JPH1161342A - High chromium ferritic steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide new chromium ferritic steel which has an improved high temp. creep strength in the temp. range of >=600 deg.C an equal to or higher toughness than existing low alloy steel, workability and weldability and is substituted for austenitic stainless steel. SOLUTION: This ferritic steel consists of, by weight, 0.03-0.12% C, 0.1-0.7% Si, 0.1-1.0% Mn, <=0.025% P, <=0.015% S, 8-13% Cr, 0.1-1.5% Mo, 0.1-3.5% W, 0.01-0.3% V, 0.01-0.2% Nb, 0.1-3% Co, 0.1-3% Cu, 0.1-1% Ni, 0.0005-0.01% B, 0.01-0.1% N, further, any of 0.01-0.5% Hf, 0.01-0.5% Zr, 0.01-1.0% Ta, or 0.01-3% Os and the balance Fe with inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a boiler for power generation,
The present invention relates to a high Cr ferritic steel excellent in high-temperature strength suitable for use as a high-temperature pressure-resistant member in fields such as turbines and chemical plants.

[0002]

2. Description of the Related Art Austenitic stainless steel, high Cr ferritic steel having a Cr content of 9 to 12%, 2 1 / 4Cr-1Mo steel (JIS) are used as high-temperature pressure-resistant members for boilers for power generation, chemical plants and nuclear power. There is a low Cr ferritic steel and a carbon steel represented by STBA24 (all alloy components in this specification are weight%). These are selected according to the use temperature, pressure, and use environment of the target member and in consideration of economic efficiency. Among them, 9-12% Cr ferrite steel is 1) less expensive than austenitic stainless steel.
It has excellent features such as 2) low coefficient of thermal expansion, 3) less likely to cause stress corrosion cracking, and 4) good thermal conductivity.
In addition, high-temperature corrosion,
Excellent in stress corrosion and high in high temperature strength. Therefore, it is attracting attention as a substitute for austenitic stainless steel.

[0003]

Therefore, the present invention provides a 60
A new high Cr that can significantly improve the high temperature creep strength in the temperature range of 0 ° C or higher, and has the same or higher performance as existing low alloy steels in toughness, workability and weldability, and can be replaced with austenitic stainless steel. It provides ferritic steel.

[0004]

