WO1996025530A1

WO1996025530A1 - High-strength ferritic heat-resistant steel excellent in resistance to embrittlement caused by intermetallic compound deposition

Info

Publication number: WO1996025530A1
Application number: PCT/JP1996/000319
Authority: WO
Inventors: Yasushi Hasegawa; Masahiro Ohgami; Hisashi Naoi
Original assignee: Nippon Steel Corporation
Priority date: 1995-02-14
Filing date: 1996-02-14
Publication date: 1996-08-22

Abstract

A martensitic heat-resistant steel that is excellent in high-temperature creep strength, contains Co, and does not yield an intermetallic compound with an approximate composition of Cr40Mo20Co20W10C2-Fe at a temperature as high as 600 °C. The deposition of the above intermetallic compound is suppressed and an excellent high-temperature creep strength is secured by adding minute amounts of Mg, Ba, Ca, Y, Ce, La, etc., and small amounts of Ti and Zr to a heat-resistant steel containing at least 8 % Cr and also Co, Mo and W.

Description

Description High-strength, heat-resistant steel with excellent intermetallic compound precipitation embrittlement resistance Technical field

The present invention relates to a heat-resistant steel-based steel, and more particularly, to an excellent creep rupture strength for use in a high-temperature and high-pressure environment and an excellent intermetallic compound precipitation embrittlement resistance. This is related to heat-resistant steels. Background art

In recent years, the operating conditions of thermal power boilers have been remarkably high temperature and high pressure, and in some cases, operation at 566 ° C and 316 bar is planned. In the future, conditions up to 649 ° C and 352 bar are assumed, and the materials used will be extremely harsh.

The refractory materials used in thermal power plants are exposed to different environments depending on where they are used. In areas with high ambient temperatures, called so-called superheater tubes and reheater tubes, austenitic materials with particularly excellent corrosion resistance and strength at high temperatures, or 9 to 12 when considering steam oxidation resistance and thermal conductivity Martensite-based materials containing% Cr are often used.

In recent years, new heat-resistant materials that have been newly added to W to improve the high-temperature strength have been researched, developed, and put into practical use, and have greatly contributed to achieving higher efficiency of power generation plants. For example, the use of W as a solid solution strengthening element has been disclosed in JP-A-63-89644, JP-A-6-231139, JP-A-62-297435, etc. Compared to conventional Mo-containing heat-resistant heat-resistant steel, it is possible to achieve a dramatically higher creep strength. There is disclosure about hot steel. In many cases, these have a single-phase tempered martensite structure, which combines the advantages of ferritic steel with excellent steam oxidation resistance and high-strength properties to create next-generation high-temperature and high-pressure. It is expected as a material used in the environment. As an example, 12% Cr steel having excellent high-temperature creep strength is disclosed in JP-A-5-263196, JP-A-5-311342, JP-A-5-311343, and JP-A-5-311344. Gazette, _JP-5 - ₃₁₁₃ 45 JP, Hei 5 - disclosed in 311346 JP.

The high-temperature strength of the heat-resistant steel is controlled by solid solution strengthening and precipitation strengthening. Recent technologies have succeeded in increasing the high-temperature creep strength by blending the two in a well-balanced manner. W and Mo are used for solid solution strengthening, and Nb and V and their carbides or nitrides are used for precipitation strengthening. It has been confirmed that it is effective for improving the break rupture strength. The only practical problem with these additive elements that are effective in improving the strength is that any of them is a ferrite stabilizing element, so the Cr equivalent value of the material is increased, and as a result, the structure becomes Instead of a single phase, it will have a two-phase structure of delta-plated tempered martensite. The two-phase structure has characteristics different from those of the martensite single-phase structure, and is often avoided when uniform material properties are required. In addition, since interphase distribution of various elements occurs, a problem may occur in a material having insufficient corrosion resistance.

Therefore, it is indispensable to use a single-phase structure in the material of a heat-resistant steel that achieves high strength by obtaining a tempered martensite structure. The usual method is to add a certain amount of a stabilizing element and to design the components to obtain a martensitic single-phase structure during cooling after solution heat treatment.

Austenitic stabilizing elements used for the above purposes include Ni, Mn, Co, Cu, C, N, etc., where high-temperature creep strength is important. In this case, Ni and Mn are excluded from the selection candidate elements based on the reason for inducing a decrease in the creep strength, and Cu is excluded in order to ensure weldability. Since N and N greatly change the mechanical properties of a material, its design is often determined in consideration of the balance between the strength and toughness of the material. In many cases, it cannot be used for addition. Therefore, Co, which is expensive but does not significantly affect other mechanical properties, is finally selected and is being used in recent heat-resistant steels.

