Patent Publication Number: US-2021181686-A1

Title: Watch Outer Packaging Component And Watch

Description:
The present application is based on, and claims priority from JP Application Serial Number 2019-225197, filed Dec. 13, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a watch outer packaging component, a watch, and a method for manufacturing a watch outer packaging component. 
     2. Related Art 
     JP 2009-69049 A discloses a watch housing using ferritic stainless steel in which a surfacing layer is austenitized by nitrogen absorption treatment, specifically, a case band and a case back. 
     In JP 2009-69049 A, austenitization of the surfacing layer of ferritic stainless steel results in hardness and corrosion resistance required as a watch housing. 
     However, in JP 2009-69049 A, on an inner side of the watch housing as well, a surfacing layer similar to that on an outer side is formed, and thus when the housing is made to have a predetermined thickness, for example, about  4 mm, a thickness of an inner layer portion formed of a ferrite phase decreases, thereby deteriorating an antimagnetic performance. 
     On the other hand, when the thickness of the watch housing is increased in order to thicken the inner layer portion, the watch increases in size. 
     In other words, JP 2009-69049 A has a problem in that it is difficult, while maintaining a predetermined size as the watch, to ensure desired antimagnetic performance. 
     SUMMARY 
     A watch outer packaging component of the present disclosure is a watch outer packaging component formed of austenitized ferritic stainless steel including a base formed of a ferrite phase and a surfacing layer formed of an austenitized phase in which the ferrite phase is austenitized, the watch outer packaging component abutting on a sealing member that partitions between a space inside a watch and a space outside the watch, wherein the surfacing layer includes an outer surfacing layer provided at an outer surface facing the space outside the watch, and an inner surfacing layer provided at an inner surface facing the space inside the watch, and the inner surfacing layer is thinner in thickness than the outer surfacing layer. 
     A watch outer packaging component of the present disclosure is a watch outer packaging component formed of austenitized ferritic stainless steel including a base formed of a ferrite phase and a surfacing layer formed of an austenitized phase in which the ferrite phase is austenitized, the watch outer packaging component abutting on a sealing member that partitions between a space inside a watch and a space outside the watch, wherein the surfacing layer includes an outer surfacing layer provided at an outer surface facing the space outside the watch, and the surfacing layer is not provided at an inner surface facing the space inside the watch. 
     A watch outer packaging component of the present disclosure is a watch outer packaging component formed of austenitized ferritic stainless steel including a base formed of a ferrite phase and a surfacing layer formed of an austenitized phase in which the ferrite phase is austenitized, wherein the surfacing layer includes a first surfacing layer provided at an inner surface facing a space inside a watch, and a second surfacing layer provided at an outer surface facing a space outside the watch, and the first surfacing layer is thinner in thickness than the second surfacing layer. 
     A watch including a watch outer packaging component of the present disclosure. 
     A method for manufacturing a watch outer packaging component of the present disclosure is a method for manufacturing a watch outer packaging component formed of austenitized ferritic stainless steel including a base formed of a ferrite phase and a surfacing layer formed of an austenitized phase in which the ferrite phase is austenitized, the watch outer packaging component abutting on a sealing member that partitions between a space inside the watch and a space outside the watch, that includes a first processing step for processing ferritic stainless steel to form a base material, a heat treatment step for performing nitrogen absorption treatment on the base material to form the surfacing layer, and a second processing step for cutting the surfacing layer to form the watch outer packaging component, wherein in the second processing step, an inner surfacing layer, of the surfacing layer, provided on an inner surface facing a space inside the watch is cut so as to be thinner in thickness than an outer surfacing layer provided on an outer surface facing a space outside the watch. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial cross-sectional view schematically illustrating a watch of a first exemplary embodiment. 
         FIG. 2  is a cross-sectional view illustrating a main part of a case main body of the first exemplary embodiment. 
         FIG. 3  is a schematic diagram illustrating a manufacturing step of the case main body of the first exemplary embodiment. 
         FIG. 4  is a schematic diagram illustrating a manufacturing step of the case main body of the first exemplary embodiment. 
         FIG. 5  is a schematic diagram illustrating a manufacturing step of the case main body of the first exemplary embodiment. 
         FIG. 6  is a cross-sectional view illustrating a main part of a case main body of a second exemplary embodiment. 
         FIG. 7  is a partial cross-sectional view schematically illustrating a watch of a third exemplary embodiment. 
         FIG. 8  is a cross-sectional view illustrating a main part of a case main body of a fourth exemplary embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     First Exemplary Embodiment 
     A watch  1  of a first exemplary embodiment of the present disclosure will be described below with reference to the drawings. 
       FIG. 1  is a partial cross-sectional view schematically illustrating the watch  1  of the present exemplary embodiment. 
     As illustrated in  FIG. 1 , the watch  1  includes an outer packaging case  2 . The outer packaging case  2  includes a cylindrical case main body  21 , a case back  22  fixed to a back surface side of the case main body  21 , an annular bezel  23  fixed to a front surface side of the case main body  21 , and a glass plate  24  held by the bezel  23 . Furthermore, a dial  11  and a movement (not illustrated) are housed in the case main body  21 . Note that, the case main body  21  is an example of a watch outer packaging component of the present disclosure. 
