WO2011102244A1 - 耐疲労亀裂進展特性および耐食性に優れた鋼材並びにその製造方法 - Google Patents
耐疲労亀裂進展特性および耐食性に優れた鋼材並びにその製造方法 Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
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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
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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
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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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
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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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
- C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
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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 steel material suitable for use in a hull, a civil engineering structure, a construction machine, a hydraulic iron pipe, an offshore structure, a line pipe, and other welded structures that require fatigue crack growth resistance and corrosion resistance, and a manufacturing method thereof. About.
- Patent Document 1 proposes a technique for reducing the residual stress in the weld joint by reducing the high-temperature strength by utilizing a ferrite phase having a lower strength than the austenite phase at the same temperature.
- a ferrite phase having a lower strength than the austenite phase at the same temperature.
- welded steel structures are often used in environments where there is a large amount of incoming salt, such as beach areas and areas where snow melting salt is spread, and in the shipbuilding field, they are often used in seawater spray environments.
- weathering steel is used for structures such as bridges as a minimum maintenance steel that can be used as it is without being painted.
- a protective rust layer is formed on the surface of weathering steel not only in the beach area but also in inland areas where there is a large amount of incoming salt, such as areas where snowmelt salt and antifreeze are sprayed. Since it is hard to be done, the effect which suppresses corrosion is hard to be exhibited. Therefore, in these regions, it is not possible to use bare weatherproof steel, and ordinary steel is used by painting on ordinary steel. However, in the case of using such ordinary steel for coating, it is necessary to repaint every 10 years because of coating deterioration due to corrosion, and therefore the cost required for maintenance becomes enormous.
- Ni-based high weathering steel to which about 1 to 3% of Ni is added has been developed.
- the salt in an environment where snow melting salt or anti-freezing agent is sprayed on the road, the salt is wound up on the running car and adheres to the bridge that supports the road, resulting in a severe corrosive environment. Furthermore, the eaves under the eaves a little away from the coast are also exposed to severe salt damage environments, and in such areas, the amount of incoming salt becomes a severe corrosive environment with 1 mdd or more.
- Patent Document 3 proposes a weather-resistant steel material having an increased chromium (Cr) content
- Patent Document 4 proposes a weather-resistant steel material having an increased nickel (Ni) content.
- the steel material having the effect of suppressing fatigue crack growth and the steel material having corrosion resistance as described above have the following problems.
- Patent Document 1 requires high-concentration Al addition to make the ferrite phase exist in a wider temperature range.
- Al contributes to the formation of a ferrite phase, but is an element that significantly reduces toughness, which is one of the basic characteristics required for structural steel materials.
- the toughness itself against a static load is insufficient.
- the design of the shape and dimensions of the structural material needs to be carried out not only from the viewpoint of fatigue strength but also from the viewpoint of preventing brittle fracture against static loads. With the technique proposed in Patent Document 1, the strength and soundness are improved. The balance cannot be improved.
- the weathering steel material which increased chromium (Cr) content proposed by the said patent document 3 can improve a weather resistance in the area
- paint peel resistance is a major problem in welded steel structures used in environments with a large amount of incoming salt. That is, as shown above, in a coastal environment where a large amount of chloride comes in or an environment where a snow melting agent or an antifreezing agent is sprayed, the coating peels off early and corrosion progresses. Therefore, it is necessary to repaint the paint every few to a few dozen years. In addition, when repainting is performed, it is necessary to assemble a scaffold on a once-corroded bridge and perform a reblasting process as a previous process, which is very expensive.
- the paint peel resistance is largely due to the characteristics including the corrosion resistance of the steel material as the base.
- the present invention has been made to solve such a problem, and does not contain a large amount of elements that inhibit toughness such as Al and B, and a steel material excellent in fatigue crack growth resistance and corrosion resistance and its
- the object is to provide a manufacturing method.
- the above-mentioned corrosion resistance refers to corrosion resistance in a high chloride environment (coating does not peel off, corrosion at the coating defect part is suppressed and corrosion resistance is maintained (paint peeling resistance), and weather resistance when no coating is applied. Means).
- the present inventors first conducted a study focusing on the correlation between the fatigue characteristics of a welded joint and the cleanliness of inclusions present in the steel material. It was found that there was no correlation between the joint fatigue characteristics.
- the joint fatigue characteristics greatly depend on the characteristics of the steel surface, and that improving the cleanliness improves the joint fatigue characteristics. did. More specifically, the inclusion analysis was limited to the region from the steel sheet surface to a depth of 2 mm in the thickness direction, the cleanliness was obtained for each steel sheet, and the correlation with the joint fatigue characteristics was examined. It was recognized that there was. The reason why such a correlation is recognized is that the steel surface has a large amount of displacement and is likely to start fatigue cracks.
- inclusions do not deform even under high stress because of their high hardness.
- the amount of displacement is large on the steel surface, it is considered that a crack occurs at the interface between the inclusion and the base structure, and the fatigue characteristics deteriorate. Therefore, the cleanliness of inclusions is usually a problem in the central part of the steel plate thickness, but the cleanliness of the steel surface is a problem with regard to fatigue characteristics.
- the present inventors examined corrosion in an environment with a large amount of incoming salt. As a result, in such an environment, repeated drying and wetting of the FeCl 3 solution became an essential condition of corrosion, and due to hydrolysis of Fe 3+ It has been found that corrosion is accelerated by lowering the pH and by Fe 3+ acting as an oxidizing agent.
- the corrosion reaction at this time is as shown below.
- Fe 2+ generated by the reaction of the above formula (1) is oxidized to Fe 3+ by air oxidation, and the generated Fe 3+ acts again as an oxidant to accelerate corrosion.
- the reaction rate of air oxidation of Fe 2+ is generally slow in a low pH environment, but is accelerated in a concentrated chloride solution, and Fe 3+ is easily generated. It has been found that due to such a cyclic reaction, in an environment where the amount of incoming salt is very large, Fe 3+ is always supplied, corrosion of steel is accelerated, and corrosion resistance is significantly deteriorated.
