Alloy sheet for shadow mask and method for manufacturing thereof

Abstract: An alloy sheet for making a shadow mask consists essentially of 34 to 38 wt.% Ni, 0.07 wt.% or less Si, 0.002 wt.% or less B, 0.002 wt.% or less O, less than 0.002 wt.% N and the balance being Fe and inevitable impurities; said alloy sheet after annealing before press-forming having 0.2 % proof stress of 28 kgf/mm² or less; and a gathering degree of {211} plane being 16 % or less. A method for manufacturing an alloy sheet comprises: a finish cold-rolling step of cold-rolling the cold-rolled sheet at a cold-rolling reduction ratio in response to an average austenite grain size D (µm), the reduction ratio of final cold-rolling R (%) satisfying the equations below; 16 ≦ R≦75, 6.38D-133.9 ≦ R ≦ 6.38D-51.0 a softening annealing step of annealing said cold rolled sheet in a temperature range of 720 to 790 °C for 2 to 40 min. before press-forming and on conditions satisfying the equation below; T ≧ -53.8 logt + 806, where T( °C) is the temperature and t (min.) is the time of the annealing.

Description: Background of the Invention Field of the Invention The present invention relates to an alloy sheet for making a shadow mask having high press-formability and a method of manufacturing the same. Description of the Related Art A recent trend of up-grading color television to high definition TV has employed Fe-Ni alloy containing 34 to 38wt.% Ni as the alloy for making a shadow mask to suppress color-phase shift. Compared with low carbon steel which has long been used as a shadow mask material, conventional Fe-Ni alloy has a considerably lower thermal expansion coefficient. Accordingly, a shadow mask made of conventional Fe-Ni alloy raises no problem of color-phase shift coming from the thermal expansion of the shadow mask even when an electron beam heats the shadow mask. Common practice in making alloy sheets for shadow masks includes the following steps. An alloy ingot is prepared by a continuous casting process or ingot-making process. The alloy ingot is subjected to slabbing, hot-rolling, cold-rolling, and annealing to form an alloy sheet. The alloy sheet for the shadow mask is then usually processed in the following steps to form a shadow mask. (1) The alloy sheet is photo-etched to form passage-holes for the electron beam on the alloy sheet for the shadow mask. A thin alloy sheet for a shadow mask which has been perforated by etching is hereinafter referred to as a "flat mask". (2) The flat mask is subjected to annealing. (3) The annealed flat mask is pressed into the curved shape of a cathode ray tube. (4) The press-formed flat mask is assembled to form a shadow mask, which is then subjected to blackening treatment. A shadow mask which is prepared by cold-rolling, recrystallization annealing, or by further slight finishing rolling after recrystallization annealing, has greater strength than conventional low carbon steel. Accordingly, such a conventional Fe-Ni alloy is subjected to softening-annealing (annealing before press-forming) at a temperature of 800°C or more before press-forming to make the grains of which it is composed coarse. After the softening-annealing, a warm-press is applied to carry out spheroidal forming. A temperature of 800°C or more is, however, in the high temperature region. Therefore, from the viewpoint of work efficiency and economy, the development of a manufacturing method to obtain as low a strength as in a material which has been softening-annealed at 800°C or more, by softening-annealing at 800°C or less has been a waited. Responding to this desire, a prior art proposal was made in JP-A-H3-267320 (the term JP-A- referred to herein signifies an unexamined Japanese patent publication ). This prior art employs cold-rolling, recrystallization annealing, finish cold-rolling and softening annealing. The finish cold-rolling is conducted at a reduction ratio of 5 to 20%. The temperature of the softening annealing is below 800°C, more specifically at 730°C for 60 min. This prior art produces a sheet having sufficiently low strength to give good press-forming performance with a 0.2% proof stress of 9.5 kgf/mm 2 (10 kgf/mm 2 or less) at 200°C. However, the prior art does not achieve the quality required to perform satisfactory warm press-forming. Shadow masks prepared by the prior art were found to gall the die and to exhibit cracks generated at the edge of the shadow masks. Nevertheless, cathode ray tube manufacturers try to carry out softening annealing at a lower temperature and in a shorter time than the conventional levels described above, aiming to improve work efficiency and economy. The target annealing time is 40min. or less, and in some cases, as short as 2 min. However, if such annealing conditions are applied to the prior art, the galling of dies during press-forming becomes severe and cracks on shadow masks increase to raise a serious quality problem. Summary of the Invention The object of the present invention is to provide an alloy sheet for making a shadow mask having high press-formability and a method of manufacturing the same. To achieve this object, the present invention provides an alloy sheet for making a shadow mask consisting of 34 to 38 wt.% of Ni, 0.001-0.07 wt.% of Si, 0.002 wt.% or less of B, 0.002 wt.% or less of O, 0.0001-0.002 wt.% of N, 0-1 wt.% of Co, optionally 0.0001-0.005 wt.% of C, optionally 0.001-0.35 wt.% of Mn, optionally 0.001-0.05 wt.% of Cr, and a balance of Fe and inevitable impurities; said alloy sheet after annealing before press-forming having 0.2% proof stress of 28 kgf/mm 2 or less; and a gathering degree of {211} plane on a surface of said alloy sheet being 16% or less. The present invention also provides an alloy sheet for making a shadow mask consisting of 28 to 38 wt.% of Ni, 0.001-0.07 wt.% of Si, 0.002 wt.% or less of B, 0.002 wt.% or less of O, 0.0001-0.002 wt.% of N, over 1 to 7 wt.% of Co, optionally 0.0001-0.005 wt.% of C, optionally 0.001-0.35 wt.% of Mn, optionally 0.001-0.05 wt.% of Cr, and a balance of Fe and inevitable impurities; said alloy sheet after annealing before press-forming having 0.2% proof stress of 28 kgf/mm 2 or less; and a gathering degree of {211} plane on a surface of said alloy sheet being 16% or less. The present invention also provides a method for manufacturing an alloy sheet for a shadow mask comprising the steps of: (a) preparing a hot rolled-sheet containing Fe, Ni and optionally Co; (b) annealing said hot-rolled sheet in a temperature range of 910 to 990°C; (c) a first cold-rolling step of cold-rolling said annealed hot-rolled sheet to produce a cold-rolled sheet; (d) a first crystallization annealing step of annealing said cold-rolled sheet subjected to the first cold-rolling; (e) a second cold-rolling step of cold-rolling said cold-rolled sheet subjected to the recrystallization annealing; (f) a final recrystallization annealing step of annealing said cold-rolled sheet subjected to the second cold-rolling; (g) a finish cold-rolling step of cold-rolling of the cold-rolled sheet subjected to the finish recrystallization annealing at a cold-rolling reduction ratio in response to an average austenite grain size D (µm)yielded by the finishing recrystallization annealing, the reduction ratio of final cold-rolling R (%) satisfying the equations below; 16≤R≤75, 6.38D-133.9≤R≤6.38D-51.0 (h) a softening annealing step of annealing said cold-rolled sheet subjected to the finishing cold-rolling in a temperature range of 720 to 790°C for 2 to 40 min. before press-forming and on conditions satisfying the equation below; T≥-53.8 logt + 806, where T(°C) is the temperature and t(min.) is the time of the annealing. The term "favorable press-formability" of the present invention means having excellent shape freezing