JPH03236448A - Cr-ni series heat resistant steel - Google Patents

Abstract

PURPOSE:To manufacture a heat resistant steel having high creep rupture strength and oxidation resistance at a high temp. as well as a heat resistant steel combining high temp. strength and economicity by adding specified elements to a Cr-Ni series heat resistant steel. CONSTITUTION:The compsn. of a Cr-Ni series heat resistant steel is formed into a one contg., by weight, 0.2 to 0.6% C, <2% Si, <2% Mn, 20 to 35% Cr, 15 to 50% Ni, 0.05 to 0.50% Zr, 0.05 to 0.30% Ti, 0.2 to 2.0% Nb and 0.5 to 10% Mo or furthermore contg. specified amounts of at least one or more kinds among W, V, N, Al and B and the balance Fe, by which the Cr-Ni series heat resistant steel excellent in creep rupture strength and oxidation resistance at a high temp. can be manufactured. Or, this steel is formed into a one contg. 0.2 to 0.6% C, <2% Si, 5 to 20% Mn, 20 to 35% Cr, 5 to 15% Ni, 0.1 to 2.0% V and 0.03 to 0.30% N as well as satisfying 15 to 35%(Mn+Ni) or furthermore contg. specified amounts of at least one kind among Zr, Ti, Nb, Mo, W, Al and B, by which the Cr-Ni series heat resistant steel having high high temp. strength and excellent in economicity can be manufactured.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention provides a Cr-Ni heat-resistant steel that has high creep rupture strength (high temperature strength) at high temperatures and excellent oxidation resistance; The present invention also relates to a Cr-Ni heat-resistant steel having high high-temperature strength and excellent economic efficiency.

(Prior art) Reformer reaction tubes and cracking furnace reaction tubes used in the production of petroleum refining hydrogen, ammonia, methanol, ethylene, etc. in petrochemical plants, and reformer reaction tubes used in fuel cell plants to produce hydrogen for fuel cells. ASTM standard HK40 (JIS 25CH22
25Cr2ONi steel (equivalent to
Heat-resistant steel such as 25Cr-35Ni steel (corresponding to IS: 5CH24) is widely used. These heat-resistant steels are characterized by particularly excellent heat resistance.

(Problems to be Solved by the Invention) By the way, the above-mentioned reaction tubes are manufactured by centrifugal casting, but because the creep rupture strength of heat-resistant steel is low, they usually have to have a thick-walled structure. However, in this case, thermal stress increases when the temperature changes, and the thermal fatigue damage described above when starting and stopping the use of the reaction tube increases. For this reason, although the yield of the above-mentioned reaction tube could be improved by increasing the operating temperature, it was not possible to raise the temperature to a level that would improve the yield. Further, the thick wall structure is not preferable from the economic point of view of improving thermal efficiency, that is, reducing fuel consumption due to increase in operating temperature.

Therefore, as a steel that can eliminate the above-mentioned drawbacks to some extent, 0
．． 3C-24Cr-24Ni-1,5Nb-balance Fe composition and 0.4C-25Cr-35Ni-1,5Nb
- A heat-resistant steel having a composition with the remainder being Fe has been developed. These heat-resistant steels can be made into thin-walled structures that meet the requirements for high creep strength at high temperatures to some extent.

However, demands for higher temperatures during operation and reductions in fuel consumption have become even higher in recent years. For this reason, heat-resistant steels have been proposed in which the above-mentioned heat-resistant steels containing niobium are further added with one or more of the elements titanium, aluminum, nitrogen, and boron to enhance creep rupture strength. However, when operations are carried out at high temperatures, oxidation that causes scale to form on the surface of cast products such as reaction tubes is promoted. When this oxide scale flakes off, it causes a loss of the cast product and further oxide scale is formed in the area where it flakes off, creating a vicious cycle.Although the above-mentioned heat-resistant steels all have sufficient resistance to this oxidation, There wasn't.

