WO2010104165A1 - Hic-resistant thick steel sheet and uoe steel pipe - Google Patents
Hic-resistant thick steel sheet and uoe steel pipe Download PDFInfo
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- WO2010104165A1 WO2010104165A1 PCT/JP2010/054173 JP2010054173W WO2010104165A1 WO 2010104165 A1 WO2010104165 A1 WO 2010104165A1 JP 2010054173 W JP2010054173 W JP 2010054173W WO 2010104165 A1 WO2010104165 A1 WO 2010104165A1
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
- B21C37/06—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
- B21C37/08—Making tubes with welded or soldered seams
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/06—Surface hardening
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
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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
- C22C38/02—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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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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
Definitions
- the present invention relates to a thick steel plate and a UOE steel pipe, and more specifically, excellent in hydrogen-induced crack resistance (HIC resistance) suitable for use in applications such as line pipes, offshore structures, and pressure vessels.
- the present invention relates to a high-strength thick steel plate of X60 grade or higher and a UOE steel pipe made of this thick steel plate.
- thin steel plate means a steel plate having a thickness of 6.0 mm or more.
- Line pipes used for the transportation of crude oil and natural gas in addition to general properties such as strength, toughness, and weldability, may be used in corrosive environments containing hydrogen sulfide. Resistance to induced cracking (hereinafter referred to as “HIC”) is required as an important characteristic.
- HIC Resistance to induced cracking
- HIC prevention measures are disclosed below.
- Patent Document 1 if MnS is present in a steel material, cracks are generated starting from this, and based on the knowledge that when MnS extends for a long time during rolling, the cracking sensitivity increases, the S content in the steel It is described that S in steel is made into a fine spheroidized CaS or REM sulfide by reducing Ca and REM in steel.
- Patent Document 2 a hard structure such as martensite or bainite is formed by segregation of C, Mn, P, etc. in a portion corresponding to the center segregation portion of the slab, and this is a propagation path of cracks.
- it is hard by reducing the concentration of C, Mn, P, etc. in the steel, performing soaking treatment to reduce segregation by diffusion, and further increasing the cooling rate after rolling. Preventing tissue formation is disclosed.
- Patent Documents 3 and 4 disclose that the center segregation itself is eliminated by rolling the slab once after bulging the slab at the stage where the continuously cast unsolidified molten steel remains.
- Patent Documents 5 to 7 with the improvement of the strength specifications of steel materials that have recently been demanded, the single countermeasures against the above-mentioned central segregation part and MnS generation have become insufficient in many cases. Therefore, by adding Cu or Ni to the steel, a protective film is formed on the surface of the steel material to suppress the intrusion of hydrogen into the steel, and the addition of Cr, Mo, etc. or the heat treatment during rolling ( It is disclosed that TMCP (thermomechanical control process) is used in combination.
- TMCP thermomechanical control process
- the present invention is based on an important finding that Nb carbonitride is the starting point of HIC in addition to MnS, C, Mn, and P, which have been conventionally considered as the main cause of hindering HIC resistance. .
- the “Nb segregation degree”, “Mn segregation degree”, and “Ti segregation degree” are measured vertically from the center of the plate thickness in a cross section (cross section perpendicular to the plate surface) cut in parallel to the plate rolling direction of the steel plate.
- Nb, Mn and Ti concentrations are measured at 50 points or more, preferably 100 points or more, and for each of Nb, Mn and Ti, all measured values are obtained by the average concentration which is the arithmetic average value of all measured values. It means a value calculated by dividing the maximum density which is the maximum measured value. That is, the Nb segregation degree is the highest Nb concentration / average Nb concentration, the Mn segregation degree is the highest Mn concentration / average Mn concentration, and the Ti segregation degree is the highest Ti concentration / average Ti concentration.
- 50 points or more is a length range of 20% or more of the total plate thickness in the plate thickness direction (that is, a length of 10% or more of the total plate thickness above and below the center of the plate thickness). In the range, it is preferable that the position is changed from the center of the plate thickness in the up and down direction at almost equal increments.
- the segregation value of each element can be calculated by obtaining the average concentration and the maximum concentration of Nb, Mn, and Ti from the measured values obtained at 50 points or more. As will be described later, in the examples of the present invention, the degree of segregation was determined by measuring 60 points (total measurement length: 12 mm) at 0.1 mm intervals from the center of the plate thickness.
- Thin steel plate means a steel plate having a thickness of 6.0 mm or more as described above.
- a preferable plate thickness is 10 mm or more where segregation is particularly likely to occur.
- the upper limit of the plate thickness is not particularly defined, but according to the present invention, a HIC thick steel plate having a plate thickness of up to 40 mm can be realized.
- the present invention is a UOE steel pipe characterized by using the above-mentioned HIC thick steel plate as a material.
- the UOE steel pipe is manufactured by press-forming a thick steel plate into a U shape and then an O shape, and submerging arc welding the butt portion of the plate, and then expanding the tube with an expander from the inside and finishing it to a predetermined size.
- HIC thick steel plate and UOE steel pipe according to the present invention, high strength of X60 grade (about YP70 ksi) or more can be obtained. Moreover, in addition to controlling the elements that cause the generation of HIC, such as Mn, C, P, and S, which are conventionally proposed, the generation of HIC due to Nb and Ti carbonitrides can be prevented. Therefore, generation of HIC in the high-strength thick steel plate can be reliably prevented.
- the thick steel plate having excellent HIC resistance according to the present invention can be used for structures such as offshore structures and pressure vessels, or for manufacturing UOE steel pipes.
- the UOE steel pipe excellent in HIC resistance according to the present invention is particularly suitable for a line pipe, but can also be used in an offshore structure. Since the generation of HIC can be surely prevented, the reliability of the product is remarkably increased.
- FIG. 2A is a graph showing the relationship between Mn concentration and Nb concentration
- FIG. 2B is a graph showing the relationship between Mn concentration and Ti concentration.
- the chemical composition of the thick steel plate according to the present invention is as described below. In the following description, all percentages relating to the chemical composition of steel mean mass%. [C: 0.02% or more, 0.07% or less]
- C is known as an element that greatly affects the strength of steel. If the C content is less than 0.02%, it is difficult to obtain a predetermined strength for applications such as line pipes.
- the C content exceeds 0.07%, as described above, a macro-segregation portion is formed at the thickness center portion of the slab during continuous casting, which causes generation of HIC. Therefore, the C content is set to 0.02% or more and 0.07% or less. From the above viewpoint, the lower limit of the C content is preferably 0.03%, and the upper limit is preferably 0.06%.
