JP2003041351A - High chromium steel and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high chromium steel with few defects originating from a blow hole, and a manufacturing method therefor. SOLUTION: The high chromium steel is characterized by including, by mass%, 0.04-0.25% C, 0-1.00% Si, 0.1-1.5% Mn, 4-14% Cr, 0-0.5% Cu, 0-0.8% Ni, 0-0.05% Al, and 0.001-0.1% N, and the balance Fe with impurities, and in the impurities, 0.030% or less S, 0.030% or less P, and 0.02% or less oxygen, while satisfying the expression (1): log[%N]<=0.05[%Cr]-0.34A-1.353...(1), where [%N] indicates a nitrogen content in the steel, [%Cr] indicates a Cr content in the steel, and A indicates a cross sectional area (m<2> ) of a die. The steel can include one or more of Ca or/and Mo, W, Nb, V, Ti and B. The steel can be manufactured by means of casting the steel which has the above composition and satisfies the above expression.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-chromium steel product having few external flaws, for example, a steel used as a material for a seamless steel pipe, and a method for producing the same.

[0002]

2. Description of the Related Art High chrome steel is widely used as a material for various steel products including a material for seamless steel pipe. As the raw material, a steel slab produced by continuous casting, ingot casting, or the like is used as it is, or a material subjected to hot working by heating at 1100 ° C. or higher is used.

When a seamless steel pipe or the like is manufactured using high chromium steel as a material, outer surface defects are often generated as compared with the case where ordinary steel is used as a material. The causes of the defects are various, but nitrogen (N) in the steel is the main cause of the defects.

Nitrogen is added to improve creep strength by forming carbonitrides in a steel pipe for a boiler. Since N is an element that stabilizes austenite, it is often added in an amount of about 0.05 to 0.10% to improve hot workability.

The mechanism of occurrence of external surface flaws in high chromium seamless steel pipes is considered as follows. That is, a steel slab produced by continuous casting, ingot casting, or the like has blowholes due to nitrogen gas generated during casting. This blow hole remains after the pipe manufacturing process and becomes a flaw on the outer surface of the product.

In the blowhole, the nitrogen contained in the molten steel cannot be dissolved in the molten steel due to the decrease of the molten steel temperature at the time of casting, and it is not dissolved in the solid phase either, and becomes N ₂ gas bubbles and solidifies. It is a defect that remains as a hole in the cast slab.
When such a slab is processed into a seamless steel pipe or the like through a process such as rolling, vacancy defects in the slab become outer surface defects.

Conventionally, in order to reduce the above-mentioned external flaws, measures have been taken to remove the defects by cooling a steel slab produced by continuous casting, ingot casting or the like, and then grinding it. . However, such a measure causes a decrease in efficiency and an increase in manufacturing cost, which is not preferable in industrial production.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high chromium steel having few defects caused by blowholes, and a method of manufacturing the steel relatively easily without lowering the productivity.

[0009]

SUMMARY OF THE INVENTION The invention is summarized in the following high chromium steel. In the following description,% related to the content of components means “mass%”.

C: 0.04 to 0.25%, Si: 0 to 1.00%, Mn:
0.1-1.5%, Cr: 4-14%, Cu: 0-0.5%, Ni: 0-
0.8%, Al: 0-0.05%, N: 0.001-0.1%, balance Fe
And impurities, and S in the impurities is 0.030% or less,
A high chromium steel characterized in that P is 0.030% or less, oxygen is 0.02% or less, and the following formula is satisfied.

Log [% N] ≦ 0.05 [% Cr] -0.34A-1.353 However, [% N] is the nitrogen content (mass%) in the steel, [% C]
r] is the Cr content (mass%) in the steel, and A is the cross-sectional area (m ² ) of the mold.

A in the above equation is the cross-sectional area of the mold in the case of continuous casting and the maximum cross-sectional area of the mold in the case of ingot casting.

The above steels may further contain one or more of the following contents of Mo, W, Nb, V, Ti and B, respectively. Moreover, 0.0001 to 0.006% of Ca can be contained.

Mo: 0.1-3%, W: 0.1-3%, Nb: 0.00
5 to 0.2%, V: 0.08 to 0.3%, Ti: 0.005 to 0.03 and B: 0.0001 to 0.02%.

The present invention is also summarized by the following method for producing high chromium steel.