Means for Solving the Problems As a result of intensive studies, the present inventors have provided the following high-ferritic steels having excellent high-temperature strength. (1) Carbon (C): 0.03 to 0.12%, silicon (S
i): 0.1 to 0.7%, manganese (Mn): 0.1 to
1.0%, phosphorus (P): ≤0.025%, sulfur (S): ≤0.015%, chromium (Cr): 8-13
%, Molybdenum (Mo): 0.1 to 1.5%, tungsten (W): 0.1 to 3.5%, vanadium (V):
0.01-0.3%, niobium (Nb): 0.01-0.
2%, cobalt (Co): 0.1 to 3%, copper (Cu):
0.1-3%, nickel (Ni): 0.1-1%, boron (B): 0.0005-0.01%, nitrogen (N):
0.01 to 0.1%, hafnium (Hf): 0.01 to
A high Cr ferritic steel containing 0.5%, with the balance being iron and unavoidable impurities. (2) carbon: 0.03 to 0.12%, silicon: 0.1 to
0.7%, manganese: 0.1 to 1.0%, phosphorus: ≦ 0.
025%, sulfur: ≤ 0.015%, chromium: 8 to 13
%, Molybdenum: 0.1 to 1.5%, tungsten:
0.1-3.5%, vanadium: 0.01-0.3%,
Niobium: 0.01-0.2%, Cobalt: 0.1-3
%, Copper: 0.1-3%, nickel: 0.1-1%, boron: 0.0005-0.01%, nitrogen: 0.01-0.
1%, zirconium: High Cr ferritic steel containing 0.01 to 0.5%, the balance being iron and unavoidable impurities. (3) carbon: 0.03 to 0.12%, silicon: 0.1 to
0.7%, manganese: 0.1 to 1.0%, phosphorus: ≦ 0.
025%, sulfur: ≤ 0.015%, chromium: 8 to 13
%, Molybdenum: 0.1 to 1.5%, tungsten:
0.1-3.5%, vanadium: 0.01-0.3%,
Niobium: 0.01-0.2%, Cobalt: 0.1-3
%, Copper: 0.1-3%, nickel: 0.1-1%, boron: 0.0005-0.01%, nitrogen: 0.01-0.
1%, tantalum: High Cr ferritic steel containing 0.01 to 1.0%, the balance being iron and unavoidable impurities. (4) carbon: 0.03 to 0.12%, silicon: 0.1 to
0.7%, manganese: 0.1 to 1.0%, phosphorus: ≦ 0.
025%, sulfur: ≤ 0.015%, chromium: 8 to 13
%, Molybdenum: 0.1 to 1.5%, tungsten:
0.1-3.5%, vanadium: 0.01-0.3%,
Niobium: 0.01-0.2%, Cobalt: 0.1-3
%, Copper: 0.1-3%, nickel: 0.1-1%, boron: 0.0005-0.01%, nitrogen: 0.01-0.
1%, osmium: High Cr ferritic steel containing 0.01 to 3%, the balance being iron and unavoidable impurities.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION A first preferred embodiment of the present invention is to add Co, which has an effect of suppressing the formation of δ-ferrite, by adding Hf, which has been rarely used as an additional element.
It is characterized by adding appropriate amounts of Cu and Ni.
C: 0.03 to 0.12%, Si: 0.1 to 0.7%,
Mn: 0.1 to 1.0%, P: ≤ 0.025%, S: ≤
0.015%, Cr: 8 to 13%, Mo: 0.1 to 1.
5%, W: 0.1-3.5%, V: 0.01-0.3
%, Nb: 0.01 to 0.2%, Co: 0.1 to 3%,
Cu: 0.1-3%, Ni: 0.1-1%, B: 0.0
005 to 0.01%, N: 0.01 to 0.1%, Hf:
The object is to provide a high Cr ferritic steel containing 0.01 to 0.5%, with the balance being iron and unavoidable impurities and having excellent high-temperature strength.

[0006] The action of each component in the steel of the present invention and the reasons for its limitation will be described below. C (carbon) is, together with N, Cr,
It combines with Fe, V, and Nb to form carbonitride and contributes to improvement in high-temperature strength. Further, it acts as an austenite-forming element and suppresses the formation of δ-ferrite. 0.03
%, Carbide precipitation is insufficient, and the amount of δ-ferrite increases, resulting in insufficient strength and toughness. Also,
If added in excess of 0.12%, excessive precipitation of carbides significantly hardens and reduces workability, and also deteriorates weldability, causing problems such as weld cracking when manufacturing pressure vessels and the like. Therefore, the component range is from 0.03 to
0.12%, preferably 0.05 to 0.11%.

Si (silicon) acts as a deoxidizer,
It is an element that enhances steam oxidation resistance, but 0.7%
If it exceeds, the toughness is significantly reduced, and is harmful to the strength. On the other hand, if the addition is less than 0.1%, the effect cannot be obtained. Therefore, the component range is 0.1-0.7%
It is.

[0008] Mn (manganese) is an element useful as a deoxidizing agent like Si. However, if it exceeds 1%, the steel is hardened and the workability is impaired. On the other hand, if the addition is less than 0.1%, the effect cannot be obtained. Therefore, its component range is
0.1 to 1%.

P (phosphorus) and S (sulfur) are elements that are harmful to toughness and workability. Even if a small amount of S is present, the grain boundary and Cr ₂ O ₃ scale film become unstable, and the strength and toughness are increased. It is also preferable that the number is as small as possible even within the above-mentioned allowable range, because it causes deterioration of workability. As the inevitable contents, the upper limit is 0.025% for P and 0.015 for S.
%.