- the present inventors examined the influence of various alloy elements on the weather resistance based on the corrosion mechanism in such a salt environment, and as a result, obtained the findings shown in the following (a) to (c).
- Sn dissolves as Sn 2+, by lowering the concentration of Fe 3+ by 2Fe 3+ + Sn 2+ ⁇ 2Fe 2+ + Sn 4+ becomes reactions, (1) inhibit the reaction of formula. Sn also has an effect of suppressing anodic dissolution.
- Cu is an element that has traditionally been the basis for improving corrosion resistance in an environment with a large amount of incoming salt, and the effect of improving corrosion resistance is seen in an environment with a relatively long wetting time.
- a relatively dry environment in which salt is deposited and wet and dry are repeated due to changes in humidity and ⁇ -FeOOH is generated. Then, it was found that Cu rather promotes corrosion.
- the present invention has been completed based on such findings, and the gist of the present invention is the steel materials having excellent fatigue crack growth characteristics and corrosion resistance shown in the following (1) to (6), and the following (7 ) And (8) are methods for producing a steel material excellent in fatigue crack growth resistance and corrosion resistance.
- a steel material excellent in fatigue crack growth resistance and corrosion resistance characterized by being 4 or less.
- each element symbol in the above formula means the content (% by mass) of each element. When the content of each element is at the impurity level, 0 (zero) is substituted.
- a steel material excellent in fatigue crack growth resistance and corrosion resistance according to any one of the above (1) to (4), further comprising, by mass%, Ti: 0.05% or less.
- a method for producing a steel material having excellent fatigue crack growth characteristics and corrosion resistance characterized by comprising the following steps A to D and having a recuperation temperature width of 70 ° C. or less after completion of cooling in step D .
- Step A A step of blowing an inert gas into the molten steel under the conditions satisfying the following formula (3):
- Step C A step of heating the obtained steel slab to 900 to 1180 ° C. and then hot rolling under a condition that the finishing temperature is 650 to 1000 ° C.
- Step D The obtained hot-rolled material is acceleratedly cooled from the temperature range of 620 to 950 ° C. under the condition that the average cooling rate in the temperature range of 620 to 500 ° C. is 5 to 50 ° C./sec. The process of finishing cooling in the temperature range.
- G 1 Inert gas flow rate (NL / min) blown into molten steel
- H 1 Distance from the tip of the inert gas blowing nozzle to the molten steel surface (m)
- t 1 inert gas blowing time (min)
- S 1 Ladle molten steel amount (ton)
- D 1 Ladle inner diameter (m)
- a method for producing a steel material having excellent fatigue crack growth characteristics and corrosion resistance comprising the following steps A1 to D, and having a recuperation temperature width of 70 ° C. or less after completion of cooling in step D .
- Step A1 A step of subjecting the molten steel to a vacuum refining treatment under the conditions satisfying the following formula (4):
- Step B Continuously casting the obtained molten steel to obtain a steel piece having the chemical composition of any one of (1) to (6) above
- Step C A step of heating the obtained steel slab to 900 to 1180 ° C. and then hot rolling under a condition that the finishing temperature is 650 to 1000 ° C.
- Step D The obtained hot-rolled material is acceleratedly cooled from the temperature range of 620 to 950 ° C. under the condition that the average cooling rate in the temperature range of 620 to 500 ° C. is 5 to 50 ° C./sec. The process of finishing cooling in the temperature range.
- G 2 Inert gas flow rate used for molten steel reflux (NL / min)
- D 2 inner diameter of dip tube (m)
- t 2 Vacuum processing time (min)
- S 2 Ladle molten steel amount (ton)
- the steel material of the present invention is excellent in fatigue crack growth resistance and corrosion resistance
- a welded structure that requires fatigue crack growth resistance such as a hull, civil engineering structure, construction machine, hydraulic iron pipe, offshore structure, line pipe, etc. Suitable for use with things.
- C 0.01 to 0.14% C is an element necessary for ensuring strength. If the content is less than 0.01%, the required strength cannot be ensured. However, if the content exceeds 0.14%, it becomes difficult to ensure toughness in both the heat affected zone (HAZ) and the base material when welding. Therefore, the C content is set to 0.01 to 0.14%.
- the preferable lower limit of the C content is 0.03%, and the preferable upper limit is 0.10%.
- Si 0.04 to 0.6%
- Si has a deoxidizing action and contributes to an increase in the strength of the steel material. In order to obtain these effects, it is necessary to contain Si by 0.04% or more. However, if its content exceeds 0.6%, toughness is reduced. Therefore, the Si content is 0.04 to 0.6%.
- Mn 0.5 to 2.0% Mn has an effect of enhancing the hardenability of steel and is an effective component for securing the strength. If the content is less than 0.5%, the hardenability is insufficient and the desired strength and toughness cannot be obtained. However, if Mn is contained in an amount exceeding 2.0%, segregation increases and hardenability increases too much, and the toughness of both the heat affected zone and the base metal decreases during welding. Therefore, the Mn content is 0.5 to 2.0%.
- P 0.01% or less P is unavoidably present in steel as an impurity. If its content exceeds 0.01%, it not only segregates at the grain boundaries and lowers toughness, but also causes hot cracking during welding. Therefore, the content of P needs to be limited to 0.01% or less. The smaller the P, the better.
- S 0.003% or less S is unavoidably present in steel as an impurity.
- the S content needs to be limited to 0.003% or less. The smaller the S, the better.
- Cu Less than 0.2% Cu is generally regarded as a basic element for improving weather resistance, and is added to all beach weather resistant steels and corrosion resistant steels, but in a relatively dry environment under high flying salt. Rather, it reduces the corrosion resistance. Further, if it coexists with Sn, cracking occurs during rolling. Therefore, it is necessary to reduce the Cu content. Even if contained as an impurity, the Cu content needs to be less than 0.2%. Preferably it is less than 0.1%.
