KR100595383B1 - Ferritic stainless steel sheet excellent in press formability and secondary formability and its manufacturing method - Google Patents

Abstract

Ferritic stainless steel sheet is C: 0.02 mass% or less, Si: 0.8 mass% or less, Mn: 1.5 mass% or less, P: 0.050 mass% or less, S: 0.01 mass% or less, Cr: 8.0-35.0 mass%, N: 0.05 mass% or less, Ti: 0.05-0.40 mass%, Nb: 0.10-0.50 mass%, and have a composition which is (% Tix% N) <0.005. Precipitates having a particle size of 0.15 µm or more, except for TiN, are distributed in the steel matrix at a rate of 5000 to 50000 particles / mm 2. The steel sheet is hot rolled slab at the hot rolling end temperature of 800 ° C. or lower, and then annealed the hot rolled steel sheet at 450 to 1080 ° C., and the intermediate annealing is performed at a temperature within the range of (recrystallization completion temperature-100 ° C.) to (recrystallization completion temperature). The hot rolled steel sheet is cold rolled together to be a cold rolled steel sheet, followed by final annealing of the cold rolled steel sheet at l080 占 폚 or lower. Ferritic stainless steel sheet has high dimensional accuracy and excellent secondary workability after press working due to the controlled distribution of precipitates.

Ferritic, stainless steel plate, hot rolled, cold rolled, dimensional accuracy.

Description

Ferritic stainless steel sheet with excellent press formability and secondary workability and its manufacturing method {FERRITIC STAINLESS STEEL SHEET EXCELLENT IN PRESS FORMABILITY AND SECONDARY FORMABILITY AND ITS MANUFACTURING METHOD}

1 is a view for explaining the roundness of a steel sheet formed in a cylindrical shape by a multi-stage press.

The present invention relates to a ferritic stainless steel sheet and a method of manufacturing the same, which can be processed into a predetermined shape without a poor roundness and torsion after machining by press working and then secondary processing into a final profile by good hot extrusion. will be.

Ferritic stainless steels represented by SUS430 and SUS430LX have good corrosion resistance.

It is economically superior to austenitic stainless steel because it does not contain Ni, which is an expensive element, and thus has been used in a wide range of fields such as durable consumer goods. The conditions for press forming a ferritic stainless steel sheet to obtain a product shape are becoming more and more severe according to the development of its use. Pressed steel sheets are often secondary processed, for example for the extrusion of holes. In response to the development of the application, there is a demand for providing a new ferritic stainless steel sheet which is remarkably superior in workability compared to a conventional ferritic stainless steel sheet, and is molded into a product without defect even under severe conditions.

Numerous studies have been reported on the formability of ferritic stainless steel sheets. A representative improvement is the combined addition of Ti and Nb for the stabilization of C and N dissolved as carbonitrides. Further, JP 2000-192199 A teaches the distribution of Mg based inclusions effective in anti- leasing properties in ferritic stainless steel sheets containing both Ti and Nb. JP 8-26436 B teaches a combination of hot rolling conditions designed to improve the Rankford value (r), an index of formability, with the addition of Ti and Nb.

The shape freezing and secondary workability of the primary-machined steel sheet to be processed to the final form are also important factors in addition to the Lankford value (r) and anti-rising properties.

Compared with the austenitic stainless steel sheet, the workability of the ferritic stainless steel sheet is generally inferior. In particular, the plate thickness in the primary molding is significantly reduced, and the thickness reduction is anisotropic. As a result, when the ferritic stainless steel sheet is pressed into a cylindrical shape, the dimensional accuracy such as roundness deteriorates as the processing conditions become excessive. Plate thickness variation after primary molding causes severe degradation of secondary processability such as hole extrusion.

When ferritic stainless steel sheet maintains high dimensional accuracy (e.g. roundness, shrinkage and anti-torsion) as well as secondary workability in the press-formed state, inexpensive ferritic stainless steel sheet is subjected to excessive processing conditions It can be used as a part or a member instead of the expensive austenitic stainless steel sheet which was inevitably used in view of the above.