performance, having a good fit with dies (free of galling of dies), and generating no cracks in materials during press-forming. Brief Description of the Drawings Fig. 1 is a graph showing the relation between 0.2% proof stress after annealing before press-forming, and the gathering degree of {211} planes and crack generation during press-forming according to preferred embodiment-1; Fig. 2 is a graph showing the relation between the gathering degree of {211} planes, elongation perpendicular to rolling direction, and annealing temperature of hot-rolled sheet according to preferred embodiment-1; Fig. 3 is a graph showing the relation between average austenite grain size before finish cold-rolling, and finish cold-rolling reduction ratio and 0.2% proof stress after annealing before press-forming according to preferred embodiment-1; Fig. 4 is a graph showing the relation between the conditions for annealing before press-forming, 0.2% proof stress after annealing before press-forming and the gathering degree of {211} planes according to preferred embodiment-1; Fig. 5 is a graph showing the relation between the conditions for annealing before press-forming, 0.2% proof stress after annealing before press-forming and the gathering degree of {211} planes according to preferred embodiment-1. Description of the Preferred Embodiment Preferred embodiment - 1 The present invention asks for a specific range of yield strengths in order to improve shape fixability during hot press-forming and to suppress crack generation in alloy sheet. Yield strength is represented by 0.2% proof stress of 28.0 kgf/mm 2 at room temperature after softening annealing before press-forming (hereinafter referred to as "annealing before press-forming"). 0.2% proof stress of 28.0 kgf/mm 2 or less further improves the shape fixability. The gist of the present invention is as follows. (a), Growth of crystal grains is enhanced during annealing before press-forming by specifying the content of B and O. Coarsening crystal grains realizes a low yield strength. (b), Suitability to dies during press-forming is improved by specifying the content of Si and N to suppress galling of dies. (c), Generation of cracks during press-forming is suppressed by controlling the degree of {211} planes on the thin alloy sheet after annealing before press-forming. The invention is described in greater detail in the following with reasons for limiting the ranges of the chemical composition of the alloy. To prevent color-phase shift, Fe-Ni alloy sheet for shadow masks has to have an upper limit to average thermal expansion coefficient of approximately 2.0 x 10 -6 / °C in the temperature range of 30 to 100°C. The average thermal expansion coefficient depends on the content of Ni in the alloy sheet. The Ni content which satisfies the above limitation of average thermal expansion coefficient is in a range of 34 to 38wt.%. Consequently, the preferred Ni content is in a range of 34 to 38wt.%. More preferably, the Ni content which further decreases average thermal expansion coefficient is in a range of 35 to 37wt.%, and most preferably in a range of 35.5 to 36.5 wt.%. Usually Fe-Ni alloy includes Co as one of the inevitable impurities. Co of 1 wt.% or less does not affect the characteristics. Ni content which satisfies the above described range is also employed. On the contrary, when over 1 wt.% to 7 wt.% Co is included, the Ni content which satisfies the above limitation of average thermal expansion coefficient is in a range of 28 to 38 wt.%. Consequently, the Ni content is specified as 28 to 38 wt.% when over 1 wt.% to 7 wt.% Co is included. Co and Ni content to further improve the characteristics is in a range of 3 to 6 and 30 to 33 wt.%, respectively. As Co of over 7 wt.% increases the thermal expansion coefficient, the upper limit of Co content is defined as 7 wt.%. Oxygen is one of the inevitable impurities. When oxygen content is increased, non-metallic oxide inclusion increases in the alloy. Non-metallic inclusion suppresses the growth of crystal grains during annealing before press-forming, particularly under conditions of 720 to 790°C and 40min or less annealing time, which are the conditions before press-forming specified in this invention. If the content of O exceeds 0.002%, the growth of crystal grains is suppressed and 0.2% proof stress after annealing before press-forming exceeds 28.0 kgf/mm 2 . The lower limit of O content is not specially limited, but it is selected to be 0.001% from the economy of ingot-making processes. Boron enhances the hot-workability of the alloy. An excess amount of B induces the segregation of B at boundaries of recrystallized grains formed during annealing before press-forming, which inhibits the free migration of grain boundaries and results in the suppression of grain growth and the 0.2% proof stress after annealing before press-forming limit to be exceeded. In particular, under the annealing conditions before press-forming specified in this invention, the suppression of grain growth is strong and the does not uniformly affect all grains, so a severely mixed grain structure is accompanied by irregular elongation of material during press-forming. Boron also increases the gathering degree of {211} planes after annealing, which causes cracks on the skirt of the material. Boron content above 0.0020wt.% significantly enhances the suppression of grain growth, and the 0.2% proof stress exceeds 28.0 kgf/mm 2 . Also irregular elongation during press-forming appears, and the degree of {211} planes exceeds the upper limit specified in this invention. Based on these findings, the upper limit of B content is defined as 0.0020wt.%. Silicon is used as the deoxidizer during ingot-making of the alloy. When the Si content exceeds 0.07wt.%, an oxide film of Si is formed on the surface of the alloy during annealing before press-forming. The oxide film degrades the fit between die and alloy sheet during press-forming and results in the galling of the die by the alloy sheet. Consequently, the upper limit of Si content is specified as 0.07wt.%. Less Si content improves the fit of die and alloy sheet. The lower practical limit of Si content is 0.001wt.% or more from the economy of ingot-making processes. Nitrogen is an element unavoidably entering into the alloy during ingot-making processes. 0.0020 wt.% or more of nitrogen induces the concentration of N on the surface of the alloy during annealing before press-forming. The concentrated N on the surface of the alloy degrades the fit of the die and alloy sheet to gall the die with the alloy sheet. Consequently, N content is specified to be below 0.0020wt.%. The lower practical limit of N content is 0.0001wt.% or higher from the economy of ingot-making processes. Most preferably, the composition further contains 0.0001 to 0.005 wt.% C, 0.001 to 0.35wt.%Mn, and 0.001 to 0.05wt.