     A winding stem pipe  25  fits into and is fixed to the case main body  21 , and a shaft portion  261  of a crown  26  is rotatably inserted into the winding stem pipe  25 . 
     The case main body  21  and the bezel  23  engage with each other via a plastic packing  27 , and the bezel  23  and the glass plate  24  are fixed to each other by a plastic packing  28 . 
     Furthermore, the case back  22  is fitted into or screwed with the case main body  21 , and a ring-shaped rubber packing or case back packing  40  is interposed in a seal portion  50  in a compressed state. With this configuration, the seal portion  50  is liquid-tightly sealed, and a waterproof function is obtained. 
     Here, in the present exemplary embodiment, the winding stem pipe  25 , the plastic packing  27 , and the case back packing  40  partition a space in which the movement and the like of the case main body  21  are housed, that is, a space inside the watch, and a space outside the case main body  21 , that is, a space outside the watch. In other words, the winding stem pipe  25 , the plastic packings  27  and  28 , and the case back packing  40  are an example of a sealing member of the present disclosure that abuts on the case main body  21 . 
     A groove  262  is formed at an outer periphery halfway the shaft portion  261  of the crown  26 , and a ring-shaped rubber packing  30  is fitted into the groove  262 . The rubber packing  30  adheres to an inner circumferential surface of the winding stem pipe  25 , and is compressed between the inner circumferential surface and an inner surface of the groove  262 . According to this configuration, a gap between the crown  26  and the winding stem pipe  25  is liquid-tightly sealed and a waterproof function is obtained. Note that, when the crown  26  is rotated and operated, the rubber packing  30  rotates together with the shaft portion  261  and, slides in a circumferential direction while adhering to the inner circumferential surface of the winding stem pipe  25 . 
     Case Main Body 
       FIG. 2  is an enlarged cross-sectional view of a main part of the case main body  21 , specifically, a region II in  FIG. 1 . 
     As illustrated in  FIG. 2 , the case main body  21  is formed of ferritic stainless steel including a base  211  formed of a ferrite phase, a surfacing layer  212  formed of an austenite phase (hereinafter, an austenitized phase) in which the ferrite phase is austenitized, and a mixed layer  213  in which the ferrite phase and the austenitized phase are mixed with each other. 
     Base 
     The base  211  contains, in percent by mass, Cr: 18 to 22%, Mo: 1.3 to 2.8%, Nb: 0.05 to 0.50%, Cu: 0.1 to 0.8%, Ni: less than 0.5%, Mn: less than 0.8%, Si: less than 0.5%, P: less than 0.10%, S: less than 0.05%, N: less than 0.05%, and C: less than 0.05%, with a balance being formed of ferritic stainless steel formed of Fe and unavoidable impurities. 
     Cr is an element that increases a transfer rate of nitrogen to the ferrite phase, and a diffusion rate of nitrogen in the ferrite phase, in nitrogen absorption treatment. When Cr is less than 18%, the transfer rate and diffusion rate of nitrogen decrease. Furthermore, when Cr is less than 18%, corrosion resistance of the surfacing layer  212  deteriorates. On the other hand, when Cr exceeds 22%, hardening occurs, and workability as a material worsens. Furthermore, when Cr exceeds 22%, anaesthetic appearance is spoiled. Thus, Cr content may be 18 to 22%, may be 20 to 22%, and may be 19.5 to 20.5%. 
     Mo is an element that increases the transfer rate of nitrogen to the ferrite phase, and the diffusion rate of nitrogen in the ferrite phase, in the nitrogen absorption treatment. When Mo is less than 1.3%, the transfer rate and diffusion rate of nitrogen decrease. Furthermore, when Mo is less than 1.3%, corrosion resistance as a material deteriorates. On the other hand, when Mo exceeds 2.8%, hardening occurs, and the workability as the material worsens. Furthermore, when Mo exceeds 2.8%, a configuration organization of the surfacing layer  212  becomes significantly heterogeneous, and the aesthetic appearance is spoiled. Thus, Mo content may be 1.3 to 2.8%, may be 1.8 to 2.8%, and may be 2.25 to 2.35%. 
     Nb is an element that increases the transfer rate of nitrogen to the ferrite phase, and the diffusion rate of nitrogen in the ferrite phase, in the nitrogen absorption treatment. When Nb is less than 0.05%, the transfer rate and diffusion rate of nitrogen decrease. On the other hand, when Nb exceeds 0.50%, hardening occurs, and the workability as the material worsens. Furthermore, a deposition section is generated, and the aesthetic appearance is spoiled. Thus, Nb content maybe 0.05 to 0.50%, maybe 0.05 to 0.35%, and may be 0.15 to 0.25%. 
     Cu is an element that controls absorption of nitrogen in the ferrite phase in the nitrogen absorption treatment. When Cu is less than 0.1%, a variation in a nitrogen content in the ferrite phase increases. On the other hand, when Cu exceeds 0.8%, the transfer rate of nitrogen to the ferrite phase decreases. Thus, the Cu content may be 0.1 to 0.8%, may be 0.1 to 0.2%, and may be 0.1 to 0.15%. 
