WO2018011862A1 - 耐応力腐食割れ性に優れたボイラー用電縫鋼管及びその製造方法 - Google Patents
耐応力腐食割れ性に優れたボイラー用電縫鋼管及びその製造方法 Download PDFInfo
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- WO2018011862A1 WO2018011862A1 PCT/JP2016/070453 JP2016070453W WO2018011862A1 WO 2018011862 A1 WO2018011862 A1 WO 2018011862A1 JP 2016070453 W JP2016070453 W JP 2016070453W WO 2018011862 A1 WO2018011862 A1 WO 2018011862A1
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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
- 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
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
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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
-
- 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
- C22C38/02—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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
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- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
Definitions
- the present invention relates to an electric-welded steel pipe for boilers having excellent stress corrosion cracking resistance on the outer surface of the steel pipe. Moreover, this invention relates to the manufacturing method of such an electric-resistance-welded steel pipe.
- Boiler piping made of carbon steel heat transfer tubes may be used in nitrate environments. For this reason, such boiler piping may be damaged due to stress corrosion cracking caused by ammonium nitrate. Therefore, the boiler piping is required to have stress corrosion cracking resistance (hereinafter sometimes referred to as “SCC resistance”).
- SCC resistance stress corrosion cracking resistance
- Boiler piping damage is caused by ammonium nitrate, which is generated when NO 2 or NH 3 in the exhaust gas dissolves in the condensed condensed water on the piping when starting up the plant, and tensile residual stress due to bending or fin winding welding. It is a phenomenon that these causes occur in synergy.
- Patent Document 1 discloses a method for evaluating and diagnosing SCC damage due to nitrate in a carbon steel heat transfer tube of a waste heat recovery boiler with high accuracy. Specifically, the number of start / stop times in each mode of the plant and each The wet time in each mode and the concentration of nitrogen oxides in the exhaust gas in each mode are calculated, the concentration of accumulated nitrate during the entire wet time is calculated, and the calculated concentration of accumulated nitrate is determined by stress corrosion cracking. A nitrate stress corrosion cracking diagnosis method is disclosed that evaluates the degree of damage by calculating the operating period until a possible generation limit nitrate concentration is reached.
- Patent Document 2 discloses a high-strength boiler electric resistance steel pipe excellent in high-temperature characteristics and corrosion resistance.
- the component composition is C: 0.15 to 0.30% by weight%, Si: 0.05-0.50%, Mn: 0.25-1.5%, N: 0.005-0.010%, Cu: 0.02-0.10%, Ca: 0.001-0. 004%, Mo: 0.01-0.10%, S: 0.003% or less as basic components, remaining Fe and unavoidable elements.
- a boiler ERW steel pipe having a uniform structure is disclosed.
- Patent Document 3 discloses a steel material having excellent resistance to nitric acid stress corrosion cracking, and specifically, C: 0.005 to 0.05%, Si: 0.1 to 0.00 by weight%. 8%, Mn: 0.2 to 1.5%, P: 0.015% or less, S: 0.015% or less, Cr: 3.5 to 5.0%, Mo: 0.2 to 1.2 %, Nb: 0.01 to 0.15%, Al: 0.01 to 0.20%, N: 0.015% or less, with the remainder consisting of Fe containing unavoidable components for resistance to nitric acid stress corrosion cracking Excellent steel materials are disclosed.
- the above-described damage to the boiler piping is caused by cracks extending along the ferrite grain boundary of the welded part when used in a nitrate environment. This damage occurs in the weld due to the lower carbon concentration in the weld compared to the base metal, and the ferrite grain boundary strength is such that the weld can withstand use in a nitrate environment. This is because it is not sufficiently obtained.
- the present invention has been made in view of the above circumstances, and provides an electric resistance welded steel pipe for a boiler that has excellent stress corrosion cracking resistance by increasing the ferrite grain boundary strength of the weld and suppressing cracks in the weld. And providing a method for manufacturing the ERW steel pipe.
- the inventors of the present invention can increase the ferrite grain boundary strength of the welded portion, suppress cracking at the welded portion, and thus exhibit excellent stress corrosion cracking resistance (SCC resistance).
- SCC resistance stress corrosion cracking resistance
- the inventors of the present invention can increase the carbon concentration of the weld abutting portion and improve the ferrite grain boundary strength of the weld abutting portion by performing a predetermined heat treatment after the electric resistance welding, and thus improve the SCC resistance. The knowledge that it can be made was acquired.
- the present inventors evaluated the hardness difference between different depth positions from the surface of the base material part and the hardness of the weld contact part for the presence or absence of decarburization affecting the ferrite grain boundary strength.
- a method of evaluating the difference between the hardness of the base metal part (Evaluation Method 1), or evaluating the pearlite area ratio of the weld interface, and the pearlite area ratio of the weld interface and the pearlite area ratio of the base material part
- evaluation method 2 A method of evaluating the difference between the hardness of the base metal part (Evaluation Method 1), or evaluating the pearlite area ratio of the weld interface, and the pearlite area ratio of the weld interface and the pearlite area ratio of the base material part.
- the present invention has been made based on the above findings, and the gist thereof is as follows.
- Ingredient composition is mass%, C: 0.05 to 0.35%, Si: 0.10 to 0.35%, Mn: 0.25 to 1.50%, S: 0.035% or less, P: 0.035% or less, Al: 0.005 to 0.050%, N: 0.010% or less, and O: 0.010% or less, Further optionally, Cr: 1.00% or less, Mo: 1.00% or less, Ni: 2.00% or less, Cu: 2.00% or less, B: 0.0030% or less, Nb: 0.0.
- Ingredient composition is mass%, C: 0.05 to 0.35%, Si: 0.10 to 0.35%, Mn: 0.25 to 1.50%, S: 0.035% or less, P: 0.035% or less, Al: 0.005 to 0.050%, N: 0.010% or less, and O: 0.010% or less, Further optionally, Cr: 1.00% or less, Mo: 1.00% or less, Ni: 2.00% or less, Cu: 2.00% or less, B: 0.0030% or less, Nb: 0.0.
- [5] A method for producing an electric-welded steel pipe for boilers having excellent stress corrosion cracking resistance according to any one of [1] to [4], A step (i) of forming a steel material having the composition described in [1] or [2] into a pipe; And a step (ii) of subjecting the tube to a heat treatment for 30 seconds or more at a temperature of not less than Ac3 and not more than 1250 ° C. in an atmosphere furnace. Manufacturing method of sewn steel pipe.
- the hardness difference between different depth positions from the surface of the base material part is set to a predetermined range, and the welding abutting part
- the difference between the hardness and the hardness of the base material portion is set within a predetermined range.