- Si 0.05% or more, 0.50% or less
- Si When Si is contained in an amount of 0.05% or more, it generally acts as a deoxidizing element in the steel manufacturing process and is effective in reducing the oxygen concentration in the steel. Si also has the effect of strengthening steel. However, if the Si content exceeds 0.50%, island-shaped martensite is generated, and the toughness of the HAZ (welding heat affected zone) is deteriorated during welding. Further, since Si has a strong interaction with Ti, it affects the generation of TiN even though it is not a constituent element.
- the Si content is set to 0.05% or more and 0.50% or less.
- a preferable Si content is 0.05% or more and less than 0.3%.
- Mn 1.1% or more and 1.6% or less
- Mn is an element that generally has a great influence on the strength of a steel material. If the Mn content is less than 1.1%, it is difficult to obtain sufficient strength. If the Mn content exceeds 1.6%, Mn concentrates at the center segregation part as described above, and the HIC resistance is deteriorated. For this reason, Mn content shall be 1.1% or more and 1.6% or less. In order to ensure the HIC resistance at the center segregation part, the Mn content is preferably 1.1% or more and less than 1.5%.
- P 0.015% or less
- P is one of impurities inevitably contained in the steel, and is preferably as low as possible.
- P has a small distribution coefficient at the solid-liquid interface during solidification and has a tendency to remarkably segregate. Therefore, as described above, P is concentrated at the central segregation portion to deteriorate the HIC resistance. Therefore, the upper limit of the P content is set to 0.015%.
- the P content is preferably less than 0.008%.
- the lower limit of the P content is not specified, the extreme reduction of the P content is accompanied by a corresponding increase in cost. Therefore, the P content is preferably 0.004% or more.
- S is one of the impurities inevitably contained in the steel and is preferably as low as possible.
- S is an element that has a small distribution coefficient at the solid-liquid interface during solidification and has a tendency to remarkably segregate.
- the segregation part generates MnS and becomes the starting point of HIC generation.
- the upper limit of the S content is set to 0.002%.
- the upper limit of the S content is preferably 0.001%.
- the lower limit of the S content is not specified, an extreme reduction in the S content is accompanied by a corresponding increase in cost, so the S content is preferably 0.0003% or more.
- Nb is an element that forms carbonitrides in steel to increase the strength of the steel and is effective in improving toughness. Therefore, Nb is contained 0.005% or more.
- Nb is used to control the microstructure of the thick steel plate by controlling solid solution and precipitation. In order to obtain this effect, 0.005% or more of Nb is contained.
- an increase in the amount of Nb means an increase in the amount of Nb carbonitride, which may cause a decrease in HIC resistance. For this reason, Nb content shall be 0.005% or more and 0.060% or less.
- the Nb content is preferably 0.010% or more and 0.040% or less.
- Ti improves the strength of the steel, fixes N in the steel as TiN, and reduces the amount of precipitation of NbN and AlN. Therefore, NbN to the austenite grain boundary during bending and straightening of continuous cast slabs There is also an effect of preventing slab surface cracks caused by dynamic precipitation of AlN. In order to obtain such an effect, 0.005% or more of Ti is contained. However, if the Ti content exceeds 0.030%, a large number of Ti carbides are generated, which reduces HAZ toughness and causes coarse TiN to be generated.
- Ti content shall be 0.005% or more and 0.030% or less.
- a preferable Ti content is 0.010% or more and 0.025% or less.
- Al 0.005% or more, 0.06% or less
- Al is one of the elements effective for reducing the oxygen concentration in steel as a deoxidizing element.
- the Al content necessary for deoxidation is 0.005% or more. If the Al content is less than this, desulfurization will be insufficient, the yield of Ca addition will deteriorate, and the effect will not be sufficiently obtained, and HIC will occur due to the segregation of sulfides and S in the steel. .
- the Al content is set to 0.06% or less.
- the Al content is preferably 0.04% or less.
- Ca 0.0005% or more, 0.0006% or less
- Ca is a semi-essential additive element for reducing the S concentration, preventing the formation of MnS, and controlling the form of sulfide. For this reason, 0.0005% or more of Ca is contained. However, when the Ca content exceeds 0.0006%, the effect is saturated and the manufacturing cost increases. For this reason, Ca content shall be 0.0005% or more and 0.0006% or less.
- N is an element that inevitably enters the steel when the steel is melted in an air atmosphere such as a converter.
- N is a constituent element of coarse Nb carbonitride which is focused in the present invention.
- Nb carbonitrides are not directly associated with N preferentially, but are known to precipitate with crystallized TiN as nuclei.
- N is an element that forms nitrides with Al, Ti, etc. in steel materials, and these nitrides have the effect of refining crystal grains as pinned particles during the hot working process. Affects the formation of microstructures. For this reason, N needs to be a concentration of 0.0015% or more.
- these nitrides are dynamically precipitated at the austenite grain boundaries during continuous casting, causing cracks on the slab surface, so the upper limit of N is 0.007%.
- each element symbol means the content (% by mass) of the element.
- the upper limit of the C and Mn contents is determined for the purpose of reducing MnS generation and C segregation. For this reason, in order to ensure strength, at least one alloy element selected from Cu, Ni, Cr, and Mo is contained. In order to surely obtain the effect of improving the strength, it is effective that the total content of these alloy elements is more than 0.1%. However, if the content of these alloy elements is too large, the hardenability is increased, and the strength is increased and part of the structure is hardened. As a result, the HIC resistance is deteriorated. Therefore, in the present invention, the total content of these alloy elements is less than 1.5%.
- each of these alloy elements will also be described. As can be seen from these explanations, it is preferable to contain all of these four elements, but depending on the target strength level, one to three additives may be added. However, even in that case, the total amount thereof is made to be more than 0.1% and less than 1.5%.
- Cu improves the hardenability of steel by containing 0.1% or more.
- the Cu content exceeds 0.5%, the hot workability and machinability of the steel deteriorate, and surface cracks called copper cracks are induced during continuous casting. Therefore, the Cu content is desirably 0.1% or more and 0.5% or less.
- Cu is contained in an amount of 0.2% or more, it is desirable to contain Ni in an amount of (1/3) or more of Cu in order to prevent copper cracking.
- Ni has the effect of improving the toughness as well as improving the strength of the steel by solid solution strengthening. These effects are obtained when the Ni content is 0.1% or more. However, even if Ni is contained in excess of 1.0%, the effect reaches a peak, and the weldability is rather deteriorated. For this reason, the Ni content is desirably 0.1% or more and 1.0% or less.