     Ni is an element that inhibits the transfer of nitrogen to the ferrite phase, and the diffusion of nitrogen in the ferrite phase, in the nitrogen absorption treatment. When Ni is equal to or greater than 0.5%, the transfer rate and the diffusion rate of nitrogen decrease. Furthermore, it is possible that corrosion resistance worsens, and that it becomes difficult to prevent occurrence of a metal allergy and the like. Thus, Ni content may be less than 0.5%, may be less than 0.2%, and may be less than 0.1%. 
     Mn is an element that inhibits the transfer of nitrogen to the ferrite phase, and the diffusion of nitrogen in the ferrite phase, in the nitrogen absorption treatment. When Mn is equal to or greater than 0.8%, the transfer rate and the diffusion rate of nitrogen decrease. Thus, Mn content may be less than 0.8%, may be less than 0.5%, and may be less than 0.1%. 
     Si is an element that inhibits the transfer of nitrogen to the ferrite phase, and the diffusion of nitrogen in the ferrite phase, in the nitrogen absorption treatment. When Si is equal to or greater than 0.5%, the transfer rate and the diffusion rate of nitrogen decrease. Thus, Si content may be less than 0.5%, and may be less than 0.3%. 
     P is an element that inhibits the transfer of nitrogen to the ferrite phase, and the diffusion of nitrogen in the ferrite phase, in the nitrogen absorption treatment. When P is equal to or greater than 0.10%, the transfer rate and the diffusion rate of nitrogen decrease. Thus, P content may be less than 0.10%, and may be less than 0.03%. 
     S is an element that inhibits the transfer of nitrogen to the ferrite phase, and the diffusion of nitrogen in the ferrite phase, in the nitrogen absorption treatment. When S is equal to or greater than 0.05%, the transfer rate and the diffusion rate of nitrogen decrease. Thus, S content may be less than 0.05%, and may be less than 0.01%. 
     N is an element that inhibits the transfer of nitrogen to the ferrite phase, and the diffusion of nitrogen in the ferrite phase, in the nitrogen absorption treatment. When N is equal to or greater than 0.05%, the transfer rate and the diffusion rate of nitrogen decrease. Thus, N content may be less than 0.05%, and may be less than 0.01%. 
     C is an element that inhibits the transfer of nitrogen to the ferrite phase, and the diffusion of nitrogen in the ferrite phase, in the nitrogen absorption treatment. When C is equal to or greater than 0.05%, the transfer rate and the diffusion rate of nitrogen decrease. Thus, C content may be less than 0.05%, and may be less than 0.02%. 
     Note that, the base  211  is not limited to the configuration described above, and it is sufficient that the base  211  is formed of the ferrite phase. 
     Surfacing Layer 
     The surfacing layer  212  is provided by performing the nitrogen absorption treatment on the base material forming the base  211 , to austenitize the ferrite phase. In the present exemplary embodiment, a nitrogen content in the surfacing layer  212  is set to 1.0 to 1.6% in percent by mass. In other words, nitrogen is contained at high concentrations in the surfacing layer  212 . Accordingly, anticorrosive performance in the surfacing layer  212  can be improved. 
     In addition, in the present exemplary embodiment, the surfacing layer  212  includes an outer surfacing layer  2121  and an inner surfacing layer  2122 . The outer surfacing layer  2121  is the surfacing layer  212  provided outside the plastic packing  27 , that is, on an outer surface  214  facing the space outside the watch. In addition, the inner surfacing layer  2122  is the surfacing layer  212  provided inside the plastic packing  27 , that is, on an inner surface  215  facing the space inside the watch. 
     Here, in  FIG. 1 , the outer surface  214  of the outer surfacing layer  2121  is denoted by a thick line. Additionally, in the present exemplary embodiment, a surface of the case main body  21  that contacts the plastic packing  27  is referred to as the outer surface  214  facing an outside of the watch. 
     Note that, the inner surfacing layer  2122  is an example of a first surfacing layer of the present disclosure, and the outer surfacing layer  2121  is an example of a second surfacing layer of the present disclosure. 
     Here, in the present exemplary embodiment, the inner surfacing layer  2122  is provided such that a thickness a is thinner than a thickness b of the outer surfacing layer  2121 . Specifically, the thickness a of the inner surfacing layer  2122  is set to approximately  40  pm, and the thickness b of the outer surfacing layer  2121  is set to approximately 350 μm. 
     Note that, the outer surfacing layer  2121  is not limited to the configuration described above. For example, the thickness b of the outer surfacing layer  2121  may be set to equal to or greater than 350 μm, and may be set to equal to or greater than 100 μm and equal to or less than 600 μm. With the configuration described above, it is possible to ensure predetermined corrosion resistance, and it is possible to prevent a nitrogen absorption treatment time from becoming too long. Further, the inner surfacing layer  2122  is not limited to the configuration described above. For example, the thickness a of the inner surfacing layer  2122  may be set to equal to or greater than 40 μm, and may be set to equal to or less than 100 μm. 