Summary of the Invention

An object of the present invention is to provide a ferritic stainless steel sheet having improved dimensional accuracy and secondary workability after press working by controlling the particle size of the precipitate dispersed in the steel matrix and the distribution of the precipitate.

The present invention proposes a new ferritic stainless steel sheet. C: 0.02 mass% or less, Si: 0.8 mass% or less, Mn: 1.5 mass% or less, P: 0.050 mass% or less, S: 0.01 mass% or less, Cr: 8.0-35.0 mass%, N: 0.05 mass% or less, Ti: 0.05 to 0.40% by mass, Nb: 0.10 to 0.50% by mass, optionally Ni: 0.5% by mass or less, Mo: 3.0% by mass or less, Cu: 2.0% by mass or less, V: 0.3% by mass or less, Zr: 0.3% by mass or less, A1: 0.3% by mass or less, B: 0.0100% by mass or less selected from the group consisting of, the remainder is Fe and unavoidable impurities, (% Ti x% N) <0.005 A new ferritic stainless steel sheet having a phosphorus composition is proposed. Its metallurgical structure is defined as having a distribution of 500 to 50000 particles / mm ² of precipitates having a particle size of 0.15 μm or more except for TiN.

Ferritic stainless steel sheets are manufactured as follows:

The molten steel of the desired composition is cast into slabs. The slab is hot rolled into a steel sheet at a temperature of 800 ° C. or lower after the hot rolling, and then annealed at 450 to 1080 ° C. The annealed hot rolled steel sheet is pickled and cold rolled with cold rolling with at least one intermediate annealing within a temperature range of (recrystallization complete temperature-10 DEG C) to (recrystallization complete temperature). Cold rolled steel sheet is finally annealed at a temperature of 1080 ℃ or less.

The hot rolled steel sheet may be box-annealed for a predetermined time of one hour or shorter. Intermediate annealing and finish annealing can be performed in a continuous annealing furnace for one minute or shorter time.

Detailed description of the invention

The present inventors studied and reviewed from various viewpoints about the manufacturing conditions of ferritic stainless steel sheet for improving the dimensional accuracy (roundness, shrinkage and torsion, etc.) after press working, and the shape and distribution of TiN and other precipitates after annealing were It was found that the steel sheet had a great influence on the roundness and the secondary workability. Based on the findings, the inventors assume that the target characteristics can be given to the ferritic stainless steel sheet by appropriately controlling the shape and distribution of the precipitates. As a carbonitride, ferritic stainless steels in which both Ti and Nb are added in combination with the stoichiometric ratio employed for stabilization of C and N are used, and shapes and distributions suitable for the purpose are optimized by optimizing the processing heat treatment of the ferritic stainless steel sheet. The formation of precipitates is realized.

The influence of morphology and distribution of precipitates on press formability and dimensional accuracy is estimated as follows:

C and N contained in the ferritic stainless steel are mostly precipitated as carbonitrides by addition of Ti and Nb. Precipitated carbonitrides other than TiN are substantially modified into very fine particles during the production of finish annealing from hot rolled steel sheet annealing through cold rolling. When the fine grains are annealed for recrystallization, the fine precipitate does not exhibit pinning action, and recrystallized grains having a specific crystal orientation are first grown, resulting in a large anisotropic mixed structure. The large anisotropy is a cause of concentration of deformation along a specific direction during the primary processing of the steel sheet, and deteriorates the press formability of the steel sheet and the dimensional accuracy after the press working.

By the distribution of precipitates having a particle size of a certain value or more, a pinning action at the time of recrystallization is expected. In order to improve the anisotropy and dimensional accuracy of the pressed steel sheet, the pinning action suppresses preferential growth or coarsening of grains having a particular crystal orientation. The effect of the pinning action on the press formability and the dimensional accuracy after press working is typically remarkable by depositing precipitates with a particle size of 0.15 μm or more excluding TiN at a rate of 500-50000 / mm ² , as can be seen in the examples below. Become.

Among the precipitates, TiN is not preferable in terms of press formability and dimensional accuracy after press work. In fact, steel sheets with (% Ti ×% N) exceeding 0.005 crack in the press-formed state. Coarse TiN particles deposited in a cubic shape are observed at the starting point of cracking. These observations mean that the strain concentrates on the cubic vertices during press working and causes micro cracks. The concentration of deformation and the occurrence of microcracks around TiN are also poor for hole extrusion in the secondary forming step.

