JP6987651B2 - High hardness precipitation hardening stainless steel with excellent hot workability and no sub-zero treatment required - Google Patents

Description

This application relates to stainless steel for use as members that require high hardness and high corrosion resistance such as propeller shafts, drive shafts, bearings and rolls, and has particularly excellent hot workability and high hardness precipitation hardening that does not require sub-zero treatment. Regarding type stainless steel.

Precipitation-hardened stainless steel has corrosion resistance as stainless steel and strength due to precipitation hardening, and is classified into martensitic, semi-martensite, and austenite according to the substrate structure. Austenitic stainless steels can be used for non-magnetic applications. The martensitic and semi-martensite systems are those that dissolve in austenite and precipitate a metal or compound that has almost no solubility in martensite from the martensitic region after transformation of martensite. It is characterized in that it is used in combination with martensitic transformation and precipitation hardening.

As precipitation hardening stainless steel, C ≦ 0.05 mass%, 0.5 ≦ Si <2.0 mass%, Mn ≦ 1.50 mass%, 2.0 ≦ Cu ≦ 5.0 mass%, 2.0 ≦ Ni < 7.0 mass%, 10.0 ≤ Cr ≤ 15.0 mass%, 1.0 ≤ Co ≤ 5.0 mass%, 2.0 <Mo ≤ 5.0 mass%, 0.5 <Ti ≤ 3.0 mass%, and , N ≦ 0.05 mass%, the balance consisting of Fe and unavoidable impurities, and precipitation hardening stainless steel satisfying Si + Ti + Co ≧ 4.5 and Si / Mo ≦ 0.7 have been proposed (eg, Patent Documents). See 1.).
According to Patent Document 1, when Cu is added to steel containing a predetermined element, the hardness is increased by precipitating the ε-Cu phase and the G phase by solidification heat treatment and aging treatment, and Si / Mo in terms of mass ratio. We are trying to improve hot workability by optimizing the ratio. However, in this patent, Co is an essential element as a component of steel. We are also trying to improve hot workability by satisfying Si / Mo ≤ 0.7, but we have also developed precipitation hardening stainless steel with further improvement in hot workability, and Co and Mo. It is required to reduce the use of expensive elements such as as much as possible.

On the other hand, the applicant of the present application has C: 0.01 to 0.10%, Si: 0.30 to 2.00%, Mn: 0.01 to 1.00%, P: 0.040 in mass%. % Or less, S: 0.030% or less, Ni: 4.0 to 9.0%, Cr: 13.0 to 22.0%, Mo: 0.20 to 2.00%, Cu: 0.60 to 0 Corrosion resistance and manufacturability containing 4.00%, Ti: 0.50 to 3.50%, Nb: 0.01 to 2.00%, N: 0.050% or less, and consisting of the balance Fe and unavoidable impurities. Has filed a patent application for excellent high-hardness stainless steel (see Patent Document 2). This Patent Document 2 describes that both high hardness and high corrosion resistance are compatible and that the heat treatment range in which high hardness can be obtained is wide, and Cr of 13.0% or more is required to improve the corrosion resistance. There is. However, in Patent Document 2, in order to transform the retained austenite into martensitic transformation, a sub-zero treatment in which the retained austenite is kept at −20 ° C. to −90 ° C. for 10 minutes or more is required, which is costly to manufacture.

Japanese Patent No. 5878896 Japanese Unexamined Patent Publication No. 2017-78195

For applications where a high hardness material is required, martensitic stainless steel such as SUS420 is used. However, martensitic stainless steel has a relatively high C content and low corrosion resistance. In comparison, precipitation hardening stainless steels such as SUS630 have excellent corrosion resistance but have a problem of low hardness. Therefore, adjustments have been made in the past to achieve both of these, but they are not sufficient, and there is a demand for further improvement in hot workability and reduction of expensive elements such as Co and Mo as much as possible. Further, when the Ms point (martensite transformation start temperature) is low, retained austenite is generated and the hardness becomes low, so that subzero treatment may be used to avoid it. However, the sub-zero treatment has a problem that it is very costly because it is cooled by using a cooling agent such as dry ice or liquid nitrogen.

Therefore, the problem to be solved by the present application is to provide a high hardness precipitation hardening stainless steel having excellent manufacturability by eliminating the above-mentioned sub-zero treatment and improving hot workability. Is.