% By mass, C: 0.04 to 0.25%, Si: 0 to 1.
00%, Mn: 0.1 to 1.5%, Cr: 4 to 14%, Cu: 0 to 0.5
%, Ni: 0 to 0.8%, Al: 0 to 0.05%, N: 0.001 to 0.1
%, The balance is Fe and impurities, and S in the impurities is 0.
A method for producing high chromium steel, which comprises casting molten steel containing 030% or less, P of 0.030% or less, oxygen of 0.02% or less, and satisfying the above formula.

The material steel of the above-mentioned manufacturing method is also made of Mo to B.
May include one or more of the ingredients up to
It can contain 0.0001 to 0.006% Ca.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION (1) Composition of Steel The reasons for limiting the composition of the steel of the present invention will be described below together with the action and effect of each component.

C: 0.04 to 0.25% C is added as a stabilizing element of carbide precipitation and martensite structure for securing the strength of steel. If it is less than 0.04%, the amount of δ-ferrite increases and the strength is impaired. on the other hand,
If it exceeds 0.25%, the steel is significantly hardened and the workability and weldability are impaired. Therefore, it is set to 0.04 to 0.25%.

Si: 0 to 1.00% Si acts as a deoxidizing agent in the refining process of steel and is effective for improving steam oxidation resistance of steel, but its content is 1.00.
%, The workability is impaired, so the content was made 1.00% or less.
The Si content in the steel may be substantially 0%. But Si
Also has the effect of increasing the strength of the steel. Therefore, in order to obtain the effects of improving the steam oxidation resistance and improving the strength described above,
A content of 10% or more is desirable.

Mn: 0.1-1.5% Mn improves the hot workability of steel, but if it is less than 0.1%, its effect is small. On the other hand, if it exceeds 1.5%, the steel is hardened and the workability and weldability are impaired. Therefore, the proper content of Mn is 0.1 to 1.5%.

Cr: 4 to 14% Cr is an important element that imparts oxidation resistance and corrosion resistance to steel. If it is less than 4%, the effect is small. On the other hand, if it exceeds 14%, the growth of δ-ferrite is promoted and the strength is impaired. Therefore, the proper content of Cr is 7 to 14%.

Cu: 0 to 0.5% or less Cu is an element effective for improving the oxidation resistance of steel. However, if added too much, the toughness and workability are impaired, so the upper limit of the content should be 0.5%. Cu may be not added, and therefore the content may be substantially 0%, but if it is intended to improve the oxidation resistance, the content is preferably 0.1% or more.

Ni: 0 to 0.8% Ni is an element effective in increasing the toughness of steel, but if it is added too much, the creep strength will decrease, so the content is Ni.
It should be 0.8% or less. Ni may be not added, and the content thereof may be substantially 0%, but if it is intended to improve the toughness, the content of Ni is preferably 0.1% or more.

Al: 0 to 0.05% or less Al is added as a deoxidizing agent for steel. However, when the Al content exceeds 0.05%, the creep strength decreases, so 0.
It was less than 05%. The lower limit may be substantially 0%, but 0.01% or more is desirable to obtain a sufficient deoxidizing effect.

N (nitrogen): 0.001 to 0.1% N is effective for improving creep strength by combining with Nb and V to form a carbonitride, but 0.001%
If it is less than 0.1%, there is no effect. On the other hand, if it exceeds 0.1%, the weldability and workability are impaired.

One of the steels of the present invention is, in addition to the above components, the balance being Fe and impurities. In addition to the above components, another one of the steels of the present invention is the above-mentioned Mo, W, Nb, V, Ti.
And one or more components selected from B, and / or 0.
Steel containing 0001 to 0.006% Ca. Mo, W, Nb, V, T
i and B are components that increase creep strength. Less than,
The effects and proper contents of each are described below.

Mo: 0.1 to 3% Mo is a so-called solid solution strengthening element that forms a solid solution in steel to increase the strength. If it is less than 0.1%, the effect of increasing the strength and creep strength is small, and if it exceeds 3%, an intermetallic compound precipitates, impairing the toughness and workability. Therefore, the proper content of Mo is
It is 0.01 to 3%.

W: 0.1-3% W, like Mo, is a solid solution strengthening element of steel. If it is less than 0.1%, the effect of improving the strength and creep strength is small, and if it exceeds 3%, an intermetallic compound precipitates and the toughness and workability are impaired.
Therefore, the proper content of W is 0.1 to 3%.

