JP2010229457A - Ferritic-austenitic stainless steel having excellent ingot crack resistance and method of manufacturing steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing ferritic-austenitic stainless steel by a continuous casting method in which the composition of steel is regulated and by which a hot rolled steel sheet is efficiently manufactured without causing slab crack by a hot charge method requiring no composition heat maintaining furnace. <P>SOLUTION: The steel sheet contains, in mass%, ≤0.10% C, ≤2.0% Si, ≤4.0% Mn, <0.05% P, <0.010% S, 17-25% Cr, 0.60-5.00% Ni, 0.010-0.150% N, 0.01-0.1% Al and the balance iron and inevitable impurities, wherein DF value is controlled to 70-85. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a ferritic / austenitic stainless steel excellent in crack resistance and a method for producing the steel plate. According to the present invention, ferritic / austenitic stainless steel having excellent slab cracking resistance can be produced without containing a large amount of expensive and rare element Ni, which contributes to resource protection and environmental conservation. It is thought that it is possible.

  Stainless steel can be broadly classified into austenitic stainless steel, ferritic stainless steel, and two-phase (ferrite / austenite) stainless steel. Austenitic stainless steel contains 7% or more of Ni, and many steel types are excellent in formability. Ferritic stainless steel contains little Ni and generally has a much lower formability than austenitic stainless steel. On the other hand, two-phase (ferrite / austenite) stainless steels have so far many steel types that have an intermediate position between austenitic stainless steels and ferritic stainless steels in terms of formability and corrosion resistance. However, in recent years, a technology having formability close to that of austenitic stainless steel has also been developed in ferritic / austenitic stainless steels by utilizing the work-induced martensitic transformation of the austenitic phase during plastic working. Patent Document 1 describes a technique in which the tensile elongation at break is increased by the TRIP phenomenon using a stainless steel containing a retained austenite phase whose main constituent phase is a ferrite phase. Patent Document 2 describes a method of increasing the tensile elongation by defining the stability of the austenite phase. Patent Document 3 discloses a technique for increasing the total elongation in a tensile test by defining the austenite phase fraction and the amounts of C and N in the austenite phase.

  In general, ferrite-austenitic stainless steel is known to exhibit a tendency that a large amount of ferrite-forming elements such as Cr are contained in the ferrite phase because the elements are distributed in each of the ferrite phase and the austenite phase. Ferritic stainless steel containing a large amount of Cr is recognized as a problem during production because of poor toughness, and it can be easily estimated that the same phenomenon occurs in the ferrite phase of ferrite-austenitic stainless steel.

  Here, the ferritic stainless steel sheet having a relatively low Cr content of around 20% is generally manufactured by a continuous casting method with high manufacturing efficiency. In this method, slabs are formed by continuous casting, then cut and stacked to a length of about 10 m, and kept warm by a heat insulating cover to prevent the temperature from dropping until the next furnace is inserted. Then, a method of hot rolling by heating in a heating furnace, a so-called hot charge method is employed.

  However, it takes a considerable time for the cut slab to be inserted into the heating furnace. That is, it is necessary to take care of removing surface flaws between cutting and next heating, or to wait until a rolling chance, and in some cases, it takes 20 hours from cutting to inserting the heating furnace. There is. In the case of low Cr ferritic stainless steel, the transition temperature is low, so the slab temperature will be lower than the transition temperature even if the slab is stacked and the insulation cover is applied with a heat insulating material, even if the time from cutting to insertion of the furnace is long. The slab will not crack due to residual stress.

  The continuous cast slab is sprayed with spray water until solidification is completed from the lower part of the mold to promote solidification. However, a large internal stress is generated by this cooling. Further, since the wall thickness is as thin as about 200 mm, the temperature is likely to decrease, and steel with poor toughness is very disadvantageous for cracking of the slab.

  As described above, high Cr ferritic stainless steel exceeding 20% has low toughness and a transition temperature of about 400 to 500 ° C. When the hot charge method in normal continuous casting is applied to high Cr ferritic stainless steel, the slab temperature falls below the transition temperature between slab cutting and heating furnace insertion, and transverse cracks occur in the slab. was there.

  Large transverse cracks are thought to be generated by thermal stress starting from some defects when the toughness of the slab is poor. Once transverse cracking occurs, the slab may fall out of the conveying device in the heating furnace, making extraction impossible, and the effect on the heating furnace operation is significant.

