JP5745345B2 - Ferritic stainless steel sheet excellent in hot workability and weather resistance and manufacturing method thereof - Google Patents

Description

  The present invention relates to a ferritic stainless steel sheet, and more particularly to an alloy-saving ferritic stainless steel sheet excellent in hot workability and weather resistance and a method for producing the same.

  Ferritic stainless steel sheets are used in a wide range of fields for interior and exterior of home appliances, kitchen equipment, and building materials. This is because the ferritic stainless steel plate is a rare metal and is more economical than the austenitic stainless steel plate containing a large amount of Ni, which has recently experienced a significant increase in price.

  Low Cr ferritic stainless steels containing about 11 to 13% Cr are JIS steel types such as SUS405, SUS410L, SUH409, and SUH409L with reduced C content. These low Cr ferritic stainless steels are the cheapest of all stainless steels and have good workability. However, the amount of Cr is small, so there is a limit to corrosion resistance, such as home appliances / kitchen equipment and building / building materials. It does not have the necessary corrosion resistance as a general durable consumer material.

  Therefore, medium Cr ferritic stainless steel containing about 14 to 20% of Cr is widely used for applications as a general durable consumer material. Among them, SUS430 containing about 17% of Cr is particularly used.

  The medium Cr ferritic stainless steel used in the above applications is required to have excellent corrosion resistance against pitting and rusting in a neutral chloride environment. Usually, C and N are reduced to improve the corrosion resistance of SUS430. In addition to SUS430, there are high purity ferritic stainless steels in which C and N are reduced and a stabilizing element such as Nb and Ti is added.

  As a JIS steel grade, there is SUS430LX, and as a higher grade steel grade of SUS430LX, there are SUS430J1L, SUS436J1L, etc. in which Cu, Ni, Mo, etc. are added and the Cr amount is increased.

  In addition to Ni, Mo, Nb, and Ti, Cr, which is a main element of stainless steel, is a rare metal and has an economic problem associated with price fluctuations. Therefore, without depending on the use of these rare metals, it becomes a problem to improve the corrosion resistance of the low Cr ferritic stainless steel and SUS430 to expand the application.

  In order to solve the above problems from the viewpoint of resource saving and economical efficiency, studies have been made to improve the intergranular corrosion resistance of low Cr ferritic stainless steel by adding a small amount of Sn or Sb.

  In Patent Document 1, C: 0.001 to 0.30%, N: 0.001 to 0.050%, Cr: 10.0 to 30.0%, S: 0.010% or less, P: 0 0.040% or less, Mn: 0.01 to 1.0%, Si: 0.01 to 1.0%, Ni: 1.0% or less, O: 0.010% or less, Sn: 0.0. Ferritic stainless steels having excellent surface properties containing one or two of 005 to 0.10% and Sb: 0.005 to 0.10% are disclosed. The amount of Sn and Sb in this stainless steel is substantially less than 0.05%.

  In Patent Document 2, C: 0.03 to 0.25%, Si: 0.25 to 0.6%, Mn: 2% or less, P: 0.035% or less, S: 0.01% or less, Cr: 11 to 15.5%, Ni: 0.6% or less, Cu: 0.8% or less, Mo: 0.05% or less, Sn: 0.03 to 0.15%, V: 0.1% Hereinafter, martensitic stainless steel containing Al: 0.03% or less and N: 0.01-0.08% and having a high hardness of 300-600 Hv and excellent in corrosion resistance is disclosed.

  Patent Documents 3 to 5 have the effect of controlling non-metallic inclusions and improving corrosion resistance on the premise of adding a small amount of Mg. W, V, Zr, Co, Se, Ta, Re, Y, La, Hf A ferritic stainless steel having a small amount of rare metal or Sn added and excellent in corrosion resistance, surface characteristics, and workability is disclosed.

  The ferritic stainless steels described in Patent Documents 3 and 5 are high-purity ferritic stainless steels in which C and N are reduced and stabilizing elements such as Ti and Nb are added. The ferritic stainless steel described in Patent Document 4 is a high-Mg ferritic stainless steel with Mg: 12 to 60 ppm, C: 0.039 to 0.1%, and N: 0.0002 to 0.05%.

