JP7513862B2 - Chemicals for heat treatment of stainless steel, heat-treated stainless steel member, and method for producing heat-treated stainless steel member - Google Patents

Description

The present invention relates to a chemical for heat treating stainless steel, a heat treated stainless steel component, and a method for manufacturing a heat treated stainless steel component.

Stainless steel is processed into a shape close to the intended product by hot working the ingot, which has been cast in a desired shape, at temperatures above the recrystallization temperature. In hot working, in order to control the characteristics, dimensional accuracy, and shape of the products, it is necessary to keep the temperature difference between materials and between parts of the material small, and so stainless steel tends to be heated for long periods of time in a heating furnace.

As a result, high-temperature heating causes uneven and localized oxidation (hereinafter collectively referred to as "abnormal oxidation") to occur on the surface of the stainless steel. This not only deteriorates the surface properties, but also causes the problem of reduced yields due to a reduction in the product area.

For this reason, methods have been studied that suppress abnormal oxidation by applying a chemical agent to the surface of the steel before hot working to form a scale of uniform thickness. For example, Patent Document 1 discloses an oxidation prevention paint for steel that is applied to steel materials (slabs) such as nickel steel to prevent the formation of oxidized scale in high-temperature oxidizing atmospheres such as a soaking furnace.

Japanese Patent Application Laid-Open No. 11-222564

However, the antioxidant paint described in Patent Document 1 is insufficient in preventing abnormal oxidation of stainless steel.

Stainless steel is characterized by a beautiful metallic luster on the surface, and particularly excellent surface properties are required. For this reason, it is desirable that no thick scale remains when the product is in use. However, if dense scale is formed during the heat treatment associated with hot working and is firmly attached to the stainless steel base material, it is necessary to thoroughly perform shot blasting or pickling to remove the scale.

In particular, when shot blasting components with complex shapes, the surface properties and characteristics of the surface layer vary depending on the part of the stainless steel base material. In addition, the waste liquid after pickling has a large environmental impact, and treating the waste liquid increases costs.

The present invention aims to solve the above problems and provide a stainless steel heat treatment agent that can be used to manufacture stainless steel heat treated components with excellent surface properties, suppress abnormal oxidation during heat treatment, and easily remove scale after cooling.

The present invention has been made to solve the above problems, and is summarized as follows: The stainless steel heat treatment agent, stainless steel heat treatment member, and method for manufacturing stainless steel heat treatment member.

(1) Contains chromium oxide;
After being applied to the surface of the stainless steel material,
A stainless steel heat treatment agent used in applications where the stainless steel is heated and held at a temperature in the range of 1200 to 1300°C in an atmosphere with an _O2 concentration of more than 0% by volume,
The chemical composition of the stainless steel material is, in mass%,
Mn: 6.0% or less;
The Cr content in the stainless steel heat treatment agent and the Cr content in the stainless steel material satisfy the following formula (i):
Chemicals for heat treatment of stainless steel.
_MCrB / _MCrF ≦ 1.0 (i)
In the above formula (i), the meanings of the symbols are as follows:
M _CrB : Cr content of stainless steel material (mass%)
M _CrF : Cr content (mass%) of the stainless steel heat treatment agent

(2) The average particle size of the chromium oxide is 50 μm or less.
The agent for heat treatment of stainless steel according to (1) above.

(3) The chemical composition of the stainless steel material is, in mass%,
C: 0.001 to 0.080%,
Si: 0.01 to 1.50%,
Mn: 0.1 to 6.0%,
P: 0.050% or less,
S: 0.030% or less; and Cr: 15.0 to 25.0%;
2. A stainless steel heat treatment agent according to claim 1, wherein the stainless steel heat treatment agent is a fluorine-containing compound.

(4) The chemical composition of the stainless steel material is, in mass%,
C: 0.001 to 0.060%,
Si: 0.01 to 1.50%,
Mn: 0.1 to 6.0%,
P: 0.050% or less,
S: 0.0050% or less,
Cr: 19.0 to 25.0%,
Ni: 1.0 to 6.0%,
N: 0.050 to 0.25%,
Al: 0.003 to 0.050%,
Ti: 0 to 0.050%,
Nb: 0 to 0.15%,
Mo: 0 to 2.0%,
Cu: 0 to 3.0%,
W: 0 to 2.0%,
Mg: 0 to 0.0050%,
Ca: 0 to 0.0050%,
REM: 0 to 0.30%,
B: 0 to 0.0040%,
The balance is Fe and impurities.
The agent for heat treatment of stainless steel according to (3) above.

