TWI747722B - Matian bulk iron series stainless steel plate and matian bulk iron series stainless steel components - Google Patents

Abstract

The Matian scattered iron-based stainless steel plate of the present invention has C: 0.100~0.170%, Si: 0.30~0.60%, Mn: 0.10~0.60%, Cr: 11.0~15.0%, Ni: 0.05~0.60% in terms of mass% , Cu: 0.006~0.50%, V: 0.010~0.10%, Al: 0.05% or less, N: 0.040% or more and less than 0.060%, and C+1/2N: 0.130~0.190%, and as shown in formula (1) γp is 120 or more; after quenching and tempering the aforementioned Asada scattered iron stainless steel plate, the area ratio of δ Fe Fe (δFe) existing in the center of the plate thickness of the steel plate in the plate thickness section is less than 0.1%.

Description

Matian bulk iron series stainless steel plate and matian bulk iron series stainless steel components

The present invention relates to Asada scattered iron-based stainless steel plates and Asada scattered iron-based stainless steel components with excellent corrosion resistance after quenching. In more detail, the present invention relates to an Asada loose iron-based stainless steel, which has excellent corrosion resistance even if it is air-cooled for use in the manufacture of western-style food knives, looms, tools, disc brakes, and the like.

Western-style food knives (dining knives), scissors, looms, vernier calipers and other tools generally use Matian scattered iron stainless steel plates such as SUS420J1 and SUS420J2 steel. It is difficult to plate, paint, or use anti-rust oil in such applications, and the blank itself is required to have rust resistance. In addition, it is also very important that it is not easy to wear, so it must have high hardness.

The manufacturing steps of western food knives are usually die-cutting from steel plates, and after heating and quenching, they undergo grinding steps to make knives. The quenching step is mostly carried out under air cooling, which is also related to the characteristics of the Asada scattered iron stainless steel plate with excellent hardenability.

Document 1 (Japanese Patent Laid-Open No. 2008-163452) discloses Asada scattered iron-based stainless steel which is excellent in corrosion resistance when quenched by air cooling. Here, N is added to about 0.06% as an element that improves the corrosion resistance.

Document 2 (Japanese Patent Laid-Open No. 2005-163176) discloses steel to which N is further added. In addition, Document 3 (Japanese Patent Laid-Open No. 2005-248263) discloses the use of special equipment to further improve the N steel.

In recent years, with Europe as the center, the requirements for corrosion resistance of Western tableware are gradually increasing. As a result, in the rust resistance evaluation test, rust can be observed everywhere on the back or blade of the table knife, and the center of the grip, and it is required to improve the situation.

In recent years, as the requirements for corrosion resistance of Western tableware, centered on Europe, have increased, there has been a gradual increase in the need to improve the rust of the back or the edge of the knife and the center of the grip in the strict corrosion resistance test. The object of the present invention is to provide Asada loose iron stainless steel plates and Asada loose iron stainless steel components, which can be used for the use of Asada loose iron stainless steel such as table knives and other Western tableware, while maintaining sufficient hardness that can withstand use. And the end surface is excellent in corrosion resistance.

In order to achieve the above-mentioned purpose, the inventors of this case first investigated the rust condition of the table knife in detail. As a result, it is clearly shown that the rusted part is from the end face of the steel plate, more specifically, from the center of the thickness of the steel plate as the starting point. It was also confirmed that the delta ferrite phase (delta Fe phase) caused by macrosegregation was formed in the center of the thickness of the steel plate, and the mechanism of rusting was that the grain boundary of delta Fe became the accumulation site of carbides, and the carbides were being quenched. When it is heated and melted, and during subsequent cooling, grain boundary precipitation occurs, resulting in sensitization and grain boundary corrosion.