- the pearlite area ratio of the welding contact portion is set within a predetermined range after setting a specific component composition.
- the method for manufacturing an electric resistance welded steel pipe for boiler according to the present invention uses a predetermined atmosphere furnace and sets a holding temperature and a holding time in a predetermined range in the heat treatment. Yes. Therefore, according to the technology related to the electric-welded steel pipe for boilers according to the present invention, the ferrite grain boundary strength is increased by increasing the carbon concentration of the weld abutting portion, cracking at the welded portion is suppressed, and excellent stress corrosion resistance is achieved. An electric resistance welded steel pipe for boiler having cracking properties can be obtained.
- FIG. 1 is a schematic view showing a portion of a steel pipe targeted in the investigation of a crack occurrence portion
- (a) is a cross-sectional view showing a weld abutting portion in the steel pipe
- (b) is a drawing of (a). It is an enlarged view of a circled part.
- FIG. 2 is a cross-sectional photograph of a welded contact portion of an ERW steel pipe, where (a) is an example in which no cracking occurred and (b) is an example in which cracking has occurred.
- Fig. 3 is a graph showing the relationship between the hardness of the ERW steel pipe for boiler and the distance from the weld surface.
- FIG. 4A shows a steel pipe where stress corrosion cracking has not occurred
- FIG. 4B shows stress corrosion cracking.
- the steel pipe which is doing is shown.
- 4A and 4B are schematic views showing the carbon concentration at the weld abutting portion of the pipe.
- FIG. 4A shows a state before the heat treatment
- FIG. 4B shows a state after the heat treatment.
- the present electric resistance steel pipe for boilers which is excellent in the stress corrosion cracking resistance according to the present invention
- the manufacturing method thereof hereinafter sometimes referred to as “the present application manufacturing method”.
- the constituent elements of the above embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same.
- various forms included in the above-described embodiments can be arbitrarily combined within a range obvious to those skilled in the art.
- the ERW steel pipe of the present application contains C, Si, Mn, S, P, Al, N, and O, and Fe and unavoidable impurities in the following ranges.
- C 0.05 to 0.35%
- C is an element necessary for ensuring the strength of the steel pipe. If it is less than 0.05%, the strength of the steel pipe is insufficient, so C is made 0.05% or more. Preferably it is 0.06% or more. On the other hand, if it exceeds 0.35%, the hardness of the steel pipe increases and the workability deteriorates, so C is made 0.35% or less. Preferably it is 0.32% or less.
- Si 0.10 to 0.35%
- Si is an element that contributes to improving the strength of the steel pipe by solid solution strengthening. If it is less than 0.10%, the effect of addition is not sufficiently exhibited, so Si is made 0.10% or more. Preferably it is 0.15% or more. On the other hand, if it exceeds 0.35%, the strength of the steel pipe will increase too much and the workability will deteriorate, so Si is made 0.35% or less. Preferably it is 0.30% or less.
- Mn 0.25 to 1.50%
- Mn is an element that ensures hardenability and contributes to improving the strength of the steel pipe. If it is less than 0.25%, the effect of addition is not sufficiently exhibited, so Mn is made 0.25% or more. Preferably it is 0.27% or more. On the other hand, if it exceeds 1.50%, the hardness of the steel pipe increases so much that the workability deteriorates, so Mn is made 1.50% or less. Preferably it is 1.45% or less.
- S 0.035% or less
- S is an element that forms MnS that is a starting point of cracking. For this reason, it is preferable that S is as small as possible. Preferably it is 0.030% or less.
- the lower limit includes 0%, but if it is attempted to reduce S to less than 0.0001%, the manufacturing cost increases significantly, so practically 0.0001% is the practical lower limit.
- P 0.035% or less
- P is an element that causes grain boundary segregation or center segregation which causes ductile deterioration. For this reason, it is preferable that P is as small as possible. Preferably it is 0.030% or less.
- the lower limit includes 0%, but if P is reduced to less than 0.0010%, the manufacturing cost increases significantly. Therefore, in practice, 0.0010% is the practical lower limit.
- Al 0.005 to 0.050%
- Al is a deoxidizing element. If it is less than 0.005%, deoxidation becomes insufficient, so Al is made 0.005% or more. Preferably it is 0.010% or more. On the other hand, if it exceeds 0.050%, the workability deteriorates due to the coarsening of the alumina-based oxide, so Al is made 0.050% or less. Preferably it is 0.040% or less.
- N 0.010% or less
- N is an unavoidable element. If it exceeds 0.010%, inclusions become coarse and workability deteriorates, so N is made 0.010% or less. Preferably it is 0.008% or less.
- the lower limit includes 0%, but if N is reduced to less than 0.0010%, the manufacturing cost increases significantly, so practically 0.0010% is the practical lower limit.
- O 0.010% or less
- O is an element unavoidably present after deoxidation. If it exceeds 0.010%, inclusions become coarse and workability deteriorates, so O is made 0.010% or less. Preferably it is 0.005% or less.
- the lower limit includes 0%, but if O is reduced to less than 0.0005%, the manufacturing cost is significantly increased, so practically 0.0005% is the practical lower limit.
- the balance Fe and inevitable impurities
- the balance is Fe and inevitable impurities.
- the inevitable impure part is not an impurity that is intentionally mixed, but also an impurity contained in a raw material or an impurity that can be mixed in each manufacturing process.
- Examples of inevitable impurities in the ERW steel pipe of the present application include As, Na, Zr, and Sb.
- the content (upper limit value) of these inevitable impurities is particularly limited as follows.
- the contents of As are 0.01% or less, Na is 0.01% or less, Zr is 0.01% or less, and Sb is 0.01% or less.
- the present electric resistance welded steel pipe is at least one of Cr, Mo, Ni, Cu, B, Nb, V, Ti, and Mg, as long as the characteristics of the present electric resistance welded steel pipe are not impaired. You may contain in each range shown.
- Cr 0.05-1.00% Cr is an element that ensures hardenability and contributes to improving the strength of the steel pipe. If it is less than 0.05%, the effect of addition is not sufficiently exhibited, so Cr is preferably made 0.05% or more. More preferably, it is 0.10% or more. On the other hand, if it exceeds 1.00%, the hardness of the steel pipe will increase too much and the workability will deteriorate, so Cr is preferably made 1.00% or less. More preferably, it is 0.80% or less.