[0010] Cr (chromium) combines with C and N to form carbonitrides and contributes to the improvement of creep rupture strength, and improves the oxidation resistance and high temperature corrosion resistance by forming a solid solution in the matrix. In addition, it strengthens the matrix itself and contributes to improvement in creep strength. If the content is less than 8%, sufficient oxidation resistance and high-temperature corrosion resistance cannot be obtained, and if it exceeds 13%, δ-ferrite is easily formed and the strength and toughness are impaired. Therefore, the component range is 8 to 13%.

Mo (molybdenum), together with W, forms a solid solution in the parent phase and improves the creep strength. If Mo is added alone, about 3% can be added. However, when W is added in the scope of the present invention, W is more effective for improving the high-temperature strength, and Mo and W are added in large amounts. Then δ
-While ferrite is formed, an intermetallic compound called a Laves phase is formed during long-time use at high temperature, and creep ductility is reduced. Also, if less than 0.1% is added, the effect is not exhibited. Therefore, its component range is
0.1 to 1.5%, preferably 0.1 to 1.0%.

As described above, W (tungsten) forms a solid solution in the matrix and significantly improves the creep strength. However, when it is added in excess of 3.5%, δ-ferrite is easily formed. Also, if less than 0.1% is added, the effect is not exhibited. Therefore, the component range is from 0.1 to
It is 3.5%, preferably 1.5 to 3.0%.

V (vanadium) is, together with Nb, C,
Combines with N to form fine carbonitrides. These fine precipitates are effective for improving long-time creep strength at high temperatures. However, if it is less than 0.01%, a sufficient effect cannot be obtained, and if it exceeds 0.3%, the creep strength is rather deteriorated. Therefore, the component range is 0.01 to
0.3%, preferably 0.10 to 0.25%.

Nb (niobium) forms fine carbonitrides as described above and contributes to improvement in creep strength. Also,
This has the effect of suppressing the growth of austenite grains during the solution treatment. However, if the content is less than 0.01%, the above effects cannot be obtained. If the content exceeds 0.2%, undissolved NbC increases, and creep strength and toughness are impaired. Therefore, its component range is 0.01-0.2%, preferably 0.03%.
~ 0.1%.

Co (cobalt), like Cu and Ni, is an austenite stabilizing element and has an effect of suppressing the formation of δ-ferrite. In addition, there is an advantage that the Acl temperature is less reduced with respect to the addition amount than Ni and the tempering temperature can be set higher. Therefore, the amount of Co to be added is 0.1.
1-3%. If it is less than 0.1%, a sufficient effect cannot be obtained, and if it exceeds 3%, the creep strength is rather deteriorated.

Cu (copper) is an austenite stabilizing element, has an effect of suppressing the formation of δ-ferrite, and can be expected to strengthen solid solution and precipitation. However, a large amount of addition lowers the strength and hot workability. Regarding hot workability, workability can be improved by adding an appropriate amount of Ni. From the above, the component range of Cu is 0.1.
It is 1 to 3%, preferably 0.5 to 2.5%.

Ni (nickel) is an austenite stabilizing element, has an effect of suppressing the formation of δ-ferrite, and contributes to improvement of toughness.
%, The high temperature creep strength is impaired. Further, by setting the balance between Ni and Cu to be Ni ≧ 1/4 Cu in a weight ratio, it is possible to prevent cracking during hot working due to the large addition of Cu (when adding 1% or more of Cu). Therefore, considering the balance with Cu, the component range is:
It is 0.1 to 1%, preferably 0.1 to 0.7%.

B (boron) has an effect of improving hardenability by adding a very small amount and dispersing and stabilizing carbides. If less than 0.0005%, the effect is small,
If it exceeds 0.01%, workability is impaired. Therefore, the component range is 0.0005 to 0.01%, preferably 0.001 to 0.007%.