Further, nickel is not only a heat-resistant element but also has the effect of imparting toughness to steel, but on the other hand, it has the drawback of being expensive. Therefore, if the same creep rupture strength can be achieved with steel, the lower the nickel content, the lower the cost of casting.

The present invention was made in view of the above circumstances, and consists of a Cr-Ni heat-resistant steel that achieves high creep rupture strength at high temperatures and has excellent oxidation resistance, and a Cr-Ni heat-resistant steel that has both high-temperature strength and economic efficiency. -An object of the present invention is to provide a Ni-based heat-resistant steel.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention first produces a heat-resistant steel having high creep rupture strength and oxidation resistance at high temperatures, and uses zero carbon. 2-0.6% by weight, silicon up to 2.0% by weight, manganese up to 2.0% by weight, chromium 20-35%
15-50% by weight of nickel, 0.05-0.50% of zirconium, 0.05-0.3% of titanium by weight.
0% by weight, 0.0% niobium. 2-2.0% by weight and 0.0% molybdenum. Provided is a Cr-Ni heat-resistant steel containing 5 to 10.0% by weight and the balance containing iron.

Further, in order to achieve this object, the present invention further includes 0.5 to 10.0% by weight of tungsten in addition to the above composition.
1.00% by weight vanadium, 0.03-0.20% nitrogen, 0.0005-0.1000% aluminum and o,oo.

A Cr-Ni heat-resistant steel containing at least one member selected from the group consisting of 5 to 0.1000% by weight of boron is also provided.

In addition, the present invention is a Cr-Ni heat-resistant steel that has 0.0% carbon content and achieves high creep rupture strength at high temperatures and economic efficiency at low cost. 2-0.6% by weight, silicon up to 2.0% by weight, manganese 5-20% by weight, chromium 20-20% by weight
35% by weight, nickel 5-15% by weight, vanadium 0. 1-2.0% by weight and 0.03-0.3% nitrogen
The total of manganese and nickel is 15 to 35, including 0% by weight.
% by weight, and the remainder contains iron.

Further, in order to achieve the same objective, the present invention further provides 0.05 to 0.50% by weight of zirconium to the above composition.
~0.30 wt% titanium, 0°2~2.0 wt% niobium, 0.5~10.0 wt% molybdenum, 0.5~
10.0% by weight tungsten, 0.0005-0.1
000% by weight aluminum and 0.0005-0.
Provided is a Cr-Ni heat-resistant steel containing 1000% by weight of at least one member selected from the group consisting of boron.

(Function) In both the Cr-Ni heat-resistant steels according to the first and second inventions, in addition to carbon, nickel, chromium, and manganese are dissolved in iron, so that they form an austenitic structure even at room temperature, and are heat-resistant elements. It exhibits good heat resistance because it is made of nickel, silicon, chromium, and manganese. In the heat-resistant steel according to the first invention, zirconium, titanium, niobium, and molybdenum form carbides and precipitate finely and uniformly in the matrix, increasing the creep rupture strength of the heat-resistant steel at high temperatures. In addition, molybdenum that cannot be completely precipitated becomes a solid solution in the matrix, and zirconium strengthens the strength of grain boundaries and improves ductility, thereby contributing to increasing the creep strength of heat-resistant steel.

Furthermore, zirconium was found to have the effect of preventing oxide scale from peeling off. Therefore, loss of steel material due to peeling off of oxide scale is also suppressed.

In addition to the above elements, tungsten, vanadium,
In the heat-resistant steel according to the second invention containing nitrogen, aluminum, and boron, tungsten and vanadium form carbides with the above-mentioned zirconium, titanium, niobium, and molybdenum, and precipitate finely and uniformly in the matrix. Therefore, the same effect as described above increases the crimp rupture strength of the heat-resistant steel at high temperatures. In addition, nitrogen partially replaces carbon in the metal carbide mentioned above and turns the carbide into fine carbonitride, thereby partially increasing the creep rupture strength.

