JP2012140687A - Ti CONTAINING FERRITIC STAINLESS STEEL HOT ROLLED COIL AND MANUFACTURING METHOD - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Ti containing ferritic stainless steel hot rolled coil of a thick gauge which has enough toughness and ductility which can stably prevent a problem of material crack in a line in which a hot rolled coil is developed to be rolled.SOLUTION: The Ti containing ferritic stainless steel hot rolled coil is such that a hardness is 180 HV or less, a Charpy impact value at 25°C is regulated at least 20 J/cm, and a sheet thickness is 5.0-12.0 mm. The hot rolled coil can be manufactured by a method as follows. A slab is hot rolled to be made to have a sheet thickness of 5.0-12.0 mm, then is taken-up at a winding temperature of 570°C or higher to be made a coil. When after the lapse of five minutes or longer from the taking-up end and a surface temperature of the coil circumference is 550°C or higher, the coil is soaked in water, and is retained for 15 minutes or longer.

Description

  The present invention is a “thick gauge” Ti-containing ferritic stainless steel hot-rolled coil or hot-rolled annealed coil having a thickness of 5 mm or more, which is a problem when the coil is unrolled through a production line. It has a good toughness and ductility that can stably prevent cracking. Moreover, it is related with the manufacturing method of such a hot-rolled coil or a hot-rolled annealing coil. In this specification, the “hot rolled coil” means a coil in which the steel strip after hot rolling is wound and cooled, and the “hot rolled annealing coil” is a steel strip after hot rolling. A coil that has been wound and cooled and then annealed and pickled.

  There are many uses for stainless steel products that use cold-rolled steel sheets as raw materials, but there are also uses that use "thick gauge" stainless steel sheets with a thickness of 5 to 12 mm as materials. For example, a flange used in a device in an automobile exhaust gas path is required to have corrosion resistance, heat resistance, and strength, and therefore, a stainless steel thick plate is used. Conventionally, austenitic stainless steel with good manufacturability has been applied, but replacement with ferritic stainless steel, which is advantageous in terms of thermal expansion coefficient and material cost, has been studied.

  For automotive exhaust gas path flange applications, it is advantageous to use steel grades with excellent corrosion resistance and heat resistance. An example of such a ferritic steel type is Ti-containing ferritic stainless steel. Ferritic stainless steel is prone to embrittlement at 475 ° C, and when a thick-gauge hot-rolled coil is manufactured, the next-line plate line (continuous annealing pickling line and rewinding to attach a dummy tail for preparation) When a coil is unrolled through a line in a line, etc., troubles that cause cracks in the steel strip are likely to occur. Since ferritic stainless steel containing Ti may help to reduce the toughness of hot-rolled coils, manufacturing a thick-gauge hot-rolled steel strip of Ti-containing ferritic stainless steel with existing mass production equipment very difficult.

JP-A 64-56822 Japanese Patent Publication No. 6-17516 JP-A-8-199237 Japanese Patent No. 3705391

Shoji Iwaoka, Nobuo Ohashi, “Development of Mass Production System for High-Purity Ferritic Stainless Steel”, Iron and Steel, 65th (1979) No. 14, pp. 2097-2103

  Various methods have been studied so far for improving the toughness of ferritic stainless steel hot-rolled materials to which Ti or Nb is added. Patent Document 1 discloses a technique in which the hot rolling finish temperature is increased according to the composition and the water is cooled rapidly after winding. Patent Document 2 discloses a method of rapidly cooling after hot rolling and winding at a temperature of 450 ° C. or lower. Patent Document 3 discloses a method of cooling after hot rolling and winding at as low a temperature as possible depending on the plate thickness. Patent Document 4 discloses a method for adjusting the content of C + N within a range in which a decrease in toughness is unlikely to occur, and particularly teaches that it is preferable to finish hot rolling at 800 ° C. or higher and to cool to at least 600 ° C. with water. . Non-Patent Document 1 discloses a technique in which the hot rolling end temperature is set to 900 ° C. or higher and the steel strip is immediately cooled in a water tank.