% Cr. As described above, the control of alloy composition and of 0.2% proof stress after annealing before press-forming specified in this invention suppresses the galling of dies by alloy sheet during press-forming and gives a superior shape fixability. However, regarding press-forming quality, there remains the problem of crack generation in press-formed materials. To cope with this problem, the inventors studied the relation between crack generation in the material during press-forming and crystal orientation during press-forming by changing the crystal orientation of the alloy sheet in various directions using alloy sheets having chemical composition and 0.2% proof stress in the range specified in this invention, and found that effective conditions to suppress crack generation in the alloy material are to control the gathering degree of {211} planes to be maintained at or below a specified value, as well as to control the 0.2% proof stress after annealing before press-forming to keep it at or below a specified level. Fig. 1 shows the relation between crack generation on alloy sheet during press-forming, the gathering degree of {211} planes, and 0.2% proof stress for an alloy sheet having chemical composition specified in the present invention. The gathering degree of {211} planes is determined from the relative X-ray intensity ratio of (422) diffraction planes of alloy sheet after annealing before press-forming divided by the sum of the relative X-ray diffraction intensity ratios of (111), (200), (220), (311), (331), and (420) diffraction planes. The relative X-ray diffraction intensity ratio is defined as the value of X-ray diffraction intensity observed on each diffraction plane divided by the theoretical X-ray diffraction intensity of that diffraction plane. For example, the relative X-ray diffraction intensity ratio of the (111) diffraction plane is determined from the X-ray diffraction intensity of the (111) diffraction plane divided by the theoretical X-ray diffraction intensity of the (111) diffraction plane. The measurement of the degree of {211} planes was carried by measuring the X-ray diffraction intensity of (422) diffraction planes which have equivalent orientation to {211} planes. Fig. 1 clearly shows that the case where 0.2% proof stress does not exceed 28.0 kgf/mm 2 and where the gathering degree of {211} planes does not exceed 16% does not induce crack generation in alloy sheet during press-forming, which fact indicates the effect of this invention. Based on this finding, the invention specifies 16% or less for the gathering degree of {211} planes as the condition to suppress crack generation in the alloy sheet. The alloy sheet of the present invention is manufactured by the following processes. A hot-rolled alloy sheet having the above described chemical composition is annealed, subjected to a process including cold-rolling, recrystallization annealing and cold-rolling, followed by final recrystallization annealing, finish cold-rolling and annealing before press-forming. The processes will be described in detail. The hot-rolled sheet has to be annealed in the specified temperature range to maintain the gathering degree of {211} planes at 16% or less. A hot-rolled sheet which satisfies the conditions of chemical component specified in the present invention is annealed at different temperatures, subjected to a process including cold-rolling, recrystallization annealing, cold-rolling, recrystallization annealing (at 890°C for 1 min.), finish cold-rolling (at 21 % of reduction ratio) and annealing before press-forming to obtain a desired alloy sheet. As a comparative example, a hot-rolled strip which had not been annealed was treated under the same conditions as above. Fig. 2 shows the relation between the gathering degree of {211} planes, elongation perpendicular to rolling direction, and annealing temperature of alloy sheet treated by the processes above. According to Fig. 2, the gathering degree of {211} planes was 16% or less when the annealing temperature of the hot-rolled sheet was 910 to 990°C. Consequently, this invention specifies a temperature for annealing hot-rolled sheet in the range of 910 to 990 °C to assure a gathering degree of {211} planes of 16% or less. To achieve the satisfactory gathering degree of {211} planes being focused on in this invention, uniform heat treatment of the slab after slabbing is not preferable. For example, when a uniform heat treatment is carried at 1200°C or more for 10 hours or more, the gathering degree of {211} planes exceeds the range specified in the present invention. Therefore, such heat treatment must be avoided. The mechanism of crack generation during press-forming under conditions above 16% of the degree of {211} crystal planes is not clear. Fig. 2 shows the trend that a high degree of {211} planes gives a low elongation perpendicular to the rolling direction. Increased degree of {211} planes decreases the elongation perpendicular to the rolling direction and lowers the fracture limit, then presumably induces cracks. To keep the gathering degree of {211} planes at 16% or less and to maintain the 0.2% proof stress after annealing before press-forming at 28.0 kgf/mm 2 or less, the control of the conditions for finish cold rolling (reduction ratio of finish cold-rolling), and of the conditions for annealing before press-forming are also important. Hot-rolled alloy strips having the composition above were subjected to annealing (in the temperature range of 910 to 990°C), cold-rolling, recrystallization annealing, finish cold-rolling, and annealing before press-forming (at 750°C for 15min.) to produce alloy sheets. The alloy sheets were tested for tensile strength to determine 0.2% proof stress (the values are shown in parentheses in Fig. 3). Fig. 3 shows the relation between the 0.2% proof stress, reduction ratio of finish cold-rolling and average austenite grain size before finish cold-rolling. In this test, the specified austenite grain size was obtained by varying the temperature of recrystallization annealing before finish cold-rolling. A 0.2% proof stress of 28.0 kgf/mm 2 or less was obtained as is shown in region I of Fig. 3 under the conditions given below. Finish cold-rolling reduction ratio (R%): 16 - 75%, 6.38D - 133.9 ≤ R ≤ 6.38D - 51.0, where D is the average austenite grain size (µm) before finish cold-rolling. The reduction ratio (R%) is controlled based on the average grain size (D µm). In the case of R < 16% or R < 6.38D - 133.9, the conditions specified in the present invention for annealing before press-forming give insufficient recrystallization, insufficient growth of recrystallized grain, and 0.2% proof stress exceeding 28.0 kgf/mm 2 , and result in an unsatisfactory alloy sheet. If R > 75% or R > 6.38D - 51.0, then the conditions specified in the present invention for annealing before press-forming allow 100% recrystallization but give an excess frequency of nucleation during recrystallization, which decreases the size of the recrystallized grains. In that case, the 0.2% proof stress exceeds 28.0 kgf/mm 2 , and the alloy sheet has unsatisfactory qualities. For the above described reasons, the conditions which achieve 28.0 kgf/mm 2 or below of 0.2% proof stress under the conditions for annealing before press-forming in this invention are specified such that R (%), the reduction ratio of cold-rolling, satisfies equations (1a) and (1b) described below according to the average austenite grain size before finish cold-rolling. 16 ≤ R ≤ 75 6.38D - 133.9 ≤ R ≤ 6.38D - 51.0 An adequate value for the reduction ratio of finish cold-rolling (R%) in response to the austenite grain size (D µm) before finish cold-rolling within the range specified above realizes a gathering degree of {211} planes of 16% or less on the surface of alloy sheet after annealing before press-forming. The structure control of the alloy sheet of the present invention is realized by controlling the frequency of nucleation during recrystallization, through the control of the overall structure of the alloy during hot-rolled sheet annealing, and an adequate reduction ratio of finish cold-rolling in response to the grain size before finish cold-rolling. Fig. 3 shows that further reduction of 0.2% proof stress after annealing before press-forming is achieved by optimizing the reduction ratio of finish cold-rolling (R%). In concrete terms, by controlling the value of the reduction ratio of finish cold-rolling to satisfy equations (2a) and (2b), that is, so that the value is in region II in Fig. 3, the 0.2% proof stress can be 27.5 kgf/mm 2 or less. 21 ≤ R ≤ 70 6.38D - 122.6 ≤ R ≤ 6.38D - 65.2 Furthermore, by controlling the value of the reduction ratio to satisfy