- Mo improves the hardenability of steel and contributes to strength increase.
- Mo is an element that is difficult to segregate microscopically and has an effect of suppressing the generation of HIC due to central segregation. These effects of Mo are obtained with a Mo content of 0.02% or more.
- Mo is not only an expensive element that leads to an increase in cost, but if Mo is contained in an amount exceeding 0.5%, a hardened phase such as a bainite phase or a martensite phase is generated, and the HIC is rather deteriorated. Therefore, the Mo content is preferably 0.02% or more and 0.5% or less. Since the influence on the HIC resistance is larger than that of the other three elements described above, the Mo content is more preferably 0.3% or less.
- V 0.10% or less
- V is effective for increasing the strength of steel by forming a solid solution and carbonitride in ferrite in steel, and therefore V may be contained particularly when high strength is required.
- the V content exceeds 0.1%, the HAZ toughness is adversely affected. For this reason, when it contains V, the content is made into 0.10% or less.
- V content is 0.01%.
- Fe and impurities Other than the above are Fe and impurities.
- Mn segregation degree”, “Nb segregation degree”, and “Ti segregation degree” are segregation degrees at the center of the plate thickness, and are determined as described above.
- the present inventors have reduced MnS, C, Mn, and P, which have been conventionally considered as the main cause of hindering HIC resistance in thick steel plates used for X60 grade (about YP70 ksi) line pipes and the like. Even so, it has been found that HIC may occur. The reason for this is thought to be that cracks may occur due to the Nb or Ti carbonitrides remaining in the steel as the starting point even when conventional HIC measures such as MnS and macrosegregation are taken.
- Nb and Ti also caused the occurrence of HIC due to the segregation degree in the thick steel plate. That is, in addition to the conventional knowledge, by newly controlling the segregation of Nb and Ti, it is possible to improve the HIC resistance of thick steel plates used for X60 grade line pipes and the like.
- the present inventors performed an HIC test on a test piece collected from the manufactured thick steel plate. All cracks occurred at the center of the plate thickness. From this, it can be seen that HIC occurs at the central segregation part. A detailed investigation of the crack occurrence portion was performed on the test piece where the crack occurred. The inclusions that became the starting point of cracking were analyzed by SEM / EDS, but the concentration varied variously, but Nb was mainly contained, and the carbonitride (Nb (C, N)) (10 This was found to be “Nb carbonitride” in the present specification, containing up to vol% Ti.
- the segregation degree investigation can be carried out by using an EPMA (Electron Beam Microanalyzer, Electron Probe Micro Analyzer) method, a laser ICP (Laser Ablation Inductively Coupled Plasma) method, or a chemical analysis method.
- EPMA Electron Beam Microanalyzer, Electron Probe Micro Analyzer
- laser ICP Laser Ablation Inductively Coupled Plasma
- the present inventors investigated the degree of segregation of each element at the center of the plate thickness from the rolled steel plate, and investigated the correlation with the presence or absence of HIC.
- the degree of segregation of each element was investigated by the laser ICP method.
- the apparatus used was a laser ICP analyzer manufactured by Shimadzu Corporation.
- the laser ICP method irradiates a cut surface of a sample with a laser beam, conveys the generated vapor with a carrier gas, emits light in induction plasma, analyzes the wavelength and intensity of this light, and quantitatively analyzes each element. This is a type of emission analysis. By moving the sample in one direction, irradiating a laser beam, and repeating the analysis, it is possible to examine the concentration change at a certain length for each element.
- concentration of each element at 120 points in a total length of 12 mm, 6 mm above and below the plate thickness center of the cut surface Get the measured value.
- macrosegregation can be fully evaluated.
- the arithmetic average value of the measured values obtained at 120 points is regarded as the average concentration of the element in the thick steel plate, and the maximum value (maximum concentration) among the measured values is divided by the average concentration. Is required.
- the segregation degree of each element is obtained by actually obtaining the concentration (mass%) of each element from the measured values (emission peak intensity) at 120 points obtained by the laser ICP method, and calculating the maximum concentration / average concentration. You can also. However, since this concentration and the luminescence peak intensity attributed to each element obtained by measurement are in a directly proportional relationship, the segregation degree can be easily obtained as the ratio of maximum peak intensity / average peak intensity for each element.
- the laser beam diameter is about 1 mm, all inclusions of 1 mm or less are absorbed in the measurement data. Since the size of the inclusion is usually about several ⁇ m, and even a large one is about several tens of ⁇ m, the measurement of the degree of segregation sufficiently including the inclusion can be performed by this measurement.
- FIG. 1 is a graph showing the results of segregation degrees of Mn, P, S, Nb, and C obtained by a laser ICP method for a thick steel plate having an HIC occurrence rate of 8.8%.
- the horizontal axis in the graph of FIG. 1 is the measurement point position in the plate thickness direction (the plate thickness center is 60 ⁇ unit is 0.1 mm>, the measurement length is 6 mm each in the vertical direction from the plate thickness center, and the measurement points are 120 points in total)
- the vertical axis represents the measurement result (luminescence peak intensity, arbitrary unit) of each element.
- the level of the vertical axis varies depending on the element, but the average composition and the degree of segregation can be calculated by this measurement method.
- the degree of segregation can be determined by measuring the element at the target site using chemical analysis or the like and comparing the result with the analysis result of the part without segregation.
- the degree of segregation can also be determined by an EPMA method or a laser emission mass spectrometry method (Laser-Ablation-Inductive-Coupled-Plasma-Mass-Spectroscopy, LA-ICP-MS method) in which quantitative determination is performed by mass spectrometry instead of emission analysis in the laser ICP method.
- Nb segregation degree 2.1
- Ti segregation degree 1.8
- Mn segregation degree 1.3
- Nb segregation degree / Mn segregation degree ( ⁇ ) 1.
- Ti segregation degree / Mn segregation degree ( ⁇ ) 1.4.
- FIG. 2A is a graph using the data of FIG. 1 with the horizontal axis representing the Mn concentration and the vertical axis representing the Nb concentration.
- FIG. 2B illustrates the horizontal axis representing the Mn concentration and the vertical axis representing the Ti concentration. It is a graph. The concentration of each element actually uses the emission peak intensity. By comparing these graphs, the degree of Mn segregation and the degree of Nb segregation or Ti segregation can be compared.