  Patent Document 4 discloses a method in which a continuous cast slab is heated by hot ingot direct feeding and hot-rolled for high-purity ferritic stainless steel containing 10 to 30% Cr. The transition temperature of this ferritic stainless steel is described to be about 300 ° C., but when it contains 25% or more of high Cr, it is estimated that the transition temperature is 300 ° C. or more. In order to prevent the temperature drop of the slab after cutting, it must be inserted into a large-capacity heat-retaining furnace, and expensive equipment is required.

  Therefore, Patent Document 5 describes a method for reducing the transverse cracking sensitivity by setting the transition temperature to 300 ° C. or less by adding Nb and the amount of C + N to 0.015% or less so as not to require a heat insulation furnace. This method is effective because there is no change in the composition of the ferrite phase if it is a ferritic stainless steel having a ferrite single-phase structure, but in the case of a ferrite-austenitic stainless steel, the composition of the ferrite phase changes with the temperature change during production. Therefore, the transverse cracks generated in the ferrite phase could not be completely prevented.

JP-A-10-219407 JP-A-11-71643 JP 2006-169622 A Japanese Examined Patent Publication No. 61-44121 JP-A-8-25313

  In view of the above-described problems, in the present invention, a slab is manufactured by a continuous casting method of ferrite-austenitic stainless steel having a Cr content of 17 to 25%, and the slab is manufactured by a hot charge method that does not require a heat-retaining furnace An object of the present invention is to provide a ferritic / austenitic stainless steel and a method for producing a hot-rolled steel sheet that are capable of efficiently producing a hot-rolled steel sheet without causing cracks in the steel and excellent in crack resistance.

  When the present inventors apply ferritic-austenitic stainless steel to continuous casting, the temperature of the slab becomes 300 ° C. or lower after being cut into a slab and heated for hot rolling. However, in order to prevent cracks from occurring, the component composition of ferrite-austenitic stainless steel was studied intensively using a lab ingot in order to set the transition temperature to 300 ° C. or lower. As a result, the present inventors have found that there is a combination of components in which no cracks are generated, and completed the present invention.

  The gist of the present invention is as follows.

(1) In mass%,
C: 0.10% or less,
Si: 2.0% or less,
Mn: 4.0% or less,
P: 0.050% or less,
S: 0.010% or less,
Cr: 17 to 25%,
Ni: 0.6 to 5.0%,
Cu: 2.0% or less,
Mo: 2.0% or less,
N: 0.01 to 0.15%,
Al: 0.01-0.2%
Ferritic / austenitic stainless steel with excellent crack resistance, wherein the balance is iron and inevitable impurities, and the DF value represented by the following formula (1) is 70 to 85.
DF value = 7.2 × (Cr + 0.88 × Mo + 0.78 × Si)
−8.9 × (Ni + 0.03 × Mn + 0.72 × Cu + 22 × C + 21 × N) − 44.9 Formula (1)

(2) Furthermore, in mass%,
Nb: 0.50% or less,
Ti: 0.50% or less,
The ferritic / austenitic stainless steel with excellent crack resistance according to claim 1, characterized in that it contains one or two of the following.

(3) Furthermore, in mass%,
Ca: 0.003% or less,
Mg: 0.003% or less,
B: 0.003% or less,
The ferritic / austenitic stainless steel with excellent crack resistance according to claim 1, wherein the ferritic / austenitic stainless steel is excellent.

(4) By mass%
C: 0.10% or less,
Si: 2.0% or less,
Mn: 4.0% or less,
P: 0.050% or less,
S: 0.010% or less,
Cr: 17 to 25%,
Ni: 0.6 to 5.0%,
Cu: 2.0% or less,
Mo: 2.0% or less,
N: 0.01 to 0.15%,
Al: 0.01-0.2%
The balance is made of iron and unavoidable impurities, and the DF value of 70 to 85 represented by the following formula (1) is made into a slab by continuous casting, and continuously below its impact transition temperature. A method for producing a ferritic / austenitic stainless steel sheet having excellent crack resistance, which is characterized by heating without cooling to hot rolling and then hot rolling.
DF value = 7.2 × (Cr + 0.88 × Mo + 0.78 × Si)
−8.9 × (Ni + 0.03 × Mn + 0.72 × Cu + 22 × C +
21 * N) -44.9 (1) Formula

(5) The slab is further in mass%,
Nb: 0.50% or less,
Ti: 0.50% or less,
1 or 2 types of these are contained, The manufacturing method of the ferritic-austenitic stainless steel plate excellent in the placement crack resistance of Claim 4 characterized by the above-mentioned.