  So far, the present inventors have disclosed a high-purity ferritic stainless steel that has improved weather resistance and workability by the addition of Sn, not from the addition of Cr or Mo, from the viewpoint of resource saving and economy. Yes. Sn, together with Cu, is a typical trump element in steel materials, and thus a recycled iron source can be effectively used as the Sn source.

  Patent Documents 6 and 7 include Cr: 13 to 22%, Sn: 0.001 to 1%, reducing C, N, Si, Mn, and P, and stabilizing elements of Ti and Nb as necessary. A high-purity ferritic stainless steel to which is added is disclosed.

Japanese Patent Laid-Open No. 11-92872 JP 2010-215995 A JP 2001-11582 A JP 2001-288543 A JP 2001-294991 A JP 2009-174036 A JP 2010-159487 A

Metal Treatment, (1964), p.230, 245 Stainless steel as eco-material and recycling, Japan Iron and Steel Association, Material and Organization Properties Subcommittee, published on October 2, 2000, page 9

  So far, in low Cr ferritic stainless steel, it has been studied to improve the corrosion resistance by adding a small amount of Sn or Mg without relying on rare metals, but the object of study is that the added amount is less than 0.05% It was limited to ferritic stainless steel. Therefore, low Cr ferritic stainless steel has not yet been provided with corrosion resistance that can be applied to general durable consumer materials.

  The effect of addition of Sn is manifested in martensitic stainless steel with a Hv of 300 or higher, or high-purity ferritic stainless steel with reduced C and N, but sufficient corrosion resistance is not obtained for expansion of applications.

  Therefore, the present invention focuses on Sn that can be expected to be effectively used from recycled iron sources without relying on rare metals, and can improve the corrosion resistance of low Cr ferritic stainless steel and can be applied to general durable consumer materials. An object is to provide an alloy-saving ferritic stainless steel sheet.

  The inventors of the present invention have found that improvement of hot workability becomes a manufacturing problem when Sn is added to improve the corrosion resistance of the low Cr ferritic stainless steel. Non-Patent Document 2 discloses that Sn inhibits the hot workability of stainless steel, and in an austenitic stainless steel, it is disclosed that Sn <0.01% is kept low. There is no specific disclosure about steel and it has not been recognized as a problem so far.

  In order to solve the above-mentioned problems, the present inventors have intensively studied on the low Cr ferritic stainless steel, focusing on the weather resistance and the hot workability that is a manufacturing problem due to the addition of Sn. ) To (d) were obtained.

  (A) Sn is an element effective for improving the weather resistance of high purity ferritic stainless steel, but is limited to high purity ferritic stainless steel, in low Cr ferritic stainless steel and medium Cr ferritic stainless steel However, when a small amount of Sn is added, the weather resistance is improved, and when γp defined by the following formula is adjusted to 10 ≦ γp ≦ 65, good hot workability can be obtained. The technical meaning of the following formula will be described later.

γp = 420C + 470N + 23Ni + 7Mn + 9Cu-11.5Cr
-11.5Si-52Al-69Sn + 189
γp is an index that represents the maximum value of the amount of austenite generated during heating at 1100 ° C. disclosed in Non-Patent Document 1.

  (B) Hot workability can be improved by reducing C and N to reduce deformation resistance at high temperatures, or adding a small amount of Mg, B, Ca, etc. to increase grain boundary strength.

  (C) Moreover, the hot workability can be improved by increasing the slab heating temperature and the hot rolling end temperature to reduce the deformation resistance at a high temperature.

  (D) The weather resistance can be improved by adding a stabilizing element of Nb or Ti, or by mixing Ni, Cu, Mo, V, or the like from the recycled iron source.

  This invention was made | formed based on the knowledge of said (a)-(d), and the summary is as follows.

(1) By mass%, C: 0.001 to 0.3%, Si: 0.01 to 1.0%, Mn: 0.01 to 2.0%, P: 0.005 to 0.05% , S: 0.0001 to 0.01%, Cr: 11.0 to 13.0%, N: 0.001 to 0.1%, Al: 0.0001 to 1.0%, Sn: 0.05 In a ferritic stainless steel sheet composed of ~ 1.0%, the remainder Fe and inevitable impurities, γp defined by the following formula (2) satisfies the following formula (1) and hot workability and wrinkle resistance Ferritic stainless steel sheet with excellent properties.
10 ≦ γp ≦ 65 (1)
γp = 420C + 470N + 23Ni + 7Mn + 9Cu-11.5Cr
-11.5Si-52Al-69Sn + 189 (2)
Here, C, N, Ni, Mn, Cu, Cr, Si, Al, and Sn are the contents of each element.