In addition, it was found that the rust is also related to the cooling rate during quenching. Although the cooling rate varies greatly depending on the quenching equipment, if the average cooling rate is evaluated from the quenching temperature to the temperature at which carbide precipitation is approximately 600°C, it can be seen that water quenching can achieve a cooling rate greater than 100°C/s. Therefore, it can inhibit the precipitation of carbides and is not easy to rust. However, in the air cooling commonly used in the manufacturing steps of table knives, the cooling rate is only about 5°C/s, which cannot inhibit the precipitation of carbides and is easy to rust.

The inventors of the present case studied the improvement method based on these knowledge and insights. As a result, they found that adding N to the composition of the steel sheet and optimizing the manufacturing steps made it unavoidable that there would be a certain degree of δFe reduction in the usual steps, and the The δFe in the steel is limited to a fixed amount, so that the rust can be suppressed in the Western-style cutting tool after forming and heat treatment.

Afterwards, further detailed discussions were conducted and the invention was finally completed.

That is, (1) A Matian scattered iron series stainless steel plate, characterized in that it has the following steel composition: Calculated by mass%, C: 0.100~0.170%, Si: 0.25~0.60%, Mn: 0.10~0.60%, P: Below 0.035%, S: 0.015% or less, Cr: 11.0~15.0%, Ni: 0.05~0.60%, Cu: 0.006~0.50%, V: 0.010~0.10%, Al: 0.05% or less, N: 0.040% or more and less than 0.060%, and C+1/2N: 0.130~0.190%, and the remainder is composed of Fe and impurities, and Γp shown in the following formula (1) is 120 or more; After maintaining the aforementioned Asada bulk iron stainless steel plate at 1050°C for 30 minutes and then performing air quenching and tempering at 150°C for 30 minutes, the δ Fe grain iron (δFe) present in the center of the plate thickness is The area ratio in the cross section is less than 0.1%. γp=420C+470N+30Ni+7Mn+9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-52Al+189　・・・　Equation (1) The element symbol in formula (1) means the content (mass%) of the element.

(2) The Matian scattered iron-based stainless steel plate as in (1), wherein the aforementioned steel composition replaces part of the aforementioned Fe and further contains one or more of the following elements: Calculated by mass%, Mo: 0.01~1.0%, Ti: 0.005~0.050% and Nb: 0.005~0.050%.

(3) The Matian scattered iron stainless steel plate as in (1) or (2), wherein the aforementioned steel composition replaces part of the aforementioned Fe and further contains one or two of the following elements: Calculated by mass%, Sn: 0.01~0.10%, Bi: 0.01~0.20%.

(4) A stainless steel component of Asada scattered iron series, having a steel composition as in any one of (1) to (3); The characteristics of the aforementioned Matian bulk iron series stainless steel components are: Γp shown in the aforementioned formula (1) is 120 or more; and, The area ratio of δ Fe grained iron (δFe) existing in the center of the plate thickness in the plate thickness section is less than 0.1%.

The Asada loose iron stainless steel plate of the present invention is used for the Asada loose iron stainless steel used in Western tableware such as table knives. It maintains sufficient hardness to withstand use, and has excellent corrosion resistance, especially end surface corrosion resistance. Therefore, when it is used as a Asada bulk iron-based stainless steel member such as Western-style food knives, it can also be expected to have the effect of improving the corrosion resistance and increasing the life of the product.

The form used to implement the invention Further details.

＜Chemical composition of steel plates and steel components＞ (% means mass%) C: 0.100~0.170% Both C and N are the elements that determine the quenching hardness. In order to obtain the required hardness of Western-style food knives, it must be more than 0.100%. And it should be more than 0.110%, more than 0.120%. On the other hand, if it is excessively added, the quenching hardness will increase above the required level. In addition to the increase in the load during grinding, the toughness will also decrease. In addition, even with the present invention, Cr carbides are still precipitated during air quenching and corrosion resistance is likely to be impaired, so it is set to 0.170% or less. And it is preferably 0.155% or less.