- Mo 0.05-1.00%
- Mo is an element that ensures hardenability and contributes to improving the strength of the steel pipe. If it is less than 0.05%, the effect of addition is not sufficiently exhibited, so Mo is preferably made 0.05% or more. More preferably, it is 0.10% or more. On the other hand, if it exceeds 1.00%, the hardness of the steel pipe will increase excessively and the workability will deteriorate, so Mo is preferably made 1.00% or less. More preferably, it is 0.80% or less.
- Ni 0.10 to 2.00%
- Ni is an element that ensures hardenability and contributes to improving the strength of the steel pipe. If it is less than 0.10%, the effect of addition is not sufficiently exhibited, so Ni is preferably made 0.10% or more. More preferably, it is 0.15% or more. On the other hand, since the hardness of the steel pipe exceeding 2.00% increases excessively and the workability deteriorates, Ni is preferably made 2.00% or less. More preferably, it is 1.50% or less.
- Cu 0.10 to 2.00%
- Cu is an element that ensures hardenability and contributes to improving the strength of the steel pipe. If it is less than 0.10%, the effect of addition is not sufficiently exhibited, so Cu is preferably made 0.10% or more. More preferably, it is 0.15% or more. On the other hand, if it exceeds 2.00%, the hardness of the steel pipe will increase too much and the workability will deteriorate, so Cu is preferably made 2.00% or less. More preferably, it is 1.50% or less.
- B 0.0003 to 0.0030%
- B is an element that ensures hardenability and contributes to improving the strength of the steel pipe. If it is less than 0.0003%, the effect of addition is not sufficiently exhibited, so B is preferably made 0.0003% or more. More preferably, it is 0.0005% or more. On the other hand, if it exceeds 0.0030%, grain boundary embrittlement may be caused, so B is preferably made 0.0030% or less. More preferably, it is 0.0020% or less.
- Nb 0.005 to 0.20%
- Nb is an element that has a strong affinity between C and N, precipitates NbCN, and contributes to improving the strength of the steel pipe. If it is less than 0.005%, the effect of addition is not sufficiently exhibited, so Nb is preferably 0.005% or more. More preferably, it is 0.010% or more. On the other hand, if it exceeds 0.20%, precipitation hardening by NbC becomes remarkable and workability deteriorates, so Nb is preferably 0.20% or less. More preferably, it is 0.10% or less.
- V 0.005 to 0.20%
- V is an element that has a strong affinity between C and N, precipitates VN and VC, and contributes to improving the strength of the steel pipe. If it is less than 0.005%, the effect of addition is not sufficiently exhibited, so V is preferably set to 0.005% or more. More preferably, it is 0.010% or more. On the other hand, if it exceeds 0.20%, precipitation hardening due to VN or VC becomes remarkable and workability deteriorates. Therefore, V is preferably 0.20% or less. More preferably, it is 0.10% or less.
- Ti 0.005 to 0.20%
- Ti is an element that has a strong affinity for N and precipitates TiN to contribute to the refinement of the structure. If it is less than 0.005%, the effect of addition is not sufficiently exhibited, so Ti is preferably made 0.005% or more. More preferably, it is 0.008% or more. On the other hand, if it exceeds 0.20%, precipitation hardening by TiC becomes remarkable and workability deteriorates, so Ti is preferably 0.20% or less. More preferably, it is 0.10% or less.
- Ca 0.0001 to 0.0050% Ca is an element that adjusts the form of inclusions in the base material and the ERW weld and contributes to improvement in workability. If it is less than 0.0001%, the effect of addition is not sufficiently exhibited, so Ca is preferably made 0.0001% or more. More preferably, it is 0.0005% or more. On the other hand, if it exceeds 0.0050%, the inclusions in the steel increase and the workability deteriorates, so Ca is preferably 0.0050% or less. More preferably, it is 0.0040% or less.
- Mg 0.0050% or less
- Mg is a deoxidizing element, and the generated oxide functions as a precipitation nucleus of MnS. Therefore, Mg is an element contributing to miniaturization and uniform dispersion of MnS. If it exceeds 0.0050%, the yield decreases and the effect of addition is saturated. Therefore, Mg is preferably 0.0050% or less. More preferably, it is 0.0040% or less.
- the welding abutting portion is a portion in the vicinity of the welding surface, and a portion whose distance from the welding surface is a distance of 0 ⁇ m to about 100 ⁇ m among the portions where the microstructure is thermally affected by the electric resistance welding.
- the base material portion is a portion that is further away from the welding surface than the welding abutting portion, and means a portion in which the microstructure is not affected by heat due to the electric resistance welding.
- the inventors of the present invention have stress corrosion cracking (SCC) in a nitrate environment. Welds were photographed for steel pipes where no SCC occurred and steel pipes where SCC occurred in a nitrate environment, and the cracked portions of the steel pipe where SCC occurred were investigated.
- SCC stress corrosion cracking
- FIG. 1 is a schematic diagram showing a portion of a steel pipe targeted in the investigation of a crack occurrence portion, and is a diagram drawn by increasing the horizontal scale relative to the vertical scale.
- Fig.1 (a) has shown a part of cross-sectional area
- FIG.1 (b) is an enlarged view of the encircled part X of Fig.1 (a). It is.
- FIG.1 (b) it is an area
- the weld abutting portion can be defined by specifying the positions of 100 ⁇ m on both sides of the weld surface by making indentations after specifying the weld surface by performing metal flow etching.
- FIG. 2 is a cross-sectional photograph of a welded contact portion of an ERW steel pipe, where (a) is an example in which no cracking occurred, and (b) is an example in which cracking has occurred.
- the crack propagated from the outer surface to the deep part at the weld abutting portion of the steel pipe, and specifically, occurred in a region from the outer surface to a depth of 1 mm.
- the hardness of the weld abutting portion at a specific depth position is measured by measuring the Vickers hardness (Hv) at a depth position of 0.5 mm from the outer surface of the steel pipe in a range of 0.6 mm on both sides across the weld surface. did. This hardness is measured at a test load of 100 g at each position of 0.1 mm pitch in an arc shape around the weld surface.
- the hardness of the member portion at the specific depth position is Vickers hardness (Hv) at a depth position of 0.5 mm from the outer surface of the steel pipe, and both sides of the position rotated 90 ° around the steel pipe center from the weld surface. Measurements were made in the range of 0.6 mm.
- FIG. 3 is a graph showing the results of item (1-2) above. That is, FIG. 3 is a graph showing the relationship between the hardness of the ERW steel pipe for boiler (Vickers hardness at a depth of 0.5 mm from the outer surface of the steel pipe) and the distance from the weld surface. The steel pipe which has not generate
- a positive (negative) number on the horizontal axis means that the welding surface is separated from the welding surface by a predetermined distance.