The present inventors have paid attention to the new ferritic heat-resistant steel technology mainly composed of W, Mo, and Co. Depending on the chemical composition and heat treatment conditions, ferrite-based heat-resistant steel In general, Cr ₄ was not observed. Mo ₂ . Co _2. W,. An intermetallic compound having a composition of C ₂ —Fe (presumed to be a subspecies of ASTM force number 23-196) was found to precipitate. Therefore, this intermetallic compound precipitates in a Cr steel to which Co, W, and Mo are added in a practical use environment, and its morphology is film-like, and 50 m along the grain boundary. It has been found that it can grow rapidly to oversize.

In the material in which this intermetallic compound is precipitated, the creep rupture strength is about 30% as the estimated rupture strength outside the straight line for 100,000 hours, and the ductile brittle fracture fiber temperature rises about 40 ° C in the toughness test after aging. This was also found as a result of the study.

Therefore, from the results of this study, in high-strength Co, Mo, W composite-added heat-resistant steel containing 8% or more of Cr, unless the technology to suppress the precipitation of the intermetallic compound was developed, the severeness of 650 ° C and 350 atm was considered. It has become clear that it is difficult to use it in various environments.

Further research by the present inventors revealed that this film-like intermetallic compound If a small amount of Mg, Ba, Ca, Y, Ce, La, etc., which has been added as a desulfurizing material to fix S in steel at the same time, is added simultaneously, precipitation of about 70% is suppressed. Furthermore, the addition of a small amount of the strong carbide-forming elements, Ti and Zr, fixes the C contained in the intermetallic compound in a very small amount. It was also found that spheroidization occurs when precipitation occurs. If both techniques are not used simultaneously, it is difficult to completely suppress the precipitation of intermetallic compounds, and when only one of them is used, the creep rupture strength is reduced by about 20% and the elongation is reduced. A rise of 20 ° C in brittle fracture surface fiber temperature cannot be avoided. Disclosure of the invention

The present invention has the above-mentioned disadvantages of the conventional steel, namely, approximately Cr. ¾ <0 ₂ . (; 0 _2. \ ^. Prevents precipitation of intermetallic compounds having a composition of C ₂ _Fe, contains 8 to 13% of Cr, has sufficient corrosion resistance, and contains Mo and W. It is an object of the present invention to provide a new frit-based heat-resistant steel having a Co-containing martensite single-phase structure having high creep rupture strength. According to

C: 0.01 ~ 0.30%, Si 0.01 ~ 0.80%,

Mn: 0.20 to 1.50%, Cr 8.00 to 13.00%,

Mo: 0.01 ~ 3.00%, W 0.10 ~ 5.00%,

Co: 0.05 to 600%, V 0.002 to 0.800%

Nb: 0.002 to 0.500% N 0.002 to 0.200%

Containing, in addition to

Ca 0.0005 ~ 0.0050%, Ba 0.0003 ~ 0, 0020%

Mg 0.0005- 0.0050%, La 0.001-0.020%

Ce 0.001 to 0.020%, Y 0.001 to 0.020% Of Ca, Ba, and Mg in the form of precipitates, and La, Ce, and Y in the form of precipitates or solid solutions.

Ti: 0.002-0.500%, Zr: 0.002-0.500%

Contains one or two of the above, alone or in combination, or

Ni: 0.10 to 2.00%, Cu: 0.10 to 2.00%

One or two of the above may be used alone or in combination.

B: 0.0005 to 0.010%

Containing

P: 0.030% or less, S: 0.010% or less,

0: 0.020% or less

The present invention provides a high-strength, high-temperature, heat-resistant steel excellent in intermetallic compound precipitation embrittlement resistance, characterized in that the balance is limited to Fe and inevitable impurities. BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a perspective view showing the steel sheet specimen, the rolling direction, and the sampling direction of the creep rupture strength evaluation specimen;

Figure 2 is a graph showing the effect of adding Ti, Zr and Ca, Ba, in steel;

Fig. 3 is a graph showing the effect of adding Ti, Zr and La, Ce, Y in steel;

Figure 4 shows the results of the creep rupture strength evaluation of the steel of the present invention and an example of the estimated creep rupture strength outside the straight line at 650 ° C for 100,000 hours based on the results. This is a graph shown in comparison with the data band of the break rupture strength; Figure 5 is a graph showing the relationship between W content in steel and creep rupture strength;

Figure 6 is a graph showing the relationship between the Co content in steel and creep rupture strength. BEST MODE FOR CARRYING OUT THE INVENTION

The reason for limiting each component range in the present invention as described above will be described below.