- B More than 0.0007% and 0.005% or less B is an element having an effect of improving hardenability and increasing strength. In order to acquire this effect, it is necessary to make it contain exceeding 0.0007%. However, if the content exceeds 0.005%, the fatigue characteristics deteriorate. Therefore, the B content is more than 0.0007% and not more than 0.005%.
- Al less than 0.05%
- Al is an element having a deoxidizing action.
- toughness tends to deteriorate mainly in the weld heat affected zone. This is presumably because coarse cluster-like alumina inclusion particles are easily formed. Therefore, the Al content is less than 0.05%.
- N 0.007% or less
- N is an element unavoidably present in steel as an impurity. When present in a large amount, it causes deterioration of the toughness of the base metal and the weld heat affected zone. Therefore, the N content is 0.007% or less. The smaller N, the better.
- O 0.003% or less
- O (oxygen) is an element unavoidably present in steel as an impurity.
- the content exceeds 0.003%, the base material toughness and ductility such as stretch drawing are adversely affected. Therefore, the O content is limited to 0.003% or less.
- Sn 0.03 to 0.50% Sn dissolves as Sn 2+ and has an action of inhibiting corrosion by an inhibitor action in an acidic chloride solution. Further, rapidly to reduce the Fe 3+, by having an effect of reducing Fe 3+ concentration as oxidizing agent, since inhibit corrosion promoting effect of Fe 3+, thereby improving the weather resistance in high airborne salt environments. Moreover, Sn has the effect
- Cu / Sn ratio 1 or less
- the corrosion resistance is significantly reduced by the inclusion of Cu.
- the steel material according to the present invention has the chemical composition described above, and the balance is made of Fe and impurities.
- the impurities are components that are mixed due to various factors of the manufacturing process including raw materials such as ore and scrap when industrially manufacturing steel materials, and in a range that does not adversely affect the present invention. It means what is allowed.
- the steel material of the present invention may contain one or more components selected from at least one of the following first group to fifth group, if necessary.
- first group to fifth group if necessary.
- Mo has an effect of improving the strength and toughness of the base material, and may be contained as necessary. However, if the content exceeds 1.0%, the hardness of the weld heat affected zone is mainly increased, and the toughness and SSC resistance are impaired. Therefore, when Mo is contained, the content is preferably 1.0% or less. In addition, in order to acquire this effect stably, it is preferable to make it contain 0.05% or more.
- V 0.1% or less
- V has an effect of improving the strength of the base material mainly by precipitation of carbonitride during tempering, and may be contained as necessary. However, if the content exceeds 0.1%, the performance improvement effect of the base material is saturated, leading to toughness deterioration. Therefore, when V is contained, the content is preferably 0.1% or less. In addition, in order to acquire this effect stably, it is preferable to make it contain 0.005% or more.
- Nb 0.1% or less Since Nb has the effect of improving the strength and toughness of the base material by refining and precipitation of carbides, it may be contained as necessary. However, if the content exceeds 0.1%, the above effect is saturated, but the toughness of the weld heat affected zone is significantly impaired. Therefore, when Nb is contained, the content is preferably 0.1% or less. In addition, in order to acquire this effect stably, it is preferable to make it contain 0.005% or more.
- Ni Ni 1.5% or less
- Ni has an effect of increasing the toughness of a steel matrix (material) in a solid solution state, and may be contained as necessary.
- the content is preferably 1.5% or less.
- Group 3 Cr Cr: 1.2% or less Since Cr has the effect of enhancing the corrosion resistance of carbon dioxide gas and enhancing the hardenability, it may be contained if necessary. However, if the content exceeds 1.2%, even if other component conditions are satisfied, not only is it difficult to suppress the hardening of the weld heat-affected zone, but the carbon dioxide corrosion resistance improvement effect is saturated. Therefore, when Cr is contained, the content is preferably 1.2% or less. In addition, in order to acquire this effect stably, it is preferable to make it contain 0.05% or more.
- Ti Ti acts as a deoxidizing element and forms an oxide phase composed of Ti and Mn, and in particular refines the structure in the heat-affected zone of high heat input welding, thereby improving fatigue characteristics. Therefore, it may be contained as necessary. However, if the content exceeds 0.05%, the oxide to be formed becomes Ti oxide or Ti-Al oxide and the dispersion density decreases, and the structure in the heat-affected zone of the high heat input weld zone becomes finer. Lost the ability to For this reason, when Ti is contained, the content is preferably 0.05% or less. More preferred is less than 0.02%. More preferably, it is 0.018% or less. In order to stably form this oxide phase in steel, it is preferable that the total amount of Ti in the steel is 0.003% or more.
- Group 5 Ca, Mg Ca: 0.003% or less Ca reacts with S in steel to form oxysulfide (oxysulfide) in molten steel.
- oxysulfide oxysulfide
- this oxysulfide does not extend in the rolling direction during rolling and is spherical after rolling, so it suppresses weld cracks and hydrogen-induced cracks starting from cracks at the ends of stretched inclusions. Has the effect of Therefore, you may make it contain as needed. However, if its content exceeds 0.003%, toughness may be deteriorated. Therefore, when Ca is contained, the content is preferably 0.003% or less. In addition, in order to acquire this effect stably, it is preferable to make it contain 0.0005% or more.
- Mg forms an Mg-containing oxide, serves as a generation nucleus of TiN, and has the effect of finely dispersing TiN. Therefore, Mg may be contained as necessary. However, when the content exceeds 0.003%, the amount of oxide becomes excessive and ductility is reduced. Therefore, when Mg is contained, the content is preferably 0.003% or less. In addition, in order to acquire this effect stably, it is preferable to make it contain 0.0005% or more.
- the Bq value obtained from the following formula (1) needs to be 0.003 or less, and the Ceq value obtained from the following formula (2) is 0.15 to 0.35. It is necessary to be.