equations (3a) and (3b), that is, so that the value is in region III, the 0.2% proof stress can be 27 kgf/mm 2 or less. 26 ≤ R ≤ 63 6.38D - 108.0 ≤ R ≤ 6.38D - 79.3 For the above described reasons, the present invention specifies the reduction ratio of finish cold-rolling R(%) to satisfy equations (2a) and (2b) above, in response to the average austenite grain size D (µm) before finish cold-rolling to obtain 0.2% proof stress of 27.5 kgf/mm 2 or less, and specifies the reduction ratio of finish cold-rolling R(%) to satisfy equations (3a) and (3b) above, in response to the average austenite grain size D (µm) before finish cold-rolling to obtain 0.2% proof stress of 27.0 kgf/mm 2 or less. The average austenite grain size specified by the relation to reduction ratio of finish cold-rolling, R, is obtained by annealing a hot-rolled sheet followed by cold-rolling- and annealing in a temperature range of 860 to 950°C for 0.5 to 2 min. Fig. 4 shows the relation between annealing temperature before press-forming (T), annealing time (t), 0.2% proof stress after annealing before press-forming and gathering degree of {211} planes of an alloy sheet. The alloy sheet was manufactured by a process including annealing of hot-rolled sheet in a temperature of 910 to 990°C, cold-rolling, recrystallization annealing, cold-rolling, recrystallization annealing, finish cold-rolling and annealing before press-forming and by controlling the conditions such as composition, annealing condition of the hot-rolled sheet and reduction ratio of finish cold-rolling in response to the average austenite grain size before finish cold-rolling to satisfy the specification of the present invention. As clearly shown in Fig. 4, even if the annealing condition of the hot-rolled sheet, austenite grain size before finish cold-rolling, and the finish cold-rolling reduction ratio stay within the range specified in this invention, when the temperature of annealing before press-forming has the relation of T < -53.8 log t + 806, then satisfactory recrystallization is not conducted and 0.2% proof stress exceeds 28.0 kgf/mm 2 and the gathering degree of {211} planes exceeds 16%, which characteristic values do not satisfy the ranges specified in this invention. When the temperature (T) of annealing before press-forming, exceeds 790°C or when annealing time (t) before press-forming exceeds 40min., then the {211} planes develop to increase the gathering degree of {211} planes to be higher than 16%, which is also inadequate. Consequently, to obtain a value of 0.2% proof stress and degree of {211} planes specified in this invention, this invention specifies the temperature (T) of annealing before press-forming to be 790°C or less, and the annealing time (t) before press-forming to be 40min. or less and T ≥ -53.8 log t + 806. Fig. 5 shows the relation between the 0.2% proof stress in response to the time of annealing before press-forming and the change of gathering degree of {211} planes for each annealing temperature. The employed alloys were No. 1 alloy of the present invention and alloys Nos. 21 and 22, which are comparative alloys. They were hot-rolled to manufacture the hot-rolled sheet, then subjected to a process of annealing in a temperature range of 910 to 990°C, cold-rolling, recrystallization annealing, cold-rolling, recrystallization annealing, finish cold-rolling and annealing before press-forming. In both cases, the conditions for annealing hot-rolled sheet, and the reduction ratio of finish cold-rolling in response to the average austenite grain size before finish cold-rolling remained within the ranges specified in this invention. According to Fig. 5, within the conditions for annealing before press-forming specified in this invention, the alloy of this invention gives both 0.2% proof stress and gathering degree of {211} planes specified in this invention. The comparative alloys clearly have problems in their press-formability with 0.2% proof stress exceeding 28.0 kgf/mm 2 even if annealed at 750°C, and with the gathering degree of {211} planes exceeding the limit specified in the present invention. Accordingly, the present invention emphasizes the alloy composition as well as the specification of manufacturing method. The annealing before press-forming of this invention may be carried before photo-etching. In that case, if the conditions for annealing before press-forming are kept within the ranges specified in this invention, then satisfactory photo-etching quality is secured. As for the alloy of the prior art, annealing before press-forming cannot be conducted before photo-etching because photo-etching after annealing before press-forming following the conditions of this invention results in poor quality photo-etching. On the contrary, the alloy of this invention having specified composition and gathering degree of {211} planes keeps its favorable quality if photo-etching after annealing before press-forming is conducted. There are other methods to limit the degree of {211} planes on the alloy sheet after annealing before press-forming within the ranges specified in this invention. Examples of these methods are rapid solidification and overall texture control through the control of recrystallization during hot-working. Example 1 This is a series of ladle refining produced alloys No. 1 through No. 23 having the compositions shown in Table 1 and Table 2. Alloys No. 1 through No. 13 and No. 18 through No. 23 were cast into ingots. These ingots were subjected to adjusting, blooming, scarfing and hot-rolling (at 1100°C for 3 hrs) to provide hot-rolled sheet. Alloys No. 14 through No. 17 were directly cast into thin plates, these plates were hot-rolled at a reduction ratio of 40%, then rolled at 700°C to provide a hot-rolled sheet. These hot-rolled sheets were subjected to annealing (at 930°C), cold-rolling, recrystallization annealing, cold-rolling, recrystallization annealing (following the conditions shown in Table 5) and finish cold-rolling (at a reduction ratio of 21%) to provide alloy sheets having a thickness of 0.25 mm. The hot-rolled sheets were fully recrystallized by hot-rolling. The alloy sheets were etched to make flat masks, which flat masks were then treated by annealing before press-forming at 750°C for 20 min. to provide materials No. 1 through No. 23. These were press-formed to inspect the press-formability. Table 1 and Table 2 shows the average austenite grain size before finish cold-rolling of each material, and Table 3 and Table 4 shows the gathering degree of {211} planes, tensile properties and press-formability. The tensile properties (0.2% proof stress and elongation perpendicular to the rolling direction) and gathering degree of {211} planes were inspected after annealing before press-forming. The tensile properties were determined at room temperature. The measurement of the gathering degree of {211} planes was carried out with the X-ray diffraction method described before. As shown in Table 3 and Table 4, materials No. 1 through No. 13, which have chemical compositions, gathering degrees of {211} planes, and 0.2% proof stresses within the ranges specified in the present invention, show excellent press-formability. Materials No. 1 through No. 17 of the present invention that include Co also show excellent press-formability. On the contrary, materials No. 18 through No. 20 give Si and Ni contents above the upper limit of this invention and raise a problem in fit with die. Material No. 19 gives an O content above the upper limit of this invention and also gives 0.2% proof stress above the upper limit, 28.9 kgf/mm 2 , which results in a poor shape fixability and induces crack generation. Material No. 21 and No. 22 are comparative examples giving B content and B and O contents above the upper limits of this