  These conventional techniques are effective in improving the toughness of hot rolled coils of ferritic stainless steel to which Ti or Nb is added. However, according to the investigation by the inventors, in the case of a hot-rolled coil of a thick gauge Ti-containing ferritic stainless steel, it is easy to stably prevent cracking when the coil is deployed even if the above-described conventional technology is applied. I understood that it was not. The same applies to hot-rolled annealing coils. That is, in the sheet-passing line that deploys the hot-rolled coil and the hot-rolled annealed coil, a crack may occur at a location where a relatively large amount of bending deformation is applied to the steel strip, which may be a problem.

  In view of such a problem, the present invention has a toughness and ductility sufficient to stably prevent the problem of material cracking in a line through which a hot-rolled coil or a hot-rolled annealed coil is expanded and passed, and contains Ti of a thick gauge An object of the present invention is to provide a ferritic stainless steel hot-rolled coil or hot-rolled annealed coil.

As a result of detailed studies, the inventors of the present invention have been able to stably prevent cracks in the through-plate line that deploys a thick gauge Ti-containing ferritic stainless steel hot-rolled coil and hot-rolled annealed coil.
(I) deter embrittlement at 475 ° C,
(Ii) removing hot-rolled strain;
Was found to be extremely effective.
The above (i) is what has been said in the past, but that alone is not sufficient as a crack prevention measure for thick-gauge hot-rolled coils and hot-rolled annealed coils, and (ii) It became clear that the thick gauge material can be prevented from cracking by synergistic action.

  Regarding (i) suppression of embrittlement at 475 ° C., it is basically necessary to adopt a method of shortening the residence time in the temperature range of around 475 ° C., and a considerable effect can be obtained even by the conventional technique. However, careful measures are required in order to provide toughness and ductility that can sufficiently withstand bending deformation when developing a thick gauge hot rolled coil or hot rolled annealed coil. Specifically, it was found that it is important to consider “recovery” after winding the coil. That is, if the coil wound in the hot rolling process is simply cooled in the water tank, the temperature at the center of the coil cannot be lowered sufficiently. A phenomenon of “recovery” occurs in which the temperature starts to rise. As a result, 475 ° C. embrittlement may occur. In order to prevent recuperation, it is extremely effective to immerse the wound coil in a water tank for 15 minutes or more.

  In order to remove the hot-rolled strain of (ii), after winding at as high a temperature as possible, do not immediately immerse the coil in a water tank, but hold it for a while at a high temperature to carry out “strain relief annealing”. Then, it is extremely effective to immerse in a water tank after that.

By these methods, a hot rolled coil having a hardness adjusted to 180 HV or less and a Charpy impact value at 25 ° C. of 20 J / cm ² or more can be obtained. Moreover, the hot rolled coil can be obtained by annealing and pickling the hot rolled coil in a continuous annealing pickling line to obtain a hot rolled annealed coil having a hardness adjusted to 165 HV or less and a Charpy impact value at 25 ° C. of 15 J / cm ² or more. it can. Such a hot-rolled coil and a hot-rolled annealed coil can be developed without being cracked in the next sheet passing line as they are, although they are thick gauges.
The present invention has been completed based on these findings.

That is, the above-mentioned object is mass%, C: 0.030% or less, Si: 2.00% or less, Mn: 2.00% or less, P: 0.050% or less, S: 0.040% or less, Cr : 10.0 to 25.00%, N: 0.030% or less, Ti: 0.01 to 0.50%, Ni: 2.00% or less, Mo: 2.50% or less as required Cu: 1.80% or less, Co: 0.50% or less, Al: 0.50% or less, W: 1.80% or less, V: 0.30% or less, Zr: 0.20% or less, B : 1.00% or less, REM (rare earth element): 0.100% or less, Ca: 0.0050% or less of one or more types, the balance of Fe and inevitable impurities, the composition is hard 180HV or less, thickness Charpy impact value is preferably 20 J / cm ² or more is adjusted to 22.5J / cm ² or more at 25 ° C. 5.0 It is accomplished by Ti-containing ferritic stainless steel hot rolled coils of 12.0 mm. Also, a Ti-containing ferritic stainless steel hot-rolled annealing coil having the above composition, having a hardness of 165 HV or less, and a Charpy impact value at 25 ° C. adjusted to 15 J / cm ² or more, and a plate thickness of 5.0 to 12.0 mm. This is achieved.