(6) The slab is further in mass%,
Ca: 0.003% or less,
Mg: 0.003% or less,
B: 0.003% or less,
1 or 2 types of these are contained, The manufacturing method of the ferritic-austenitic stainless steel plate excellent in the placement crack resistance in any one of Claim 4 or 5 characterized by the above-mentioned.

  Hereinafter, the inventions related to the steels (1) to (6) are referred to as the present invention. The inventions (1) to (6) may be collectively referred to as the present invention.

  According to the present invention, a ferrite and austenitic stainless steel sheet that does not contain a large amount of Ni, which is an expensive and rare element, efficiently without causing cracks in the slab by a hot charge method that does not require a heat-retaining furnace. Since it can be manufactured, it greatly contributes to resource protection and environmental protection.

It is a figure which shows the influence which it has on the impact characteristic of DF value. It is a figure which shows the relationship between the cooling temperature of an ingot, and cooling time.

When the present inventors apply ferritic-austenitic stainless steel to continuous casting, the temperature of the slab becomes 300 ° C. or less after being cut into a slab and heated for hot rolling. However, in order to prevent cracks from occurring, the component composition of ferrite-austenitic stainless steel was intensively studied using a lab ingot to reduce the transition temperature to 300 ° C. or less. As a result, it was found that there was a combination of components in which no cracks occurred, and the DF value shown in the following formula (1) constituting the relationship was reached.
DF value = 7.2 × (Cr + 0.88 × Mo + 0.78 × Si)
−8.9 × (Ni + 0.03 × Mn + 0.72 × Cu + 22 × C + 21 × N) − 44.9 (1) Formula DF value is an element that stabilizes the ferrite phase and an element that stabilizes the austenite phase. Since the relationship is constructed, the effect of each element is influenced by the mutual relationship between the elements, so the coefficients are different. By limiting the DF value within the range of 70 to 85, the inventors have found that the transition temperature can be lowered to 300 ° C. or lower, and further to 200 ° C. or lower. Below, the typical experimental result is demonstrated.

  First, the DF value that is an index of an alloy element that is an important element of the present invention will be described.

  DF value 70 to 85: The metal structure of ferrite-austenitic stainless steel is composed of two phases, a ferrite phase and an austenite phase. The reason for being two phases at room temperature is that the composition contained in each phase (especially the element having a large diffusion rate such as N) is greatly influenced, and the composition tends to approach the equilibrium state in each temperature range during the cooling process from solidification to room temperature. This is because of the continuous distribution and organization. The relationship between the DF value and the transition temperature is shown in FIG. When the DF value exceeds 85, the temperature of the ingot becomes lower than the transition temperature even when the hot charge method is applied, and cracks can be observed on the surface of the ingot, and the length that can be observed on the surface becomes large. Therefore, the upper limit of the DF value is set to 85. When cooling to room temperature and observing cracks on the ingot surface, cracks are observed even when the DF value is less than 85, and cracks cannot be observed at a DF value of 70. Therefore, the lower limit of the DF value is set to 70. Therefore, the range of the present invention is a DF value of 70 to 85 at which cracking does not occur by applying the hot charge method. Here, since the DF value indicates the relationship between the element that stabilizes the ferrite phase and the element that stabilizes the austenite phase, when the DF value is 70 or less, the ratio of the austenite-forming element slightly contained in the ferrite phase Therefore, it can be estimated that the toughness of the ferrite phase is improved and it is not necessary to apply the hot charge method. Therefore, in the present invention, a DF value of 70 or less is outside the present invention.

  The reasons for limiting the components are described below. In addition, "%" shown below represents mass%.

(C: 0.10% or less)
C is an element that greatly affects the stability of the austenite phase. If the content exceeds 0.10%, the hardness of the austenite phase may remarkably increase. Further, in order to promote the precipitation of Cr carbide, it causes the occurrence of intergranular corrosion, so the upper limit was made 0.10%. Moreover, although it is more preferable to make C low from a corrosion-resistant point, in order to reduce, the cost increase at the time of refining will be caused. Preferably, it is 0.01 to 0.04% of range, and more preferably 0.025 to 0.04% of range.