invention, respectively, both give 0.2% proof stress above the upper limit of this invention, 28.0 kgf/ mm 2 , to degrade the shape fixability. These comparative materials give gathering degrees of {211} planes above the upper limit of the present invention to induce cracking of alloy sheet. The average austenite grain size before finish cold-rolling of material No. 23 fails to reach the level that satisfies the reduction ratio of finish cold-rolling, which gives a 0.2% proof stress of more than 28.0 kgf/ mm 2 to degrade shape fixability and induce crack generation. The above discussion clearly shows that Fe-Ni alloy sheet and Fe-Ni-Co alloy having the high press-formability aimed for in this invention is prepared by adjusting the chemical composition, degree of (211) planes, and 0.2% proof stress within the ranges specified in this invention. Material No. Annealing conditions 1 890°C x 1 min. 2 890°C x 1 min. 3 890°C x 1 min. 4 880°C x 0.8 min. 5 880°C x 0.8 min. 6 880°C x 0.8 min. 7 880°C x 0.8 min. 8 870°C x 1 min. 9 870°C x 1 min. 10 870°C x 1 min. 11 910°C x 1 min. 12 920°C x 0.5 min. 13 930°C x 0.5 min. 14 920°C x 0.5 min. 15 870°C x 1 min. 16 880°C x 0.8 min. 17 870°C x 1 min. 18 890°C x 1 min. 19 890°C x 1 min. 20 890°C x 1 min. 21 890°C x 1 min. 22 890°C x 1 min. 23 850°C x 1 min. Example 2 Hot-rolled sheets of alloy Nos. 1, 9 and 14, which were used in Example 1, were employed. Annealing for hot-rolled sheet was applied to these materials under various annealing conditions given in Table 6, and no annealing was applied to one material, which is also given in the table. They were subjected to cold-rolling, recrystallization annealing, cold rolling, recrystallization annealing (at 890°C for 1 min.), finish cold-rolling (at a reduction ratio of 21%) to provide alloy sheet having a thickness of 0.25 mm. The flat masks were then treated by annealing before press-forming at 750°C for 15 min. to give materials No. 24 through No. 28. The flat masks were press-formed and were tested for press-formability. Table 6 shows the annealing temperature, average austenite grain size before finish cold-rolling and gathering degree of {211} planes. Table 7 shows tensile properties and press-formability. The methods for measuring properties were the same as in Example 1. As shown in Table 6 and 7, materials No. 24 and No. 25 having a chemical composition and satisfying the conditions specified in the present invention have excellent press-formability. On the contrary, materials No.26 through No. 28 give a hot-rolled sheet annealing temperature above the limit of this invention, and all of these materials give the gathering degree of {211} planes above the upper limit of this invention and generate cracks in the alloy sheet during press-forming. Furthermore, material No. 28 gives 0.2% proof stress of more than 28.0 kgf/mm 2 and raises the problem of shape fixability during press-forming. Consequently, to keep the degree of {211} planes within the range specified in this invention, it is important to carry out the hot-rolled sheet annealing following the conditions specified in this invention. Material No. Alloy No. Hot-rolled sheet annealing temperature (°C) Average austenite grain size before finish cold-rolling (µm) Gathering degree of {211} planes 24 14 930 18 8 25 9 960 18 7 26 1 900 17 31 27 1 1000 18 35 28 1 - 17 38 Material No. Tensile properties Press-formability 0.2% Proof stress (kgf/mm 2 ) Elongation perpendicular to the rolling direction (%) Shape fixability Fit with die Cracking in the alloy sheet 24 27.7 43.3 O ○ ○ None 25 27.4 43.2 O ○ ○ None 26 27.9 38.5 ○ ○ Yes 27 28.0 39.0 ○ ○ Yes 28 28.2 36.2 ▵ ○ Yes Example 3 Hot-rolled sheets of alloy Nos. 1, 2, 4, 6, 7, 8, 9, 11, 12, 13 and 14 which were used in Example 1 were employed. These hot-rolled sheets were subjected to a process including annealing (at 930°C), cold-rolling, recrystallization annealing, cold-rolling, recrystallization annealing (at the temperature shown in Table 8 and Table 9 for 1 min.), finish cold-rolling to obtain alloy sheets having a thickness of 0.25mm. The alloy sheets were etched to make flat masks, which flat masks were then subjected to annealing before press-forming at 750°C for 20 min. to obtain materials No. 29 through No. 66. These materials were press-formed to determine the press-formability. Table 8 and Table 9 show the annealing temperature before finish cold-rolling, average austenite grain size before finish cold-rolling, reduction ratio of finish cold rolling and tensile properties. Table 10 and Table 11 show the gathering degree of {211} planes and press-formability. The methods for measuring properties were the same as in Example 1. Table 8 through Table 11 show that materials No. 30 through No. 35, No. 38, No. 41 through 43 and No. 47 through 66, which have chemical compositions and satisfy the conditions of hot-rolled sheet annealing and annealing before press-forming specified in the present invention and give the relation between average austenite grain size before finish cold-rolling and reduction ratio of finish cold-rolling in a region specified in the present invention, give 16% or less of {211} planes. Of these, materials No. 5 30, No. 35, No. 38, No. 41, No. 47, No. 49, No. 50, No. 54, No. 60, No. 63 and No. 66 employed reduction ratios of finish cold-rolling, R, (in Region I in Fig. 3) satisfying the above described equations (1a) and (1b) to give 0.2% proof stress of 28.0 kgf/mm 2 or less. Materials No. 31, No. 33, No. 34, No. 43, No. 48, No. 52, No. 55, No. 59 and No. 65 employed reduction ratios of finish cold-rolling, R, (in Region II in Fig. 3) satisfying the above described equations (2a) and (2b) to give 0.2% proof stress of 27.5 kgf/ mm 2 or less. Materials No. 32, No. 42, No. 51, No. 53, No. 56, No. 57, No. 58, No. 61, No. 62 and No. 64 employed reduction ratios of finish cold-rolling, R, (in Region III in Fig. 3) satisfying the above described equations (3a) and (3b) to give 0.2% proof stress of 27.0 kgf/mm 2 or less. All of these materials give the 0.2% proof stress aimed for in this invention and show high press-forming quality. Accordingly, the decrease in 0.2% proof stress proved to improve the shape fixability. Contrary to the above preferred embodiment, the relation among the average austenite grain size before finish cold-rolling, conditions of hot-rolled sheet annealing and reduction ratio of finish cold-rolling of comparative materials No. 29, No. 36, No. 37, No. 39, No. 40, No. 44, and No. 45 failed to satisfy the conditions specified in the present invention even if they satisfied the conditions of chemical composition, hot-rolled sheet annealing and annealing before press-forming specified in the present invention. They are out of the scope of this invention for one of the 0.2% proof stress and the gathering degree of {211} planes or both, and they raise problems with at least one of the shape fixability and crack generation in alloy sheet during press-forming or both. Material No. 46 was treated by annealing before finish cold-rolling at 850°C for 1 min. Such an annealing condition gives an austenite grain size of 10.0 µm, so the 0.2% proof stress exceeds 28.0 kgf/mm 2 even if the reduction ratio of finish cold-rolling is selected to be 15%. These figures cannot provide a shape fixability during press-forming to satisfy the specifications of this invention. As discussed in detail above, though the conditions that the chemical composition, conditions for hot-rolled sheet annealing, and conditions for annealing before press-forming are kept in the ranges specified in this invention, it is important to keep the austenite grain size before finish cold-rolling and the reduction ratio of finish cold-rolling within the ranges specified in this invention to obtain the