C is necessary for maintaining strength, but if it is less than 0.01%, it is not enough to secure strength, and if it exceeds 0.30%, the heat affected zone is hardened significantly, causing low temperature cracking during welding. Therefore, the range was set to 0.01 to 0.30%. C is contained in trace amounts even in harmful intermetallic compounds, but there is no correlation between the amount of added C and the precipitation conditions of intermetallic compounds.

Si is important for ensuring oxidation resistance and is a necessary element as a deoxidizing agent.However, if it is less than 0.01%, it is insufficient, and if it exceeds 0.80%, the creep strength is reduced, so 0.02 to 0.80 % Range.

Mn is a component necessary not only for deoxidation but also for maintaining strength. To obtain a sufficient effect, it is necessary to add 0.20% or more, and if it exceeds 1.50%, the creep strength may decrease. Therefore, the range was set to 0.20 to 1.50%.

Cr is an element essential to the oxidation resistance, Cr ₂ combines with C at the same time

₃ C _6, and contributes in the form of such Cr ₇ C ₃ in the base material Ma Bok Li Tsu fine precipitates child in click scan to increase the click rie blanking strength. From the viewpoint of oxidation resistance, the lower limit was set to 8.00%, and the upper limit was set to 13.00% in order to stably obtain a martensite single phase structure.

W is an element that significantly increases creep strength by solid solution strengthening, and significantly enhances long-term creep strength especially at high temperatures of 500 ° C or higher. . When added in excess of 5.00%, a large amount of Laves phase intermetallic compound precipitates mainly at the grain boundaries and significantly lowers the base metal toughness and the creep strength, so the upper limit was set to 5.00%. If the content is less than 0.10%, the effect of solid solution strengthening is insufficient, so the lower limit was set to 0.10%.

Co is an effective element for lowering the Cr equivalent value without significantly changing the mechanical properties and the thermodynamic properties such as the transformation point of the material, such as the strength and toughness. No effect as the austenite stability element is less than 0.05%, if added over 6.00%, the intermetallic compound of Co entity (schematic _{_{C Γ 4 .ΜΟ 2 (:.}} Ο 2 .Ι ^. (Different in structure and properties from the intermetallic compound having the composition of ₂ —Fe) precipitates in large quantities, and the creep rupture strength of the base material is reduced. Therefore, the addition range is determined to be 0.05 to 6.00%. did.

Mo is also an element that enhances high-temperature strength by solid solution strengthening. <Less than 0.01%, the effect is insufficient.If it is more than 3.00%, a large amount of Mo ₂ C-type carbide precipitates, or Fe ₂ Mo-type The upper limit was set to 3.00% because the toughness of the base metal may be significantly reduced when it is added simultaneously with W due to the precipitation of intermetallic compounds.

V is an element that remarkably enhances the high-temperature creep rupture strength of steel, whether it precipitates as a precipitate or forms a solid solution in the matrix like W. In the present invention, if the content is less than 0.002%, precipitation strengthening by V precipitates is insufficient, and if it exceeds 0.800%, clusters of V-based carbide or carbonitride are formed, resulting in a decrease in toughness. The range was 0.002 to 0.800%.

Nb enhances high-temperature strength by precipitation as MX-type carbide or carbonitride, and also contributes to solid solution strengthening. If less than 0.002%, the effect of addition was not recognized, and if added more than 0.500%, coarse precipitation occurred and the toughness was reduced, so the addition range was limited to 0.002 to 0.500%.

N forms solid solution in the matrix or precipitates as nitride or carbonitride. However, mainly in the form of VN, NbN, or their respective carbonitrides, they contribute to both solid solution strengthening and precipitation strengthening. Addition of less than 0.002% hardly contributes to strengthening, and the upper limit of addition is set to 0.200% in consideration of the upper limit value that can be added to molten steel depending on the amount of Cr added up to 13%.

One or more of Ca, Ba, Mg, Y, Ce, and La: Ca: 0.0005-0.0050%, Ba: 0.0003-0.0020%, Mg: 0.0005-0.0050%, La: 0.001-0.020% , Ce: 0.001 to 0.020%, and Y: 0.001 to 0.020%, are just one of the fundamental technologies of the present invention. Mo ₂ . Co _2. W _1. Prevents about 90% of grain boundary film-like precipitation of intermetallic compounds having the composition of C ₂ —Fe. Ca, Ba, and Mg hardly form a solid solution in steel, and exist mainly as sulfides near the grain boundaries or as inclusions in the form of oxides inside the grain boundaries. Each is strong 0 ₂ . (: 0 ₂ .. (: ₂ — Fe intermetallic compound formation inhibiting element, which temporarily decomposes from the form of sulfide or oxide and cuts the lattice structure of the intermetallic compound to form another spherical intermetallic compound. Compound or intermetallic compound is re-dissolved in steel.