     In addition, each of the thicknesses a and b is a thickness of a layer formed of the austenitized phase, and, for example, in a visual field when SEM observation is performed at a magnification of 500 to 1000, is a shortest distance from the outer surface  214  to a ferrite phase of an outer mixed layer  2131  described below, or a shortest distance from the inner surface  215  to a ferrite phase of an inner mixed layer  2132  described below. Alternatively, a shallowest austenitized phase from the outer surface  214  or a shallowest austenitized phase from the inner surface  215 . Additionally, when a distance from the outer surface  214  or the inner surface  215  to each of a plurality of points that is short in distance to the ferrite phase is measured, an average value thereof may be defined as the thickness a of the outer surfacing layer  2121  or the thickness b of the inner surfacing layer  2122 . 
     Mixed Layer 
     In a step of forming the surfacing layer  212 , the mixed layer  213  is generated by a variation in transfer rate of nitrogen entering the base  211  formed of the ferrite phase. In other words, at a location where the transfer rate of nitrogen is high, nitrogen enters into a deep location of the ferrite phase and the location is austenitized, and at a location where the transfer rate of nitrogen is low, the ferrite phase is austenitized only up to a shallow location, thus the mixed layer  213  is formed in which the ferrite phase and the austenitized phase are mixed with each other with respect to a depth direction. Note that, the mixed layer  213  is a layer including a shallowest site to a deepest site of the austenitized phase when viewed in a cross-section, and is a layer thinner than the surfacing layer  212 . 
     Here, in the present exemplary embodiment, the mixed layer  213  includes the outer mixed layer  2131  and the inner mixed layer  2132 . The outer mixed layer  2131  is a layer formed between the base  211  and the outer surfacing layer  2121 . In addition, the inner mixed layer  2132  is a layer formed between the base  211  and the inner surfacing layer  2122 . 
     Method for Manufacturing Case Main Body 
     Next, a method for manufacturing the case main body  21  will be described. 
       FIGS. 3 to 5  are schematic diagrams each illustrating a manufacturing step of the case main body  21 . 
     As illustrated in  FIG. 3 , first, ferritic stainless steel is subjected to a machine process to form a base material  200 . At this time, ferritic stainless steel is cut such that a thickness of a location corresponding to the inner surfacing layer  2122  is larger than a thickness of a location corresponding to the outer surfacing layer  2121  by a predetermined dimension. 
     Note that, the step of processing ferritic stainless steel to form the base material  200  is an example of a first processing step of the present disclosure. 
     Next, as illustrated in  FIG. 4 , the nitrogen absorption treatment is performed on the base material  200  processed as described above. Accordingly, nitrogen enters the base material  200  from a surface, the ferrite phase is austenitized, and a layer corresponding to the surfacing layer  212  is formed. 
     Note that, the step of performing the nitrogen absorption treatment on the base material  200  to form the surfacing layer is an example of a heat treatment step of the present disclosure. 
     Finally, as illustrated in  FIG. 5 , by cutting the layer corresponding to the surfacing layer  212  of the base material  200  by a predetermined amount, the case main body  21  as described above is formed. At this time, in the present exemplary embodiment, the cutting is performed such that the inner surfacing layer  2122  is thinner in thickness than the outer surfacing layer  2121 . Specifically, the base material  200  is cut such that the thickness of the inner surfacing layer  2122  is approximately 100 μm, and the thickness of the outer surfacing layer  2121  is approximately 350 μm. 
     Note that, the step for cutting the base material  200  to form the case main body  21  is an example of a second processing step of the present disclosure. 
     Advantageous Effects of First Exemplary Embodiment 
     According to the first exemplary embodiment, the following advantageous effects can be produced. 
     The case main body  21  of the present exemplary embodiment is formed of austenitized ferritic stainless steel including the base  211  formed of the ferrite phase, and the surfacing layer  212  formed of the austenitized phase in which the ferrite phase is austenitized. Then, the surfacing layer  212  includes the outer surfacing layer  2121  provided on the outer surface  214  facing the space outside the watch, and the inner surfacing layer  2122  provided on the inner surface  215  facing the space inside the watch, and the inner surfacing layer  2122  is thinner in thickness than the outer surfacing layer  2121 . 
     Accordingly, the thickness of the inner surfacing layer  2122  is reduced, and thus, the outer surfacing layer  2121  can be made to have a thickness with which predetermined anticorrosive performance is obtained without increasing a thickness as the case main body  21 , and the base  211  can be made to have a thickness with which predetermined antimagnetic performance is obtained. Thus, while a predetermined size as the watch  1  is maintained, desired antimagnetic performance can be ensured. 
     Furthermore, in the present exemplary embodiment, the thickness of the inner surfacing layer  2122  is decreased, thus a distance between the movement housed in the case main body  21  and the base  211  formed of the ferrite phase can be shortened. Accordingly, influence of an external magnetic field on a motor or the like provided in the movement can be reduced, and the antimagnetic performance can be improved. 
     In the present exemplary embodiment, the thickness of the inner surfacing layer  2122  is equal to or less than 100 μm. 