Furthermore, tungsten and nitrogen that cannot be precipitated become solid solutions in the matrix, and boron strengthens the strength of grain boundaries and improves ductility, each of which contributes to increasing the creep strength of heat-resistant steel. Also, like zirconium mentioned above, boron strengthens the strength of grain boundaries and improves ductility, but
Aluminum forms a compound with gas components such as nitrogen at the grain boundaries, and by fixing (degassing) the gas components at the grain boundaries, it suppresses brittleness caused by gases and helps strengthen the grain boundaries of boron and zirconium. .

In addition, the third invention contains only 5 to 15% by weight of expensive nickel, and also contains carbon, silicon, manganese, chromium,
Provides heat-resistant steel containing vanadium and nitrogen. In this heat-resistant steel, manganese partially replaces the function of nickel to form an austenitic structure, and coarse condensation of metal carbides that may occur due to the reduction of nickel is suppressed by vanadium and nitrogen. Therefore, this heat-resistant steel can achieve both high-temperature strength and low cost at the same time.

Furthermore, the fourth invention provides a heat-resistant steel that achieves the common objectives of high-temperature strength and low cost, including at least one of zirconium, titanium, niobium, molybdenum, tungsten, aluminum, and boron in addition to the above-mentioned components. We provide heat-resistant steel including All of these elements contribute to increasing creep strength, thereby realizing a heat-resistant steel with high high-temperature strength at a low cost.

The relationship between the properties and constituent elements of each heat-resistant steel of the present invention will be explained in detail below.

Each of the Cr-Ni heat-resistant steels of the present invention has an austenitic structure, but in the case of the heat-resistant steels according to the first and second inventions that achieve high-temperature strength and oxidation resistance, the heat-resistant steels according to the first invention is at least 0°2 to 0.0° carbon. 6% by weight, silicon up to 2.0% by weight, manganese 2. 0% by weight or less,
20-35% by weight of chromium, 15-50% by weight of nickel, 0.05-0.50% by weight of zirconium, 0.105-0.30% by weight of titanium, 0.2-2.0% by weight of niobium.
% by weight and 0.5-10.0% by weight of molybdenum. Moreover, the heat-resistant steel according to the second invention further has a temperature of 0.5 to 10
．． 0 wt% tungsten, 0.05-1.00 wt%
of vanadium, 0.03-0.20% by weight of nitrogen, 0.
0005-0.1000% by weight aluminum and 0
．． It can contain at least one member selected from the group consisting of boron in an amount of 0.0005 to 0.1000% by weight. Therefore, the reason for including the above-mentioned elements and the significance of the numerical ranges will be explained below. In addition, in the following, all percentages indicate weight percentages.

Carbon, along with chromium and nickel, is a component that stabilizes the austenitic structure. Then, it forms carbides with other metal elements and finely precipitates in the matrix, increasing creep rupture strength at high temperatures. It also has the effect of improving swirling properties during casting. In order to exhibit this effect, 0. 2% or more is required. However, if it exceeds 0.6%, this effect will be saturated and the toughness will also decrease.
The content should be 0.2 to 0.6%.

When obtaining iron by reducing iron oxide FeO, silicon is added to remove residual oxygen, improve eddy current properties, and prevent carburization (reducing toughness).
2. If added in excess, it may deteriorate weldability or cause harmful σ phase (a solid solution of a brittle non-magnetic intermetallic compound mainly composed of FeCr) to occur when used at high temperatures.
Keep it below 0%.

Manganese is used as a deoxidizing agent during melting and to fix sulfur contained in preparations used during steelmaking to remove the adverse effects of brittleness caused by each gas component, but if added in excess, Oxidation resistance (oxidation roughens the finished surface) deteriorates.

Therefore, the amount added is limited to 2.0% or less.

Chromium precipitates carbides and increases high-temperature strength,
It is necessary to improve carburization resistance and oxidation resistance at high temperatures, but for members used at temperatures exceeding 10,000C, the effect will not be exhibited unless it is 20% or more.