La, Ce, and Y exist in the form of sulfides and oxides, or dissolve in steel, and suppress the formation of intermetallic compounds by the same mechanism as Ca, Ba, and Mg. In this case, Y, Ce, and La in a solid solution state have a higher effect of suppressing the formation of intermetallic compounds than in a precipitation state. In any case, the effect is the highest in the above component range, the effect is insufficient when the amount is less than the lower limit, and when the amount is excessive, the hot workability decreases with Ca, Ba, and Mg, and Y, Ce, La defines the above-mentioned component range because a large number of coarse oxides are generated and the toughness is reduced.

Ti and Zr have a strong carbide-producing ability to capture C, a trace constituent element in the intermetallic compound, and as a result, have the function of spheroidizing the intermetallic compound. This technique is also the basis of the present invention. Less than 0.002% The effect is insufficient, and if added over 0.500%, coarse carbides, carbonitrides, or nitrides precipitate and reduce toughness, so the addition range was limited to 0.002 to 0.500%.

Ti and one or a Ca of Zr, Ba, Mg, Ce, Y, addition of technology one or two or more kinds of La is to be applied at the same time Cr _4. Mo ₂ . Co _2. ₀ The formation of C ₂ —Fe intermetallic compounds cannot be completely suppressed, and the desired mechanical properties cannot be secured. This composite addition technique is an essential element of the present invention and is the most significant feature. This composite addition effect was confirmed based on the following experiment.

Except for Ti, Zr, Ca, Ba, Mg, La, Ce, and Y, steels in the chemical composition range of the present invention are melted with V1M (vacuum induction heating furnace) and EF (electric furnace), and A0D (Ar oxygen blow decarburizer), V0D (Vacuum exhaust oxygen blow decarburizer), LF (Molten steel ladle refiner) and use it continuously or with a normal steel ingot A slab having a maximum cross section of 210 X 1600 mm or a billet having a cross-sectional area smaller than that in the case of a continuous slab is formed by a steel slab. After being formed into ingots of size, they were forged or hot-rolled to form ingots (having various sizes of 10 kg to 20 tons) of a size that would not interfere with the subsequent investigation.

Slabs, billets, and ingots were subjected to a solution treatment (normalizing treatment) at 1100 ° C for 1 hour, air-cooled, and quenched into a martensite structure. It was reheated to 780 ° C, below the temperature, tempered for one hour, and then air-cooled.

From the heat-treated specimens, creep rupture strength evaluation specimens (2) were sampled in the direction shown in Fig. 1 for the hot rolled material in parallel with the rolling direction (3) of the steel sheet (2), and from the forged ingots, Similarly, creep rupture test pieces were collected from the longitudinal direction of the test pieces. Intermetallic compound precipitation behavior of test materials In order to investigate this, a block test piece was cut out from the creep-ruptured test piece, the substrate was electrolyzed with an organic acid, and the precipitate was separated and extracted by suction filtration. The extracted residue is quantitatively analyzed using a calibration curve by atomic absorption spectroscopy or gas chromatography, or

X-ray diffraction qualitative analysis confirmed the presence of each precipitate. In addition, thin film samples or replica samples were prepared as necessary, and the structure of the precipitates was analyzed and the morphology was observed.

The creep rupture strength was evaluated by estimating the creep rupture strength of 100,000 hours outside the straight line based on the creep rupture strength measurement data for 10,000 hours at 650 ° C. Assuming the boiler operating conditions at 650 ° C and 350 bar, the OOMPa was set to the standard value, taking into account the stress applied to parts such as steam piping and heat exchangers. That is, if the creep rupture strength estimated at 650 ° C. and 100,000 hours by linear extrapolation exceeds l OOMPa, there is almost no precipitation of intermetallic compounds, and the creep rupture which is the object of the present invention is intended. It was considered that the strength was achieved.

Figure 2 shows the estimated creep rupture strength outside the straight line at 100,000 hours at 650 ° C in Mpa units. One of Ti or Zr and one of Ca, Mg, Ba FIG. 4 is a diagram plotting the concentration of each additive element when one of them is added. The number in the plot circle indicates the creep rupture strength (MPa). Element symbols below or beside the circle indicate the selected additive element type.