     Accordingly, the distance between the movement housed in the case main body  21 , and the base  211  formed of the ferrite phase can be shortened, thereby improving the antimagnetic performance. 
     In the present exemplary embodiment, the thickness of the outer surfacing layer  2121  is equal to or greater than 100 μm and equal to or less than 600 μm. 
     Accordingly, the predetermined anticorrosive performance can be ensured, and it is possible to prevent the nitrogen absorption treatment time from becoming too long. 
     In the present exemplary embodiment, the mixed layer  213  is included that is formed between the base  211  and the surfacing layer  212  and in which the ferrite phase and the austenitized phase are mixed with each other. 
     Accordingly, in the nitrogen absorption treatment, a variation in the transfer rate of nitrogen can be tolerated, thereby making it possible to facilitate the nitrogen absorption treatment. 
     In the present exemplary embodiment, the base  211  contains, in percent by mass, Cr: 18 to 22%, Mo: 1.3 to 2.8%, Nb: 0.05 to 0.50%, Cu: 0.1 to 0.8%, Ni: less than 0.5%, Mn: less than 0.8%, Si: less than 0.5%, P: less than 0.10%, S: less than 0.05%, N: less than 0.05%, and C: less than 0.05%, with a balance being formed of Fe and unavoidable impurities. 
     This makes it possible to increase the transfer rate of nitrogen to the ferrite phase, and the diffusion rate of nitrogen in the ferrite phase, in the nitrogen absorption treatment. 
     In the present exemplary embodiment, the nitrogen content of the surfacing layer  212  is 1.0 to 1.6% in percent by mass. 
     Accordingly, anticorrosive performance in the surfacing layer  212  can be improved. 
     Second Exemplary Embodiment 
     Next, a second exemplary embodiment will be described based on  FIG. 6 . 
     The second exemplary embodiment differs from the first exemplary embodiment described above in that an inner surfacing layer and an inner mixed layer are not provided. 
     Note that, an identical configuration to that in the first exemplary embodiment will be given an identical reference numeral and detailed description will be omitted. 
       FIG. 6  is a cross-sectional view illustrating a main part of a case main body  21 A of the second exemplary embodiment. 
     As illustrated in  FIG. 6 , the case main body  21 A is formed of ferritic stainless steel including a base  211 A formed of a ferrite phase, a surfacing layer  212 A formed of an austenitized phase, and a mixed layer  213 A in which the ferrite phase and the austenitized phase are mixed with each other. 
     The base  211 A is formed of ferritic stainless steel as in the case of the base  211  of the first exemplary embodiment described above. 
     Further, similar to the surfacing layer  212  of the first exemplary embodiment described above, the surfacing layer  212 A is provided by austenitizing the ferrite phase forming the base  211 A. 
     Further, similar to the mixed layer  213  of the first exemplary embodiment described above, in a step of forming the surfacing layer  212 A, the mixed layer  213 A is generated by a variation in transfer rate of nitrogen entering the base  211 A formed of the ferrite phase. 
     In the present exemplary embodiment, the surfacing layer  212 A includes an outer surfacing layer  2121 A provided on an outer surface  214 A facing a space outside a watch. The mixed layer  213 A has an outer mixed layer  2131 A formed between the outer surfacing layer  2121 A and the base  211 A. 
     In the present exemplary embodiment, a thickness c of the outer surfacing layer  2121 A is set to approximately 350 μm, similar to the outer surfacing layer  2121  of the first exemplary embodiment described above. Note that, the outer surfacing layer  2121 A is not limited to the configuration described above. For example, the thickness c of the outer surfacing layer  2121 A may be set to equal to or greater than 350 μm, and may be defined as equal to or greater than 100 μm and equal to or less than 600 μm. 
     Here, in the present exemplary embodiment, the surfacing layer  212 A and the mixed layer  213 A are provided only on the outer surface  214 A. In other words, the surfacing layer  212 A and the mixed layer  213 A are not provided on the inner surface  215 A, and the base  211 A is exposed in a space inside the watch. 
     Accordingly, a distance between a movement housed in the case main body  21 A and the base  211 A formed of the ferrite phase can be shortened. 
     Note that, in the present exemplary embodiment, in the space inside the watch, the base  211 A formed of the ferrite phase is exposed, but since the space inside the watch is sealed off from the space outside the watch by the winding stem pipe  25 , the plastic packings  27 ,  28 , the case back packing  40 , and the like, an effect on corrosion is small. 
     Advantageous Effects of Second Exemplary Embodiment 
     According to the second exemplary embodiment described above, the following advantageous effects can be produced. 
     In the present exemplary embodiment, the surfacing layer  212 A includes the outer surfacing layer  2121 A provided on the outer surface  214 A facing the space outside the watch. Furthermore, the surfacing layer  212 A is not provided on the inner surface  215 A. 
     Thus, the outer surfacing layer  2121 A can be made to have a thickness with which predetermined anticorrosive performance is obtained without increasing a thickness as the case main body  21 A, and the base  211 A can be made to have a thickness with which predetermined antimagnetic performance is obtained. Thus, while maintaining a predetermined size as the watch, desired antimagnetic performance can be ensured. 