- each element symbol in the above formula means the content (% by mass) of each element. When the content of each element is at the impurity level, 0 (zero) is substituted.
- Bq 0.003 or less
- the Bq value defined by the above equation (1) is 0.0001 or more. It is more preferably 0.0005 or more, and further preferably 0.001 or more.
- Ceq 0.15-0.35 Ceq obtained from the above equation (2) is a so-called carbon equivalent, and is an index for evaluating the hardenability and weldability of a steel material and is generally used widely.
- the inventors of the present invention improve the fatigue properties of welded joints, and have a tensile strength (TS) generally used as structural steel of 500 MPa or more, and a Charpy absorbed energy value vE 0 at 0 ° C. of 27 J or more.
- TS tensile strength
- vE 0 at 0 ° C. Charpy absorbed energy value
- the Ceq value is set to 0.15 to 0.35%.
- the preferable minimum of Ceq is 0.20%.
- the preferable upper limit of Ceq is 0.30%.
- the steel material of this invention requires that the oxide number of the area
- the number of oxides is measured by the procedures shown in the following (i) to (iii).
- the above specimen is set in a scanning electron microscope (SEM) equipped with an energy dispersive X-ray fluorescence spectrometer (EDX), and a 0.05 mm square area is used as one field of view, and an area within 2 mm from the surface layer Five fields of view are observed at a magnification of 2000, and the number of oxides in each field of view is measured. At this time, the oxide is distinguished from other inclusions by composition analysis by EDX. Further, the number of oxides is measured by changing the depth in a region from the surface layer to a depth of 2 mm in order to avoid variation in the visual field.
- SEM scanning electron microscope
- EDX energy dispersive X-ray fluorescence spectrometer
- the oxide in the surface layer can be reduced by devising an inert gas blowing process or a vacuum refining process. Specifically, in performing the inert gas blowing process, it is effective to blow the inert gas into the molten steel under the conditions satisfying the following expression (3).
- the definitions of the symbols in the above formula (3) are as follows.
- G 1 Inert gas flow rate (NL / min) blown into molten steel
- H 1 Distance from the tip of the inert gas blowing nozzle to the molten steel surface
- t 1 inert gas blowing time (min)
- S 1 Ladle molten steel amount (ton)
- D 1 Ladle inner diameter (m)
- blowing can be performed while sufficiently stirring the bath. That is, at the beginning of blowing, the silicon in the hot metal is oxidized to become silica, which reacts with calcined lime and iron oxide added in the furnace and starts to form CaO—SiO 2 —FeO slag. At the same time, the furnace temperature rises and scrap melting begins to progress. In the initial stage of blowing, since the carbon concentration in the hot metal is high, the injected pure oxygen gas reacts efficiently with the carbon to become carbon monoxide and decarburization proceeds. At this stage, the supply rate of pure oxygen gas determines the decarburization. As the decarburization progresses, the temperature of the bath further increases.
- the decarburization reaction is controlled by the movement of carbon in the molten steel. Insufficient carbon movement due to stirring of molten steel, the injected pure oxygen gas is used to oxidize iron rather than react with carbon, and iron oxide increases in the slag, reducing the iron yield. To do. To prevent this, gas blowing from the furnace bottom is activated.
- the molten steel is placed in a decompressed vessel and the equilibrium partial pressure is lowered to remove the gas component in the molten steel as a condition that satisfies the above formula (4).
- casting is preferably performed by continuous casting.
- the segregation of the steel slab also adversely affects the toughness of the weld heat affected zone.
- C is 0.29% or less
- P is 0.30% or less
- Mn is 3.5%. The following management should be performed.
- electromagnetic brake is applied at 1000 to 5000 gauss for discharge flow rate control during casting
- electromagnetic stirring treatment is applied to unsolidified molten steel at 250 to 1000 gauss, and the final solidified part is about 1 mm / m.
- the steel sheet may be squeezed with a gradient and the concentrated segregated molten steel may be squeezed out from the final solidified portion.
- the steel slab produced in this way is preferably heated to a temperature range of 900 to 1180 ° C. and hot rolled.
- the steel slab once cooled to room temperature may be reheated, and maintained or heated to the above temperature through a soaking furnace without cooling to room temperature after continuous casting by a so-called direct feed rolling process.
- the heating temperature is less than 900 ° C.
- the reverse transformation to austenite becomes insufficient at the time of slab heating, and the subsequent characteristics deteriorate.
- the heating temperature exceeds 1180 ° C., the austenite crystal grains become coarse during the heating of the steel slab, and the toughness of the entire base metal as well as the center portion of the plate thickness decreases.
- the hot rolling finishing temperature is preferably 650 to 1000 ° C.
- the finishing temperature is less than 650 ° C.
- the deformation resistance of the steel increases, and it becomes difficult to finish the shape of the steel material after hot rolling to the target shape.
- the finishing temperature is high, the effect of crystal grain refinement by controlled rolling cannot be obtained, and the toughness of the base material cannot be ensured. Therefore, the upper limit of the finishing temperature is limited to 1000 ° C.
- the obtained hot-rolled material was accelerated and cooled from a temperature range of 620 to 950 ° C. under a condition that an average cooling rate in the temperature range of 620 to 500 ° C. was 5 to 50 ° C./second. Cooling should be terminated in the temperature range. Furthermore, the recuperation temperature range after the cooling is preferably 70 ° C. or less.
- Fatigue characteristics can be improved by cooling under such conditions.
- the average cooling rate in the temperature range of 620 to 500 ° C. is set to 5 to 50 ° C./sec.
- the cooling stop temperature in this cooling exceeds 500 ° C., the strength cannot be ensured because the formation of martensite or lower bainite becomes insufficient not only in the central part of the steel material but also in the surface layer part. Therefore, the cooling stop temperature is set to 500 ° C. or lower. Such heat treatment makes it easier to obtain a martensite or bainite structure. In the case of a steel material having the chemical composition of the present invention, it mainly has a bainite structure.