In the first means for solving the above problems, in terms of mass%, C: 0.01 to 0.10%, Si: 0.30 to 2.00%, Mn: 0.01 to 1 .00%, Ni: 4.00 to 9.00%, Cr: 8.01 to 14.50%, Mo: 0.10 to 2.00%, Cu: 0.50 to 4.00%, Ti: It contains 0.50 to 3.50%, is composed of the balance Fe and unavoidable impurities, satisfies the following formulas (1) and (2), has a hardness of 55HRC or more, a residual austenite amount of 1% or less, and heat. It is a high hardness precipitation hardening stainless steel having excellent manufacturability, characterized in that the temperature range in which the drawing (RA) is 60% or more in the intertensile test (greeble test) is 100 ° C. or more.
5.00 ≤ Ni _eq ≤ <9.50 ... Equation (1)
Ni _eq ≤ -0.83 x Cr _eq + 25.5 ... Equation (2)
However, Ni _eq = [% Ni] +30 × ([% C] + [% N]) +0.5 × [% Mn] +0.3 × [% Cu], and Cr _eq = [% Cr] + [ % Mo] + 1.5 × [% Si] + 0.5 × [% Nb].
In each of the above [% M], the numerical value (mass%) of the content of the corresponding element is substituted.

In the second means, in addition to the chemical components of the first means, in mass%, Al: 0.001 to 0.150%, Nb: 0.01 to 2.00%, N: 0.002 to 0. .050% and S: any one or more selected from 0.001 to 0.100%, except for Cr in the chemical composition of the first means, Cr: 8. It is set to less than 00 to 13.00%, consists of the balance Fe and unavoidable impurities, satisfies the following formulas (1) and (2), has a hardness of 55HRC or more, a residual austenite amount of 1% or less, and a hot tensile test. It is a high hardness precipitation hardening stainless steel having excellent manufacturability, characterized in that the temperature range in which the drawing (RA) is 60% or more in (Greble test) is 100 ° C. or more.
5.00 ≤ Ni _eq ≤ 9.50 ... Equation (1)
Ni _eq ≤ -0.83 x Cr _eq + 25.5 ... Equation (2)
However, Ni _eq = [% Ni] + 30 × ([% C] + [% N]) + 0.5 × [% Mn] + 0.3 × [% Cu], and Cr _eq = [% Cr] + [ % Mo] + 1.5 × [% Si] + 0.5 × [% Nb].
In each of the above [% M], the numerical value (mass%) of the content of the corresponding element is substituted.

In the third means, in addition to the chemical components of the first means, Ca: 0.0001 to 0.0250%, Mg: 0.0001 to 0.0250%, B: 0.0001 to 0 in mass%. It contains any one or more selected from .0250%, consists of the balance Fe and unavoidable impurities, satisfies the formulas (1) and (2) described below, has a hardness of 55HRC or more, and remains. High hardness precipitation hardening type with excellent manufacturability, characterized in that the amount of austenite is 1% or less and the temperature range in which the drawing (RA) in the hot tensile test (greeble test) is 60% or more is 100 ° C. or more. It is stainless steel.
5.00 ≤ Ni _eq ≤ 9.50 ... Equation (1)
Ni _eq ≤ -0.83 x Cr _eq + 25.5 ... Equation (2)
However, Ni _eq = [% Ni] +30 × ([% C] + [% N]) +0.5 × [% Mn] +0.3 × [% Cu], and Cr _eq = [% Cr] + [ % Mo] + 1.5 × [% Si] + 0.5 × [% Nb].
In each of the above [% M], the numerical value (mass%) of the content of the corresponding element is substituted.

In the fourth means, in addition to the chemical components of the first means, Al: 0.001 to 0.150%, Nb: 0.01 to 2.00%, N: 0.002 to 0 in% by mass. It contains any one or more selected from 050% and S: 0.001 to 0.100%, and further, in terms of mass%, Ca: 0.0001 to 0.0250%, Mg: 0. It contains any one or more selected from 0001 to 0.0250% and B: 0.0001 to 0.0250%, and consists of the balance Fe and unavoidable impurities, and is composed of the formula (1) and the formula described below. Satisfying (2), the hardness is 55HRC or more, the amount of retained austenite is 1% or less, and the temperature range in which the drawing (RA) in the hot tensile test (greeble test) is 60% or more is 100 ° C. or more. It is a high hardness precipitation hardening type stainless steel having excellent manufacturability.
5.00 ≤ Ni _eq ≤ 9.50 ... Equation (1)
Ni _eq ≤ -0.83 x Cr _eq + 25.5 ... Equation (2)
However, Ni _eq = [% Ni] +30 × ([% C] + [% N]) +0.5 × [% Mn] +0.3 × [% Cu], and Cr _eq = [% Cr] + [ % Mo] + 1.5 × [% Si] + 0.5 × [% Nb].
In each of the above [% M], the numerical value (mass%) of the content of the corresponding element is substituted.

According to the above-mentioned means, the present invention has a hardness of 55 HRC or more, weather resistance, which makes it difficult to stirrate, a residual austenite amount of 1% or less, and a hot tensile test drawing (RA). It is possible to produce high hardness precipitation hardening stainless steel having a temperature range of 60% or more of 100 ° C. or higher, excellent hot workability, and excellent manufacturability that does not require sub-zero treatment.

Prior to describing the embodiment for carrying out the invention of the present application, the reasons for limiting the chemical components other than Fe in each of the above-mentioned means of the present application and the formulas (1) and (2) will be described below. The% of the chemical component is mass%.