When only Ti or Zr alone or one of Ca, Ba and Mg was added alone, regardless of the amount of addition, the temperature was 650 ° C for 100,000 hours. The estimated creep rupture strength outside the straight line is less than 10 OOMPa. This indicates that the addition of Ti, Zr, or Ca, Mg, or Ba alone could not suppress the precipitation of intermetallic compounds and reduced creep rupture strength. On the other hand, one kind of Ti or Zr and one kind of Ca, Mg, Ba When the amount of addition is within the range, that is, when Ti and Zr are 0.002 to 0.500%, Ca and Mg are 0.0005 to 0.0050%, and Ba is 0.0003 to 0.0020%, the creep rupture strength exceeds lOOMPa, and the Microscopic analysis and quantification and qualitative analysis of electrolytic extraction residues indicated that the specimens with a creep rupture strength of 10 OMPa or more were roughly rated C. It was confirmed that no intermetallic compound having a composition of MO CO W-Fe (presumed to be a subspecies of ASTM force No. 23-196) was not precipitated. Conversely, if the composition is out of the range of the present invention, the steel to which Ti, Zr, Ca, Mg, and Ba are added has approximately Cr ₄ . Mo ₂ . Co _2. W,. An intermetallic compound having a composition of C ₂ —Fe was detected, and its presence was confirmed.

Figure 3 shows the results of performing exactly the same experiment, replacing the Ca, Mg, and Ba groups in Figure 2 with Y, Ce, and La. The behavior of γ, Ce, La was exactly the same as Ca, Mg, Ba. In other words, when Y, Ce, and La are 0.001 to 0.020% and Ti and Zr are 0.002 to 0.500%, out of a straight line at 650 ° C for 100,000 hours. 揷 The estimated creep rupture strength is lOOMPa or more, and ₄ . Mo ₂ . Co ₂₀ W,. An intermetallic compound having a composition of C ₂ —Fe was not detected. Conversely, in steels containing Ti, Zr, Ca, Mg, and Ba that are out of the component range of the present invention,

, Schematic (; _"4 \ 10 ₂ (0 _2" _[1 (:..... An intermetallic compound having a ₂ _ 6 having a composition able to detect, in is found confirming its existence, this In all cases, the creep rupture strength was always below 100MPa.

The above results show that each of the elements of the present invention was obtained in the case where Ti and Zr were added in combination, and in the case where two or more of Ca, Mg, Ba, Y, La and Ce were added in combination. The situation was exactly the same when it was within the chemical composition range and when even one was out of the range. Table 1 shows some of these results.

That is, it is necessary to add one or two kinds of Ti and Zr in combination with one or more kinds of Ca, Mg, Ba, Y, Ce and La, and It has been found that the added amounts of various elements must be the values specified in the claims.

The method for melting the steel of the present invention is not limited at all, and the process to be used may be determined in consideration of the chemical composition and cost of the steel, such as a converter, an induction heating furnace, an arc melting furnace, and an electric furnace. . However, the production process is equipped with a hopper to which Ti, Zr, Ca, Mg, Ba, Y, Ce, and La can be added, and the oxygen concentration in the molten steel does not slag as an oxide of these added elements. It must be capable of controlling it sufficiently low. Therefore, it is useful to apply an LF or vacuum degassing device equipped with an Ar bubble blowing device, an arc heating device, or a plasma heating device, which enhances the effects of the present invention. Other manufacturing processes, specifically rolling, heat treatment, pipe making, welding, cutting, inspection, etc., which are considered necessary or useful for manufacturing steel or steel products according to the present invention, shall be applied. It does not hinder the effects of the present invention.

In particular, in the manufacturing process of the steel pipe, under the conditions including the manufacturing process of the present invention, after being processed into a round billet or a square billet, it is hot-extruded or variously seamless. Rolling method to form seam repipe and tube, hot rolling to thin plate, cold rolling and then to electric resistance welding by electric resistance welding, and T1G, MIG, SAW, LASER, EB welding alone In addition to the above methods, it is possible to apply a method of forming a welded steel pipe, and after each of the above methods, hot (or hot) SR (draw rolling) or regular rolling, and various types of straightening. It is also possible to carry out additional steps, and it is possible to expand the applicable dimensional range of the steel of the present invention.

The steel of the present invention can also be provided in the form of a thick plate and a thin plate, and can be used in the form of various heat-resistant materials by using a plate subjected to a necessary heat treatment. Which has no effect on the effects of the present invention. Absent.