Nb: 0.005-0.2% Nb combines with C and N to form a carbonitride, and
Although it is effective in improving the creep strength, if it is less than 0.005%, the effect cannot be obtained, while if it exceeds 0.2%, the weldability and creep strength of steel are impaired. Therefore, the proper Nb content is 0.005 to 0.2%.

V: 0.08-0.3% V also forms a carbonitride by combining with C and N, and is effective in improving strength and creep strength. However, if it is less than 0.08%, a sufficient effect cannot be obtained, while if it exceeds 0.3%, on the contrary, the creep strength is lowered. Therefore, the appropriate content of V is 0.08 to 0.3%.

Ti: 0.005 to 0.03% Ti also forms carbonitrides and is effective in improving the strength and creep strength of steel, but if it is less than 0.005%, a sufficient effect cannot be obtained, while on the other hand, it exceeds 0.03%. And impair toughness. Therefore, Ti
The proper content of is 0.005-0.03%.

B: 0.0001 to 0.02% B is also effective in improving strength and creep strength. But,
If it is less than 0.0001%, a sufficient effect cannot be obtained, while 0.02%
If it exceeds, weldability and workability are impaired. Therefore, the proper content of B is 0.0001 to 0.02%.

Ca: 0.0001 to 0.006% Ca forms an oxide in steel and stabilizes and detoxifies inclusions, thereby improving toughness. However, 0.0001%
If it is less than 0.006%, a sufficient effect cannot be obtained, while if it exceeds 0.006%, the toughness is impaired. Therefore, the proper Ca content is 0.0001-
It is 0.006%.

The impurities P and S of steel are respectively
Must be kept below 0.030%. Oxygen is 0.02
It is necessary to keep the percentage below.

Both P and S are impurity elements harmful to the toughness and hot workability of steel. Therefore, it should be 0.030% or less and as small as possible. If it exceeds 0.030%, flaws are likely to occur during rolling. Oxygen is an impurity element harmful to the toughness and hot workability of steel. Therefore, it is preferably 0.02% or less and as small as possible.

(2) Relationship between Nitrogen [N] and Cr in Steel Blowhole is
Since it cannot be melted as the temperature is lowered, it is not solid-solved in the solid phase and is discharged to the molten steel. Therefore, if the N content of steel is reduced, the occurrence of defects can be suppressed, but depending on the type of steel, it is essential to contain N to some extent or more, and if the N content is unduly reduced, the performance of steel products will be deteriorated. Also, even if defects such as blowholes occur in the slab,
It is possible to remove it by caring for the slab, but this causes an extra process and an increase in cost.

Therefore, in the present invention, by making the degree of influence of the constituents into an index, it is possible to manufacture steel with few blowholes without degrading product performance.

FIG. 1 is a diagram showing the relationship between the temperature of steel and the nitrogen solubility. Nitrogen, which has a high solubility in a high temperature liquid phase (Lid.), Is separated as bubbles when the solid phases of δ-ferrite (δ) and austenite (γ) are deposited, because the solubility is low in the solid phase.

FIG. 2 is a diagram showing the relationship between the nitrogen solubility and the Cr content in molten steel at 1600 ° C. The solid line indicated by a is the nitrogen solubility curve.

Now, in the Fe-Cr-N ternary system, the liquid phase (1600
Considering the nitrogen solubility of (° C.), logf _N ^Cr = log [% N ₀ ] −log [% N] ... However, [% N ₀ ] is the N content in the molten steel in the Fe-N system, and [% N] is N in the ternary molten steel of Fe-Cr-N.
It is the content. In addition, logf _N ^Cr = e _N ^Cr [% Cr]. Therefore, the above equation (a) is expressed as e _N ^Cr [% Cr] = log
_{[% N 0] -log [%} N], i.e., the log [% N] = log [ % N 0] -e N Cr [% Cr] ··· b.

According to Pehle and Elliott (see, for example, Japan Society for the Promotion of Science, Steelmaking 19th Committee, "Recommended Equilibrium Value of Steelmaking Reaction, Revision and Supplement" (November 1984), page 18), log [% N
₀ ] = − 188 / T−1.248 (T is absolute temperature), and the formula of S. Banya et al. (See page 258 of the above publication).
According to _a ^{e N Cr = -148 / T +} 0.033. Therefore, the formula b becomes log [% N] = (− 188 / T−1.248) − (− 148 / T + 0.033) [% Cr] ...