C: 0.01 to 0.10%
C is an element required to maintain the strength and corrosion resistance of steel. If C is less than 0.01%, the strength will be insufficient. On the other hand, if C is more than 0.10%, the corrosion resistance is lowered. Therefore, C is set to 0.01 to 0.10%.

Si: 0.30 to 2.00%
Si is a deoxidizing material during steel smelting and is an element necessary for contributing to the precipitation strengthening of steel. If Si is less than 0.30%, it will be insufficient as a deoxidizing agent during smelting and will be insufficient as a precipitation strengthening element of steel. On the other hand, when Si is more than 2.00%, the hot workability of the steel is lowered. Therefore, Si is set to 0.30 to 2.00%.

Mn: 0.01-1.00%
Mn is an element required as a deoxidizing material during steel smelting. If Mn is less than 0.01%, it will be insufficient as a deoxidizing agent during smelting. On the other hand, if Mn is more than 1.00%, the hot workability of the steel is lowered. Therefore, Mn is set to 0.01 to 1.00%.

Ni: 4.00-900%
Ni is an element that contributes to the precipitation strengthening of steel. If Ni is less than 4.00%, it will be insufficient as a precipitation strengthening element for steel. On the other hand, Ni is an expensive element, so if it is more than 9.00%, the cost will increase. Therefore, Ni is set to 4.00 to 9.00%.

Cr: 8.00 to 14.50%
Cr is an element that contributes to the corrosion resistance of steel. If Cr is less than 8.00%, the corrosion resistance is lowered. On the other hand, if Cr is more than 14.50%, the hot workability is lowered and Cr is an expensive element, which increases the cost. Therefore, Cr is set to 8.00 to 14.50%, preferably less than 8.00 to 13.00.

Mo: 0.10 to 2.00%
Mo is an element that contributes to the corrosion resistance of steel. If Mo is less than 0.10%, the corrosion resistance is lowered. On the other hand, if the amount of Mo is more than 2.00, the hot workability is lowered and the element is expensive, so that the cost is increased. Therefore, Mo is set to 0.10 to 2.00%.

Cu: 0.50 to 4.00%
Cu is an element that contributes to the corrosion resistance of steel and also contributes to precipitation strengthening. If the amount of Cu is less than 0.50%, the corrosion resistance of the steel is lowered, and it is insufficient as an element that contributes to precipitation strengthening. On the other hand, if the amount of Cu is more than 4.00%, the hot workability is deteriorated. Therefore, Cu is set to 0.50 to 4.00%.

Ti: 0.50 to 3.50%
Ti is an element that contributes to the precipitation strengthening of steel. If Ti is less than 0.50%, it is insufficient as a precipitation strengthening element for steel. On the other hand, if Ti is more than 3.50%, the hot workability is lowered and the cost is increased. Therefore, Ti is set to 0.50 to 3.50%.

Next, the elements of the selective chemical composition used in the present invention will be described below.

Al: 0.001 to 0.150%
Al is a component that lowers the corrosion resistance of steel and also lowers the hot workability. Therefore, the upper limit is 0.150%. On the other hand, if Al is forcibly reduced, the cost will be high, and therefore, it may be 0.001% or more from an economic point of view.

Nb: 0.01 to 2.00%
Nb can be added as a component that suppresses grain grain coarsening of steel. However, if it is less than 0.01%, the effect of suppressing grain grain coarsening cannot be obtained. On the other hand, if it exceeds 2.00%, the hot workability is lowered and the cost is increased. Therefore, Nb is set to 0.01 to 2.00%.

N: 0.002 to 0.050%
N is a component that lowers the hot workability of steel. If it exceeds 0.050%, the ferrite becomes unstable. Therefore, the upper limit is 0.050%. On the other hand, if N is forcibly reduced, the cost will be high, so it may be 0.002% or more from an economic point of view.

S: 0.001 to 0.100%
S is a chemical component that can be added to improve the machinability of steel. However, if it is less than 0.001%, it is too small to obtain the effect. On the other hand, if it exceeds 0.100%, the hot workability is lowered. Therefore, S is set to 0.001 to 0.100%.

The above chemical components of Al, Nb, N, and S can be selectively added by one or more.

Further, selective chemical components other than the above used in the present invention will be described below.

Mg: 0.0001 to 0.0250%
Mg is a chemical component that can be added to contribute to the hot workability of steel. However, if it is less than 0.0001%, no contribution to hot workability is observed. On the other hand, if it exceeds 0.0250% and is excessive, the hot workability is rather lowered. Therefore, it is set to 0.0001 to 0.0250%.

Ca: 0.0001 to 0.0250%
Ca is a chemical component that can be added to contribute to the hot workability of steel. However, if it is less than 0.0001%, no contribution to hot workability is observed. On the other hand, if it exceeds 0.0250% and is excessive, the hot workability is rather lowered. Therefore, it is set to 0.0001 to 0.0250%.