(5) The chemical composition of the stainless steel material is, in mass%,
C: 0.001 to 0.080%,
Si: 0.01 to 1.0%,
Mn: 0.1 to 2.0%,
P: 0.045% or less,
S: 0.030% or less,
Cr: 18.0 to 22.0%,
Ni: 8.0 to 14.0%,
N: 0.50% or less,
Al: 0.003 to 0.050%,
Ti: 0 to 0.050%,
Nb: 0 to 0.15%,
Mo: 0 to 3.0%,
Cu: 0 to 3.0%,
W: 0 to 2.0%,
Mg: 0 to 0.0050%,
Ca: 0 to 0.0050%,
REM: 0 to 0.30%,
B: 0 to 0.0040%,
The balance is Fe and impurities.
The agent for heat treatment of stainless steel according to (3) above.

(6) The chemical composition of the stainless steel material is, in mass%,
C: 0.001 to 0.080%,
Si: 0.01 to 1.0%,
Mn: 0.1 to 1.0%,
P: 0.040% or less,
S: 0.030% or less,
Cr: 16.0 to 25.0%,
Ni: 1.0% or less,
N: 0.6% or less,
Al: 0.003 to 0.2%,
Ti: 0 to 0.50%,
Nb: 0 to 0.7%,
Mo: 0 to 2.0%,
Cu: 0 to 1.0%,
W: 0 to 2.0%,
Mg: 0 to 0.0050%,
Ca: 0 to 0.0050%,
REM: 0 to 0.30%,
B: 0 to 0.0040%,
The balance is Fe and impurities.
The agent for heat treatment of stainless steel according to (3) above.

(7) A stainless steel substrate having a stainless steel base material and a scale formed on at least a portion of a surface of the stainless steel base material,
In the concentration profile in the depth direction of the scale, the Cr content repeats maximum and minimum values two or more times;
The chemical composition of the stainless steel base material is, in mass%,
Mn: 6.0% or less;
Stainless steel heat treated components.

(8) The chemical composition of the scale at the depth position where the Cr content is maximum is, in mass%,
Cr: 20.0 to 40.0%,
Fe: 10.0 to 35.0%,
Mn: 0 to 10.0%, and
The chemical composition of the scale at the depth position where the Cr content is minimal is, in mass%,
Cr: 0 to 20.0%,
Fe: 30.0 to 60.0%,
Mn: 0 to 10.0%.
The heat-treated stainless steel member according to (7) above.

(9) The chemical composition of the stainless steel base material is, in mass%,
C: 0.001 to 0.080%,
Si: 0.01 to 1.50%,
Mn: 0.1 to 6.0%,
P: 0.050% or less,
S: 0.030% or less; and Cr: 15.0 to 25.0%;
The heat-treated stainless steel member according to (7) or (8) above.

(10) The chemical composition of the stainless steel base material is, in mass%,
C: 0.001 to 0.060%,
Si: 0.01 to 1.50%,
Mn: 0.1 to 6.0%,
P: 0.050% or less,
S: 0.0050% or less,
Cr: 19.0 to 25.0%,
Ni: 1.0 to 6.0%,
N: 0.050 to 0.25%,
Al: 0.003 to 0.050%,
Ti: 0 to 0.050%,
Nb: 0 to 0.15%,
Mo: 0 to 2.0%,
Cu: 0 to 3.0%,
W: 0 to 2.0%,
Mg: 0 to 0.0050%,
Ca: 0 to 0.0050%,
REM: 0 to 0.30%,
B: 0 to 0.0040%,
The balance is Fe and impurities.
The heat-treated stainless steel member according to (9) above.