However, if a large amount is added, σ phase will be generated during long-term use at high temperatures, resulting in a decrease in strength and toughness, so the amount added should be 20 to 35%.

Nickel is a component that stabilizes the austenite structure, improves oxidation resistance and carburization resistance, and also has the property of preventing crystal grain growth and increasing high-temperature strength. This effect is 1
It is noticeable when the amount is 5% or more, but if it is added in large quantities, the effect becomes saturated and it is not preferable from an economic point of view.

Below, niobium, zirconium, titanium, and molybdenum, which are characteristics of the present invention, will be explained.

First, niobium forms fine carbides, which are uniformly dispersed and precipitated in the matrix, increasing the crimp strength of heat-resistant steel. It also contributes to improving carburization resistance. In order to exhibit such an effect, a content of 0°2% or more is required, but if added in a large amount, weldability deteriorates and toughness also decreases. Therefore, the amount added should be 0.2 to 2.0%.

Titanium increases the creep strength of heat-resistant steel by uniformly dispersing and precipitating fine carbides in the matrix. In order to exhibit this effect, titanium must be present in an amount of 0.05% or more; however, adding a large amount of titanium increases oxide-based and sulfide-based nonmetallic inclusions and reduces strength. Therefore, the amount added should be 0.05 to 0.30%.

Zirconium strengthens grain boundaries, improves ductility, and evenly disperses and precipitates fine carbides in the matrix, increasing the creep strength of heat-resistant steel. It also prevents the peeling of oxide scales and improves peelability of steel materials. Breaking the vicious cycle of loss and monoxide. In order to exhibit this effect, zirconium needs to be present in an amount of 0.05% or more; however, adding a large amount will increase the number of oxide-based and sulfide-based nonmetallic inclusions, while also increasing the amount of niobium and titanium fine carbides. In order to reduce the precipitated material of
It causes a decrease in toughness and creep rupture strength. Therefore, the amount added should be 0.05 to 0.50%.

Molybdenum uniformly disperses and precipitates fine carbides in the matrix together with the above three elements, and the remaining part that cannot be precipitated is also dissolved in the matrix to improve high-temperature strength. In order to exhibit this effect, molybdenum must be at least 0. It is necessary to add 5% or more, but if added in a large amount, δ-ferrite is generated and the strength is reduced.

Therefore, the amount added should be 0.5 to 10.0%.

By the way, the second invention provides a Cr-Ni heat-resistant steel that can further contain tungsten, vanadium, boron, nitrogen, and aluminum in addition to the above-mentioned composition; The reason for adding elements and the significance of the amount added will be explained.

First, like molybdenum, tungsten uniformly disperses and precipitates fine carbides in the matrix, and the remainder is dissolved in the matrix to improve high-temperature strength. For this purpose, at least 0.5% or more of tungsten is required, but if added in a large amount, δ-ferrite is generated and the toughness is reduced. Therefore, the amount of tungsten added is 0. 5 to 10.0%.

Vanadium is also an element that uniformly disperses and precipitates fine carbides in the matrix, improving high-temperature strength. For this purpose, at least 0.05% of vanadium is required, but if added in a large amount, δ-ferrite is generated and the toughness is reduced. Therefore, the amount added is 0.05 to 1
．． 00%.

Like the aforementioned zirconium, boron strengthens grain boundaries, improves ductility, and increases creep strength. In order to exhibit this effect, 0.0005% or more is required, but 0.1
If it exceeds 000%, the effect is saturated. Therefore, the amount added is 0.0005 to 100%.

Nitrogen partially replaces carbon in the carbides of the metal elements mentioned above to form carbonitrides, contributing to improvement of high-temperature strength. Nitrogen is also an element that promotes austenitization and also plays a role in preventing the formation of δ-ferrite. This effect is 0.0
This can be obtained by containing 3% or more, but if it is contained in a large amount, the toughness is significantly reduced. Therefore, the content should be 0.03 to 0.20%.