B: 0.0001 to 0.0250%
B is a chemical component that can be added to contribute to the hot workability of steel. However, if it is less than 0.0001%, no contribution to hot workability is observed. On the other hand, if it exceeds 0.0250% and is excessive, the hot workability is rather lowered. Therefore, it is set to 0.0001 to 0.0250%.

The above chemical components of Mg, Ca, and B can be selectively added by one or more.

Equation (1): 5.00 ≤ Ni _eq ≤ 9.50
_{The value of Ni eq in} the formula (1) needs to be 5.00 or more and 9.50 or less. When the formula (1) does not satisfy the above conditions, the hot workability of the steel is lowered. Therefore, the equation (1) is set to 5.00 ≤ Ni _eq ≤ 9.50.
_{However, Ni eq} in the above formula (1) = [% Ni] + 30 × ([% C] + [% N]) + 0.5 × [% Mn] + 0.3 × [% Cu].

Equation (2): Ni _eq ≤ −0.83 × Cr _eq + 25.5
As shown in the formula (2), the value of _{Ni eq} needs to be equal to or less than the value of _{−0.83 × Cr eq + 25.5.} This is because when the formula (2) does not satisfy the above conditions, the amount of retained austenite increases. Therefore, the formula (2) is Ni _eq ≤ −0.83 × Cr _eq + 25.5.
However, Ni _eq is Ni _eq = [% Ni] + 30 × ([% C] + [% N]) + 0.5 × [% Mn] + 0.3 × [% Cu], and further, Cr _eq = [% Cr] + [% Mo] + 1.5 × [% Si] + 0.5 × [% Nb].
In addition, the value of [% M] (“M” indicates a chemical component) in the equations (1) and (2) is the magnitude of the numerical value of mass%, that is, the content of the corresponding element. A numerical value (mass%) is substituted.

Next, a mode for carrying out the invention of the present application will be described below based on examples.

The chemical composition of the invention steel of the first means shown in Table 1, the chemical composition of the invention steel of the second means shown in Table 2, the invention steel of the third means and the invention steel of the fourth means shown in Table 3. Example steels of each chemical component, and comparative examples of each chemical component of comparative steel 1 (comparative steel for the first means) and comparative steel 2 (comparative steel for the second means) shown in Table 4 and a table. Each of the comparative examples of the chemical components of the comparative steel 3 (comparative steel for the third means) and the comparative steel 4 (comparative steel for the fourth means) shown in 5 is provided, and the balance of Fe and unavoidable. Each of the steels of Examples and Comparative Examples composed of impurities was melted in a 100 kg VIM (vacuum induction melting furnace) and cast into an ingot.
These ingots were forged into steel bars having a diameter of 20 mm at 1150 ° C. Further, these steel bars were kept at 900 to 1200 ° C. for 1 hour, then cooled with water and subjected to a solidification heat treatment. Further, these solid solution heat-treated steel bars were held at 300 to 800 ° C. for 1 hour, then air-cooled and subjected to aging heat treatment.

The following tests were carried out from each material adjusted to each size after the above aging heat treatment. The results of the test show the characteristics of the invention steels in Table 1, Table 2, and Table 3 together with the chemical composition of the invention steels of the claimed steels, and further, Tables 4 and 5 show the first to fourth items. Each of these properties is shown together with the chemical composition of the comparative steel, which is a comparative example of the invention of the means.
As for each characteristic, those satisfying the formulas (1) and (2) were marked with ◯, those not satisfying the formulas (2) were marked with x, and are shown in Table 1, Table 2, and Table 3, and Tables 4 and 5. In the weather resistance test, those that were rusted were marked with x, those that were not rusted were marked with ◯, and are shown in Tables 1, 2, and 3, and Tables 4 and 5. The underlined parts in Tables 4 and 5 indicate that they are outside the scope of the present invention.

_{The evaluation items were Ni eq} and Cr _{eq of} each invention steel and each comparative steel, as well as peak hardness (HRC) and weather resistance of aging (in a salt spray test, 50 ppm Nickel was sprayed at 35 ° C for 16 hours without rusting. ◯, with rusting was ×), the amount of retained austenite (%), and the temperature (° C.) at which the throttle (RA) of hot workability (greeble test) was 60% or more.

The evaluation method is Ni _eq (that is, Ni equivalent), Cr _eq (that is, Cr equivalent), the Ms point (° C) which is the martensite starting temperature, the magnitude of each value of the formulas (1) and (2), and these. Means showing the peak hardness, weather resistance, residual austenite amount, residual γ amount, and hot workability drawing, that is, the temperature at which RA is 60% or more, which are related to the values. Measured by.

That is, for the peak hardness in the aging hardness, the Rockwell hardness in the middle circumference of the cross section perpendicular to the forging direction was measured using the round bar subjected to the above-mentioned various aging treatments, and the obtained hardness was obtained. Among them, the one with the largest value was regarded as the peak hardness, and the one having the value of HRC55 or more was judged to be good.