  Here, the above-mentioned hardness and Charpy impact value being “adjusted” within the above range means that the characteristics within the above numerical range are satisfied over the entire length of the steel strip wound in a coil shape. . The “total length of the steel strip” is a portion where the width of the steel strip is constant, and is a portion excluding both ends in the longitudinal direction of the steel strip that is cut and removed during line passing. “Hardness” is the surface hardness of the steel strip. As the “Charpy impact value”, a value measured according to JIS Z2242 using a 2 mm V notch impact test piece is adopted. The impact test piece is sampled so that its longitudinal direction coincides with the rolling direction of the steel strip and the movement direction of the hammer is the width direction of the steel strip.

  As a method for producing such a hot-rolled coil, a stainless steel slab having the above composition is hot-rolled to a plate thickness of 5.0 to 12.0 mm, and then a winding temperature of 570 ° C. or higher, preferably 730 ° C. or higher. Ti containing coil that is coiled and then immersed in water after 5 minutes or more have elapsed from the end of winding and the outermost surface temperature of the coil is 550 ° C. or more and kept in the water for 15 minutes or more A method for producing a ferritic stainless steel hot rolled coil is provided. Furthermore, a Ti-containing ferritic stainless steel hot-rolled annealing coil is provided that is subjected to annealing pickling in a continuous annealing pickling line for the Ti-containing ferritic stainless steel hot-rolled coil obtained by the above manufacturing method. Is done.

  According to the present invention, a Ti-containing ferritic stainless steel thick gauge hot-rolled coil or hot-rolled annealed coil that has excellent toughness and ductility can be provided. Conventionally, the thickness gauge hot-rolled coil or hot-rolled annealed coil of Ti-containing ferritic stainless steel has been difficult to provide for the line-passing plate. However, according to the present invention, this is possible. Therefore, the present invention can contribute to the widespread use of ferritic stainless steel materials in applications of thick plate members such as flanges used in apparatuses in automobile exhaust gas paths.

The graph which arranged the Charpy impact value in 25 degreeC of a hot-rolled coil according to the classification | category (Table 2) of hot-rolled coil manufacturing conditions. The graph which arranged the Vickers hardness of the hot-rolled coil according to the classification | category (Table 2) of hot-rolled coil manufacturing conditions. The graph which arranged the Charpy impact value in 25 degreeC of a hot-rolled annealing coil according to the classification | category (Table 2) of hot-rolling coil manufacturing conditions. The graph which arranged the Vickers hardness of the hot-rolled annealing coil according to the classification | category (Table 2) of hot-rolling coil manufacturing conditions.

In the following, “%” in the component elements means “mass%” unless otherwise specified.
[Chemical composition]
C is a factor that hardens the steel and lowers the toughness, so is limited to a content of 0.030% or less. However, it is not necessary to extremely reduce C, and the C content is usually 0.001 to 0.030%.

  Si and Mn are effective as deoxidizers and have an effect of improving high-temperature oxidation resistance. In particular, when emphasizing high-temperature oxidation resistance, it is more effective to secure a content of 0.05% or more for Si and 0.05% or more for Mn. However, if these elements are contained in a large amount, it becomes a factor that causes embrittlement of the steel. As a result of various studies, both Si and Mn are limited to contents of 2.00% or less. Each may be managed to be 1.00% or less, or 0.50% or less.