- each figure shown in figure shows the result about two examples from which the measurement position differs although it is the same steel pipe.
- the hardness when the distance from the weld surface is “0 (mm)” is the hardness of the weld abutting portion, and the distance from the weld surface is “ ⁇ 0.1, ⁇ 0. .2, ⁇ 0.3, ⁇ 0.4, ⁇ 0.5, ⁇ 0.6 (mm) ”is the hardness of the base material portion.
- the depth difference in hardness in the base material portion and the weld abutting portion at the specific depth position By setting the hardness difference from the base metal part within a predetermined range, the carbon concentration of the welded part (more specifically, the weld abutting part) is increased to increase the ferrite grain boundary strength, and cracks at the welded part are prevented. It is possible to suppress and realize excellent stress corrosion cracking resistance.
- the pearlite area ratio of the weld contact area is determined by performing metal flow etching to identify the weld surface, demarcating the weld contact area, further performing nital etching, and analyzing the structure of the weld contact area with an optical microscope ( (Magnification 200 times) was taken continuously, and the photographed image was derived by image analysis.
- the pearlite area ratio of the weld abutting portion from the outer surface to 1 mm is 5% or more, Then, it was confirmed that stress corrosion cracking (SCC) does not occur.
- the item (2) is an effect that carbon is diffused by a heat treatment to be described later, and the carbon concentration of the weld contact portion is increased.
- the pearlite area ratio of the weld abutting portion from the outer surface to 1 mm is set within a predetermined range.
- the ferrite grain boundary strength of the welded portion (more specifically, the weld abutting portion) can be increased, and cracking at the welded portion can be suppressed to achieve excellent stress corrosion cracking resistance.
- the pearlite area ratio is 8% or more, it is preferable in that it can be said to be an excellent electric-welded steel pipe for boilers.
- the upper limit of the pearlite area ratio is not particularly limited because it is determined by the amount of carbon.
- the residual stress in the surface layer portion of the weld contact portion was measured by measuring the stress on the outer surface of the steel pipe using X-ray diffraction (irradiation diameter: 0.5 mm), and this value was adopted.
- the residual stress on the outer surface of the steel pipe is uniform in the circumferential direction including the welded portion.
- the surface layer of the weld interface is not used in steel pipes where no SCC has occurred.
- the residual stress in the surface layer portion of the weld contact portion was over 200 MPa.
- Such low residual stress is realized because the residual stress generated when the heat-treated tube is bent and straightened is sufficiently reduced by the subsequent final heat treatment, as will be described later. Thereby, even if the hardness difference between the weld contact portion and the base material portion exceeds 20 Hv, the occurrence of SCC can be prevented if the residual stress of the surface layer portion of the weld contact portion is within an appropriate range. .
- the dendrite area ratio of the weld contact portion from the outer surface to 1 mm is 1% or less. The reason will be described below.
- the ERW steel pipe is a steel pipe formed through ERW welding.
- dendride does not exist in the welding contact portion in an area ratio exceeding 1% in the first place. Therefore, the steel pipe of the present embodiment obtained by electric resistance welding has an advantage that the productivity is extremely high as compared with a steel pipe formed through beam welding or the like.
- the dendrite area ratio is continuously photographed using an optical microscope (200 magnifications) of the structure of the weld abutting portion in a depth region from the outer surface of the steel pipe to 1 mm in the same manner as the method for deriving the pearlite area ratio.
- the captured image can be derived by image analysis.
- the manufacturing method of the present application includes at least a process using a steel material as a pipe (process (i)) and a heat treatment process of the pipe (process (ii)).
- the production method of the present application optionally includes a step (step (iii)) of correcting the bending of the tube and then subjecting the tube to a final heat treatment.
- This step is an essential step and is a step of forming a steel material (hot rolled coil) having a predetermined component composition into a tube.
- the predetermined component composition is the above-described component composition.
- the apparatus for forming a pipe is a commonly used apparatus, for example, ⁇ Forming equipment (equipment with a plurality of roll pairs that press steel from its up-down direction or left-right direction to form an open tube in sequence), ⁇ Welding machine (equipment for welding the ends of open pipes), ⁇ Cutting equipment (equipment that removes weld beads), ⁇ Cooling equipment (equipment for cooling pipes), -Stylization equipment (equipment for shaping welded pipes), ⁇ Non-destructive inspection equipment (equipment for non-destructive inspection of standardized pipes), and traveling cutting equipment (equipment for cutting pipes after non-destructive inspection to a predetermined length) Can be used.
- ⁇ Forming equipment equipment with a plurality of roll pairs that press steel from its up-down direction or left-right direction to form an open tube in sequence
- ⁇ Welding machine equipment for welding the ends of open pipes
- ⁇ Cutting equipment equipment that removes weld beads
- Cooling equipment equipment for cooling pipes
- This step is an essential step and is a step in which heat treatment is performed on the above-described tube after traveling cutting. Since ERW steel pipes for boilers may crack at welds with low carbon concentration when used in nitrate environments, etc., this process is effective in converting the base material carbon to the weld contact area in a short time. This is a process for increasing the stress corrosion cracking resistance by suppressing the generation of SCC by increasing the ferrite grain boundary strength of the weld abutting portion. Specifically, the tube is subjected to a heat treatment (hereinafter sometimes simply referred to as “main heat treatment”) for 30 seconds or more at a temperature of Ac3 or higher and 1250 ° C. or lower in an atmosphere furnace. In addition, after this heat processing, the electric-resistance-welded steel pipe for boilers as a final product is obtained through standing to cool.
- main heat treatment hereinafter sometimes simply referred to as “main heat treatment”
- FIG. 4 is a schematic diagram showing the carbon concentration at the weld abutting portion of the pipe, where (a) shows the state before the heat treatment, and (b) shows the state after the heat treatment.
- carbon diffuses in the weld abutting portion, and as a result, the ferrite grain boundary strength of the weld abutting portion is increased and the occurrence of SCC is suppressed, and as a result, the stress corrosion cracking resistance. Can be increased.
- the heat treatment temperature in this step is less than Ac3 point, the structure is not homogenized, and carbon diffusion to the weld interface becomes insufficient, so the heat treatment temperature is set to Ac3 point or higher.
- the heat treatment temperature is preferably (Ac3 point + 10) ° C. or higher.
- the heat treatment temperature in this step exceeds 1250 ° C., it will adversely affect the weld abutting part due to the generation of scale during welding and excessive decarburization at the welding abutting part.
- the temperature is 1250 ° C. or lower.
- the heat treatment temperature is preferably set to 1150 ° C. or lower.