In addition, powder metallurgy methods such as HIP (hot isostatic pressing and sintering), C1P (cold isostatic pressing) and sintering can be applied. Therefore, it is possible to obtain products of various shapes by applying the necessary heat treatment after the molding process.

The above-described steel pipes, plates, and heat-resistant members of various shapes can be subjected to various heat treatments according to the purpose and application, respectively, and are important in sufficiently exerting the effects of the present invention.

Normally, products are usually subjected to normalizing (solution heat treatment) + tempering process, but in addition to this, re-tempering and normalizing processes can be performed alone or in combination. Yes, and useful. However, it is essential to stop and maintain the cooling after the solution heat treatment.

When the nitrogen or carbon content is relatively high, when the content of austenitic stabilizing elements such as Co and Ni is high, or when the Cr equivalent value is low, 0 ° C to avoid the residual austenite phase It is possible to apply a so-called cryogenic treatment for cooling below, which is effective for sufficiently expressing the mechanical properties of the steel of the present invention.

The above steps can be applied by repeating each step a plurality of times within a range necessary for sufficiently exhibiting material properties, and do not affect the effects of the present invention at all.

The above steps may be appropriately selected and applied to the steel manufacturing process of the present invention. Example

As shown in Table 1, 300 tons, 120 tons, 60 tons, 1 ton, 300 kg, 100 kg, and 50 kg of the steel of the present invention were respectively blasted using a normal blast furnace iron-converter blowing method, VIM, EF or a laboratory vacuum melting equipment. Melted, with arc reheating equipment Refined by LF equipment capable of injecting Ar or a small reproduction test equipment with the same capacity, and made into 1200 mm x 210 mm pieces and 560 x 210 mm billets by continuous manufacturing, or by ordinary ingot making method The ingot was made from 50 kg to 50 ton. The obtained flakes, billets and ingots can be hot rolled or hot forged into plates of 50 thickness and 12 plates, or round billets. Then, a tube with an outer diameter of 74 mm and a wall thickness of 10 mm was manufactured by hot extrusion, and a pipe with an outer diameter of 380 mm and a wall thickness of 50 IMI was manufactured by seamless rolling. Furthermore, the thin plate was formed and subjected to ERW welding to form an ERW steel pipe with an outer diameter of 280 mm and a wall thickness of 12 mm.

All plates and tubes were subjected to solution heat treatment at a maximum heating temperature of 950 to 1350 ° C for 1 hour, then air-cooled, and then tempered at 750 to 800 hours for 1 hour.

The creep characteristics of the base metal were determined as shown in Fig. 1 by cutting out a 6 mm-diameter creep test specimen 測 and measuring the creep rupture strength at 650 ° C for up to 10,000 hours. The obtained data was extrapolated to a straight line to obtain a creep rupture strength of 100,000 hours.

Figure 4 shows the measurement results of the base metal's break rupture strength up to 10,000 hours, together with an extrapolated straight line of the estimated break strength at 100,000 hours. It can be seen that the high-temperature creep rupture strength of the steel of the present invention is higher than that of the conventional 9-12% Cr steel.Figure 5 shows the W content and creep rupture estimated at 650 ° C for 100,000 hours. It is a figure which shows the relationship of intensity. When the W content is between 0.10 and 5.00%, the creep rupture strength exceeds 100MPa.

Figure 6 shows the relationship between the Co content and the estimated creep rupture strength at 650 ° C for 100,000 hours. If the Co content is 0.05% or more, the creep rupture strength becomes 100MPa or more.If the addition exceeds 6.0%, an intermetallic compound mainly composed of Co is precipitated and cleaved. Breaking strength decreases O

For comparison, a steel which does not correspond to any of the present invention in chemical composition was evaluated by the same method. Chemical composition and evaluation results CRS (Estimated creep rupture strength at 650 ° C, 100,000 hours estimated by linear extrapolation from measurement results of creep rupture strength up to 10,000 hours at 650 ° C, 10,000 hours) Table 2 shows the analysis results of the intermetallic compounds.