N (nitrogen) is, like C, Cr, Fe,
It combines with V, Nb, etc. to form carbonitride. 0.01%
If it is less than 0.1%, the effect is not obtained, and if it exceeds 0.1%, the carbonitride becomes coarse and the strength, toughness and workability are impaired. Therefore, the component range is 0.01 to 0.1%, preferably 0.02 to 0.07%.

Since Hf (hafnium) has a large misfit (degree of lattice distortion) with the Fe matrix and a large diffusion coefficient in Fe, the movement of dislocations occurs when Hf forms a solid solution in the Fe matrix. Inhibits and increases high temperature strength. Hf that does not form a solid solution combines with C and precipitates as carbide, thereby inhibiting dislocation movement. However, if it is less than 0.01%, the effect is not obtained, and if it exceeds 0.5%, an intermetallic compound is formed and the toughness is reduced. Therefore, the component range is 0.01 to 0.5%.

In a second preferred embodiment of the present invention, Zr, which has been rarely used as an additional element, is added,
Co, C having the effect of suppressing the formation of δ-ferrite
u and Ni are added in appropriate amounts,
C: 0.03 to 0.12%, Si: 0.1 to 0.7%,
Mn: 0.1 to 1.0%, P: ≤ 0.025%, S: ≤
0.015%, Cr: 8 to 13%, Mo: 0.1 to 1.
5%, W: 0.1-3.5%, V: 0.01-0.3
%, Nb: 0.01 to 0.2%, Co: 0.1 to 3%,
Cu: 0.1-3%, Ni: 0.1-1%, B: 0.0
005 to 0.01%, N: 0.01 to 0.1%, Zr:
The object is to provide a high Cr ferritic steel containing 0.01 to 0.5%, with the balance being iron and unavoidable impurities and having excellent high-temperature strength.

The action of each component of the steel of the present invention in the second embodiment and the reason for limiting the same will be described below. C, Si, Mn,
P, S, Cr, Mo, W, V, Nb, Co, Cu, N
i, B and N are the same as in the first embodiment.
Zr (zirconium) has a large misfit with the Fe matrix (degree of lattice distortion) and a large diffusion coefficient in Fe. Therefore, when Zr forms a solid solution in the Fe matrix, the dislocation motion is inhibited. Increases high temperature strength. In addition, Zr that does not form a solid solution combines with N and precipitates as nitride, thereby inhibiting dislocation movement. However, if it is less than 0.01%, the effect is not obtained, and if it is added in a large amount, an intermetallic compound is formed and the toughness is reduced.
%.

In a third preferred embodiment of the present invention, Ta, which has been rarely used as an additional element, is added,
Co, C having the effect of suppressing the formation of δ-ferrite
u and Ni are added in appropriate amounts,
C: 0.03 to 0.12%, Si: 0.1 to 0.7%,
Mn: 0.1 to 1.0%, P: ≤ 0.025%, S: ≤
0.015%, Cr: 8 to 13%, Mo: 0.1 to 1.
5%, W: 0.1-3.5%, V: 0.01-0.3
%, Nb: 0.01 to 0.2%, Co: 0.1 to 3%,
Cu: 0.1-3%, Ni: 0.1-1%, B: 0.0
005 to 0.01%, N: 0.01 to 0.1%, Ta:
The object is to provide a high Cr ferritic steel containing 0.01 to 1.0%, with the balance being iron and unavoidable impurities and having excellent high-temperature strength.

The action of each component of the steel of the present invention in the third embodiment and the reason for limiting the same will be described below. C, Si, Mn,
P, S, Cr, Mo, W, V, Nb, Co, Cu, N
i, B and N are the same as in the first embodiment.
Since Ta (tantalum) has a large misfit (degree of lattice distortion) with the Fe matrix and a large diffusion coefficient in Fe, when Ta forms a solid solution in the Fe matrix, it inhibits the movement of dislocations. Increases high temperature strength. However, if it is less than 0.01%, the effect is not obtained, and if it exceeds 1%, an intermetallic compound is generated and a carbide is easily formed. Therefore, the component range is 0.01-1.0%
It is.