- a slab obtained by melting steel having a chemical composition shown in Table 1 in a converter and performing an inert gas blowing process or a vacuum refining process shown in Table 2 and then performing continuous casting is appropriately used.
- the steel plate for test was obtained by hot rolling and cooling to the plate thickness under the conditions shown in Table 3.
- the fatigue fracture life, the tensile strength and toughness of the weld heat affected zone, the number of oxides, the reduction in plate thickness, and the peeled area ratio were measured using the above test steel plates by the following methods.
- ⁇ Fatigue test> Using the test steel plate, a load non-transmission type cross welded joint was produced under the welding conditions shown in Table 4 and subjected to a fatigue test. In addition, the shape and dimension of a joint test body are shown in FIG. The joint was manufactured by fillet welding. In FIG. 1, 1 and 2 are base metal steel plates, and 5 is a welded portion. A repeated axial load was applied to each joint specimen, and the fatigue crack initiation life at the weld toe, that is, fatigue fracture life, was measured. Table 5 shows the fatigue test conditions.
- test pieces obtained from the obtained steel materials were evaluated by SAE (Society of Automotive Engineers) J2334 test.
- SAE J2334 test is wet: 50 ° C., 100% RH, 6 hours, salt adhesion: 0.5% NaCl, 0.1% CaCl 2 , 0.075% NaHCO 3 aqueous solution, 0.25 hour, dry: 60
- This test is a test that simulates a severe corrosive environment in which the amount of incoming salt exceeds 1 mdd.
- the “plate thickness reduction amount” is an average plate thickness reduction amount of the test piece, and is calculated using the weight reduction before and after the test and the surface area of the test piece.
- a test piece with a size of 150 x 70 mm was coated with a modified epoxy paint (Banno 200: made in China) by air spray to a dry film thickness of 150 ⁇ m, and the steel substrate After making a crosscut at a depth reaching, the SAE J2334 test was also evaluated.
- a modified epoxy paint Banno 200: made in China
- Table 6 shows the chemical composition and manufacturing method of the steel material and various test results.
- the number of oxides in a region within 2 mm from the surface layer is 5 ⁇ 10 4 pieces / mm 2 or less.
- the fatigue fracture life (number of repetitions) exceeded 5 ⁇ 10 6 times, and da / dn was 5 ⁇ 10 ⁇ 5 or less, so that it had sufficient fatigue crack propagation characteristics.
- the chemical composition satisfies the range defined by the present invention, but the production methods deviate from the conditions of the present invention, and Comparative Examples 1 and 2 and the chemical composition deviates from the range defined by the present invention. In each case, the fatigue rupture life was extremely poor at 10 4 units.
- Comparative Example 3 in which the Cu content was large and Cu / Sn exceeded 1, minute cracks occurred at the ends during rolling.
- Comparative Example 4 with a small amount of Sn the corrosion resistance in an environment with a large amount of incoming salt was lowered, and the peeled area ratio was 80%.