(2) The ferritic stainless steel sheet excellent in hot workability and weather resistance according to (1), wherein the following expression (1 ′) is satisfied instead of the expression (1).
15 ≦ γp ≦ 55 (1 ′)

  (3) The ferritic stainless steel sheet is further, in mass%, Mg: 0.005% or less, B: 0.005% or less, Ca: 0.005% or less, La: 0.1% or less, Y: One or more of 0.1% or less, Hf: 0.1% or less, and REM: 0.1% or less are included. Hot working as described in (1) or (2) above Ferritic stainless steel sheet with excellent durability and weather resistance.

  (4) The ferritic stainless steel sheet is further in mass%, Nb: 0.3% or less, Ti: 0.3% or less, Ni: 1.0% or less, Cu: 1.0% or less, Mo: 1.0% or less, V: 1.0% or less, Zr: 0.5% or less, Co: 0.5% or less, containing one or more kinds (1) to ( 3) A ferritic stainless steel sheet excellent in hot workability and weather resistance according to any one of 3).

  (5) The stainless steel slab having the composition according to any one of (1) to (4) is heated to 1100 to 1300 ° C. and subjected to hot rolling, and the steel sheet after hot rolling is finished is 700 to 1000. A method for producing a ferritic stainless steel sheet excellent in hot workability and weather resistance, characterized by winding at ℃.

  (6) The hot workability as described in (5) above, wherein the steel sheet after the hot rolling is not annealed, or is subjected to continuous annealing or box annealing at 700 to 1000 ° C. A method for producing ferritic stainless steel sheets with excellent weather resistance.

  According to the present invention, the corrosion resistance of low Cr ferritic stainless steel can be improved by effectively using Sn in a recycled iron source without relying on rare metals, and can be applied to general durable consumer goods. An alloy type ferritic stainless steel sheet can be provided.

It is a figure which shows the relationship between (gamma) p and hot workability.

  The present invention will be described below.

  The ferritic stainless steel sheet (hereinafter sometimes referred to as “the present invention steel sheet”) excellent in hot workability and weather resistance of the present invention is in mass%, C: 0.001 to 0.3%, Si: 0.01-1.0%, Mn: 0.01-2.0%, P: 0.005-0.05%, S: 0.0001-0.01%, Cr: 11.0-13. In a ferritic stainless steel sheet consisting of 0%, N: 0.001 to 0.1%, Al: 0.0001 to 1.0%, Sn: 0.05 to 1.0%, the balance Fe and inevitable impurities, Γp defined by the following formula (2) satisfies the following formula (1).

10 ≦ γp ≦ 65 (1)
γp = 420C + 470N + 23Ni + 7Mn + 9Cu-11.5Cr
-11.5Si-52Al-69Sn + 189 (2)
Here, C, N, Ni, Mn, Cu, Cr, Si, Al, and Sn are the contents of each element.

  (I) The reason for limiting the component composition of the steel sheet of the present invention will be described first. Hereinafter, “%” means “mass%”.

  C is an element that degrades hot workability and weather resistance. In order to suppress deterioration of hot workability and weather resistance, the upper limit is made 0.3%. Since excessive reduction leads to an increase in refining costs, the lower limit is made 0.001%. Preferably, considering the manufacturability and weather resistance, the content is made 0.01 to 0.1%. More preferably, it is 0.02 to 0.07%.

  Si is an element that is effective as a deoxidizing element and enhances weather resistance. In order to obtain the effect of addition, 0.01% or more is added. Excessive addition causes a decrease in toughness and workability, so the upper limit is made 1.0%. Preferably, considering the addition effect and manufacturability, 0.1 to 0.6%. More preferably, it is 0.15 to 0.5%.