In the above C formula, T is the melting point of 9% Cr steel 15
Substituting 06 ° C (that is, 1789K) gives the following two equations. log [% N] = 0.05 [% Cr] -1.353 ... D The above formula is for the ideal state (equilibrium state). In actual casting, a non-equilibrium state occurs due to the influence of the mold size. That is, the nitrogen content at the blowhole generation limit fluctuates due to the influence of the mold size, and therefore correction is necessary.

The marks ◯ and X shown in FIG. 2 described above show a part of the generation state of the outer surface flaw of the seamless steel pipe in the embodiment described later. That is, ○ is the rejection rate is less than 10%, × is
It means 10% or more. As shown in the figure, the reject rate has a fixed relationship with the curve b.

As described above, the mold size influences the generation of blowholes and eventually the generation of external defects. Therefore, in order to confirm the degree of the influence, the relationship between the cross-sectional area of the mold and the generation of external defects was investigated.

In FIG. 3, the horizontal axis represents the cross-sectional area A of the mold, and the vertical axis represents 0.
The results of the examples described below are plotted as 05 [% Cr] −log [% N] −1.353. The meanings of O and X in the figure are as described above. From this FIG. 3, the slope “0.34” of the boundary straight line (broken line c in the figure) at which the rejection rate becomes 10% is obtained. That is, the broken line c is represented by y = 0.34A.

Here, y is 0.05 [% Cr] -log [% N]-
Since it is 1.353, 0.05 [% Cr] −log [% N] −1.353 = 0.3
4A, and eventually log [% N] = 0.05 [% Cr] -0.34A-1.353 ... This E formula is a formula considering the mold size instead of the above-mentioned D formula.

The above E formula is a formula in which the curve b shown in FIG. 2 is corrected in consideration of the influence of the cross-sectional area A of the mold. Therefore,
The area where the number of external defects is small and the rejection rate is less than 10% is an area where the following formula is satisfied.

Log [% N] ≦ 0.05 [% Cr] −0.34A−1.353 ... When the mold cross-sectional area A is small, the cooling rate is fast and the concentration of nitrogen at the solidification interface is unlikely to rise. Therefore, the allowable amount of [N] becomes large. On the other hand, if A is large, the cooling rate will slow down,
The allowable amount of [N] becomes smaller. Since the nitrogen concentration at the solidification interface further decreases when the solidified shell is forcibly cooled during casting as in continuous casting, the formula is a standard with a sufficient margin as the control standard for the allowable amount of [N]. That is, it can be said that the formula shows a condition sufficient to prevent blowhole defects in the cast slab. In addition, A is generally 0.02 to 1.00.
It is in the range of (m ² ).

The behavior of nitrogen in the process of solidifying molten steel has been described above. In summary, if molten steel satisfying the formula is cast, a slab with few defects caused by blowholes can be manufactured. And even in the slab, the nitrogen content and Cr
The content will satisfy the formula. That is, the high chromium steel of the present invention satisfying the formula has few defects caused by blowholes, and the products such as seamless steel pipe manufactured from the steel have extremely few external flaws.

[0051]

EXAMPLES Steels having the compositions shown in Tables 1 and 2 were melted, ingot-cast or continuously cast, and slab-rolled into round billets. In order to eliminate the effect of slabbing, the billet was externally cut to a depth of 2 mm to a diameter of 189 mm, and then a seamless steel pipe was manufactured by the Mannesmann mandrel mill method. The seamless steel pipe has an outer diameter of 60.2 to 141 mm and a wall thickness of 5 to 15 mm.
And the number shown in Table 3 and Table 4 was manufactured for each steel type.

After the pipe was made, the seamless steel pipe was inspected visually and by ultrasonic flaw detection, and a pipe having a flaw of 5% or more of the wall thickness was rejected. Casting conditions and inspection results are shown in Tables 3 and 4.

The reject rate in Tables 3 and 4 means "the number of rejects /
The number of steel pipes manufactured is 100. In the left column of Table 3 and Table 4
The value of 0.05 [% Cr] -0.34A-log [% N] of 1.353 or more is an example satisfying the above formula. The rejection rate is
It is less than 10%. On the other hand, in the case where this value is less than 1.353 (Test Nos. 5, 18, 19, 20, 34), the occurrence rate of external defects is high, which is 10% or more.

