Seamless can body and method of manufacturing seamless can body

Abstract

[object] To provide a seamless can body in which the sheet thickness of a raw sheet (blank) is reduced, pressure resistance of a can bottom is enhanced, buckling is restrained, and problems with blacking and cleaning are solved, and a manufacturing method of the seamless can body.[Solving Means] A seamless can body 1 having a tubular body section 10 and a can bottom section 20. The can bottom section 20 includes an outer circumferential bottom section 202a extending from a lower end of the tubular body section 10 such as to decrease in diameter toward the inside and an annular grounding section 202E positioned further inside than the outer circumferential bottom section 202a. In a case where t1 is the sheet thickness of the outer circumferential bottom section 202a and where t2 is the sheet thickness of the annular grounding section 202b, the relation of t2>t1 is satisfied.

1 . A seamless can body including a tubular body section and a can bottom section,
 the can bottom section including
 an outer circumferential bottom section extending from a lower end of the tubular body section such as to decrease in diameter toward an inside, and 
 an annular grounding section located further inside than the outer circumferential bottom section, 
   wherein, in a case where t 1  is a sheet thickness of the outer circumferential bottom section and where t 2  is a sheet thickness of the annular grounding section, the following relation is satisfied
   t2>t1. 
   
     
     
         2 . A seamless can body comprising:
 a tubular body section; and   a can bottom section including at least an outer circumferential bottom section extending from a lower end of the tubular body section through a boundary part such as to decrease in diameter toward an inside,   wherein a sheet thickness of the lower end of the tubular body section is substantially equal to a sheet thickness of an intermediate part of the tubular body section in an axial direction.   
     
     
         3 . The seamless can body according to  claim 1 ,
 wherein the can bottom section further includes an inside end section located further inside than the annular grounding section, and   in a case where t 3  is a sheet thickness of the inside end section, the following relation is satisfied
   t3>t1. 
   
     
     
         4 . The seamless can body according to  claim 3 , wherein a sheet thickness gradually increases from the outer circumferential bottom section to the inside end section such that t 3 >t 2  is satisfied. 
     
     
         5 . The seamless can body according to  claim 1 ,
 wherein the can bottom section further includes a rising section rising upward from the inside end section, and   in a case where t 4  is a sheet thickness of an upper end of the rising section, the following relation is satisfied   
       t 4 >t 1 . 
     
     
         6 . The seamless can body according to  claim 5 , wherein the can bottom section further includes a dome section that is connected to the rising section and bulges to protrude upward, and a sheet thickness gradually increases from the dome section to the inside end section such that t 3 >t 4 >t 5  is satisfied in a case where t 5  is a sheet thickness of a center of the dome section. 
     
     
         7 . The seamless can body according to  claim 6 , wherein t 5 <t 1  is further satisfied. 
     
     
         8 . The seamless can body according to  claim 5 , wherein a ring groove in which a connection section between the rising section and the dome section protrudes toward an outside with respect to a can body axis is formed. 
     
     
         9 . The seamless can body according to  claim 2 , wherein a sheet thickness of the boundary part is substantially equal to the sheet thickness of the intermediate part. 
     
     
         10 . The seamless can body according to  claim 2 ,
 wherein, in a case where t WL  is the sheet thickness of the lower end of the tubular body section and where t WC  is the sheet thickness of the intermediate part of the tubular body section in the axial direction, the following relation is satisfied
     t   WC   ≤t   WL <1.09 ×t   WC . 
   
     
     
         11 . The seamless can body according to  claim 10 ,
 wherein the following relation (where t 0  is the sheet thickness of the boundary part) is satisfied in the tubular body section
     t   WC   ≤t 0<1.09 ×t   WC    
   
     
     
         12 . The seamless can body according to  claim 1 , wherein 60 degrees specular glossiness from the lower end of the tubular body section to the vicinity of the boundary part is equal to or more than 300%. 
     
     
         13 . A method of manufacturing a seamless can body including a tubular body section and a can bottom section, the method comprising:
 a first molding step of molding a raw metal material into a cup body including the tubular body section, a cup outer circumferential bottom section extending from a lower end of the tubular body section such as to decrease in diameter, an inclined section extending upward toward an inside from the cup outer circumferential bottom section, and a cup dome section bulging upward from an end portion of the inclined section at a first height; and   a second molding step of applying a pressing force to the cup dome section toward an outside of a can by using an upper molding member while the cup outer circumferential bottom section of the cup body is brought into contact with a lower molding member, to press down the cup dome section such as to have a second height lower than the first height, and to apply compressive stresses in a meridian direction and a circumferential direction, and then pressing the inclined section into the lower molding member while a thickness of the inclined section is increased.   
     
     
         14 . The method of manufacturing a seamless can body according to  claim 13 ,
 wherein, in the second molding step,
 the inclined section is pressed into the lower molding member, to thereby form an annular grounding section located further inside than an outer circumferential bottom section, an inside end section located further inside than the annular grounding section, and a rising section rising upward from the inside end section and connected to a can dome section, and 
 a ring groove in which a connection section between the rising section and the can dome section protrudes toward an outside with respect to a can body axis is formed such that an inside diameter of the connection section becomes greater than an inside diameter of the inside end section. 
   
     
     
         15 . A method of manufacturing a seamless can body, the method comprising:
 a first molding step of molding a raw metal material into a cup body including a tubular body section thinned by ironing, an outer circumferential bottom section extending from a lower end of the tubular body section, and a bulging section bulging from the outer circumferential bottom section toward an opening at a first height; and   a second molding step of pressing down the bulging section such as to have a second height lower than the first height,   wherein, in the first molding step, the lower end of the tubular body section is drawn to form the outer circumferential bottom section extending from the lower end of the tubular body section through a boundary part such as to decrease in diameter toward an inside, such that a sheet thickness of the lower end of the tubular body section becomes substantially equal to a sheet thickness of an intermediate part of the tubular body section in an axial direction.