In a fourth preferred embodiment of the present invention, Os, which has been rarely used as an additional element, is added.
Co, C having the effect of suppressing the formation of δ-ferrite
u and Ni are added in appropriate amounts,
C: 0.03 to 0.12%, Si: 0.1 to 0.7%,
Mn: 0.1 to 1.0%, P: ≤ 0.025%, S: ≤
0.015%, Cr: 8 to 13%, Mo: 0.1 to 1.
5%, W: 0.1-3.5%, V: 0.01-0.3
%, Nb: 0.01 to 0.2%, Co: 0.1 to 3%,
Cu: 0.1-3%, Ni: 0.1-1%, B: 0.0
005-0.01%, N: 0.01-0.1%, Os:
The purpose of the present invention is to provide a high Cr ferritic steel containing 0.01 to 3%, with the balance being iron and unavoidable impurities and having excellent high temperature strength.

The operation of each component of the steel of the present invention in the fourth embodiment and the reason for limiting the same will be described below. C, Si, Mn,
P, S, Cr, Mo, W, V, Nb, Co, Cu, N
i, B and N are the same as in the first embodiment.
Os (osmium) has a large misfit (degree of lattice distortion) with the Fe matrix and has a large diffusion coefficient in Fe. Therefore, when Hf forms a solid solution in the Fe matrix, the dislocation movement is inhibited. Increases high temperature strength. The Fe matrix has a wide solid solubility limit with respect to Os, and the high-temperature strength increases in proportion to the amount of addition, but the upper limit is set to 3% in view of economic efficiency. If the content is less than 0.01%, the effect is not obtained. Therefore, the component range is 0.01 to 3.0%.

The high Cr ferritic steel having excellent high-temperature strength according to the present invention comprises the above components and inevitable impurities and iron. The unavoidable impurities refer to those that are mixed in from the raw material in the steelmaking stage and cannot be removed even in refining, and specifically, Al, O, Sn, As, and Sb.
P <0.03, S <
0.03, Al <0.01, O <0.01, Sn <0.
01, As <0.01, and Sb <0.01.

[0028]

EXAMPLES Specific experimental examples will be described below.
The present invention is not limited to this. Tables 1 and 2 show the chemical component compositions of the materials subjected to the test, and Tables 3 and 4 show the results of the material property test. Example 1 In Table 1, A to D are comparative steels, and AA to AL are invention steels of Example 1. Steel A, Steel B and Steel C are fire STBA27 and fire STBA specified in the technical standards for thermal power plants for power generation, respectively.
No. 28 is a material equivalent to Fire SUS410J2TB, and D steel is a material equivalent to D20 standard X20CrMoV121. Each of these steels was melted in a 30 kg high frequency vacuum melting furnace, and the ingot was forged at 1150 to 950 ° C. A steel and B steel are 1050 ° C x 1 as normal heat treatment.
hr.A. After normalizing C (air cooling), 770 ℃ x 1h
r.A. C was tempered. C steel and D steel are 1100 ° C. × 1 hr · A. After normalizing C, 76
0 ° C. × 2 hr · A. C was tempered. The steel of the present invention is 1070 ° C. × 3 hr · A. After normalizing C, 7
80 ° C. × 2 hr · A. C was tempered.

For these test steels, a tensile test (JIS
Z 2241), a Charpy impact test (JIS Z 2242) and a creep rupture test (JIS Z 2272). The tensile test was performed at room temperature and 600 ° C, and the creep rupture test was performed at 600 ° C and 650 ° C.
A long-term test was performed at 10,000 ° C. and 700 ° C. for a maximum of about 10,000 hr, and creep rupture strength at 650 ° C. × 10 ₅ hr was determined. In the Charpy impact test, a ductile-brittle fracture transition temperature was determined in accordance with JIS Z 2202.