  Mn is an element that forms sulfides and inhibits weather resistance. In order to suppress deterioration of weather resistance, the upper limit is made 2.0%. Excessive reduction leads to an increase in refining costs, so the lower limit is made 0.01%. Preferably, considering the weather resistance and manufacturability, the content is made 0.05 to 0.6%. More preferably, it is 0.15 to 0.5%.

  P is an element that inhibits manufacturability and weldability. The upper limit is made 0.05% in order to suppress degradation of manufacturability and weldability. Since excessive reduction leads to an increase in refining costs, the lower limit is made 0.005%. Preferably, considering the manufacturing cost, the content is made 0.01 to 0.04%. More preferably, it is 0.01 to 0.03%.

  S is an element that deteriorates hot workability and weather resistance. In order to suppress deterioration of hot workability and weather resistance, the upper limit is made 0.02%. Since excessive reduction leads to an increase in refining costs, the lower limit is made 0.0001%. Preferably, considering the weather resistance and manufacturing cost, the content is made 0.0002 to 0.01%. More preferably, it is 0.0005 to 0.005%.

  Cr is an essential element for enhancing the weather resistance of the steel sheet of the present invention to which Sn is added. In order to obtain an effect of improving weather resistance, 11.0% or more is added. The upper limit is 13.0% from the viewpoints of manufacturability and corrosion resistance. Considering performance and alloy cost, 12.0 to 13.0% is preferable.

  N, like C, is an element that degrades weather resistance. In order to suppress deterioration of weather resistance, the upper limit is made 0.1%. Since excessive reduction leads to an increase in refining costs, the lower limit is made 0.001%. Preferably, considering the weather resistance and manufacturing cost, 0.01 to 0.05%. More preferably, it is 0.01 to 0.03%.

  Al, like Si, is an element that is effective for deoxidation and enhances weather resistance. In order to obtain the additive effect, 0.0001% or more is added. Excessive addition causes a decrease in toughness and weldability, so the upper limit is made 1.0%. Preferably, considering the addition effect and manufacturability, the content is made 0.001 to 0.5%. More preferably, it is 0.005 to 0.1%.

  Sn is an essential element for ensuring the target weather resistance without relying on rare metals such as Cr, Ni, and Mo. Sn is an element that acts as a ferrite forming element, reduces γp, and refines the solidified structure by the inoculation effect. Therefore, conventionally, the cracking of the steel ingot generated when γp is small can be improved by refining the solidified structure by adding Sn.

  In the steel sheet of the present invention, 0.05% or more is added to obtain the target weather resistance. The upper limit is 1.0% from the viewpoint of manufacturability. From the economical efficiency compared with SUS430, it is preferably more than 0.10 to 0.6%. Considering performance and alloy cost, more than 0.10 to 0.3% is more preferable.

  Mg, B, and Ca are elements that are effective in increasing the cleanliness or grain boundary strength of steel and improving the hot workability of Sn-added steel. If necessary, both are added in an amount of 0.0001% or more. However, if it exceeds 0.005%, the productivity is lowered. Preferably, considering the effect and manufacturability, the content is made 0.0003 to 0.003%.

  La, Y, Hf, and REM are elements that increase hot workability and steel cleanliness, and significantly improve weather resistance and hot workability. If necessary, both are added in an amount of 0.001% or more. However, excessive addition leads to an increase in alloy cost and a decrease in manufacturability, so in both cases the upper limit is set to 0.1%. Preferably, considering the effect of addition, economy, and manufacturability, the total of one or more types is 0.001 to 0.05%.

  Nb and Ti are elements that improve weather resistance by a stabilizing action of fixing C and N. If necessary, both are added in an amount of 0.01% or more. However, excessive addition leads to a decrease in manufacturability accompanying an increase in alloy costs and a recrystallization temperature. To do. Preferably, considering the addition effect, alloy cost, and manufacturability, the total of one or two of Nb and Ti is 0.02 to 0.2%.

  Ni, Cu, Mo, V, Zr, and Co are elements that enhance weather resistance by a synergistic effect with Sn. Although it adds as needed, Ni, Cu, and Mo all add 0.1% or more, and V, Zr, and Co all add 0.01% or more. Excessive addition leads to an increase in alloy costs and a decrease in manufacturability. Therefore, Ni, Cu, Mo, and V have an upper limit of 1.0%, and Zr and Co have an upper limit of 0.5%.