(11) The chemical composition of the stainless steel base material is, in mass%,
C: 0.001 to 0.080%,
Si: 0.01 to 1.0%,
Mn: 0.1 to 2.0%,
P: 0.045% or less,
S: 0.030% or less,
Cr: 18.0 to 22.0%,
Ni: 8.0 to 14.0%,
N: 0.50% or less,
Al: 0.003 to 0.050%,
Ti: 0 to 0.050%,
Nb: 0 to 0.15%,
Mo: 0 to 3.0%,
Cu: 0 to 3.0%,
W: 0 to 2.0%,
Mg: 0 to 0.0050%,
Ca: 0 to 0.0050%,
REM: 0 to 0.30%,
B: 0 to 0.0040%,
The balance is Fe and impurities.
The heat-treated stainless steel member according to (9) above.

(12) The chemical composition of the stainless steel base material is, in mass%,
C: 0.001 to 0.080%,
Si: 0.01 to 1.0%,
Mn: 0.1 to 1.0%,
P: 0.040% or less,
S: 0.030% or less,
Cr: 16.0 to 25.0%,
Ni: 1.0% or less,
N: 0.6% or less,
Al: 0.003 to 0.2%,
Ti: 0 to 0.50%,
Nb: 0 to 0.7%,
Mo: 0 to 2.0%,
Cu: 0 to 1.0%,
W: 0 to 2.0%,
Mg: 0 to 0.0050%,
Ca: 0 to 0.0050%,
REM: 0 to 0.30%,
B: 0 to 0.0040%,
The balance is Fe and impurities.
The heat-treated stainless steel member according to (9) above.

(13) For the stainless steel material according to any one of (1) to (6) above,
(a) applying a stainless steel heat treatment agent according to any one of (1) to (6) above to a surface;
(b) heating and holding the material at a temperature in the range of 1200 to 1300 ° C. in an atmosphere having an O ₂ concentration of more than 0% by volume;
(c) cooling to room temperature.
A method for manufacturing a heat-treated stainless steel component.

(14) In the step (c), after the hot working, the steel is cooled to room temperature.
A method for producing a heat-treated stainless steel member according to (13) above.

By using the stainless steel heat treatment agent of the present invention, it is possible to obtain heat-treated stainless steel components with excellent surface properties.

1 is a cross-sectional SEM photograph of a stainless steel base material and a scale.

The inventors conducted detailed studies into methods for simultaneously suppressing abnormal oxidation that occurs when stainless steel is heated and improving the peelability of scale that forms on the surface of the stainless steel, and as a result, they came to the following findings.

It _was discovered that by applying a chemical agent mainly composed of _Cr2O3 to the surface of stainless steel and then heating it at high temperature for a long time, a scale with a layered structure in which two or more layers with different oxide compositions are stacked (hereinafter also referred to as "layered scale") is formed. The presence of layered scale on the surface of stainless steel moderately suppresses the intrusion and diffusion of oxygen during heating and holding, suppressing abnormal oxidation.

It was also found that the layered scale easily peels off from the stainless steel base material during cooling after heat treatment. It is believed that the difference in thermal contraction during cooling, due in part to the difference in thermal expansion of each layer with a different oxide composition, causes the scale to easily peel off. The mechanism by which layered scale forms is currently under active investigation.

The present invention was made based on the above findings. Each of the requirements of the present invention will be described in detail below. In the present invention, the stainless steel before heat treatment is called the stainless steel material, and the stainless steel after heat treatment is called the stainless steel heat-treated member.

1. Chemical agent for heat treatment of stainless steel The chemical agent for heat treatment of stainless steel according to the present invention (hereinafter, simply referred to as "chemical agent") is used for applications in which the chemical agent is applied to the surface of a stainless steel material and then heated and maintained under predetermined conditions. The heating and maintaining conditions will be described later.

The agent of the present invention also contains chromium oxide. In order to form the above-mentioned layered scale, the Cr content in the agent needs to be adjusted in relation to the Cr content in the stainless steel material, and specifically, the following formula (i) needs to be satisfied:
_MCrB / _MCrF ≦ 1.0 (i)
In the above formula (i), the meanings of the symbols are as follows:
M _CrB : Cr content of stainless steel material (mass%)
M _CrF : Cr content (mass%) of the stainless steel heat treatment agent

By applying the above-mentioned agent to the surface of the stainless steel material, a layer of scale is formed on the surface of the stainless steel material, even if it is heated for a long time, and the occurrence of abnormal oxidation is suppressed. In addition, as mentioned above, the formed layer of scale has the property of being easily peeled off, and most of it peels off easily during cooling. Therefore, it is possible to omit shot blasting or pickling to remove the scale.