Si: 0.25~0.60% In addition to being required for deoxidation in steelmaking, Si can also effectively inhibit the formation of oxide film after quenching and heat treatment, so it should be contained at more than 0.25%. If it is less than 0.25%, excessive oxide film will be formed and the final polishing load will increase. However, adding too much will suppress the formation of austenitic iron and impair the hardenability, so it is set to 0.60% or less.

Mn: 0.10~0.60% Mn is a stabilizing element of austenitic iron, which is necessary to ensure the hardness and the amount of scattered iron during quenching. Therefore, it should contain more than 0.10%. However, since it will promote the formation of oxide film during quenching and increase the subsequent grinding load, it is set to 0.60% or less. In addition, if it is added too much, a large amount of MnS is generated and corrosion resistance is also reduced.

P: Below 0.035% P is an element contained as an impurity in melt milling of raw materials or alloys such as ferrochrome. Since it is an element harmful to the toughness of the steel sheet after hot rolling and annealing or after quenching, its content is set to 0.035% or less. If it is added too much, hot workability and corrosion resistance will decrease.

S: 0.015% or less S has a small solid solubility in the austenitic iron phase, and segregates in the grain boundary to promote the reduction of hot workability. In addition, if it is contained too much, a large amount of MnS is generated and corrosion resistance is also reduced. Therefore, the S content is set to 0.015% or less.

Cr: 11.0~15.0% In order to maintain the corrosion resistance as a Western-style knife, Cr must be at least 11.0%. On the other hand, it also has the effect of narrowing the stable temperature range of austenitic iron, so it is set to 15.0% or less. And it should be more than 12.0%. In addition, the upper limit is preferably 14.0% or less. The range is preferably set to 12.0~14.0%.

Ni: 0.05~0.60% Ni series is the same as Mn as a stabilizing element for austenitic iron, which is necessary to ensure the hardness and the amount of scattered iron during quenching. Moreover, it also has the effect of improving corrosion resistance. Therefore, it should contain more than 0.05%. However, adding too much may sometimes increase the stability of the γ phase and reduce the amount of scattered iron in Asada. In addition, Ni is more expensive than other elements, so the upper limit is set to 0.60%.

Cu: 0.006~0.50% The Cu series is the same as Mn and Ni as an austenitic iron stabilizing element, and is an element that improves the corrosion resistance. Although it is also an element that cannot be avoided from the scrap during steel making, it must be contained at least 0.006% in order to improve the corrosion resistance. And it is better to contain 0.02% or more. It is better to contain 0.05% or more. On the other hand, excessive content will reduce hot workability, etc., so it is made 0.50% or less. Although it is cheaper than Ni, it is still more expensive. Therefore, it is desirable to reduce the added elements as much as possible.

V: 0.010~0.10% The V series is often unavoidably mixed from alloying elements such as ferrochrome. It is very difficult to reduce this point and will cause excessive load on the steel making step, so the content is more than 0.010%. However, excessive content reduces the austenitic iron formation temperature zone, so it is set to 0.10% or less. In addition, if it is added too much, VN will be formed and N will be fixed, which will cause a decrease in hardness or corrosion resistance, which is not preferable.

Al: less than 0.05% Al is an element that effectively deoxidizes. However, if it is contained excessively, CaS will be generated as a fusible inclusion during hot rolling, which will reduce the corrosion resistance, so the content should be 0.05% or less. The Al content should be more than 0.001%. It may not contain Al.

N: 0.040% or more and less than 0.060% Both N and C are elements that determine the quenching hardness, and at the same time are important elements in the present invention for improving the corrosion resistance. Therefore, it is necessary to contain 0.040% or more in the present invention. And more than 0.045% is better. However, if it contains too much N, it is easy to produce bubble defects in the flat embryo, which will reduce the corrosion resistance. At the same time, it is an element that increases the manufacturing cost in the secondary refining by VOD and the like. Especially in continuous casting, it is difficult to avoid bubble defects and stable production. Therefore, N is preferably lower, and its content is set to less than 0.060%. And it should be less than 0.057%.