  If P and S are contained in a large amount, they may cause a decrease in corrosion resistance, so P is limited to 0.050% or less and S is limited to 0.040% or less. Usually, it may be in the range of P: 0.000 to 0.050% and S: 0.0005 to 0.040%. When emphasizing corrosion resistance, it is more effective to limit the S content to 0.005% or less.

  Cr is an important element for ensuring the corrosion resistance as stainless steel. It is also effective in improving high temperature oxidation resistance. In order to exert these effects, a Cr content of 10.00% or more is required. It is more effective to set the Cr content to 15.00% or more, or 17.00% or more. On the other hand, when a large amount of Cr is contained, the manufacturability of the thick gauge steel strip becomes difficult due to the hardening of the steel and the reduction in toughness. As a result of various studies, the Cr content is limited to 25.00% or less. You may manage to 22.00% or less or 20.00% or less.

  N is a factor that lowers toughness, so is limited to a content of 0.030% or less. However, it is not necessary to extremely reduce the N content, and the N content is usually 0.001 to 0.030%.

  Ti is an extremely effective element for suppressing the segregation of grain boundaries of Cr carbide / nitride by fixing C and N, and maintaining high corrosion resistance and high temperature oxidation resistance of steel. For this purpose, a Ti content of 0.01% or more is required. It is more effective to set it to 0.05% or more, and it is more effective to set it to 0.10% or more. However, excessive Ti content is not preferable because it promotes a decrease in toughness of the hot-rolled coil. As a result of various studies, the Ti content is limited to 0.50% or less.

  Ni has an action of suppressing the progress of corrosion, and can be added as necessary. In that case, it is more effective to secure a Ni content of 0.01% or more. However, since a large amount of Ni may adversely affect the workability, when Ni is added, it is necessary to be within a range of 2.00% or less, and may be controlled within a range of 1.00% or less. .

  Mo is an element effective for improving the corrosion resistance, and can be added as necessary. In that case, it is more effective to secure a Mo content of 0.02% or more, and it is more effective to set it to 0.50% or more. However, since a large amount of Mo has an adverse effect on toughness, when Mo is added, it is necessary to perform it in a range of 2.50% or less, and it may be controlled in a range of 1.50% or less.

  Cu is an element effective for improving low temperature toughness and workability. It is also effective for improving the high temperature strength. Therefore, Cu can be added as needed. In that case, it is more effective to secure a Cu content of 0.02% or more. However, when a large amount of Cu is added, the workability is rather lowered. When adding Cu, it is necessary to carry out in the range of 1.80% or less, and you may manage to content of 0.50% or less.

  Co is an element contributing to low temperature toughness, and can be added as necessary. In that case, it is more effective to secure a Co content of 0.010% or more. However, excessive addition causes a decrease in ductility. Therefore, when adding Co, the addition is performed within a range of 0.50% or less.

  Al is an element effective as a deoxidizer, and can be added as necessary. In that case, it is more effective to set the Al content to 0.005% or more. However, since a large amount of Al content causes a decrease in toughness, when Al is contained, the Al content is limited to 0.50% or less, and more preferably 0.20% or less.

  W and V are elements effective for improving the high-temperature strength, and one or more of them can be added as necessary. In that case, it is more effective to secure a content of 0.10% or more for W and 0.10% or more for V. However, when these elements are added in a large amount, the steel becomes hard and causes cracking when the steel strip passes through. When adding W, it is necessary to carry out in the range of 1.80% or less, and you may manage to content of 0.50% or less. When adding V, it is necessary to carry out in the range of 0.30% or less, and you may manage to 0.15% or less of content.

  Zr has an action of fixing C like Ti, and is an effective element for maintaining high corrosion resistance and high temperature oxidation resistance of steel. Therefore, Zr can be added as necessary. In that case, it is more effective to secure a Zr content of 0.02% or more. However, since a large amount of Zr is a factor that hinders workability, when Zr is added, it is necessary to perform the content within the range of 0.20% or less, and the content may be controlled to 0.10% or less. .