(Si: 2.0% or less)
Si may be used as a deoxidizing element or may be contained for improving oxidation resistance. However, if the content exceeds 2.0%, the material is hardened and the uniform elongation is lowered, so this was made the upper limit. Moreover, in order to reduce Si extremely, the cost at the time of refining is increased. Preferably, it is in the range of 0.05 to 1.0%, and more preferably in the range of 0.4 to 1.0%.

(Mn :: 4.0% or less)
Mn concentrates in the austenite phase and plays an important role in changing the stability of the austenite phase. However, a large amount causes a decrease in corrosion resistance and hot workability, so the upper limit was made 4.0%. In order to make it less than 0.05%, the cost in the smelting process is increased, so the lower limit is desirably made 0.05%. From the viewpoint of corrosion resistance, a lower value is preferable, and the upper limit is preferably set to 3.0%.

(P: 0.050% or less)
P is an element that is inevitably mixed and is difficult to reduce because it is contained in a raw material such as Cr. Less than 050%.

(S: 0.010% or less)
Since S may combine with Mn to form inclusions and serve as a starting point for rusting, the upper limit was made less than 0.010%. Since it is preferable from the viewpoint of corrosion resistance, the lower the content, the lower the content of 0.003%.

(Cr: 17-25%)
Cr is an element necessary for ensuring corrosion resistance and needs to be contained in an amount of 17% or more. However, a large amount causes hot working cracks and leads to an increase in the cost of the refining process, so the upper limit was made 25%. Preferably, it is 20 to 23% of range.

(Ni: 0.6-5.0%)
Ni is an austenite stabilizing element and is an important element for adjusting the stability of the austenite phase. Moreover, since it has an effect which suppresses a hot work crack, it is made to contain 0.6% or more. If the content exceeds 5.0%, the raw material cost increases, and it may be difficult to obtain a two-phase structure of austenite and ferrite, so this was made the upper limit. Preferably, it is 0.6 to 2.4% of range. More preferably, it is 0.6 to 2.2% of range.

(N: 0.01-0.15%)
N, like C, is an element that greatly affects the stability of the austenite phase. Moreover, since it has the effect of improving corrosion resistance when it exists in solid solution, it shall contain 0.01 or more. However, when the content is 0.15% or more, the uniform elongation may be reduced, and Cr nitride is liable to precipitate and conversely causes a decrease in corrosion resistance. In order to obtain an effect stably, 0.06 or more is preferable.

(Cu: 2.0% or less)
Cu, like Ni, is an austenite stabilizing element, and is an important element for adjusting the stability of the austenite phase. However, if the content exceeds 2.0%, cracking during hot working is promoted and the strength is increased, so this was made the upper limit. In order to obtain an effect stably, 0.1% or more is preferable.

(Mo: 2.0% or less)
Since Mo is an element that improves the corrosion resistance, it may be selectively contained. By containing 0.1% or more, the corrosion resistance improving effect is exhibited. In order to obtain an effect stably, 0.5% or more is preferable. However, when it exceeds 2.0%, the uniform elongation is lowered and the raw material cost is greatly increased.

(Al: 0.01-0.2%)
Al is an element having a very large deoxidizing ability of steel, and must be added from the viewpoint of improving the toughness of the ferrite phase. In order to reduce oxide inclusions by deoxidation and obtain high toughness, a content of 0.01% or more is necessary. On the other hand, excessive addition leads to hardening of the steel and may deteriorate the workability, so the content is made 0.2% or less. Preferably, it is 0.02 to 0.1% of range.

  Moreover, the following elements can be selectively contained.

(One or two of Nb: 0.50% or less, Ti: 0.50% or less)
Nb has the effect of preventing the weld heat-affected zone from becoming coarse, but the content exceeding 0.50% lowers the uniform elongation, so this was made the upper limit. In order to obtain an effect stably, 0.03% or more is desirable.

  Ti, like Nb, has an effect of preventing the weld heat affected zone from becoming coarse. Furthermore, the content is preferably 0.03% or more in order to finely equiax the solidified structure. However, the content exceeding 0.50% lowers the uniform elongation, so this was made the upper limit.

(Ca: 0.003% or less, Mg: 0.003% or less, B: 0.003% or less)
Ca may be slightly contained for desulfurization and deoxidation. However, the content of over 0.003% tends to cause hot working cracks and lowers the corrosion resistance, so this was made the upper limit. To obtain a stable effect. 0.0005% or more is desirable.

  Mg has not only deoxidation but also an effect of refining the solidified structure. In order to stably exhibit these effects, the content is preferably 0.0005% or more. Moreover, since content exceeding 0.003% brings about the cost increase in a steelmaking process, this was made into the upper limit.