- the segregation degree of Mn represents the segregation of each element in the slab. If the segregation degree of slab (Mn segregation degree) deteriorates, the segregation degree of Nb and Ti It can be seen that the degree of segregation deteriorates as well. Furthermore, it has also been found that when the Mn segregation degree exceeds a certain critical point, Nb and Ti tend to precipitate as inclusions all at once as shown in circles in these figures.
- the present inventors consider that inclusions generated in large quantities can cause HIC, and the presence / absence of HIC, Nb segregation degree / Mn segregation degree ( ⁇ ), and Ti segregation degree / Mn segregation degree ( ⁇ ).
- the relationship was investigated.
- the Nb segregation degree is 2.0 or less
- the ratio of Nb segregation degree / Mn segregation degree ⁇ is 1.0 or more and 1.5 or less
- the Ti segregation degree is 2.0 or less. It has been found that the occurrence of HIC can be remarkably suppressed when ⁇ , which is the ratio of segregation degree / Mn segregation degree, is 1.0 or more and 1.5 or less.
- the determination criterion for the presence or absence of HIC occurrence according to the present invention is particularly effective with respect to the HIC resistance of high-strength steel of X60 grade or higher, which cannot be determined only by a conventionally known determination criterion. It goes without saying that the generation of HIC can be effectively prevented by using the criteria for the segregation degree of Nb and Ti according to the present invention together with the conventionally proposed reduction of C, Mn, P and S.
- the thick steel plate according to the present invention can be manufactured by setting the steelmaking and rolling conditions so that segregation does not easily occur.
- the operating conditions effective for reducing segregation are briefly described below.
- Water cooling is effective because it can reduce the diffusion of elements such as C and P as much as possible and prevent C from being combined with Nb. Although the diffusion rate of each element decreases with a decrease in temperature, if it is allowed to cool without water cooling after rolling, it may take a longer time to be exposed to a higher temperature, which may promote element diffusion. The diffused elements segregate at the grain boundaries and inclusions.
- the water cooling rate is desirably 5 ° C./sec or more and 30 ° C./sec or less. This is because if the water cooling rate is less than 5 ° C./sec, diffusion is promoted, and if the water cooling rate exceeds 30 ° C./sec, baking occurs excessively and a hardened structure is generated.
- the UOE steel pipe manufactured using the thick steel plate according to the present invention does not generate HIC due to coarse carbonitrides of Ti and Nb, and is highly reliable when used in a corrosive environment.
- a method for manufacturing a UOE steel pipe is well known to those skilled in the art.
- a UOE steel pipe can be manufactured by a method similar to the conventional technique.
- the obtained slab is heated to about 1100 ° C. or more and 1200 ° C. or less, and hot-rolled under conditions where the finish rolling temperature is about 750 ° C. or more and 850 ° C. or less, and finished to a thickness of about 25.4 mm. It was. Immediately after the hot rolling, water cooling was performed, cooling was stopped at about 450 ° C. or more and 550 ° C. or less, and then air cooling was performed. The cooling rate of water cooling was 10 to 30 ° C./sec.
- the steel plate of the invention steel having a small segregation degree ratio ⁇ and ⁇ of Nb and Ti as small as 1.5 or less has a strength of X60 grade or higher, a tensile strength of 520 MPa or higher, and an HIC generation rate. (CAR) was 3% or less. Accordingly, it is obvious to those skilled in the art that a highly reliable UOE steel pipe can be manufactured from this thick steel plate.
- steel types Nos. 4, 11 and 12 have the chemical composition of the steel satisfying the conditions specified in the present invention, but regarding the degree of segregation, the value of Nb segregation degree, the ratio of Nb segregation degree / Mn segregation degree ( ⁇ ) Or Ti segregation degree / Mn segregation degree ratio ( ⁇ ) is an example that does not satisfy the scope of the present invention, and in all cases the strength is sufficient, but the HIC generation rate is high.
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Abstract
Description
(3)特許文献5~7には、最近求められるようになってきた鋼材の強度スペックの向上に伴って、上記の中心偏析部やMnS生成に対する単独対策では不十分な場合が多くなってきたことから、鋼中にCuやNiを添加することにより、鋼材表面に保護被膜を形成して、鋼中への水素の侵入を抑制するとともに、CrやMo等の添加や圧延時の加工熱処理(TMCP,thermomechanical control process)を併用することが開示されている。 Patent Documents 3 and 4 disclose that the center segregation itself is eliminated by rolling the slab once after bulging the slab at the stage where the continuously cast unsolidified molten steel remains.
(3) In Patent Documents 5 to 7, with the improvement of the strength specifications of steel materials that have recently been demanded, the single countermeasures against the above-mentioned central segregation part and MnS generation have become insufficient in many cases. Therefore, by adding Cu or Ni to the steel, a protective film is formed on the surface of the steel material to suppress the intrusion of hydrogen into the steel, and the addition of Cr, Mo, etc. or the heat treatment during rolling ( It is disclosed that TMCP (thermomechanical control process) is used in combination.
式(1):0.1%<(Cu+Ni+Cr+Mo)<1.5%
上記式中、元素記号は各元素の含有量(質量%)を意味する。 The present invention, in mass%, C: 0.02 to 0.07%, Si: 0.05 to 0.50%, Mn: 1.1 to 1.6%, P: 0.015% or less, S : 0.002% or less, Nb: 0.005 to 0.060%, Ti: 0.005 to 0.030%, Al: 0.005 to 0.06%, Ca: 0.0005 to 0.0006% , N: 0.0015 to 0.007%, at least one selected from Cu, Ni, Cr and Mo in an amount satisfying the formula (1), V: 0 to 0.10%, balance Fe and impurities Nb segregation degree is 2.0 or less, ratio α of Nb segregation degree to Mn segregation degree (α = Nb segregation degree / Mn segregation degree) is 1.0 or more and 1.5 or less, Ti HIC resistance characterized by having a segregation degree of 2.0 or less and a ratio of Ti segregation degree to Mn segregation degree β (β = Ti segregation degree / Mn segregation degree) of 1.0 or more and 1.5 or less. There is an excellent thick steel plate to sex:
Formula (1): 0.1% <(Cu + Ni + Cr + Mo) <1.5%
In said formula, an element symbol means content (mass%) of each element.
UOE鋼管は、厚鋼板をU型、次にO型にプレス成形し、板の突き合わせ部をサブマージアーク溶接した後、内側からエキスパンダーで拡管して所定寸法に仕上げることにより製造される。 From another point of view, the present invention is a UOE steel pipe characterized by using the above-mentioned HIC thick steel plate as a material.