     Furthermore, in the present exemplary embodiment, since the surfacing layer  212 A is not provided on the inner surface  215 A, the distance between the movement housed in the case main body  21 A and the base  211 A can be shortened. Accordingly, influence of an external magnetic field on a motor or the like provided in the movement can be further reduced, and the antimagnetic performance can be further improved. 
     Third Exemplary Embodiment 
     Next, a third exemplary embodiment will be described based on  FIG. 7 . 
     The third exemplary embodiment differs from the first exemplary embodiment in that a case main body  21 B and a sensor  6 B engage with each other via a packing  7 B. 
     Note that, an identical configuration to that in the first and second exemplary embodiments will be given an identical reference numeral and detailed description will be omitted. 
       FIG. 7  is a partial cross-sectional view schematically illustrating a watch  1 B of the third exemplary embodiment. Note that  FIG. 7  is a partial cross-sectional view of the watch  1 B taken along a direction parallel to the dial  11 . 
     As illustrated in  FIG. 7 , the watch  1 B of the present exemplary embodiment includes the case main body  21 B, the sensor  6 B, and the packing  7 B. 
     In the present exemplary embodiment, the case main body  21 B and the sensor  6 B engage with each other via the packing  7 B. That is, the packing  7 B is an example of a sealing member of the present disclosure. 
     Sensor 
     The sensor  6 B includes a sensor main body  61 B, a sensor housing  62 B, a sensor cover  63 B, a mounting screw  64 B, a foreign material ingress prevention cover  65 B, and a waterproof packing  66 B, and is configured to be capable of measuring a pressure acting on the watch  1 B. In the present exemplary embodiment, the sensor  6 B is attached to watch  1 B for the purpose of measuring air pressure and water pressure. 
     Note that, the watch  1 B may have, by measuring air pressure and water pressure by the sensor  6 B, for example, an altitude estimation function, a weather prediction function, a water depth estimation function, a diving information display function, and the like, based on detected air pressure. 
     Furthermore, the sensor  6 B is not limited to the configuration described above, and, for example, may be configured to be capable of measuring a temperature of the watch  1 B. 
     In the present exemplary embodiment, the sensor main body  61 B is housed in the sensor housing  62 B attached to the case main body  21 B. Then, the sensor main body  61 B is fixed to the sensor housing  62 B by the waterproof packing  66 B. This seals a gap between the sensor main body  61 B and the sensor housing  62 B. 
     In this state, the foreign material ingress prevention cover  65 B is disposed so as to cover the sensor main body  61 B, and the sensor cover  63 B is disposed so as to cover the foreign material ingress prevention cover  65 B. The sensor cover  63 B is attached by the mounting screw  64 B to the sensor housing  62 B so that the sensor  6 B is attached to the case main body  21 B. 
     Here, in the present exemplary embodiment, the case main body  21 B is provided with an outer surfacing layer similar to the outer surfacing layer  2121  of the first exemplary embodiment described above, on an outer surface  214 B denoted by a thick line in  FIG. 7 . Furthermore, the case main body  21 B is provided with an inner surfacing layer similar to the inner surfacing layer  2122  of the first exemplary embodiment described above, on an inner surface  215 B. In other words, the inner surface  215 B is provided with the inner surfacing layer thinner in thickness than the outer surfacing layer provided on the outer surface  214 B. 
     Advantageous Effects of Third Exemplary Embodiment 
     According to the third exemplary embodiment described above, the following advantageous effects can be produced. 
     In the present exemplary embodiment, the case main body  21 B is provided with the inner surfacing layer thinner in thickness than the outer surfacing layer, on the inner surface  215 B. 
     Accordingly, as in the first and second exemplary embodiments described above, while a predetermined size as the watch  1 B is maintained, desired antimagnetic performance can be ensured. 
     In the present exemplary embodiment, since the sensor  6 B is attached to the case main body  21 B, the watch  1 B can have a function such as an altitude estimation function, a weather prediction function, a water depth estimation function, a diving information display function, and the like. 
     Fourth Exemplary Embodiment 
     Next, a fourth exemplary embodiment will be described based on  FIG. 8 . 
     The fourth exemplary embodiment differs from the first exemplary embodiment described above in that a step is provided between an outer surface  214 C and an inner surface  215 C. 
     Note that, an identical configuration to that in the first exemplary embodiment will be given an identical reference numeral and detailed description will be omitted. 
       FIG. 8  is a cross-sectional view illustrating a main part of a case main body  21 C of the fourth exemplary embodiment. 
     As illustrated in  FIG. 8 , the case main body  21 C is formed of ferritic stainless steel including a base  211 C formed of a ferrite phase, a surfacing layer  212 C formed of an austenitized phase, and a mixed layer  213 C in which the ferrite phase and the austenitized phase are mixed with each other. 
     The base  211 C is formed of ferritic stainless steel as in the case of the base  211  of the first exemplary embodiment described above. 
     Further, similar to the surfacing layer  212  of the first exemplary embodiment described above, the surfacing layer  212 C is provided by austenitizing the ferrite phase forming the base  211 C. 