  B is an element effective for increasing the grain boundary strength. In order to stably exhibit such an effect, the content is preferably 0.0005% or more. Further, if the content exceeds 0.003%, a large amount of boride is formed, and the corrosion resistance is remarkably lowered.

Next, the reason for heating without cooling below the impact transition temperature will be described.
When the slab is cooled to below the transition temperature after casting and heated, the tensile stress inside the slab exceeds the yield stress and the slab cracks, so the slab must be heated at a temperature above the transition temperature. I must. The impact transition temperature of a continuously cast slab cannot be measured during the manufacturing process, but can be obtained by cutting a slab into small pieces, cooling it, collecting a Charpy test piece from this piece, and testing it. The Charpy test was performed according to JIS Z 2242. The V-notch test piece used was taken from the site where the ingot surface layer was ground by about 2 mm from the width direction of the ingot mold, and the average value of the number of tests 3 was calculated.

  In the present invention, the transition temperature of the continuously cast slab can be lowered to 300 ° C. or less by the above-mentioned component regulation, and it can be inserted into the heating furnace even after 7 hours or more have passed after the slab has been cut. When the transition temperature is 250 ° C., no cracking occurs even after 10 hours after cutting.

  Hereinafter, the present invention will be specifically described based on examples.

  Steel having the chemical composition shown in Table 1 was made into an ingot having a thickness of 30 mm and a width of 100 mm using a vacuum high-frequency melting furnace, and melted to a length of 180 mm to collect the ingot.

  In addition, about each steel of the component shown in Table 1, the transition temperature was calculated | required by taking a sample from the ingot which melt | dissolved beforehand, cooling to normal temperature, and processing the Charpy test piece. The relationship between the ingot cooling time and temperature is shown in FIG. At that time, in order to make the ingot cooling rate close to that of the slab, a thermocouple was installed in the portion where the ingots were overlapped, and the temperature change was observed.

  Each melted ingot is stacked, covered with a heat insulating cover, slowly cooled, and when the first ingot cut first becomes 55 to 115 ° C. higher than the transition temperature, it is inserted into a heating furnace to 1200 ° C. After soaking, hot rolling was performed. On the other hand, as a comparative example, Steel No. When the ingot temperature of No. 1 became 60 ° C. lower than the transition temperature, it was inserted into the heating furnace.

  Table 2 shows the time required from the completion of casting to the end of hot rolling and the surface condition of the hot-rolled steel sheet. The horizontal crack of the ingot shown here indicates the number of cracks that can be confirmed by visually observing the cut surface of the ingot when inserted into a hot-rolling heating furnace.

  The surface condition of the steel sheet after hot rolling was judged by the condition of removal of wrinkles after surface grinding. A grinding of about 40 μm per 10 cm 2 on one side was performed and the finish was # 600. A color check generally used for slab cracking was performed on the part, and the case where there was no crack of 5 mm was determined as good. Cracks remained after grinding, and the parts where large cracks were judged to be impossible to remove were cut and removed into scrap. Moreover, when the ingot was severely embrittled, a large crack was observed before the start of hot rolling or after one or two passes, and it was judged that rolling was impossible, and the scrap was processed.

  As shown in Table 2, since the transition temperature of the ferrite-austenitic stainless steel as a component regulated in the present invention is remarkably low at 300 ° C. or less, even if the time from completion of casting to insertion into the heating furnace is increased, the slab No cracking occurs. However, comparative steel No. 1 and no. When the heating furnace insertion temperature is as low as 160 ° C. or lower as in No. 11, cracks can be observed in the hot-rolled sheet even if the composition conditions are satisfied. Steel No. shown as a reference example. In No. 24, since the DF value was less than 70, no cracks could be observed in the hot-rolled sheet even at 80 ° C. and a furnace insertion temperature close to room temperature.