  B is an element that improves corrosion resistance and workability by addition of a small amount, and one or more of these can be added as necessary. In that case, it is more effective to secure a B content of 0.0001% or more. However, since excessive B content adversely affects hot workability, when B is added, it is performed in a range of 0.0050% or less.

  REM (rare earth element) and Ca are effective elements for improving high-temperature oxidation resistance, and one or more of them can be added as necessary. In that case, it is more effective to secure a content of 0.001% or more for REM and 0.0005% or more for Ca. However, since toughness decreases when a large amount of these elements are added, the content range is 0.100% or less when REM is added, and 0.0050% or less when Ca is added.

[Thickness]
In the case of a hot-rolled coil or hot-rolled annealed coil of Ti-containing ferritic stainless steel having the above composition, when the plate thickness is 5.0 mm or more, it is subjected to bending deformation by a roll during sheet passing in a general steel strip production line. Cracks tend to occur and often become a problem. On the other hand, in consideration of the plate passing ability of a general steel strip production line, it is impossible to pass a steel strip having a plate thickness exceeding 12.0 mm. Therefore, in the present invention, a hot rolled coil or a hot rolled annealed coil having a plate thickness of 5.0 to 12.0 mm is an object. You may manage to plate | board thickness of 5.5-9.0 mm.

〔mechanical nature〕
In order to prevent cracking when line-passing a thick gauge hot-rolled steel strip of Ti-containing ferritic stainless steel having the above composition, it is important that the material has good ductility and toughness. Ductility can be evaluated by hardness, and toughness can be evaluated by Charpy impact value at 25 ° C. As a result of detailed examination, in the case of a hot rolled coil, when the hardness is 180 HV or less and the Charpy impact value at 25 ° C. is 20 J / cm ² or more over the entire length of the coil, the thickness of the next process is as it is up to 12.0 mm. It is possible to pass through the lines without causing cracks. The Charpy impact value at 25 ° C. is more preferably 22.5 J / cm ² or more. In that case, the degree of freedom of the sheet passing conditions (for example, line speed) is expanded, leading to an improvement in productivity. In the case of a hot-rolled annealed coil, when the hardness is 165 HV or less and the Charpy impact value at 25 ° C. is 15 J / cm ² or more over the entire length of the coil, the thickness of the coil reaches 12.0 mm as it is in the next process line. It is possible to let the plate pass without causing cracks.

[Manufacture of hot rolled coils]
Hot rolling is performed by a series of processes in which a slab is heated and then extracted, subjected to a plurality of passes of reduction to form a steel strip having a thickness of 5.0 to 12.0 mm, and wound. However, it is important that the winding temperature is 570 ° C. or higher. If the coiling temperature is lower than that, the effect of “strain relief annealing” performed using the standing time after coiling will not be sufficiently exerted, resulting in a decrease in ductility. Further, embrittlement at 475 ° C. is likely to occur during the standing time after winding. Accordingly, the winding temperature needs to be 570 ° C. or higher, but more preferably 600 ° C. or higher. In particular, if the coiling is performed at a high temperature of 730 ° C. or higher, the effect of “strain relief annealing” can be exhibited more remarkably, and high toughness can be obtained more stably. The heating temperature is, for example, 1180 to 1260 ° C., and the finish rolling temperature (material surface temperature on the roll exit side of the final rolling pass) is, for example, 800 ° C. or higher, preferably 900 ° C. or higher.