The UOE steel pipe is manufactured by press-forming a thick steel plate into a U shape and then an O shape, and submerging arc welding the butt portion of the plate, and then expanding the tube with an expander from the inside and finishing it to a predetermined size.
[C:0.02%以上、0.07%以下]
一般に、Cは、鋼の強度に大きな影響を及ぼす元素として知られる。C含有量が0.02%未満ではラインパイプ等の用途に対して所定の強度を得ることが困難となる。一方、C含有量が0.07%を超えると、上述したように連続鋳造時には鋳片の厚み中心部にマクロ偏析部を形成し、HICの発生原因となる。そのため、C含有量は0.02%以上、0.07%以下とする。上記観点からC含有量の下限は0.03%であることが望ましく、その上限は0.06%であることが望ましい。 The chemical composition of the thick steel plate according to the present invention is as described below. In the following description, all percentages relating to the chemical composition of steel mean mass%.
[C: 0.02% or more, 0.07% or less]
In general, C is known as an element that greatly affects the strength of steel. If the C content is less than 0.02%, it is difficult to obtain a predetermined strength for applications such as line pipes. On the other hand, if the C content exceeds 0.07%, as described above, a macro-segregation portion is formed at the thickness center portion of the slab during continuous casting, which causes generation of HIC. Therefore, the C content is set to 0.02% or more and 0.07% or less. From the above viewpoint, the lower limit of the C content is preferably 0.03%, and the upper limit is preferably 0.06%.
Siは、0.05%以上含有させた場合に、一般に鋼の製造プロセスでは脱酸元素として作用し、鋼中の酸素濃度を低減するのに有効である。また、Siは鋼を強化する効果もある。しかし、Si含有量が0.50%を超えると島状マルテンサイトの生成を引き起し、溶接時にHAZ(溶接熱影響部)の靱性を悪化させる。また、SiはTiとの間に強い相互作用を有することから、構成元素でないにもかかわらずTiNの生成に影響する。本発明においてHICの発生起点として注目するNb炭窒化物は、TiNを核として析出する可能性が高く、Si濃度が高くなりすぎると、HIC特性の劣化を引き起こす恐れがある。したがって、Si含有量は0.05%以上、0.50%以下とする。好ましいSi含有量は0.05%以上、0.3%未満である。 [Si: 0.05% or more, 0.50% or less]
When Si is contained in an amount of 0.05% or more, it generally acts as a deoxidizing element in the steel manufacturing process and is effective in reducing the oxygen concentration in the steel. Si also has the effect of strengthening steel. However, if the Si content exceeds 0.50%, island-shaped martensite is generated, and the toughness of the HAZ (welding heat affected zone) is deteriorated during welding. Further, since Si has a strong interaction with Ti, it affects the generation of TiN even though it is not a constituent element. In the present invention, Nb carbonitrides that are noted as the starting point of HIC generation are highly likely to precipitate with TiN as nuclei, and if the Si concentration becomes too high, there is a risk of deteriorating HIC characteristics. Therefore, the Si content is set to 0.05% or more and 0.50% or less. A preferable Si content is 0.05% or more and less than 0.3%.
Mnは,一般に鋼材の強度に大きな影響を与える元素であり、Mn含有量が1.1%未満では十分な強度を得ることが困難である。Mn含有量が1.6%を超えると、上述したようにMnが中心偏析部で濃化して、耐HIC特性を劣化させる。このため、Mn含有量は1.1%以上、1.6%以下とする。中心偏析部での耐HIC特性を確実に確保するために、Mn含有量は好ましくは1.1%以上、1.5%未満である。 [Mn: 1.1% or more and 1.6% or less]
Mn is an element that generally has a great influence on the strength of a steel material. If the Mn content is less than 1.1%, it is difficult to obtain sufficient strength. If the Mn content exceeds 1.6%, Mn concentrates at the center segregation part as described above, and the HIC resistance is deteriorated. For this reason, Mn content shall be 1.1% or more and 1.6% or less. In order to ensure the HIC resistance at the center segregation part, the Mn content is preferably 1.1% or more and less than 1.5%.
Pは、鋼中に不可避的に含有される不純物の一つであり、できるだけ低い方が好ましい。Pは、凝固時の固液界面における分配係数が小さく、著しく偏析する傾向があるので、上述したように中心偏析部で濃化して、耐HIC特性を劣化させる。そのため、P含有量の上限を0.015%とする。Pの中心偏析部における耐HIC特性の劣化をより確実に防止するためには、P含有量を0.008%未満とすることが好ましい。P含有量の下限は規定されないが、極端なP含有量の低減には相応のコスト上昇を伴うので、P含有量は0.004%以上とすることが望ましい。 [P: 0.015% or less]
P is one of impurities inevitably contained in the steel, and is preferably as low as possible. P has a small distribution coefficient at the solid-liquid interface during solidification and has a tendency to remarkably segregate. Therefore, as described above, P is concentrated at the central segregation portion to deteriorate the HIC resistance. Therefore, the upper limit of the P content is set to 0.015%. In order to more reliably prevent the deterioration of the HIC resistance in the central segregation portion of P, the P content is preferably less than 0.008%. Although the lower limit of the P content is not specified, the extreme reduction of the P content is accompanied by a corresponding increase in cost. Therefore, the P content is preferably 0.004% or more.
Sも鋼中に不可避的に含有される不純物の一つであり、できるだけ低い方が好ましい。Pと同様に、Sも凝固時の固液界面における分配係数が小さく、著しく偏析する傾向がある元素である。その上、上述したように、偏析部ではMnSを生成してHICの発生起点となる。このため、S含有量の上限を0.002%とする。高強度鋼のように、より要求レベルの厳しい条件で安定して耐HIC特性を得るためには、S含有量の上限を0.001%とすることが好ましい。S含有量の下限は規定されないが、極端なS含有量の低減には相応のコスト上昇を伴うので、S含有量は0.0003%以上とすることが望ましい。 [S: 0.002% or less]
S is one of the impurities inevitably contained in the steel and is preferably as low as possible. Like P, S is an element that has a small distribution coefficient at the solid-liquid interface during solidification and has a tendency to remarkably segregate. In addition, as described above, the segregation part generates MnS and becomes the starting point of HIC generation. For this reason, the upper limit of the S content is set to 0.002%. In order to obtain stable HIC resistance under more severe requirements such as high strength steel, the upper limit of the S content is preferably 0.001%. Although the lower limit of the S content is not specified, an extreme reduction in the S content is accompanied by a corresponding increase in cost, so the S content is preferably 0.0003% or more.