FIG. 4 shows some of the test results of Table 3 and Table 4.
This is illustrated by the relationship between 0.05 [% Cr] -0.34A-log [% N] and the rejection rate. From this figure, 0.05 [% Cr] -0.34A-
It is clear that the rejection rate increases when the value of log [% N] is less than 1.353.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

[Table 3]

[0058]

[Table 4]

The high chromium steel of the present invention has extremely few defects caused by blowholes. This steel is
It can be reliably manufactured by the method of the present invention in which the Cr content and the nitrogen content of steel are controlled by the above formula. The high chromium steel of the present invention is useful as a material for producing seamless steel pipes and other products while suppressing the occurrence of external defects.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between temperature and nitrogen solubility of steel.

FIG. 2 is a diagram showing a relationship between a Cr content and a nitrogen solubility in a Fe—Cr—N system at 1600 ° C. and a boundary of a rejection rate of 10% due to a flaw generation.

Fig. 3 Cross-sectional area of mold and 0.05 [% Cr] -log [% N] -1.353
It is a figure which shows the boundary line of the rejection rate 10% by the defect generation of the high chromium steel on the map with the value of.

FIG. 4 is a diagram showing the relationship between 0.05 [% Cr] -0.34A-log [% N] and the rejection rate due to the occurrence of flaws.

Claims (8)