satisfactory press-formability aimed for by this invention. Material No. Alloy No. Gathering degree of {211} planes (%) Press formability Shape fixability Fit with die Cracking in the alloy sheet 29 1 15 X ○ Yes 30 1 15 ○ ○ None 31 1 8 O ○ ○ None 32 1 14 O ○ ○ None 33 1 16 O ○ ○ None 34 1 12 O ○ ○ None 35 1 5 ○ ○ None 36 1 12 X ○ Yes 37 2 14 ▵ ○ Yes 38 1 15 ○ ○ None 39 1 7 X ○ Yes 40 2 20 X ○ Yes 41 1 8 ○ ○ None 42 1 15 O ○ ○ None 43 1 5 O ○ ○ None 44 1 8 X ○ Yes 45 1 26 X ○ Yes 46 8 20 X ○ Yes 47 2 13 ○ ○ None Material No. Alloy No. Gathering degree of {211} planes (%) Press formability Shape fixability Fit with die Cracking in the alloy sheet 48 6 13 O ○ ○ None 49 6 11 ○ ○ None 50 6 5 ○ ○ None 51 1 3 O ○ ○ None 52 1 2 O ○ ○ None 53 1 15 O ○ ○ None 54 12 19 ○ ○ None 55 14 8 O ○ ○ None 56 9 9 O ○ ○ None 57 11 11 O ○ ○ None 58 11 13 O ○ ○ None 59 11 16 O ○ ○ None 60 9 6 ○ ○ None 61 9 13 O ○ ○ None 62 9 15 O ○ ○ None 63 13 13 ○ ○ None 64 13 16 O ○ ○ None 65 7 15 O ○ ○ None 66 4 15 ○ ○ None Example Hot-rolled sheets of alloy Nos. 1, 4, 9, 10, 12, 14, 21 and 22 which were used in Example 1 were employed. These hot-rolled sheets were subjected to a process including annealing (at 930°C), cold-rolling, recrystallization annealing, cold-rolling, recrystallization annealing (at 890°C for 1 min.), finish cold-rolling (at a reduction ratio of 21%) to obtain alloy sheets having a thickness of 0.25 mm. The alloy sheets were etched to make flat masks, which flat masks were then subjected to annealing before press-forming under the conditions shown in Table 12 to obtain materials No. 67 through No. 84. These materials were press-formed to determine their press-formability. Table 12 shows average austenite grain size before finish cold-rolling, conditions for annealing before press-forming, gathering degree of {211} planes, tensile properties and press-formability. Table 10 and Table 11 show the gathering degree of {211} planes and press-formability. The methods used for measuring properties were the same as in Example 1. Table 12 shows that materials No. 67, No. 69, No. 70 and No. 76 through No. 84, which satisfy the conditions of chemical composition and hot-rolled sheet annealing, finish cold-rolling (reduction ratio of finish cold rolling), annealing before press-forming (temperature, time) specified in the present invention give a gathering degree of {211} planes of 16% or less. All of these materials give the 0.2% proof stress aimed for in this invention and show high press-forming quality. Contrary to the above preferred embodiment, comparative materials No. 72 and No. 73 were annealed before press-forming at a temperature and for a time above the upper limits of the present invention though they satisfied the conditions of chemical composition, hot-rolled sheet annealing and finish cold-rolling (reduction ratio of finish cold-rolling) specified in the present invention. They gave a gathering degree of {211} planes of 16% or more and cracking was generated. Comparative material No. 63 was annealed before press-forming at a temperature (T) and for a time (t) not satisfying the equation T ≥-53.8 log t + 806. Comparative material No. 71 was annealed before press-forming for a time above the upper limit of the present invention and annealing temperature T and annealing time t not satisfying the above described equation. All of these comparative materials gave 0.2% proof stress of more than 28.0 kgf/mm 2 , and they had problems with shape fixability during press-forming. The degree of {211} planes of these materials exceeded 16%, and cracks were generated in the alloy sheets. Materials No. 74 and No. 75 employed comparative alloys. Even if annealing before press-forming was carried out at 750°C for 60 min., their 0.2% proof stress values exceeded 28.0 kgf/mm 2 and they had problems with shape fixability during press-forming. The gathering degree of {211} planes of these materials exceeded 16%, and cracks were generated in the alloy sheets. As described in detail above, though the condition that the chemical composition, conditions for hot-rolled sheet annealing and reduction ratio of finish cold-rolling are kept in the ranges specified in this invention, it is important to keep the conditions for annealing before press-forming within the ranges specified in this invention to obtain the satisfactory press-form quality aimed for by this invention. Example 5 Hot-rolled sheets of alloy No. 1 and No. 4, which were used in Example 1, were employed. These sheets were subjected to annealing (at 930°C), cold-rolling, recrystallization annealing, cold rolling, recrystallization annealing (at 890°C for 1 min.), and finish cold-rolling (at a reduction ratio of 21%) to obtain alloy sheets having a thickness of 0.25 mm. These alloy sheets were annealed before press-forming under the conditions shown in Table 13 to obtain materials No. 85 through No. 87. The alloy sheets were etched to make flat masks. Press-forming was applied to these flat masks then the press-form quality was determined. Table 13 shows the average austenite grain size, conditions for annealing before press-forming and gathering degree of {211} planes of each material. Table 14 shows the tensile properties, press-formability and etching performance. Etching performance was determined by visual observation of irregularities appeared on the etched flat masks. The measuring methods for each property were the same as in Example 1. Table 13 and Table 14 indicate that materials No. 85 through No. 87 which satisfy the conditions of chemical composition and manufacturing process specified in the present invention give favorable states without irregularities in etching, a gathering degree of (211) planes of 16% or less, and 0.2% proof stress within the range specified in this invention. All of these materials show excellent press-form quality. Therefore, it is important to keep the chemical composition and manufacturing process specified in this invention to obtain the satisfactory press-form quality aimed for by this invention. If these conditions are satisfied, an alloy sheet subjected to etching after annealing before press-forming gives a flat mask having the desired etching performance free of irregularities. As described in detail in Example 1 through Example 5, alloy sheets having a gathering degree of {211} planes higher than 16% give lower elongation perpendicular to rolling direction after annealing before press-forming than that of the preferred embodiment of this invention. An increased degree of {211} planes presumably decreases the elongation and induces cracks on alloy sheets during press-forming. Material No. Alloy No. Average austenite grain size before finish cold-rolling (µm) Annealing conditions before press-forming Gathering degree of {211} planes Temperature (°C) Time (min.) 85 1 18 750 20 7 86 1 17 790 2 15 87 4 13 720 40 16 Material No. Tensile properties Press-formability Etching performance 0.2% Proof strength (kgf/mm 2 ) Elongation perpendicular to the rolling direction (%) Shape fixability Fit with die Cracking in the alloy sheet 85 27.4 43.0 O ○ ○ None No irregularities 86 28.0 42.0 ○ ○ None No irregularities 87 28.0 41.2 ○ ○ None No irregularities Example 6 Hot-rolled sheets of alloy No. 1, 4, 9, 10, 12, 14, 21 and 22 which were used in Example 1 were employed. These hot-rolled sheet were subjected to a process including annealing (at 930°C), cold-rolling, recrystallization annealing (at 890°C for 1 min.), finish cold-rolling (at a reduction ratio of 21%) and stress relief annealing to obtain alloy sheets having a thickness of 0.25 mm. The alloy sheets were etched to make flat masks, which flat masks were then subjected to annealing before press-forming under the conditions shown in Table 12 to obtain materials No. 67 