For weather resistance (in a salt spray test, 50 ppm NaCl was sprayed at 35 ° C. for 16 hours), the above-mentioned round bars subjected to various aging treatments were adjusted to a size of 12 mm in diameter and 21 mm in length, and a weather resistance test was carried out. .. Specifically, salt water having a predetermined concentration and temperature was continuously sprayed on the surface of the test piece for a predetermined time, and after the test, the presence or absence of rusting on the surface of the washed test piece was investigated.

For the residual austenite amount, that is, the residual γ amount, the residual austenite amount in the middle peripheral portion of the cross section perpendicular to the forging direction was measured using the round bar subjected to the above-mentioned various aging treatments. A curved IPX-ray diffractometer RINT RAPID II (Rigaku Co., Ltd., Japan) was used for the measurement.

At a drawing in hot workability (gleeble test), that is, at a temperature at which RA of 60% or more can be obtained, the round bar subjected to the above-mentioned various aging treatments is adjusted to a test piece having a diameter of 8 mm and a length of 100 mm, and is heated by energization. A hot tensile test (gleeble test) was carried out. The test temperature was set every 25 ° C. from 800 to 1350 ° C., and the temperature range in which the drawing RA in the hot workability of the test piece after fracture was 60% or more was calculated. Those having a temperature range of 100 ° C. or higher were judged to be good.

As shown in Table 1, Table 2 and Table 3, each No. 1 of the first to fourth means of the present application. In the column of the formula (1) in the table, the case where the formula (1) was satisfied was evaluated as ◯.
The equation (1) is 5.00 ≦ Ni _eq ≦ 9.50.
Further, in the column of the formula (2) in the table, the case where the formula (2) was satisfied was evaluated as ◯.
Equation (2) is Ni _eq ≤ −0.83 × Cr _eq + 25.5.
In addition, Ni _eq = [% Ni] + 30 × ([% C] + [% N]) + 0.5 × [% Mn] + 0.3 × [% Cu], and Cr _eq = [% Cr] + [ % Mo] + 1.5 × [% Si] + 0.5 × [% Nb].

No. 1 of the first to fourth means of the present application. _{About the characteristics of the invention steel of the above, the value of Ni eq} in Table 1, Table 2, and Table 3 is 5.00 or more and 9.50 or less. Further, the value of _{Cr eq} varies depending on the value of _{Ni eq and is 9.4 to 15.7.}
The Ms point (martensite transformation start temperature) is 106 to 262 ° C. Further, those satisfying the equations (1) and (2) are indicated by ◯, and both have values satisfying both equations.

The steels of the inventions of the first to fourth means of Tables 1, 2 and 3 that satisfy these characteristics have the following characteristics. The peak hardness in the aging hardness after the aging heat treatment was 55HRC or more, the weather resistance was not rusted in the salt spray test, and these are indicated by ○, and the residual austenite amount, that is, the residual γ amount was 1.0% or less. Further, the temperature at which the drawing (RA) in the hot tensile test (greeble test) is 60% or more is 100 ° C. or more.

For each of the invention steels of the first to fourth means of Tables 1, 2 and 3 above, the comparative steels 1 and the comparative steels 2 are shown in Tables 4 and 5 and corresponding in the same order as these. No. of Comparative Steel 3 and Comparative Steel 4. As an evaluation of the above-mentioned test, the characteristics outside the range of the characteristics of each of the inventions of the first to fourth means are sequentially described below.