The ferritic stainless steel sheet of the present invention contains an alloy component at a predetermined ratio as follows.

[C: 0.02 mass% or less]

Although C turns into carbides and is effective for random growth of recrystallized ferrite during finish annealing, the excessive amount of C reduces workability because it is a component that increases strength. Carbide precipitation also causes deterioration in corrosion resistance. From this point of view, it is desirable to control the upper limit of the C content to 0.02% by mass as low as possible in consideration of moldability and corrosion resistance. It is preferable to reduce C content to 0.015 mass% or less for the improvement of secondary workability. However, lowering the C content to a lower level than necessary requires a long time of refining and causes the steel material cost to increase. Therefore, the lower limit of the C content is preferably determined at 0.001 mass%. The definition of the lower limit also ensures the influence of carbides that contributed to the random growth of recrystallized ferrite during finish annealing.

[Si: 0.8% by mass or less]

It is an alloy component added as a deoxidizer at the time of steelmaking, but its solid solution hardenability is high. Excessive Si content in excess of 0.18% by mass causes material hardening and ductility degradation. For ductility and secondary workability, it is preferable to set the upper limit of the Si content to 0.5 mass%.

[Mn: 1.5 mass% or less]

Mn has a less hardening effect than Si due to its small solid solution strengthening ability. However, when excess Mn in excess of 1.5 mass% is contained, Mn-type fume will generate | occur | produce in steelmaking, and manufacturability will deteriorate.

[P: 0.050% by mass or less]

P is a component harmful to hot workability, and the upper limit of the P content is set at 0.050% by mass from the viewpoint of workability.

[S: 0.01% by mass or less]

S is a harmful component which segregates in the grain boundary and embrittles the grain boundary. Such a defect can be suppressed by regulating S content to 0.01 mass% or less.

[Cr: 8.0-35.0 mass%]

In order to obtain the corrosion resistance required for stainless steel, the Cr content is controlled to at least 8.0 mass%. However, since the toughness and secondary workability of stainless steel deteriorate with the increase of Cr content, the upper limit of Cr content is set to 35.0 mass%. Cr content is preferably controlled below 20.0 mass% for further improvement in ductility and secondary workability.

[N: 0.05% by mass or less]

N becomes nitride and is effective for randomized growth of recrystallized ferrite grains in finish annealing, but has a curing effect. Since excessive amount of N reduces the ductility of a steel plate, it is preferable to reduce N content as much as possible, and in this invention, the upper limit of N content is set to 0.05 mass% from a viewpoint of ensuring ductility. In order to further improve ductility and secondary workability, an N content of 0.02 mass% or less is preferable. However, the reduction of the N content more than necessary requires a long time of refining, and causes the steel cost to increase. Therefore, the minimum of N content becomes like this. Preferably it is determined to 0.001 mass% or more. The lower limit also ensures the effect of nitride on random growth of recrystallized ferrite grains in the finish annealing step.

[Ti: 0.05 to 0.40 mass%]

Ti is an alloy component that stabilizes C and N as carbonitrides for improving workability and corrosion resistance. Such effect is remarkable at Ti contents of 0.05% by mass or more. However, addition of excess Ti in excess of 0.40 mass% is not preferable to raise steel cost and generate surface defects resulting from Ti type inclusions.

[Nb: 0.10 to 0.50 mass%]

Nb, like Ti, is an alloy component having an effect on stabilization of C and N, and is an essential component for precipitates of Nb-based inclusions having a particle size of 0.15 μm or more except TiN. The Nb-based inclusions preferably consist of carbide and Fe ₂ Nb. An Nb content of 0.10 mass% or more is necessary for the precipitation of such niobium-based inclusions. However, addition of 0.5b or more of Nb is not preferable because it causes more precipitation than necessary and raises the recrystallization temperature of ferritic stainless steel.