  After winding, it is necessary not to immediately cool the coil with water, but to leave it for a while (keep it in the atmosphere). The “strain relief annealing” is performed to remove the hot-rolled strain by using the standing time. As a result of various studies, hot rolling strain is effectively removed by securing a time of 5 minutes or more after the end of winding until water cooling. However, if left for too long, embrittlement occurs at 475 ° C. Therefore, water cooling is started when the surface temperature of the outermost periphery of the coil is 550 ° C. or higher. In the case of a coil having a mass of 10 tons or more, the surface temperature of the outermost periphery can be maintained at 550 ° C. or higher while keeping the winding time at 570 ° C. or higher and leaving the standing time at 5 minutes or longer. In the case of a small-scale coil, the temperature drop during the standing time becomes large. Therefore, the winding temperature is set to, for example, 600 ° C. or higher, the standing time is set to 5 minutes or more, and the outermost surface temperature 550 is set. What is necessary is just to satisfy | fill the conditions more than ℃. More preferably, the standing time is 8 minutes or more.

  Water cooling of the coil is performed by immersing the entire coil in water in a water tank. It is important that the immersion time is 15 minutes or longer. If the immersion time is shorter than that, the above-mentioned “recovery” phenomenon may occur after taking out from the water tank, resulting in 475 ° C. embrittlement. The immersion time is more preferably 30 minutes or longer.

[Manufacture of hot-rolled annealing coils]
The hot-rolled coil manufactured according to the above method is attached to the dummy tail and the surface flaws on the rewind line as necessary, and then passed through the continuous annealing pickling line, can do. As an annealing condition in the continuous annealing pickling line, for example, a condition of cooling to 900 to 1100 ° C. and then cooling at an average cooling rate from the heating temperature to 400 ° C. at 50 ° C./sec or more is preferable.

  Steel shown in Table 1 was melted to form a continuous cast slab, and a hot rolled coil having a plate thickness of 8 mm was produced by a continuous hot rolling line. All the steels shown in Table 1 satisfy the chemical composition defined in the present invention. Table 2 shows the hot rolled coil manufacturing conditions. Water cooling of the hot rolled coil was performed by a method of immersing the hot rolled coil in water in a water tank. In Table 1, slab heating temperature, finish rolling temperature, and coiling temperature are specifically described among the hot rolled coil manufacturing conditions.

  The water in the water tank is circulated by the power of the pump, and water is appropriately replenished so that the entire hot rolled coil is always submerged. In the case of performing immersion in a water bath, the immersion was not started immediately after winding, but was allowed to stand for 5 minutes or longer (time exposed to the atmosphere), and then the immersion was started. However, No. 19 in Table 1 was left for 2 minutes. The immersion time in the water tank was 15 minutes or longer. However, No. 20 of Table 1 made immersion time 7 minutes.

  Samples were taken from the outermost and innermost circumferences of the obtained hot-rolled coil, and Charpy impact test pieces and hardness were measured from the vicinity of the steel strip width direction end (edge part) and the width direction center of each sample. A test specimen for measurement was cut out. Hardness measurement and Charpy impact test at 25 ° C. were carried out by the method described above. And about each coil, the numerical value with the worst result was employ | adopted as the characteristic value (henceforth "evaluation characteristic value") of the coil among all the measured values of the outermost peripheral part and the innermost peripheral part. Specifically, for the Charpy impact value, the smallest value among the obtained measured values was set as the evaluation characteristic value, and for the hardness, the largest value among the measured values of the Vickers hardness was set as the evaluation characteristic value. As a result, for example, a decrease in toughness and ductility in the inner periphery of the coil when “recuperation” occurs, and a decrease in toughness and ductility when “strain relief annealing” becomes insufficient in the outer periphery of the coil are obtained. The soundness of the entire belt length can be evaluated.

  FIG. 1 and FIG. 2 show the Charpy impact value and hardness (both evaluated characteristic values described above) at 25 ° C. of the hot-rolled coil, respectively.

  The condition of classification A is in accordance with a general ferritic stainless steel hot-rolled coil manufacturing method that does not perform a special cooling operation after finishing rolling, but the winding temperature is higher than the 475 ° C embrittlement temperature. 475 ° C. embrittlement occurred in the temperature lowering process after winding, resulting in a decrease in toughness (Charpy impact value) and hardening. Since it is difficult to use it as it is in this state, special processing such as rapid cooling after batch annealing is required for commercialization.