     Further, similar to the mixed layer  213  of the first exemplary embodiment described above, in a step of forming the surfacing layer  212 C, the mixed layer  213 C is generated by a variation in transfer rate of nitrogen entering the base  211 C formed of the ferrite phase. Note that, as in the first exemplary embodiment described above, an outer mixed layer  2131 C is provided between the base  211 C and an outer surfacing layer  2121 C described later, and an inner mixed layer  2132 C is provided between the base  211 C and an inner surfacing layer  2122 C described later. 
     Here, in the present exemplary embodiment, the surfacing layer  212 C includes, similar to the first exemplary embodiment described above, the outer surfacing layer  2121 C and the inner surfacing layer  2122 C. Additionally, the step is provided between the outer surface  214 C of the outer surfacing layer  2121 C and the inner surface  215 C of the inner surfacing layer  2122 C. This is formed, for example, when the case main body  21 C is manufactured, by performing cutting such that the inner surfacing layer  2122 C is thinner in thickness than the outer surfacing layer  2121 C so as to provide a step. In other words, in a first processing step, a base material is formed such that a location corresponding to the outer surfacing layer  2121 C and a location corresponding to the inner surfacing layer  2122 C are identical in thickness to each other. Then, in a second processing step after a heat treatment step, cutting is performed such that the inner surfacing layer  2122 C is larger in amount of cutting than the outer surfacing layer  2121 C. Thus, as in the first exemplary embodiment described above, the inner surfacing layer  2122 C is provided such that a thickness d is thinner than a thickness e of the outer surfacing layer  2121 C. Specifically, the thickness d of the inner surfacing layer  2122 C is set to approximately 40 μm, and the thickness e of the outer surfacing layer  2121 C is set to approximately 350 μm. 
     Effects of Fourth Exemplary Embodiment 
     According to the fourth exemplary embodiment described above, the following advantageous effects can be produced. 
     In the present exemplary embodiment, the step is provided between the outer surface  214 C of the outer surfacing layer  2121 C and the inner surface  215 C of the inner surfacing layer  2122 C. This makes it possible to increase a space inside a watch. Accordingly, a degree of freedom of design of a movement or the like housed in the space inside the watch can be increased. 
     MODIFICATION EXAMPLE 
     Note that the present disclosure is not limited to each of the exemplary embodiments described above, and variations, modifications, and the like within the scope in which the object of the present disclosure can be achieved are included in the present disclosure. 
     In each the exemplary embodiment described above, the watch outer packaging component of the present disclosure is configured as the case main body  21 ,  21 A,  21 B, or  21 C, but is not limited thereto. For example, the watch outer packaging component of the present disclosure may be configured as at least one of a case back and a bezel. Additionally, the watch may have a plurality of the outer packaging components as described above. Furthermore, the watch outer packaging component of the present disclosure may be a case in which a case main body and a case back are integral. 
     In the first, second, and fourth exemplary embodiments, each of the case main bodies  21 ,  21 A, and  21 C engages with the bezel  23 , the crown  26 , and the case back  22  via the winding stem pipe  25 , the plastic packing  27 , and the case back packing  40 . Furthermore, in the third exemplary embodiment, the case main body  21 B engages with the sensor  6 B via the packing  7 B, but the present disclosure is not limited thereto. For example, the watch outer packaging component of the present disclosure may engage with at least one of a case back, a crown, a button, a sensor, a dial window, and a bezel. 
     In the first, second and fourth exemplary embodiments described above, the sealing member of the present disclosure is configured as the winding stem pipe  25 , the plastic packing  27 , and the case back packing  40 , and in the third exemplary embodiment, the sealing member of the present disclosure is configured as the packing  7 B, but the present disclosure is not limited thereto. For example, the sealing member may be configured as the plastic packing  28  that secures the bezel  23  and the glass plate  24 , a gasket, or the like, and it is sufficient that the sealing member is configured to abut on the watch outer packaging component and to be capable of partitioning the space inside the watch and the space outside the watch. 
     In each the exemplary embodiment described above, the case main body  21 ,  21 A,  21 B, or  21 C, is configured as the watch outer packaging component, but is not limited thereto. For example, the case main body may be configured as an outer packaging component of an electronic device other than a watch, that is, a housing of an electronic device, or the like. By providing the housing configured in this manner, desired antimagnetic performance can be secured while a predetermined size is maintained, for the electronic device. 
     Summary of Present Disclosure 
     A watch outer packaging component of the present disclosure is a watch outer packaging component formed of austenitized ferritic stainless steel including a base formed of a ferrite phase, and a surfacing layer formed of an austenitized phase in which the ferrite phase is austenitized, and abutting on a sealing member that partitions a space inside a watch and a space outside the watch, wherein the surfacing layer has an outer surfacing layer provided on an outer surface facing the space outside the watch, and an inner surfacing layer provided on an inner surface facing the space inside the watch, and the inner surfacing layer is thinner in thickness than the outer surfacing layer. 
     Accordingly, the thickness of the inner surfacing layer is reduced, and thus, the outer surfacing layer can be made to have a thickness with which predetermined anticorrosive performance is obtained without increasing a thickness as the watch outer packaging component, and the base can be made to have a thickness with which predetermined antimagnetic performance is obtained. Thus, while maintaining a predetermined size as the watch, desired antimagnetic performance can be ensured. 