[Ni: 0.5 mass% or less]

Ni is an alloy component added as needed, and is effective for improving toughness and corrosion resistance of a hot rolled steel sheet. However, excessive addition of Ni causes an increase in the raw material cost and hardening, so the upper limit of the Ni content is set at 0.5% by mass.

[Mo: 3.0 mass% or less]

Mo is an alloy component added as needed and contributes to the improvement of corrosion resistance. However, excessive addition of Mo exceeding 3.0 mass% is not preferable because it reduces hot workability.

[Cu: 2.O mass% or less]

Cu is an alloy component added as needed, and it mixes in stainless steel from scrap etc. at the time of steelmaking. If excess Cu is contained, it will cause embrittlement and hot workability fall, and the upper limit of Cu content is set to 2.0 mass% or less.

[V: 0.3 mass% or less, Zr: 0.3 mass% or less]

V and Zr are alloy components added as needed. V precipitates solid solution C as a carbide in the steel matrix to improve workability, while Zr captures oxygen in the steel to improve workability and toughness. However, if it adds excessively, productivity will fall. In this sense, the upper limit of the content of each of V and Zr is set to 0.3 mass%.

[Al: 0.3 mass% or less]

Al is an alloy component added as needed and is added as a deoxidizer at steelmaking time.

However, excessive addition of A1 in excess of 0.3% by mass leads to an increase in nonmetallic inclusions, leading to a decrease in toughness and surface defects.

[B: 0.0100 mass% or less]

B is an alloy component added as needed, stabilizes N, and has the effect | action which improves the corrosion resistance and workability of stainless steel. The effect of B is evident above 0.0010% by mass, but excess B above 0.0100% by mass deteriorates hot workability and weldability.

In addition to the components listed above, Ca, Mg, Co, REM (rare earth metal) and the like may be incorporated from steel scrap as a raw material in steelmaking. Except in the case where such components are contained in large quantities, they do not adversely affect the roundness in deep drawing processing or the dimensional accuracy after press working.

[(% Ti ×% N) <0.005]

TiN grows into coarse particles or forms clusters with an increase of (% Ti x% N). Coarse TiN particles or clusters promote the accumulation of deformation during primary processing, resulting in the formation of microcracks at an early stage of drawing processing. As will be appreciated in the examples below, this deleterious effect of coarse TiN particles or clusters is eliminated by regulating (% Ti x% N) to a value of less than 0.005.

[Distribution rate of precipitates with particle size of 0.15㎛ or more excluding TiN: 5000-50000 / mm ² ]

Carbide and nitride precipitates having a particle size of 0.15 µm or more have a pinning action, thereby suppressing preferential growth of grains having grain orientation or coarsening of grains, thereby improving anisotropy of stainless steel sheets, roundness after cylindrical drawing, and dimensional accuracy after press working.

Precipitates are carbides and nitrides of Ti and Nb, Laves phase and mixtures thereof. TiN particles precipitated in the form of a cube are excluded from precipitates effective in press formability and dimensional accuracy because deformation concentrates at the peaks of precipitate particles during processing and easily acts as a starting point of minute cracks. 5000 ~ 50000 pcs / mm ² The distribution of precipitates with a particle size of 0.15 μm or more, excluding the ratio TiN, ensures an effective pinning action on the press formability and dimensional accuracy of the pressed steel piece as noted in the examples below.

The effect of precipitates on the formability and dimensional accuracy of press-formed steel pieces is noted at a particle size of 0.15 mu m or more, and becomes larger depending on the size of the particle size. However, coarse precipitates having a particle size of 1.0 mu m or more promote accumulation of deformation and formation of minute cracks during press working, resulting in poor form freezing. The pinning action of the precipitates is clearly noted at a distribution ratio of 5000 / mm ² , but the excessive distribution of precipitates of 50000 / mm ² or more deteriorates the ductility and deep drawability of the steel sheet. The excessive distribution raises the recrystallization temperature of the steel sheet, and therefore, the steel sheet is not preferable in that it is difficult to anneal to the recrystallized state.

From the following description the manufacturing conditions necessary for controlling the form and distribution of the precipitate will be understood from the following description.