  The condition of classification B is that the steel strip after finish rolling is water-cooled and wound at a temperature lower than the 475 ° C. embrittlement region. This method has been known to be effective in avoiding or reducing embrittlement at 475 ° C. Conventionally, if it is a general hot-rolled coil having a thickness of less than 5 mm, it can be used as it is for a line passing plate. is there. However, since the material hardens due to the remaining hot-rolling strain, in the case of a thick-gauge hot-rolled coil, it is difficult to pass the line as it is.

  The condition of the classification C is that the coil obtained under the condition of the classification B is immersed in water and cooled. In this case as well, the point where hot-rolled strain remains is the same as in category B, and the water cooling of the coil does not contribute to the improvement of toughness and ductility.

On the other hand, the condition of classification D is that the film is wound at a temperature of 570 ° C. or higher, secured for 5 minutes or longer, and then immersed in a water tank from a temperature range of 550 ° C. or higher and water-cooled for 15 minutes or longer. The effect of “strain relief annealing” was obtained by leaving for 5 minutes or more, and 475 ° C. embrittlement due to “recuperation” was also avoided by immersion in water for 15 minutes or more. This confirmed that good toughness with Charpy impact value of 20 J / cm ² or more and softening of 180 HV or less were realized.

In the condition of class E, the coiling temperature is controlled to a high temperature of 730 ° C. or more in the condition of class D. As a result, a better toughness with a Charpy impact value of 22.5 J / cm ² or more was obtained.

  When a hot rolling coil manufactured according to the conditions of classification D and E was passed through a line and expanded, and then wound on the exit side of the line, a rewinding experiment was conducted. It was confirmed that troubles that would interfere with the situation did not occur.

The coil manufactured under the condition of classification D1 has a relatively hard finish due to insufficient removal of hot-rolled strain due to the short standing time after winding.
Coils produced under the conditions of classification D2 were considered to have “recuperated” because of the short immersion time in the water tank, and a decrease in toughness and ductility due to 475 ° C. embrittlement was observed on the inner circumference side of the coils. .

The hot rolled coil produced in Example 1 was passed through a continuous annealing pickling line to obtain a hot rolled annealed coil. As the annealing conditions, various conditions were adopted as long as the conditions for cooling after heating at 900 to 1100 ° C. and the average cooling rate from the heating temperature to 400 ° C. being 50 ° C./sec or more were satisfied. About the obtained hot-rolled annealing coil, the Charpy impact value and the evaluation characteristic value of Vickers hardness were calculated | required similarly to the above. As a result, it was confirmed that all hot-rolled annealed coils derived from hot-rolled coils manufactured under the conditions of classifications D and E according to the present invention satisfy the characteristics of Charpy impact value of 15 J / cm ² or more and hardness of 165 HV or less. It was done.

  FIG. 3 shows Charpy impact values of hot-rolled annealed coils manufactured under various annealing conditions using hot-rolled coils of No. 7 (Category C) and Nos. 8, 10, 21 (Category D) in Table 1 (above (Evaluation characteristic value). Further, in FIG. 4, various annealing conditions using the hot rolled coils of No. 5, 6 (Category B), No. 7 (Category C) and Nos. 8, 10, 21 (Category D) of Table 1 are shown. The hardness (above-mentioned evaluation characteristic value) of the manufactured hot-rolled annealing coil is illustrated.

  Various Ti-containing ferritic stainless steels having the same composition as the invention examples shown in Table 1 are melted in the laboratory, and the thicknesses are determined under the conditions of the above classifications D and E assuming the conditions for producing hot-rolled coils in a mass production line. A 12.0 mm hot-rolled sheet was produced. About the obtained hot-rolled sheet, the bending test which assumed the bending deformation in the sheet-passing line which has the capability which can pass the hot-rolled steel strip of 12 mm in thickness was implemented. As a result, all the samples were evaluated as having toughness and ductility so as to avoid troubles when passing through a hot rolled coil having a plate thickness of 12.0 mm.