C+1/2N: 0.130~0.190% The elements that determine the hardness of the Asada scattered iron phase in steel are C and N, and their total contributes to the hardness. According to the research of the inventor of this case, the contribution of N to the hardness is half of that of C. In order to obtain the required hardness as a Western-style knife, C+1/2N must be 0.130% or more. And more than 0.150% is preferred. On the other hand, if C+1/2N becomes too large, the quenching hardness will increase excessively, which will impair the toughness of the product or the intermediate material (cast slab, etc.) in the manufacturing process, so it is set to 0.190% or less. And it is preferably 0.180% or less, and it can also be set to 0.175% or less.

Furthermore, in order to stably exhibit hardness during quenching, mutual adjustments must be made so that γp described in the above formula (1) becomes 120 or more. If γp is less than 120, the hardness variation will increase depending on the quenching conditions. And δFe in steel also increases. In the present invention, γp can be adjusted to 130 or more, or 140 or more. And in the present invention, it may be 170 or less, or may be 150 or less.

In addition to the above-mentioned components, the steel composition of the present invention is composed of Fe and impurities.

In addition, in the present invention, in addition to the elements described above, the steel composition can also replace a part of the aforementioned Fe by adding Mo, Nb, Ti, and Sn and Bi elements to improve rust resistance and corrosion resistance.

Mo: 0.01~1.0% Mo is an element that improves the corrosion resistance and exhibits its effect when added at 0.01% or more. However, Mo is also an expensive element, and even if it is added excessively, its effect is not clear, so the upper limit is made 1.0%.

Ti: 0.005~0.050% Ti is an element that suppresses sensitization and corrosion resistance reduction caused by precipitation of chromium carbonitrides in stainless steel by forming carbonitrides. The effect will be displayed at 0.005%. However, excessive addition will make the Asada scattered iron phase unstable and reduce the hardness, so the upper limit is set to 0.050%.

Nb: 0.005~0.050% Nb is an element that suppresses sensitization and corrosion resistance reduction caused by precipitation of chromium carbonitrides in stainless steel by forming carbonitrides. The effect will be displayed at 0.005%. However, excessive addition will make the Asada scattered iron phase unstable and reduce the hardness, so the upper limit is set to 0.050%.

Sn: 0.01~0.10% Sn is an effective element in improving the corrosion resistance after quenching, and it should be more than 0.01%, and more than 0.05% should be added as required. However, since excessive addition will promote edge cracking during hot rolling, it is preferably set to 0.10% or less.

Bi: 0.01%~0.20% Bi is an element that improves corrosion resistance. Although the mechanism is not clear, it is speculated that the addition of Bi has the effect of making MnS, which is likely to be the starting point of rust, to become finer, and therefore the probability of becoming the starting point of rust is reduced. The effect can be exerted by adding more than 0.01%. Furthermore, even if it is added more than 0.20%, the effect will only be saturated, so the upper limit is set to 0.20%.

＜Comparative rate of δ ferrite iron of steel plate and steel components＞

The inventors of the present case discovered that the delta ferrous iron (delta Fe) present in the center of the thickness of the steel plate greatly affects the corrosion resistance of the end face of the steel plate. It is inferred that after the steel plate is quenched at a slow cooling rate with air cooling, the grain boundary between δFe and the parent phase (γ phase) will become the precipitation site of Cr carbide during cooling, causing sensitization near the precipitated Cr carbide, and Decrease the corrosion resistance of the end face. In addition, it can be inferred that the reason why N improves the corrosion resistance of the end surface is that it also has the effect of suppressing the precipitation of Cr carbides.

Therefore, in the present invention, N is included together, and δFe existing in the central part of the plate thickness in the steel can be effectively suppressed.