[Hot rolling at hot end temperature below 800 ℃]

Ferritic stainless steel sheets are hot rolled at a relatively low hot finish temperature to cause nuclei to deposits distributed in the finish annealed steel sheet. Ferrite grain boundaries and internal deformation after hot rolling serve as nucleus sites. Hot rolled end temperature is set below 800 ° C to cause as many nuclear sites as possible.

[Annealing of Hot Rolled Steel Sheets at 450 ~ 1080 ℃]

The precipitate of the hot rolled steel sheet is annealed at 450 to 1080 ° C to anneal the hot rolled steel sheet in a form suitable for controlling the precipitate distributed in the finished annealed steel sheet to a particle size of 0.15 µm or more. If the annealing temperature is lower than 450 ° C., little effective precipitate is produced. If, on the contrary, the hot rolled steel sheet is heated at a temperature above 1080 ° C., the precipitates other than TiN are not suitable because they are reused in the steel matrix.

Annealing is completed within 1 hour to adequately control the number of distribution of precipitates without growing into coarse particles.

[Intermediate annealing at a temperature within the range of (recrystallization completion temperature-100 ° C) to (recrystallization completion temperature)]

During cold rolling, the steel sheet is annealed at a relatively low temperature in order to suppress re-use of the precipitate formed by annealing the hot rolled steel sheet. The intermediate annealing temperature just below the recrystallization completion temperature is desirable to remove the strain introduced into the steel sheet by cold rolling. The steel sheet can be softened without reclaiming the precipitate, regardless of whether there is some rolling structure that has not yet been recrystallized as long as the annealing temperature is maintained within the range of (recrystallization temperature-100 ° C) to (recrystallization temperature).

The intermediate annealing period is completed in one minute to avoid re-use of the precipitates encountered in conventional continuous annealing furnaces.

[Finish Annealing at Temperature Below 1080 ° C]

The rolled structure is removed by finish annealing. However, the heating temperature above 1080 ° C. is not only disadvantageous for mass production, but also precipitates are re-used and coarsened grains, leading to a decrease in toughness.

Finish annealing is completed in one minute to avoid re-use of the precipitates encountered in conventional continuous annealing furnaces.

Other features of the present invention will be apparent from the following examples, but the scope of the present invention is not limited to these examples.

Example 1 (Basic Experiment)

The present inventors investigated the effects of TiN, which are often precipitated in ferritic stainless steel matrices, and the morphology of the precipitates on dimensional accuracy and secondary workability after press working under the following conditions.

Several steels were melted and cast into slabs in the test furnace, where each steel

C: 0.007% by mass, Si: 0.40% by mass, Mn: 0.25% by mass, P: 0.030% by mass, S: 0.0005% by mass, Cu: 0.05% by mass, Cr: 16.50% by mass, Al: 0.04% by mass, Fe and inevitable impurities, except that the Nb, Ti, and N contents were varied within the range of 0.02 to 0.30 mass%, 0.05 to 0.30 mass%, and 0.005-0.035 mass%, respectively.

Table 1 shows Nb, Ti and N content, (% Ti x% N) and recrystallization completion temperature.

Each slab was hot rolled to a thickness of 4 mm at a hot end temperature of 750 ° C.

Hot rolled steel sheet Nos. 1-7 was annealed at 800 degreeC for 60 second, it was cold-rolled after pickling, and it was set as the thickness of 2 mm. The steel sheet was made into a final thickness of 0.5 mm by cold rolling with intermediate annealing for 60 seconds at a temperature of (recrystallization completion temperature-50 ° C). The cold rolled steel sheet was finish annealed at 1000 ° C. for 60 seconds.

Cold rolled steel plate Nos. 8 and 9 were annealed, cold rolled after pickling to a thickness of 2 mm. The steel sheets were intermediately annealed and cold rolled to a final thickness of 0.5 mm. The cold rolled steel sheet was finish annealed. Table 2 shows the conditions of annealing, intermediate annealing and finish annealing of the hot rolled steel sheet.

[Distribution rate and form of precipitate]

The specimens sampled from each of the annealed steel sheets were etched in a nonaqueous electrolyte of 10% acetylacetone-1% tetramethyl ammonium chloride-methyl alcohol under the potential potential and then observed by scanning electron microscope to investigate the distribution of precipitates. . The cross sections parallel to the rolling direction were inspected at 50 arbitrary points, and the maximum length of each precipitate was measured and evaluated by particle size.