- the holding time in this heat treatment is 30 seconds or more.
- the holding time refers to the time that has passed since the furnace temperature reached (target temperature ⁇ 20 ° C.).
- target temperature ⁇ 20 ° C. target temperature ⁇ 20 ° C.
- the atmosphere in the atmosphere furnace may be an atmosphere composed of at least one of argon, nitrogen, carbon dioxide, and hydrogen.
- oxygen is inevitably mixed.
- the present inventors have an item (1) (limitation on hardness) or item (2) (limitation on pearlite area ratio) if the amount of oxygen is unavoidably mixed (oxygen concentration is about 1%). It was experimentally confirmed that the above-mentioned predetermined range was obtained, and that the heat treatment effect was not hindered. For this reason, it is preferable that the oxygen concentration in the atmospheric furnace in this step is 1% or less.
- Step (iii) This step is an optional step, and is a step in which a steel material is used as a pipe, the pipe is bent after being subjected to the main heat treatment described above, and a finish heat treatment is performed. If the steel material remains in a tubular state, the tube may not be straight enough to fit the desired use in its longitudinal direction and may be somewhat curved. If this bending occurs, the residual stress of the surface layer of the welded joint becomes high for the ERW steel pipe after production is finished, and the residual stress increases due to straightening of the bending, and stress corrosion cracking (SCC) is likely to occur. Become.
- a steel pipe having a bend cannot be distributed to the market in the first place. For this reason, by adopting this step, the bending can be suppressed, and the occurrence of SCC can be effectively suppressed.
- amendment of the said curvature can be performed using a normal correction apparatus.
- the final heat treatment is applied.
- the residual stress of a steel pipe can be reduced, generation
- the final heat treatment is performed at a temperature of 400 ° C. or higher and Ac1 point or lower.
- the heat treatment temperature in this step is less than 400 ° C, the residual stress is not effectively reduced, so the heat treatment temperature is 400 ° C or higher. In order to further reduce the residual stress, the heat treatment temperature is more preferably 450 ° C. or higher.
- the heat treatment temperature in this step exceeds the Ac1 point, transformation is performed and the structure uniformity is impaired, so the heat treatment temperature is set to Ac1 point or less.
- the heat treatment temperature is preferably set to (Ac1 point ⁇ 10) ° C. or lower.
- the effect of the present invention will be verified by comparing the characteristics of the inventive example (invented steel pipe) with the characteristics of the comparative example (comparative steel pipe). Since various conditions used when manufacturing the steel pipe of the invention are examples of conditions adopted to confirm the feasibility and effects of the present invention, the present invention is not limited to these example conditions. In addition, the present invention can adopt various conditions as long as it does not depart from the gist and achieve the object.
- each of the 20 types of steel strips obtained as described above was continuously formed into a tubular shape, and the edges of the tubular steel strips were welded by high-frequency welding to produce 20 types of tubes (outer diameter 38 mm, meat A thickness of 2.5 mm) was obtained. Thereafter, each pipe was heat-treated under the conditions shown in Table 2 to obtain invention steel pipes 1 to 13 and comparative steel pipes 14 to 20. In Table 2, a blank part means that the final heat treatment was not performed.