  (II) Next, γp defined by formula (2) and formula (1) for limiting the range of γp in order to ensure the hot workability of the Sn-added steel will be described. γp is an index indicating the maximum amount of austenite produced when heated to 1100 ° C. The present inventors experimentally obtained the effect of addition of Sn, and newly added the Sn term “−69Sn” to the empirical formula for estimating the maximum phase fraction of the γ phase described in Non-Patent Document 1. The following formula was obtained.

γp = 420C + 470N + 23Ni + 7Mn + 9Cu-11.5Cr
-11.5Si-52Al-69Sn + 189
Here, C, N, Ni, Mn, Cu, Cr, Si, Al, and Sn are the contents of each element.

  The experiment conducted by the present inventors, the result thereof, and the presumed action mechanism will be described. A 11-13% Cr steel containing 0.2% Sn was melted in a vacuum of 50 kg, a 42 mm thick block test piece was prepared from the cast steel ingot, left standing for one month, and then hot rolled. The experiment was conducted.

  In the hot rolling experiment, the block test piece was heated to 1120 ° C., a hot-rolled sheet having a total reduction ratio of 88% (8 passes), a finishing temperature of 700 to 900 ° C. and a thickness of 5 mm was manufactured. The presence or absence of the occurrence of ear cracks was investigated on the side, and the quality of hot workability was judged.

  Ear cracks occurred as γp increased, and the upper limit increased at 13% or less with 13% Cr as a boundary. Hot work cracks frequently occur at the phase boundary between the ferrite phase and the austenite phase generated at high temperatures. This is presumed that the formation of an austenite phase with low Sn solubility causes segregation to the austenite / ferrite grain boundaries in the process of being discharged to the ferrite phase side, resulting in a decrease in grain boundary strength. .

  When the amount of Cr is small, the deformation resistance at high temperature is small, so it is considered that the upper limit value of γp has increased. On the other hand, when γp is reduced, the ingot is cracked. Sn is an element that refines the solidified structure due to the inoculation effect as well as a ferrite forming element. Therefore, conventionally, the cracking of the steel ingot generated when γp is small can be improved by refining the solidified structure by adding Sn.

  In addition, the contribution of Sn as a ferrite-forming element is large compared with Cr despite the addition of a small amount. The present inventors determined that the ferrite forming ability at 1100 ° C. was 6 times that of Cr and the coefficient was “−69 (= −11.5 × 6)” based on the structure observation conducted in the experiment.

  Furthermore, a cold-rolled annealed sheet is produced with 0.2% Sn-added steel, SUS410L (12% Cr) and SUS430 (17% Cr) are used as comparative materials, and 35 ° C., 5% NaCl according to JIS Z 2371. A salt spray test using an aqueous solution was performed to evaluate weather resistance. The evaluation surface was polished by wet paper # 600 and the spraying time was 48 hours.

  SUS410L broke out in terms of evaluation, and the Sn-added 11-13% Cr steel did not fire as in SUS430. As a result, it was possible to confirm the effect of improving weather resistance by adding Sn.

In the steel sheet of the present invention, γp defined by the above formula (2) is limited by the following formula (1) in order to ensure the required hot workability.
10 ≦ γp ≦ 65 (1)

  As shown in the above formula (1), the target hot workability can be secured at γp65 or less when Cr is 13.0% or less. The target hot workability means that no ear cracks occur in the hot rolling experiment described above.

  Hot workability improves as γp decreases. However, when γp is excessively small, the cracking susceptibility becomes high, and hot working cracks due to the cracking are induced. Therefore, the lower limit of γp is 10 at Cr: 13.0% or less. Considering manufacturability, a preferable range is 15 ≦ γp ≦ 55 when Cr is 13.0% or less.

  (III) The reason for limiting the conditions in the method for producing the steel sheet of the present invention will be described.