- the steel material of the present invention is excellent in fatigue crack growth resistance and corrosion resistance
- a welded structure that requires fatigue crack growth resistance such as a hull, civil engineering structure, construction machine, hydraulic iron pipe, offshore structure, line pipe, etc. Suitable for use with things.
- Base steel plate 2. 4. Base steel plate welded part
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Abstract
Description
Fe3++e-→Fe2+ (Fe3+の還元反応)
2H2O+O2+2e-→4OH-、
2H++2e-→H2
アノード反応:Fe→Fe2++2e- (Feの溶解反応)
2Fe3++Fe→3Fe2+・・・・・・(1)式
ただし、上記式中の各元素記号は、各元素の含有量(質量%)を意味する。なお、各元素の含有量が不純物レベルの場合には0(ゼロ)を代入するものとする。
工程A:溶鋼に下記(3)式を満足する条件で不活性ガスを吹き込む工程、
工程B:得られた溶鋼を連続鋳造し、上記(1)~(6)のいずれかの化学組成を有する鋼片を得る工程、
工程C:得られた鋼片を900~1180℃に加熱した後、仕上げ温度が650~1000℃となる条件で熱間圧延を施して熱延材を得る工程、および、
工程D:得られた熱延材を、620~950℃の温度域から、620~500℃の温度域における平均冷却速度が5~50℃/秒となる条件で加速冷却し、500℃以下の温度域で冷却を終了させる工程。
ただし、上記(3)式中の記号の定義は、下記のとおりである。
G1:溶鋼内に吹き込まれる不活性ガス流量(NL/min)
H1:不活性ガス吹き込みノズルの先端から溶鋼湯面までの距離(m)
t1:不活性ガス吹き込み時間(min)
S1:取鍋溶鋼量(ton)
D1:取鍋内径(m)
工程A1:溶鋼に下記(4)式を満足する条件で真空精錬処理を行う工程、
工程B:得られた溶鋼を連続鋳造し、上記(1)~(6)のいずれかの化学組成を有する鋼片を得る工程、
工程C:得られた鋼片を900~1180℃に加熱した後、仕上げ温度が650~1000℃となる条件で熱間圧延を施して熱延材を得る工程、および、
工程D:得られた熱延材を、620~950℃の温度域から、620~500℃の温度域における平均冷却速度が5~50℃/秒となる条件で加速冷却し、500℃以下の温度域で冷却を終了させる工程。
ただし、上記(4)式中の記号の定義は、下記のとおりである。
G2:溶鋼環流に使用される不活性ガス流量(NL/min)
D2:浸漬管内径(m)
t2:真空処理時間(min)
S2:取鍋溶鋼量(ton)
まず、本発明の鋼材の化学組成その他について説明する。以下の説明において、含有量についての「%」は、「質量%」を意味する。
Cは、強度を確保するために必要な元素である。その含有量が0.01%未満では必要とする強度を確保することができない。しかし、その含有量が0.14%を超えると、溶接した場合に溶接熱影響部(HAZ)、母材ともに靱性を確保することが難しくなる。したがって、Cの含有量は、0.01~0.14%とする。C含有量の好ましい下限は0.03%、好ましい上限は0.10%である。
Siは、脱酸作用があるとともに、鋼材の強度上昇にも寄与する。これらの効果を得るためには、Siを0.04%以上含有させる必要がある。しかし、その含有量が0.6%を超えると、靭性の低下をもたらす。したがって、Siの含有量は、0.04~0.6%とする。
Mnは、鋼の焼入性を高める効果があり、強度確保に有効な成分である。その含有量が0.5%未満では、焼入性が不足し、所望の強度および靱性が得られない。しかし、Mnは2.0%を超えて含有させると、偏析が増すとともに焼入性が高まりすぎて、溶接時に溶接熱影響部、母材ともに靱性が低下する。したがって、Mnの含有量は、0.5~2.0%とする。
Pは、不純物として鋼中に不可避的に存在する。その含有量が0.01%を超えると、粒界に偏析して靭性を低下させるのみならず、溶接時に高温割れを招く。したがって、Pの含有量は、0.01%以下に制限する必要がある。Pは少ないほど好ましい。
Sは、不純物として鋼中に不可避的に存在する。その含有量が多すぎると、中心偏析を助長したり、延伸したMnSが多量に生成したりして、母材および溶接熱影響部の機械的性質を劣化させる。したがって、Sの含有量は、0.003%以下に制限する必要がある。Sは少ないほど好ましい。
Cuは、一般的に耐候性を向上させる基本元素とされ、全ての海浜耐候性鋼や耐食鋼に添加されているが、高飛来塩分下の比較的ドライな環境においては、むしろ耐食性を低下させる。またSnと共存すると圧延時に割れが生じる。したがって、Cuの含有は少なくする必要がある。不純物として含有されるとしても、Cu含有量は0.2%未満とする必要がある。好ましくは0.1%未満である。
Bは、焼入性を向上させて強度を高める効果がある元素である。この効果を得るには、0.0007%を超えて含有させる必要がある。しかし、その含有量が0.005%を超えると、疲労特性が劣化する。したがって、Bの含有量は0.0007%を超え0.005%以下とする。
Alは、脱酸作用を有する元素である。しかし、その含有量が0.05%以上になると、主として溶接熱影響部において靱性が劣化しやすくなる。これは、粗大なクラスター状のアルミナ系介在物粒子が形成されやすくなるためと考えられる。したがって、Al含有量は、0.05%未満とする。ただし、脱酸作用があるSiにより脱酸を行う場合には、特に含有させなくてもよい。なお、Alによる脱酸作用を安定的に発揮させるためには、0.001%以上含有させることが好ましい。
Nは、不純物として鋼中に不可避的に存在する元素である。多量に存在する場合には、母材および溶接熱影響部の靭性の悪化原因となる。したがって、N含有量は、0.007%以下とする。Nは少ないほど好ましい。
O(酸素)は、不純物として鋼中に不可避的に存在する元素である。その含有量が0.003%を超えると、母材靭性及び伸び絞り等の延性に悪影響を及ぼす。したがって、O含有量は、0.003%以下に制限する。