Claims (9)

In mass%, C: 0.030% or less, Si: 2.00% or less, Mn: 2.00% or less, P: 0.050% or less, S: 0.040% or less, Cr: 10.0-00 20.00%, N: 0.030% or less, Ti: 0.01 to 0.50%, balance Fe and unavoidable impurities, hardness is 180HV or less, Charpy impact value at 25 ° C A Ti-containing ferritic stainless steel hot-rolled coil having a plate thickness of 5.0 to 12.0 mm adjusted to 20 J / cm ² or more.   Furthermore, Ni: 2.00% or less, Mo: 2.50% or less, Cu: 1.80% or less, Co: 0.50% or less, Al: 0.50% or less, W: 1.80% or less, V: 0.30% or less, Zr: 0.20% or less, B: 0.0050% or less, REM (rare earth element): 0.100% or less, Ca: 0.0050% or less. The Ti-containing ferritic stainless steel hot-rolled coil according to claim 1 having a composition. The Ti-containing ferritic stainless steel hot-rolled coil according to claim 1 or 2, wherein a Charpy impact value at 25 ° C is adjusted to 22.5 J / cm ² or more. In mass%, C: 0.030% or less, Si: 2.00% or less, Mn: 2.00% or less, P: 0.050% or less, S: 0.040% or less, Cr: 10.0-00 20.00%, N: 0.030% or less, Ti: 0.01 to 0.50%, balance Fe and inevitable impurities, hardness is 165HV or less, Charpy impact value at 25 ° C A Ti-containing ferritic stainless steel hot-rolled annealing coil having a plate thickness of 5.0 to 12.0 mm adjusted to 15 J / cm ² or more.   Furthermore, Ni: 2.00% or less, Mo: 2.50% or less, Cu: 1.80% or less, Co: 0.50% or less, Al: 0.50% or less, W: 1.80% or less, V: 0.30% or less, Zr: 0.20% or less, B: 0.0050% or less, REM (rare earth element): 0.100% or less, Ca: 0.0050% or less. The Ti-containing ferritic stainless steel hot-rolled annealing coil according to claim 4 having a composition.   In mass%, C: 0.030% or less, Si: 2.00% or less, Mn: 2.00% or less, P: 0.050% or less, S: 0.040% or less, Cr: 10.0-00 A stainless steel slab having a composition comprising 25.00%, N: 0.030% or less, Ti: 0.01 to 0.50%, the balance Fe and unavoidable impurities is hot-rolled to a thickness of 5.0 to 12 The coil is wound at a winding temperature of 570 ° C. or higher after setting to 0.0 mm, and the coil is immersed in water after 5 minutes or more have elapsed from the end of winding and when the outermost surface temperature of the coil is 550 ° C. or higher. A method for producing a Ti-containing ferritic stainless steel hot-rolled coil that is kept in the water for 15 minutes or longer.   The stainless steel slab is further made of Ni: 2.00% or less, Mo: 2.50% or less, Cu: 1.80% or less, Co: 0.50% or less, Al: 0.50% or less, W: 1 1.80% or less, V: 0.30% or less, Zr: 0.20% or less, B: 0.0050% or less, REM (rare earth element): 0.100% or less, Ca: 0.0050% or less The method for producing a Ti-containing ferritic stainless steel hot-rolled coil according to claim 6, which has a composition containing at least a seed.   The method for producing a Ti-containing ferritic stainless steel hot-rolled coil according to claim 6 or 7, wherein the coiling temperature is 730 ° C or higher.   The Ti-containing ferritic stainless steel hot-rolled by subjecting the Ti-containing ferritic stainless steel hot-rolled coil obtained by the manufacturing method according to any one of claims 6 to 8 to annealing pickling in a continuous annealing pickling line. An annealing coil manufacturing method.

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