The steel plate of the present invention is a steel plate before quenching. Although it is sufficient to measure the δFe present in the steel sheet before quenching, it is difficult to measure the surrounding areas because of the ferrous iron phase. However, the δFe present in the steel plate after quenching and tempering is easy to measure because the surrounding area is the Asada scattered iron phase. Therefore, for the steel plate of the present invention (before quenching), the amount of δFe is evaluated after quenching and tempering. The quenching conditions used for evaluation were set at 1050°C and maintained for 30 minutes and then air-cooled, and the tempering conditions were set at 150°C and 30 minutes. If the quenching temperature is too low and the time is too short, the ferrous iron phase will remain and cannot be distinguished from the δFe phase, so it is not good. If the quenching temperature is too high and the time is too long, the δFe phase will change and be different from the initial state. good. The quenching method is set to air cooling. After quenching and tempering the steel plate under the above-mentioned evaluation conditions, the evaluation is carried out based on the area ratio of the δFe layer (the amount of δFe) in the thickness section of the steel plate.

As mentioned above, the steel plate and steel member of the present invention do not set the N content to a very high level. Therefore, compared with the case where the N content is higher, δFe must be further reduced. If it is the amount of N in the present invention, setting the amount of δFe to less than 0.1% can obtain good end surface corrosion resistance. Although the corrosion resistance is improved as the amount of δFe is reduced, a longer heat treatment is required as described later, so it is set to 0.05% or more. The range is preferably 0.05% or more and less than 0.1%. ＜Manufacturing method of steel plate＞

The manufacturing method of the steel plate of the present invention uses a conventional method. Through melting and casting, the flat embryo with adjusted composition is obtained, hot-rolled, and then box-annealed, sprayed and pickled to make a product.

However, in order to control the amount of δFe to less than 0.1%, preheating of the flat embryo is carried out. As a result, the amount of δFe produced can be reduced more than before, and good end surface corrosion resistance can be obtained. At this time, the heating conditions should be set to 1100~1150℃, and the soaking time should be set to be greater than 50 hours and less than 100 hours. If the heating temperature is higher than 1150℃, the two-phase (γ+δ) is stable and the amount of δFe increases sharply, so it is not good. In addition, the rapid increase of δFe will also remain in a large amount in the subsequent steps, so it will also become the main reason for the decrease in hardness. On the other hand, if it is lower than 1100°C, δFe will not decrease even if it is heated for a long time, which is undesirable. Since the amount of δFe is higher than 1150℃, the hardness can be maintained sometimes depending on the subsequent steps. In addition, δFe will become too much if it is less than 50 hours, and it is undesirable, and if it exceeds 100 hours, it will become expensive and undesirable.

The preheating can be carried out as heating of the flat blank before hot rolling, or directly hot rolling. ＜Manufacturing method of steel components＞

In the present invention, the obtained steel sheet is punched, quenched, and tempered, and polished to form a steel member. After punching, forging is sometimes performed to arrange the shape before quenching. In addition, the conditions for quenching and tempering are preferably as follows. The quenching temperature should be 1000~1150℃. If the quenching temperature is lower than 1000℃, the austenitic iron phase will be less at high temperature, and the hardness after quenching will decrease, so it is not good. On the other hand, if the quenching temperature is higher than 1150°C, the δ phase and the stable austenitic iron phase increase, and the hardness will also decrease at this time, which is not good. In addition, the maintenance time during quenching is preferably 1 minute to 1 hour. If the maintenance time is less than 1 minute, the austenitic iron phase will be less at high temperature, and the hardness after quenching will decrease, so it is not good. On the other hand, if the holding time is longer than 1 hour, the stable austenitic iron phase will increase, and the hardness will also decrease at this time, which is not good. The cooling rate during quenching is based on the average cooling rate from the quenching temperature to 600°C, which should be 1°C/sec or more. If it is less than this speed, the hardness will decrease, so it is not good. By setting the quenching to air cooling, the aforementioned better cooling rate can be achieved. In addition, the tempering temperature is preferably 100°C to 250°C. If the tempering temperature is lower than 100°C, the effect of tempering is poor, and if the tempering temperature is higher than 250°C, the decrease in hardness becomes too large, which is not preferable. ＜Steel structure of steel plate and steel components＞

