200mm-500mm.
Fig. 1 shows the cross section of H-shaped steel, and it is by producing at horizontal (non-vertical) cutting steel.Use test sheet (sample) obtains the mechanical property of the H-shaped steel that makes by various tests.Fig. 1 shows from the position that testing plate (sample) is got.First location is that flange 2 is at the central section of thickness direction (1/2 t
2) and be 1/4th (1/4 B) position of 1/4 total flange width (B) in the flange width direction apart from the end of flange 2.The second position is that flange 2 is at the central section of thickness direction (1/2 t
2) and be half (1/2 B) position (fillet part 4) of total flange width (B) in the flange width direction.The 3rd position is that the soffit of girder 3 is at the central section of thickness direction (1/2 t
1) and in half (1/2 H) position of the total soffit of girder height of flange width direction (H).(1/4 B) mechanical property of position can be represented the mechanical property of the flange portion of H-shaped steel in the above.Yet, measure the mechanical property of above-mentioned 3 positions and check the mean value of mechanical property of these 3 positions and the value of the mechanical property of soffit of girder part (the 3rd position) to confirm to prevent to have the excessive reinforcement of the mechanical property of soffit of girder part.Also promptly, calculate the value of soffit of girder part and the ratio of the mean value of three positions.
Table 2 has been described the result who tests above, promptly, the yield tensile ratio of the yield strength of room temperature, the tensile strength of room temperature, room temperature, 0 ℃ charpy impact absorb can be (according to 3 mean values of JIS, sample is JIS NO.4 (actual size), have 2mm V-type recess), according to the ratio of 0.2% proof stress under 0.2% proof stress under 600 ℃ of JIS A2 and 600 ℃ with the yield strength of room temperature, for example according to JIS NO.13A or 13B, this depends on the thickness of shaped steel.About Charpy impact test, the measured value of the data represented fillet part (1/2 B) in the table 2, the fillet part has the lower value of any other parts than the cross section of H-shaped steel in Charpy impact test.About 0.2% proof stress under 600 ℃, the measured value of data represented (1/4 B) position at flange portion of table 2.(1/4 B) value of position is represented the intensity of H-shaped steel.For steel, the desirable strength of two inhomogeneities (level) is arranged.One is the SN400 class, and wherein tensile strength is 400MPa and bigger under the room temperature, and another is the SN490 class, and wherein tensile strength is 490MPa and bigger under the room temperature.About the SN400 class, show that intensity is about the embodiment of 400-520MPa.About the SN490 class, show that intensity is about the embodiment of 500-611MPa.In table 2, according to these class descriptions result, in addition, the value of the mechanical property of calculating soffit of girder part is listed in the table with the ratio of the mean value of 3 positions.
Steel of the present invention satisfies the sedimental molar fraction of following condition such as component, alloy carbide and alloy carbonitride.The mechanical property of steel of the present invention all obtains target capabilities under high temperature (600 ℃) and room temperature, for example yield strength, tensile strength, 0 ℃ of charpy impact absorb can, particularly the strength ratio with the flange portion of steel is defined as (0.2% proof stresss under 600 ℃)/ratio of (yield strength under the room temperature) and the yield tensile ratio of room temperature.
Although Comparative Examples has the component identical with steel of the present invention, do not satisfy under room temperature and the high temperature at least a in the mechanical property, this is because the requirement of the sedimental molar fraction of alloy carbide of their discontented unabridged version inventions and alloy carbonitride.
Compared steel " c, f, g " is compared with steel of the present invention (100J or bigger), and 0 ℃ charpy impact absorbs can be not enough.Compared steel " a, b " belongs to the SN400 class, does not reach 600 ℃ of target value of 0.2% proof strength, i.e. 157MPa and bigger down.Compared steel " d, e " belongs to the SN490 class, and 0.2% proof strength under 600 ℃ is respectively 206,212MPa, does not reach 217MPa and bigger target value.The strength ratio of contrast " d, e " does not reach 50% or bigger target value.
As mentioned above, under the condition of the add-on proper equilibrium of V and Mo, by forming alloy carbide and the alloy carbonitride that mainly constitutes, the invention provides the shaped steel that has excellent fire-resistance and at high temperature have mechanical property under ideal intensity and the room temperature by V and Mo.
Shaped steel of the present invention can be used as material of construction fully and has great industrial applicibility.
All patents of quoting as proof, publication, outstanding and co-pending application and the provisional application of the reference of the application institute are all added this paper at this.
Therefore the present invention has been described, apparent, can change it in many ways.These change should not think and deviates from the spirit and scope of the present invention, and all is that conspicuous improvement is also contained in the scope of claims with all these to those skilled in the art.
Claims (4)
1, a kind of shaped steel comprises (weight percent (%)):
C：0.03-0.15，
Si：0.05-0.50，
Mn：0.4-2.0，
Mo：0.1-0.6，
V:0.20-0.35 and
N：0.002-0.012，
Optional Al≤0.01 that exists,
And randomly comprise the element of one or more following weight percents (%):
Ti：0.005-0.020，
Nb≤0.06％，
Cr≤0.7，
Ni≤1.0 and
Cu≤1.0，
And surplus is iron and residual impurity, wherein
Alloy carbide and the alloy carbonitride sedimentary molar fraction (x) under 600 ℃ be 0.3% or bigger and
Alloy carbide and the alloy carbonitride sedimentary molar fraction under 300 ℃ with have a M
2C type alloy carbide is 2.0 or littler with the ratio (y) with MCN type alloy carbonitride sedimentary molar fraction under 600 ℃,
Wherein, the flange portion of described shaped steel has 50% or bigger strength ratio, 80% or the shock strength of littler yield tensile ratio and 100 J or bigger 0 ℃ of following Charpy impact test, wherein strength ratio=(600 ℃ 0.2% proof stresss) down/(yield strength under the room temperature).
2, the preparation method of shaped steel as claimed in claim 1 carries out hot rolling after reheat cast steel, comprise step:
(a) with the cast steel reheat to 1100-1300 ℃;
(b) the described cast steel of hot rolling is to form shaped steel; With
(c) after hot rolling finishes, naturally cooling or quick cooling, the described shaped steel of naturally cooling then.
3, method as claimed in claim 2, wherein said hot-rolled step comprise at least once shaped steel with being water-cooled to 700 ℃ or littler, and described temperature is in the surface measurements of the flange portion of shaped steel, and is rolling in temperature recovery process then.
4, method as claimed in claim 3, wherein said quick refrigerative step is to carry out under the average cooling rate of 0.5-5.0 ℃/s.
Applications Claiming Priority (4)
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| JP2004220454 | 2004-07-28 | ||
| JP220337/2004 | 2004-07-28 | ||
| JP220454/2004 | 2004-07-28 | ||
| JP207185/2005 | 2005-07-15 |
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| CN100535161C true CN100535161C (en) | 2009-09-02 |
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