Snは、Sn2+となって溶解し、酸性塩化物溶液中でのインヒビター作用により腐食を抑制する作用を有する。また、Fe3+を速やかに還元させ、酸化剤としてのFe3+濃度を低減する作用を有することにより、Fe3+の腐食促進作用を抑制するので、高飛来塩分環境における耐候性を向上させる。また、Snには鋼のアノード溶解反応を抑制し耐食性を向上させる作用がある。さらに、Snを含有することにより、飛来塩分が多い環境においてもCrの耐候性を向上させる効果が発揮される。これらの作用は、Snを0.03%以上含有させることにより得られ、0.50%を超えると飽和する。したがって、Snの含有量は0.03~0.50%とする。Snの含有量の望ましい範囲は0.03~0.20%である。
Snを含有する鋼の場合には、Cuの含有による耐食性の低下が著しい。また、鋼材を製造する際、Cuの含有による圧延割れの原因ともなる。このため、Cu/Sn比、すなわち、Sn含有量に対するCu含有量の比を1以下とする必要がある。
Mo:1.0%以下
Moは、母材の強度と靱性を向上させる効果があるため、必要に応じて含有させても良い。しかし、1.0%を超えて含有させると、主として溶接熱影響部の硬度が高まり、靱性および耐SSC性を損なう。したがって、Moを含有させる場合には、その含有量を1.0%以下とするのが好ましい。なお、この効果を安定的に得るためには、0.05%以上含有させるのが好ましい。
Vは、主に焼戻し時の炭窒化物析出により母材の強度を向上させる効果があるため、必要に応じて含有させても良い。しかし、0.1%を超えて含有させると、母材の性能向上効果が飽和し、靱性劣化を招く。したがって、Vを含有させる場合には、その含有量を0.1%以下にするのが好ましい。なお、この効果を安定的に得るためには、0.005%以上含有させるのが好ましい。
Nbは、細粒化と炭化物析出により母材の強度および靱性を向上させる効果があるため、必要に応じて含有させても良い。しかし、その含有量が0.1%を超えると、上記の効果が飽和する一方で、溶接熱影響部の靱性を著しく損なう。したがって、Nbを含有させる場合には、その含有量を0.1%以下とするのが好ましい。なお、この効果を安定的に得るためには、0.005%以上含有させるのが好ましい。
Ni:1.5%以下
Niは、固溶状態において鋼のマトリックス(生地)の靭性を高める効果があるため、必要に応じて含有させても良い。しかし、1.5%を超えて含有させても合金コストの上昇に見合った特性の向上が得られない。さらに、SnとNiの共存により耐食性が劣化する場合がある。したがって、Niを含有させる場合には、その含有量を1.5%以下とすることが好ましい。なお、この効果を安定的に得るためには、0.05%以上含有させるのが好ましい。
Cr:1.2%以下
Crは、耐炭酸ガス腐食性を高め、また焼入性を高める効果があるため、必要に応じて含有させても良い。しかし、1.2%を超えて含有させると、他の成分条件を満足させても、溶接熱影響部の硬化の抑制が難しくなるだけでなく、耐炭酸ガス腐食性向上効果も飽和する。したがって、Crを含有させる場合には、その含有量を1.2%以下とすることが好ましい。なお、この効果を安定的に得るためには、0.05%以上含有させるのが好ましい。
Ti:0.05%以下
Tiは、脱酸元素として作用するとともに、Ti、Mnからなる酸化物相を形成し、特に大入熱溶接の熱影響部における組織を微細化し、疲労特性向上の効果が得られるため、必要に応じて含有させても良い。しかし、0.05%を超えて含有させると、形成される酸化物がTi酸化物あるいはTi-Al酸化物となって分散密度が低下し、大入熱溶接部の熱影響部における組織を微細化する能力が失われる。このため、Tiを含有させる場合には、その含有量を0.05%以下とするのが好ましい。より好ましいのは0.02%未満である。さらに好ましくは0.018%以下である。なお、この酸化物相を安定的に鋼中に形成させるためには、鋼中のTiの総量を0.003%以上とするのが好ましい。
Ca:0.003%以下
Caは、鋼中のSと反応して溶鋼中で酸硫化物(オキシサルファイド)を形成する。この酸硫化物は、MnSなどと異なり、圧延加工で圧延方向に伸びることがなく圧延後も球状であるため、延伸した介在物の先端などを割れの起点とする溶接割れや水素誘起割れを抑制する作用がある。したがって、必要に応じて含有させても良い。しかし、その含有量が0.003%を超えると、靱性の劣化を招くことがある。したがって、Caを含有させる場合には、その含有量を0.003%以下とするのが好ましい。なお、この効果を安定的に得るためには、0.0005%以上含有させるのが好ましい。
Mgは、Mg含有酸化物を生成し、TiNの発生核となり、TiNを微細分散させる効果を持つため、必要に応じて含有させても良い。しかし、その含有量が0.003%を超えると、酸化物が多くなりすぎて延性低下をもたらす。したがって、Mgを含有させる場合には、その含有量を0.003%以下とするのが好ましい。なお、この効果を安定的に得るためには、0.0005%以上含有させるのが好ましい。
ただし、上記式中の各元素記号は、各元素の含有量(質量%)を意味する。なお、各元素の含有量が不純物レベルの場合には0(ゼロ)を代入するものとする。
Bによる焼入性向上効果を発揮させるには、鋼中のNの影響をなくす必要がある。Bは、Nと結合し易く、鋼中にフリーなNが存在すると、Nと結合してBNが生成しやすいからである。このため、N含有量に応じてTiを添加し、TiNとして固定することにより、Bを鋼中に存在させる。B含有量が大きくなればなるほど、Bによる焼入性が向上する。しかし、(1)式から求められるBq値が0.003を超えると、粗大な鉄炭硼化物が形成され、疲労特性の劣化に繋がる。したがって、Bq値は、0.003以下にする必要がある。
上記(2)式から求められるCeqは、いわゆる炭素当量であり、鋼材の焼入性や溶接性を評価する指標であり、一般に広く使われている。
本発明の耐疲労亀裂進展特性および耐食性に優れた鋼材を製造するにあたっては、精錬段階から調整をするのが好ましい。すなわち、精錬段階では、不活性ガス吹き込み処理または真空精錬処理を工夫することにより、表層部の酸化物を低減できる。具体的には、不活性ガス吹き込み処理を行うに当たっては、溶鋼に下記(3)式を満足する条件で不活性ガスを吹き込むのが有効である。
ただし、上記(3)式中の記号の定義は、下記のとおりである。
G1:溶鋼内に吹き込まれる不活性ガス流量(NL/min)
H1:不活性ガス吹き込みノズルの先端から溶鋼湯面までの距離(m)
t1:不活性ガス吹き込み時間(min)
S1:取鍋溶鋼量(ton)
D1:取鍋内径(m)
ただし、上記(4)式中の記号の定義は、下記のとおりである。
G2:溶鋼環流に使用される不活性ガス流量(NL/min)
D2:浸漬管内径(m)
t2:真空処理時間(min)
S2:取鍋溶鋼量(ton)
上記の試験用鋼板を用いて、表4に示す溶接条件で、荷重非伝達型の十字溶接継手を作製し、疲労試験に供した。なお、継手試験体の形状と寸法を図1に示す。継手は隅肉溶接で製作した。図1において、1と2が母材鋼板、5が溶接部である。各継手試験体に対し、繰返し軸力負荷を与え、溶接余盛り止端における疲労亀裂の発生寿命、つまり疲労破断寿命を測定した。表5に疲労試験条件を示す。
上記の試験用鋼板において、圧延面に平行で、かつ圧延方向に垂直な方向に試験片を採取し、JIS Z 2241(1998)に規定される方法に従って、引張試験を実施し、引張強さ(TS)を求めた。