Table 3 shows the test results. As is clear from Table 3, the steel of the present invention shows higher values in both room temperature and 600 ° C in tensile strength and 0.2% proof stress than the comparative steel. Further, it can be seen that the creep rupture strength of the steel of the present invention is much better than the comparative steel. In addition, the ductility-brittle transition temperature of the steel of the present invention shows a value equivalent to that of the existing steel as a comparative steel, and it can be seen that there is no practical problem. As described above, the steel of the present invention has a high-temperature strength that greatly exceeds the conventional steel,
This material has the same toughness as conventional steel.

Example 2 In the same manner as in Example 1, the steel 2 of the present invention (reference numerals BA to B)
L), a tensile strength test, a Charpy impact test and a creep rupture test were performed to evaluate the material properties. Table 3 shows the test results. As is clear from Table 3, the steel of the present invention shows higher values of the tensile strength and 0.2% proof stress at room temperature and 600 ° C. than the comparative steel at room temperature and 600 ° C., similarly to the invention steels of Examples 1 (reference symbols AA to AL). I have. Further, it can be seen that the creep rupture strength of the steel of the present invention is much better than the comparative steel. Also,
The ductility-brittle transition temperature of the steel of the present invention shows the same value as that of the existing steel as the comparative steel, and it can be seen that there is no practical problem.

As described above, the steel of the present invention, like the steel of the first embodiment, is a material having a high-temperature strength that is significantly higher than that of the conventional steel and a toughness equivalent to that of the conventional steel. Zr, which is one of the characteristic additional elements of the steel of the present invention, is cheaper than Hf added in Example 1, and is therefore more economically advantageous than the invention steel of Example 1.

Example 3 According to the same method as in Example 1, the steel 3 of the present invention (reference characters CA to C)
L), a tensile strength test, a Charpy impact test and a creep rupture test were performed to evaluate the material properties. Table 2 shows the chemical composition of the material, and Table 4 shows the test results. As is clear from Table 4, the steel of the present invention is the steel of the first embodiment (symbol AA).
-AL), the tensile strength and 0.2% proof stress of both room temperature and 600 ° C show higher values than the comparative steel.
Further, it can be seen that the creep rupture strength of the steel of the present invention is much better than the comparative steel. Further, the ductility-brittle transition temperature of the steel of the present invention shows a value equivalent to that of the existing steel as a comparative steel, and it can be seen that there is no practical problem. Further, the steels of the present invention were prepared in Example 1 (Hf-added steel) and Example 2 (Zr
Since the solid solubility limit of Fe in the special additive element (Ta) is wider than that of the inventive steel of (added steel), it can be added in a large amount, and therefore has a high creep rupture strength.

As described above, the steel of the present invention is a material having a high-temperature strength that is significantly higher than that of the conventional steel and a toughness equivalent to that of the conventional steel, and has a higher temperature than the steels of the invention shown in Examples 1 and 2. It is a material with excellent strength. Since the material thickness can be made thinner because it is superior in the high-temperature strength to the invention steels of Examples 1 and 2, the thermal stress accompanying the start and stop of the plant can be reduced, the occurrence of damage is suppressed, and the reliability of the plant is improved. Contribute.

Example 4 According to the same method as in Example 1, the steel 4 of the present invention (reference numerals DA to D)
L), a tensile strength test, a Charpy impact test and a creep rupture test were performed to evaluate the material properties. Table 2 shows the chemical composition of the material, and Table 4 shows the test results. As is clear from Table 4, the steel of the present invention is the steel of the first embodiment (symbol AA).
-AL), the tensile strength and 0.2% proof stress of both room temperature and 600 ° C show higher values than the comparative steel.
Further, it can be seen that the creep rupture strength of the steel of the present invention is much better than the comparative steel. In addition, the ductility-brittle transition temperature of the steel of the present invention shows a value equivalent to that of the existing steel as a comparative steel, and it can be seen that there is no practical problem. Further, the steel of the present invention has a solid solubility limit to Fe of a special additive element (Os) more than the inventive steels of Example 1 (Hf-added steel), Example 2 (Zr-added steel) and Example 3 (Ta-added steel). Has a high creep rupture strength because of its large content.