[Dimension Accuracy of Pressed Steel Sheet]

Blanks sampled from each annealed steel sheet were press molded by a multistage press to a cylindrical profile (shown in FIG. 1). The maximum and minimum radius of the cylindrical part C at the position 5 mm from the flange part F was measured by the laser displacement meter. The ratio of (maximum diameter-minimum diameter) / (minimum diameter) was calculated and the dimensional accuracy of the pressed steel sheet was evaluated by considering the roundness.

Secondary Machinability

Another test piece was made to have a height of 10 mm by using a punch having a diameter of 103 mm, a shoulder radius of 10 mm, and a die having a diameter of 105 mm and a shoulder radius of 8 mm, while the flange of the test piece was fixed to the bead. A blank of 92 mm in diameter was sampled from the bottom of the elongated test piece, and a hole of 10 mm in diameter was formed at the center of the blank with a clearance of 10%. The blanks were then subjected to secondary workability testing as follows.

The blank was held in such a way that a burr around the hole faces the die between a flat head punch with a diameter of 40 mm and a shoulder radius of 3 mm and a die with a diameter of 42 mm and a shoulder radius of 3 mm. The hole was extruded by a punch until a crack occurred at the edge, while the flange of the blank was fixed with the bead. The diameter of the hole was measured at the start of the crack. Second-extrusion ratio was calculated according to the following equation. Secondary-extrusion ratio (%) = (diameter of extruded hole-diameter of unextruded hole) / (diameter of unextruded hole) × 100.

Table 3 shows the results. It is noted that the steel sheet cracked during press-forming when the product of (% Ti x% N) was greater than 0.005. The steel sheet having an Nb content of less than 0.02% by mass exhibited a decrease in roundness regardless of the manufacturing conditions. The observations for all cracked steel sheets and steel sheets showing roundness reduction showed very rarely distributed precipitates with a particle size of 0.15μm except TiN in the steel matrix.

On the other hand, the roundness was improved as an increase in the number of precipitates distributed in the steel matrix having an Nb content of 0.3% by mass or more in combination with the thermomechanical treatment conditions. But,

The steel sheet whose product of (% Ti x% N) was greater than 0.005 was inferior to the secondary workability. Poor secondary formability was also noted for steel sheets of 0.02 mass% Nb.

The improvement of secondary workability (ie pore enlargement) was confirmed as an increase in the number of precipitates distributed in the steel matrix having an Nb content of 0.3 mass% or more. However, the excessive distribution of precipitates was not suitable for secondary workability.

The results demonstrate that the dimensional accuracy and secondary machinability of the pressed steel sheets depend on the distribution of precipitations of 0.15 μm or more excluding TiN. In other words, for a controlled distribution of these precipitates at a ratio of 5000 to 50000 / mm ² , an optimum thermomechanical treatment is effective for dimensional accuracy and secondary workability.

Example 2

Several stainless steels having the compositions shown in Table 4 were melted in a vacuum furnace and cast into slabs. Steels A to H belong to the present invention, and steels I to L do not satisfy the composition definition of the present invention.

Each slab was hot rolled to a thickness of 4.0 mm, annealed, pickled and cold rolled to a thickness of 2 mm. The cold rolled steel sheet was intermediately annealed and further cold rolled to a final thickness of 0.5 mm and then finished annealed. Table 5 shows the conditions for hot end temperature, annealing of hot rolled steel sheets, intermediate annealing and finish annealing.

Each steel sheet was irradiated in the same manner as in Example 1 to investigate the form and distribution of precipitates, and the dimensional accuracy and secondary workability of the pressed steel sheet.

The results shown in Table 6 show that the precipitates with a particle size of 0.15 μm or more except for TiN were pressed to a good profile having a roundness of 2.5% or less for ferritic stainless steel sheets distributed in the steel matrix at a ratio of 5000 to 50000 / mm ² .