Nbは、鋼中で炭窒化物を形成して、鋼の強度を高めるとともに靱性の向上にも有効な元素である。そのため、Nbを0.005%以上含有させる。特にTMCPにおいては、固溶及び析出を制御することにより厚鋼板のミクロ組織を制御するためにNbが用いられる。この効果を得るためにも、Nbを0.005%以上含有させる。しかし、Nb含有量が0.060%を超えると、加熱時にも固溶せず、組織制御ができなくなる。同時にNb量の増加は、Nb炭窒化物量の増加を意味し、耐HIC特性の低下を引き起こす可能性がある。このためNb含有量は0.005%以上、0.060%以下とする。高強度鋼のように、より要求レベルの厳しい条件で安定して耐HIC特性を確保するためには、Nb含有量を0.010%以上、0.040%以下とすることが好ましい。 [Nb: 0.005% or more, 0.060% or less]
Nb is an element that forms carbonitrides in steel to increase the strength of the steel and is effective in improving toughness. Therefore, Nb is contained 0.005% or more. In particular, in TMCP, Nb is used to control the microstructure of the thick steel plate by controlling solid solution and precipitation. In order to obtain this effect, 0.005% or more of Nb is contained. However, if the Nb content exceeds 0.060%, it does not dissolve even during heating, and the structure cannot be controlled. At the same time, an increase in the amount of Nb means an increase in the amount of Nb carbonitride, which may cause a decrease in HIC resistance. For this reason, Nb content shall be 0.005% or more and 0.060% or less. In order to ensure stable HIC resistance under more severe requirements, such as high-strength steel, the Nb content is preferably 0.010% or more and 0.040% or less.
Tiは、鋼の強度を向上させるとともに、鋼中のNをTiNとして固定し、NbNやAlNの析出量を減少させることから、連続鋳造の鋳片の曲げ・矯正時のオーステナイト粒界へのNbNやAlNの動的析出に起因した鋳片表面割れを防止する効果もある。このような効果を得るために、Tiを0.005%以上含有させる。しかし、Ti含有量が0.030%を超えると、Ti炭化物が多数生成し、HAZ靱性を低下させるとともに、粗大なTiNが生成する原因となる。また、上述したようにNb炭窒化物はTiNを核として析出する可能性が高いため、粗大なTiNの存在は耐HIC特性の低下を引き起こす。このため、Ti含有量は0.005%以上、0.030%以下とする。好ましいTi含有量は0.010%以上、0.025%以下である。 [Ti: 0.005% or more, 0.030% or less]
Ti improves the strength of the steel, fixes N in the steel as TiN, and reduces the amount of precipitation of NbN and AlN. Therefore, NbN to the austenite grain boundary during bending and straightening of continuous cast slabs There is also an effect of preventing slab surface cracks caused by dynamic precipitation of AlN. In order to obtain such an effect, 0.005% or more of Ti is contained. However, if the Ti content exceeds 0.030%, a large number of Ti carbides are generated, which reduces HAZ toughness and causes coarse TiN to be generated. Further, as described above, since Nb carbonitride is highly likely to precipitate with TiN as a nucleus, the presence of coarse TiN causes a decrease in HIC resistance. For this reason, Ti content shall be 0.005% or more and 0.030% or less. A preferable Ti content is 0.010% or more and 0.025% or less.
Alも脱酸元素として鋼中の酸素濃度を低減するために有効な元素の一つである。脱酸のために必要となるAl含有量は0.005%以上となる。Al含有量がこれを下回ると、脱硫も不十分になる上、Ca添加の歩留まりが悪化し、その効果も充分得られなくなり、鋼中の硫化物やSの偏析に起因してHICが発生する。しかし、脱酸に伴い生成するアルミナはHICの原因となることがあるので、Al含有量は0.06%以下とする。同じ理由で、Al含有量は0.04%以下とすることが好ましい。 [Al: 0.005% or more, 0.06% or less]
Al is one of the elements effective for reducing the oxygen concentration in steel as a deoxidizing element. The Al content necessary for deoxidation is 0.005% or more. If the Al content is less than this, desulfurization will be insufficient, the yield of Ca addition will deteriorate, and the effect will not be sufficiently obtained, and HIC will occur due to the segregation of sulfides and S in the steel. . However, since the alumina produced by deoxidation may cause HIC, the Al content is set to 0.06% or less. For the same reason, the Al content is preferably 0.04% or less.
耐HIC鋼では、CaはS濃度を低減させ、MnSの生成を防止すると共に、硫化物の形態制御のために半ば必須の添加元素である。このため、Caを0.0005%以上含有させる。しかし、Ca含有量が0.0060%を超えると、その効果は飽和し、製造コストの増加を招く。このため、Ca含有量は0.0005%以上、0.0060%以下とする。 [Ca: 0.0005% or more, 0.0006% or less]
In HIC-resistant steel, Ca is a semi-essential additive element for reducing the S concentration, preventing the formation of MnS, and controlling the form of sulfide. For this reason, 0.0005% or more of Ca is contained. However, when the Ca content exceeds 0.0006%, the effect is saturated and the manufacturing cost increases. For this reason, Ca content shall be 0.0005% or more and 0.0006% or less.
Nは、鋼を転炉などの大気雰囲気で溶製する場合には鋼中に不可避的に侵入する元素である。Nは本発明で着目する粗大なNb炭窒化物の構成元素である。Nb炭窒化物は、直接Nと優先的に結びつくことはないが、晶出したTiNを核として析出することが知られている。Nは鋼材中でAlやTiなどと窒化物を形成する元素であり、これらの窒化物は熱間加工の過程でピン留め粒子として結晶粒を微細化する効果を有することから、鋼材の機械特性に影響を与えるとともに、ミクロ組織形成にも影響を与える。このため、Nを0.0015%以上の濃度とする必要がある。一方で、前述のようにこれらの窒化物が連続鋳造時にオーステナイト粒界に動的析出することにより、鋳片表面割れの原因となることから、Nの上限は0.007%となる。 [N: 0.0015% or more, 0.007% or less]
N is an element that inevitably enters the steel when the steel is melted in an air atmosphere such as a converter. N is a constituent element of coarse Nb carbonitride which is focused in the present invention. Nb carbonitrides are not directly associated with N preferentially, but are known to precipitate with crystallized TiN as nuclei. N is an element that forms nitrides with Al, Ti, etc. in steel materials, and these nitrides have the effect of refining crystal grains as pinned particles during the hot working process. Affects the formation of microstructures. For this reason, N needs to be a concentration of 0.0015% or more. On the other hand, as described above, these nitrides are dynamically precipitated at the austenite grain boundaries during continuous casting, causing cracks on the slab surface, so the upper limit of N is 0.007%.