Furthermore, there is a problem that scale typically peels off during hot rolling and is pressed into the surface of the steel plate or the like, causing defects (hereinafter also referred to as "scale defects"), which increases the workload of surface grinding and other operations. However, it has been discovered that by using the agent of the present invention, it is possible to unexpectedly prevent scale defects.

In order for the Cr content in the agent to satisfy the above formula (i), the content of chromium oxide contained in the agent is preferably 30% or more by mass. In addition, the agent may contain silicon oxide, sodium oxide, aluminum oxide, etc. as components other than chromium oxide. The content of silicon oxide is preferably 60% or less, and the content of sodium oxide and aluminum oxide is preferably 10% or less.

The average particle size of the chromium oxide contained in the agent is preferably 50 μm or less. By making the average particle size 50 μm or less, it becomes easier to control the amount of oxygen that penetrates and diffuses into the surface of the stainless steel material while it is heated, and the adhesive strength with the material and the reactivity between the agents themselves can be maintained.

2. Stainless steel material The chemical composition of the stainless steel material on whose surface the agent of the present invention is applied contains 6.0% or less Mn by mass. Mn is an element that is more easily oxidized than Cr, and is also an element that easily diffuses in the oxides of Fe and Cr that are generated during heating. Therefore, if the Mn content exceeds 6.0%, the amount of oxides such as _MnCr2O4 generated becomes excessive, and _layered scale cannot be obtained. Therefore, the Mn content in the stainless steel material is limited to 6.0% or less.

There are no particular restrictions on the content of elements other than Mn, so long as it is stainless steel. For example, the chemical composition of stainless steel material should preferably contain, in mass percent, C: 0.001-0.080%, Si: 0.01-1.50%, Mn: 0.1-6.0%, P: 0.050% or less, S: 0.030% or less, and Cr: 15.0-25.0%.

The term "impurities" as used herein refers to components that are mixed in during the industrial production of steel due to various factors in the manufacturing process, such as raw materials such as ores and scraps, and that are acceptable within the scope of not adversely affecting the present invention.

Furthermore, the chemical composition of the above stainless steel materials can be broadly divided into three types: (a) duplex stainless steel, (b) austenitic stainless steel, and (c) ferritic stainless steel.

(a) The preferred chemical composition of duplex stainless steel is, in mass%, C: 0.001-0.060%, Si: 0.01-1.50%, Mn: 0.1-6.0%, P: 0.050% or less, S: 0.0050% or less, Cr: 19.0-25.0%, Ni: 1.0-6.0%, N: 0.050-0.25%, Al: 0.003-0.050%, Ti: 0-0.050%, Nb: 0-0.15%, Mo: 0-2.0%, Cu: 0-3.0%, W: 0-2.0%, Mg: 0-0.0050%, Ca: 0-0.0050%, REM: 0-0.30%, B: 0-0.0040%, balance: Fe and impurities.

(b) The preferred chemical composition of austenitic stainless steel is, in mass %, C: 0.001-0.080%, Si: 0.01-1.0%, Mn: 0.1-2.0%, P: 0.045% or less, S: 0.030% or less, Cr: 18.0-22.0%, Ni: 8.0-14.0%, N: 0.50% or less, Al: 0.003-0.050%, Ti: 0-0.050%, Nb: 0-0.15%, Mo: 0-3.0%, Cu: 0-3.0%, W: 0-2.0%, Mg: 0-0.0050%, Ca: 0-0.0050%, REM: 0-0.30%, B: 0-0.0040%, balance: Fe and impurities.