On the other hand, the comparative steel sheet (Examples Nos. A2, B2, C2, and D2) manufactured under inadequate conditions, although satisfying the compositional conditions of the present invention, has a distribution number of precipitates of not less than 0.15 μm and having a particle size of 5000-50000. The metallographic structure, which was outside the range of ² mm / mm ² , resulted in inferior dimensional accuracy and secondary machinability after pressing.

Sheet I was too hard due to excess C and cracked during press working. Steel plate K was too strong due to excess Nb and cracked during press working. Steel plate L with a product of (% Ti x% N) greater than 0.005 cracked during press working, with the cracking starting near coarse TiN particles. The steel sheet J lacking Nb was inferior in roundness after the press working.

As a result of the above comparison, it is understood that the ferritic stainless steel sheet can be made into a target profile having dimensional accuracy after press working and excellent secondary workability by controlled distribution of precipitates having a particle size of 0.15 μm or more except TiN.

As described above, according to the present invention, the ferritic stainless steel sheet, which can have high dimensional accuracy and excellent secondary workability after press working, has a particle size of 0.15 except TiN at a ratio of 5000 to 50000 / mm ² in a steel matrix having a controlled composition. Provided by the distribution of precipitates of μm or more. The shape and distribution of these precipitates suitable for the purpose are realized by appropriately controlling the heat treatment conditions of the hot-rolled end temperature and the hot-rolled steel sheet annealing, the intermediate annealing in cold rolling, and the finish annealing of the cold rolled steel sheet. Ferritic stainless steel sheet produced in this way is an element or component that requires strict dimensional accuracy in various fields in place of expensive austenitic stainless steel sheet, for example, sealing members for organic electroluminescent devices, precision pressed parts, It is useful as a sink, an article, a burner of a stove, an oil filler tube of a fuel tank, a motor casing, a cover, a cap of a sensor, an injector tube, a thermostat valve, a bearing seal, a flange, and the like.

Claims (2)

C: 0.02 mass% or less, Si: 0.8 mass% or less, Mn: 1.5 mass% or less, P: 0.050 mass% or less, S: 0.01 mass% or less, Cr: 8.0-35.0 mass%, N: 0.05 mass% or less, Ti: 0.05 to 0.40% by mass, Nb: 0.10 to 0.50% by mass, optionally Ni: 0.5% by mass or less, Mo: 3.0% by mass or less, Cu: 2.0% by mass or less, V: 0.3% by mass or less, Zr: 0.3% by mass or less, A1: 0.3% by mass or less, B: 0.0100% by mass or less selected from the group consisting of, the remainder is Fe and unavoidable impurities, (% Ti x% N) <0.005 Has a phosphorus composition, A ferritic stainless steel sheet having excellent press formability and secondary workability having a metal structure in which precipitates having a particle size of 0.15 µm to 1.0 µm excluding TiN are distributed in a steel matrix at a rate of 5000 to 50000 / mm ² . C: 0.02 mass% or less, Si: 0.8 mass% or less, Mn: 1.5 mass% or less, P: 0.050 mass% or less, S: 0.01 mass% or less, Cr: 8.0-35.0 mass%, N: 0.05 mass% or less, Ti: 0.05 to 0.40% by mass, Nb: 0.10 to 0.50% by mass, optionally Ni: 0.5% by mass or less, Mo: 3.0% by mass or less, Cu: 2.0% by mass or less, V: 0.3% by mass or less, Zr: 0.3% by mass or less, A1: 0.3% by mass or less, B: 0.0100% by mass or less selected from the group consisting of, the remainder is Fe and unavoidable impurities, (% Ti x% N) <0.005 Providing a slab of ferritic stainless steel having a phosphorus composition; Hot rolling the slab at a hot end temperature of 800 ° C. or lower, Annealing the hot rolled steel sheet at a temperature in the range of 450-1080 ° C., Cold rolling the cold rolled steel sheet by cold rolling with at least one intermediate annealing at a temperature in the range of (recrystallization complete temperature-100 ° C) to (recrystallization completion temperature), and And subsequently annealing the cold rolled steel sheet at a temperature below 1080 ° C., Manufacturing method of ferritic stainless steel sheet excellent in press formability and secondary workability.

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