- index A Difference between the hardness at the surface layer of the base material part and the hardness at the 1/2 thickness depth position of the base material part
- Index B Difference (Hv) between the hardness of the weld abutting portion 0.5 mm from the outer surface and the hardness of the base metal portion 1 mm from the outer surface
- Index C Perlite area ratio (%) of the weld contact portion 0.5 mm from the outer surface
- Index D Residual stress (MPa) at the surface layer of the weld contact
- the indicators A to D were measured by the method described above or according to the method described above.
- the surface layer part was decarburized both in the base metal part and in the welding contact part. Since the surface layer hardness is reduced, the values of the index A and the index B in Table 3 are not any desired 20 Hv or less. For this reason, the sample of the steel pipe number 13 and the steel pipe number 14 is not an invented steel pipe but a comparative steel pipe.
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Abstract
Description
C :0.05~0.35%、
Si:0.10~0.35%、
Mn:0.25~1.50%、
S :0.035%以下、
P :0.035%以下、
Al:0.005~0.050%、
N :0.010%以下、及び
O :0.010%以下
を含み、
さらに任意選択的に、Cr:1.00%以下、Mo:1.00%以下、Ni:2.00%以下、Cu:2.00%以下、B:0.0030%以下、Nb:0.20%以下、V:0.20%以下、Ti:0.20%以下、Ca:0.0050%以下、Mg:0.0050%以下の少なくとも1種を含み、
残部:Fe及び不可避的不純物であり、
母材部の表層での硬度と母材部の1/2厚み深さ位置での硬度との差が20Hv以下であり、
外表面から1mmまでの溶接衝合部の硬度と、外表面から1mmまでの母材部の硬度と、の差が20Hv以下である
ことを特徴とする、耐応力腐食割れ性に優れたボイラー用電縫鋼管。
C :0.05~0.35%、
Si:0.10~0.35%、
Mn:0.25~1.50%、
S :0.035%以下、
P :0.035%以下、
Al:0.005~0.050%、
N :0.010%以下、及び
O :0.010%以下
を含み、
さらに任意選択的に、Cr:1.00%以下、Mo:1.00%以下、Ni:2.00%以下、Cu:2.00%以下、B:0.0030%以下、Nb:0.20%以下、V:0.20%以下、Ti:0.20%以下、Ca:0.0050%以下、Mg:0.0050%以下の少なくとも1種を含み、
残部:Fe及び不可避的不純物であり、
外表面から1mmまでの溶接衝合部のパーライト面積率が5%以上である、耐応力腐食割れ性に優れたボイラー用電縫鋼管。
上記[1]又は[2]に記載の成分組成の鋼材を成形して管とする工程(i)と、
上記管に、雰囲気炉で、Ac3点以上1250℃以下の温度で30秒以上保持する熱処理を施す工程(ii)と、を含む
ことを特徴とする、耐応力腐食割れ性に優れたボイラー用電縫鋼管の製造方法。
[成分組成]
まず、本願電縫鋼管の成分組成の限定理由について詳述する。なお、以下に示す成分組成の単位[%]は全て質量%を意味する。
本願電縫鋼管は、C、Si、Mn、S、P、Al、N、及びO、並びにFe及び不可避的不純物を、以下に示す各範囲で含有する。
Cは、鋼管の強度を確保するために必要な元素である。0.05%未満では、鋼管の強度が不足するので、Cは0.05%以上とする。好ましくは0.06%以上である。一方、0.35%を超えると、鋼管の硬さが上昇して加工性が劣化するので、Cは0.35%以下とする。好ましくは0.32%以下である。
Siは、固溶強化により鋼管の強度の向上に寄与する元素である。0.10%未満では、添加効果が十分に発現されないので、Siは0.10%以上とする。好ましくは0.15%以上である。一方、0.35%を超えると、鋼管の強度が上昇し過ぎて加工性が低下するので、Siは0.35%以下とする。好ましくは0.30%以下である。
Mnは、焼入れ性を確保し、鋼管の強度の向上に寄与する元素である。0.25%未満では、添加効果が十分に発現されないので、Mnは0.25%以上とする。好ましくは0.27%以上である。一方、1.50%を超えると、鋼管の硬さが上昇し過ぎて加工性が劣化するので、Mnは1.50%以下とする。好ましくは1.45%以下である。
Sは、割れの発生起点となるMnSを形成する元素である。このため、Sはできるだけ少ないほうが好ましいので0.035%以下とする。好ましくは0.030%以下である。下限は0%を含むが、Sを0.0001%未満に低減しようとすると、製造コストが大幅に上昇するので、実用上は、0.0001%が実質的な下限である。
Pは、延性劣化の原因となる粒界偏析や中心偏析を起こす元素である。このため、Pはできるだけ少ないほうが好ましいので0.035%以下とする。好ましくは0.030%以下である。下限は0%を含むが、Pを0.0010%未満に低減すると、製造コストが大幅に上昇するので、実用上は、0.0010%が実質的な下限である。
Alは、脱酸元素である。0.005%未満では、脱酸が十分でなくなるので、Alは0.005%以上とする。好ましくは0.010%以上である。一方、0.050%を超えると、アルミナ系酸化物の粗大化によって加工性が劣化するので、Alは0.050%以下とする。好ましくは0.040%以下である。
Nは、不可避的に存在する元素である。0.010%を超えると、介在物が粗大化して加工性が劣化するので、Nは0.010%以下とする。好ましくは0.008%以下である。下限は0%を含むが、Nを0.0010%未満に低減すると、製造コストが大幅に上昇するので、実用上は、0.0010%が実質的な下限である。
Oは、脱酸後、不可避的に存在する元素である。0.010%を超えると、介在物が粗大化して加工性が劣化するので、Oは0.010%以下とする。好ましくは0.005%以下である。下限は0%を含むが、Oを0.0005%未満に低減すると、製造コストが大幅に上昇するので、実用上は、0.0005%が実質的な下限である。
残部はFeと不可避的不純物である。ここで、不可避的不純部とは、意図的に混入された不純物ではなく、かつ、原材料において含まれる不純物或いは各製造工程において混入され得る不純物をいう。本願電縫鋼管における不可避的不純物としては、例えば、As、Na、Zr、Sbが挙げられる。なお、本願においては、これらの不可避的不純物は、以下のとおり特に含有量(上限値)が限定される。
本願電縫鋼管は、上記に示した元素の他、本願電縫鋼管の特性を損なわない範囲で、Cr、Mo、Ni、Cu、B、Nb、V、Ti、Mgの少なくともいずれかを、以下に示す各範囲で含有してもよい。
Crは、焼入れ性を確保し、鋼管の強度の向上に寄与する元素である。0.05%未満では、添加効果が十分に発現されないので、Crは0.05%以上とすることが好ましい。さらに好ましくは0.10%以上である。一方、1.00%を超えると、鋼管の硬さが上昇し過ぎて加工性が劣化するので、Crは1.00%以下とすることが好ましい。さらに好ましくは0.80%以下である。