(c) The preferred chemical composition of ferritic stainless steel is, in mass %, C: 0.001-0.080%, Si: 0.01-1.0%, Mn: 0.1-1.0%, P: 0.040% or less, S: 0.030% or less, Cr: 16.0-25.0%, Ni: 1.0% or less, N: 0.6% or less, Al: 0.003-0.2%, Ti: 0-0.50%, Nb: 0-0.7%, Mo: 0-2.0%, Cu: 0-1.0%, W: 0-2.0%, Mg: 0-0.0050%, Ca: 0-0.0050%, REM: 0-0.30%, B: 0-0.0040%, balance: Fe and impurities.

3. Heat-treated stainless steel component The heat-treated stainless steel component according to the present invention comprises a stainless steel base material and a scale formed on at least a portion of the surface of the stainless steel base material. Here, the scale formed on the surface of the stainless steel base material refers to scale that is generated during heat treatment and does not peel off even after cooling and remains partially.

The above-mentioned stainless steel heat-treated component is obtained by applying the agent according to the present invention to the surface of the stainless steel material, and then heating and holding it under specified conditions. As described above, a scale having a layered structure is formed by applying the agent according to the present invention to the surface of the stainless steel material and heating it at a high temperature for a long period of time.

Figure 1 shows a scanning electron microscope (SEM) photograph of the cross section of the stainless steel base material and scale. As shown in Figure 1, the scale 2 formed on the surface of the stainless steel base material 1 has a layered structure, with layers 21 with a relatively high Cr content and layers 22 with a low Cr content alternately stacked. In other words, the scale formed on the surface of the stainless steel base material has a concentration profile in the depth direction in which the Cr content alternates between maximum and minimum values two or more times.

The chemical composition of the scale at the depth position where the Cr content is maximum is, in mass %, Cr: 20.0-40.0%, Fe: 10.0-35.0%, Mn: 0-10.0%, and the chemical composition of the scale at the depth position where the Cr content is minimum is, in mass %, Cr: 0-20.0%, Fe: 30.0-60.0%, Mn: 0-10.0%.

The chemical composition of the scale can be measured by cutting out a sample so that the cross section of the scale can be observed, and then using the energy dispersive X-ray analysis (EDS) provided with the SEM. More specifically, a line analysis using EDS can be performed to determine the concentration profile of each element.

There are no particular limitations on the thickness of the scale. However, the thickness of the scale formed under the manufacturing conditions described below is approximately 10 μm for the layers with a relatively high Cr content and the layers with a relatively low Cr content, with a total thickness of approximately 40 to 300 μm.

Since the stainless steel heat-treated component is obtained by subjecting the above-mentioned stainless steel material to heat treatment, the chemical composition of the stainless steel base material is the same as that of the stainless steel material. In other words, the Mn content in the stainless steel base material is 6.0% or less. The contents of other elements are also the same as those of the stainless steel material, so explanations are omitted.

4. Manufacturing method of heat-treated stainless steel member The manufacturing conditions of the heat-treated stainless steel member according to the present invention will be described. In the manufacturing method of the heat-treated stainless steel member according to one embodiment of the present invention, the stainless steel material is subjected to the following steps in order: (a) applying the above-mentioned agent, (b) heating and holding the temperature in the range of 1200 to 1300°C in an atmosphere with an _O2 concentration of more than 0% by volume, and (c) cooling to room temperature.

(a) Coating Step There are no particular limitations on the method for coating the chemicals onto the stainless steel material. For example, a known method may be used in which the chemicals are mixed with water to form a paste and then coated uniformly onto the material.

There is also no particular limit to the amount of agent applied, but it is preferably in the range of 50 to 200 mg/ ^cm2 . By applying an amount of 50 mg/ ^cm2 or more, sufficient antioxidant ability can be obtained. On the other hand, by applying an amount of 200 mg/ ^cm2 or less, it is possible to prevent cracks from occurring in the coating, which allows oxygen to penetrate.

(b) Heating and holding step Next, the stainless steel material coated with the agent is heated and held at a temperature range of 1200 to 1300 ° C in an atmosphere with an O ₂ concentration of more than 0 vol%. By heating in an environment where oxygen is present, a layered scale is formed. Since the presence of oxygen is sufficient even in small amounts, the O ₂ concentration needs to be more than 0 vol%, but it is preferable that it is 1 vol% or more.