through No. 84. These materials were press-formed to determine their press-formability. Table 15 shows average austenite grain size before finish cold-rolling, conditions for annealing before press-forming, gathering degree of {211} planes, tensile properties and press-formability. Table 10 and Table 11 show the gathering degree of {211} planes and press-formability. The methods used for measuring properties were the same as in Example 1. Table 15 shows that materials No. 67, No. 69, No. 70 and No. 76 through No. 84, which satisfy the conditions of chemical composition and hot-rolled sheet annealing, finish cold-rolling (reduction ratio of finish cold rolling), annealing before press-forming (temperature, time) specified in the present invention give a gathering degree of {211} planes of 16% or less. All of these materials give the 0.2% proof stress aimed for in this invention and show high press-forming quality. Contrary to the above preferred embodiment, comparative materials No. 72 and No. 73 were annealed before press-forming at a temperature and for a time above the upper limits of the present invention though they satisfied the conditions of chemical composition, hot-rolled sheet annealing and finish cold-rolling (reduction ratio of finish cold-rolling) specified in the present invention. They exhibited a gathering degree of {211} planes of 16% or more and cracks were generated. Comparative material No. 63 was annealed before press-forming at a temperature (T) and for a time (t) not satisfying the equation T ≥ -48.1 log t + 785. Comparative material No. 71 was annealed before press-forming for a time above the upper limit of the present invention and annealing temperature T and annealing time t not satisfying the above described equation. All of these comparative materials gave 0.2% proof stress of more than 27.5 kgf/mm 2 , and they had problems with shape fixability during press-forming. The degree of {211} planes of these materials exceeded 16%, and cracks were generated on the alloy sheets. Materials No. 74 and No. 75 employed comparative alloys. Even if annealing before press-forming is carried out at 750°C for 50 min., their 0.2% proof stress values exceeded 27.5 kgf/mm 2 and they had problems with shape fixability during press-forming. The gathering degree of {211} planes of these materials exceeded 16%, and cracks were generated in the alloy sheets. As described in detail above, even under the condition that the chemical composition, conditions for hot-rolled sheet annealing and reduction ratio of finish cold-rolling are kept in the ranges specified in this invention, it is important to keep the conditions for annealing before press-forming within the ranges specified in this invention to obtain the satisfactory press-form quality aimed for by this invention. Example 7 Hot-rolled sheets of alloy No. 1 and No. 4, which were used in Example 1, were employed. These sheets were subjected to annealing (at 930°C), cold-rolling, recrystallization annealing, cold rolling, recrystallization annealing (at 890°C for 1 min.), finish cold-rolling (at a reduction ratio of 21%) and stress relief annealing to obtain alloy sheets having a thickness of 0.25 mm. These alloy sheets were annealed before press-forming under the conditions shown in Table 16 to obtain materials No. 85 through No. 87. The alloy sheets were etched to make flat masks. Press-forming was applied to these flat masks then their press-formability was determined. Table 13 shows the average austenite grain size, conditions for annealing before press-forming and gathering degree of {211} planes of each material. Table 17 shows the tensile properties, press-formability and etching performance. Etching performance was determined by visual observation of irregularities appearing on the etched flat masks. The measuring methods for each property were the same as in Example 6. Table 16 and Table 17 indicate that materials No. 85 through No. 87 which satisfy the conditions for chemical composition and manufacturing process specified in the present invention give favorable states without irregularities in etching, a degree of {211} planes of 16% or less, and 0.2% proof stresses within the ranges specified in this invention. All of these materials showed excellent press-form quality. Therefore, it is important to keep the chemical composition and manufacturing process specified in this invention to obtain the satisfactory press-formability aimed for by this invention. If these conditions are satisfied, an alloy sheet subjected to etching after annealing before press-forming gives a flat mask having the desired etching performance free of irregularities. Material No. Alloy No. Average austenite grain size before finish cold-rolling (µm) Annealing conditions before press-forming Gathering degree of {211} planes (%) Temperature (°C) Time(min) 85 1 18 750 20 8 86 1 17 790 2 16 87 4 13 720 40 15 Material No. Tensile properties Press-formability Etching performance 0.2% proof stress (kfg/mm 2 ) Elongation perpendicular to the rolling direction (%) Shape fixability Fit with die Cracking in the alloy sheet 85 26.9 42.6 O ○ ○ None No irregularities 86 27.5 41.3 ○ ○ None No irregularities 87 27.5 4.04 ○ ○ None No irregularities As described in detail in Example 6 and Example 7, alloy sheets having higher than 16% of the gathering degree of {211} planes give lower elongation perpendicular to rolling direction after annealing before press-forming than that of the preferred embodiment of this invention. An increased gathering degree of {211} planes presumably decreases the elongation and induces cracks in the alloy sheets during press-forming.

Claims: Claims for the following Contracting State : GB An alloy sheet for making a shadow mask consisting of 34 to 38 wt.% of Ni, 0.001-0.07 wt.% of Si, 0.002 wt.% or less of B, 0.002 wt.% or less of O, 0.0001-0.002 wt.% of N, 0-1 wt.% of Co, optionally 0.0001-0.005 wt.% of C, optionally 0.001-0.35 wt.% of Mn, optionally 0.001-0.05 wt.% of Cr, and a balance of Fe and inevitable impurities; said alloy sheet after annealing before press-forming having 0.2% proof stress of 28 kgf/mm 2 or less; and a gathering degree of {211} plane on a surface of said alloy sheet being 16% or less. An alloy sheet according to Claim 1, wherein said Ni content is 35 to 37 wt.%. An alloy sheet according to Claim 2, wherein said Ni content is 35.5 to 36.5 wt.%. An alloy sheet according to Claim 1 or 3, wherein said O content is 0.001 to 0.002 wt.%. An alloy sheet according to Claim 1, wherein said Co content is either 0(nil) or 0.001-1 wt.%. An alloy sheet for making a shadow mask consisting of 28 to 38 wt.% of Ni, 0.001-0.07 wt.% of Si, 0.002 wt.% or less of B, 0.002 wt.% or less of O, 0.0001-0.002 wt.% of N, over 1 to 7 wt.% of Co, optionally 0.0001-0.005 wt.% of C, optionally 0.001-0.35 wt.% of Mn, optionally 0.001-0.05 wt.% of Cr, and a balance of Fe and inevitable impurities; said alloy sheet after annealing before press-forming having 0.2% proof stress of 28 kgf/mm 2 or less; and a gathering degree of {211} plane on a surface of said alloy sheet being 16% or less. An alloy sheet according to Claim 6, wherein said Ni content is 30 to 33 wt.%. An alloy sheet according to Claim 6 or Claim 7, wherein said Co content is 3 to 6 wt.%. An alloy sheet according to any of Claims 6-8, wherein said O content is 0.001 to 0.002 wt.