Moは、焼入れ性を確保し、鋼管の強度の向上に寄与する元素である。0.05%未満では、添加効果が十分に発現されないので、Moは0.05%以上とすることが好ましい。さらに好ましくは0.10%以上である。一方、1.00%を超えると、鋼管の硬さが上昇し過ぎて加工性が劣化するので、Moは1.00%以下とすることが好ましい。さらに好ましくは0.80%以下である。
Niは、焼入れ性を確保し、鋼管の強度の向上に寄与する元素である。0.10%未満では、添加効果が十分に発現されないので、Niは0.10%以上とすることが好ましい。さらに好ましくは0.15%以上である。一方、2.00%を超える、鋼管の硬さが上昇し過ぎて加工性が劣化するので、Niは2.00%以下とすることが好ましい。さらに好ましくは1.50%以下である。
Cuは、焼入れ性を確保し、鋼管の強度の向上に寄与する元素である。0.10%未満では、添加効果が十分に発現されないので、Cuは0.10%以上とすることが好ましい。さらに好ましくは0.15%以上である。一方、2.00%を超えると、鋼管の硬さが上昇し過ぎて加工性が劣化するので、Cuは2.00%以下とすることが好ましい。さらに好ましくは1.50%以下である。
Bは、焼入れ性を確保し、鋼管の強度の向上に寄与する元素である。0.0003%未満では、添加効果が十分に発現されないので、Bは0.0003%以上とすることが好ましい。さらに好ましくは0.0005%以上である。一方、0.0030%を超えると、粒界脆化を招く場合があるので、Bは0.0030%以下とすることが好ましい。さらに好ましくは0.0020%以下である。
Nbは、CとNとの親和力が強く、NbCNを析出して、鋼管の強度の向上に寄与する元素である。0.005%未満では、添加効果が十分に発現されないので、Nbは0.005%以上とすることが好ましい。さらに好ましくは0.010%以上である。一方、0.20%を超えると、NbCによる析出硬化が顕著となり、加工性が劣化するので、Nbは0.20%以下とすることが好ましい。さらに好ましくは0.10%以下である。
Vは、CとNとの親和力が強く、VNやVCを析出して、鋼管の強度の向上に寄与する元素である。0.005%未満では、添加効果が十分に発現されないので、Vは0.005%以上とすることが好ましい。さらに好ましくは0.010%以上である。一方、0.20%を超えると、VNやVCによる析出硬化が顕著となり、加工性が劣化するので、Vは0.20%以下とすることが好ましい。さらに好ましくは0.10%以下である。
Tiは、Nとの親和力が強く、TiNを析出して、組織の微細化に寄与する元素である。0.005%未満では、添加効果が十分に発現しないので、Tiは0.005%以上とすることが好ましい。さらに好ましくは0.008%以上である。一方、0.20%を超えると、TiCによる析出硬化が顕著となり、加工性が劣化するので、Tiは0.20%以下とすることが好ましい。さらに好ましくは0.10%以下である。
Caは、母材及び電縫溶接部の介在物の形態を調整し、加工性の向上に寄与する元素である。0.0001%未満では、添加効果が十分に発現しないので、Caは0.0001%以上とすることが好ましい。さらに好ましくは0.0005%以上である。一方、0.0050%を超えると、鋼中の介在物が増し、加工性が劣化するので、Caは0.0050%以下とすることが好ましい。さらに好ましくは0.0040%以下である。
Mgは、脱酸元素であり、生成する酸化物は、MnSの析出核として機能するので、MnSの微細化と均一分散に寄与する元素である。0.0050%を超えると、歩留りが低下して、添加効果が飽和するので、Mgは0.0050%以下とすることが好ましい。さらに好ましくは0.0040%以下である。
以下に、本願電縫鋼管においては、(1)硬度に関する限定が必須である。この硬度に関する限定は、
(1-1)母材部の表層での硬度と母材部の1/2厚み深さ位置での硬度との差が20Hv以下であること、及び
(1-2)外表面から1mmまでの溶接衝合部の硬度と、外表面から1mmまでの母材部の硬度と、の差が20Hv以下であること、
の2つの事項を含む。
(1-1)母材部の表層での硬度と母材部の1/2厚み深さ位置での硬度との差(母材部の深さ方向硬度差)、及び
(1-2)外表面から1mmまでの溶接衝合部の硬度と、外表面から1mmまでの母材部の硬度と、の差(特定深さ位置での溶接衝合部と母材部との硬度差)
について調査した。
(1-1)母材部の深さ方向硬度差が20Hv以下であり、かつ
(1-2)特定深さ位置での溶接衝合部と母材部との硬度差が20Hv
であれば、応力腐食割れ(SCC)が発生しないことが確認された。
本願電縫鋼管においては、上記の硬度に関する限定理由に代替して、(2)パーライト面積率に関する限定が必須である。より詳細には、
外表面から1mmまでの溶接衝合部のパーライト面積率が5%以上であること、
が必須である。
(2)外表面から1mmまでの溶接衝合部のパーライト面積率
について調査した。
(2)外表面から1mmまでの溶接衝合部のパーライト面積率が5%以上、
であれば、応力腐食割れ(SCC)が発生しないことが確認された。
なお、特に、上記項目(2)は、後述する熱処理により炭素が拡散して溶接衝合部の炭素濃度が上昇する効果である。
さらに、本願電縫鋼管においては、上述した硬度に関する限定又はパーライト面積率に関する限定に加えて、残留応力に関する限定を任意選択的に採用することができる。この残留応力に関する限定は、
(3)溶接衝合部の表層部の残留応力が200MPa以下であること、である。
(3)溶接衝合部の表層部の残留応力
について調査した。
(3)外表面から1mmまでの溶接衝合部と外表面から1mmまでの母材部との硬度差が20Hvを若干超えても溶接衝合部の表層部の残留応力が200MPa以下
であれば、応力腐食割れ(SCC)が発生しないことが確認された。
加えて、本願電縫鋼管においては、「外表面から1mmまでの溶接衝合部のデンドライト面積率が1%以下である」ことが好ましい。以下にその理由を説明する。
次に、本願製法の限定理由について詳述する。本願製法は、少なくとも、鋼材を管とする工程(工程(i))及び管の熱処理工程(工程(ii))を含む。そして、本願製法は、これらの工程に加えて、管の曲りを矯正しその後に管に対して最終熱処理を施す工程(工程(iii))を任意選択的に含む。
本工程は、必須の工程であって、所定の成分組成の鋼材(熱延コイル)を管に成形する工程である。ここで、所定の成分組成とは上述した成分組成である。また、管への成形装置は、通常用いられる装置、例えば、
・成形機器(鋼材をその上下方向或いは左右方向から押圧して順次オープン管とする複数のロール対を備える機器)、
・溶接機(オープン管の端部同士を溶接する機器)、
・切削機器(溶接ビードを除去する機器)、
・冷却機器(管を冷却する機器)、
・定形化機器(溶接した管を定形化する機器)、
・非破壊検査機器(定形化を行った管を非破壊検査する機器)、及び
・走行切断機器(非破壊検査終了後の管を所定長さに切断する機器)
を備える成形装置を用いることができる。
本工程は上記の各機器を順次用いて、成形、溶接、ビード除去、冷却、定形化、非破壊検査、及び走行切断を順次行う。
本工程は、必須の工程であって、上述した走行切断後の管に熱処理を施す工程である。ボイラー用電縫鋼管は、硝酸塩環境等での使用時に低炭素濃度の溶接部で割れが発生するおそれがあることから、本工程は、母材部の炭素を短時間で溶接衝合部へ効率的に拡散させ、ひいては溶接衝合部のフェライト粒界強度を高めてSCCの発生を抑制し、耐応力腐食割れ性を高めるための工程である。具体的には、管に、雰囲気炉で、Ac3点以上1250℃以下の温度で30秒以上保持する熱処理(以下、単に「本熱処理」と称する場合がある)を施す。 なお、本熱処理後、放冷を経て、最終製品としてのボイラー用電縫鋼管が得られる。
本工程は、任意選択的な工程であって、鋼材を管とし、上述した本熱処理を施した後、管の曲りを矯正し、仕上げ熱処理を施す工程である。鋼材を管状とした状態のままでは、管がその長手方向において所望の使用に適合する程度に直線状をなさず、幾分湾曲しているおそれがある。この曲りがあると、製造終了後の電縫鋼管について、溶接衝合部の表層部の残留応力が高くなり、曲がり取りの矯正で残留応力が大きくなり、応力腐食割れ(SCC)が発生し易くなる。また、曲がりを有する鋼管は、そもそも市場に流通させることができない。このため、本工程を採用することで、当該曲りが抑制され、ひいてはSCCの発生を効率的に抑制すること等ができる。なお、当該曲りの矯正は、通常の矯正装置を用いて行うことができる。