In addition, since the amount of oxygen on the surface of the stainless steel material is controlled by the agent, there is no need to specifically limit the upper limit of the oxygen concentration in the environment. However, if the oxygen concentration is too high, the amount of oxygen entering the agent cannot be properly controlled, and the desired layered scale may not be obtained, so it is preferable to set it to, for example, 20% by volume or less.

If the heating temperature is less than 1200°C, the amount of oxygen entering the material cannot be properly controlled, resulting in a single-layer scale, and layered scale is not formed. On the other hand, if the heating temperature exceeds 1300°C, the antioxidant ability of the agent decreases, abnormal oxidation occurs, and layered scale is not obtained.

Here, "holding" means that the temperature needs to remain within the above temperature range even for a short period of time. In other words, the heating holding time is more than 0 seconds. However, from the viewpoint of minimizing temperature differences between materials and between parts of the material, the heating holding time is preferably 1 hour or more, and more preferably 5 hours or more.

(c) Cooling step: The heat-treated stainless steel component after the heating is cooled to room temperature. There is no particular limitation on the cooling method, and air cooling or water cooling may be used. In addition, the stainless steel material after the heating may be subjected to hot working and then cooled to room temperature.

The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples.

Stainless steels (steel types A to D) having the chemical compositions shown in Table 1 were melted and billets with a cross section of 130 mm x 130 mm and a length of 2000 mm were prepared (Tests No. 1 to 8). Then, except for Test No. 8, 50 mg/ ^cm2 of a chemical agent having the components shown in Table 2 was applied to the black surface of the billet. Then, each billet was heated and held under the conditions shown in Table 3, and then cooled to room temperature by air cooling to obtain test materials. The heating and holding atmosphere was set to an _O2 concentration of 2 volume%, an _H2O concentration of 20 volume%, and an _N2 concentration of 78 volume%.

Test pieces were then cut out so that the cross section of the scale formed on the surface of each test material could be observed, and the chemical composition of the scale was analyzed using SEM and EDS. Specifically, first, SEM observation was used to confirm whether the scale had a layered structure or was a single layer, and the thickness was measured. In addition, if the scale had a layered structure, line analysis was performed in the depth direction using EDS to determine the Cr concentration profile.

In Table 3, for all samples evaluated as "layered", the Cr content alternated between maximum and minimum values two or more times in the concentration profile in the depth direction. The chemical composition was measured at three points at each of the depth positions where the Cr content was maximum and minimum, and the average was calculated. On the other hand, when the scale was a single layer, the chemical composition was measured at three arbitrary points and the average was calculated. The results are also shown in Table 3.

Furthermore, using each of the obtained test materials, the occurrence of abnormal oxidation was investigated and the scale peeling property was evaluated. The occurrence of abnormal oxidation was investigated using the following procedure. First, a cross section perpendicular to the surface was cut out so that the length of the surface of the test material after cooling was 20 mm, and embedded in resin. The cross section was then polished and observed, and it was determined that abnormal oxidation had occurred in the area where oxidation had progressed to a depth five times or more deeper than the other areas. If no abnormal oxidation was observed, the evaluation was rated as ◯, and if abnormal oxidation occurred in even one place, the evaluation was rated as ×.

In addition, the surface of the test material after cooling was observed and the remaining scale rate was measured to evaluate the scale removability. Specifically, if the remaining scale rate was less than 10%, the scale removability was rated as good (◯), and if it was 10% or more, the scale removability was rated as poor (×). The results are shown in Table 3.

As shown in Table 3, when the specifications of the present invention were satisfied, layered scale was formed, abnormal oxidation was prevented, and the scale strippability was excellent. On the other hand, in Test No. 5, in which the Mn content in the stainless steel material was excessive, the amount of _MnCr2O4 produced was excessive, _and layered scale could not be obtained. As a result, abnormal oxidation occurred and the scale strippability was poor.

In addition, in Test No. ₆ , where the heating temperature was low, the scale was a single layer of chromium oxide, resulting in poor scale removal properties. Furthermore, in Test No. 7, where a chemical agent not containing _Cr2O3 was used, and Test No. 8, where no chemical agent was used, no oxidation prevention ability was obtained and thick scale mainly composed of Fe was formed. As a result, abnormal oxidation occurred and scale removal properties were poor.