(1)式に関して述べたように、上記各元素記号はその元素の含有量(質量%)を意味する。 [0.1% <(Cu + Ni + Cr + Mo) <1.5%]
As described with respect to the formula (1), each element symbol means the content (% by mass) of the element.
[V:0.10%以下]
Vは、鋼中でフェライト中への固溶並びに炭窒化物を形成して鋼の強度を高めるために有効であるので、特に高強度が要求される場合にはVを含有させてもよい。しかし、V含有量が0.1%を超えると、HAZ靱性に悪影響を与える。このため、Vを含有させる場合にはその含有量は0.10%以下とする。なお、Vによる上記効果を確実に得るには、V含有量は0.01%であることが望ましい。 Next, arbitrary elements will be described.
[V: 0.10% or less]
V is effective for increasing the strength of steel by forming a solid solution and carbonitride in ferrite in steel, and therefore V may be contained particularly when high strength is required. However, if the V content exceeds 0.1%, the HAZ toughness is adversely affected. For this reason, when it contains V, the content is made into 0.10% or less. In addition, in order to acquire the said effect by V reliably, it is desirable that V content is 0.01%.
[Nb偏析度:2.0以下;Nb偏析度/Mn偏析度(α):1.0以上、1.5以下]
[Ti偏析度:2.0以下;Ti偏析度/Mn偏析度(β):1.0以上、1.5以下]
「Mn偏析度」、「Nb偏析度」および「Ti偏析度」は、板厚中央部での偏析度であり、前述した通りに求められる。 Other than the above are Fe and impurities.
[Nb segregation degree: 2.0 or less; Nb segregation degree / Mn segregation degree (α): 1.0 or more, 1.5 or less]
[Ti segregation degree: 2.0 or less; Ti segregation degree / Mn segregation degree (β): 1.0 or more, 1.5 or less]
“Mn segregation degree”, “Nb segregation degree”, and “Ti segregation degree” are segregation degrees at the center of the plate thickness, and are determined as described above.
各元素の偏析度は、レーザーICP法により調査した。使用した装置は島津製作所製のレーザーICP分析装置であった。レーザーICP法は、サンプルの切断面に対しレーザービームを照射し、発生した蒸気をキャリアガスによって搬送し、誘導プラズマ中で発光させ、この光の波長と光度を分析して、各元素の定量分析を行う方法であり、発光分析の1種である。サンプルを1方向に移動させてレーザービームを照射し、分析を繰り返すことによって、各元素について一定長さにおける濃度変化を調べることができる。 The present inventors investigated the degree of segregation of each element at the center of the plate thickness from the rolled steel plate, and investigated the correlation with the presence or absence of HIC.
The degree of segregation of each element was investigated by the laser ICP method. The apparatus used was a laser ICP analyzer manufactured by Shimadzu Corporation. The laser ICP method irradiates a cut surface of a sample with a laser beam, conveys the generated vapor with a carrier gas, emits light in induction plasma, analyzes the wavelength and intensity of this light, and quantitatively analyzes each element. This is a type of emission analysis. By moving the sample in one direction, irradiating a laser beam, and repeating the analysis, it is possible to examine the concentration change at a certain length for each element.
次工程である連続鋳造(CC)では、鋳片の中心部が凝固する際に鋳片の凝固収縮量に相当する程度、あるいはやや上回る程度に鋳片に勾配を設けることで、板厚方向の偏析の低減を図ることできる。一方、鋳込み幅方向と鋳込み長さ方向で顕著な凝固不均一が発生しないように、適正な水冷条件の採用および鋳込み速度の選択も偏析低減に有効である。 In steelmaking, application of IR (injection refining) and control of oxide morphology by adding Ca are effective in reducing segregation.
In the next process, continuous casting (CC), when the center part of the slab solidifies, the slab is provided with a gradient to the extent corresponding to or slightly above the solidification shrinkage of the slab. Segregation can be reduced. On the other hand, the use of appropriate water-cooling conditions and the selection of the casting speed are also effective in reducing segregation so that significant solidification non-uniformity does not occur in the casting width direction and the casting length direction.
表1に示す化学組成とAr3点を有する鋼種No.1~14を、厚さ300mm、幅2300mmの垂直曲げ型連続鋳造機を用いて、0.7m/min以上、0.8m/min以下の鋳造速度で連続鋳造して鋳片(スラブ)を得た。 The present invention will be described more specifically with reference to examples.
Using steel type Nos. 1 to 14 having the chemical composition and Ar 3 points shown in Table 1 and a vertical bending type continuous casting machine having a thickness of 300 mm and a width of 2300 mm, they are 0.7 m / min or more and 0.8 m / min or less. A slab was obtained by continuous casting at a casting speed of.
HIC試験は、NACE TM-02-84で規定されるNACE試験に供し、HIC発生率として割れ面積率(CAR, Crack Area Ratio)を測定した。CARが3%以下を合格と判定し、3%を超える場合は実質的なHIC発生ありとして、不合格であると判定した。 About this thick steel plate, the segregation degree investigation (
The HIC test was subjected to the NACE test specified by NACE TM-02-84, and the crack area ratio (CAR) was measured as the HIC generation rate. When CAR was 3% or less, it was determined to be acceptable, and when it exceeded 3%, it was determined that there was substantial HIC occurrence and that it was rejected.
On the other hand, either the strength or the HIC occurrence rate was unsatisfactory for the thick steel plate of the comparative steel. In particular, steel types Nos. 4, 11 and 12 have the chemical composition of the steel satisfying the conditions specified in the present invention, but regarding the degree of segregation, the value of Nb segregation degree, the ratio of Nb segregation degree / Mn segregation degree (α ) Or Ti segregation degree / Mn segregation degree ratio (β) is an example that does not satisfy the scope of the present invention, and in all cases the strength is sufficient, but the HIC generation rate is high.