Aluminum fixes grain boundary gas components and effectively exhibits the grain boundary strengthening effect of boron and zirconium described above. For this purpose, the content must be 0.0005% or more, but if the content is too large, the strength will decrease due to grain boundary segregation.

Therefore, the aluminum content is between 0.0005 and 0.0.
Set it to 1000%.

Further, the third and fourth inventions provide a heat-resistant steel that simultaneously achieves creep strength and low cost by reducing the Ni content. That is, the heat-resistant steel according to the third invention contains at least 0.0% carbon. 2-0.6% by weight, silicon up to 2.0% by weight, manganese 5-20% by weight, chromium 20-20% by weight
35% by weight, nickel 5-15% by weight, vanadium 0. 1-2.0% by weight and 0.03-0.3% nitrogen
Contains 0% by weight. Moreover, the heat-resistant steel according to the fourth invention further includes 0.05 to 0.50% by weight of zirconium, and 0.05 to 0.50% by weight of zirconium.
0.30% by weight titanium, 0.2~2゜0% by weight niobium, 0.5~10.0% by weight molybdenum 0.0005
~0.1000 wt% aluminum and 0.000
It can contain at least one kind selected from the group consisting of boron in an amount of 5 to 0.1000% by weight. Therefore, the reasons for including the above-mentioned elements and the significance of the numerical ranges will be explained below, without overlapping with the previous description.

As mentioned above, nickel is a component that stabilizes the austenite structure, and also increases oxidation resistance and carburization resistance.
Furthermore, it has the property of preventing crystal grain growth and increasing high-temperature strength. This effect can be achieved even at 15% or less when vanadium and nitrogen are present in predetermined amounts as described below. Since nickel is very effective and causes an increase in manufacturing costs, the nickel content in this heat-resistant steel was limited to 5 to 15%.

In the third and fourth inventions, manganese is required in an amount of 5% or more in order to replace the stabilizing function of the austenite structure played by nickel. However, if it exceeds 20%, the agglomeration of precipitated carbides becomes coarse during high-temperature use, resulting in a decrease in strength.

Therefore, the content should be 5 to 20%.

By the way, in addition to limiting the content of each of nickel and manganese, the total content of nickel and manganese is set to 15% or more from the viewpoint of stabilizing the austenite structure.

However, if this content becomes too high, not only will the improvement effect of nickel on high temperature strength, oxidation resistance, and carburization resistance be saturated, but it will also go against the purpose of improving economic efficiency. Therefore, the total content should be 15 to 35%.

As mentioned above, vanadium is an element that uniformly disperses and precipitates fine carbides in the matrix and improves high-temperature strength. In order to suppress this, the decrease in nickel is compensated for and the creep strength is strengthened. For this purpose 0
．． It is necessary to add 1% or more, but if it is too much, δ
- Produces ferrite and reduces toughness. Therefore,
The amount added is 0.1 to 2.0%.

As mentioned earlier, nitrogen partially replaces carbon in carbides of metal elements to form carbonitrides, but at this time, like vanadium, it suppresses the agglomeration and coarsening of M23C6 type metal carbides. do. Therefore, this nitrogen also compensates for the decrease in nickel and contributes to improving high-temperature strength. This effect can be obtained by containing 0.03% or more, but if it is contained in a large amount, the toughness is significantly reduced. Therefore, the content should be 0.03 to 0.30%.

(Example) First, the results of testing the creep strength and oxidation resistance of heat-resistant steels having both high temperature strength and oxidation resistance according to the first and second inventions will be shown below.