  Comparative steel No. No. 15 had a small amount of Al and was below the lower limit. Deoxidation was insufficient, coarse oxides were scattered, and the furnace insertion temperature was lower than the ingot transition temperature, so hot rolling occurred frequently. Comparative steel No. In the case of No. 16, N was large and the upper limit was exceeded, voids due to N were generated, and film-like carbonitrides were deposited at the grain boundaries, so hot rolling occurred frequently. Comparative steel No. In No. 17, since Mn deviated from the upper limit, hot workability deteriorated due to high Mn, and wrinkles occurred during hot rolling. Comparative steel No. No. 18 had a heating furnace insertion temperature lower than the transition temperature of the ingot, and because the DF value was out of the upper limit and Al was out of the upper limit, hot rolling was frequently caused by ingot cracking and hardening due to high Al. . Comparative steel No. In No. 19, the DF value exceeded the upper limit, the transition temperature was very high, and even if it was inserted into the heating furnace in a short time of 6 hours after the completion of casting, the transition temperature fell below, so cracking occurred in the ingot. Comparative steel No. In No. 20, Si deviated from the upper limit, and hardening due to Si was remarkable and wrinkles occurred during hot rolling. Comparative steel No. In No. 21, since Ti exceeded the upper limit and the DF value was 85 or more, cracks were observed before inserting the heating furnace, and cracks were also generated in the hot-rolled sheet. Comparative steel No. No. 22 has a heating furnace insertion temperature lower than the transition temperature of the ingot, and C and Ni are outside the upper limit and the DF value is 85 or more. Also cracks occurred. Comparative steel No. In No. 23, Cr, Cu, Mo, and Nb deviated from the upper limit and the DF value deviated from the lower limit, so hot rolling occurred frequently.

  According to the present invention, it is possible to produce a ferritic / austenitic stainless steel sheet by a continuous casting-hot charge method.

  The present invention relates to a ferritic / austenitic stainless steel excellent in ingot crack resistance and a method for producing the same. According to the present invention, ferritic and austenitic stainless steels excellent in workability can be produced without containing a large amount of expensive and rare element Ni, which can contribute to resource protection and environmental conservation. it is conceivable that.

Claims (6)

% By mass
C: 0.10% or less,
Si: 2.0% or less,
Mn: 4.0% or less,
P: 0.050% or less,
S: 0.010% or less,
Cr: 17 to 25%,
Ni: 0.6 to 5.0%,
Cu: 2.0% or less,
Mo: 2.0% or less,
N: 0.01 to 0.15%,
Al: 0.01-0.2%
Ferritic / austenitic stainless steel with excellent crack resistance, characterized in that the balance is made of iron and inevitable impurities, and the DF value represented by the following formula (1) is 70 to 85.
DF value = 7.2 × (Cr + 0.88 × Mo + 0.78 × Si)
−8.9 × (Ni + 0.03 × Mn + 0.72 × Cu + 22 × C + 21 × N) − 44.9 Formula (1) Furthermore, in mass%,
Nb: 0.50% or less,
Ti: 0.50% or less,
The ferritic / austenitic stainless steel with excellent crack resistance according to claim 1, characterized in that it contains one or two of the following. Furthermore, in mass%,
Ca: 0.003% or less,
Mg: 0.003% or less,
B: 0.003% or less,
The ferritic / austenitic stainless steel with excellent crack resistance according to claim 1, wherein the ferritic / austenitic stainless steel is excellent. % By mass
C: 0.10% or less,
Si: 2.0% or less,
Mn: 4.0% or less,
P: 0.050% or less,
S: 0.010% or less,
Cr: 17 to 25%,
Ni: 0.6 to 5.0%,
Cu: 2.0% or less,
Mo: 2.0% or less,
N: 0.01 to 0.15%,
Al: 0.01-0.2%
The balance is made of iron and unavoidable impurities, and the DF value of 70 to 85 represented by the following formula (1) is made into a slab by continuous casting, and continuously below its impact transition temperature. A method for producing a ferritic / austenitic stainless steel sheet having excellent crack resistance, which is characterized by heating without cooling to hot rolling and then hot rolling.
DF value = 7.2 × (Cr + 0.88 × Mo + 0.78 × Si)
−8.9 × (Ni + 0.03 × Mn + 0.72 × Cu + 22 × C + 21 × N) − 44.9 Formula (1) The slab is further mass%,
Nb: 0.50% or less,
Ti: 0.50% or less,
1 or 2 types of these are contained, The manufacturing method of the ferritic-austenitic stainless steel plate excellent in the placement crack resistance of Claim 4 characterized by the above-mentioned. The slab is further mass%,
Ca: 0.003% or less,
Mg: 0.003% or less,
B: 0.003% or less,
One type or two types of these are contained, The manufacturing method of the ferrite austenitic stainless steel plate excellent in the placement cracking resistance in any one of Claim 4 or 5 characterized by the above-mentioned.

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