     Furthermore, in the present exemplary embodiment, the thickness of the inner surfacing layer is decreased, thus, for example, a distance between a movement housed in the watch outer packaging component, and the base formed of the ferrite phase can be shortened. Accordingly, influence of an external magnetic field on a motor or the like provided in the movement can be reduced, and the antimagnetic performance can be improved. 
     In the watch outer packaging component of the present disclosure, the thickness of the inner surfacing layer may be equal to or less than 100 μm. 
     Accordingly, for example, the distance between the movement housed in the outer packaging component, and the base formed of the ferrite phase can be shortened, thereby improving the antimagnetic performance. 
     A watch outer packaging component of the present disclosure is a watch outer packaging component formed of austenitized ferritic stainless steel including a base formed of a ferrite phase, and a surfacing layer formed of an austenitized phase in which the ferrite phase is austenitized, and abutting on a sealing member that partitions a space inside a watch and a space outside the watch, wherein the surfacing layer has an outer surfacing layer provided on an outer surface facing the space outside the watch, and the surfacing layer is not provided on an inner surface facing the space inside the watch. 
     Thus, the outer surfacing layer can be made to have a thickness with which predetermined anticorrosive performance is obtained without increasing a thickness as the watch outer packaging component, and the base can be made to have a thickness with which predetermined antimagnetic performance is obtained. 
     Thus, while maintaining a predetermined size as the watch, desired antimagnetic performance can be ensured. 
     In the watch outer packaging component of the present disclosure, a thickness of the outer surfacing layer may be equal to or greater than 100 μm and equal to or less than 600 μm. 
     Accordingly, the predetermined anticorrosive performance can be ensured, and it is possible to prevent a nitrogen absorption treatment time from becoming too long. 
     The watch outer packaging component of the present disclosure may be provided with a mixed layer that is formed between the base and the surfacing layer, and in which the ferrite phase and the austenitized phase are mixed with each other. 
     Accordingly, in nitrogen absorption treatment, a variation in transfer rate of nitrogen can be tolerated, thereby making it possible to facilitate the nitrogen absorption treatment. 
     In the watch outer packaging component of the present disclosure, the base may contain, in percent by mass, Cr: 18 to 22%, Mo: 1.3 to 2.8%, Nb: 0.05 to 0.50%, Cu: 0.1 to 0.8%, Ni: less than 0.5%, Mn: less than 0.8%, Si: less than 0.5%, P: less than 0.10%, S: less than 0.05%, N: less than 0.05%, and C: less than 0.05%, with a balance being formed of Fe and unavoidable impurities. 
     This makes it possible to increase the transfer rate of nitrogen to the ferrite phase, and a diffusion rate of nitrogen in the ferrite phase, in the nitrogen absorption treatment. 
     In the watch outer packaging component of the present disclosure, a nitrogen content of the surfacing layer may be 1.0 to 1.6% in percent by mass. 
     Accordingly, anticorrosive performance in the surfacing layer can be improved. 
     The watch outer packaging component of the present disclosure may engage with at least one of a case back, a crown, a button, a sensor, a dial window, and a bezel, via the sealing member. 
     A watch outer packaging component of the present disclosure is a watch outer packaging component formed of austenitized ferritic stainless steel including a base formed of a ferrite phase, and a surfacing layer formed of an austenitized phase in which the ferrite phase is austenitized, wherein the surfacing layer has a first surfacing layer provided on an inner surface facing a space inside a watch, and a second surfacing layer provided on an outer surface facing a space outside the watch, and the first surfacing layer is thinner in thickness than the second surfacing layer. 
     In the watch outer packaging component of the present disclosure, the thickness of the first surfacing layer may be equal to or less than 100 μm. 
     Accordingly, for example, a distance between a movement housed in the watch outer packaging component, and the base formed of the ferrite phase can be shortened, thereby improving antimagnetic performance. 
     In the watch outer packaging component of the present disclosure, the thickness of the second surfacing layer may be equal to or greater than 100 μm and equal to or less than 600 μm. 
     Accordingly, predetermined anticorrosive performance can be ensured, and it is possible to prevent a nitrogen absorption treatment time from becoming too long. 
     A watch that includes the watch outer packaging component of the present disclosure. 
     A method for manufacturing a watch outer packaging component of the present disclosure is a method for manufacturing a watch outer packaging component formed of austenitized ferritic stainless steel including a base formed of a ferrite phase, and a surfacing layer formed of an austenitized phase in which the ferrite phase is austenitized, and abutting on a sealing member that partitions a space inside the watch and a space outside the watch, that includes a first processing step of processing ferritic stainless steel to form a base material, a heat treatment step of performing nitrogen absorption treatment on the base material to form the surfacing layer, and a second processing step for cutting the surfacing layer to form the watch outer packaging component, wherein in the second processing step, an inner surfacing layer of the surfacing layer provided on an inner surface facing a space inside the watch is cut so as to be thinner in thickness than an outer surfacing layer provided on an outer surface facing a space outside the watch.