20種類の成分組成を有する、表1に示す各鋼帯を成形した。なお、表1の下部に各鋼帯に関するAc3点の算出方法を併記する。なお、表1中、空欄部はその元素が含まれないことを意味する。
・指標A:母材部の表層での硬度と母材部の1/2厚み深さ位置での硬度との差(Hv)
・指標B:外表面から0.5mmの溶接衝合部の硬度と、外表面から1mmまでの母材部の硬度と、の差(Hv)
・指標C:外表面から0.5mmの溶接衝合部のパーライト面積率(%)
・指標D:溶接衝合部の表層部の残留応力(MPa)
Claims (8)
- 成分組成が、質量%で、
C :0.05~0.35%、
Si:0.10~0.35%、
Mn:0.25~1.50%、
S :0.035%以下、
P :0.035%以下、
Al:0.005~0.050%、
N :0.010%以下、及び
O :0.010%以下
を含み、
さらに任意選択的に、Cr:1.00%以下、Mo:1.00%以下、Ni:2.00%以下、Cu:2.00%以下、B:0.0030%以下、Nb:0.20%以下、V:0.20%以下、Ti:0.20%以下、Ca:0.0050%以下、Mg:0.0050%以下の少なくとも1種を含み、
残部:Fe及び不可避的不純物であり、
母材部の表層での硬度と母材部の1/2厚み深さ位置での硬度との差が20Hv以下であり、
外表面から1mmまでの溶接衝合部の硬度と、外表面から1mmまでの母材部の硬度と、の差が20Hv以下である
ことを特徴とする、耐応力腐食割れ性に優れたボイラー用電縫鋼管。 - 成分組成が、質量%で、
C :0.05~0.35%、
Si:0.10~0.35%、
Mn:0.25~1.50%、
S :0.035%以下、
P :0.035%以下、
Al:0.005~0.050%、
N :0.010%以下、及び
O :0.010%以下
を含み、
さらに任意選択的に、Cr:1.00%以下、Mo:1.00%以下、Ni:2.00%以下、Cu:2.00%以下、B:0.0030%以下、Nb:0.20%以下、V:0.20%以下、Ti:0.20%以下、Ca:0.0050%以下、Mg:0.0050%以下の少なくとも1種を含み、
残部:Fe及び不可避的不純物であり、
外表面から1mmまでの溶接衝合部のパーライト面積率が5%以上である、耐応力腐食割れ性に優れたボイラー用電縫鋼管。 - 前記溶接衝合部の表層部の残留応力が200MPa以下である、請求項1又は2に記載の耐応力腐食割れ性に優れたボイラー用電縫鋼管。
- 前記外表面から1mmまでの溶接衝合部のデンドライト面積率が1%以下である、請求項1から3のいずれか1項に記載の耐応力腐食割れ性に優れたボイラー用電縫鋼管。
- 請求項1~4のいずれか1項に記載の耐応力腐食割れ性に優れたボイラー用電縫鋼管の製造方法であって、
請求項1又は2に記載の成分組成の鋼材を成形して管とする工程(i)と、
前記管に、雰囲気炉で、Ac3点以上1250℃以下の温度で30秒以上保持する熱処理を施す工程(ii)と、を含む
ことを特徴とする、耐応力腐食割れ性に優れたボイラー用電縫鋼管の製造方法。 - 前記工程(ii)の後に、前記管の曲がりを矯正し、その後に400℃以上Ac1点以下の温度で熱処理を施す工程(iii)を含む、請求項5に記載の耐応力腐食割れ性に優れたボイラー用電縫鋼管の製造方法。
- 前記雰囲気炉の雰囲気が酸素を含まない、請求項5又は6に記載の耐応力腐食割れ性に優れたボイラー用電縫鋼管の製造方法。
- 前記雰囲気炉の雰囲気が、アルゴン、窒素、二酸化炭素、及び水素の少なくとも1種である、請求項7に記載の耐応力腐食割れ性に優れたボイラー用電縫鋼管の製造方法。
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Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5132415A (ja) * | 1974-09-14 | 1976-03-19 | Sumitomo Metal Ind | Denhokokan |
JPS60116722A (ja) * | 1983-11-28 | 1985-06-24 | Nippon Steel Corp | 加工性の優れたボイラ用鋼管製造法 |
JPH04191323A (ja) * | 1990-11-22 | 1992-07-09 | Sumitomo Metal Ind Ltd | 切削性に優れたシリンダー用鋼管の製造法 |
JP2002294402A (ja) * | 2001-03-28 | 2002-10-09 | Nippon Steel Corp | 耐摩耗特性に優れた低合金耐熱ボイラー用鋼管 |
KR20080087548A (ko) * | 2007-03-27 | 2008-10-01 | 현대하이스코 주식회사 | 보일러용 내열합금강관 |
JP2016079431A (ja) * | 2014-10-14 | 2016-05-16 | 新日鐵住金株式会社 | 油井用電縫鋼管及びその製造方法 |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3101174C2 (de) * | 1981-01-16 | 1983-02-10 | Brohltal-Deumag AG für feuerfeste Erzeugnisse, 5401 Urmitz | Wärmetauscher, insbesondere Winderhitzer |
JP4276341B2 (ja) * | 1999-09-02 | 2009-06-10 | 新日本製鐵株式会社 | 引張強さ570〜720N/mm2の溶接熱影響部と母材の硬さ差が小さい厚鋼板およびその製造方法 |
US9757780B2 (en) * | 2009-03-25 | 2017-09-12 | Nippon Steel & Sumitomo Metal Corporation | Electric resistance welded steel pipe excellent in deformability and fatigue properties after quenching |
JP6193206B2 (ja) * | 2013-12-11 | 2017-09-06 | 株式会社神戸製鋼所 | 耐サワー性、haz靭性及びhaz硬さに優れた鋼板およびラインパイプ用鋼管 |
-
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Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5132415A (ja) * | 1974-09-14 | 1976-03-19 | Sumitomo Metal Ind | Denhokokan |
JPS60116722A (ja) * | 1983-11-28 | 1985-06-24 | Nippon Steel Corp | 加工性の優れたボイラ用鋼管製造法 |
JPH04191323A (ja) * | 1990-11-22 | 1992-07-09 | Sumitomo Metal Ind Ltd | 切削性に優れたシリンダー用鋼管の製造法 |
JP2002294402A (ja) * | 2001-03-28 | 2002-10-09 | Nippon Steel Corp | 耐摩耗特性に優れた低合金耐熱ボイラー用鋼管 |
KR20080087548A (ko) * | 2007-03-27 | 2008-10-01 | 현대하이스코 주식회사 | 보일러용 내열합금강관 |
JP2016079431A (ja) * | 2014-10-14 | 2016-05-16 | 新日鐵住金株式会社 | 油井用電縫鋼管及びその製造方法 |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2021033647A1 (ja) * | 2019-08-20 | 2021-02-25 | 日本製鉄株式会社 | 接合継手、自動車用部材、及び接合継手の製造方法 |
JPWO2021033647A1 (ja) * | 2019-08-20 | 2021-02-25 | ||
JP7156541B2 (ja) | 2019-08-20 | 2022-10-19 | 日本製鉄株式会社 | 接合継手、自動車用部材、及び接合継手の製造方法 |
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