As described above, the steel sheet of the present invention is box-annealed after hot rolling, and sprayed and pickled to produce a product. And for the obtained steel plate, the steel plate is further punched, quenched and tempered, and then ground to make the steel component of the invention. That is, the steel sheet of the present invention is in the state before quenching, and the steel structure of the steel sheet has a crystalline structure mainly composed of ferrous iron or the like. On the other hand, in the steel member of the present invention obtained by quenching and tempering the steel plate after processing, the steel structure of the steel structure becomes a structure mainly composed of Asada loose iron. Regarding the steel with the above properties, even if it is a steel plate before quenching and heat treatment (the steel structure is mainly made of ferrous iron), it is generally still called "Mada scattered iron-based stainless steel plate." For this reason, regarding the present invention, the steel sheet is also described as "Mada Scattered Iron-based stainless steel sheet".

Example The following examples illustrate the effects of the present invention, but the present invention is not limited to the conditions used in the following examples.

In this embodiment, the steel with the composition shown in Table 1 and Table 2 is first smelted and cast into a flat blank with a thickness of 250 mm. Next, as pre-heating, the flat embryos were heat-treated at 1150°C for 60 hours so that the amount of δFe was within a fixed range. However, for the A2 steel series, preheating is performed at 1175°C for 60 hours and 950°C for 60 hours to make A2' steel and A2" steel respectively.

[表2]

＜實施例1＞Then, it is heated to 1150°C and undergoes hot-rolling to produce a hot-rolled steel sheet with a thickness of 3-8mm. Then, the hot-rolled steel sheet is annealed by box annealing. Set the maximum heating temperature to a temperature zone above 800°C and below 900°C. And through bead spraying to remove the rust on the surface of the annealed steel plate, and pickling. [Table 1]

[Table 2]

<Example 1>

In order to evaluate the obtained steel plate, a sample for evaluation was cut out from the steel plate, and the sample was heated to 1050°C and maintained for 30 minutes as a quenching and tempering treatment, then air-cooled, and then subjected to a cycle of 150°C for 30 minutes Fire, made of steel components. Then carry out various evaluations of δFe amount measurement, hardness measurement and end surface corrosion resistance. The results obtained are shown in Table 3. [table 3]

The amount of δFe is measured by mirror-polishing and etching the end surface of the sample to expose the structure. Etching solution such as aqua regia can also expose δFe, but if the reagent described in Document 4 (Journal of the Japanese Society of Metals, 1962, Vol. 26, No. 7, pages 472-478) is used, it is called an improved Murakami reagent. δFe will be etched into dark brown, so it is ideal, and it is used for evaluation. A representative example is shown in Figure 1.

The tissue exposed by the modified Murakami reagent was examined with a microscope, a photograph of δFe was taken from a total thickness of a fixed width (2mm in this embodiment), and the δFe area was calculated from the image analysis, and then the area ratio (δFe area ( mm ² )/2mm×total thickness (mm)×100(%)) as the amount of δFe. In order for the steel member of the composition of the present invention to exhibit excellent corrosion resistance, the value must be less than 0.1%. And it should be above 0.05% and less than 0.1%. δFe area ratio (amount of δFe): less than 0.1% is considered acceptable (A), and more than that is considered unacceptable (X).

The hardness is after the surface of the sample is finished and ground to #80, the surface hardness (quenching hardness) is evaluated according to JIS Z 2245 with Rockwell hardness C scale, and 50 or more is regarded as a pass (A), otherwise it is regarded as not Pass (X).

The end surface corrosion resistance is evaluated by finishing and grinding the sample surface and end surface to #600. As the evaluation surface system, the end surface is the upper side, and the salt spray test is performed for 24 hours (JIS Z 2371 "Salt spray test method"), and the raw material is calculated. The number of rust spots. 2 points or less is considered pass (A), and if the number exceeds this number, it is considered unqualified (X). In particular, those with zero rust points are regarded as pass (S). In addition, even if the salt spray test is conducted for more than 24 hours, rust rarely advances further, so the 24-hour result is used to judge the end surface corrosion resistance.