上記の試験用鋼板(板厚(t))から、鋼板表面から(1/4)t厚部において、圧延面に平行で、圧延方向に垂直な方向に試験片を採取し、JIS Z 2242(1998)に規定される方法に従って、衝撃試験を実施し、0℃における吸収エネルギー(vE0)を求めた。
下記(i)~(iii)に示す手順により表層から2mm以内の領域における酸化物数を求めた。
耐食性に関しては、得られた鋼材から得た試験片をSAE(Society of Automotive Engineers)J2334試験により評価した。SAE J2334試験は、湿潤:50℃、100%RH、6時間、塩分付着:0.5%NaCl、0.1%CaCl2、0.075%NaHCO3水溶液浸漬、0.25時間、乾燥:60℃、50%RH、17.75時間を1サイクル(合計24時間)とした加速試験であり、腐食形態が大気暴露試験に類似しているとされている(長野博夫、山下正人、内田仁著:環境材料学、共立出版(2004)、p.74)。なお、本試験は、飛来塩分量が1mddを超えるような厳しい腐食環境を模擬する試験である。
2.母材鋼板
5.溶接部
Claims (8)
- 質量%で、C:0.01~0.14%、Si:0.04~0.6%、Mn:0.5~2.0%、P:0.01%以下、S:0.003%以下、Cu:0.2%未満、B:0.0007%を超え0.005%以下、Al:0.05%未満、N:0.007%以下、O:0.003%およびSn:0.03~0.50%以下を含有し、残部はFeおよび不純物からなり、かつ、Cu/Sn比が1以下である化学組成を有し、そして、下記(1)式から求められるBq値が0.003以下、下記(2)式から求められるCeq値が0.15~0.35であり、かつ、表層から2mm以内の領域における酸化物数が1平方mmあたり5×104個以下であることを特徴とする耐疲労亀裂進展特性および耐食性に優れた鋼材。
ただし、上記式中の各元素記号は、各元素の含有量(質量%)を意味する。なお、各元素の含有量が不純物レベルの場合には0を代入するものとする。 - さらに、質量%で、Mo:1.0%以下、V:0.1%以下およびNb:0.1%以下から選択される1種以上の元素を含有することを特徴とする請求項1に記載の耐疲労亀裂進展特性および耐食性に優れた鋼材。
- さらに、質量%で、Ni:1.5%以下を含有することを特徴とする請求項1または2に記載の耐疲労亀裂進展特性および耐食性に優れた鋼材。
- さらに、質量%で、Cr:1.2%以下を含有することを特徴とする請求項1から3までのいずれかに記載の耐疲労亀裂進展特性および耐食性に優れた鋼材。
- さらに、質量%で、Ti:0.05%以下を含有することを特徴とする請求項1から4までのいずれかに記載の耐疲労亀裂進展特性および耐食性に優れた鋼材。
- さらに、質量%で、Ca:0.003%以下およびMg:0.003%以下の一方または両方を含有することを特徴とする請求項1から5までのいずれかに記載の耐疲労亀裂進展特性および耐食性に優れた鋼材。
- 下記の工程A~Dを備え、かつ、工程Dの冷却終了後の復熱温度幅を70℃以下とすることを特徴とする耐疲労亀裂進展特性および耐食性に優れた鋼材の製造方法。
工程A:溶鋼に下記(3)式を満足する条件で不活性ガスを吹き込む工程、
工程B:得られた溶鋼を連続鋳造し、請求項1から6までのいずれかに記載の化学組成を有する鋼片を得る工程、
工程C:得られた鋼片を900~1180℃に加熱した後、仕上げ温度が650~1000℃となる条件で熱間圧延を施して熱延材を得る工程、および、
工程D:得られた熱延材を、620~950℃の温度域から、620~500℃の温度域における平均冷却速度が5~50℃/秒となる条件で加速冷却し、500℃以下の温度域で冷却を終了させる工程。
ただし、上記(3)式中の記号の定義は、下記のとおりである。
G1:溶鋼内に吹き込まれる不活性ガス流量(NL/min)
H1:不活性ガス吹き込みノズルの先端から溶鋼湯面までの距離(m)
t1:不活性ガス吹き込み時間(min)
S1:取鍋溶鋼量(ton)
D1:取鍋内径(m) - 下記の工程A1~Dを備え、かつ、工程Dの冷却終了後の復熱温度幅が70℃以下であることを特徴とする耐疲労亀裂進展特性および耐食性に優れた鋼材の製造方法。
工程A1:溶鋼に下記(4)式を満足する条件で真空精錬処理を行う工程、
工程B:得られた溶鋼を連続鋳造し、請求項1から6までのいずれかに記載の化学組成を有する鋼片を得る工程、
工程C:得られた鋼片を900~1180℃に加熱した後、仕上げ温度が650~1000℃となる条件で熱間圧延を施して熱延材を得る工程、および、
工程D:得られた熱延材を、620~950℃の温度域から、620~500℃の温度域における平均冷却速度が5~50℃/秒となる条件で加速冷却し、500℃以下の温度域で冷却を終了させる工程。
ただし、上記(4)式中の記号の定義は、下記のとおりである。
G2:溶鋼環流に使用される不活性ガス流量(NL/min)
D2:浸漬管内径(m)
t2:真空処理時間(min)
S2:取鍋溶鋼量(ton)
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Cited By (6)
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JP2013044020A (ja) * | 2011-08-24 | 2013-03-04 | Jfe Steel Corp | 船舶バラストタンク用耐食鋼材 |
WO2016092756A1 (ja) * | 2014-12-09 | 2016-06-16 | Jfeスチール株式会社 | 耐候性に優れた構造用鋼材 |
JP5999196B2 (ja) * | 2012-12-05 | 2016-09-28 | Jfeスチール株式会社 | 耐アルコール孔食性および耐アルコールscc性に優れた鋼材 |
JP6394839B1 (ja) * | 2017-12-14 | 2018-09-26 | 新日鐵住金株式会社 | 鋼材 |
CN115572893A (zh) * | 2022-09-02 | 2023-01-06 | 武汉钢铁有限公司 | 一种耐大气腐蚀的高强度汽车轮辐用钢及其制造方法 |
US12000028B2 (en) * | 2015-08-24 | 2024-06-04 | Nippon Steel Corporation | Rail vehicle axle |
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WO2014104424A1 (ko) | 2012-12-24 | 2014-07-03 | 주식회사 포스코 | 내응축수 부식특성, 성형성 및 고온 내산화 특성이 우수한 자동차 배기계용 페라이트계 스테인리스강 및 그 제조방법 |
WO2019146749A1 (ja) * | 2018-01-26 | 2019-08-01 | 日本製鉄株式会社 | 係留チェーン用鋼および係留チェーン |
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