As described above, the steel according to the present invention is a material having a high temperature strength which is significantly higher than that of the conventional steel, and a toughness equivalent to that of the conventional steel. Is also a material excellent in high-temperature strength. Example 1 of the steel of the present invention
Since the high-temperature strength is superior to the invention steels of Nos. 1 to 3, the thickness of the material can be reduced, so that the thermal stress accompanying the start / stop of the plant can be reduced, the occurrence of damage is suppressed beforehand, and the reliability of the plant is further improved. .

[0037]

As described above, the steel of the present invention forms a stable structure at a high temperature by the components shown in Table 1, and the conventional high Cr
An object of the present invention is to provide a ferritic steel having significantly improved creep strength at a high temperature of 600 ° C. or higher where ferrite steel was difficult to use. The steel of the present invention is an austenitic steel such as SUS347HTB, SUS321HTB and SU.
It has a creep strength equal to or higher than that of S316HTB. The steel of the present invention is a material having both toughness, workability, and economy, which are the advantages of ferritic steel, as a high-temperature pressure-resistant member used in industrial fields such as boilers, chemical industries, and nuclear power. , Plates and other various shapes of forged products.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

[0041]

[Table 4]

Claims (4)

[Claims] 1% by weight of carbon: 0.03 to 0.12
%, Silicon: 0.1 to 0.7%, manganese: 0.1 to
1.0%, phosphorus: ≤0.025%, sulfur: ≤0.01
5%, chromium: 8 to 13%, molybdenum: 0.1 to 1.
5%, tungsten: 0.1 to 3.5%, vanadium:
0.01-0.3%, niobium: 0.01-0.2%, cobalt: 0.1-3%, copper: 0.1-3%, nickel:
0.1-1%, boron: 0.0005-0.01%, nitrogen: 0.01-0.1%, hafnium: 0.01-0.
High Cr ferritic steel containing 5%, with the balance being iron and unavoidable impurities. 2. Carbon: 0.03-0.12% by weight
%, Silicon: 0.1 to 0.7%, manganese: 0.1 to
1.0%, phosphorus: ≤0.025%, sulfur: ≤0.01
5%, chromium: 8 to 13%, molybdenum: 0.1 to 1.
5%, tungsten: 0.1 to 3.5%, vanadium:
0.01-0.3%, niobium: 0.01-0.2%, cobalt: 0.1-3%, copper: 0.1-3%, nickel:
0.1-1%, boron: 0.0005-0.01%, nitrogen: 0.01-0.1%, zirconium: 0.01-
A high Cr ferritic steel containing 0.5%, with the balance being iron and unavoidable impurities. 3. Carbon by weight: 0.03-0.12
%, Silicon: 0.1 to 0.7%, manganese: 0.1 to
1.0%, phosphorus: ≤0.025%, sulfur: ≤0.01
5%, chromium: 8 to 13%, molybdenum: 0.1 to 1.
5%, tungsten: 0.1 to 3.5%, vanadium:
0.01-0.3%, niobium: 0.01-0.2%, cobalt: 0.1-3%, copper: 0.1-3%, nickel:
0.1-1%, boron: 0.0005-0.01%, nitrogen: 0.01-0.1%, tantalum: 0.01-1.0
%, The balance being iron and unavoidable impurities
r Ferrite steel. 4. Carbon in weight%: 0.03-0.12
%, Silicon: 0.1 to 0.7%, manganese: 0.1 to
1.0%, phosphorus: ≤0.025%, sulfur: ≤0.01
5%, chromium: 8 to 13%, molybdenum: 0.1 to 1.
5%, tungsten: 0.1 to 3.5%, vanadium:
0.01-0.3%, niobium: 0.01-0.2%, cobalt: 0.1-3%, copper: 0.1-3%, nickel:
0.1-1%, boron: 0.0005-0.01%, nitrogen: 0.01-0.1%, osmium: 0.01-3
%, The balance being iron and unavoidable impurities
r Ferrite steel.