Of the comparison steels in Table 2, the 98th and 99th steels have no added Ti and Zr, and are outlined. ₂ . .. (; 0 ₂ "/ ₁ ₍₂ - intermetallic compound having a 6 a composition Chikaraku, in click Li-loop test 650 ° C, precipitated in the grain boundaries in the full I Lum shape, 650 .C, An example in which the estimated creep rupture strength by linear extrapolation for 100,000 hours decreased.No. 100 steel contained more than 0.5% Ti, large amounts of coarse carbonitrides were generated, and the toughness was 0 ° C immediately after heat treatment. In this case, the creep rupture strength was extremely low at 2 J, and at the same time, the creep rupture strength was reduced. In the case of steel No. 102, both Ti and Zr exceeded 0.5%, large amounts of coarse carbonitrides were generated, and the toughness was 0% immediately after heat treatment. At 0.5 ° C, it was extremely low at 0.5J, and at the same time, the creep rupture strength decreased. Choose from For that element a does not contain one or more, schematic _{C Mo Co ^ W, .C 2} -. Intermetallic compounds with Fe made composition, in click Li-loop test 650 ° C, off the grain boundaries This is an example of precipitation in the form of a film, and the estimated creep rupture strength outside the straight line at 650 ° C for 100,000 hours decreased.

Steel No. 105 is Ca, Steel No. 106 is Mg, Steel No. 107 is Y, Steel No. 108 is Ce, respectively, exceeding 0.005%, 0.005%, 0.02%, 0.02%, and Ca, Mg added steel In the case where the hot workability deteriorates and the ingot cracks during hot rolling and the production fails, in the case of Y and Ce-added steel, a large number of coarse oxides are generated in large quantities, and the toughness decreases immediately after the heat treatment. 0.8J at 0, and 0.5J and pole At the same time, almost all of Y and Ce were present in the steel as oxides, so that the effect of suppressing the formation of intermetallic compounds could not be exhibited, resulting in a decrease in creep rupture strength. Example No. 109 steel had no added C and thus had low creep rupture strength.No. 110 steel had too much W and a large amount of Fe ₂ W type Laves phase was precipitated, resulting in creep rupture strength. No. 111 steel lacked Co, a large amount of delta fluoride remained, and the creep rupture strength decreased.Steel No. 112 was excessive in Co and was mainly composed of Co. This is an example in which a compound (Fe ₂ Co) is precipitated and the creep rupture strength is reduced.

Table 1 (111): Steel of the present invention

Table 1 (1-2): Steel of the present invention

CRS: 650 ° C, chestnut up to 10,000 f ^ f¾ ^^], Naotsuru ^ Estimated 650 ° C, 100,000 estimated chestnut

«Alternation: 瞧 Cr Jo ₂ . Co _2. W, — Identification of ^ intercalated ^ l with Fe fibers by X-ray diffraction and electron microscopy MSg ^.

Other metallization ^ J

6ISd one 0 £ si6 ΟΑλ

酶 ½¾ 本： (ϊ-2) ΐ

Table 1 (2-2): Steel of the present invention

o o o o o o o o o o o o

LO

in CD

o

D to m

Table 1 (3-2): Steel of the present invention

CRS: Clearance up to 10,000 at 650 ° C ¾S «iJ ii Pla H i Estimated 650 ° C 100,000 B # f _B

Presence or absence of intermetallic compound: X-ray diffraction of intermetallic ^ with composition Cr.nMo, nCo ₂₀ W, _nC ₂ —Fe, by mm

Other interludes ^! Will be displayed as "Yes" on their own.

Table 1 (4-1): Steel of the present invention

ο:

Να C 01 Μη Ρ S Cr Μθ W Co Nb V Ν 0

7D 013ο 0.5ο9 0.5 ^ 0.0058 0.0097 9.746 0.136 3.316 4.612 0.426 0.259 0.1840 ώ014ώ

77 0.28ο 1.143 0.0232 0.0061 10.521 0.256 1.022 1.267 0.361 0.561 0.0510

78 0.094 0, J85 0, 75 0.0050 0.0094 8.926 0.166 4.251 0.996 0.363 0.002 0.1 ^ 90 ϋ

79 U.151 0.όίΐ 1.147 0.0058 11.220 0.296 0.798 0.982 0.98 0.4 ^ 9 0.115ο Ul

80 0.10b 0.49ο 0.000b 9.884 0.280 0.407 1.110 0.όο 0.όίο 0.14 ^ 7

J eight

81 0.165 0.656 1.095 0.0064 0.0034 12.629 0.211 1.432 1.110 0.410 0.394 0.0781 0.0115

82 0.132 0.214 1.026 0.0245 0.0002 10.073 0.047 1.253 4.618 0.355 0.796 0.1040 0.ΌΰΔό

83, 0 ^ 1 0, 1ο4 1.489 0 0037 0.0055 10.500 0.144 1.058 4.348 0.157 0, 4ο4 0.057ο 01U5

84 0.059 0.18 ^ 577 0.O ^ bd 0.ΟΟ ο 10.7ab 534 0.ϋ 4 0.434 U.0UJ7 U.UU7U fl

85 0.258 0.130 1.330 0.0243 0.0042 11.900 0.189 1.565 4.986 0.429 0.536 0.0402 0.0200