First, Table 1 shows the composition of the heat-resistant steel used as a sample.

space below c] Here, the heat-resistant steel according to the embodiments of the first and second inventions is referred to as 19
I used seeds. In addition, in order to compare and contrast with the heat-resistant steel according to Examples, Comparative Examples 1 and 2 are heat-resistant steels that do not contain any of the niobium, zirconium, titanium, and molybdenum, as well as tungsten, vanadium, nitrogen, aluminum, and boron, which are the characteristics of the present invention. (Comparative Example 1 corresponds to HK40, Comparative Example 2 corresponds to HP), Comparative Example 3 uses heat-resistant steel that further contains niobium in HP, and Comparative Examples 4 to 7 use zirconium, titanium, niobium, and molybdenum, respectively. Heat-resistant steels were used, each containing a quantity outside the range of the present invention.

These heat-resistant steels are 200mm x 30Qm after normal melting.
Cast into mx20mm plate materials, JIS Z-
Parallel part diameter 6 discs φ, gauge distance 30 according to 2272
A test piece of mm was taken.

Then, for each test piece, 3 kg at a temperature of 1050°C
7 kg under stress of f/+nm+2 and temperature of 900°C
A creep rupture test was conducted under two conditions of a stress of 1/mm2, and the time to break and elongation at break were measured.

On the other hand, in the oxidation resistance test,
A test plate of m x 20 mm x 2 mm was cut out, and the test plate was held at a temperature of 1100°C for 1 hour, and then left in the atmosphere and cooled 30 times.

Thereafter, the weight of this test plate was measured, and the amount of weight loss per unit area (oxidation loss) due to peeling off of the oxidized skeleton was determined. The results are shown in Table 2.

[Margin below]

As can be seen from Table 2, the elongation at break of the heat-resistant steels according to the examples of the first and second inventions is approximately the same as that of the heat-resistant steels according to the comparative example under both conditions; All times are significantly longer (2 to 9 times). Among the heat-resistant steels according to this example, those containing any one of W1, N, AI, and B in addition to Zr, Ti, Nb, and MO (Examples 5 to 14) are The creep rupture time is longer than those containing no (Examples 1 to 4).

The high-temperature strength strengthening effect of the five elements W1, N5Al, and B was demonstrated by two types of elements (Examples 15 to 17) and 5.
The results are higher in the order of those containing all types (Examples 18 to 19).

Regarding oxidation resistance, the heat-resistant steels according to the embodiments of the first and second inventions have less oxidation loss under both conditions, especially compared to comparative examples that do not contain zirconium (comparative examples 1 to 4). ing. This tendency is 900°C・7kg1/m
This is noticeable under m2 conditions.

Next, regarding the heat-resistant steel that achieves high-temperature strength and low cost according to the third and fourth inventions, test pieces were taken according to the same procedure as explained in Table 2, and creep rupture tests were conducted under the same conditions. Ta. The composition of the sample is shown in Table 3, and the results of the creep rupture test are shown in Table 4.

[Margin below]

Comparative Examples 1 to 3 are the same as in Tables 1 and 2. The sample according to this example was heated at 1050°C' 3 kgl
/mm2 and 900°C/7 kgf/mm2, both exhibited a rupture time that was 2 to 7 times longer than that of the comparative example. Also, V, l!, which is a feature of the third invention! : In addition to N, Zr and Ti.

Those containing any one of Nb, Mo, W, A 1 and B (Examples 21 to 27), those containing two or more types (Examples 28 to 31), and those containing all six types (Example 3)
2) (corresponding to the fourth invention), Z r, T i in this order
, NbSMo, W, AI and B. The creep rupture time is longer than that of the sample containing neither I nor B (Example 20).

Furthermore, since the heat-resistant steel of this example has a low Ni content of 1% or less, it was possible to significantly reduce the manufacturing cost compared to the heat-resistant steel of the comparative example.

〔Effect of the invention〕

As explained above, in the Cr-Ni heat-resistant steel according to the first invention, zirconium, titanium, niobium, and molybdenum form carbides and precipitate finely and uniformly in the matrix, causing creep rupture of the heat-resistant steel at high temperatures. Increase strength. In addition, molybdenum that cannot be completely precipitated becomes a solid solution in the matrix, and zirconium strengthens the strength of grain boundaries and improves ductility, thereby contributing to increasing the creep strength of heat-resistant steel.