First, No. 1 of the comparative steel 1 corresponding to the first means. 1 to 15 will be described below.
No. In No. 1, since the Ms point, which is the martensite starting temperature, is as low as 61 ° C. and less than 100 ° C., the residual austenite amount (that is, the residual γ amount in Table 1) is 2.4%, which is the one specified in the present invention. The drawing RA, which is more than 0.0% and has hot workability, is less than 100 ° C., which is the lower limit of the temperature of 60% or more, and is extremely low at 25 ° C.
No. In No. 2, the C content was 0.12%, which was higher than the range of the present invention, the Ni _eq was 10.58, which was higher than 9.50 of the present invention, and the Ms point was 69 ° C., which was lower than 100 ° C. Since it does not satisfy the formula (1), it is ×, the weather resistance is also ×, the residual austenite amount (residual γ amount) is 2.8%, which is more than 1.0% specified in the present invention, and the drawing is hot workability. The temperature range in which RA is 60% or more is as low as 75 ° C, which is less than 100 ° C.
No. In No. 3, the Si content is 0.20%, which is less than the range of the present invention, and the peak hardness of the aging treatment is 53.8 HRC, which is lower than the 55 HRC of the present invention.
No. In No. 4, the Si content is 2.16%, which is higher than the range of the present invention, and the Ni _eq is 10.34, which is higher than 9.50 of the present invention. The workability of the throttle RA is as low as 50 ° C., which is less than the lower limit of 100 ° C. in the temperature range of 60% or more.
No. In No. 5, the Mn content was 1.17%, which was higher than the range of the present invention, and the Ni _eq was 9.80, which was higher than 9.50 in the present invention. The workability drawing RA is as low as 50 ° C., which is less than 100 ° C., which is the lower limit of the temperature range of 60% or more.
No. In No. 6, the Ni content is 3.61%, which is less than 4.00% of the range of the present invention, and the peak hardness of the aging treatment is 52.6 HRC, which is lower than 55 HRC in the present invention.
No. In 7, the Ni content was 9.52%, which was more than 9.00% of the range of the present invention, Ni _eq was higher than 9.50 in the present invention, 12.10, and the Ms points were 52 ° C and 100 ° C. It is less than low, does not satisfy the formula (1) and is not woven, and has a residual austenite amount (residual γ amount) of 5.2%, which is more than 1.0% specified in the present invention, and is a hot workability drawing. RA is as low as 75 ° C., which is less than the lower limit of 100 ° C. in the temperature range of 60% or more.
No. In No. 8, the Cr content is 4.03%, which is less than 8.00% of the range of the present invention, and the weather resistance is ×.
No. In No. 9, the Cr content is 14.88%, which is more than 14.50% of the range of the present invention, the hot workability is low, and the cost is increased.
No. In No. 10, the Mo content was 0.04%, which was less than 0.10% of the range of the present invention, and the Ni _eq was 9.51, which was slightly higher than 9.50 of the present invention, satisfying the formula (1). The temperature range in which the hot workability drawing RA is 60% or more is less than 100 ° C. and the temperature range is as low as 75 ° C.
No. In No. 11, the Mo content is 2.19%, which is higher than 2.00% of the present invention, the cost is high, the Ni _eq is 11.01, which is higher than 9.50 of the present invention, and the formula (1) is satisfied. Since there is no such thing, it is x, and the hot workability drawing RA is less than 100 ° C., which is the lower limit of the temperature range of 60% or more, and is as low as 50 ° C.
No. In No. 12, the Cu content is 0.32%, which is less than 0.50% of the present invention, and the peak hardness of the aging treatment is 53.2 HRC, which is lower than 55 HRC in the present invention.
No. In No. 13, the Cu content was 0.43%, which was higher than 4.00% of the present invention, and the Ni _eq was 9.85, which was higher than 9.50 of the present invention. The hot workability drawing RA is less than 100 ° C., which is the lower limit of the temperature at which it is 60% or more, and is as low as 75 ° C.
No. In No. 14, the Ti content is 0.12%, which is less than the lower limit of 0.50% of the _{present invention, and the Ni eq} is 10.31, which is higher than 9.50 of the present invention, and the formula (1) is satisfied. The peak hardness of the aging treatment is 52.9 HRC, which is lower than 55 HRC in the present invention, and the hot workability drawing RA is 50 ° C, which is less than the lower limit of the temperature range of 60% or more. Low.
No. In No. 15, the Ti content is 3.80%, which is higher than the upper limit of 3.50% of the _{present invention, and the Ni eq} is 10.00, which is higher than 9.50 in the present invention, and the formula (1) is satisfied. The hot workability of the throttle RA is less than 100 ° C., which is the lower limit of the temperature range of 60% or more, and is as low as 75 ° C.

Next, No. 2 of the comparative steel 2 corresponding to the second means. 16 to 21 will be described below.
No. In No. 16, the Al content is 0.186%, which is higher than the upper limit of 0.150% of the present invention. However, since the elements other than Al are within the specified range, Ni _eq , Cr _eq , Ms point, formula (1), formula (2), aging hardness (peak hardness), weather resistance, retained austenite. No particular effect was observed on the amount (residual γ amount) and the hot workability of the throttle RA.
No. In No. 17, the content of Nb is 2.09%, which is higher than the upper limit of 2.00% of the present invention. Therefore, Ni _eq is 9.52, which is slightly higher than 9.50 of the present invention, does not satisfy the formula (1), is ×, and the hot workability drawing RA is in the temperature range of 60% or more. It is less than the lower limit of 100 ° C and is as low as 75 ° C.
No. In No. 18, the content of N is 0.084%, which is higher than the upper limit of 0.050% of the present invention. Therefore, Ni _eq is 10.25, which is higher than 9.50 in the present invention, does not satisfy the formula (1), and is ×, and the hot workability throttle RA is the lower limit of the temperature range of 60% or more. It is less than 100 ° C and as low as 75 ° C.
No. In No. 19, the S content is 0.145%, which is higher than the upper limit of 0.100% in the present application. Therefore, the hot workability drawing RA is less than 100 ° C., which is the lower limit of the temperature range of 60% or more, and is extremely low at 25 ° C.
No. No. 20 has an Nb content of 2.14%, which is higher than the upper limit of 2.00% of the present invention. On the other hand, although it contains N, its content is within the range of 0.050% or less of the upper limit of the present invention. Therefore, Ni _eq is 9.67, which is higher than 9.50 of the present invention, does not satisfy the formula (1), is ×, and the hot workability throttle RA is the lower limit of the temperature range of 60% or more. It is less than 100 ° C and as low as 75 ° C.
No. In No. 21, the S content is 0.122%, which is more than the upper limit of 0.100% of the present invention, and Nb is contained, but the content is 1.69%, which is 0.01 to 2 of the present invention. In the range of .00%, N is further contained, but the content is more than 0.050%, which is the upper limit of the present application. Therefore, Ni _eq is 9.80, which is higher than 9.50 of the present invention, does not satisfy the formula (1), and is ×, and the hot workability throttle RA is at the lower limit of the temperature range of 60% or more. It is less than a certain 100 ° C and is extremely low at 25 ° C.