  The heating temperature of the stainless steel slab to be subjected to hot rolling is set to 1100 ° C. or higher in order to suppress the formation of an austenite phase that induces hot work cracking and to reduce deformation resistance during hot rolling. If the heating temperature is excessively high, the surface properties deteriorate due to the coarsening of crystal grains, and the slab shape during heating may deteriorate, so the upper limit is set to 1300 ° C. From the viewpoint of hot workability and manufacturability, it is preferably 1150 to 1250 ° C.

  From the viewpoint of hot workability, the temperature at which the steel sheet after hot rolling is wound is 700 ° C. or higher in order to increase the heating temperature. When the temperature is lower than 700 ° C., there is a risk of inducing surface cracks during winding or a defective shape of the coil. If the coiling temperature is excessively increased, the formation of internal oxides and grain boundary oxidation are promoted, and the surface properties are lowered. Therefore, the upper limit is set to 1000 ° C. From the viewpoint of hot workability and manufacturability, the temperature is preferably 700 to 900 ° C.

  After hot rolling, annealing is performed or omitted, and one or more cold rolling or two or more cold rolling sandwiching intermediate annealing are performed. Annealing of the hot-rolled steel sheet is performed by continuous annealing or batch type box annealing at 700 ° C. or higher for promoting recrystallization. If the annealing temperature is excessively increased, the surface properties and pickling descaling properties are deteriorated, so the upper limit is set to 1000 ° C. From the viewpoint of surface properties, the temperature is preferably 700 to 900 ° C.

  Finish annealing after cold rolling is performed in an oxidizing atmosphere or a reducing atmosphere. The annealing temperature is preferably 700 to 900 ° C. in consideration of recrystallization, surface properties, and descaling properties. The pickling method is not particularly limited, and may be a method commonly used industrially. For example, alkaline salt bath immersion + electrolytic pickling + nitrohydrofluoric acid immersion may be performed, and the electrolytic pickling performs neutral salt electrolysis or nitric acid electrolysis.

  Next, examples of the present invention will be described. The conditions in the examples are one example of conditions used for confirming the feasibility and effects of the present invention, and the present invention is based on this one example of conditions. It is not limited. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

Example 1
Ferritic stainless steel having the composition shown in Table 1 is melted in 150 kg in a vacuum, the steel ingot is heated to 1000 to 1300 ° C. and subjected to hot rolling, wound at 500 to 700 ° C., and plate thickness A 3.0 to 6.0 mm hot-rolled steel sheet was produced.

  The hot-rolled steel sheet is annealed by simulating box annealing or continuous annealing, or is subjected to cold rolling twice or once with intermediate annealing, omitting the annealing, and a sheet thickness of 0.4-0. An 8 mm cold-rolled steel sheet was produced. The cold-rolled steel sheet was subjected to finish annealing at a temperature of 780 to 900 ° C. at which recrystallization was completed. In the finish annealing, oxidizing atmosphere annealing or bright annealing was performed. As comparative steels, SUS410L (12Cr) and SUS430 (17Cr) were used.

  The hot workability was evaluated by examining the presence or absence of the occurrence of ear cracks in the hot-rolled sheet. The case where no ear cracks occurred was indicated as “◯”, the case where ear cracks occurred from the end surface of the steel sheet to the surface was indicated as “X”, and the case where ear cracks did not reach the steel sheet surface was indicated as “Δ”.

  The weather resistance was evaluated by conducting a salt spray test in accordance with JIS Z 2371. The test condition was that the evaluation surface was polished by wet paper # 600 and the spraying time was 48 hours. The degree of occurrence of the comparative steel was “no occurrence” from SUS410L and “no occurrence” from SUS430. Therefore, the evaluation index, “no occurrence” equivalent to SUS430, was set as “◯”, and “with occurrence” was set as “x”.

  Further, an immersion test was performed in which the sample was immersed in a 0.5% NaCl aqueous solution at 80 ° C. for 168 hours to evaluate the weather resistance. The test piece was finished by polishing the entire surface with wet paper # 600. The degree of occurrence of the comparative steel was “entire occurrence” and “perforated” with SUS410L, and “entire occurrence” with SUS430. Therefore, the evaluation index is “◯” for the occurrence equivalent to SUS430. Those showing SUS410L equivalent puncture and perforation were marked with “x”.

  Table 2 summarizes the manufacturing conditions and test results.