The sample (equivalent to the steel member of the present invention) subjected to the specified quenching and tempering of the steel plate of the present invention not only has excellent end surface corrosion resistance, but also has excellent other properties, and is suitable as a steel plate for Western-style cutting tools. In contrast, comparative steels have poor end surface corrosion resistance or poor other characteristics, which are obviously not suitable for steel plates for Western-style kitchen knives. <Example 2>

Using the members cut out from the obtained steel plates, they were quenched and tempered under the conditions shown in Table 4 to produce steel members. The quenching system is heated at 1050~1150°C, and then the cooling rate from the quenching temperature to 600°C is controlled to the cooling rate described in Table 4 for cooling. And implement tempering treatment at 150~250℃ for 1~2 hours to make steel components. In addition, A2' steel and A2" steel are also treated in the same way.

The measurement of the amount of δFe, the measurement of hardness, and the evaluation of end surface corrosion resistance of the obtained steel member are shown in Table 4 together with the heat treatment conditions. In addition, the evaluation method and evaluation criteria were the same as in Example 1. [Table 4]

The steel member of the present invention not only has excellent end surface corrosion resistance, but also has excellent other characteristics, and is suitable as a steel member for western-style kitchen knives. In contrast, comparative steel has poor end surface corrosion resistance or poor other characteristics, which is obviously not suitable for steel components for Western-style kitchen knives.

According to the present invention, it is possible to manufacture the Asada scattered iron-based stainless steel components with excellent corrosion resistance on the end surface after air-cooling and quenching and the Asada scattered iron-based stainless steel plate used as the material in a highly productive manner. Sexuality will increase, which is very useful in the industry.

Fig. 1 shows a representative example of the cross-sectional structure of the steel sheet of the present invention after etching with modified Murakami reagent.

Claims (4)

A kind of Matian scattered iron series stainless steel plate, characterized in that it has the following steel composition: Calculated by mass%, C: 0.100~0.170%, Si: 0.25~0.60%, Mn: 0.10~0.60%, P: Below 0.035%, S: 0.015% or less, Cr: 11.0~15.0%, Ni: 0.05~0.60%, Cu: 0.006~0.50%, V: 0.010~0.10%, Al: 0.05% or less, N: 0.040% or more and less than 0.060%, and C+1/2N: 0.130~0.190%, and The remainder is composed of Fe and impurities, and Γp shown in the following formula (1) is 120 or more; After maintaining the aforementioned Asada bulk iron stainless steel plate at 1050°C for 30 minutes and then performing air quenching and tempering at 150°C for 30 minutes, the δ Fe grain iron (δFe) present in the center of the plate thickness is The area ratio in the section is less than 0.1%; γp=420C+470N+30Ni+7Mn+9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-52Al+189　・・・　Equation (1) The element symbol in formula (1) means the content (mass%) of the element. For example, the Matian scattered iron stainless steel plate of claim 1, wherein the aforementioned steel composition replaces a part of the aforementioned Fe and further contains one or more of the following elements: Calculated by mass%, Mo: 0.01~1.0%, Ti: 0.005~0.050% and Nb: 0.005~0.050%. For example, the Matian scattered iron stainless steel plate of claim 1 or claim 2, wherein the aforementioned steel composition replaces part of the aforementioned Fe and further contains one or two of the following elements: Calculated by mass%, Sn: 0.01~0.10%, Bi: 0.01~0.20%. A kind of Matian loose iron series stainless steel components, with the steel composition of any one of Claim 1 to Claim 3; The characteristics of the aforementioned Matian bulk iron series stainless steel components are: Γp shown in the aforementioned formula (1) is 120 or more; and, The area ratio of δ Fe grained iron (δFe) existing in the center of the plate thickness in the plate thickness section is less than 0.1%.

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