86 0.113 0.196 0.725 0.0193 0.0043 12.768 0.039 2.351 1.996 0.350 0.223 0.0939 0.0073

87 eighty no

ϋ, 1ό6 ϋ 590 1, 397 0 · 078 0.Wic 8.777 0.041 380 .80ο 0.015 0Ob 0.05 ^ 4 0.0001

88 0 0 8 0 0 44 0.544 0.0126 0.0075 9.701 0.253 2.474 0.575 0 023 0 252 0.0911 0.0115

89 0.Ub 0.54ο 1.όοό 0.0175 0.0079 8.Οοο 0.045 1.956 L.650 0.171 0.419 0.1623 0.0083 υ.β ηι Δνι U.0U U.ο9ο U. / U. i U. UlDo U. Ulol

91 0.014 0.018 0.804 0.0071 0.0096 8.117 0.181 2.956 4.184 0.192 0.694 0.0291 0.0189

92 0.141 0.038 0.981 0.0020 0.0068 8.098 0.297 4.117 0.489 0.320 0.587 0.1805 0.0003

93 0.049 0.735 1.344 0.0083 0.0050 8.375 0.210 0.835 2.526 0.292 0.710 0.1420 0.0112

94 0.190 0.685 1.219 0.0019 0.0054 9.371 0.162 3.772 3.725 0.498 0.766 0.1552 0.0185

95 0.266 0.694 1.208 0.0126 0.0012 11.607 0.174 2.689 5.947 0.428 0.429 0.1928 0.0117

96 0.069 0.476 1.143 0.0168 0.0012 10.540 0.275 3.016 5.368 0.115 0.075 0.0142 0.0158

97 0.162 0.073 0.263 0.0118 0.0096 10.515 0.198 4.595 4.394 0.196 0.076 0.1853 0.0173

Table 1 (4-2): Steel of the present invention

CRS: 650 ° (: chestnuts up to 10,000 hours ^^. Metallization ^!

同 Other metal intermetallic ^! Or! ½Suru ^ displays the Nada page as “Yes”.

Table 2 (1): Comparative steel

Table 2 (2): Comparative steel

CRS: 650 ° C. Clear up to 10,000 B ^ 5 ^ ¾¾ Tearing 650 ° C, 100,000 ff says ϋ¾Cree ^

Presence of intercalation ^ /: ^ ₄ . 1 *) ₂ . (; 0 _{2 (} ^. ( ₂ —The intercalation ^ ¾ which has a fiber of syrup6, the clarity of the 顕, the same male and other intermetallics by electron microscopy ^ /) Is displayed.

Industrial applicability

The present invention has excellent high-temperature creep strength, contains Co, and has a high C temperature of 600 ° C. or more. Mo Co ^ W ,. (I) To provide a martensitic heat-resistant steel which does not generate an intermetallic compound having a composition of Fe.

Claims

1. In mass%,

c 0.0% 0.30%,

0.8% of Si 0.0%,

O

Mn 0.20-1.50%,

1

Cr 8.00 to 13.00%,

Mo 0.01 ~ 3.00%,

Contract

W 0.10-5.00%,

Co 0.05 ~ 6.00%,

V 0.002-0.800%, Nb 0.002-0.500%,

N 0.002 to 0.200%

Containing, in addition to

Ca: 0.0005-0.0050%,

Ba: 0.0003-0.0020%,

Mg: 0.0005-0.0050%,

&&: 0.00 ton 0.002%

Ce: 0.001 to 0.002%,

Y: 0.020%

Of Ca, Ba, Mg in the form of precipitate, La, Ce, Y in the form of precipitate or solid solution.

Ti: 0.002-0.500%,

Zr: 0.002-0.500%

One or two of the above alone or in combination,

P: 0.030% or less,

S: 0.010% or less, 0: 0.020% or less

High-strength heat-resistant steel with excellent intermetallic compound precipitation embrittlement resistance characterized by the fact that the balance consists of Fe and unavoidable impurities.

2. The composition according to claim 1, further comprising

Ni: 0.10-2.00%,

Cu: 0.10-2.00%

A high-strength ferritic heat-resistant steel having excellent intermetallic compound precipitation embrittlement characteristics, characterized by containing one or two of the following.

3. In addition to the component of claim 1 or 2,

B: 0.0005 to 0.010%

High-strength X-ray heat-resistant steel with excellent intermetallic compound precipitation embrittlement resistance characterized by containing.