By using the stainless steel heat treatment agent of the present invention, it is possible to obtain heat-treated stainless steel components with excellent surface properties.

1. Stainless steel base material 2. Scale 21. Layer with high Cr content 22. Layer with low Cr content

Claims (12)

In mass percent,
up to 60% silicon oxide,
Not more than 10% sodium oxide, and
Contains 10% or less aluminum oxide,
the balance being 30% or more of chromium oxide and impurities;
The average particle size of the chromium oxide is 50 μm or less,
After being applied to the surface of the stainless steel material,
A stainless steel heat treatment agent used in applications where the stainless steel is heated and held at a temperature in the range of 1200 to 1300°C in an atmosphere with an _O2 concentration of more than 0% by volume and not more than 20% by volume,
The chemical composition of the stainless steel material is, in mass%,
Mn: 6.0% or less;
The Cr content in the stainless steel heat treatment agent and the Cr content in the stainless steel material satisfy the following formula (i):
Chemicals for heat treatment of stainless steel.
_MCrB / _MCrF ≦ 1.0 (i)
In the above formula (i), the meanings of the symbols are as follows:
M _CrB : Cr content of stainless steel material (mass%)
M _CrF : Cr content (mass%) of the stainless steel heat treatment agent The chemical composition of the stainless steel material is, in mass%,
C: 0.001 to 0.080%,
Si: 0.01 to 1.50%,
Mn: 0.1 to 6.0%,
P: 0.050% or less,
S: 0.030% or less; and Cr: 15.0 to 25.0%;
The agent for heat treating stainless steel according to claim 1. The chemical composition of the stainless steel material is, in mass%,
C: 0.001 to 0.060%,
Si: 0.01 to 1.50%,
Mn: 0.1 to 6.0%,
P: 0.050% or less,
S: 0.0050% or less,
Cr: 19.0 to 25.0%,
Ni: 1.0 to 6.0%,
N: 0.050 to 0.25%,
Al: 0.003 to 0.050%,
Ti: 0 to 0.050%,
Nb: 0 to 0.15%,
Mo: 0 to 2.0%,
Cu: 0 to 3.0%,
W: 0 to 2.0%,
Mg: 0 to 0.0050%,
Ca: 0 to 0.0050%,
REM: 0 to 0.30%,
B: 0 to 0.0040%,
The balance is Fe and impurities.
The agent for heat treating stainless steel according to claim 2. The chemical composition of the stainless steel material is, in mass%,
C: 0.001 to 0.080%,
Si: 0.01 to 1.0%,
Mn: 0.1 to 2.0%,
P: 0.045% or less,
S: 0.030% or less,
Cr: 18.0 to 22.0%,
Ni: 8.0 to 14.0%,
N: 0.50% or less,
Al: 0.003 to 0.050%,
Ti: 0 to 0.050%,
Nb: 0 to 0.15%,
Mo: 0 to 3.0%,
Cu: 0 to 3.0%,
W: 0 to 2.0%,
Mg: 0 to 0.0050%,
Ca: 0 to 0.0050%,
REM: 0 to 0.30%,
B: 0 to 0.0040%,
The balance is Fe and impurities.
The agent for heat treating stainless steel according to claim 2. The chemical composition of the stainless steel material is, in mass%,
C: 0.001 to 0.080%,
Si: 0.01 to 1.0%,
Mn: 0.1 to 1.0%,
P: 0.040% or less,
S: 0.030% or less,
Cr: 16.0 to 25.0%,
Ni: 1.0% or less,
N: 0.6% or less,
Al: 0.003 to 0.2%,
Ti: 0 to 0.50%,
Nb: 0 to 0.7%,
Mo: 0 to 2.0%,
Cu: 0 to 1.0%,
W: 0 to 2.0%,
Mg: 0 to 0.0050%,
Ca: 0 to 0.0050%,
REM: 0 to 0.30%,
B: 0 to 0.0040%,
The balance is Fe and impurities.
The agent for heat treating stainless steel according to claim 2. A stainless steel base material and a scale formed on at least a portion of a surface of the stainless steel base material,