  In Table 2, test numbers 1 to 3 and 7 to 26 are test examples relating to the ferritic stainless steel sheet that satisfies the component composition and γp defined in the present invention and the manufacturing conditions. In these steel plates, the target hot workability and the weather resistance equivalent to SUS430 are obtained.

  Test Nos. 4 to 6 are test examples relating to ferritic stainless steel sheets that have the component composition and γp specified in the present invention but deviate from the manufacturing conditions specified in the present invention. In these steel sheets, ear cracks could not be suppressed, but the target hot workability was obtained.

  Test numbers 27 to 32 are test examples relating to a ferritic stainless steel sheet in which the component composition and γp deviate from the component composition and γp defined in the present invention. In these steel sheets, the target hot workability and weather resistance or both are not obtained.

  Test Nos. 33 to 35 are test examples relating to ferritic stainless steel sheets having the component composition defined in the present invention, but γp deviating from the range of γp defined in the present invention. In these steel sheets, the target weather resistance is obtained, but the target hot workability is not obtained. Here, the test number 33 is a test example in which the crack due to the placement crack is manifested by hot working because γp is small.

  Test numbers 36 and 37 are reference examples according to SUS410L and SUS430, respectively.

  Here, FIG. 1 shows the relationship between γp and hot workability. It can be seen from FIG. 1 that γp must be adjusted to 10 to 65, preferably 15 to 55, in order to obtain good hot workability in Sn-added steel.

  According to the present invention, the corrosion resistance of low Cr ferritic stainless steel can be improved by effectively using Sn in a recycled iron source without depending on the use of rare metals, and can be applied to general durable consumer goods. An alloy-saving ferritic stainless steel sheet can be provided. Therefore, the present invention has high applicability in the production and use industries of stainless steel plates.

Claims (6)

In mass%, C: 0.001 to 0.3%, Si: 0.01 to 1.0%, Mn: 0.01 to 2.0%, P: 0.005 to 0.05%, S: 0.0001-0.01%, Cr: 11.0-13.0%, N: 0.001-0.1%, Al: 0.0001-1.0%, Sn: 0.05-1. Ferritic stainless steel sheet consisting of 0%, balance Fe and inevitable impurities, excellent in hot workability and weather resistance characterized by γp defined by the following formula (2) satisfying the following formula (1) Ferritic stainless steel sheet.
10 ≦ γp ≦ 65 (1)
γp = 420C + 470N + 23Ni + 7Mn + 9Cu-11.5Cr
-11.5Si-52Al-69Sn + 189 (2)
Here, C, N, Ni, Mn, Cu, Cr, Si, Al, and Sn are the contents of each element. The ferritic stainless steel sheet excellent in hot workability and weather resistance according to claim 1 , wherein the following formula (1 ′) is satisfied instead of the formula (1).
15 ≦ γp ≦ 55 (1 ′)   The ferritic stainless steel sheet is further, in mass%, Mg: 0.005% or less, B: 0.005% or less, Ca: 0.005% or less, La: 0.1% or less, Y: 0.1 % Or less, Hf: 0.1% or less, REM: 0.1% or less, or one or two or more of them are contained in hot workability and weather resistance according to claim 1 or 2 Excellent ferritic stainless steel sheet.   The ferritic stainless steel sheet is further mass%, Nb: 0.3% or less, Ti: 0.3% or less, Ni: 1.0% or less, Cu: 1.0% or less, Mo: 1.0 % Or less, V: 1.0% or less, Zr: 0.5% or less, Co: 0.5% or less, 1 type or 2 types or more are contained, The any one of Claims 1-3 characterized by the above-mentioned. A ferritic stainless steel sheet having excellent hot workability and weather resistance as described in the section.   The stainless steel slab having the component composition according to any one of claims 1 to 4 is heated to 1100 to 1300 ° C and subjected to hot rolling, and the steel plate after the hot rolling is finished is wound at 700 to 1000 ° C. A method for producing a ferritic stainless steel sheet excellent in hot workability and weather resistance, characterized by   The steel sheet after the hot rolling is not annealed, or is subjected to continuous annealing or box annealing at 700 to 1000 ° C., in hot workability and weather resistance according to claim 5. An excellent ferritic stainless steel sheet manufacturing method.

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