%. An alloy sheet according to Claim 1 or Claim 6, wherein said 0.2% proof stress is 27.5 kgf/mm 2 or less. An alloy sheet according to Claim 10, wherein said 0.2% proof stress is 27 kgf/mm 2 or less. A method of manufacturing an alloy sheet for a shadow mask comprising the steps of: (a) preparing a hot rolled-sheet containing Fe, Ni and optionally Co; (b) annealing said hot-rolled sheet in a temperature range of 910 to 990°C; (c) a first cold-rolling step of cold-rolling said annealed hot-rolled sheet to produce a cold-rolled sheet; (d) a first crystallization annealing step of annealing said cold-rolled sheet subjected to the first cold-rolling; (e) a second cold-rolling step of cold-rolling said cold-rolled sheet subjected to the recrystallization annealing; (f) a final recrystallization annealing step of annealing said cold-rolled sheet subjected to the second cold-rolling; (g) a finish cold-rolling step of cold-rolling of the cold-rolled sheet subjected to the finish recrystallization annealing at a cold-rolling reduction ratio in response to an average austenite grain size D (µm)yielded by the finishing recrystallization annealing, the reduction ratio of final cold-rolling R _ (%) satisfying the equations below; 16≤R≤75, 6.38D-133.9≤R≤6.38D-51.0 (h) a softening annealing step of annealing said cold-rolled sheet subjected to the finishing cold-rolling in a temperature range of 720 to 790°C for 2 to 40 min. before press-forming and on conditions satisfying the equation below; T≥-53.8 logt + 806, where T(°C) is the temperature and t(min.) is the time of the annealing. A method according to Claim 12, wherein said hot-rolled sheet consists of 34 to 38 wt.% of Ni, 0.001-0.07 wt.% of Si, 0.002 wt.% or less of B, 0.002 or less of O, 0.0001-0.002 wt.% of N, 0 (nil) or 0.001-1 wt.% of Co, optionally 0.0001-0.005 wt.% of C, optionally 0.001-0.35 wt.% of Mn, optionally 0.001-0.05 wt.% of Cr, and a balance of Fe and inevitable impurities. A method according to Claim 12, wherein said hot-rolled sheet consists of 28 to 38 wt.% of Ni, 0.001-0.07 wt.% of Si, 0.002 wt.% or less of B, 0.002 or less of O, 0.0001-0.002 wt.% of N, over 1 to 7 wt.% of Co, optionally 0.0001-0.005 wt.% of C, optionally 0.001-0.35 wt.% of Mn, optionally 0.001-0.05 wt.% of Cr, and a balance of Fe and inevitable impurities. A method according to Claim 12, wherein said finishing cold-rolling is performed at the cold-rolling reduction ratio in response to the average austenite grain size D (µm) yielded by the final recrystallization annealing, the cold-rolling reduction ratio R (%) satisfying the equations below; 21≤R≤70, 6.38D-122.6≤R≤6.38D-65.2. A method according to Claim 15, wherein said finish cold-rolling is performed at the cold-rolling reduction ratio in response to the average austenite grain size D (µm) yielded by the final recrystallization annealing, the cold-rolling reduction ratio R(%) satisfying the equations below; 26≤R≤63, 6.38D-108.0≤R≤6.38D-79.3. A method according to Claim 12, wherein said finish recrystallization annealing is performed in the temperature range of 860 to 950°C for 0.5 to 2 min. Claims for the following Contracting States : FR, DE An alloy sheet for making a shadow mask consisting of 34 to 38 wt.% of Ni, 0.001-0.07 wt.% of Si, 0.002 wt.% or less of B, 0.002 wt.% or less of O, 0.0001-0.002 wt.% of N, 0.001-1 wt.% of Co, optionally 0.0001-0.005 wt.% of C, optionally 0.001-0.35 wt.% of Mn, optionally 0.001-0.05 wt.% of Cr, and a balance of Fe and inevitable impurities; said alloy sheet after annealing before press-forming having 0.2% proof stress of 28 kgf/mm 2 or less; and a gathering degree of {211} plane on a surface of said alloy sheet being 16% or less. An alloy sheet according to Claim 1, wherein said Ni content is 35 to 37 wt.%. An alloy sheet according to Claim 2, wherein said Ni content is 35.5 to 36.5 wt.%. An alloy sheet according to Claim 1 or 3, wherein said O content is 0.001 to 0.002 wt.%. An alloy sheet for making a shadow mask consisting of 28 to 38 wt.% of Ni, 0.001-0.07 wt.% of Si, 0.002 wt.% or less of B, 0.002 wt.% or less of O, 0.0001-0.002 wt.% of N, over 1 to 7 wt.% of Co, optionally 0.0001-0.005 wt.% of C, optionally 0.001-0.35 wt.% of Mn, optionally 0.001-0.05 wt.% of Cr, and a balance of Fe and inevitable impurities; said alloy sheet after annealing before press-forming having 0.2% proof stress of 28 kgf/mm 2 or less; and a gathering degree of {211} plane on a surface of said alloy sheet being 16% or less. An alloy sheet according to Claim 5, wherein said Ni content is 30 to 33 wt.%. An alloy sheet according to Claim 5 or Claim 6, wherein said Co content is 3 to 6 wt.%. An alloy sheet according to any of Claims 5-7, wherein said O content is 0.001 to 0.002 wt.%. An alloy sheet according to Claim 1 or Claim 5, wherein said 0.2% proof stress is 27.5 kgf/mm 2 or less. An alloy sheet according to Claim 9, wherein said 0.2% proof stress is 27 kgf/mm 2 or less. A method of manufacturing an alloy sheet for a shadow mask comprising the steps of: (a) preparing a hot rolled-sheet containing Fe, Ni and Co; (b) annealing said hot-rolled sheet in a temperature range of 910 to 990°C; (c) a first cold-rolling step of cold-rolling said annealed hot-rolled sheet to produce a cold-rolled sheet; (d) a first crystallization annealing step of annealing said cold-rolled sheet subjected to the first cold-rolling; (e) a second cold-rolling step of cold-rolling said cold-rolled sheet subjected to the recrystallization annealing; (f) a final recrystallization annealing step of annealing said cold-rolled sheet subjected to the second cold-rolling; (g) a finish cold-rolling step of cold-rolling of the cold-rolled sheet subjected to the finish recrystallization annealing at a cold-rolling reduction ratio in response to an average austenite grain size D (µm)yielded by the finishing recrystallization annealing, the reduction ratio of final cold-rolling R (%) satisfying the equations below; 16≤R≤75, 6.38D-133.9≤R≤6.38D-51.0 (h) a softening annealing step of annealing said cold-rolled sheet subjected to the finishing cold-rolling in a temperature range of 720 to 790°C for 2 to 40 min. before press-forming and on conditions satisfying the equation below; T≥-53.8 logt + 806, where T(°C) is the temperature and t(min.) is the time of the annealing. A method according to Claim 11, wherein said hot-rolled sheet consists of 34 to 38 wt.% of Ni, 0.001-0.07 wt.% of Si, 0.002 wt.% or less of B, 0.002 or less of O, 0.0001-0.002 wt.% of N, 0.001-1 wt.% of Co, optionally 0.0001-0.005 wt.% of C, optionally 0.001-0.35 wt.% of Mn, optionally 0.001-0.05 wt.% of Cr, and a balance of Fe and inevitable impurities. A method according to Claim 11, wherein said hot-rolled sheet consists of 28 to 38 wt.% of Ni, 0.001-0.07 wt.% of Si, 0.002 wt.% or less of B, 0.002 or less of O, 0.0001-0.002 wt.% of N, over 1 to 7 wt.% of Co, optionally 0.0001-0.005 wt.% of C, optionally 0.001-0.35 wt.% of Mn, optionally 0.001-0.05 wt.% of Cr, and a balance of Fe and inevitable impurities. A method according to Claim 11, wherein said finishing cold-rolling is performed at the cold-rolling reduction ratio in response to the average austenite grain size D (µm) yielded by the final recrystallization annealing, the cold-rolling reduction ratio R (%) satisfying the equations below; 21≤R≤70, 6.38D-122.6≤R≤6.38D-65.2. A method according to Claim 14, wherein said finish cold-rolling is performed at the cold-rolling reduction ratio in response to the average austenite grain size D (µm) yielded by the final recrystallization annealing, the cold-rolling reduction ratio R(%) satisfying the equations below; 26≤R≤63, 6.38D-108.0≤R≤6.38D-79.3. A method according to Claim 11, wherein said finish recrystallization annealing is performed in the temperature range of 860 to 950°C for 0.5 to 2 min.

Inventors: HIASA MICHIHITO, INOUE TADASHI, TSURU KIYOSHI, HIASA, MICHIHITO, INOUE, TADASHI, TSURU, KIYOSHI, HIASA, MICHIHITO, C/O INTELLECTUAL PROP. DEPT., INOUE, TADASHI, C/O INTELLECTUAL PROP. DEPT., TSURU, KIYOSHI, C/O INTELLECTUAL PROP. DEPT.
Applicants: NIPPON KOKAN KK, NKK CORPORATION
Application year: 1993
Main classification: C22C38
IPC codes: C21D8, H01J9, C22C38