Next, No. 1 of the comparative steel 3 corresponding to the third means. 22 to 24 will be described.
No. In No. 22, the Ca content is 0.0312%, which is higher than the upper limit of 0.0250% of the present invention, and the B content is 0.0340%, which is higher than the upper limit of 0.0250% of the present invention. Therefore, the hot workability drawing RA is less than 100 ° C., which is the lower limit of the temperature range of 60% or more, and is as low as 75 ° C.
No. In No. 23, the Mg content is 0.0289%, which is higher than the upper limit of 0.0250% of the present invention. Therefore, the hot workability drawing RA is less than 100 ° C., which is the lower limit of the temperature range of 60% or more, and is as low as 75 ° C.
No. In No. 24, the Mg content is 0.0274%, which is higher than the upper limit of 0.0250% of the present invention, and the B content is 0.0340%, which is higher than the upper limit of 0.0250% of the present invention. Therefore, Ni _eq is 11.39, which is higher than the upper limit of 9.50 of the present invention, and the Ms point is as low as 92 ° C, which is lower than 106 ° C. The residual austenite amount (residual γ amount) is 2.7%, which exceeds 1.0% specified in the present invention, and the hot workability drawing RA is 100 ° C., which is the lower limit of the temperature range of 60% or more. It is less than 50 ° C and as low as 50 ° C.

Finally, No. 1 of the comparative steel 4 corresponding to the fourth means. 25 to 30 will be described.
No. In 25, the Al content is 0.099%, which is within the range of 0.150% or less of the upper limit of the present invention, and the Nb content is 0.92%, which is 2.00% or less of the upper limit of the present invention. Within the range of, the content of B is 0.0401%, which exceeds the upper limit of 0.0250% of the _{present invention, and Ni eq} is 12.12, which is higher than the upper limit of 9.50 of the present invention. It does not satisfy the formula (1) and is ×, and the hot workability drawing RA is less than 100 ° C., which is the lower limit of the temperature range of 60% or more, and is as low as 75 ° C.
No. No. 26 does not contain Al, Ca is 0.0052%, which is in the range of 0.0001 to 0.0250% of the present invention, but Mg is 0.0290%, which is the upper limit of 0 of the present invention. More than .0250%, the hot workability drawing RA is less than 100 ° C, which is the lower limit of the temperature range of 60% or more, and is as low as 75 ° C.
No. In 27, the Al content is 0.083%, which is within the range of 0.150% of the upper limit of the present invention, and N is 0.041%, which is within the range of 0.002 to 0.050% of the present invention. However, since Mg is 0.0267%, which is higher than the upper limit of 0.0250% of the present invention, the hot workability drawing RA is less than 100 ° C., which is the lower limit of the temperature range of 60% or more. It is as low as 50 ° C.
No. No. 28 has an S content of 0.089%, which is in the range of 0.001 to 0.100% of the present invention, and an Al content of 0.041%, which is 0.001 to 0.150% of the present invention. Although within the range, Ca is 0.0361%, which is higher than the upper limit of 0.0250% of the present invention. Therefore, Ni _eq is 11.21, which is higher than the upper limit of 9.50 of the present invention, does not satisfy the formula (1), is ×, and the hot workability throttle RA is the lower limit of the temperature range of 60% or more. It is less than 100 ° C, which is a value, and is as low as 50 ° C.
No. In No. 29, the S content was 0.026%, which was in the range of 0.001 to 0.100% of the present invention, the Al content was not, and the Nb content was 0.20%, which was 0. Within the range of 01 to 2.00%, Mg is 0.0213% and 0.01 to 2.00% of the present invention, and B is 0.0274%, which is the upper limit of the present invention. More than 0250%. Therefore, Ni _eq is 11.90, which is higher than the upper limit of 9.50 of the present invention, does not satisfy the formula (1), is ×, and the hot workability throttle RA is the lower limit of the temperature range of 60% or more. It is less than the value of 100 ° C and is as low as 75 ° C.
No. In No. 30, the S content was 0.047% and 0.001 to 0.100% of the present invention, Al was 0.186% and 0.001 to 0.150% of the present invention, and Ca was 0.0284. % Is more than 0.0250% of the upper limit of the present invention, and Mg is 0.0316%, which is more than 2.00% of the upper limit of the present invention, but B is 0.0034%, which is 0. It is in the range of 0001 to 0.0250%. Therefore, the hot workability drawing RA is less than 100 ° C., which is the lower limit of the temperature range of 60% or more, and is extremely low at 25 ° C.