[Claims] 1. In mass%, C: 0.04 to 0.25%, Si: 0 to 1.
00%, Mn: 0.1 to 1.5%, Cr: 4 to 14%, Cu: 0 to 0.5
%, Ni: 0 to 0.8%, Al: 0 to 0.05%, N: 0.001 to 0.1
%, The balance is Fe and impurities, and S in the impurities is 0.
A high chromium steel which is 030% or less, P is 0.030% or less, oxygen is 0.02% or less, and satisfies the following formula. log [% N] ≦ 0.05 [% Cr] -0.34A-1.353 However, [% N] is the nitrogen content (mass%) in the steel, and [% Cr] is the Cr content (mass) in the steel. %), A is the cross-sectional area (m ² ) of the mold. 2. In mass%, C: 0.04 to 0.25%, Si: 0 to 1.
00%, Mn: 0.1 to 1.5%, Cr: 4 to 14%, Cu: 0 to 0.5
%, Ni: 0 to 0.8%, Al: 0 to 0.05%, N: 0.001 to 0.1
%, And Mo, W, Nb, V with the following contents, respectively:
One or more of Ti and B, the balance being Fe and impurities, S in the impurities being 0.030% or less, P being 0.030% or less, oxygen being 0.02% or less, and satisfying the following formula: And high chrome steel. Mo: 0.1-3%, W: 0.1-3%, Nb: 0.005-0.2%,
V: 0.08-0.3%, Ti: 0.005-0.03 and B:
0.0001 to 0.02%. log [% N] ≦ 0.05 [% Cr] -0.34A-1.353 However, [% N] is the nitrogen content (mass%) in the steel, and [% Cr] is the Cr content (mass) in the steel. %), A is the cross-sectional area (m ² ) of the mold. 3. In mass%, C: 0.04 to 0.25%, Si: 0 to 1.
00%, Mn: 0.1 to 1.5%, Cr: 4 to 14%, Cu: 0 to 0.5
%, Ni: 0 to 0.8%, Al: 0 to 0.05%, N: 0.001 to 0.1
%, Ca: 0.0001 to 0.006%, the balance Fe and impurities, S in the impurities is 0.030% or less, P is 0.030% or less,
A high chromium steel having an oxygen content of 0.02% or less and satisfying the following formula. log [% N] ≦ 0.05 [% Cr] -0.34A-1.353 However, [% N] is the nitrogen content (mass%) in the steel, and [% Cr] is the Cr content (mass) in the steel. %), A is the cross-sectional area (m ² ) of the mold. 4. In mass%, C: 0.04 to 0.25%, Si: 0 to 1.
00%, Mn: 0.1 to 1.5%, Cr: 4 to 14%, Cu: 0 to 0.5
%, Ni: 0 to 0.8%, Al: 0 to 0.05%, N: 0.001 to 0.1
%, Ca: 0.0001 to 0.006%, and one or more of Mo, W, Nb, V, Ti and B each having the following content,
The balance consists of Fe and impurities, and S in the impurities is 0.030.
%, P is 0.030% or less, oxygen is 0.02% or less, and the following formula is satisfied, a high chromium steel. Mo: 0.1-3%, W: 0.1-3%, Nb: 0.005-0.2%,
V: 0.08-0.3%, Ti: 0.005-0.03 and B:
0.0001 to 0.02%. log [% N] ≦ 0.05 [% Cr] -0.34A-1.353 However, [% N] is the nitrogen content (mass%) in the steel, and [% Cr] is the Cr content (mass) in the steel. %), A is the cross-sectional area (m ² ) of the mold. 5. In mass%, C: 0.04 to 0.25%, Si: 0 to 1.
00%, Mn: 0.1 to 1.5%, Cr: 4 to 14%, Cu: 0 to 0.5
%, Ni: 0 to 0.8%, Al: 0 to 0.05%, N: 0.001 to 0.1
%, The balance is Fe and impurities, and S in the impurities is 0.
A method for producing high chromium steel, which comprises casting molten steel containing 030% or less, P of 0.030% or less, oxygen of 0.02% or less, and satisfying the following formula. log [% N] ≦ 0.05 [% Cr] -0.34A-1.353 However, [% N] is the nitrogen content (mass%) in the steel, and [% Cr] is the Cr content (mass) in the steel. %), A is the cross-sectional area (m ² ) of the mold. 6. In mass%, C: 0.04 to 0.25%, Si: 0 to 1.
00% or less, Mn: 0.1 to 1.5%, Cr: 4 to 14%, Cu: 0 to 0.
5%, Ni: 0-0.8%, Al: 0-0.05%, N: 0.001-0.1
%, And Mo, W, Nb, V with the following contents, respectively:
Cast molten steel containing at least one of Ti and B, the balance of Fe and impurities, S in the impurities of 0.030% or less, P of 0.030% or less, oxygen of 0.02% or less, and satisfying the following formula A method for producing high-chromium steel, which comprises: Mo: 0.1-3%, W: 0.1-3%, Nb: 0.005-0.2%,
V: 0.08-0.3%, Ti: 0.005-0.03 and B:
0.0001 to 0.02%. log [% N] ≦ 0.05 [% Cr] -0.34A-1.353 However, [% N] is the nitrogen content (mass%) in the steel, and [% Cr] is the Cr content (mass) in the steel. %), A is the cross-sectional area (m ² ) of the mold. 7. In mass%, C: 0.04 to 0.25%, Si: 0 to 1.
00%, Mn: 0.1 to 1.5%, Cr: 4 to 14%, Cu: 0 to 0.5
%, Ni: 0 to 0.8%, Al: 0 to 0.05%, N: 0.001 to 0.1
%, Ca: 0.0001 to 0.006%, the balance Fe and impurities, S in the impurities is 0.030% or less, P is 0.030% or less,
A method for producing high-chromium steel, characterized by casting molten steel having an oxygen content of 0.02% or less and satisfying the following formula. log [% N] ≦ 0.05 [% Cr] -0.34A-1.353 However, [% N] is the nitrogen content (mass%) in the steel, and [% Cr] is the Cr content (mass) in the steel. %), A is the cross-sectional area (m ² ) of the mold. 8. In mass%, C: 0.04 to 0.25%, Si: 0 to 1.
00%, Mn: 0.1 to 1.5%, Cr: 4 to 14%, Cu: 0 to 0.5
%, Ni: 0 to 0.8%, Al: 0 to 0.05%, N: 0.001 to 0.1
%, Ca: 0.0001 to 0.006%, and M below
One or more of o, W, Nb, V, Ti and B, with the balance being F
e and impurities, and S in the impurities is 0.030% or less,
A method for producing high chromium steel, characterized in that P is 0.030% or less, oxygen is 0.02% or less, and molten steel satisfying the following formula is cast. Mo: 0.1-3%, W: 0.1-3%, Nb: 0.005-0.2%,
V: 0.08-0.3%, Ti: 0.005-0.03 and B:
0.0001 to 0.02%. log [% N] ≦ 0.05 [% Cr] -0.34A-1.353 However, [% N] is the nitrogen content (mass%) in the steel, and [% Cr] is the Cr content (mass) in the steel. %), A is the cross-sectional area (m ² ) of the mold.