Claims (3)
- 質量%で、C:0.02~0.07%、Si:0.05~0.50%、Mn:1.1~1.6%、P:0.015%以下、S:0.002%以下、Nb:0.005~0.060%、Ti:0.005~0.030%、Al:0.005~0.06%、Ca:0.0005~0.0060%、N:0.0015~0.007%、式(1)を満足する量のCu、Ni、CrおよびMoから選ばれた少なくとも1種、V:0~0.10%、残部Feおよび不純物からなる化学組成を有し、かつNb偏析度が2.0以下、Mn偏析度に対するNb偏析度の比α(α=Nb偏析度/Mn偏析度)が1.0以上、1.5以下、Ti偏析度が2.0以下、Mn偏析度に対するTi偏析度の比β(β=Ti偏析度/Mn偏析度)が1.0以上、1.5以下であることを特徴する、耐HIC特性に優れた厚鋼板。
式(1):0.1%<(Cu+Ni+Cr+Mo)<1.5%
式中、元素記号は各元素の含有量(質量%)を意味する。 By mass%, C: 0.02 to 0.07%, Si: 0.05 to 0.50%, Mn: 1.1 to 1.6%, P: 0.015% or less, S: 0.002 %, Nb: 0.005 to 0.060%, Ti: 0.005 to 0.030%, Al: 0.005 to 0.06%, Ca: 0.0005 to 0.0006%, N: 0 A chemical composition consisting of .0015 to 0.007%, at least one selected from Cu, Ni, Cr and Mo in an amount satisfying the formula (1), V: 0 to 0.10%, the balance Fe and impurities. And Nb segregation degree is 2.0 or less, ratio α of Nb segregation degree to Mn segregation degree (α = Nb segregation degree / Mn segregation degree) is 1.0 or more and 1.5 or less, and Ti segregation degree is 2 Excellent HIC resistance, characterized in that the ratio β of Ti segregation to Mn segregation is β or less (β = Ti segregation / Mn segregation) is 1.0 or more and 1.5 or less. Thick steel plate.
Formula (1): 0.1% <(Cu + Ni + Cr + Mo) <1.5%
In the formula, the element symbol means the content (% by mass) of each element. - 前記化学組成が0.01~0.10%のVを含有する、請求項1に記載の厚鋼板。 The thick steel plate according to claim 1, wherein the chemical composition contains V of 0.01 to 0.10%.
- 請求項1または2に記載の厚鋼板を素材とすることを特徴とするUOE鋼管。 A UOE steel pipe made of the thick steel plate according to claim 1 or 2.
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2011503869A JPWO2010104165A1 (en) | 2009-03-12 | 2010-03-12 | HIC thick steel plate and UOE steel pipe |
CN2010800209055A CN102421926A (en) | 2009-03-12 | 2010-03-12 | HIC-resistant thick steel sheet and UOE steel pipe |
EP10750916.8A EP2407570A4 (en) | 2009-03-12 | 2010-03-12 | Hic-resistant thick steel sheet and uoe steel pipe |
RU2011141268/02A RU2011141268A (en) | 2009-03-12 | 2010-03-12 | THICK-STEEL STEEL RESISTANT TO HYDROGEN CRACKING AND THE STEEL PIPE MADE BY UOE TECHNOLOGY |
CA2755271A CA2755271A1 (en) | 2009-03-12 | 2010-03-12 | Hic-resistant thick steel plate and uoe steel pipe |
US13/228,819 US20120121453A1 (en) | 2009-03-12 | 2011-09-09 | Hic-resistant thick steel plate and uoe steel pipe |
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JP2009-059639 | 2009-03-12 |
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US13/228,819 Continuation US20120121453A1 (en) | 2009-03-12 | 2011-09-09 | Hic-resistant thick steel plate and uoe steel pipe |
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US (1) | US20120121453A1 (en) |
EP (1) | EP2407570A4 (en) |
JP (1) | JPWO2010104165A1 (en) |
KR (1) | KR20110123807A (en) |
CN (1) | CN102421926A (en) |
CA (1) | CA2755271A1 (en) |
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JP5177310B2 (en) * | 2011-02-15 | 2013-04-03 | Jfeスチール株式会社 | High tensile strength steel sheet with excellent low temperature toughness of weld heat affected zone and method for producing the same |
JP6044247B2 (en) * | 2011-12-13 | 2016-12-14 | Jfeスチール株式会社 | Method for evaluating the resistance to hydrogen cracking of steel materials and steel sheets for high strength sour line pipes with good resistance to hydrogen cracking |
JP5565420B2 (en) * | 2012-02-02 | 2014-08-06 | 新日鐵住金株式会社 | UOE steel pipe for line pipe |
WO2013190750A1 (en) * | 2012-06-18 | 2013-12-27 | Jfeスチール株式会社 | Thick, high-strength, sour-resistant line pipe and method for producing same |
RU2621093C2 (en) * | 2012-07-09 | 2017-05-31 | ДжФЕ СТИЛ КОРПОРЕЙШН | Thick-walled high tensile sulphurous-gas resistant main pipe and method for its manufacture |
WO2014024234A1 (en) * | 2012-08-10 | 2014-02-13 | Nippon Steel & Sumitomo Metal Corporation | Steel plate for high strength steel pipe and high strength steel pipe |
CN112760464A (en) * | 2019-10-21 | 2021-05-07 | 宝山钢铁股份有限公司 | Normalizing type low-yield-ratio UOE welded pipe and manufacturing method thereof |
CN113462885A (en) * | 2021-06-07 | 2021-10-01 | 山西太钢不锈钢股份有限公司 | Dynamic positioning method applied to narrow space of heating furnace |
CN117358778B (en) * | 2023-12-08 | 2024-03-08 | 成都先进金属材料产业技术研究院股份有限公司 | Titanium alloy seamless tube and preparation method thereof |
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2010
- 2010-03-12 JP JP2011503869A patent/JPWO2010104165A1/en active Pending
- 2010-03-12 CN CN2010800209055A patent/CN102421926A/en active Pending
- 2010-03-12 CA CA2755271A patent/CA2755271A1/en not_active Abandoned
- 2010-03-12 KR KR1020117023642A patent/KR20110123807A/en not_active Application Discontinuation
- 2010-03-12 EP EP10750916.8A patent/EP2407570A4/en not_active Withdrawn
- 2010-03-12 RU RU2011141268/02A patent/RU2011141268A/en unknown
- 2010-03-12 WO PCT/JP2010/054173 patent/WO2010104165A1/en active Application Filing
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Also Published As
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CN102421926A (en) | 2012-04-18 |
RU2011141268A (en) | 2013-04-20 |
EP2407570A4 (en) | 2016-06-22 |
CA2755271A1 (en) | 2010-09-16 |
JPWO2010104165A1 (en) | 2012-09-13 |
KR20110123807A (en) | 2011-11-15 |
US20120121453A1 (en) | 2012-05-17 |
EP2407570A1 (en) | 2012-01-18 |
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