Furthermore, zirconium was found to have the effect of preventing oxide scale from peeling off. Therefore, loss of steel material due to peeling off of oxide scale is also suppressed.

In addition to the above elements, tungsten, vanadium,
In the heat-resistant steel according to the second invention, which contains nitrogen, aluminum, and boron, tungsten and vanadium form carbides or carbonitrides together with the above-mentioned zirconium, titanium, niobium, and molybdenum to precipitate finely and uniformly, increasing high-temperature strength. .

A third invention provides a heat-resistant steel that contains only 5 to 15% by weight of expensive nickel and also contains carbon, silicon, manganese, chromium, vanadium, and nitrogen. In this heat-resistant steel, manganese partially replaces the function of nickel to form an austenitic structure, and the coarse condensation of metal carbides that may occur due to the reduction of nickel
Inhibited by vanadium and nitrogen. Therefore, this heat-resistant steel can achieve both high-temperature strength and low cost at the same time.

Furthermore, the fourth invention provides a heat-resistant steel that achieves the common objectives of high-temperature strength and low cost, including at least one of zirconium, titanium, niobium, molybdenum, tungsten, aluminum, and boron in addition to the above-mentioned components. We provide heat-resistant steel including All of these elements contribute to increasing creep strength, thereby realizing a heat-resistant steel with high high-temperature strength at a low cost.

Claims (1)

[Claims] 1. 0.2 to 0.6% by weight of carbon, 2.0% or less of silicon, 2.0% or less of manganese, and 20 to 20% of chromium.
35% by weight, 15-50% by weight of nickel, 0.05-0.50% by weight of zirconium, 0.05-0% by weight of titanium.
．． A Cr-Ni heat-resistant steel containing 30% by weight, 0.2 to 2.0% by weight of niobium, 0.5 to 10.0% by weight of molybdenum, and the balance containing iron. 2. 0.2 to 0.6% by weight of carbon, 2.0% or less of silicon, 2.0% or less of manganese, 20 to 20% of chromium
35% by weight, 15-50% by weight of nickel, 0.05-0.50% by weight of zirconium, 0.05-0% by weight of titanium.
．． 30 wt%, 0.2-2.0 wt% niobium and 0.5-10.0 wt% molybdenum, and 0.5-2.0 wt%
10.0% by weight tungsten, 0.05-1.00% by weight vanadium, 0.03-0.20% by weight nitrogen,
A Cr-Ni heat-resistant steel containing at least one member selected from the group consisting of 0.0005 to 0.1000% by weight of aluminum and 0.0005 to 0.1000% by weight of boron, and the balance containing iron. 3. Carbon 0.2-0.6% by weight, silicon 2.0% by weight or less, manganese 5-20% by weight, chromium 20-3%
5% by weight, 5-15% by weight of nickel, 0% of vanadium
．． A Cr-Ni heat-resistant steel containing 1 to 2.0% by weight, 0.03 to 0.30% by weight of nitrogen, a total of 15 to 35% by weight of manganese and nickel, and the balance containing iron. 4. Carbon 0.2-0.6% by weight, silicon 2.0% by weight or less, manganese 5-20% by weight, chromium 20-3%
5% by weight, 5-15% by weight of nickel, 0% of vanadium
．． The total of manganese and nickel is 15-35% by weight, including 1-2.0% by weight and 0.03-0.30% by weight of nitrogen, and 0.05-0.50% by weight of zirconium, 0. .05-0.30% by weight titanium, 0.2
~2.0 wt% niobium, 0.5-10.0 wt% molybdenum, 0.5-10.0 wt% tungsten, 0
．． A Cr-Ni heat-resistant steel containing at least one member selected from the group consisting of 0.0005 to 0.1000% by weight of aluminum and 0.0005 to 0.1000% by weight of boron, and the balance being iron.