Claims (4)

By mass%, C: 0.01 to 0.10%, Si: 0.30 to 2.00%, Mn: 0.01 to 1.00%, Ni: 4.00 to 9.00%, Cr: It contains 8.01 to 14.50%, Mo: 0.10 to 2.00%, Cu: 0.50 to 4.00%, Ti: 0.50 to 3.50%, and the balance Fe and unavoidable impurities. The temperature at which the hardness is 55 HRC or more, the residual austenite amount is 1% or less, and the drawing is 60% or more in the hot tensile test (greeble test) is 100, which satisfies the following formulas (1) and (2). High hardness precipitation hardening stainless steel with excellent manufacturability, which is characterized by a temperature of ℃ or higher.
5.00 ≤ Ni _eq ≤ 9.50 ... Equation (1)
Ni _eq ≤ -0.83 x Cr _eq + 25.5 ... Equation (2)
However, Ni _eq = [% Ni] + 30 × ([% C] + [% N]) + 0.5 × [% Mn] + 0.3 × [% Cu], and Cr _eq = [% Cr] + [% Mo] +1.5 x [% Si] +0.5 x [% Nb].
In each of the above [% M], the numerical value (mass%) of the content of the corresponding element is substituted. In addition to the chemical composition of claim 1, by mass%, Al: 0.001 to 0.150%, Nb: 0.01 to 2.00%, N: 0.002 to 0.050%, and S :. It contains any one or more selected from 0.001 to 0.100%, but the Cr in the chemical component of claim 1 is Cr: 8.00 to less than 13.00%. , Remaining Fe and unavoidable impurities, satisfying the following formulas (1) and (2), hardness is 55HRC or more, residual austenite amount is 1% or less, and drawing 60% in hot tensile test (greeble test). A high-hardness precipitation-hardened stainless steel with excellent manufacturability, characterized in that the above temperature is 100 ° C. or higher.
5.00 ≤ Ni _eq ≤ 9.50 ... Equation (1)
Ni _eq ≤ -0.83 x Cr _eq + 25.5 ... Equation (2)
However, Ni _eq = [% Ni] + 30 × ([% C] + [% N]) + 0.5 × [% Mn] + 0.3 × [% Cu], and Cr _eq = [% Cr] + [% Mo] +1.5 × [% Si] +0.5 × [% Nb].
In each of the above [% M], the numerical value (mass%) of the content of the corresponding element is substituted. Any one selected from Ca: 0.0001 to 0.0250%, Mg: 0.0001 to 0.0250%, and B: 0.0001 to 0.0250% in mass% in addition to the chemical component of claim 1. It contains one or more kinds of steel, and consists of the balance Fe and unavoidable impurities, which satisfies the following formulas (1) and (2), has a hardness of 55HRC or more, a residual austenite amount of 1% or less, and is hot. High hardness precipitation hardening stainless steel with excellent manufacturability, characterized in that the temperature at which the drawing is 60% or more in the tensile test (greeble test) is 100 ° C. or higher.
5.00 ≤ Ni _eq ≤ 9.50 ... Equation (1)
Ni _eq ≤ -0.83 x Cr _eq + 25.5 ... Equation (2)
However, Ni _eq = [% Ni] + 30 × ([% C] + [% N]) + 0.5 × [% Mn] + 0.3 × [% Cu], and Cr _eq = [% Cr] + [% Mo] +1.5 × [% Si] +0.5 × [% Nb].
In each of the above [% M], the numerical value (mass%) of the content of the corresponding element is substituted. In addition to the chemical component of claim 1, in mass%, Al: 0.001 to 0.150%, Nb: 0.01 to 2.00%, N: 0.002 to 0.050%, S: 0. It contains any one or more selected from 001 to 0.100%, and further, Ca: 0.0001 to 0.0250%, Mg: 0.0001 to 0.0250%, B: 0. It contains any one or more selected from 0001 to 0.0250%, consists of the balance Fe and unavoidable impurities, satisfies the formulas (1) and (2) described below, and has a hardness of 55HRC. As described above, a high hardness precipitation hardening stainless steel having excellent manufacturability, characterized in that the amount of retained austenite is 1% or less and the temperature at which the drawing is 60% or more in the hot tensile test (greeble test) is 100 ° C. or more.
5.00 ≤ Ni _eq ≤ 9.50 ... Equation (1)
Ni _eq ≤ -0.83 x Cr _eq + 25.5 ... Equation (2)
However, Ni _eq = [% Ni] + 30 × ([% C] + [% N]) + 0.5 × [% Mn] + 0.3 × [% Cu], and Cr _eq = [% Cr] + [% Mo] +1.5 × [% Si] +0.5 × [% Nb].
The numerical value (mass%) of the content of the corresponding element is substituted into the above [% M].