In the concentration profile in the depth direction of the scale, the Cr content repeats maximum and minimum values two or more times;
The chemical composition of the scale at the depth position where the Cr content is maximum is, in mass%,
Cr: 20.0 to 40.0%,
Fe: 10.0 to 35.0%,
Mn: 0 to 10.0%, and
The chemical composition of the scale at the depth position where the Cr content is minimal is, in mass%,
Cr: 0 to 20.0%,
Fe: 30.0 to 60.0%,
Mn: 0 to 10.0%;
The residual rate of the scale is less than 10%,
The chemical composition of the stainless steel base material is, in mass%,
Mn: 6.0% or less;
Stainless steel heat treated components. The chemical composition of the stainless steel base material is, in mass%,
C: 0.001 to 0.080%,
Si: 0.01 to 1.50%,
Mn: 0.1 to 6.0%,
P: 0.050% or less,
S: 0.030% or less; and Cr: 15.0 to 25.0%;
7. The heat treated stainless steel component according to claim 6 . The chemical composition of the stainless steel base material is, in mass%,
C: 0.001 to 0.060%,
Si: 0.01 to 1.50%,
Mn: 0.1 to 6.0%,
P: 0.050% or less,
S: 0.0050% or less,
Cr: 19.0 to 25.0%,
Ni: 1.0 to 6.0%,
N: 0.050 to 0.25%,
Al: 0.003 to 0.050%,
Ti: 0 to 0.050%,
Nb: 0 to 0.15%,
Mo: 0 to 2.0%,
Cu: 0 to 3.0%,
W: 0 to 2.0%,
Mg: 0 to 0.0050%,
Ca: 0 to 0.0050%,
REM: 0 to 0.30%,
B: 0 to 0.0040%,
The balance is Fe and impurities.
8. The heat treated stainless steel component according to claim 7 . The chemical composition of the stainless steel base material is, in mass%,
C: 0.001 to 0.080%,
Si: 0.01 to 1.0%,
Mn: 0.1 to 2.0%,
P: 0.045% or less,
S: 0.030% or less,
Cr: 18.0 to 22.0%,
Ni: 8.0 to 14.0%,
N: 0.50% or less,
Al: 0.003 to 0.050%,
Ti: 0 to 0.050%,
Nb: 0 to 0.15%,
Mo: 0 to 3.0%,
Cu: 0 to 3.0%,
W: 0 to 2.0%,
Mg: 0 to 0.0050%,
Ca: 0 to 0.0050%,
REM: 0 to 0.30%,
B: 0 to 0.0040%,
The balance is Fe and impurities.
8. The heat treated stainless steel component according to claim 7 . The chemical composition of the stainless steel base material is, in mass%,
C: 0.001 to 0.080%,
Si: 0.01 to 1.0%,
Mn: 0.1 to 1.0%,
P: 0.040% or less,
S: 0.030% or less,
Cr: 16.0 to 25.0%,
Ni: 1.0% or less,
N: 0.6% or less,
Al: 0.003 to 0.2%,
Ti: 0 to 0.50%,
Nb: 0 to 0.7%,
Mo: 0 to 2.0%,
Cu: 0 to 1.0%,
W: 0 to 2.0%,
Mg: 0 to 0.0050%,
Ca: 0 to 0.0050%,
REM: 0 to 0.30%,
B: 0 to 0.0040%,
The balance is Fe and impurities.
8. The heat treated stainless steel component according to claim 7 . A method for producing a heat-treated stainless steel member according to any one of claims 6 to 10, comprising the steps of:
For the stainless steel material according to any one of claims 1 to 5,
(a) applying a stainless steel heat treatment agent according to any one of claims 1 to 5 to a surface;
(b) heating and holding the material at a temperature in the range of 1200 to 1300 ° C. in an atmosphere having an _O2 concentration of more than 0 vol.% and not more than 20 vol.%;
(c) cooling to room temperature.
A method for manufacturing a heat-treated stainless steel component. In the step (c), after the hot working, the steel is cooled to room temperature.
The method for producing the heat treated stainless steel component according to claim 11 .